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A proven treatment for patients suffering from musculoskeletal issues is orthopaedic surgery. Metal-on-metal devices have been popular over the last 50 years due to low wear rates and excellent corrosion resistance. However, due to recent findings of metal dissolution into the body, their subsequent use has been in decline and are barely used today. This leads to adverse effects within the patient as well as weakening the structural integrity of the alloy. Understanding the mechanisms behind this phenomenon are vital to improving the functionality of these implants as due to their low wear rates they are viable for the ever-growing younger population who require an implant. A thorough investigation into the electrochemical behaviour of cobaltchromium-molybdenum alloys in simulated bodily fluids has been undertaken, looking in detail at the specific interactions that bovine serum albumin has with the alloy. A range of electrochemical and surface characterisation techniques were adopted to undertake this research. Analysis of the electrolyte post-test was also conducted to determine the dissolution of the alloy under specific conditions. Obtained results have indicated that the presence of inorganic/organic species affects the corrosion resistance and dissolution of the metal. The presence of bovine serum albumin has been shown to be two-fold: it can inhibit the access of oxidants to the alloy leading the adsorbed organic layer/passive film to be weaker, increasing the corrosion rate but can alter the passive film due to the molecule being a cathodic inhibitor increasing the resistance of corrosion in the passive domain. During an electrochemical repassivation phase, the presence of bovine serum albumin is seen to inhibit the repassivation rate alongside altering the composition of the reformed passive film and ratios of metallic ions released into the environment. The affinity of bovine serum albumin with molybdenum has been identified to be due to the formation of a highly thermodynamically favoured Mo-S bond. From the findings presented, a clearer understanding of the electrochemical interactions that take place within the body have been obtained. This is crucial for further understanding and predicting in-vivo performance.

In the UK, there is 140 tHM of PuO2 stored at the Sellafield site as a zero value asset. This material was generated by nuclear fuel reprocessing in the ThORP and Magnox fuel reprocessing plants, which are due to cease operation by 2021. The current UK government plan is to recycle this material as MOX fuel, however the uptake for this fuel type in the current UK reactor fleet is absent. There is also a significant portion of this waste stream that is contaminated with advanced fission products (e.g. Am-241) and degraded storage materials (e.g. Cl from PVC containment). Therefore, a dual track strategy of immobilisation and MOX fuel research has been suggested for this waste stream, to ensure there is a suitable end state for the stockpile should MOX fuel fabrication not come to fruition. This thesis presents an investigation of candidate wasteforms which are appropriate for the immobilisation of the UK PuO2 stockpile, where HIPing was applied as a thermal treatment technology and CeO2 used as a surrogate for PuO2 throughout. The key research questions for this thesis were: 1. What are the candidate wasteforms for the immobilisation the UK PuO2 stockpile given that ~ 5 tHM is degraded/contaminated and MOX fuel is not currently feasible? 2. How do these wasteforms compare in terms of waste loading, technology readiness level and chemical durability? 3. Is hot isostatic pressing a viable thermal treatment method for these wasteforms? 4. Is CeO2 a suitable surrogate for PuO2 in each wasteform? The wasteforms investigated for this thesis were ATS glass and fluorite based ceramics (zirconolite, pyrochlore and cubic zirconia). The results of the studies conducted for each wasteform matrix are presented below. Chapters 4 and 5 - Alkali tin silicate (ATS) glass: ATS glass is a type of borosilicate glass developed in the US for the immobilisation of excess weapons plutonium. This composition was modified to include Fe0 to create a reducing environment within the glass, with the aim of reducing Ce4+ to Ce3+ , and therefore improving the Ce wasteloading. The matrix of ATS glasses produced were characterised using Ce XANES and Fe EXAFS/Mössbauer spectroscopy to determine the Ce/Fe oxidation state and Fe local coordination environment. Ce was shown to fully reduce to Ce3+ and incorporate into the glass upon the addition of Fe0 . Durability tests were completed on the most successful compositions, showing that the addition of Fe improved the short term durability of the glass. HIPing was also shown to be a viable thermal treatment method for ATS glass, producing glass which fully incorporated Ce, with no deleterious effects on the dissolution rate measured. Chapter 6 - Zirconolite ceramics: Zirconolite ceramics are a proposed wasteform for the immobilisation of PuO2. A matrix of eight zirconolite formulations was produced using HIPing, assessing two different Ce doping mechanisms, as well as the efficacy of Al, Mg and Fe as charge compensating ions. Secondary phases, including perovskite and trace CeO2, were observed using XRD and SEM/EDX. A selection of the formulations with the most favourable phase assemblage were subject to durability assessment using aggressive conditions (0.01 M HNO3 leachant at 90 °C), in order to compare their relative durability as well as comparing their performance to other wasteforms proposed for this waste stream. The secondary Ce-bearing phases were postulated to dominate the dissolution rate measured, with the formulation containing the highest quantity of secondary phases displaying the highest dissolution rate. The Ce dissolution rates were still comparable to others in the literature measured in similar conditions, providing confidence in the long term durability of zirconolite wasteforms despite the heterogeneity in the phase assemblage. Chapter 7 - Fluorite based ceramics: Ceramic formulations with a fluorite based structure were investigated which included: cubic zirconia, zirconate pyrochlore, and zirconolite. The waste loading of these formulations was previously optimised using CPS, however significant porosity was observed, hence the application of HIPing in this work to achieve full densification. These formulations included Hf and Gd as neutron absorbing cations, included to observe the effect of these cations on the resulting phase assemblage and relative dissolution rate. Single phase zirconolite was synthesised (with two polytypes observed, 2M and 3T), which proved to be the most durable composition when subject to aggressive PCT-B testing (identical to dissolution conditions implemented in Chapter 6). The least durable formulation was pyrochlore due to the presence of a Ce/Gd fluorite solid solution which was postulated to preferentially dissolve. With the exception of the pyrochlore formulation, the measured dissolution rates of Ce and Gd were within one order of magnitude which is promising for maintaining subcriticality in these wasteforms. Chapter 8 – Molten salt synthesis of zirconolite ceramics: The molten salt synthesis of zirconolite ceramics was also investigated, for the purposes of selectively immobilising entrained actinides from the legacy and future pyroprocessing of nuclear fuels, using the salt eutectic as a synthesis medium. A self-compensating Ce-doped zirconolite formulation was selected, with several experimental parameters systematically adjusted to observe the effects on the resultant phase assemblage. These experimental parameters included: salt to ceramic ratio, synthesis temperature, duration and atmosphere, as well as reagent excess and surrogate type. An excess of TiO2 and ZrO2 reagents was found to produce a wasteform close to single phase, however deleterious Ce-bearing perovskite was still formed. HIPing was not applied in this case since the salt medium must be dissolved post-synthesis, and a second consolidation step for the resulting zirconolite powder must be performed. In summary, each wasteform investigated was demonstrated to be feasible for the immobilisation of the UK PuO2 stockpile, when using Ce as a Pu surrogate. Ce was successfully incorporated into the chemical structure of each wasteform studied, with further optimisation of the synthesis parameters required for complete waste incorporation in some instances. The durability of the ceramic wasteforms was several orders of magnitude greater than the ATS glass wasteforms, when considering the NLCe and NRCe. However, it is important to note that the technology readiness level of glass wasteform synthesis in the UK is significantly greater than that of ceramic wasteforms. CeO2 was demonstrated to be a viable surrogate for PuO2 but it should be noted that Pu4+ has a much greater redox potential that Ce4+, which proved to be problematic for both the glass and ceramic wasteforms studied in this thesis. HIPing was also demonstrated to produce viable wasteforms in Chapters 5 – 7, however the effects of this process on the redox environment requires further consideration.

Methane is an abundant earth resource important for the energy sector. The development of better catalysts for the complete combustion of methane and the discovery of new catalysts that can directly oxidise methane to methanol are of great scientific importance. The total oxidation of methane to CO2 is considered for amorphous surface palladium oxide. A partially oxidised palladium surface is found to have both metal-like and oxide-like character. This peculiar characteristic is found to be important for increased reactivity, with dehydrogenation steps having enhanced activity on metal areas and oxidation steps having enhanced activity on oxide areas of the surface. These findings allow the further development of catalysts that stabilise the metal and oxide phase together, improving catalyst efficiency. The mechanism for the direct oxidation of methane to methanol is investigated for a Rh@ZSM-5 catalyst. The effect of molecules coordinating to the single atom centre on the reaction mechanism is explored. CO has a considerable effect as a ligand, explaining the experimental requirement for CO to have a trace presence in the system. Despite water also being required experimentally, a minimal ligand effect is found. However, water is found to be crucial as a hydrogen source for a key elementary step in the reaction. The similarity of the chemistry of single atom heterogeneous systems and homogeneous systems is discussed. These findings show the possibility of modulating ligand effects in heterogeneous catalysts. The increased reactivity of methanol against methane is investigated for a variety of fcc metals. It is found that methanol as a reactant is consistently more reactive for C-H activation, C-O coupling, and C-OH coupling. As methane and methanol have different affinities for water, the effect of an aqueous environment on the conversion-selectivity limit is considered. Water is found to not have an asymmetric effect on the reactivity of methane and methanol, mirroring the findings of the gas phase calculations. However, a C-OH mechanism is promoted in the aqueous phase, which would have a considerable effect on the selectivity on the production of methanol from methane, by minimising the formation of other oxygenates. This explains a long held mystery of why water promotes the selectivity of the methane to methanol process across many systems. The failure of palladium, a total oxidation catalyst, for the methane to methanol process is characterised and explained with a total combustion microkinetic model. A streamlined microkinetic model is designed that can accurately describe the methane to methanol formation. Excess dehydrogenation of methane is the main route of selectivity loss. Single atom alloys are then considered as a potential opportunity for a selective methane to methanol catalyst class. 64 surfaces are considered as potential catalysts, with 7 found to be indicative of being effective methane to methanol catalysts. These are then modelled for their activity and selectivity towards methanol production. One modelled catalyst has remarkably improved selectivity and activity over palladium, allowing future experimental trials which are focused on the best and most promising catalysts.

Ammonia has recently been regarded as a promising energy vector for on-board hydrogen generation purposes thanks to the breakthrough in renewable powers. The intermittent nature of these energies mean that both the generation and utilisation of ammonia need to be carried out at mild temperatures and pressures to afford frequent ramping. Under such conditions, catalysts are easily prone to hydrogen poisoning where the surface active sites are extensively blocked by H atoms originated from the competitive reaction between dihydrogen and other gaseous reactants. In such context, this thesis explores the use of a metal-doped electrostatically polar refractory oxide catalyst for efficient thermal catalytic ammonia synthesis and decomposition reactions with the primary aim to alleviate hydrogen poisoning. In-depth catalytic activity and kinetic order studies were examined for both the forward and backward N-cycle reaction. A thorough round of surface characterisations combined with a series of spectroscopic, imaging and computational techniques were conducted to investigate the relationship between the activity and the structural and electronic properties of the catalyst. In the second part of the thesis, the polar oxide catalyst was aptly modified to construct a well-defined frustrated Lewis pair to decipher the elemental pathway for which H atoms are transferred from the metal active site to the catalytic support. Atom probe tomography in conjunction with in-situ x-ray photoelectron spectroscopy were employed to reconstruct the 3D environment of the spillover effect and the surface changes were monitored in real-time.

Carbon dioxide utilisation in the synthesis of dimethyl carbonate (DMC) is attractive due to the extensive application of DMC in a variety of processes. Previously, high selectivity to DMC has been correlate with high pressure operating environments employing supercritical CO2. Applying high-operating pressure (8 Mpa~16.5 MPa) in chemical plants is, however, cost and energy intensive and introduces significant safety concerns. Optimisation of reaction conditions with the aim of minimizing the operating pressure while increasing reaction rate, selectivity and catalyst lifetime should be a key goal of process development. Herein, one-pot synthesis of DMC from propylene oxide, methanol and CO2 using alkali halide catalysts under low-operating pressure (2 MPa at room temperature) was studied. This study has evaluated the catalytic activity of alkali halide-based catalysts via the one-pot route of DMC synthesis and the results showed that a DMC selectivity of 15.9% can be obtained when K2CO3-NaBr-ZnO is used as the catalyst. However, selectivity to DMC is limited by the relatively high yield of PG through the hydrolysis of PO. Therefore, both a physical drying agent (3Å molecular sieve) and a chemical dehydrating agent (acetonitrile) are applied in DMC synthesis. The production of PC increases significantly (from 1.04 mmol/ml to 1.48 mmol/ml and 1.59 mmol/ml for 3Å molecular sieve and acetonitrile, respectively) owing to the inhabitation of the PO hydrolysis, however, the influence of adding dehydrating agents on improving the yield of DMC is not obvious (from 0.53 mmol/ml to 0.51 mmol/ml and 0.49 mmol/ml for 3Å molecular sieve and acetonitrile, respectively). The catalyst applied in the DMC synthesis reactions are characterised using TGA, XRD, SEM, SEM/EDS, AAS and ICP-OES. Additionally, Zn powder shows great possibility of achievement to remove water through the reaction with steam water under reaction condition. Results indicate that the addition of Zn powder to the K2CO3-NaBr-ZnO catalyst system increases the DMC selectivity from 15.9% to 36.1% at 2 MPa and 160 °C for 5 h. Catalyst characterisation showed that Zn powder increases the stability of the catalyst by preventing the active ingredients on the catalyst surface from leaching. The results also show an increase in propylene oxide conversion to DMC attributed to the increase of Zn2+ ions in the reaction solution. Zn both promotes DMC formation through the new reaction route and transesterification of propylene carbonate and methanol.

This PhD thesis describes the Ni-catalysed alkylation of ammonia with alcohols to achieve high selectivity to primary amines. This work was broadly divided into two parts: (i) developing and understanding reaction conditions through batch reactions; and (ii) deploying the system into a flow reactor and understanding how the system works and fails. Extensive screening of heterogeneous catalysts in the alkylation of ammonia with alcohols was carried out in batch reactors. It was found that a commercial 65 wt% Ni/Al2O3/SiO2 catalyst yielded the highest selectivity towards the primary amine. High selectivities of 99% with 7 different alcohols to their corresponding amines were achieved with moderate alcohol conversions, under the reaction conditions of 160 °C, 72 hours, 30 mL of 0.1 M alcohol in o-xylene, alcohol/Ni = 10 and anhydrous ammonia/alcohol = 7. An extruded version of this catalyst was created for the application in flow. A flow reactor was then designed and constructed. Competitive formation of the nitrile side-product was suppressed when the catalyst was pre-reduced. Higher alcohol conversions and selectivities to the primary amines were achieved at 51 - 100% and 99% respectively. This improvement in performances is attributed to the minimisation of water accumulation. Over an extended continuous run for 78 hours, it was found that the carbon deposition on the catalyst resulted in the deactivation of the catalyst in flow.

This thesis investigates the design and performance of absorbent-enhanced ammonia synthesis reactors. The per-pass conversion of ammonia can be improved by the sequencing of ammonia synthesis catalyst and ammonia-selective absorbent beds in the reactor. A new perspective includes adjacent coupling and multi-bed coupled absorptive reactors which contributes to the exciting area of ammonia synthesis improvement. This type of reactors enable operation under conditions milder than those used in a traditional Haber-Bosch reactor. As part of the work a novel Ru catalyst with polar metallic oxide support was developed to meet the requirements of mild operating conditions of the absorptive reactor. An experimental unit was built to perform the synthesis of ammonia in a fixed-bed absorptive reactor, and an increased per-pass conversion was observed from experimental data. Mathematical models were also developed to provide insights into the reasons for the conversion improvement in the absorptive reactor. Our simulations of these two kinds of absorption-enhanced ammonia synthesis reactors contribute to their understanding and confirm the enhancement of their per-pass conversion. A preliminary mathematical model study of the adjacent coupling absorptive reactor was carried out first in which the influence of absorption on the per-pass ammonia conversion was linked to a hypothetical recycle stream. Based on the result of this preliminary model, a more detailed transient backflow cell model was developed to simulate the behaviour of the adjacent coupling absorptive reactor. Given the complexity of the reacting fluid through the fixed bed, a computational fluid dynamics simulation via ANSYS Fluent was also generated and resulted in similar results to those of the transient backflow cell model. On this basis, an improved absorptive reactor, i.e. the multi-bed absorptive reactor, was proposed and modelled in Fluent, achieving close to 100% per-pass conversion. This research improved the per-pass conversion of ammonia synthesis reactors and enabled milder operating conditions for process. Furthermore, a theoretical framework was provided through mathematical modelling for optimisation purposes.

Declining indigenous resources, increased dependence on imports and intermittent renewable energy, have resulted in an increasingly diverse energy-generation landscape. As a result, gas turbine operators face new challenges with respect to gas turbine flexibility in terms of combustion efficiency, safety and emission control. Increased reliance on liquefied natural gas, potentially containing high concentrations of heavier hydrocarbons, typically ethane and propane, coupled with the emerging prospect of hydrogen injection into national gas grids, presents associated combustion impacts not fully appreciated. This new reality underlines the necessity of developing understanding of fundamental combustion characteristics, ultimately guiding the design of future highly flexible gas turbines. This thesis aims to characterise fundamental combustion performance of methane/higher hydrocarbon/hydrogen fuels, through a combination of experimental and numerical techniques, with a focus on natural gas blends representative of fuel variations and at air fuel ratios expected in premixed low-carbon power generation facilities. The parameters identified to investigate fuel behaviour were the laminar burning velocity, Markstein Length and the Lewis Number, yielding essential physiochemical and thermo-diffusive flame information. These properties are of value when attempting to predict flame behaviour in turbulent environments, reflective of most practical gas turbine applications. The main components of natural gas, and relevant hydrogen enriched binary and tertiary mixtures were parametrically investigated, with respect to stretch-related and flame propagation behaviour at lean air fuel ratios, in addition to a comparison of numerically simulated results obtained from chemical kinetics. Effective Lewis Number models were appraised and compared to experimentally measured data, employing theoretical formulations relating Markstein Length to Lewis Number as proposed in literature. The influence of hydrogen and propane addition to the lean stability limits of premixed turbulent methane flames was examined, using a generic swirl burner, at various inlet temperature and thermal powers, with measured lean blow off limits in correlation with measured Markstein length behaviour.

The objective of this work was to design, model and develop a practical and compact optical system capable to measure the displacement a microelectromechanical system (MEMS) gravimeter. Integrating the optical readout will enable to achieve a resolution potentially down to 10 μgal per square root Hertz. This will allow a more compact measurement system that could revolutionize the way gravity surveys are performed. The different optical components required to create the displacement sensor have been studied, fabricated and characterised. The sensor is obtained by creating an integrated Michelson interferometer on an SOI chip. Each component has been optimised for the specific application starting from the optical or electrical simulations. The design phase has considered both the requirements for obtaining a compact system and the fabrication limitations and tolerances. To successfully create the required structures, the fabrication process required the development of tailored methods for the electron beam lithography and the etching, together with the improvement of the existing ones. The fabricated system demonstrated a resolution below 4 nm when measuring a moving mirror at 30 cm distance. The waveguide coupled Ge photodetector required for the integration has been extensively studied. A novel design showed and increased coupling efficiency between the silicon waveguide and the germanium structure. The charge sheet layer has also been modelled to give a better electric field profile distribution. The selective area growth of the germanium in silica trenches has been investigated with the purpose of reducing the number of defects present in the Ge detectors. This will reduce the sources of dark current and dark counts. All these improvements will enable to have small device footprints with low dark current and capacitance. A detector with high sensitivity will allow to have a high sensitivity on the displacement of the MEMS and in turn on the gravity measurements.

Nitrocellulose (NC) is the base component for many modern day propellants and explosives, as well as for everyday items such as printing inks, paint and lacquer coatings. Despite its early beginnings as the first man-made plastic, the decomposition pathways from the bulk material to the products observed from its ambient ageing are still not fully understood. Knowledge of these processes are of critical importance when considering the conservation of NC artefacts, refinement of product formulations, predictions of shelf life and safety improvements. In this study, the dominant degradation pathways of NC were investigated using quantum mechanics (QM) methods to probe the mechanisms leading to the initial cleavage of nitrate groups from the cellulosic backbone. The NC structure was truncated from a polymer chain to monomer, dimer and trimer units. Density functional theory methods (DFT) were used to study the mechanistic detail at individual nitrate sites. Comparison of differently sized units using the quantum theory of atoms in molecules (QTAIM), analysis of the electrostatic potential (ESP) surface and partial charges showed that the most suitable approximation for study of the decomposition reactions was the β-glucopyranose monomer, bi-capped with methoxy groups. The primary thermolytic and hydrolytic denitration routes were explored using transition state (TS) searches and potential energy surface (PES) scans. It was found that the thermolytic behaviour of the NC denitration step matched that of a well studied nitrate ester, pentaerythritol tetranitrate (PETN). The hydrolytic scheme for nitrate cleavage was studied, finding that protonation at the bridging oxygen site was the most likely to lead to denitration. It was not possible to isolate a TS for the hydrolytic reaction, though a number of coordination schemes were tested. Key secondary processes beyond nitrate cleavage were examined to determine the fate of nitrogen in the system and the cause of the transition from a first order reaction rate to autocatalytic decomposition. The energies of reactions in three different decomposition schemes proposed in literature were compared. Ethyl nitrate was used as a test system before extension to the NC monomer. New reaction pathways for decomposition were constructed using the reactions posed in the literature studies. The new schemes revealed that •NO2 was the most likely cause for the experimentally observed autocatalytic rate of degradation.

Van der Waals heterostructures form a rapidly expanding field of study in physics, chemistry, material science and engineering alike. More and more exfoliable materials are discovered and the techniques to take them apart and build them back up are continuously refined. As stacking techniques become increasingly precise and reliable, potential applications of heterostructures in electronics and opto-electronics are unlocked. Within Van der Waals materials, black phosphorus has the valuable combination of a direct, tunable bandgap and a high charge carrier mobility, making it a good candidate for heterostructure devices. On its own however, black phosphorus suffers from degradation in ambient conditions and a much lower mobility than predicted. Blue phosphorus, a high-pressure allotrope, shows similar promise with further opportunities as precursor to phosphorus nanoribbons and nanotubes, but is predicted to suffer from the same problems. For the materials to be success in nanostructure applications, both these shortcomings will need to be addressed. In the following thesis, I set out to offer a well-rounded study of the properties and structure of black phosphorus in ambient conditions as well as a close examination of apparently inherent point defects at the atomic scale. The ambient degradation of black phosphorus was found to slow down significantly in a low-humidity environment, corroborating the theory that ambient degradation is a multi-step process involving oxygen and water. Chemical analysis of sample produced through both common synthesis pathways showed low concentrations of tin and iodine impurities. Atomic scale defects were studied both through STM and NC-AFM. The dominant defect has a characteristic double-lobed shape. DFT and Tight-binding calculations of tin substitutions are in good agreement with our STM and STS experiments, and find the double lobed shape to arise from a series of hydrogen-like states hosted in a potential well around the negatively charged tin defects. At high pressure, phase transitions between allotropes are found to be slow and exhibit a strong hysteresis, resulting in the coexistence of several phosphorus phases. A sufficient concentration of dopants may be able to stabilise blue phosphorus at ambient pressure.

Polycyclic aromatic hydrocarbons (PAHs), compounds that are produced during the combustion of fuels, is one example of contaminants found in automotive lubricants. PAHs can aggregate and form solid deposits. The deposits can be dispersed by the inclusion of oil-soluble additives into the lubricant. However, these additives can have negative effects on the lubricant performance. Unfortunately, current technologies do not remove contaminants; rather, they serve to minimise any damage caused by them. It is proposed that supplementing current technologies with suitable solid-phase, polymeric additives may be of benefit. It is hypothesised that contaminants can be removed from hydrocarbon fluids using polymer-supported chemistries in the solid-phase. Precipitation polymerisation (PP) and non-aqueous dispersion (NAD) polymerisation were investigated to synthesise a library of aromatic-based, crosslinked polymer particles. Hypercrosslinking chemistry was also utilised to impart high specific surface areas into some materials. To test the applicability of removing PAHs from a hydrocarbon fluid, each polymer was contacted with a solution of PAHs in heptane. These investigations proved fruitful, showing that upwards of 90% of certain PAHs could be removed from a heptane solution using crosslinked polymers. The synthesis of polymer resins by suspension polymerisation was investigated, with an aim of producing polymer particles that were of an appropriate size for containment within an engine lubricant system. A library of resins was successfully designed, synthesised and characterised. Gel-type, macroreticular and hypercrosslinked materials were synthesised to give a breadth of specific surface areas bearing varied functionality. Finally, contamination removal from an engine lubricant in situ, using some of the synthesised materials, was undertaken. It was concluded that using solid phase-polymers as contaminant removal devices was effective. Some of the work presented in this thesis forms the basis for the patent application W02017178593A2 (Removal of aromatic compounds from a hydrocarbon fluid).

Increasing greenhouse gas emissions since the onset of industrialisation now pose a significant threat to modern society and the habitability our planet for future generations. It has been determined that we must achieve zero net emissions by 2050 with a 45% decrease in emissions by 2030 (relative to 2010 levels) in order to limit warming to 1.5 °C by the end of the century. A wide variety of solutions are being explored to limit the impact of modern emissions and transition to a more sustainable energy infrastructure. One such example is the capture, storage and conversion of CO2 into valuable products and fuels for emissions mitigation and energy storage. Iron nanoparticles supported on carbon nanotubes known as Fe@CNT have proven themselves to be active for the catalytic hydrogenation of CO2 into hydrocarbons. This is due to their ability to catalyse both the reverse water-gas shift and Fischer-Tropsch processes, resulting in a coupled process that generates chemical fuels directly from a feed gas of hydrogen and CO2. Furthermore, the integration of the iron particles into the carbon nanotube support structure during synthesis results in a nanotube-particle bridged structure that enhances catalyst activity due to improved hydrogen spillover. However, the distribution of the resulting products is notoriously difficult to control, often requiring the addition of promoter metals to enhance catalyst activity and selectivity towards desirable products. These promoters are typically doped onto the surface of the catalyst using a wet impregnation technique, and are said to enhance reactivity by increasing the catalyst’s Lewis basicity. Herein, however, an alternative method of increasing the basicity of the catalyst is explored by doping nitrogen heteroatoms directly carbon nanotube support structure during synthesis resulting in a novel catalyst referred to as Fe@NCNT. This thesis explores the synthesis, characterisation and reactivity of Fe@NCNT to determine the potential for nitrogen doping to enhance the activity of carbon-supported iron nanoparticles in CO2 hydrogenation. The influence of reaction conditions and the addition of synergistic promoter metals are also explored. Nitrogen doping in Fe@NCNT serves to enhance the basicity of the catalyst, resulting in notably increased CO2 conversion and decreased CO selectivity relative to nitrogen-free Fe@CNT. However, methane production also increases as a consequence of nitrogen doping, and a trade-off is observed between CO2 conversion and high α values in the FT product distribution. This unexpected observation is largely attributed to the influence of local C—N dipoles in the catalyst surface upon the adsorption properties of the dipole-containing CO2 and CO reactant molecules and the significantly less polar hydrocarbon products. This behaviour is subsequently exploited further to develop a primarily iron-based, FT-driven methanation catalyst using a significantly lower ruthenium loading than similar catalysts in literature.

The electronic structure and magnetisation of NiFeCoCr and NiFeCoCrPd high entropy alloys has been investigated. Using Ab-initio methods the momentum density of magnetic electrons and the magnetic structure of these alloys were determined. For this, special quasirandom structures and the coherent potential approximation were used for modelling the chemical disorder present in high entropy alloys. Also, magnetic Compton scattering experiments were done to validate the theoretical calculations. The spin magnetic moment of NiFeCoCr and NiFeCoCrPd high entropy alloys have been measured by magnetic Compton scattering. Both theoretical methods overestimated the spin magnetic moment as was expected in transition metals alloys for the local density approximation and generalised gradient approximation level of density functional theory. The magnetic structure in these alloys shown most of the spin magnetic moments of Cr aligned in a opposite direction to the magnetic moments of the other elements. Previous works reports clustering or short range order of Cr in NiFeCoCr high entropy alloy. Analysing its magnetic Compton profiles this possible clustering has been discarded. Then, a ferrimagnetic structure in the strict sense is not possible in this compound. Furthermore, the addition of Pd to NiFeCoCr high entropy alloy increased the spin magnetic moment of the resultant equiatomic alloy. The spin magnetic moment of NiFeCoCrPd high entropy alloy obtained by the special quasirandom structure method is close to the experimental value measured by magnetic Compton scattering.

The Li-N-H system (lithium compounds with nitrogen and/or hydrogen based anions) is a promising family of materials for chemical energy storage applications; the development of efficient energy storage materials is one of the key challenges for global renewable energy utilisation. The Li-N-H system is of importance for both hydrogen storage and in facilitating the storage of energy as ammonia. Lithium hydride and lithium imide, two materials in this family, were investigated in this thesis. The interactions of ammonia on the surface of lithium hydride represent the hydrogen formation step in the lithium amide-lithium hydride hydrogen storage system. The study of these interactions through DFT and MD simulations has led to new insights from geometric considerations of ammonia into both its movement across the surface and its stable configuration. Molecules on the lithium hydride surface with tetrahedral geometries closely related to ammonia were investigated to better understand the surface interactions due to the distorted tetrahedral structure of ammonia. This lithium hydride surface study is the foundation for future investigations of ammonia on more complex Li-N-H surfaces, namely lithium imide, which is the dehydrogenated form of the hydrogen store, and itself an active catalyst for ammonia decomposition. The structure and dynamics of bulk lithium imide were investigated between 300-700 K with a particular attention to lithium-ion mobility through the structure. The evolution of the structure was observed from ensemble average nitrogen environments of the hydrogen and lithium ions. On heating to 700 K, a monoclinic to cubic phase transition (I112/b →Fm3̄m) was observed with the structural transition around 500 K. Frenkel defect formations with lithium ions displaced from tetrahedra into octahedra were traced through the structure and two different defect arrangements were obtained at low-temperature using different temperature gradients.

Renewable energy, such as biofuel has been highlighted as a future fuel that could replace fossil fuels. The conflict between biofuel and food security has encouraged the research on the conversion of lignocellulosic biomass into biofuels. Although lignocellulosic biomass is abundant, the presence of lignin and the cost of enzymes have caused several major issues in regards to the commercialization of lignocellulosic biofuels. The aim of this study was to investigate the feasibility of using wheat straw and sorghum bran to produce value added products, such as enzymes and bioethanol. The utilization of wheat straw for cellulase production and the subsequent hydrolysis was investigated. Six fungal strains (Aspergillus niger N402, Aspergillus niger N403, Aspergillus niger CKB, Trichoderma reesei R32, Trichoderma reesei R33 or Rhizomucor variabilis RS) were investigated using both solid-state fermentation (SSF) and submerged fermentation (SmF). In SSF, cellulase production increased from 3.2±0.05 FPU/g to 8.1±0.3 FPU/g (Filter Paper Unit) when wheat straw was modified using alkali treatment. The addition of starch improved the cellulase production with a cellulase activity of 23.14±0.09 FPU/g being obtained when 0.04% starch was added. The inoculum and reactor size also affected cellulase production. A. niger N402 with an inoculation ratio of 1x107 spores/g resulted in the highest cellulase activity of 55.93 FPU/g and 30.43 FPU/g in SSF using Petri Dish and 250 mL shake flask, respectively. The optimisation of cellulase production using a newly isolated fungal strain, R. variabilis (RS) was performed in both submerged fermentation (SmF) and solid-state fermentation (SSF). The impact of various parameters, including pH, mineral addition, nitrogen source, temperature, and substrate concentration, was investigated for SmF and incubation time, pH, temperature, inoculation size, moisture content, and nitrogen source were investigated for SSF. An optimum fermentation condition was determined to be: pH 6.5, 0.03% tryptone and fermentation for 3 days for SmF, a cellulase activity of 18.44 FPU/g was obtained. Similarly, an optimum fermentation condition for SSF was determined to be: pH 7, 28°C, inoculation size of 1×107 spores per g substrate, 0.03% tryptone and fermentation for 5 days. The cellulase activity was 30.19 FPU/g. Response Surface Methodology (RSM) was used to further optimize cellulase activity in SmF and SSF. This approach resulted in cellulase activity of 23.81 FPU/g for SmF and 24.80 FPU/g for SSF. Two rounds of physical mutagenesis of RS strain were carried out using UV lights and microwave heat. A mutant strain MW15-03 was obtained, which showed 21.6% higher cellulase production capacity in comparison with the parent strain. Sorghum bran, a starch rich food processing waste, was investigated for the production of glucoamylase in SmF and SSF. The fermentation parameters, such as cultivation time, substrate concentration, pH, aeration rate, inoculation ratio, temperature, nitrogen source, and mineral addition were investigated for SmF. The glucoamylase activity was improved from 1.90 U/mL in an initial test to 19.26 U/mL at 10% substrate concentration, pH 6, fermentation volume 200 mL in 500 mL shaking flask and fermentation of 3 days. RSM was used to further optimize glucoamylase activity in SmF and glucoamylase activity of 59.03 U/mL was achieved at the following conditions: substrate concentration 8%, pH 6, yeast extract concentration 5 g/L and fermentation volume 100 mL in 250 mL shaking flasks. Larger scale production of glucoamylase enzyme in 2 L bioreactors under the optimum condition resulted in 21.67 U/mL of glucoamylase activity at 72 hours of fermentation, while further increasing sorghum bran concentration to 12.5% gave an improved glucoamylase activity of 37.55 U/mL at 115 hours of the fermentation. The crude glucoamylase solution was used for the enzymatic hydrolysis of the sorghum bran. A sorghum bran hydrolysis carried out at 200 rpm, 55°C for 48 hours at a substrate loading ratio of 80 g/L resulted in 11.74 g/L glucose, which was comparable to that obtained using a commercial enzyme (12.72 g/L). Larger scale sorghum bran hydrolysis in 2 L bioreactors with crude glucoamylase enzyme resulted in a glucose concentration of 38.7 g/L from 200 g/L sorghum bran. Wheat straw hydrolysate, sorghum processing wastewater and sorghum bran hydrolysate were used as substrates for the production of bioethanol. The addition of minerals accelerated the rate of yeast fermentation. Marine yeast strain W. anomalus M15 resulted in a very high ethanol yield of 49.79%. Upto 19.3 g/L bioethanol was obtained. Autoclaved wheat straw at 121°C for 15 minutes gave the highest ethanol yield of 16.95% using the marine yeast W. anomalus M15.

This work has developed a series of strategies for the efficient hydrogenation of CO2 to different products with applications as chemicals and fuels. The main focus has been on the synthesis of formic acid (FA). Thermodynamic and kinetic barriers imposed in the hydrogenation of CO2 to formic acid have been overcome by utilizing ionic liquids as additives in the reaction. In the first part the beneficial thermodynamic role of ionic liquids acting as a buffer is described. The buffering properties of ionic liquids are afterwards utilized to develop a structure-activity relationship for a range of catalysts including homogeneous and heterogeneous examples. This enables for the development of highly efficient catalysts in the hydrogenation of CO2 to FA. When CO2 is used as feedstock for carbon-based material, the reduction of the oxidation state at the carbon is critical in order to generate a highly diversified product portfolio. Formic acid is, beneath carbon monoxide, the first product with a reduced oxidation state at the carbon atom. Consequently, formic acid represents a perfect starting point for the development of decarbonised chemical value chains. Furthermore, it is both industrially relevant and has potential to be implemented in future technologies including hydrogen storage schemes, thus underlining the importance for the development for new processes for the synthesis of formic acid. However, the catalytic transformation of CO2 with hydrogen is thermodynamically and kinetically challenging. On the one hand, the formation of formic acid is thermodynamically uphill in gas phase and consequently the equilibrium is commonly shifted to the product side by the addition of stoichiometric amounts of bases. The key here is the formation of formate salts and adducts which would inevitably lead to tedious purifications and to the generation of large amounts of waste. Alternatively, the reaction is carried out in liquid phase which results in an acidic reaction media. On the other hand, CO2 is a kinetically inert molecule, thus necessitating highly nucleophilic, basic metal hydride complexes in order to activate CO2. If no bases are employed, the basicity of the active metal hydride complexes leads inevitably to a fast deactivation of the catalysts. This work addresses the thermodynamic challenges by utilizing ionic liquids (ILs) as additives in the reaction. The ILs act as a buffer during the reaction, thus stabilising the pH of the solution at higher values than that expected by the concentration of FA generated, whilst avoiding the formation of formate salts and adducts. Indeed, the additional stabilisation of formic acid falls into the range of an additional H-bond, compared to the pure solvent system. The buffering properties of ILs allowed also for the screening of different catalysts, including heterogeneous RuFe-nanoalloys. These nanoalloys displayed low activity and selectivity towards the formation of formic acid in comparison to the homogeneous counterparts. One major issue is the preferred formation of carbon monoxide under elevated temperatures, prohibiting efficient transformation rates. Consequently, a wide range of Ru complexes with pyridylideneamide ligands were screened for the hydrogenation of CO2 to formic acid. It was found that the rate of reaction can be enhanced by a) an increased electron density at the metal centre and b) by changing the dominant mechanism for the CO2 insertion into the metal hydride bond. The catalyst durability can be increased by increasing the resistance of the active hydride towards protonation. This is achieved by using pyridinium carbenes as coordinating sites. The catalyst stability and activity with pyridylideneamide ligands is in general good, in line with the literature reports. Based on the experience learned from the pyridylideneamide-based catalysts, a guideline for a highly robust, active and stable catalysts was created. The first example synthesised is a Ru-pincer complexes with N-heterocyclic (NHC) side arms as coordinating sides. Here, the NHC groups, mimic the strong electron donation observed with pyridylideneamides, whilst avoiding side reactions such as electrophilic attacks onto the ligand scaffold. This scaffold allows the performance of the catalyst at demanding reaction conditions without a loss in catalytic activity via the formation of heterogeneous nanoparticles. Furthermore, the structural design of the catalyst avoids the poisoning of the catalyst by the reagents, product or lewis acids. Consequently, the here developed catalyst achieved a TON of 833,800 with an initial turnover frequency (TOF) of 22,000 h-1. These results represent the best catalytic performance reported to date by a factor of 50 (TON) and 22 (TOF), compared to the best performing catalysts reported to date under base free conditions.

Calcium carbonate is an important compound in man-made cements as well as in cements used by several animals and bacteria to produce their skeletons and exoskeletons. The sedimentary layers of the Earth’s crust is rich in calcium carbonate, making it a globally abundant mineral being the main constituent in rocks such as limestone, marble and chalk. Animals and bacteria grow and tailor these materials in complex hierarchical structures for specific purposes, obtaining superior properties compared to man-made cements. Marine animals incorporate magnesium and macromolecules into their calcium carbonate skeletons to make them stiffer and increase fracture toughness. A deeper understanding of the processes of the formation, and the self-assembly of calcium carbonate in aqueous solutions, is the key to understand how we can target the final material properties of these materials. In this thesis, atomistic molecular dynamics simulations have been used to study the mechanical properties of magnesian calcites and the interactions between hydrated calcium carbonate surfaces at nanoconfinement conditions. The interactions between atomically smooth calcium carbonate surfaces in aqueous solutions at nanometer scale separations have been computed. The surface forces display characteristic oscillations due to the structuring of the water confined between the mineral surfaces, at surface separations < 1.3 nm. Adhesion between the surfaces is observed for surfaces in registry. It is demonstrated that the adhesion can be reduced or eliminated by shifting the surfaces out of registry. From the analysis of the surface forces, we derive the interaction potential per unit area as a function of surface-to-surface separation, which is used to obtain the force between two spherical calcite colloids via the Derjaguin approximation. We investigate the impact of surface roughness on the resulting intercolloidal potential. A large enough surface roughness is shown to eliminate the adhesive properties of calcium carbonate nanoparticles. The mechanical properties and the deformation response of magnesian calcites was studied using non-equilibrium molecular dynamics. The energy dissipation mechanisms in magnesian calcites depends on both the magnesium:calcium composition and the spatial distribution of these ions is the crystal lattice. By incorporating magnesium into magnesium-rich clusters, we show that calcium carbonate materials become stiffer than if the magnesium was evenly distributed.

The work presented in this thesis utilises the laser flash photolysis-laser induced fluorescence method to study the reaction kinetics of the four isomers of butanol, potential biofuels, under conditions relevant to low temperature combustion. Prior to the widespread use of these potential alternative fuels, their mechanism of low temperature combustion must be well understood, to ensure the best conditions for these fuels are employed in novel engines. Chapter 3 describes a detailed experimental study for the reaction of each of the four isomers of butanol (n-, i-, s- and t-butanol) with the hydroxyl radical at temperatures between 298 and 714 K, and at pressures between 30 and 130 Torr of nitrogen. This work presents the first temperature dependent study of these reactions at temperatures above 400 K and below 800 K, and has thus assisted in reducing the uncertainty of the bimolecular rate coefficient in this temperature region, which is crucial to low temperature combustion of these alternative fuels in an engine. Temperature dependent modified Arrhenius parameterisations were provided from this work, and also from concatenate fits to this work and high temperature shock tube data from the literature. The temperature dependence for the reaction of each isomer with OH obtained in this work can be described by modified Arrhenius parameterisations (all in units of cm3 molecule-1 s-1): kn-butanol+OH (298 – 715 K) = (1.15 ± 2.62) × 10–19 × T (2.64 ± 0.31) × exp(7800 ± 1100 R×T) ki-butanol+OH (298 – 607 K) = (2.05 ± 6.79) × 10–18 × T (2.20 ± 0.45) × exp (6800 ± 1600 R×T) ks-butanol+OH (298 – 690 K) = (1.38 ± 2.58) × 10–21 × T (3.22 ± 0.25) × exp (10330 ± 970 R×T) kt-butanol+OH (298 – 614 K) = (4.50 ± 23.7) × 10-21 × T (2.99 ± 0.71) × exp(5200 ± 2600 R×T) These parameterisations are crucial to the improvement of structure-activity relationships, for calculating branching ratios for the reaction of the butanol isomers with OH at temperatures relevant to low temperature combustion. Accurate total bimolecular rate coefficients and branching ratios for the reaction of butanol with OH are vital for modelling of combustion parameters such as ignition delay times, as demonstrated later in Chapter 5. Chapter 4 presents experimental observations and kinetic measurements of the b-scission decomposition of b-hydroxybutyl radicals above 480 K. The b-site radicals formed through hydrogen abstraction from butanol by OH decompose at these sufficiently high temperatures to produce a butene molecule and an OH radical. The ab initio energetic barriers v to decomposition for these radicals have been calculated at the CCSD/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level. The barriers calculated have also been optimised using master equation solving for b-site radicals derived from all isomers of butanol with the exception of s-butanol. The optimised barriers to decomposition of the radical are 103.4 ± 1.3, 93.0 ± 1.0 and 100.0 ± 2.6 kJ mol-1 for t-, i- and n-butanol respectively. The OH yield obtained in these experiments has also been used as a proxy for abstraction at the beta site of each butanol isomer, and equated to the percentage of OH reaction abstractions occurring at this site. Chapter 5 presents some unusual observations in which a growth of OH signal was observed at temperatures above 600 K in the presence of oxygen following the photolysis pulse, and some experimental tests were conducted to deduce the source of this behaviour. The bimolecular rate coefficient for the reaction of O (3P) atoms with n-butanol was measured at temperatures of 490 – 730 K, and pressures of 40 – 55 Torr, described by the Arrhenius parameterisation: kO(3P)+n-butanol (490 – 730 K) = (1.64 ± 0.55) × 10-10 × exp(-18700 ± 1700/RT) cm3 molecule–1 s–1.

The combustion of fossil hydrocarbons to meet global energy demand is widely considered unsustainable and there is substantial motivation to transition toward renewable energy sources. Nevertheless, increasing integration of these renewable sources is challenged by their intermittency, which necessitates the installation of robust energy storage systems. In this context, hydrogen is an advantageous energy vector but current technologies offer insufficient storage performance. Ammonia borane (AB) offers potential as a candidate storage material but is nonetheless challenged by the need for (i) accelerated release of hydrogen, (ii) reduction of gaseous contaminants, and (iii) formation of polymeric residues that enable regeneration. This research sought to resolve these issues by nanoconfinement of AB within highly porous titania aerogels. Initially, titania aerogels were prepared and characterised, with the effect of several synthesis conditions understood. The best performing of these materials exhibited excellent surface area (SBET = 660 m2/g), pore volume (VP = 1.17cm3/g) and mesoporosity (dP = 17 nm) that were among the highest reported for such materials. Importantly, it was found that extraction with carbon dioxide resulted in the formation of titania with surface bicarbonate functionality. The preparation of such functionalised materials typically requires the inclusion of carboxylic acids during synthesis, meaning this discovery represents a distinct route toward high performance materials. One titania aerogel was then studied for the nanoconfinement of AB for application as a hydrogen storage candidate, with the composite material designated AB/TA(L). Compared to bulk AB, the nanoconfined AB/TA(L) demonstrated distinct release characteristics including lowered onset temperatures (101 to 25 oC), reduced activation energy (171 to 85 kJ/mol), altered release kinetics, increased contaminants and reduced quantity of hydrogen. The cause of these fundamental changes was believed to be strong destabilisation induced by the aforementioned surface bicarbonate functionality, the amphoteric nature of which was speculated to mediate proton exchange. In contrast to trends in literature, this result directly implicates amphoteric materials as deserving further research. Whilst many of these changes prohibited application of AB/TA(L) toward storage applications, the findings highlighted new opportunities for nanoconfinement of AB. Additionally, the release mechanisms from bulk AB and nanoconfined AB/TA(L) were interrogated using two-dimensional infrared spectroscopy. These studies found the borane functionality of bulk AB was crucially involved in the release mechanism(s), with evidence to support the occurrence of counterintuitive homopolar interactions. Although such interactions have been reported before, this result appears to be the first evidence that confirms their existence without the possibility of hydrogen exchange.

Europium chalcogenide nanocrystals exhibit significant changes in their magnetic and luminescent properties as compared to bulk. The magneto-optical properties of these materials are strongly dependent on their shape, size, and surface conditions. O'Brien et al., have pioneered the preparation of many single source precursors as efficient routes to high quality, crystalline and monodispersed nanoparticles with semiconducting properties. This work in the second chapter presents the synthesis of nine novel europium compounds: [Eu(C6H5COS)3(phen)2] (1), [Eu(C6H5COS)3(phen)].CHCl3 (2s), and [Eu(C6H5COS)3(bipy)(MeOH)] (3s). tris(methyhexyldithio-carbamato)europium(III) -1,10phenanthroline [Eu(S2CN(CH3)(C6H13))3(phen)](4), tris(dihexyldithio- carbamato)europium(III)-1,10phenanthroline [Eu(S2CN(C6H13)2)3(phen)](5), teraphenylphosphonium tetrakis (ethylxanthato)-europium(III) (Ph4P)[Eu(S2COCH2CH3)4] (6), teraphenylphosphonium tetrakis (diethyldithio- carbamato)europium(III) (Ph4P)[Eu(S2CN(CH2CH3)2)4] (7) and tris- (dithiophosphato)europium(III) complexes: [Eu(S2P(OCH2CH3)2)3(phen)] (8), [Eu(S2P(OCH2CH3)2)3(bipy)] (9), followed by their characterisation by micro- elemental analysis, 1H NMR, infra-red spectroscopy and X-ray crystallography. Eu2O2S and EuS nanoparticles have been synthesized by the thermolysis and colloidal route as reported in the third chapter and decomposition of single source precursors. The nanoparticles were characterised by powder X-ray diffraction, transmission electron microscopy and scanning electron microscopy. In the fourth chapter the nanoparticles were characterised by UV-Visible spectroscopy and the band gaps were determined and magnetic measurements revealed that EuS nanoparticles show ferromagnetic behaviour at 10 K from compounds (2s), (3s), (4), (6) and (7), the exception is EuS nanoparticles from compound (5), which shows paramagnetic behaviour at the same temperatures. Reported studies of EuS nanoparticles from precursors (2s), (3s), (4), (5) and (7) show paramagnetic behaviour at 300 K with very small ferromagnetic contribution. In contrast, EuS nanoparticles from precursor (6), show no sign of formation of magnetic nanoparticles.

Clandestine laboratories are locations where chemistry is carried out in secret, often with the intent to produce illegal drugs or other controlled substances. These laboratories are unregulated and not maintained to a good laboratory standard, presenting a risk to first responders, bystanders and the environment. Electronic noses based on metal oxide semiconducting (MOS) gas sensors present a potential technology to create devices for the detection of clandestine activity. A range of sensors based on zinc oxide, chromium titanate and vanadium pentoxide have been manufactured and modified using zeolite material and metal ion doping. Sensor fabrication took place using a commercially available screen printer, a 3 x 3 mm alumina substrate containing interdigitated electrodes and a platinum heater track. Allmaterials were modified with the protonated forms of zeolite beta, Y, mordenite and ZSM5, by incorporating these materials into the metal oxide to make up 30 % of the total ink. Zinc oxide was also modified by indium doping; doping levels were set at 0.2, 0.5, 1 and 3-mol % indium. These materials were synthesised using a co-precipitation method. Sensors were exposed to a range of gases at operating temperatures between 250 and 500°C and concentrations between 50 ppb and 80 ppm. All tests were conducted on an in house testing rig, consisting of a 12-port sensing chamber, four mass flow controllers, six solenoid vales and supplies of compressed air and analyte gas. Modification of sensors was found to improve their responsiveness, compared to the control sensors, in almost all cases. This is due to a combination of surface area enhancements, increased adsorption of material and a more accessible microstructure. Machine learning techniques were applied to the sensor data to correctly classify the class of gas observed and to assess the overall sensor performance of each material. A high level of accuracy was achieved in determining the class of gas observed.

A number of light hydrocarbons are known to form hydrates with water at a combination of low temperature and high pressure. Under these conditions, it is not uncommon for hydrates to form and plug oil and gas pipelines and other equipment, resulting in shutdown, potential risk of explosion, and accidental release of hydrocarbons into the environment. Conventional chemical inhibitors such as methanol and ethylene glycol are the most frequently used tool in hydrate prevention strategies, however, they can result in significant capital and operational costs as well as health, safety and environmental concerns. An alternative to conventional inhibitors are Low Dosage Hydrate Inhibitors (LDHI), of which Kinetic Hydrate Inhibitors (KHIs) are the more frequently used. KHIs are water soluble polymers, which prevent or delay hydrates nucleation and/or growth. Over the last two decades, much has been learnt about the mechanism of KHI; however, gaps still remain in the knowledge surrounding the mechanism of inhibition. The research described in this thesis seeks to increase the understanding of KHI performance and was carried out from 2003 to 2008 and was a part of the Joint Industrial Project (JIP) titled "Micro and Macro-Scale Evaluation of Low Dosage Hydrate Inhibitors" conducted by the Centre for Gas Hydrate Research at Heriot Watt University. The research involved a series of laboratory tests using stirred autoclave reactors that qualitatively demonstrated that the presence of ethanol, methanol and alkanes have a negative impact on the performance of KHI, while salts and synergist 2-Butoxyethanol have a positive impact. The effect of methanol was supplemented with molecular dynamic simulation that demonstrated that the methanol preferentially adheres to the polymer structures. A multi test tube rocking cell was used to generate large volumes of data to investigate the stochastic behaviour of hydrate formation with and without KHI. The results showed that the commencement of hydrate growth is logarithmically related to subcooling, and higher pressures resulted in higher induction at comparative subcooling and driving force. The information gathered improves the understanding of factors that impact the performance of KHI, improves the understanding in the designing of appropriate testing of KHI, and enhances knowledge of kinetics of hydrate nucleation and growth.

Crystallization in multiphase systems is one of the major problems that is encountered during oil processing and oil transporting processes. In the petroleum industry oil and water are produced and transported together and this causes mixing of oil and water which may result in different flow behaviour. This study is concerned with the crystallization of calcium carbonate in oil-in-water emulsions. The crystallization process is studied by following the kinetics in which different CaCO3 polymorphic phases are developed on a surface and in the bulk solution using a combination of X-Ray Diffraction and Scanning Electron Microscopy. Kinetic measurements combined with microscopic observations have been monitored with time and found as a useful way for characterizing CaCO3 scale formation on a surface and in the bulk solution. This new approach enables a better understanding of the different stages of CaCO3 scale formation in single and multiphase systems. This includes the formation of different polymorphs, the kinetics of growth of each polymorph, the order of polymorphic appearance, the mechanisms of transformation of the metastable phase to the stable one and the prediction of the time required for a complete transformation to a stable phase. The results suggest the importance of the early period of the crystallization process. This period of time represents the nucleation and the growth of the metastable phase which exhibits simultaneously with the transformation to the stable phase. The solution supersaturation ratio is found to reduce by about 96% during this period. It is found that the formation of the more stable phase mainly depends on the formation and the transformation of the less stable phase. The results show the existence of an inhibition effect when adding an oil phase to the surface crystallization through retarding both the nucleation and the dissolution processes of the metastable phase. The oil phase impacts the dissolution process by changing the mechanism of transformation from surface-controlled to diffusion-controlled. This affects the kinetics of formation of the stable phase and results in a reduction in the overall surface deposition. The inhibition effect has also been shown to take place in the bulk solution where less nucleation has been detected for homogeneous type nucleation. At the same time the oil provides an extra surface where heterogeneous nucleation takes place. The presence of oil was shown to have more impact on surface crystallization kinetics than the bulk precipitation kinetics which showed similar bulk behaviour between systems with and without oil at 30o C and 60o C. The results suggest the existence of two simultaneous processes for the precipitation kinetics; the first is the rapid dissolution of the metastable phase followed by the re-crystallization to the stable phase according to a surface-controlled mechanism. This process takes place and ceases rapidly. The second process is the slow dissolution of the metastable phase and this is followed by the re-crystallization of the stable phase according to a dissolution-controlled mechanism. This process is very slow and proceeds for a much longer time. The existence of two processes in the bulk solution compared to only one process for the crystallization on a surface results in much faster kinetics on the surface than in the bulk solution. The results also suggest the similarity in the mechanism of formation and transformation of CaCO3 scale between surface and bulk solution.

Global energetic and environmental concerns have generated interest in the biological systems for the production liquid biofuels. Butanol is one such biofuel, which can be naturally produced by some Clostridia species. However, possible limitations in Clostridial engineering and large-scale fermentation have led to an examination of other potential organisms that might house this pathway for butanol production. As a robust industrial host and key model organism in the study of fundamental biological processes, the yeast Saccharomyces cerevisiae has been used to house the Clostridial ABE-butanol pathway. However, butanol yields and titres in this yeast are relatively low. Therefore, in this thesis, three distinct strategies were carried out with the goal of optimising butanol production in the strain of yeast (previously constructed in the Ashe lab) bearing the ABE-butanol pathway: 1. Mutation of genes involved in the regulation of carbon source usage. 2. Deletion of genes where the product is involved in the consumption of cytosolic acetyl-CoA (the starting precursor for the butanol synthetic pathway). 3. Targeted mutagenesis to improve the efficiency of the thiolase enzyme, which catalyses the condensation of 2x acetyl-CoA to initiate the ABE-butanol synthesis pathway. The results showed the first two strategies did not lead to improvements in butanol yields. However, increases of intracellular acetyl-CoA were observed in some mutant strains, even though butanol production did not increase in these strains. In order to make maximum use of the accumulating cytosolic acetyl-CoA, thiolase engineering in the butanol production yeast strain was pursued. The introduced changes caused an increase in butanol (about two fold). Overall, this project has used a minimal engineering approach by modulation of associated pathways or optimisation of the heterologous enzyme with a view to improve butanol production in yeast. To achieve high and scalable butanol production in yeast, a robust approach involving whole synthetic biology - Design, Build Test, and Learn will need to be adopted to create a more efficient yeast-butanol system.

This work investigates the influence of inhibitor pigment volume concentration (PVC) on the microstructure, the barrier properties and the leaching behaviour of primer coating. The polymeric matrix of the primer coating is polyester based cross linked with blocked aliphatic polyisocyanate, whereas the active inhibitor is strontium aluminium polyphosphate hydrate (SRPP). The objectives are to correlate the PVC, primer microstructure to the leaching rate of phosphorus containing species and strontium, also, to discover the leaching mechanism and the dominant transport paths that serve as the passage for the release of phosphorus containing species and strontium. Quantitative energy dispersive X-ray spectroscopy (EDS) manifest that the concentrations of phosphorus containing species and strontium decrease throughout the entire thickness of the primer coating with relatively high SRPP PVC ( 25%). However, in a system with 10% SRPP PVC, the concentrations of phosphorus and strontium within the exposed primer coating decrease only within the regions, which are closer to the environment, whereas the concentrations of phosphorus and strontium within the regions further away from the environment are in a comparable range to that in the similar regions of the unexposed primer coating. On the other hand, microstructure characterization with scanning electron microscopy (SEM) shows that the addition and the increase of the SRPP PVC lead to formation of connection networks and clusters of connected SRPP pigment particles within the primer coatings. Also, asperities and discontinuities form on the surface of the primer coatings with the addition of the SRPP PVC, whereas the size and frequency of clusters of connected inhibitor particles and the asperities on the surface increase with the increase in the SRPP PVC. Further, the increase in the SRPP PVC leads to proportionately higher leaching rate, which could be beneficial for effective protection of the substrate, although it also leads to the depletion of the “reservoir” from the inhibitive species during short period of exposure to environment, which is undesirable. This behaviour indicates strong microstructural influence on the leaching process and is attributed to the spatial distribution of the SRPP pigments and the formation of connection networks and clusters of connected inhibitor particles. The EDS analysis illustrates the absence of detectable concentrations of phosphorus and strontium within the polymeric regions of exposed primer coatings. Therefore, transport of phosphorus containing species and strontium (if any) is highly restricted through the polymeric binder. On the other hand, the variations of the thickness of the primer coatings with similar SRPP PVC show lower leaching rate for thicker primer layers although the weight of SRPP pigment per cm2 of the primed substrate is higher within the thicker primer. This is attributed to thicker “skin layer” and/or lower number of discontinuities on the surface of thicker primer coatings, which indicates that the transport of the pigment species through the polymeric binder in the absence of easy transport paths is highly restricted and significantly influence the total leaching rate. Clusters of connected inhibitor pigments form with a critical size at percolation threshold (Pc). Therefore, percolation threshold (Pc) is proposed as a critical pigment volume concentration for inhibitor pigments, which together with inhibitor pigment dissolution and release properties should be considered during the primer design and formulation. If the inhibitor PVC is larger than the Pc, it could lead to significantly high release rates of inhibitive species (i.e. fast depletion) and significantly low barrier properties and 30 impedance of the primer coating. On the other hand, if the inhibitor PVC is just below the Pc, higher concentrations of inhibitive species can be released into the environment compared with the system that are further below the Pc, which is beneficial for effective corrosion protection, whereas the barrier properties and impedance of the primer coatings with active inhibitor PVC below the Pc are comparable to each other. Based on this study, a model is proposed for the leaching of inhibitive species released from the SRPP pigment. The release and leaching start at the loci of defects/discontinuities, where the inhibitor particle is in direct contact with the environment. The dissolution and release of inhibitive species lead to the formation of voids and cavities, which are filled with electrolyte. If the void forms at the locus of a particle, which belongs to a cluster of connected SRPP particles, the void is connected to another particle that can release inhibitive species into the medium of the void, which in the absence of the polymeric binder acts as an easy and direct passage for the transport of inhibitive species into the environment. Therefore, the leaching will continue until the cluster becomes completely depleted from the inhibitor pigments. On the other hand, if the void forms at the locus of an isolated and single particle, which is surrounded and encapsulated with the polymeric matrix, the leaching will stop after the dissolution and removal of the single particle. Based on this study and the proposed model, it is concluded that the diffusion of phosphorus containing species and strontium through the polymeric binder cannot contribute significantly to the total leaching rate. Therefore, the dominant transport paths for the release of inhibitive species are through the direct contact with the environment and the voids/cavities that are left behind after the dissolution and release of inhibitive pigments. The ratios of strontium to phosphorus concentrations within the leachate solutions are significantly higher than the ratio of strontium to phosphorus concentrations within the powder SRPP pigment. This is attributed to: 1-cationic exchange processes that replace strontium ions with cations from the environment such as sodium and potassium ions and 2- higher dissolution rate of strontium-rich particles compared with the phosphorus-rich and aluminium-rich particles that comprise the SRPP pigment.

From 1916 the "acetone butanol ethanol", or "ABE", fermentation process was the main production method for n-butanol. It was superseded in the 1950s by a more economical petrochemical process, causing the majority of plants to cease operation. In the fermentation, product inhibition led to low productivity and high energy demand in the downstream processing, making the process unable to compete with the petrochemical route. Overcoming these problems could revive the ABE industry and promote a bio-based economy. In situ product recovery (ISPR) can be applied to the fermentation process to counteract the effects of product toxicity. Productivity increases of greater than 300% are theoretically possible. Many ISPR techniques have been applied to the ABE process at laboratory scale, but a direct comparison of the different techniques has been hindered by experimental inconsistencies. Here, a techno-economic analysis was performed to compare the most developed ISPR techniques, with process simulations providing comparative data on the separation efficiency and energy demand. All the techniques were found to be economically viable, with profit increases compared to an equivalent batch plant of 110-175% and payback times of 2.2-4.5 years. In addition to generating the most profit and having the shortest payback time, perstraction was the only technique to lead to a reduction in overall plant energy demand, by ~5%, compared to a traditional ABE process. Thus perstraction warrants further investigation for application to the ABE process. Perstraction is significantly underdeveloped compared to other ISPR techniques. It was originally designed to overcome various problems associated with liquid-liquid extractions, including solvent toxicity. Here, experiments focused on the use of high-distribution toxic extractants with commercially available membranes. Results showed that high-distribution toxic extractants (1-pentanol, 1-hexanol, 1-heptanol, 1-octanol and 2-ethyl-1-hexanol) have a larger mass transfer coefficient than oleyl alcohol (the main non-toxic extractant), although chemical structure differences, such as branching, can have a greater impact on mass transfer than distribution coefficient. Unfortunately, all extractants investigated here were transferred across the membrane to some extent, which would limit perstraction to non-toxic extractants. However, differences in membrane type have a greater impact on mass transfer than the choice of extractant. Porous membranes have a mass transfer coefficient 10 times greater than non-porous membranes, which would see a factor of 10 reduction in ii membrane size and cost. Overall, this work has confirmed that perstraction is technically viable and compared options for process improvements through membrane and extractant selection.

The quality of Malaysian edible bird’s nest (EBN) is still regarded inferior due to issues related to nitrite content. In August 2011, the Chinese government imposed a ban on EBN products imported from Malaysia, due to the high level of detectable nitrite (NO2-). This nitrite contamination issue has made a great impact to the edible bird’s industry whereby many EBN farmers, traders and exporters are severely affected. In 2012, the China-Malaysia negotiations agreed on the use of radio frequency identification (RFID) tags on every individual package of Malaysian EBN and set the allowable nitrite limit to be less than 30 ppm, in order to allow exportation of Malaysian EBN to China. The processing methods in EBN industry still remain crude and lack of any form of technology advancement. The purpose of this study was to investigate infrared (IR) coupled with ultraviolet C (UVC) assisted intermittent drying as a mean of EBN processing in order to preserve its nutraceutical properties, ensure nitrite content less than 30 ppm and enhance the commercial value of the dried EBN products. In the present study, EBN were dried by IR assisted drying at low temperature (25°C, 26.7% RH and intermittency =1.00), UVC assisted drying at low temperature (25°C, 26.7% RH and intermittency=1.00) and IR-UVC assisted drying (25°C-40°C, 16.5%-26.7% RH and intermittency=0.20-1.00), respectively. Both engineering properties (drying kinetics, effective moisture diffusivity and effective thermal diffusivity) and quality properties (colour, nitrite content, moisture reabsorption ability, shrinkage, sialic acid retention, antioxidant retention and storage stability) of all dried products were assessed and evaluated. The comparisons were made against samples from fan assisted drying and hot air drying. The results revealed that intermittent infrared (IR) coupled with ultraviolet C (UVC) assisted drying at temperature of 40°C (IR-UVC40) with intermittency.

This work presents microfabricated microelectrodes, capable of quantitative analysis in molten salt (MS). MSs are an electrolytic medium of growing interest, especially in the area of nuclear reprocessing. However, designing sensors for a MS-based nuclear reprocessing system is a challenge, owing to the usually corrosive nature and high operating temperatures (typically 450 - 500◦C) of MS. Microelectrodes are well placed as sensors, with numerous advantages over macro-scale electrodes. As a consequence, there have been previous attempts to utilise microelectrodes inMS. However, these have not been successful and all have suffered disadvantages inherent in traditional microelectrode manufacturing. The microelectrodes presented in this work were produced using standard microfabrication techniques and characterised in MS. An analysis of failure mechanisms guided a systematic study of material combinations. This resulted in a sensor, which is capable of delivering quantifiable electrochemistry in MS. However, the lifetime and yield of the sensor were determined to only be 46% and 1.4 hours respectively. Further investigation of the microelectrode failure mechanisms guided several layout changes to the microelectrode design. By reducing critical area, where defects or pinholes could form, these resulted in improvements in performance. This increased the yield to 65%, while the average lifetime increased up to 45 hours. Test structures were designed to investigate the causes of the continued microelectrode failures and identified shorting between the electrode metal and silicon substrate. This suggests the existence of defects in the underlying insulator are the cause of the 35% of microelectrodes which never functioned. Separate test structures suggested the lifetimes of the microelectrodes could also be improved by removing the need for a metal adhesion layer. Tantalum has been suggested as a replacement electrode metal and a proof of concept study demonstrated the feasibility of employing thin film tantalum as an electrode metal in LKE. Using this technology as a platform, several proof-of-concept microelectrode designs are also presented: liquid microelectrodes, microelectrode arrays, and a nanoelectrode. These are targeted at specific sensing applications, and provide an expanded spectrum of measurements in MS.

Polyoxometalates, also known as heteropolyacids (HPA), are solid acids widely utilised in heterogeneous catalysis. The physicochemical properties of HPAs facilitate surface-type or bulk-type reactions, dependent on substrate polarity. For the latter, the gas-phase dehydration of ethanol was investigated representing an environmentally friendly solution to produce bio-ethylene, a key compound to the chemical industry; while for the former, the solventless liquid-phase isomerisation of α-pinene was studied due to the widespread applications of its derivates. Supported HPAs, exhibiting the Keggin structure, were prepared on commercial low surface area fumed silica and mesoporous high surface area SBA-15 via wet impregnation technique to elucidate structure-activity behaviours in both catalytic systems relative to their bulk equivalents. In addition, different types of HPAs, phosphotungstic acid (HPW), silicotungstic acid (HSiW) and phosphomolybdic acid (HPMo), were studied to observe the role of acid strength on product distribution. The successful synthesis of supported HPAs was confirmed by multiple characterisation techniques, revealing an inverse relationship between loading and dispersion which is further promoted through the use of mesoporous SBA-15 as the support, whereas non-porous fumed silica induced agglomeration which in turn increases the degree of crystalline water present in the HPAs. n-Propylamine TPD evaluated acid strength decreases in the order of HPW > HSiW > HPMo, which is independent of support. Support choice did not influence selectivity in either reaction, but did impact greatly on catalytic activity, imparting significant reaction rate and turnover frequency enhancement. For surface-type reaction, SBA-15 showed to be the optimal support due to greater active sites accessibility, whereas in the case of the bulk-type reaction, the fumed silica based materials, with larger 3D HPAs structures, even at low loadings, showed superior performance. Product distributions were affected through the choice of HPA, with higher selectivity towards camphene, for α-pinene isomerisation, and ethylene, for ethanol dehydration, observed over the HPW catalysts.

This thesis is focused on the study of the bis aromatic urea unit shown in Figure i. Particular attention is given to the self-assembly capabilities of the units as a consequence of aromatic ring functionality. The ease of synthesis, explained and developed throughout this thesis, and the properties of materials containing the units make them suitable for many industrial and biological applications (as described in Chapter 1). Chapter 2 describes a study on chemical structure variations oflinked bis aromatic urea units (a variation of RI -4, Figure i) and the correlation of these to self-assembly capabilities. The self¬assembly studies are focused around the gelating capabilities of the formed compounds. Variations of the covalent linkers and outer aromatic functionalities (see R x and RI-4 in Figure i respectively) afforded a series of organo and hydrogelators. It was found that those molecules with electron withdrawing moieties in the meta position relative to the urea bond (R2 in Figure i) formed the most effective self-assembly units. Chapter 3 details several low molecular weight hydrogelators based on mono, bi and tri-armed bis aromatic urea units. The Chapter specifically focuses upon their applications as water purification and drug delivery agents., Hydrogelators described in Chapter 2 are employed and expanded upon to increase water purification properties. It was found that the formed hydrogelators were capable of removing a range of industrial dyes from aqueous environments. Furthermore the biocompatibility of the systems and drug removal as well as release capabilities demonstrate the possibility of such systems in biomedical applications. Chapter 4 explores the results of the introduction of the bis aromatic urea self-assembly units into polymers as low molecular weight additives to enhance both the mechanical and healable properties of the bulk phase. This effect is achieved via supramolecular interactions between the units and polymers and specific self-assembly between the additives. Initial explorations were performed with poly( ethylene-co-acrylic acid) and low molecular weight mono and diacid additives. After this proof of concept stage was completed a range of bis aromatic ureas were then synthesized and blended with the polymers. These bis aromatic ureas additives had the dual functionality ofpromoting system toughness as well as lowering healing temperatures. The chemistries reported in Chapter 5 employed the results from Chapters 2 and 4 to link the most successful self-assembly units, via covalently bonds, to telechelic polyethylene glycol (PEG) oligomers to create healable polymeric coatings. Control over the systems mechanical and healable properties were realized via synthesis and blending of tri-armed polymeric units to the telechelic PEG derivatives. A significant advantage of employing a water absorbing polymeric backbone in the form of PEG was demonstrated in the ability ofthe formed systems to close punctures in coatings via swelling phenomena. Finally Chapter 6 reports an approach based upon the data described in the previous Chapters whereby polypropylene glycol oligomers (which are more hydrophobic in character when compared to analogies PEG systems) were endcapped with the self-assembling bis aromatic urea units and the physical properties of the resultant supramolecular networks assessed. These supramolecular networks exhibited remarkable self-healing properties.

It is proposed that an integrated ammonia-PEM fuel cell could unlock the potential of ammonia to act as a high capacity chemical hydrogen storage vector and enable renewable energy to be delivered eectively to road transport applications. Catalysts are developed for low temperature ammonia decomposition with activity from 450 K (ruthenium and cesium on graphitised carbon nanotubes). Results strongly suggest that the cesium is present on the surface and close proximity to ruthenium nanoparticles and that it produces activity in ruthenium by donation of electrons. The activity of sustainable cobalt for ammonia decomposition is shown to be a function of particle size and is more active on microporous carbon supports compared to mesoporous ones. Unlike ruthenium, activity for cobalt was not inuenced by the degree of surface graphitic nature and cobalt supported on microporous carbon approached the activity of ruthenium on the same support. In accordance with the sustainable objectives of this thesis, a case-study on the sustainability of ammonia as a sustainable hydrogen storage vector was undertaken. In this scheme, hydrogen produced from renewable electricity by electrolysis is con- verted to ammonia by the Haber-Bosch process and then converted back to deliver pure hydrogen at the point of use. The energy eciency and carbon footprint fell short of targets set by the US Department of Energy and the UK Department for Transport, the biggest impact was the production of hydrogen by electrolysis and not the Haber-Bosch process which accounts for only 9 % of total energy losses. To assess the feasibility of the ammonia-PEM fuel cell, a conceptual design was un- dertaken to quantify the palladium membrane size and catalyst quantity required for a typical road transport vehicle. The predicted quantity of palladium was excessive and future work must consider improvements to membrane technology.

This research explored different catalytic cracking zeolite additives to improve propylene selectivity and minimize dry gas yield. A comprehensive study of the effect of zeolite structure, pore system and crystal size on maximizing propylene production in FCC unit and the effect of post synthetic modifications on the physicochemical properties and cracking activity of ZSM-5 was investigated using X-ray diffraction (XRD), pyridine adsorption fourier transform infra-red (FTIR), 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and the catalytic cracking using n-heptane, as a model compound for heavy naphtha. The catalytic performances of these additives were evaluated in a fixed-bed reactor unit using n-heptane as a model compound for naphtha at temperatures 450 - 500 oC and W/F 38 - 92 gcat.h/mol. A range of zeolites were tested with ZSM-5 showing the optimum results at high feed conversion. Further studies on ZSM-5 crystal size illustrated that nano ZSM-5 (300 nm) was superior compared to the regular ZSM-5 (2000 - 4000 nm) in achieved conversion level and propylene selectivity. These improvements were attributed to the shorter path lengths for the reactant reducing diffusion constraints significantly. Modifying nano ZSM-5 acidity using steaming, acid leaching and silanation showed significant improvement over nano ZSM-5 parent. Mild steaming of nano ZSM-5 improved both n-heptane conversion and propylene selectivity whilst severe steaming only improved propylene selectivity. This work attempted to address the often discussed catalytic activity enhancement from mild steaming and identified newly created moderate acid sites as the source of increased activity. Dealumination by acid leaching decreased the total aluminium content of nano ZSM-5 and changed the Brønsted/Lewis ratio. Increasing the B/L ratio, increased the conversion and propylene selectivity. In addition, this research focussed for the first time on the silanation of nano ZSM-5 and its effect on n-heptane cracking, in particular, propylene and dry gas selectivity. Silica was deposited on the external surface of nano ZSM-5 neutralising the acidic sites and as a result, dry gas yield was significantly decreased due to the elimination of non-selective cracking. However, the trade off with conversion was high.

The valorization of the abundant yet recalcitrant biopolymer lignin via selective depolymerization to produce monomeric phenols could greatly improve the process economics of a lignocellulosic biorefinery. Ionic liquid pretreatment has been presented as a potential route to the effective separation of biomass, producing a clean and soluble lignin stream. This could present a significant opportunity for the use of homogenous catalysis for selective lignin depolymerization. Amongst the potential uses for renewable monomeric phenols from lignin could be as antioxidants to increase the oxidative stability of fuels. The aim of this work is to investigate the selective depolymerization of lignin to renewable phenols and also to assess the suitability of these compounds as antioxidants in fuel. Chapter 1 provides an outline of the research carried out to date in the area of lignin extraction and depolymerization to monomeric phenolic products, with a particular focus on ionic liquid (IL) pretreatment processes and the degradation of model lignin compounds by homogeneous catalysts. An introduction to the use of phenolic antioxidants in the stabilization of biodiesel is also presented. Chapter 2 reports the systematic study of the activity and selectivity of a range of homogeneous vanadium complexes for the catalytic degradation of phenolic and nonphenolic ß-O-4 model lignin compounds. The effects of changing the ligand structure are investigated, in addition to the effect of temperature, catalyst loading and availability of oxygen. Activity and selectivity were found to be highest for catalysts with bulky alkylsubstituted, monophenolate ligands. Chapter 3 investigates the stability and activity of several of the vanadium catalysts developed in chapter 2 for the degradation of model lignin compounds in a range of ILs. The majority of this work was conducted during a three-month placement in the Biomass Pretreatment team at the Joint BioEnergy Institute in Emeryville, CA, USA. A comparison of catalytic activity and selectivity in the degradation of a ß-O-4 model compound in DMSO and the IL [Emim][OAc] was conducted, along with a range of studies in mixtures of the two solvents. Whilst overall activity was lower in the ILs, selectivity for the desired C-O cleavage reaction was dramatically improved. The attempted catalytic degradation of an a-O-4 model lignin compound is also presented, along with preliminary studies of the depolymerization of alkali lignin by homogeneous vanadium catalysts in [Emim][OAc]. Chapter 4 describes the development of a high-throughput accelerated fuel oxidation rig. It also details its subsequent use in the assessment of the antioxidant properties of three renewable phenols, obtainable from lignin, in increasing the oxidative stability of rapeseed methyl ester (RME) biodiesel. The activity of the renewable phenols was compared to that of the commercial antioxidant butylated hydroxytoluene (BHT). Whilst less active than BHT, the renewable phenols were found to be active as antioxidants in RME biodiesel; the trend in activity was observed to be related to the substituents at the 2' and 6' positions. Fuel properties of blends of these renewable phenols are also presented. Chapter 5 summarizes the findings of the thesis and places them in the context of the thesis aims, whilst chapter 6 presents the experimental and synthetic methodologies employed in the thesis.

Driven by the demand for soot-free combustion, laser-based diagnostic techniques on soot have been developing since the late 1980s. One of these techniques is line-of- sight extinction, which is a fast, low-cost, and quantitative method to investigate the soot volume fraction in flames. However, the extinction-based technique suffers from relatively high measurement uncertainty due to a low signal-to-noise ratio, as the single-pass attenuation of the laser beam intensity is often insufficient. Multipass techniques can increase the sensitivity, but may suffer from a low spatial resolution. To overcome this problem, in the present study, we have developed a high spatial resolution continuous wave laser-cavity extinction (CW-LCE) technique to measure the soot volume fraction from low-soot producing flames. A laser beam cavity is realised by placing two partially reflective concave mirrors on either side of the laminar diffusion flame under investigation. This con guration makes the beam convergent inside the cavity, allowing a spatial resolution within 200 um, whilst increasing the absorption by an order of magnitude. Three different hydrocarbon fuels are tested: methane, propane and ethylene. The measurements of soot distribution across the flame show good agreement with results using laser-induced incandescence (LII) in the range of the soot volume fraction from 20 ppb to 15 ppm. The system is further applied to the measurement of soot volume fraction pro les of a series of nitrogen-diluted methane diffusion flames. The results of CW-LCE agree well with LII. The effect of fuel dilution on soot is interpreted by using a numerically calculated flow velocity and temperature eld. It is found that a previous one-step model for soot formation may underestimate the suppression effect by dilution. This is because diluent addition may shift the location of the sooting region away from the high temperature region, shortening the residence time for surface growth of soot particles. The effect of each factor (thermal, dilution, residence time) responsible for soot reduction is isolated and quantitatively compared. The size of soot particles is another important aspect of comprehensive soot measurement, and to address this aspect, a planar two-dimensional two-colour time-resolved laser-induced incandescence (2D-2C-TiRe-LII) method is developed and employed to investigate the soot formation in a series of standard ethylene and methane laminar diffusion flame. The time resolution of the 2D-LII signal is realised by shifting the delay time of the ICCD cameras. A two-colour con- guration is applied to measure the peak temperature of soot particles after the laser pulse, rather than use the energy balance equations to compute the peak temperature, which may introduce signi cant uncertainty. By combining with the CW-LCE technique, both a soot particle volume fraction and a particle size distribution map of the flame are obtained, using a minimum error approach.

The aim of this project was to produce solid adsorbents and catalysts in a continuous flow process. These materials are traditionally made in a batch process. The materials were made and the effect of the change in synthesis explored. When hydrotalcite was produced in a batch process it was found to yield material that was synthesised by a reaction governed by thermodynamic control. Contrary, solid formation in a continuous flow it was found to be governed by a kinetically controlled reaction. During the batch reaction the reactants had time and mobility to precipitate, dissolve and re-precipitate in order to arrive at the lowest energy configuration. This configuration resulted in aluminium from one meixnerite intermediate layer aligning with aluminium in the opposing layer (referred to as “in phase”). This allowed carbonate anions to join the layers together creating a crystalline structure by balancing its charge between the two aluminium atoms. In a continuous flow process the reactants were not afforded either the time or space to move. This resulted in aluminium being randomly located within the meixnerite intermediate. Due to the random placement of aluminium, the aluminium in opposing layers did not consistently align (referred to as “out of phase”). Carbonate anions bound to these out of phase aluminium atoms are unable to balance their charge by linking layers together. The anions compensated by taking up hydrogen and forming a bicarbonate anion. The remaining aluminium took up monovalent nitrate anions in the absence of any divalent anions. Hydroxide anions would have been more favourable but they were required in the formation of the lattice. It was also found that the kinetically controlled product could be converted to the thermodynamically controlled product by washing. Washing, however, degraded the lattice structure and washed away an amount of material. The hydrotalcites produced by continuous flow process were thermally decomposed to act as a carbon dioxide adsorbent. They decomposed much faster than their batch counterparts, suggesting the carbonate bridge provides thermal stability to the material. The decomposition also revealed that the magnesium/aluminium spinel recorded in other studies did not form for the materials produced in a continuous flow process. Instead the material decomposed to the separate metal oxides. This did not have an effect on the ability of the material to adsorb carbon dioxide and performed comparably to the batch process materials. The continuous flow process was used to create a Ni/Mg/Al hydrotalcite that could be used as a catalyst in ethanol steam reforming. The continuous flow process allowed three processes for introducing nickel into the system: the doping of the starting reagents, ion exchange during the washing process and the impregnation of the dry product. The doped samples produced material comparable to those produced in continuous flow without doping or washing. The ion exchange and the impregnation samples produced samples that are comparable to those produced in continuous flow with washing The doped samples exhibited a fourth region of weight loss in thermogravimetric analysis which is speculated to be the formation of nickel aluminide at high temperatures. The catalytic activity corroborated this idea with an increase in metallic behaviour. The doped sample was found to be the more active sample tested. In order to further test the effect of kinetic and thermodynamic control during the continuous flow process, an attempt to control the particle size of zirconium basic sulfate was made. It was found that the particle size could be altered in the batch process due the variable environment within the reactor. Inefficient mixing created concentration gradients and inefficient heating created temperature gradients. It was these gradients within the batch reactor that facilitated the thermodynamic product to be produced and the particle size to increase. In a continuous flow reactor these gradients did not exist. The advantage of the flow reactor was the ability to control the environment of the reactor in an even and uniform manner. The uniformity of the reactor environment eliminated any temperature or concentration gradients, keeping all the materials at similar chemical potentials, limiting particle growth.

Coal tars are complex mixtures of inorganic and organic compounds, which are dominated by PAHs and were produced as a by-product of the former manufactured gas industry. Forensic analysis of coal tar samples was carried out using two dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOFMS). This thesis first presents the application of existing multivariate statistical models developed using UK tar samples to tar samples from the USA as well as identifying 947 individual compounds present within the tars. This has important implications as this study demonstrated that statistical methods developed using UK tar samples can be successfully applied to non-UK tars. The thesis then presents the application of post extraction derivitisation to a creosote samples allowing for the detection of 255 compounds, the majority of which would not be detected without derivitisation. The analysis also detected 1505 individual compounds within the Creosote and provides the most comprehensive list of compounds detected within Creosote that has been produced. The analysis was also able to suggest the production process for the tar from which the Creosote was distilled. The use of both derivitisation and GCxGC were vital in providing this forensic information. The thesis then presents the analysis of 16 tar samples using GCxGC and post extraction derivitisation and the production of a database of 2373 individual compounds detected within the tar samples. The study showed that 163 individual compounds were present within all tar samples regardless of the production processused. This has important implications as environmental assessment usually focuses on a limited number of compounds, which could be expanded using the database presented within this thesis. Finally the thesis presented a study that analysed a sample of Pintsch Gas tar, which has never previously been analysed using a mass spectrometer and produced a unique dataset.

With the rapid development of society, the soaring consumption on fossil energy and the heavy environmental deterioration, looking for sustainable and clean energy such as solar, wind, hydrogen, has become the top priority for improving the environment pollution and accelerating the economic growth. However, the time and region limitation unable to meet the regional demand of energy, therefore, the research of effective energy storage and conversion (EESC) devices has become the research priorities. Lithium ion batteries (LIBs) as one of the EESC devices have been studied by many research groups. Oxygen evolution reaction (OER), as the anode reaction in water splitting and positive electrode charging reaction in metal-air batteries, plays a crucial role in the field of EESC. Composites of carbon material and metal oxide (or hydroxide) with their intrinsic properties can be used in the above two field as an anode or an electrocatalyst, respectively. But the common preparation method published in most articles for this type of composites usually contains two steps: first, the carbon materials should be oxidized to introduce oxygen functional groups to react with metal ions, then followed with hydrothermal reaction to make sure the reaction happened between oxidized carbon material and metal ions and finally to generate the composites of carbon materials and metal oxides. Herein, Fenton reaction with Fenton reagents (Fe2+-H2O2) was used to synthesize composites of carbon material and metal oxides (or hydroxides). Because carbon material could be firstly oxidized by Fenton reagents and secondly Fe3+ in Fenton reagents can be used as iron sources. Hence, in this work, composites of Fe(OH)3 and expandable graphite nanosheets (Fe(OH)3/EG), Fe(OH) 3 and multi-walled carbon nanotubes (Fe(OH)3/MWCNTs), Fe2O3/MWCNTs, NiFe layered double hydroxides and MWCNTs (NiFe LDHs/MWCNTs) were prepared by Fenton reaction with sonication assistance. and Fe2O3/MWCNTs used as anode material in LIBs and NiFe LDHs/MWCNTs used as electrocatalyst for OER were investigated, respectively. influence on particle size and crystal structure of metal hydroxide in the process of crystallization, hydrothermal treatment was applied after Fenton reaction which was named as EG-F-H and MWCNTs-F-H, respectively. However, the results show that MWCNTs-F without hydrothermal reaction has higher capacities than that of MWCNTs-F-H. Because the particle size of metal hydroxide on MWCNTs-F surface is smaller than that of MWCNTs-F-H, and part of metal hydroxide particles located on the surface of MWCNTs-F could drop down to the solution during the hydrothermal reaction. And EG-F also show a higher capacity than that of EG-F-H. In the Fenton reaction process, sonication was used to enhance the reaction. Hence, the optimized sonication time was also selected according to the properties of composites and the optimized sonication time is 3h. Composite of Fe2O3/MWCNTs was prepared by Fenton reaction with a heat treatment (200℃) to ensure that Fe(OH)3 was transferred to Fe2O3. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) etc. The XRD and Selected area electron diffraction (SAED) display that Fe2O3 in the composite has an amorphous structure, and SEM shows Fe2O3 nanoparticles load on MWCNTs surface. This indicates that MWCNTs was oxidized by Fenton reagents and introduced oxygen functional groups with negative charge. The electrostatic interaction between MWCNTs and iron ions with positive charge finally promote the production of composite of Fe2O3/MWCNTs. The electrochemical measurement for composite used as an anode in LIBs shows that the composite of Fe2O3/MWCNTs exhibits an excellent cycle performance with a reversible capacity of 900 mAh/g at 500 mA/g after 500 cycles and a high rate capability of 785 mAh/g at a high current density of 2 A/g. It is ascribed that the random ordered amorphous structure of Fe2O3 decreases the ion pathway and increase the diffusion of Li ions. The MWCNTs substrate provides an electronic path way and promotes the charge transportation and enhances the rate capability. Herein, NiFe LDHs/MWCNTs as an electrocatalyst used as a type of EESC was also synthesized by obtained by Fenton reaction followed with a coprecipitation process. Ni ions was simply added into the suspension of MWCNTs after the process of Fenton reaction under pH=9-10, NiFe LDHs/MWCNTs was obtained. XRD and SAED images indicate that the composites have low crystalline structure because the temperature and pressure used in this reaction is room temperature and atmospheric pressure with short reaction time. Linear sweep voltammetry (LSV), Chronopotentiometry (CP) and multi-CP were used to test their electrocatalytic properties. The results show that F(3-1)3 (named based on total ration and molar ratio between Ni: Fe explained in experimental part) displays excellent electrocatalytic properties with small overpotential of 212 mV and 283 mV at 10 mA/cm2 and 100 mA/cm2, respectively, and a few Tafel slope of 64.46 mV/dec. The outstanding electrocatalytic performance is traced to the low crystal structure of NiFe LDHs nanoparticles which could expose more active sites and facilitate the reaction between electrode and electrolyte. MWCNTs is also responsible for the excellent electrocatalytic properties, because MWCNTs enhance the conductivity of composites and improve the kinetic of OER.

The effects of hydrogen bond formation have been probed in four series of alkylammonium nitrates by increasing the alkyl chain length and by increasing the number of alkyl chains attached with a series of powerful spectroscopic and thermal techniques. Thermal analyses have been used to assess the decomposition temperatures. From thermal analyses it was determined that the majority of alkylammonium nitrates decompose before melting and formed plastic phases, a very important characteristic for fuel cell applications. By using inelastic neutron scattering technique, the entire frequency range from 0 to 4000 cm-1 has been resolved as a result of the absence of the optic selection rules. Hydrogen bonding networks have been studied in the frequency range below 300 cm-1 with inelastic scattering technique accompanied by ab initio and molecular dynamic calculations. The intra-molecular interactions have been asses in the high frequency range by infrared and Raman spectroscopy. By solid-state nuclear magnetic spectroscopy both types of nitrogen moieties have been identified by more than one signal per nucleus which indicates the high complexity of the chemical environment. Crystal structures showed significant strong hydrogen bonds formed between the two ions and a typical layering configuration as in micelle formations. The layered configuration is the consequence of electrostatic, van der Waals and the presence of the extensive hydrogen bond networks. The symmetry of the anion has been lowered and has been assessed through the N-0 in plane bend vibration. Increasing the alkyl chain length above four does not bring any significant differences in the chemical and physical properties. The most significant differences have been observed for the series where there is only one alkyl chain attached leaving three hydrogens available for bonding.

The selective oxidation of alcohols to the corresponding carbonyl product is an important transformation. Traditionally this reaction has been carried out using stoichiometric oxidants, but such methods are highly undesirable from an environmental viewpoint. In the fine chemical and pharmaceutical industries, oxidative transformations prove problematic, and are often avoided, due to a limited number of existing chemoselective and sustainable oxidation methods. The demand for new, environmentally sustainable and efficient alcohol oxidation methods has driven academic research, and a number of systems have emerged which employ catalytic metal loadings with oxygen as the terminal oxidant. In terms of sustainability, oxygen is the ideal oxidant as it is abundant, and water is the only byproduct formed during aerobic alcohol oxidation catalysis. In spite of the progress made in recent years, the introduction of such systems into industrial processes has not occurred. The aim of this thesis is the development of sustainable and industrially viable catalyst systems for aerobic alcohol oxidation. The research reported in this thesis studies two different catalytic systems. Firstly, the combination of nitroxyl radicals with copper complexes was explored (Chapter 2). The substrate scope was studied, using different nitroxyl radicals, exploring the effect of steric hindrance. The influence of mass transfer and gas pressure was also examined, in order to more efficiently utilise these expensive nitroxyl radicals. In Chapters 3 and 4, research was focused on a zeolite encaged 1,10-phenanthroline-Pd(NO3)2 catalyst system. The aim of these studies was to develop a stable Pd(ll) catalyst which would exhibit longer lifetimes compared to homogeneous systems.

This thesis is about the study of developing novel catalysts and catalytic processes and applying them to convert renewable alcohols produced from biomass into value-added chemicals. It focuses on developing iridium catalysts for hydrogen transfer initiated dehydration of 1,3- propanediol in ionic liquids as solvent and applying functionalized ionic liquids as homo- and heterogeneous catalysts for dehydration of D-sorbitol and rac-1-phenylethanol respectively.