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This thesis describes research into the utilization of conducting polymer polyaniline (PAni) as a material for the development of asymmetric hollow fiber membranes for gas separations. In order to ensure the consistency of the emeraldine base PAni molecular weight and the quality and purity throughout this research, the fresh batch polymer was synthesized in-house prior to each hollow fiber spinning. The initial gas permeation test revealed that the hollow fiber fabricated with high molecular weight PAni was favourable due to the highly viscous solution prepared with significant polymer chain entanglement that contributed to the formation of a more desirable membrane structure. However, the major turn around of the work was the introduction of volatile tetrahydrofuran (THF) to less volatile N-methyl-2-pyrrolidone (NMP) in the dope solution that promoted a proper formation of integrally skinned membranes. The effective removal of THF at a high spinning air gap further improved the fabricated membrane morphology which consisted of a denser effective skin layer, transition layer and finely porous substructure with smaller macrovoids. In addition, the spine line stress-induced orientation at a high air gap was responsible for further stretching the nascent fiber creating more packed structure that assisted toward improving the gas separation performance of the membranes. The induced molecular orientation also resulted in improvement in mechanical properties of the hollow fibers. Polyaniline derivative was synthesized to overcome the PAni solubility issue and to suppress the formation of PAni micro-agglomerates in the highly viscous dope solution. Integrallyskinned hollow fiber membranes were successfully prepared by dry-jet wet spinning from poly(ortho-anisidine) (POAn) dissolved in NMP and THF system. The bulky methoxy group introduced to the polymer backbone increased both the polymer chain rigidity and specific free volume of POAn as compared to PAni, producing membranes with significantly enhanced gas pair separation factors and small gases (hydrogen and carbon dioxide) permeation rates. The final focus of this study was investigating the potential effect of the aging process on PAni and its derivative membranes gas separation and mechanical properties. Poly(o-anisidine) membrane properties were found to be more stable than polyaniline membranes throughout the aging period, providing a strong foundation for further investigation of poly(o-anisidine) as a membrane material for gas separation towards commercial application.

Recently a large amount of interest has developed around separating out impurities of small size; pertinent examples are found within fuel and solvent processing. For such applications a leading candidate process is nanofiltration. This thesis focuses on SRNF (solvent resistant nanofiltration) composite membranes consisting of a dense polymer active layer bonded to a stronger, but ultimately more porous, support layer. The composite membranes that have been produced during the course of this work consist of a PDMS (polymdimethylsiloxane) active layer bonded to a commercially available support layer of PAN (polyacrylonitrile). To create the membrane a monomer was spread over the support layer and then polymerised to form the matrix which was responsible for separation. Commercially, either heat or radiation is often applied to cause polymerisation, however the membranes in the current work have been formed by the used of a homogeneous catalyst. This thesis investigates the transport and separation dynamics of the produced membranes for a series of fuel simulants composed of organometallics and poly-nuclear aromatic solutes dissolved in aromatic and alkane solvents. Membrane composition and the extent of polymer swelling were found to be the two key factors which had the greatest influence on solvent flux and solute rejection. By increasing catalyst concentration it was found that the dual effects of increased rejection and reduced flux occurred, with the converse also being true. The effective pore size of the membrane could also be controlled by varying the catalyst amount during manufacture as this directly affected the limit of crosslinking which formed. Polymer swelling was the most pronounced using solvents with a solubility parameter close to that of the polymer. The membrane transport mechanism was most accurately forecast by the solution diffusion model for flux predictions and the convection diffusion model for rejection predictions, however all the models tried were in close agreement. This was postulated to be due to the swelled polymer matrix which allows for both convective and diffusive transport to occur.

Smouldering combustion governs the burning of many materials in the built and natural environments. Smouldering is flameless, heterogeneous combustion which occurs when oxygen reacts with the surface of a solid fuel. Understanding the conditions which will result in the ignition and smouldering of a porous fuel is important and the phenomena involved are complex and coupled, involving heat and mass transfer, and chemical kinetics. This thesis reports experimental studies of the ignition, spread, suppression and emissions from reactions in porous media. Similar experimental techniques are shown in this thesis to be applicable when studying a wide range of solids which undergo self-sustaining reactions. This thesis is presented in a manuscript style. Each chapter takes the form of an independent paper which has been prepared for journal publication and as such, each chapter can stand on its own as a piece of research. A final chapter summarizes the findings and conclusions and suggests further areas of research. Chapter 1 presents a study of self-sustaining decomposition of ammonium nitrate containing inorganic fertilizer. This is of importance to the shipping industry which transports these materials in large quantities. Upon exposure to a heat source, ammonium nitrate may undergo exothermic decomposition which can propagate through the material, posing safety and economic threats. This reaction does not involve oxygenbased chemistry, but has many similarities to the propagation of a smoulder front in a porous material. Small-scale experiments to investigate the self-sustaining decomposition (SSD) behaviour of NPK (nitrogen, potassium, phosphorous) 16.16.16 fertilizer were undertaken. Experiments showed that this material will undergo self-sustaining decomposition and are used to formulate a reaction framework. Findings were applied to the events that occurred aboard the Ostedijk in 2007. Chapter 2 is a study of smoulder in polyurethane foam to study the relationship between sample size, critical heat flux and spread rate. Smouldering fires are the leading cause of residential fire deaths in developed countries and polyurethane foam is ubiquitous in the modern world. The critical heat flux for ignition was found to decrease with increasing sample size and the spread rate was found to be a function of the sample size, smoulder propagation depth and the applied heat flux. This is the first time that results on the effect of sample size on smouldering have been reported in the literature and these can be used to aid the extrapolation of small-scale flammability testing results to large scale scenarios. Chapter 3 presents an experimental investigation into the ignition of porous fuels by hot particles. This is related to the problem of spotting ember ignition in wildland fires which is a major, but poorly understood, spread mechanism. The process of spotting occurs in wildland fires when fire-lofted embers or hot particles land downwind, leading to ignition of new, discrete fires. The work studies the ignition of a fuel as a function of ember size and temperature. Metal particles are used as a proxy for burning embers and powdered cellulose to represent the forest fuel. Relationships between the size and temperature of the particle required for flaming and smouldering ignitions are found. These results are used to assess the ability of hot-spot ignition theory to determine the particle size–temperature relationship required for ignition of a cellulose fuel bed. Chapter 4 is an investigation into the suppression of smouldering coal. Subsurface coal fires are a significant global problem with fires in China alone estimated to consume up to 200 million tons of coal per year. As global demand for coal increases, accidental fires are a waste of a useful energy resource as well as a source of pollution and greenhouse gases. The results are the first attempt reported in the literature to study the suppression of these fires under controlled laboratory conditions. The ignition, spread and suppression of subsurface coal fires were studied using small-scale laboratory experiments. Time to ignition was seen to depend on particle size with small and large particles resulting in long times to ignition, while medium sized particles resulted in the shortest time to ignition. The maximum temperature, spread rate and mass lost were found to be independent of particle size above a critical particle size. The effectiveness of three systems for delivery of a suppression agent were assessed – direct injection, shower and spray. The effect of particle size on the water required for extinguishing using a spray was found to be weak. Chapter 5 presents an experimental investigation of the smouldering behaviour of peat. This is of particular interest in understanding the impact of smouldering fires on the earth system. The longer burn durations and different combustion dynamics of smouldering compared to flaming means that they have been shown to consume large amounts of biomass in, and contribute significantly to the emissions from, natural fires occurring in peatlands. The dynamics of smouldering peat in shallow, strong fronts was studied in the Fire Propagation Apparatus and a smoulder reaction framework with two burning regimes is presented. The first regime is peat smouldering and was found to be controlled by the applied heat flux and the second regime corresponded to char smouldering and was more sensitive to the flow of oxidizer. Chapter 6 complements Chapter 5 with an analysis of the CO and CO2 emissions for smouldering and flaming peat. This data can be used with large-scale measurement techniques to improve emission estimates. The emissions are found to be dependent of the burning regime and the type of combustion with flaming resulting in higher fluxes of CO2 and lower fluxes of CO compared to peat smouldering. Char smouldering resulted in the highest yields of CO and CO2. The large majority of emissions (85% of CO2 and 97% of CO) are released during the smoulder phase of the reaction. This highlights the differences in the chemical processes occurring under these two modes of combustion. Chapter 7 summarizes the research undertaken in this thesis and presents possible further work.

Counter-current chromatography (CCC) is a separation technique, which utilises two immiscible liquid phases in equilibrium as stationary and mobile phases. It emerged in the 1970s and had been primarily used in academia. Over the past few years its application in the pharmaceutical industry has increased as a high-throughput system. However, most businesses are still reluctant to use this technique due to the lack of understanding in solvent selection, which is essential for experimental design. Additionally, instrument design was a mainly empirical methodology, because there were no reliable models available that could predict the performance of a CCC column. One aim of this research project was to improve solvent system selection for CCC separations in order to facilitate the use of greener solvents. Therefore, a solubility driven approach for solvent selection from a list of preferred solvents was developed. This approach enables rapid solvent system selection, and potentially improves sample loading, because solvent systems are chosen by taking the solubility of target materials into account. Another aim of this PhD thesis was to develop a novel model that can predict the performance of a CCC column from column dimensions. That enables the prediction of a solute’s elution profile from a CCC column from scratch using instrument and operational parameters only. Unlike previously developed CCC models, the novel model does not resort to empirical calibration. This model was validated using a series of experimental results from literature and successfully predicted retention times as well as peak resolutions.

This thesis offers a comprehensive study that analyses the relationship between polyimide (PI) organic solvent nanofiltration (OSN) membrane formation parameters, membrane structure, and membrane functional performance. The dissertation starts by addressing the structure-related problem of macrovoid formation, which arises when more open membranes are prepared. Incorporation of TiO2 nanofillers into the membrane matrix results in macrovoid-free, organic/inorganic PI/TiO2 mixed matrix membranes without compromising rejection. Subsequently, a detailed analysis of the membrane formation process, considering the dope solution composition, evaporation step, and structural properties of polyimides, was conducted. The effect of the choice of polymer/solvent/co-solvent/non-solvent was found to be very profound and qualitatively predictable through introduction of a complex solubility parameter. Increasing value of complex solubility parameter can predict higher rejections. The study of the evaporation in PI OSN membrane formation has shown that this optional step is undesirable, as its presence results in unaltered rejection and significantly lower flux. Nevertheless, the presence of a co-solvent, regardless of whether it is volatile or not, was found to be required as it promotes formation of a dense membrane top layer. We have also studied sensitivity of PI OSN membranes to small perturbations in polymer characteristics, such as: molecular weight, alternating diisocyanates to form the PI chain, and copolymerisation method (block vs random). Finally, we proposed a less hazardous route for the PI OSN membrane formation process, which would reduce environmental impact without compromising the separation performance of the existing membranes.

Froth flotation is the largest tonnage separation process worldwide and is used for paper deinking, water purification and, particularly, mineral separation. One of the key aspects of the performance of flotation cells is the behaviour of the liquid within the froth, as it is crucial to the purity of the product and a major influence on the overall recovery. Nonlinearities in models for liquid motion in the froth make them complex to solve and existing numerical solutions have been in two dimensions at most. In order to predict the performance of industrial flotation cell designs, a three-dimensional solution for these equations is desirable. Moreover, the understanding of the process would be enhanced if a transient model were used to predict the dynamics of foam drainage. In this work, the equations for the liquid drainage have been rearranged in order to make them analogous to a compressible version of the Navier-Stokes equations, coupled to an equation of state. A model for predicting the movement of the flowing foam has also been developed, which is able to solve for the foam velocity in two and three dimensions. This has allowed the transient behaviour of liquid in flotation foams to be modelled using Fluidity, a general purpose finite element method code that allows simulations to be carried out on unstructured adaptive meshes. This is an important feature for improving the computational cost of modelling these systems, as there are boundary layers present in the process, whose size is independent of the scale of the flotation system being modelled. These models have allowed, for the first time, to carry out numerical investigations of drainage for arbitrary flotation tank geometries in up to three dimensions, and have been verified against analytical solutions and compared to laboratory scale experiments with satisfactory agreement.

Although the transesterification reaction of triglycerides with alcohols is well known and practiced on a commercial scale (using acid or alkaline catalysts), there is plenty of scope to improve this process. One approach involves the use of heterogeneous catalysts that could be retained in a fixed bed, and this would enable a continuous process to be developed. With this aim in mind, zinc proline (Zn(C5H8NO2)2) was used as a catalyst, which was coated onto a cordierite monolith support (62 cells/cm2). Two different coating methods were explored, and SEM images of the surface revealed interesting crystal structures on the surface of the cordierite. Experiments were then performed in a batch reactor (120 ml) to assess the activity of the catalyst (molar ratio methanol:rapeseed oil = 12:1, T = 195ºC and P = 20 bar, 2 h duration). Although high conversions could be achieved, the catalyst was found to lose activity with time, and even the cordierite support was also found to be catalytically active. These aspects were explored further, in a continuous flow reactor, which had an i.d. = 6.2 mm, and multiple heated sections (500 mm each) into which pieces (10 mm long) of catalyst coated monoliths were inserted. Experiments were performed with packed lengths of 200 and 400 mm, and with liquid flows ranging from 0.1 to 2.9 ml min-1. Although it was shown that high conversions can be achieved over extended run-times (e.g. 100 to 200 min), it was clear that the catalyst was losing its activity. Measurements also showed, that during the course of an experiment, Zn was leaching, and this clearly contributed to catalyst deactivation Despite the loss in activity of the zinc proline catalyst, the reaction system developed in this thesis was shown to work well, and that it could be used to evaluate the performance of catalytically coated sections of monolith. To demonstrate the use of this system, a few scoping studies were also performed using SrO as a catalyst, which was coated onto the cordierite monolith.

Atmospheric pressure chemical vapour deposition is an industrially significant process for forming functional thin films. There is a great opportunity for increased scientific understanding with the aim of improving current processes and helping to formulate new ones. This work is concerned with developing a methodology to assist this ongoing concern. A combination of spectroscopic and chemometric techniques are used to investigate several chemical vapour deposition processes. The first investigation concerns the spatial concentration mapping of key by-products during the thermal chemical vapour deposition of tin oxide films through the use of near infra red laser diode spectroscopy. This novel two dimensional characterisation of the process has identified reaction hotspots within the process, and has identified the redundancy of part of the exhaust mechanism. Subsequently, there has been improvements to the head design, and the operation of the process.The main thrust of the investigations are focussed towards the use of chemometric methods, such as experimental design and principal components analysis, in conjunction with a suite of spectroscopic measurement techniques, to analyse the plasma enhanced chemical vapour deposition of silica films. This work has shown the importance of active oxygen species on the chemistry. It has also been shown that the film properties are highly dependant on oxygen concentration in the reactor, and hence active oxygen species forming in the plasma. The identification of by-products in the silica deposition process has also been carried out for the first time. Finally, this work also presents the first rigorous studies of a new precursor for silica deposition, dichlorodimethylsilane.

This thesis investigates the constant pressure cake filtration of interacting cellulose fibre/TiO2 (rutile) mixtures, and involved experimental studies using an automated pressure filtration apparatus. The influence of suspension composition, filtration pressure and solution environment on filtration has been discussed in relation to cake properties such as average cake porosity and specific resistance. To help interpret the filtration results, sedimentation data were also obtained. The average porosities of filter cakes formed from pure rutile and fibre suspensions in deionised water were approximately 0.6 and 0.75, respectively, and a steady and progressive increase in porosity with fibre fraction was generally observed. With filtrations at 450 kPa, the average specific cake resistances for pure fibre and rutile in deionised water were approximately 9.4x1013 and 4.2x1012 m kg-1 respectively, with the variation of specific resistance with solids composition showing a minimum. Similar trends were observed at other tested filtration pressures with suspensions in deionised water but not with filtrations of suspensions in 0.2 M NaCl and 0.1 M CaCl2 solutions. The minima in average specific cake resistance with solids composition for feeds in deionised water was attributed to rutile-fibre interactions. Abrupt transitions in cake structure were evident part way through some filtrations, and resulted in unexpected filtrate flow behaviour. This is an interesting phenomenon, and not only were the changes in cake structure relatively reproducible, but also the nature of the change could be altered by changes in filtration pressure, solids composition and/or solution environment. The study of fibre/particle binary filtration behaviour, in particular the porosity and specific cake resistance trends, were substantiated by relevant theoretical treatment and modelling analysis. With the porosity trends, an additive porosity concept seemed to represent the data better than interparticle penetration models. With the specific cake resistance trends, a semi-empirical equation was proposed which appeared to represent a wide range of binary mixture filtration data. A mathematical framework was also developed in an attempt to understand the underlying physical mechanisms which led to filter cake restructuring, and possible explanations were postulated.

During recent years crystallisation has found applications in many chemical industries, such as pharmaceutical, petrochemical, micro-electronics and food industries. Crystallisation is a basic step for purification or separation for a large variety of organic, inorganic and pharmaceutical compounds. Most of the product qualities are directly related to the shape of the crystal size distribution (CSD). The main difficulty in batch crystallisation processes is to accomplish a uniform and reproducible CSD. On-line control during the process allows for improved crystalline product quality, shorter process times and reduction or elimination of compromised batches. The actual prediction and estimation of the shape of the distribution at the end of the batch can provide useful information for monitoring or designing the operating curve for the supersaturation controller. Model-based approaches provide consistency of the CSD, can be used for better control and also for product design by reverse engineering the process to achieve the desired CSD and shape. This research presents a novel methodology for solving the population balance equation (PBE) for the estimation of the shape of the crystal size distribution for batch crystallisation processes. The approach combines the quadrature method of moments (QMOM) and the method of characteristics (MOCH), and provides a computationally efficient technique for the reconstruction of the whole crystal size distribution. The technique was used to estimate the kinetic parameters for the size-dependent growth and secondary nucleation, for potash alum-water system using industrial pilot plant data provided by BASF, Chemical Company. The combined technique was also used to estimate the size-dependent dissolution parameters for potash alum-water system, using laboratory scale data. The QMOM-MOCH solution approach is evaluated in a model-based dynamic optimization study, with the aim to obtain the optimal temperature profiles, which drive the system in both the supersaturated and under-saturated region, to achieve desired target CSD. Using growth, dissolution and nucleation parameters the technique was used to optimise the temperature trajectories to obtain bimodal and mono-modal distributions. The technique can serve as a soft sensor for predicting the CSD, or as a computationally efficient algorithm for off-line design or on-line adaptation of operating policies based on knowledge of the full CSD data. Additionally, the PBE model was solved using the method of characteristics under the assumption of constant supersaturation. At constant supersaturation growth is the dominating phenomenon, yielding a simplified analytical expression for the prediction of the CSD. The research presents the new methodology for the systematic design of the setpoint operating curves for supersaturation controlled crystallisation processes, which produces a desired target crystal size distribution (CSD) at the end of the batch. A design parameter, was introduced as a function of the supersaturation and time, and is evaluated for supersaturation controlled processes. Based on the design parameter and the simplified analytical model, the supersaturation setpoint and batch time are determined using an optimisation approach to obtain a target distribution with a desired shape. Two additional methods are also proposed that use the seed in conjunction with the supersaturation setpoint design, and analytical CSD estimator for shaping the product CSD. The first approach designs a seed recipe as a mixture of crystals resulting for example from standard sieve analysis. In this approach the seed was introduced at the beginning of the batch. The second approach introduces the dynamic seeding concept, which allows an easily implementable methodology to achieve complex target CSDs using seed with mono-modal distribution as a process actuator. These methodologies were validated for potassium dichromate-water system. Size-dependent growth kinetic parameters for the potassium dichromate-water system were identified using as experimental setup developed at Loughborough University. The experiments presented in the thesis also illustrates the simultaneous application of in situ Process Analytical Technology (PAT) tools, such as focused beam reflectance measurement (FBRM) for nucleation detection, attenuated total reflection (ATR) UV/Vis spectroscopy for concentration monitoring, as well as the in-line use of a Mastersizer for real-time CSD measurement in the case of the potassium dichromate in water system. The approaches provide a comprehensive framework for model-based dynamic optimisation of crystallisation processes, which combines efficient numerical solution approaches of the PBE with the formulation of novel optimisation problems. The techniques presented include controlled dissolution, simultaneous optimisation of operating policies and seed recipes and dynamic seeding. Simulation and experimental evaluations of the proposed approaches demonstrate the potential of the techniques to provide significant improvement in the current state-of-the-art in crystallisation control.

This thesis is concerned with tackling three major challenges of melamine formaldehyde (MF) microcapsules for delivering of core materials: reducing the formaldehyde content in the formulation, modulate the mechanical properties and reducing the leakage of the core material through the microcapsules. Thus, to reduce the formaldehyde content in the microcapsules, a low formaldehyde to melamine (F/M) molar ratio (0.20-0.49) compared to the conventional literature formulations (2.30-5.50) was used to produce the MF microcapsules in this study. It was found that there is a relatively small window of F/M molar ratio between 0.20 and 0.49 in which the wall thickness and nominal rupture stress of the microcapsules can be modulated significantly. Above 0.49 increases in F/M molar ratios only increase these properties marginally. Furthermore, to reduce the leakage of the microcapsules, organic/inorganic double shell composite microcapsules with MF/copolymer as the inner shell, and ripened CaCO\(_3\) nanoparticles as the outer shell were produced. A ~20 fold reduction in leakage was observed between the double shell composite microcapsules and the MF microcapsules by the end of 24 hours, and it was also found that the mechanical properties of these double shell composite microcapsules are dominated by the CaCO\(_3\) nanoparticles outer wall. Finally, calcium shellac matrix containing MF microcapsules and unripened CaCO\(_3\) nanoparticulate microcapsules (complex capsules) were also produced to reduce the leakage. A ~37 fold leakage reduction between calcium shellac matrix containing MF microcapsules and MF microcapsules alone by the end of 20 days was observed, and a ~14 fold reduction was found between calcium shellac containing unripened CaCO3 nanoparticulate microcapsules and the unripened CaCO\(_3\) nanoparticulate microcapsules alone.

Boiling in microchannels is a very efficient mode of heat transfer with high heat and mass transfer coefficients achieved. Less pumping power is required for two-phase flows than for single-phase liquid flows to achieve a given heat removal. Applications include electronics cooling such as cooling microchips in laptop computers, and process intensification with compact evaporators and heat exchangers. Evaporation of the liquid meniscus is the main contributor to the high heat fluxes achieved due to phase change at thin liquid films in a microchannel. The microscale hydrodynamic motion at the meniscus and the flow boiling heat transfer mechanisms in microchannels are not fully understood and are very different from those in macroscale flows. Flow instability phenomena are noted as the bubble diameter approaches the channel diameter. These instabilities need to be well understood and predicted due to their adverse effects on the heat transfer. A fundamental approach to the study of two-phase flow boiling in microchannels has been carried out. Simultaneous visualisation and hydrodynamic measurements were carried out investigating flow boiling instabilities in microchannels using two different working fluids (n-Pentane and FC-72). Rectangular, borosilicate microchannels of hydraulic diameter range 700-800 μm were used. The novel heating method, via electrical resistance through a transparent, metallic deposit on the microchannel walls, has enabled simultaneous heating and visualisation to be achieved. Images and video sequences have been recorded with both a high-speed camera and an IR camera. Bubble dynamics, bubble confinement and elongated bubble growth have been shown and correlated to the temporal pressure fluctuations. Both periodic and nonperiodic instabilities have been observed during flow boiling in the microchannel. Analysis of the IR images in conjunction with pressure drop readings, have allowed the correlation of the microchannel pressure drop to the wall temperature profile, during flow instabilities. Bubble size is an important parameter when understanding boiling characteristics and the dynamic bubble phenomena. In this thesis it has been demonstrated that the flow passage geometry and microchannel confinement effects have a significant impact on boiling, bubble generation and bubble growth during flow boiling in microchannels.

Today nucleate boiling is widely used in numerous industrial applications such as cooling processes because of the high achieved heat transfer rates for low temperature differences. It remains a possible cooling solution for the next generation of central processing units (CPU), which dissipate heat fluxes exceeding the capabilities of today’s conventional forced air cooling. However, nucleate boiling is a very complex and elusive process involving many mechanisms which are not fully understood yet and a comprehensive model is still missing. For this study a new experimental setup was designed, constructed and commissioned to investigate bubble nucleation, growth, departure and interaction during nucleate pool boiling from a silicon device fully immersed in fluorinert FC-72. The location of bubble nucleation is controlled by artificial cavities etched into the silicon substrate. Boiling is initiated with a heater integrated on the back and micro-sensors indicate the wall temperature at the bubble nucleation site. During this work three different silicon test section designs were fabricated and boiling experiments on these substrates successfully conducted. Bubble growth, bubble departure frequencies and bubble departure diameters for different dimensioned artificial cavities, varied pressure and increasing wall temperature were measured from high-speed imaging sequences. Bubble interactions like vertical and horizontal coalescence were visualised and their impact on the boiling heat transfer investigated. The influence of spacing between two neighbouring artificial cavities on bubble nucleation and departure frequencies, vertical coalescence frequencies and departure diameters was analysed. The acquired data are used as input for a numerical code developed by our collaborators (Brunel University, UK and Los Alamos National Laboratories, USA) and are a first step to validate the code. The code studies the interactions between bubble nucleation sites on solid surfaces as a network. The simulations will help design boiling substrates utilised for chip cooling applications with optimal artificial cavity distribution to maximise the cooling heat transfer.

This thesis presents a detailed study into the thermodynamic stability and dehydration kinetics of a model pharmaceutical channel hydrate: carbamazepine dihydrate. The model compound of different crystal habits and particle size distributions was prepared via solventmediated crystallisation technique and agitated hydration method. The causal relationship between key drying process parameters (i.e. temperature, pressure, relative humidity and organic solvent partial pressure) and dehydration behaviour of this model compound was established using Dynamic Vapour Sorption instruments. Solid state phase transformation mechanisms under these drying conditions were elucidated through the evolution of crystal structural determined by X-ray Powder Diffraction technique. Dehydration kinetics of carbamazepine dihydrate were found to be markedly influenced by increasing temperature, reducing pressure, low humidity and higher organic solvent partial pressure, providing that the drying environment stays below the critical humidity and partial pressure for the dihydrate and acetone solvate formations. Activation energy determined from the kinetic study allows differentiation between the physically bound water in the bulk and water of crystallisation. Agglomerated dihydrate however possessed a high free water retention capacity when it exceeded a certain particle size distribution. This type of agglomerate exhibited distinct closed structure characteristics, leading to a relatively more stable form of carbamazepine dihydrate, than those without inclusion of unbound water. The agglomeration effect can thus be potentially controlled and exploited to expand the environmental stability envelope of the desired hydrated forms during manufacturing processes. Subtle changes in the drying environment were able to induce polymorphic anhydrates of different stabilities. The solid state phase transformation pathway of carbamazepine dihydrate to the four polymorphic anhydrates and an amorphous form was strongly correlated to types of dehydration mechanism, and specifically to the accessibility of and interaction with surrounding solvent vapours (i.e. hydrogen bonding propensity). Alkanol solvent vapourmediated dehydration process was found to facilitate the formation of the thermodynamically stable anhydrate, without any loss in product crystallinity. Dipolar aprotic solvents however induced the (intermediate) formation of least metastable anhydrate, depending on the local chemical environment of solute-solvent system. In conclusion, the surrounding solvent vapour plays a crucial role in drying strategies for a channel type hydrate, as it provides potential to predict and tailor the polymorphism of the desired forms which could have profound implications on the quality and performance of the final product.

Batch distillation with chemical reaction when takes place in the same unit is referred to as batch reactive distillation process. The combination reduces the capital and operating costs considerably. Among many different types of batch reactive distillation column configurations, (a) conventional (b) inverted (c) semi-batch columns are considered here. Three reaction schemes such as (a) esterification of methanol (b) esterification of ethanol (c) hydrolysis of methyl lactate are studied here. Four different types of dynamic optimisation problems such as (a) maximum conversion (b) maximum productivity (c) maximum profit and (d) minimum time are formulated in this work. Optimal design and or operation policies are obtained for all the reaction schemes. A detailed rigorous dynamic model consisting of mass, energy balances, chemical reaction and thermodynamic properties is considered for the process. The model was incorporated within the dynamic optimisation problems. Control Vector Parameterisation (CVP) technique was used to convert the dynamic optimisation problem into a nonlinear programming problem which was solved using efficient SQP (Successive Quadratic Programming) method available within the gPROMS (general PROcess Modelling System) software. It is observed that multi-reflux ratio or linear reflux operation always led to better performance in terms of conversion, productivity for all reaction schemes compared to that obtained using single reflux operation. Feed dilution (in the case of ethanol esterification) led to more profit even though productivity was found to be lower. This was due to reduction in feed price because of feed dilution. Semi-batch reactive distillation opertation (for ethanol esterification) led to better conversion compared to conventional batch distillation, however, the total amount of acetic acid (reactant) was greater in semi-batch operation. Optimisation of design and operation (for ethanol esterification) clearly showed that a single cloumn will not lead to profitable operation for all possible product demand profile. Also change in feed and /or product price may lead to adjust the production target to maximise the profitability. In batch distillation, total reflux operation is recommended or observed at the begining of the operation (as is the case for methnaol or ethanol esterification). However, in the case of hydrolysis, total reflux operation was obseved at the end of the operation. This was due to lactic acid (being the heaviest) was withrawn as the final bottom product.

This work investigates the feasibility of applying high temperature oxygen separation to the sulphuric acid decomposition process, a step used in large scale hydrogen production processes currently under development. Porous and dense membranes are both considered. Equilibrium calculations show yttria-stabilised zirconia (YSZ), combined with platinum electrodes, to be a candidate membrane. Process simulations show the potential sulphur dioxide yield increases that could be achieved through the use of a high temperature oxygen separation membrane in two different configurations. Bespoke experimental apparatus was designed, procured and assembled in order to investigate the oxygen flux through YSZ membranes in the presence of sulphur dioxide, during external voltage application. Experiments were performed in the 700 - 900°C temperature range. Results show that oxygen permeation through YSZ membranes occurs under these conditions. A decrease in oxygen permeation with time was observed and attributed to sulphur dioxide adsorption on to the platinum electrodes. Future work would concentrate on using variable applied voltages to reduce this performance decrease.

This thesis is concerned with the principal features of solvent resistant nanofiltration (SRNF), and in particular its potential in fuel processing. In the recent and more established literature, dense polydimethylsiloxane (PDMS) has been identified as a potential SRNF membrane with separation properties at a molecular level. This thesis investigates the transport and separation mechanisms of dense PDMS membranes in SRNF applications relating to the filtration of organic solvents (mixtures are mixed to simulate fuel). Simulated fuels were created which comprised representative organic solvents with organometallic (OM) and poly-nuclear aromatic (PNA) solutes. The solvent flux and solute rejection behaviour of the solvent-solute systems were studied using a cross-flow air-driven filtration apparatus and a range of operating regimes.

The aim of this research project is to improve the thermal performance of passive flat plate solar collectors using a novel cost effective enhanced heat transfer technique. The project work focuses on the process of energy conversion from the collector to the working fluid. This is accomplished by employing an aluminium grid placed in the channels of a collector to induce a gradient of heat capacitance. This novel technique is tested both theoretically by means of simplistic designs using Computational Fluid Dynamics (CFD) and experimentally using two unglazed collectors. One collector has the aluminium net inserted in its channels and it is tested against an identical conventional collector in order to have a direct comparison at the same time. The obtained CFD data and the experimental findings are coupled and show a good agreement. All the obtained results are validated with the literature. The results both theoretical and experimental demonstrate an enhancement in the heat transfer coefficient by 9 % resulting to an increase in the output temperature of the working fluid in the collector with the metallic insertion. Other parameters such as the Nusselt and Raleigh numbers supported these findings. Three novel expressions that correlate the Nusselt and the Rayleigh number, for different heat fluxes, were developed using data from CFD and experimental results. These correlations can be applied on any flat plate collector with an aluminium grid in its pipes, in order to predict its performance. Furthermore an existing lumped parameters model that predicts the output temperature of a collector was simplified and improved.

The mixing of additives into a plastic is an extremely important step in the plastics industry, necessary for the manufacture of almost every conceivable product. Therefore the costs in developing new products can prove very expensive as the testing is usually carried out using full scale machines, usually using twin screw extruders because they are able to provide good dispersive and distributive mixing. This is particularly important when compounding difficult to disperse additives and nano-additives. What is required is a machine that can replicate the mixing abilities of a twin-screw extruder but on a laboratory scale. There have been attempts by industry to develop smaller machines, such as the Thermo Scientific HAAKE Minilab II Micro Compounder which processes on the scale of 7 cm3 of material volume. This can be too small for some needs and therefore a machine is required to produce material on the 10g to 100g scale. To this end a laboratory mixer of novel design was devised and its mixing performance was assessed using conductive carbon black and compared against the Thermo Scientific HAAKE Minilab II Micro Compounder, a 19 mm co-rotating twin-screw extruder and a 40 mm co-rotating twin-screw extruder. Carbon black was used because mixing performance can be assessed by measuring the minimum carbon loading necessary to induce electrical conductivity. It was found that the minimixer was able to induce electrical conductivity at loading of 5.75% but the comparison with the other machines proved difficult as the achievement of the threshold at which semi-conductivity occurred appeared independent of shear rate and mixing duration.

There is an economic incentive to substitute energy and capital-intensive conventional gas separation schemes based on cryogenic distillation. Absorption has potential advantages over low-temperature schemes as it does not rely on high refrigeration requirements to perform the separation. An optimisation-based synthesis framework has been developed that integrates distillation and absorption-desorption schemes. This methodology is able to quantitatively resolve the numerous tradeoffs between the various capital and operating factors and systematically suggest new design configurations. A multilevel modelling approach enables the accommodation of absorption-desorption separation options in the distillation orientated framework supported by COLOM® (©Centre for Process Integration, University of Manchester). Improved shortcut models for reboiled absorption and distillation columns have been proposed, which are suitable for exploitation in the developed synthesis framework. A new methodology for heat integration is proposed that achieves efficient heat recovery and proposes a configuration of the heat exchanger network. This methodology works in harmony with the optimisation framework. Simultaneous optimisation of the separation system, the heat exchanger network and the refrigeration system offers the opportunity of achieving a superior overall configuration. The structural and operating variables of the separation system are optimised by Simulated Annealing. As a stochastic optimisation method, SA can deal with the large scale of the problem and its discontinuous and non-linear nature imposed by the feasibility limits of the separations and the model equations. The optimal separation configurations are selected on the grounds of minimum capital and operating costs. An analysis of costing methods is provided which aims at rationalising the basis for cost estimation. The application of the developed synthesis methodology is illustrated by a number of examples of relevance to the natural gas processing and refinery gas processing. Results will emphasise the functionality of the methodology as a tool for quantitative evaluation of preliminary designs and realisation of highly integrated and efficient process concepts.

This thesis presents a novel methodology for synthesis of sequences separating ternary heterogeneous azeotropic mixtures employing distillation columns and decanters. Column design methods are developed for assessing feasibility of proposed separations and for identifying economically attractive designs of columns in sequences. Design methods for advanced and complex configurations of heterogeneous azeotropic columns exploit the boundary value method. The methods can be used for establishing product feasibility in a column and evaluating a column design on a basis of cost. A new design method is developed for columns with integrated decanters, in which the existence of two liquid phases is not limited to the decanter. For a column with multiple heterogeneous stages, multiple feasible designs can be generated, corresponding to different numbers of heterogeneous stages and various ratios of two liquid phases on the heterogeneous stages. The resulting feasible designs have different total numbers of stages and feed locations for a given set of product specifications and reflux ratio. The new design method is extended further for double-feed columns and columns with intermediate decanters. Case studies indicate that the presence of heterogeneous liquid in columns considerably improves the economic performance in some cases. The economic performance is also affected by the number of heterogeneous stages. The number of heterogeneous stages that leads to near-optimal designs can be determined using the new column design methods. For some mixtures, employing complex column configurations makes the separation feasible and provides significant cost savings. For other mixtures, the complex columns may not be as attractive as single-feed columns with integrated decanters. Column design details and other results form the column design methods are used successfully to initialise rigorous simulations and to facilitate simulation convergence.

The application of pervaporation to the dehydration of aprotic solvents was investigated in this study. The performance of a commercial membrane, Celfa CMC-VP-31, was evaluated for the dehydration of tetrahydrofuran (THF) and dimethylformamide (DMF). The membrane was demonstrated to successfully dehydrate THF and calculations of water and THF permeance performed. When the membrane was applied to the dehydration of DMF, delamination of the top selective layer was observed and thus the membrane was deemed unsuitable for DMF dehydration. ' Polyaniline (PAni) was identified as a suitable candidate polymer for the formation of an aprotic solvent stable hydrophilic pervaporation membrane. PAni was synthesised in the lab and preparation conditions optimised and scaled-up to produce polymer with consistent batch to batch properties, in suitable quantities, to fabricate���· membrane sheets with sufficient surface area for testing. Casting solutions comprising of 20 wt% PAni were stabilised using an amine, 4-methyl piperidine, to prevent gelation and cross-linking prior to casting. Membranes were cast on a polyester non-woven backing and phase inverted in water to produce an asymmetric membrane structure. Scanning Electron Microscopy was used to examine the structure of the membranes formed. The effects of thermal treatment on the membrane film and polymer were investigated by a number of analytical techniques in order to devise a suitable procedure for membrane stabilisation. Thermally cross-linked PAni membranes were demonstrated to be water selective and stable in THF, DMF, ethyl acetate and ethanol. Permeance correlations with temperature were constructed to describe the performance of the membrane discs tested during solvent dehydration and compared to experimental data. Transport across the membrane was reported to be solubility dominated for all of the solvent systems tested. Finally, an examination of the reproducibility of membrane performance was made and further tests performed, to better understand variations observed in membrane pervaporation performance.

Three applications of two-phase flow and heat transfer in plate-fin heat exchangers have been studied. A dephlegmator is a heat exchanger in which reflux condensation of a vapour mixture occurs, and plate-fln versions have importance in cryogenic gas separation processes. Numerical calculations for different binary mixtures show that the number of transfer units can be expressed as a simple function of the inlet vapour state and flow rate, heat load, and channel geometry. The calculations also show that the vapour and liquid exit compositions tend to limiting values as the number of transfer units increase. These limiting values correspond to liquid leaving the exchanger in equilibrium with the vapour entering. The effect of surface tension on liquid running down the rectangular passages of plate-fin exchangers is to draw it to the corners leaving less liquid on the walls and possible dry-out. A comparison of two CFD calculations with and without surface tension shows that effect can be significant. For a liquid with a surface tension only 1% that of water, about 50% more mass flows down the corner region of a square duct of side 0.944 mm. This transfer of liquid to the corner takes place in the first millimetre of flow downwards. Experimental measurements of pressure drop were taken for air and air-water flow through eight different plate-fin pads. The two-phase pressure drops for the serrated fin were two to five times larger than those for the plain fin. However, the effect of increasing the water flow rate at a fixed air flow rate was to increase the pressure drop by up to 75% in both cases. Over 200 two-phase pressure drops measurements were made, nearly all of the data were predicted to within 20% by the Lockhart and Martinelli (1949) correlation with C factor of 12.

In this study the unique properties of microfluidic flow have been exploited to generate efficient mass-transfer in continuous segmented flow to investigate an alternative approach for performing chemical extractions. The concept of extraction-enhancement, by incorporation of a solid absorbent in the extracting phase, was explored. Proof-of-principle studies focused on the use of molecularly imprinted polymers (MIPs) to increase the effectiveness of conventional approaches. Laser machining and micro-milling were used to prepare PTFE microfluidic separation devices. Importantly, this included the design and integration of a continuous-flow microfluidic liquid phase separator. Propranolol selective molecularly imprinted polymer microspheres (3.6 µm) were prepared by precipitation polymerisation. MIP performance was assessed using conventional (equilibrium batch rebinding) and segmented-flow liquid-liquid systems. Interfacial mass transfer processes that occur during segmented flow were characterised with respect to flow variables, fluid properties and channel geometries. Segment aspect ratio and flow velocity, together with channel diameter and curvature, were shown to be important. The MIP was shown to possess high affinity and selectivity for the template (propranolol). Incorporation of the MIP into a segmented flow extraction regime was shown to significantly enhance the extent of analyte extraction. Mathematical optimisation approaches showed good correlation with experimental data. On-chip phase separation was demonstrated to be 100% efficient for particle-containing and particle-free immiscible flows. The discovery of soluble MIP species possessing similar binding characteristics to their insoluble counterparts may further improve the kinetics of the reported solid-liquid-liquid extractions. It was successfully demonstrated that a solid phase material can be incorporated into an organic phase to enhance extraction from an aqueous sample either in continuous segmented flow or under equilibrium conditions. The integration of the segmented flow approach with an on-chip liquid phase separator provides a novel platform for the development of unique and highly-efficient continuous flow devices for molecular enrichments, separations and manipulations.

Membrane based gas separations are proven to be technically attractive because of their simplicity and low energy costs, although they are often limited by insufficient flux, selectivity and stability. During the past thirty years, major developments in this technology have been made by developing high flux asymmetric membranes, and large surface area membrane modules. Today, in the present market, the sales of the membrane gas separation equipments have grown to become a $150 million per year business, and substantial growth in the near future is likely. More than 90% of membrane gas separation business involves the separation of non-condensable gases, i.e. nitrogen from air, carbon dioxide from methane, and hydrogen from nitrogen, argon, or methane. However, a large potential market for membrane gas separation lies in refineries. The separations of hydrogen/hydrocarbon and olefin/paraffin are regarded as import processes (although challenging ones) in the petrochemical industry. The membrane based separation p~ocess to sepfirate olefins from paraffins is likely to be developed to the commercial state in the next few years. Industry's demands for increasing the separation effectiveness and productivity have encouraged conducting research into development of new membrane materials. Polyaniline is regarded as so far the best alternative for gas separations, since the molecular spacing of polymer chains can be controlled by its interesting doping/dedoping chemistry. A novel method to make reproducible defect-free dense self-supported polyaniline films with the thicknesses between 2 and 6 IJm, and polyaniline nanofilm membranes with selective polyaniline layer thicknesses between 300 and 800 nm supported on a porous polyvinylidene fluoride (PVDF) substrate is developed. (Continues...).

The efficiency of membrane processes is very important to the profitability of organisations and the issue of membrane fouling, flux optimisation and selectivity and dependability are some of the drawbacks in membrane processes. Flux and selectivity problems usually arise as an increase in flux is usually followed by a decrease in the selectivity of the membrane, which is the degree of separation of contaminants. Laboratory assessments of membranes are required prior to a process application on an industrial scale to justify the nature of the membrane under certain conditions. Membrane fouling causes a decline in membrane efficiency and flux sustainability, in which performance is very high initially but then declines drastically as foulants accumulate on the membrane sUrface and ultimately within the pores. The use of turbulence promoters has been investigated in this study and its effects on flux sustainability are presented. The approach was to test two feed suspensions and determine the effects of the promoters on both systems. Regeneration methods were also used for the fouled membranes in order to re-use them for subsequent experiments. An experimental rig has been modified to house ceramic tubular membranes to monitor the filtration performance of the membranes. A literature review detailing the methods employed to control membrane fouling can be found in Chapter 2 of this thesis. The effects of operating parameters including system pressures, feed temperature, feed concentration and feed flow-rate were investigated to determine fouling effects over time. Artificial neural networks have also been utilised to correctly validate the existing experimental results generated from experimental work.

Proprietary evacuated tube solar water heaters (ETSWH) have superior thennal perfonnance in Northern Maritime climates compared with proprietary flat plate solar water heaters (FPSWHs). ETSWHs with heat pipe absorbers are especially suited for use in Northern Maritime climates due to their freeze tolerance and self-regulating heat transfer characteristics and ability to act as thennal diodes. Typically delivering 5-15% more thermal energy per annum, than FPSWHs, this is, however, achieved with higher capital costs. The adoption of thermosyphon fluid circulation compared with forced circulation systems allows the capital cost of solar water heating systems to be reduced, reliability increased and similar levels ofperfonnance to be achieved, for well designed systems. This thesis presents experimental data concerned with thermosyphon heat pipe ETSWHs operated under Northern maritime climatic conditions. It was determined that current proprietary designs of heat pipe ETSWHs originally designed for forced circulation can operate effectively when subjected to a Northern Maritime climate when thennosyphon ' fluid circulation is used instead. Though it was fo~nd that current designs are prone to diurnal reverse fluid flows which 'reduce diurnal efficiency by 11.5% Over the monitoring period from January 2007 to June 2007 it was calculated that predicted and measured solar fractions were within 2.5%. Simple payback periods and costs of the delivered energyare presented and discussed using collected and average meteorological data for the test site located at the Jordanstown campus(fthe University ofUlster. Natural convection within the manifold chamber was investigated through construction of physical models of the manifold chamber under investigation. Reverse thennosyphon fluid flows were recreated under laboratory conditions. Interactions between the pin-fin array within the manifold occurred and it was shown how these affected heat transfer within the manifold cavity. Two dimensional particle imaging velocimetry was used to visualise the thermosyphon fluid flow regime within the manifold chamber. The processed images validated the observations made by previous research that at the pin-fin diameter to spacing ratio used in proprietary heat pipe ETSWHs that locally heat transfer is degraded as the fluid travels through the cavity.

Adsorption is widely used for gas storage and separation for industrial and environmental applications. With appropriate adsorbents adsorption represents a low-energy alternative to conventional separation technologies. Hybrid organic-inorganic materials offer the ability to tailor the pore geometry as well as the surface chemistry, which are the two governing properties of an adsorbent with respect to its adsorption behaviour. Thus they enable the design of specific adsorbents for gas separation processes. By means of molecular simulation, the adsorption behaviour can be predicted prior to manufacturing the material, reducing the effort of designing and/or screening of adsorbents significantly. This work focuses on two groups of hybrid materials. On the one hand, we studied aluminium methylphosphonates which are crystalline, organic-inorganic microporous materials. They can exhibit molecular sieving effects and as they are crystalline the atomic co-ordinates, which are necessary to perform molecular simulations of the adsorption process, can be derived accurately from XRD studies. On the other hand, organically modified, non-crystalline periodic mesoporous silicas (PMSs) can be prepared with different pore geometries and their mesopores are sufficiently large to accommodate even large surface groups. We have developed new methods to generate atomic models for the amorphous wall structure of PMSs by means of computer simulation of their synthesis. This so called kinetic Monte Carlo simulation is presented in combination with Grand Canonical Monte Carlo simulation of adsorption as a tool in a design procedure for adsorbents for gas separation. The application of these design tools is demonstrated by designing an MCM-41-type hybrid adsorbent for the removal of carbon dioxide from power-plant flue gas, and by optimising the process conditions for the separation of air into nitrogen and oxygen using microporous A1MePO-α.

Scale formation on heat transfer surfaces results in the build-up of deposits (products of heat and mass transfer processes) which act as additional thermal resistance, thereby leading to the degradation of equipment heat transfer performance. Under most conditions fouling is more severe during sub-cooled boiling heat transfer, mainly due to the mechanisms which govern the bubble formation and detachment process. Therefore in response, the current project aims to investigate the boiling enhancement characteristics and fouling mitigation potential of a three-phase (vapour-liquid-solid) circulating fluidised bed heat exchanger (CFBHX). The design of the three-phase boiling system is predicated on a combination of multiphase fluidisation and flow boiling heat transfer. Experiments are performed at atmospheric pressure, and distilled water is used as the working fluid. The three-phase test unit consist of a glass riser column with a minichannel of square cross sectional area 21.5 mm x 11mm, height 1000mm, fitted with an electrically heated cartridge heater rod of 8mm diameter x 730mm length. The set-up employs stainless steel particles as the solid phase. A systematic experimental study is made to understand the influence of particles and particle size on the boiling heat transfer behaviour of the three-phase CFBHX. The effect of operating parameters such as heat flux and superficial velocity are also investigated. In the riser column, the use of transparent glass walls is of major significance as it provides a means of observing, and studying (via the use of flow visualisation techniques) the complex multiphase flow system. Results from our experimental work show that higher heat transfer coefficients are achieved in (vapour-liquid-solid) three-phase flow boiling, compared with (vapour-liquid) two-phase flow boiling. The observed enhancement becomes more pronounced for progressively larger diameter particles. Based on both an analysis of the mechanisms governing three-phase boiling heat transfer, and the extension of existing two-phase flow boiling (and liquid-solid fluidised bed) heat transfer models, a boiling heat transfer correlation has been derived for the prediction of heat transfer in our vapour-liquid-solid circulating fluidised bed system. A favourable agreement between the derived three-phase boiling correlation and our empirically obtained results has also been duly demonstrated.

Hybrid separation systems have recently been hailed as one of the most promising alternatives to conventional capital and energy intensive separation processes. Hybrid separation systems are able to effectively separate mixtures commonly encountered in the fine chemical and pharmaceutical industries that are difficult or impossible to separate by conventional distillation processes due to azeotropic behaviour or low relative volatilities. In a hybrid process where a distillation column unit and a pervaporation unit are integrated into one process, the shortcomings of one method are outweighed by the benefits of the other. The addition of a pervaporation unit to the conventional distillation process, either before, after or fully integrated, adds complexity to the system but also more degrees of freedom which, if properly chosen, can result in capital and operating costs savings and can consequently increase the overall profitability of the system, particularly for difficult separations. The objective of this work was to study the optimal configuration, design and operation of hybrid distillation/ membrane processes taking into account the extra degrees of freedom afforded by these processes. This is achieved by firstly developing detailed mathematical models from first principles to accurately describe the distillation, membrane and their hybrid processes. Secondly, rigorous optimisation strategies were employed to study the hybrid systems and their constituents processes. The feasibility of the hybrid system was investigated through various studies. In the first study, the batch configuration, design and operation of the hybrid system was considered for the first time. The second study considers the optimal synthesis of continuous hybrid processes where more degree of freedoms have been explored than previously reported. The third study considered the novel multi-criteria optimisation of these systems. It was demonstrated in these studies that significant savings can be achieved when the optimal hybrid process is used instead of distillation or pervaporation alone.

Experimental and theoretical methods have been used to study zeolite structures, properties and applications as membranes for separation purposes. Thin layers of silicalite-1 and Na-LTA zeolites have been synthesised onto carbon-graphite supports using a hydrothermal synthesis procedure. The separation behaviour of the composite membranes was characterized by gas permeation studies of pure, binary and ternary mixtures of methane, ethane and propane. The influence of temperature and feed gas mixture composition on the separation and selectivity performance of the membranes was also investigated. It was found that the silicalite-1 composite membranes synthesised onto the 4 hour oxidized carbon-graphite supports showed the most promising separation behaviour of all the composite membranes investigated. Molecular simulation methods were used to gain an understanding of how hydrocarbon molecules behave both within the pores and on the surfaces of silicalite-1, mordenite and LTA zeolites. Molecular dynamic simulations were used to investigate the influence of temperature and molecular loadings on the diffusional behaviour of hydrocarbons in zeolites. Both hydroxylated (surface termination with hydroxyl groups) and non-hydroxylated silicalite-1 and Na-mordenite surfaces were generated. For both zeolites the most stable surfaces correspond to the {010} surface. For the silicalite-1 {010} surface the adsorption of hydrocarbons and molecular water onto the hydroxylated surface showed a favourable exothermic adsorption process compared to adsorption on the non-hydroxylated surface. With the Na-mordenite {010} surface the adsorption of hydrocarbons onto both the hydroxylated and non-hydroxylated surfaces had a combination of favourable and non-favourable adsorption energies, while the adsorption of molecular water onto both types of surface was found to be a favourable adsorption process.