125 results on '"Edwards PP"'
Search Results
2. Microwave-initiated catalytic deconstruction of plastic 2 waste into hydrogen and high-value carbon
- Author
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Jie, X, Li, W, Slocombe,D, Gao, Y, Banerjee, I, Gonzalez-Cortes, S, Yao, B, Almegren, H, Alshihri, S, Dilworth, J, Thomas, JM, Xiao, T, and Edwards, PP
- Abstract
The ubiquitous challenge of plastic waste has led to the modern descriptor plastisphere to represent the human-made plastic environment and ecosystem. Here we report a straightforward rapid method for the catalytic deconstruction of various plastic feedstocks into hydrogen and high-value carbons. We use microwaves together with abundant and inexpensive iron-based catalysts as microwave susceptors to initiate the catalytic deconstruction process. The one-step process typically takes 30–90 s to transform a sample of mechanically pulverized commercial plastic into hydrogen and (predominantly) multiwalled carbon nanotubes. A high hydrogen yield of 55.6 mmol g–1plastic is achieved, with over 97% of the theoretical mass of hydrogen being extracted from the deconstructed plastic. The approach is demonstrated on widely used, real-world plastic waste. This proof-of-concept advance highlights the potential of plastic waste itself as a valuable energy feedstock for the production of hydrogen and high-value carbon materials.
- Published
- 2020
3. Future energy materials: Transparent conductors and super conductors
- Author
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Edwards, PP
- Published
- 2016
4. Metallization of fluid hydrogen - Discussion
- Author
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Johnston, RL, Nellis, WJ, Rao, CNR, Tunstall, DP, von Lohneysen, H, Edwards, PP, and Logan, DE
- Published
- 2016
5. Bismuth oxyhalide visible-light-driven BiOBrxI1-x solid solutions: Essences for the highly efficient photocatalyst
- Author
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Kong, L, Jiang, Z, Lai, HHC, Makepeace, J, Xiao, T, and Edwards, PP
- Published
- 2016
6. Fluorination of underdoped mercurocuprate superconductors
- Author
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Peacock, GB, Fletcher, A, Slaski, M, Gameson, I, Capponi, JJ, and Edwards, PP
- Subjects
Condensed Matter::Superconductivity ,Physics::Chemical Physics - Abstract
We present the results of a study into the incorporation of fluorine into the mercurocuprate superconductors. In all cases, the effect of fluorination has been to increase the Tc of underdoped superconductors to the maxima reported. This has important ramifications for the role of the interstitial oxygen in the mercurocuprate superconductors. To assist us in our study, we have, additionally, developed a novel synthetic procedure for preparing HgBa2CuO4+δ in a highly underdoped state. Remarkably, this material shows an increase in Tc, upon fluorination, of 60K! © 1998 Plenum Publishing Corporation.
- Published
- 2016
7. Do alkali metal anions (M(-)) exist in zeolite A?
- Author
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Barker, PD, Anderson, PA, Dupree, R, Kitchin, S, Edwards, PP, and Woodall, LJ
- Abstract
Recent NMR studies by Nakayama et al. on sodium zeolite A saturated with potassium metal have implied the presence of the anionic Na- species. This, if confirmed, would represent the first observation in a zeolite and opens up a wide range of possibilities for mixed metal zeolitic systems. We report the results of a number of metal combinations, using both sodium and potassium forms of zeolite A as hosts, studied by ESR, solid state MAS-NMR and powder neutron diffraction.
- Published
- 2016
8. Synthesis, structure, and XPS characterization of the stoichiometric phase Sr2CuO2F2
- Author
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Kissick, JL, Greaves, C, Edwards, PP, Cherkashenko, VM, Kurmaev, EZ, Bartkowski, S, and Neumann, M
- Abstract
Thermogravimetric analysis has revealed that reduction of Sr2CuO2F2+δ in 10% H2/90% N2, occurs in two distinct steps on heating up to 930 °C. Whereas reduction to give SrF2, SrO, and Cu is complete above 800 °C, a stable intermediate forms in the region between 250 and 450 °C. This has been identified as a new tetragonal (I4/mmm) phase, Sr2CuO2F2, with unit-cell dimensions a = 3.967(1) Å and c= 12.816(2) Å. The structure has been determined from powder x-ray-diffraction data and is related to Nd2CuO4 (T′'-type). Madelung energy, bond valence sum calculations, and F 1 s-XPS data clearly indicate that the F- ions occupy sites within the fluorite block (Sr2F2) insulating layers. This contrasts with the La2CuO4 (T-type) structure which is adopted by Sr2CuO2F2+δ-.
- Published
- 2016
9. Experimental and density-functional study of the electronic structure of In4Sn3O12
- Author
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O'Neil, DH, Walsh, A, Jacobs, RMJ, Kuznetsov, VL, Egdell, RG, and Edwards, PP
- Abstract
The electronic structure of In4 Sn3 O12 has been studied by optical and x-ray photoemission spectroscopies and has been compared to electronic structure calculations carried out using density-functional theory. An excellent agreement is found between the experimental valence-band structure and that predicted by the calculations. The valence band derives its dominant character from O2p states with three distinct features emerging from the hybridization with In and Sn5s, 5p, and 4d states, respectively. The position of the valence-band edge in the x-ray photoemission spectrum suggests a fundamental electronic gap of 2.7 eV whereas the onset of strong optical absorption is predicted to occur at 3.3 eV. © 2010 The American Physical Society.
- Published
- 2016
10. Nitrogen-doped TiO(2) Nano-crystal Colloid: A printable 'Ink' for potential Solar Energy Devices
- Author
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Jiang, Z, Shi, H, Yang, G, Xiao, T, Jones, MO, and Edwards, PP
- Published
- 2016
11. The metal-non-metal transition in macroscopic and microscopic systems - Preface
- Author
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Edwards, PP, Johnston, RL, Rao, CNR, and Tunstall, DP
- Published
- 2016
12. The structure, characterization, and evolution of colloidal metals
- Author
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Kirkland, AI, Edwards, PP, Jefferson, DA, and Duff, DG
- Published
- 2016
13. Electron-energy-loss studies of core edges in (Tl0.5Pb0.5)(Ca1-xYx)Sr2Cu2O7- delta
- Author
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Yuan, J, Brown, LM, Liang, WY, Liu, RS, and Edwards, PP
- Published
- 2016
14. Anisotropic magnetic penetration depth of grain-aligned HgBa2Ca2Cu3O8+ delta
- Author
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Panagopoulos, C, Cooper, JR, Peacock, GB, Gameson, I, Edwards, PP, Schmidbauer, W, and Hodby, JW
- Subjects
Condensed Matter::Superconductivity - Abstract
The temperature (T) dependence of the anisotropic magnetic penetration depth Λ(T) of magnetically aligned powders of crystalline HgBa2Ca2Cu3O8+δ is reported. Measurements were performed in the Meissner state using the ac-susceptibility technique. The temperature dependences of the in-plane, Λab(T), and out-of-plane, Λc(T), penetration depths are markedly different. This is believed to arise from the large anisotropy ratio γ=[Λc(0)/Λab(0)]≃30. The behavior of Λab(T) is indicative of d-wave superconductivity while Λc(T) is similar to the behavior expected for a superconductor with intrinsic Josephson coupling between the CuO2 planes. Similar measurements were performed on Ba0.6K0.4BiO3 powders for comparison.
- Published
- 2016
15. Chemistry of superconducting oxides
- Author
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Armstrong, AR and Edwards, PP
- Published
- 2016
16. Crystal chemistry of hydrogen storage materials
- Author
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Jones, MO, David, WIF, Johnson, SR, Sommariva, M, Lowton, RL, Nickels, EA, and Edwards, PP
- Abstract
We review here work on two classes of compounds that have been promoted as potential hydrogen storage materials; alkali metal amides and borohydrides, highlighting how their crystal structure and chemical properties may be used to influence the key hydrogen absorption and desorption parameters in these materials. © 2008 Materials Research Society.
- Published
- 2016
17. Synthesis and structure of Hg1-xCrxSr2CuO4+delta mercurocuprates
- Author
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Hyatt, NC, Jones, MO, Gameson, I, Slaski, M, Peacock, GB, Hriljac, JA, and Edwards, PP
- Abstract
We report preliminary results concerning the synthesis and structural characterisation of the chromium stabilised 1201 phases: Hg1-xCrxSr2CuO4+δ. A systematic study of the formation of phases in this system has been undertaken, together with a combined powder neutron and synchrotron x-ray diffraction study, to address the issue of chromium clustering and ordering in this system. © 1998 Plenum Publishing Corporation.
- Published
- 2016
18. Re-induced Raman active modes in HgBa2Can-1CunO2n+2+delta compounds
- Author
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Poulakis, N, Lampakis, D, Liarokapis, E, Yoshikawa, A, Shimoyama, J, Kishio, K, Peacock, GB, Hodges, JP, Gameson, I, Edwards, PP, and Panagopoulos, C
- Abstract
A comparative Raman study of Re-free and Re-doped HgBa2Can-1CunO2n+2+δ with n=1,3,4,5 is presented in an attempt to further clarify the structural and phononic modifications brought about by Re substitution. A number of extra high-frequency phonon peaks show up in the spectra of the Re-doped samples and are attributed to the oxygen modes of a strongly bound, almost decoupled ReO6 octahedron. As regards the apex oxygen in the Hg site, a clear transfer of spectral weight from the 590 to the 570 cm-1 apex phonon band is observed upon Re substitution. Such a change may well be accounted for assuming increased excess oxygen content for the Re-doped samples. Another interesting result is the enhancement upon Re doping of a narrow peak probably attributed to c-axis vibrations of Ba whose frequency shows a distinctive change with the number n of the CuO2 layers, providing an easy way to identify the various phases in a sample. ©1999 The American Physical Society.
- Published
- 2016
19. Microstructure of laser-ablated La(2)CnO(4)F(x) thin films on SrTiO3
- Author
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Kong, G, Aindow, M, Jones, MO, Gameson, I, Lees, ST, Gibbons, KE, Abell, JS, and Edwards, PP
- Published
- 2016
20. The mechanism of surface decomposition of Tl- and Hg-containing superconductors
- Author
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Zhou, W, Jefferson, DA, Liang, WY, Peacock, GB, Asab, A, Gameson, I, and Edwards, PP
- Abstract
The surface chemistry of various Tl- and Hg-containing superconducting oxides has been studied by high resolution transmission electron microscopy. The mechanism of surface decomposition of these materials is discussed. High chemical reactivity of the Tl-O and Hg-O layers seem to be the main course of the decomposition. It is proposed that a surface substitution of Tl and Hg may stabilise the structures without losing superconducting properties. © 1998 Plenum Publishing Corporation.
- Published
- 2016
21. Mott insulator high T-c bipolaronic superconductor transition in cuprates - Discussion
- Author
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Edwards, PP, Alexandrov, AS, Ramakrishnan, TV, and McGreevy, R
- Published
- 2016
22. High-pressure neutron diffraction study of the quasi-one-dimensional cuprate Sr2CuO3
- Author
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Hyatt, NC, Gray, L, Gameson, I, Edwards, PP, and Hull, S
- Abstract
The crystal structure of the quasi-one-dimensional cuprate Sr 2CuO3 has been studied under high pressure using neutron powder diffraction methods. Full structure refinements were undertaken, using the Rietveld method, with data acquired between room pressure and 0.55(1) GPa at room temperature. The compressibility of Sr2CuO3 is anisotropic, a consequence of the ordered nature of the anion vacancies in this material. The effect of high pressure and chemical substitution on the crystal structure of the Sr2-xCaxCuO3 system is discussed and it is suggested that the substitution of Sr2+ by Ca2+ may constitute a "chemical pressure" effect in this solid solution. The availability of accurate bond length compressibility data for Sr2CuO3 may now allow an appraisal of the effect of applied pressure on the remarkable electronic properties of this material, through appropriate band structure calculations.
- Published
- 2016
23. Amidoboranes for hydrogen storage
- Author
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David, WIF, Jones, MO, and Edwards, PP
- Published
- 2016
24. Chemistry. Electrons in cement
- Author
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Edwards, PP
- Abstract
A system of stabilized solvated electrons has been realized in a new type of inorganic electride.
- Published
- 2016
25. The Transition to the Metallic State in Polycrystalline n-type Doped ZnO Thin Films
- Author
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Vai, AT, Kuznetsov, VL, Jain, H, Slocombe, D, Rashidi, N, Pepper, M, and Edwards, PP
- Abstract
We report a detailed investigation of the charge carrier transport in polycrystalline n-type impurity-doped zinc oxide (ZnO) thin films grown by spray pyrolysis over a wide range of carrier concentrations. Particular attention is devoted to a study of the composition-dependent metal-insulator transition (MIT) in this transparent conducting oxide (TCO). In order to describe the flow of electrons in these impurity-doped thin films over this full range of conditions, it is necessary to consider multiple electronic conduction processes. The first conduction process arises from current carriers thermally excited from impurity states into the (host) ZnO conduction band. The second involves thermally-activated, quantum-mechanical tunnelling within an impurity band located close to the host conduction band. The latter conduction process predominates at low temperatures whilst the former dominates at high temperatures. We find that a MIT occurs at a critical carrier concentration between 2 and 6×1019 cm-3. At higher concentrations in this metallic regime, the impurity band merges with the ZnO conduction band. The location of the MIT was determined from low temperature resistivity data and the results are discussed in terms of the Mott and Ioffe-Regel models. In addition, the overriding importance of grain boundaries is highlighted for these polycrystalline thin films; this is a key factor in determining and limiting electronic conduction in these samples, particularly at high temperatures. These results highlight the practical importance of understanding both the MIT and also grain boundary effects in determining the electrical performance of polycrystalline TCO films. Copyright © 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.
- Published
- 2014
26. Probing the order parameter and the c-axis coupling of high Tc cuprates by penetration depth measurements
- Author
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Panagopoulos, C, Cooper, JR, Xiang, T, Peacock, GB, Gameson, I, and Edwards, PP
- Abstract
We have measured the low-temperature (T) dependence of the anisotropic penetration depth λ(T) of magnetically aligned powders of HgBa2Can-1CunO2n+2+δ (n = 1 and 3) down to 1.2 K. For both members the T dependence of the in-plane penetration depth λab(T) is strongly linear, whereas the out-of-plane component λc(T), for n = 1 and 3, varies as T5 and T2, respectively. For comparison, we also report λc(T) data for grain-aligned YBa2Cu3O7-δ (δ = 0.0 and 0.43) which vary as T and T2, respectively. The results are discussed in terms of dx2-y2wave symmetry of the order parameter in cuprates.
- Published
- 1997
27. Titanium nuclear magnetic resonance in metallic superconducting lithium titanate and its lithium-substituted derivatives Li1+xTi2-xO4 (0<x<0.10)
- Author
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Tunstall, DP, Todd, JR, Arumugam, S, Dai, G, Dalton, M, and Edwards, PP
- Published
- 1994
28. NMR studies in the superconducting spinel system Li1+xTi2−xO4
- Author
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Dalton, M, primary, Tunstall, DP, additional, Todd, J., additional, Arumugam, S, additional, and Edwards, PP, additional
- Published
- 1994
- Full Text
- View/download PDF
29. Granular effects in superconducting YBa2Cu4O8 ceramic
- Author
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Lin, SY, primary, Liu, RS, additional, Zheng, DN, additional, Liang, WY, additional, and Edwards, PP, additional
- Published
- 1991
- Full Text
- View/download PDF
30. General discussion
- Author
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Howie, A, Buffat, PA, Masson, A, Thomas, JM, Bernholc, J, Joyner, RW, Gallezot, P, Rao, CNR, Creighton, JA, Johnson, BFG, Hofmeister, H, Harris, PJF, Bradley, JS, Kuroda, H, Zamaraev, KI, Couves, JW, Greenslade, DJ, Edwards, PP, Mulvaney, P, Stace, AJ, Mile, B, Leadbetter, AJ, Duncan, MA, Landsman, DA, Henglein, A, Matijević, E, Stone, FS, Simons, JP, Bradshaw, AM, Miessner, H, Kappers, M, and Eadon, D
- Subjects
Physical and Theoretical Chemistry - Published
- 1991
31. ESR study of the quasi one-dimensional cuprate (Ca1-xYx)(0.82)CuO2
- Author
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Yuzuru Miyazaki, Hyatt, Nc, Anderson, Pa, and Edwards, Pp
32. Microwave-initiated catalytic dehydrogenation of fossil fuels for the facile production and safe storage of hydrogen
- Author
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Jie, X, Edwards, PP, and Compton, RG
- Abstract
Hydrogen offers the prospect of a highly effective fuel for future sustainable energy, not only because of its intensive energy density per unit-mass but also because its combustion produces no environmentally damaging CO2 at its point-of-use. Hydrogen is presently manufactured on an industrial scale by steam reforming or partial oxidation of methane and to a lesser degree by gasification of coal. However, these processes also generate significant quantities of CO2, with obvious attendant environmental problems. The utilisation of solar energy now yields increasing amounts of hydrogen by the splitting of water, as does the harnessing of other sources of natural energy. But even if the photocatalytic or electrolytic breakdown of water could be greatly improved to produce the necessary huge quantities of hydrogen, the resulting challenge of its safe storage and rapid release for immediate use in fuel cells, for example, is problematic. An alternative platform is to utilise the high intrinsic hydrogen content of fossil fuel hydrocarbons but in such a way as to rapidly release only their constituent hydrogen without any CO2 production. Such CO2-free hydrogen production from hydrocarbons has been advanced through pioneering studies on the catalytic thermolysis of methane and petroleum-range hydrocarbons. My doctoral research work centres on a method of rapidly liberating high-purity hydrogen from hydrocarbons without CO2 emission. An innovative system combining microwave technology and heterogeneous catalysis is thus proposed. As a result, a H2 production selectivity from all evolved gases of some 98%, is achieved with less than a fraction of a percent of adventitious CO and CO2 through the microwave-initiated catalytic dehydrogenation of liquid alkanes using Fe and Ni particles supported on silicon carbide. In this doctoral work, the complex interaction between the heterogeneous catalyst system and the induced microwave electric field was carefully studied by scanning a variety of metals and supports. Consequently, the optimised catalyst system was developed in effectively response to the microwave irradiation. Another enthusiastic and exciting part of the work is that a variety of actual, real petroleum products, ranging from heavy crude oil, crude oil through diesel, petrol to natural gas (methane) have been demonstrated that can be the vehicle for high-purity hydrogen production through the microwave-initiated catalytic dehydrogenation. Based on this work, we showed that the undoubted attractive attributes of fossil fuels - relatively inexpensive, widely available and readily adaptable to applications large and small, simple and complex, - can significantly assist in the staged transition to a hydrogen-based, sustainable hydrogen energy economy. A new scientific and technological era of “Fossil fuel decarbonisation" can arise where we will not destroy naturally-occurring fossil fuels by combustion – with the attendant CO2 emissions, but rather utilise them to produce clean hydrogen. Carbonaceous fossil fuels are thereby transformed from carbon-rich to hydrogen-rich fuels for future energy.
- Published
- 2020
33. Computational modelling of structure and dynamics in lightweight hydrides
- Author
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Aeberhard, PC, David, WIF, and Edwards, PP
- Subjects
Computer aided molecular and material design ,Computational chemistry ,Crystallography ,Hydrogen Storage ,Condensed Matter Physics ,Inorganic chemistry - Abstract
Hydrogen storage in lightweight hydrides continues to attract significant interest as the lack of a safe and efficient storage of hydrogen remains the major technological barrier to the widespread use of hydrogen as a fuel. The metal borohydrides Ca(BH₄)₂ and LiBH₄ form the subject of this thesis; three aspects of considerable academic interest were investigated by density functional theory (DFT) and molecular dynamics (MD) modelling. (i) High-pressure crystal structures of Ca(BH₄)₂ were predicted from a structural analogy between metal borohydrides and isoelectronic metal oxides. The structural stability of hydrogen storage materials under high pressure is an important aspect, as high-pressure polymorphs may provide structures with better hydrogen desorption properties. The isoelectronic analogue of Ca(BH₄)₂ is TiO₂, and structural equivalents of Ca(BH₄)₂ in the baddeleyite, columbite and cotunnite structures of TiO₂ were found to be stable at elevated pressure. Thermodynamic stability was evaluated by computing the Gibbs energy with respect to pressure and temperature. The pressure-dependence of the Helmholtz energy was determined to described a third-order Birch-Murnaghan equation of state, and the harmonic approximation was used to compute the vibrational energy levels and the Helmholtz energy as a function of temperature. The proposed structures are consistent with reports of two hitherto unidentified high-pressure phases observed experimentally. (ii) The disordered structure of the high-temperature phase of LiBH4 was studied by ab initio molecular dynamics (MD) at temperatures ranging from 200-535 K. It was found that the model emerging from analysis of the MD simulations properly accounts for dynamical disorder and fundamentally differs from the published experimental and theoretical structures. The validity of the MD model was corroborated by comparison of calculated pair distribution functions, vibrational spectra and a crystallographic model with neutron diffraction data; good agreement was found. A reassignment of the space group from P63mc to P63/mmc is proposed based on evidence for additional symmetry from MD simulations. (iii) Finally, a new MD-based method was developed to simulate fast ionic diffusion in LiBH₄. The colour diffusion algorithm - a nonequilibrium molecular dynamics method originally developed for the study of model fluids - was adapted and applied to self-diffusion of atoms in a solid for the first time. Calculated diffusion coefficients agreed very well with published measurements, and diffusion pathways that include collective particle effects were determined directly from the simulation results, thereby opening up a promising and efficient new method for the study of phenomena such as superionic conduction.
- Published
- 2016
34. p-block hydrogen storage materials
- Author
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Christopher Ian Smith, Edwards, PP, and David, WIF
- Subjects
Structural chemistry ,Chemical crystallography ,Crystallography ,Hydrogen Storage ,Materials Sciences ,Surface chemistry ,Physical & theoretical chemistry ,Catalysis ,Inorganic chemistry ,Solid state chemistry - Abstract
The development of a clean hydrogen economy will aid a smooth transition from fossil fuels which is required to stem the environmental impact and economic instability caused by oil dependency. For vehicular application, in addition to being cheap and safe, a commercial hydrogen store must contain a certain weight percentage of hydrogen to provide a reasonable range (~300 miles). It must also be able to release hydrogen under near-ambient conditions (80-120°C) and have a reasonable cycling capacity (~1000 cycles). The primary motivation of this thesis is to gain a fundamental understanding into the sorption processes of hydrogen on carbon- and aluminium-based materials to improve their hydrogen storage capacity. The sorption processes of hydrogen on mechanically milled graphite have been investigated, primarily using Electron Spin Resonance Spectroscopy and Inelastic Neutron Scattering. An investigation into the storage properties of tetrahydroaluminates, primarily NaAlH4 and LiAlH4, is performed in the presence and absence of a catalyst, and a new phase of NaAlH4 is observed prior to its decomposition. Variable temperature neutron and synchrotron diffraction, in conjunction with gravimetric and mass spectroscopy data were obtained for several mixtures of tetrahydroaluminates and alkali amides and the hydrogen desorption processes are shown to be quite different from the constituent materials. The structure of Ca(AlH4)2 has been experimentally determined for the first time and a complete set of equations describing its decomposition pathway is given.
- Published
- 2016
35. A review of catalytic hydrogenation of carbon dioxide: From waste to hydrocarbons.
- Author
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Cui L, Liu C, Yao B, Edwards PP, Xiao T, and Cao F
- Abstract
With the rapid development of industrial society and humankind's prosperity, the growing demands of global energy, mainly based on the combustion of hydrocarbon fossil fuels, has become one of the most severe challenges all over the world. It is estimated that fossil fuel consumption continues to grow with an annual increase rate of 1.3%, which has seriously affected the natural environment through the emission of greenhouse gases, most notably carbon dioxide (CO
2 ). Given these recognized environmental concerns, it is imperative to develop clean technologies for converting captured CO2 to high-valued chemicals, one of which is value-added hydrocarbons. In this article, environmental effects due to CO2 emission are discussed and various routes for CO2 hydrogenation to hydrocarbons including light olefins, fuel oils (gasoline and jet fuel), and aromatics are comprehensively elaborated. Our emphasis is on catalyst development. In addition, we present an outlook that summarizes the research challenges and opportunities associated with the hydrogenation of CO2 to hydrocarbon products., (Copyright © 2022 Cui, Liu, Yao, Edwards, Xiao and Cao.)- Published
- 2022
- Full Text
- View/download PDF
36. Size-Dependent Microwave Heating and Catalytic Activity of Fine Iron Particles in the Deep Dehydrogenation of Hexadecane.
- Author
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Jie X, Chen R, Biddle T, Slocombe DR, Dilworth JR, Xiao T, and Edwards PP
- Abstract
Knowledge of the electromagnetic microwave radiation-solid matter interaction and ensuing mechanisms at active catalytic sites will enable a deeper understanding of microwave-initiated chemical interactions and processes, and will lead to further optimization of this class of heterogeneous catalysis. Here, we study the fundamental mechanism of the interaction between microwave radiation and solid Fe catalysts and the deep dehydrogenation of a model hydrocarbon, hexadecane. We find that the size-dependent electronic transition of particulate Fe metal from a microwave "reflector" to a microwave "absorber" lies at the heart of efficient metal catalysis in these heterogeneous processes. In this regard, the optimal particle size of a Fe metal catalyst for highly effective microwave-initiated dehydrogenation reactions is approximately 80-120 nm, and the catalytic performance is strongly dependent on the ratio of the mean radius of Fe particles to the microwave skin depth ( r /δ) at the operating frequency. Importantly, the particle size of selected Fe catalysts will ultimately affect the basic heating properties of the catalysts and decisively influence their catalytic performance under microwave initiation. In addition, we have found that when two or more materials-present as a mechanical mixture-are simultaneously exposed to microwave irradiation, each constituent material will respond to the microwaves independently. Thus, the interaction between the two materials has been found to have synergistic effects, subsequently contributing to heating and improving the overall catalytic performance., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)
- Published
- 2022
- Full Text
- View/download PDF
37. Sustainable chemical processing of flowing wastewater through microwave energy.
- Author
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Siddique F, Mirzaei A, Gonzalez-Cortes S, Slocombe D, Al-Megren HA, Xiao T, Rafiq MA, and Edwards PP
- Subjects
- Catalysis, Iron, Microwaves, Wastewater, Water Pollutants, Chemical
- Abstract
Iron oxide nanostructured catalysts have emerged as potential candidates for efficient energy conversion and electrochemical energy storage devices. However, synthesis and design of nanomaterial plays a key role in its performance and efficiency. Herein, we describe a one-pot solution combustion synthesis (SCS) of α-Fe
2 O3 with glycine as a fuel, and a subsequent reduction step to produce iron-containing catalysts (i.e., Fe3 O4 , Fe-Fe3 O4 , and Fe0 ). The synthesized iron-based nanoparticles were investigated for methyl orange (MO) degradation through Microwave (MW) energy under continuous flow conditions. Fe-Fe3 O4 showed higher MO degradation efficiency than α-Fe2 O3 , Fe3 O4 and Fe0 at low absorbed MW power (i.e. 5-80 W). The enhanced degradation efficiency is associated to the combination of higher availability of electron density and higher heating effect under MW energy. Investigation of dielectric properties showed relative dielectric loss of Fe3 O4 , Fe-Fe3 O4 , and Fe0 as 3847, 2010, and 1952, respectively. The calculated average local temperature by the comparative analysis of MW treatment with conventional thermal (CT) treatment showed a marked thermal effect of MW-initiated MO degradation. This work highlights the potential of microwave-driven water depollution under continuous-flow processing conditions and demonstrates the positive impact that earth-abundant Fe catalyst synthesized by green SCS method can have over the treatment of wastewater., (Copyright © 2021 Elsevier Ltd. All rights reserved.)- Published
- 2022
- Full Text
- View/download PDF
38. Catalytic Activity of Various Carbons during the Microwave-Initiated Deep Dehydrogenation of Hexadecane.
- Author
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Jie X, Wang J, Gonzalez-Cortes S, Yao B, Li W, Gao Y, Dilworth JR, Xiao T, and Edwards PP
- Abstract
Carbon materials have been widely used as microwave susceptors in many chemical processes because they are highly effective at transforming incoming electromagnetic energy for local (hot spot) heating. This property raises the intriguing possibility of using the all-pervasive carbonaceous deposits in operating heterogeneous catalytic processes to augment the catalytic performance of microwave-initiated reactions. Here, the catalytic activities of a range of carbon materials, together with carbon residues produced from a "test" reaction-the dehydrogenation of hexadecane under microwave-initiated heterogeneous catalytic processes, have been investigated. Despite the excellent microwave absorption properties observed among these various carbons, only activated carbons and graphene nanoplatelets were found to be highly effective for the microwave-initiated dehydrogenation of hexadecane. During the dehydrogenation of hexadecane on a Fe/SiC catalyst, active carbon species were formed at the early stage of the reactions but were subsequently transformed into filamentous but catalytically inert carbons that ultimately deactivated the operating catalyst., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)
- Published
- 2021
- Full Text
- View/download PDF
39. Superalkali-Alkalide Interactions and Ion Pairing in Low-Polarity Solvents.
- Author
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Riedel R, Seel AG, Malko D, Miller DP, Sperling BT, Choi H, Headen TF, Zurek E, Porch A, Kucernak A, Pyper NC, Edwards PP, and Barrett AGM
- Abstract
The nature of anionic alkali metals in solution is traditionally thought to be "gaslike" and unperturbed. In contrast to this noninteracting picture, we present experimental and computational data herein that support ion pairing in alkalide solutions. Concentration dependent ionic conductivity, dielectric spectroscopy, and neutron scattering results are consistent with the presence of superalkali-alkalide ion pairs in solution, whose stability and properties have been further investigated by DFT calculations. Our temperature dependent alkali metal NMR measurements reveal that the dynamics of the alkalide species is both reversible and thermally activated suggesting a complicated exchange process for the ion paired species. The results of this study go beyond a picture of alkalides being a "gaslike" anion in solution and highlight the significance of the interaction of the alkalide with its complex countercation (superalkali).
- Published
- 2021
- Full Text
- View/download PDF
40. Transforming carbon dioxide into jet fuel using an organic combustion-synthesized Fe-Mn-K catalyst.
- Author
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Yao B, Xiao T, Makgae OA, Jie X, Gonzalez-Cortes S, Guan S, Kirkland AI, Dilworth JR, Al-Megren HA, Alshihri SM, Dobson PJ, Owen GP, Thomas JM, and Edwards PP
- Abstract
With mounting concerns over climate change, the utilisation or conversion of carbon dioxide into sustainable, synthetic hydrocarbons fuels, most notably for transportation purposes, continues to attract worldwide interest. This is particularly true in the search for sustainable or renewable aviation fuels. These offer considerable potential since, instead of consuming fossil crude oil, the fuels are produced from carbon dioxide using sustainable renewable hydrogen and energy. We report here a synthetic protocol to the fixation of carbon dioxide by converting it directly into aviation jet fuel using novel, inexpensive iron-based catalysts. We prepare the Fe-Mn-K catalyst by the so-called Organic Combustion Method, and the catalyst shows a carbon dioxide conversion through hydrogenation to hydrocarbons in the aviation jet fuel range of 38.2%, with a yield of 17.2%, and a selectivity of 47.8%, and with an attendant low carbon monoxide (5.6%) and methane selectivity (10.4%). The conversion reaction also produces light olefins ethylene, propylene, and butenes, totalling a yield of 8.7%, which are important raw materials for the petrochemical industry and are presently also only obtained from fossil crude oil. As this carbon dioxide is extracted from air, and re-emitted from jet fuels when combusted in flight, the overall effect is a carbon-neutral fuel. This contrasts with jet fuels produced from hydrocarbon fossil sources where the combustion process unlocks the fossil carbon and places it into the atmosphere, in longevity, as aerial carbon - carbon dioxide.
- Published
- 2020
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41. Decarbonising energy: The developing international activity in hydrogen technologies and fuel cells.
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Thomas JM, Edwards PP, Dobson PJ, and Owen GP
- Abstract
Hydrogen technologies and fuel cells offer an alternative and improved solution for a decarbonised energy future. Fuel cells are electrochemical converters; transforming hydrogen (or energy sources containing hydrogen) and oxygen directly into electricity. The hydrogen fuel cell, invented in 1839, permits the generation of electrical energy with high efficiency through a non-combustion, electrochemical process and, importantly, without the emission of CO
2 at its point of use. Hitherto, despite numerous efforts to exploit the obvious attractions of hydrogen technologies and hydrogen fuel cells, various challenges have been encountered, some of which are reviewed here. Now, however, given the exigent need to urgently seek low-carbon paths for humankind's energy future, numerous countries are advancing the deployment of hydrogen technologies and hydrogen fuel cells not only for transport, but also as a means of the storage of excess renewable energy from, for example, wind and solar farms. Furthermore, hydrogen is also being blended into the natural gas supplies used in domestic heating and targeted in the decarbonisation of critical, large-scale industrial processes such as steel making. We briefly review specific examples in countries such as Japan, South Korea and the People's Republic of China, as well as selected examples from Europe and North America in the utilization of hydrogen technologies and hydrogen fuel cells., (© 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.)- Published
- 2020
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42. The periodic law of the chemical elements: ' The new system of atomic weights which renders evident the analogies which exist between bodies ' [1].
- Author
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Edwards PP, Egdell RG, Fenske D, and Yao B
- Abstract
The historical roots, the discovery and the modern relevance of Dmitri Mendeleev's remarkable advance have been the subject of numerous scholarly works. Here, with a brief overview, we hope to provide a link into the contents of this special issue honouring the great scientist. Mendeleev's advance, announced in March 1869, as he put it in 1889, to the '… then youthful Russian Chemical Society… ', first set out the very basis of the periodic law of the chemical elements, the natural relation between the properties of the elements and their atomic weights. This was, and still is, the centrepiece of a historical journey for chemistry to today's position as a pre-eminent science. This article is part of the theme issue 'Mendeleev and the periodic table'.
- Published
- 2020
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43. Metals and non-metals in the periodic table.
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Yao B, Kuznetsov VL, Xiao T, Slocombe DR, Rao CNR, Hensel F, and Edwards PP
- Abstract
The demarcation of the chemical elements into metals and non-metals dates back to the dawn of Dmitri Mendeleev's construction of the periodic table; it still represents the cornerstone of our view of modern chemistry. In this contribution, a particular emphasis will be attached to the question 'Why do the chemical elements of the periodic table exist either as metals or non-metals under ambient conditions?' This is perhaps most apparent in the p-block of the periodic table where one sees an almost-diagonal line separating metals and non-metals. The first searching, quantum-mechanical considerations of this question were put forward by Hund in 1934. Interestingly, the very first discussion of the problem-in fact, a pre-quantum-mechanical approach-was made earlier, by Goldhammer in 1913 and Herzfeld in 1927. Their simple rationalization, in terms of atomic properties which confer metallic or non-metallic status to elements across the periodic table, leads to what is commonly called the Goldhammer-Herzfeld criterion for metallization. For a variety of undoubtedly complex reasons, the Goldhammer-Herzfeld theory lay dormant for close to half a century. However, since that time the criterion has been repeatedly applied, with great success, to many systems and materials exhibiting non-metal to metal transitions in order to predict, and understand, the precise conditions for metallization. Here, we review the application of Goldhammer-Herzfeld theory to the question of the metallic versus non-metallic status of chemical elements within the periodic system. A link between that theory and the work of Sir Nevill Mott on the metal-non-metal transition is also highlighted. The application of the 'simple', but highly effective Goldhammer-Herzfeld and Mott criteria, reveal when a chemical element of the periodic table will behave as a metal, and when it will behave as a non-metal. The success of these different, but converging approaches, lends weight to the idea of a simple, universal criterion for rationalizing the instantly-recognizable structure of the periodic table where … the metals are here, the non-metals are there … The challenge of the metallic and non-metallic states of oxides is also briefly introduced. This article is part of the theme issue 'Mendeleev and the periodic table'.
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- 2020
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44. Fuels, power and chemical periodicity.
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Yao B, Kuznetsov VL, Xiao T, Jie X, Gonzalez-Cortes S, Dilworth JR, Al-Megren HA, Alshihri SM, and Edwards PP
- Abstract
The insatiable-and ever-growing-demand of both the developed and the developing countries for power continues to be met largely by the carbonaceous fuels comprising coal, and the hydrocarbons natural gas and liquid petroleum. We review the properties of the chemical elements, overlaid with trends in the periodic table, which can help explain the historical-and present-dominance of hydrocarbons as fuels for power generation. However, the continued use of hydrocarbons as fuel/power sources to meet our economic and social needs is now recognized as a major driver of dangerous global environmental changes, including climate change, acid deposition, urban smog and the release of many toxic materials. This has resulted in an unprecedented interest in and focus on alternative, renewable or sustainable energy sources. A major area of interest to emerge is in hydrogen energy as a sustainable vector for our future energy needs. In that vision, the issue of hydrogen storage is now a key challenge in support of hydrogen-fuelled transportation using fuel cells. The chemistry of hydrogen is itself beautifully diverse through a variety of different types of chemical interactions and bonds forming compounds with most other elements in the periodic table. In terms of their hydrogen storage and production properties, we outline various relationships among hydride compounds and materials of the chemical elements to provide some qualitative and quantitative insights. These encompass thermodynamic and polarizing strength properties to provide such background information. We provide an overview of the fundamental nature of hydrides particularly in relation to the key operating parameters of hydrogen gravimetric storage density and the desorption/operating temperature at which the requisite amount of hydrogen is released for use in the fuel cell. While we await the global transition to a completely renewable and sustainable future, it is also necessary to seek CO
2 mitigation technologies applied to the use of fossil fuels. We review recent advances in the strategy of using hydrocarbon fossil fuels themselves as compounds for the high capacity storage and production of hydrogen without any CO2 emissions. Based on these advances, the world may end up with a hydrogen economy completely different from the one it had expected to develop; remarkably, with 'Green hydrogen' being derived directly from the hydrogen-stripping of fossil fuels. This article is part of the theme issue 'Mendeleev and the periodic table'.- Published
- 2020
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45. Facile in situ reductive synthesis of both nitrogen deficient and protonated g-C 3 N 4 nanosheets for the synergistic enhancement of visible-light H 2 evolution.
- Author
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Li W, Guo Z, Jiang L, Zhong L, Li G, Zhang J, Fan K, Gonzalez-Cortes S, Jin K, Xu C, Xiao T, and Edwards PP
- Abstract
A new strategy is reported here to synthesize both nitrogen deficient and protonated graphitic carbon nitride (g-C
3 N4 ) nanosheets by the conjoint use of NH4 Cl as a dynamic gas template together with hypophosphorous acid (H3 PO2 ) as a doping agent. The NH4 Cl treatment allows for the scalable production of protonated g-C3 N4 nanosheets. With the corresponding co-addition of H3 PO2 , nitrogen vacancies, accompanied by both additional protons and interstitially-doped phosphorus, are introduced into the g-C3 N4 framework, and the electronic bandgap of g-C3 N4 nanosheets as well as their optical properties and hydrogen-production performance can be precisely tuned by careful adjustment of the H3 PO2 treatment. This conjoint approach thereby results in improved visible-light absorption, enhanced charge-carrier separation and a high H2 evolution rate of 881.7 μmol h-1 achieved over the H3 PO2 doped g-C3 N4 nanosheets with a corresponding apparent quantum yield (AQY) of 40.4% (at 420 nm). We illustrate that the synergistic H3 PO2 doping modifies the layered g-C3 N4 materials by introducing nitrogen vacancies as well as protonating them, leading to significant photocatalytic H2 evolution enhancements, while the g-C3 N4 materials doped with phosphoric acid (H3 PO4 ) are simply protonated further, revealing the varied doping effects of phosphorus having different (but accessible) valence states., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2020
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46. Solvation of Na ? in the Sodide Solution, LiNa?10MeNH 2 .
- Author
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Seel AG, Holzmann N, Imberti S, Bernasconi L, Edwards PP, Cullen PL, Howard CA, and Skipper NT
- Abstract
Alkalides, the alkali metals in their ?1 oxidation state, represent some of the largest and most polarizable atomic species in condensed phases. This study determines the solvation environment around the sodide anion, Na
? , in a system of co-solvated Li+ . We present isotopically varied total neutron scattering experiments alongside empirical potential structure refinement and ab initio molecular dynamics simulations for the alkali?alkalide system, LiNa?10MeNH2 . Both local coordination modes and the intermediate range liquid structure are determined, which demonstrate that distinct structural correlations between cation and anion in the liquid phase extend beyond 8.6 ?. Indeed, the local solvation around Na? is surprisingly well defined with strong solvent orientational order, in contrast to the classical description of alkalide anions not interacting with their environment. The ion-paired Li(MeNH2 )4 + ?Na? species appears to be the dominant alkali?alkalide environment in these liquids, whereby Li+ and Na? share a MeNH2 molecule through the amine group in their primary solvation spheres.- Published
- 2019
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47. Rapid, non-invasive characterization of the dispersity of emulsions via microwaves.
- Author
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Yan Y, Gonzalez-Cortes S, Yao B, Slocombe DR, Porch A, Cao F, Xiao T, and Edwards PP
- Abstract
A rapid and non-invasive method to determine the dispersity of emulsions is developed based on the interrelationship between the droplet size distribution and the dielectric properties of emulsions. A range of water-in-oil emulsions with different water contents and droplet size distributions were analysed using a microwave cavity perturbation technique together with dynamic light scattering. The results demonstrate that the dielectric properties, as measured by non-invasive microwave cavity analysis, can be used to characterise the dispersity of emulsions, and is also capable of characterizing heavy oil emulsions. This technique has great potential for industrial applications to examine the sedimentation, creaming and hence the stability of emulsions.
- Published
- 2018
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48. Defining the flexibility window in ordered aluminosilicate zeolites.
- Author
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Wells SA, Leung KM, Edwards PP, Tucker MG, and Sartbaeva A
- Abstract
The flexibility window in zeolites was originally identified using geometric simulation as a hypothetical property of SiO
2 systems. The existence of the flexibility window in hypothetical structures may help us to identify those we might be able to synthesize in the future. We have previously found that the flexibility window in silicates is connected to phase transitions under pressure, structure amorphization and other physical behaviours and phenomena. We here extend the concept to ordered aluminosilicate systems using softer 'bar' constraints that permit additional flexibility around aluminium centres. Our experimental investigation of pressure-induced amorphization in sodalites is consistent with the results of our modelling. The softer constraints allow us to identify a flexibility window in the anomalous case of goosecreekite., Competing Interests: The authors declare no competing interests.- Published
- 2017
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49. Microwaves effectively examine the extent and type of coking over acid zeolite catalysts.
- Author
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Liu B, Slocombe DR, Wang J, Aldawsari A, Gonzalez-Cortes S, Arden J, Kuznetsov VL, AlMegren H, AlKinany M, Xiao T, and Edwards PP
- Abstract
Coking leads to the deactivation of solid acid catalyst. This phenomenon is a ubiquitous problem in the modern petrochemical and energy transformation industries. Here, we show a method based on microwave cavity perturbation analysis for an effective examination of both the amount and the chemical composition of cokes formed over acid zeolite catalysts. The employed microwave cavity can rapidly and non-intrusively measure the catalytically coked zeolites with sample full body penetration. The overall coke amount is reflected by the obtained dielectric loss (ε″) value, where different coke compositions lead to dramatically different absorption efficiencies (ε″/cokes' wt%). The deeper-dehydrogenated coke compounds (e.g., polyaromatics) lead to an apparently higher ε″/wt% value thus can be effectively separated from lightly coked compounds. The measurement is based on the nature of coke formation during catalytic reactions, from saturated status (e.g., aliphatic) to graphitized status (e.g., polyaromatics), with more delocalized electrons obtained for enhanced Maxwell-Wagner polarization.Catalyst deactivation by coke deposition is a major drawback in industrial processes. Here, the authors show a non-intrusive microwave cavity perturbation technique as a powerful tool to determine the nature and extent of coke accumulation in industrially-relevant zeolite catalysts.
- Published
- 2017
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50. Rapid Production of High-Purity Hydrogen Fuel through Microwave-Promoted Deep Catalytic Dehydrogenation of Liquid Alkanes with Abundant Metals.
- Author
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Jie X, Gonzalez-Cortes S, Xiao T, Wang J, Yao B, Slocombe DR, Al-Megren HA, Dilworth JR, Thomas JM, and Edwards PP
- Abstract
Hydrogen as an energy carrier promises a sustainable energy revolution. However, one of the greatest challenges for any future hydrogen economy is the necessity for large scale hydrogen production not involving concurrent CO
2 production. The high intrinsic hydrogen content of liquid-range alkane hydrocarbons (including diesel) offers a potential route to CO2 -free hydrogen production through their catalytic deep dehydrogenation. We report here a means of rapidly liberating high-purity hydrogen by microwave-promoted catalytic dehydrogenation of liquid alkanes using Fe and Ni particles supported on silicon carbide. A H2 production selectivity from all evolved gases of some 98 %, is achieved with less than a fraction of a percent of adventitious CO and CO2 . The major co-product is solid, elemental carbon., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
- Full Text
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