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Hydrogenation and Dehydrogenation Kinetics and Catalysts for New Hydrogen Storage Liquids

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Hydrogenation and Dehydrogenation Kinetics and Catalysts for New Hydrogen Storage Liquids Hydrogenation and Dehydrogenation Kinetics and Catalysts for New Hydrogen Storage Liquids by Farnaz Sotoodeh M.Sc. in Chemical Engineering, Iran University of Science and Technology, 2006 B.Sc. in Chemical Engineering, Iran University of Science and Technology, 2003 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy in THE FACULTY OF GRADUATE STUDIES (Chemical and Biological Engineering) The University of British Columbia (Vancouver) June 2011 ⃝c Farnaz Sotoodeh, 2011 Abstract Due to the very low density of H2, practical storage and recovery of H2 has been a challenge in utilizing H2 as an alternative fuel. Organic heteroaromatics have attracted interest because of their thermal stability and high storage capacity. In this study, H2 storage and recovery from these compounds were investigated. The kinetics of the hydrogenation/dehydrogenation reactions was studied and DFT cal- culations were used to understand the dehydrogenation product distribution. The hydrogenation of N-ethylcarbazole and carbazole at 403-423 K on a sup- ported Ru catalyst was well described by first-order kinetics. The hydrogenation of N-ethylcarbazole was significantly faster than the hydrogenation of carbazole, and >95 % selectivity to dodecahydro-N-ethylcarbazole and dodecahydrocarbazole was achieved, respectively. The dehydrogenation kinetics of dodecahydro-N-ethylcarbazole was studied at 101 kPa and 423-443 K over a Pd catalyst prepared by wet impregnation and calci- nation in air. The reactions followed first-order kinetics with 100 % conversion but only 69 % recovery of H2 was achieved at 443 K, due to minimal selectivity to N- ethylcarbazole. The complete recovery of H2 from dodecahydro-N-ethylcarbazole was achieved at 443 K and 101 kPa using Pd/SiO2 catalysts prepared by incipient wetness impregnation with calcination in He. The dehydrogenation TOF and se- lectivity to N-ethylcarbazole were dependent upon the Pd particle size. The effect of the N heteroatom on the dehydrogenation of polyaromatics was studied by comparison of dodecahydro-N-ethylcarbazole, dodecahydrocarbazole ii and dodecahydrofluorene dehydrogenation over Pd catalysts. The dehydrogena- tion of dodecahydro-N-ethylcarbazole and dodecahydrocarbazole were structure sensitive. The dehydrogenation rate of dodecahydrocarbazole was slower than dodecahydro-N-ethylcarbazole. Despite catalyst poisoning through the N atom in dodecahydrocarbazole, the N heteroatom was found to favor dehydrogenation, making heteroaromatics better candidates for H2 storage than aromatics. The structure sensitivity of the reactions and the observed product distribu- tion are explained in view of DFT calculations that showed that the adsorption of dodecahydro-N-ethylcarbazole on Pd required multiple catalytic sites and the heat of adsorption was dependent upon the surface structure. The effect of the ethyl group and the N heteroatom on the dehydrogenation rate of dodecahydro- N-ethylcarbazole was also investigated by comparing the adsorption energies of dodecahydro-N-ethylcarbazole with dodecahydrocarbazole and dodecahydrofluo- rene. iii Preface This dissertation consists of six manuscripts five of which are included in Chap- ters 2 to 6, and one of which is included in Appendix H. This PhD work has been done by Farnaz Sotoodeh under the direct supervision of Professor Kevin J. Smith in the Department of Chemical and Biological Engineering at the University of British Columbia. Preparation of the dissertation, literature review, experimen- tal design and set−up, data collection and analysis, reaction modeling and kinetic study, theoretical molecular modeling of the dehydrogenation reactions, as well as the analysis and interpretation of the results in this thesis have been performed by Farnaz Sotoodeh under the supervision of Professor Kevin J. Smith. The manuscripts included in this dissertation are listed below. For the manuscripts with co-authors, the contributions of Farnaz Sotoodeh have been described in de- tail. 1. F. Sotoodeh and K.J. Smith (2010) Kinetics of hydrogen uptake and release from heteroaromatic compounds for hydrogen storage, Industrial and Engi- neering Chemistry Research, 49, 1018-1026. A version of this manuscript is included in Chapter 2. The catalyst preparation and characterization, hydrogenation reactor set−up and performing the hydrogenation reactions, as well as the dehydrogenation reactor set−up, carrying out the dehydrogenation reactions, hydrogenation and dehydrogenation reactions sample collection and analysis of data, hydro- genation and dehydrogenation network mathematical modeling and coding, as well as the kinetic analysis of the reactions, have been done by Farnaz So- iv toodeh. The preparation and writing of the manuscript was done by Farnaz Sotoodeh under direct supervision and final approval of Professor Kevin J. Smith. 2. F. Sotoodeh, L. Zhao and K.J. Smith (2009) Kinetics of H2 recovery from dodecahydro-N-ethylcarbazole over a supported Pd catalyst, Applied Catal- ysis A: General 362, 155-162. A version of this manuscript is included in Chapter 3. The catalyst preparation, characterization, design and experimental set−up for the dehydrogenation reactions, sample collection and data analysis, ki- netic study of the reactions, mathematical modeling of the reaction network and coding have been done by Farnaz Sotoodeh under the direct supervi- sion of Professor Kevin J. Smith. The manuscript was prepared and written by Farnaz Sotoodeh with final approval of Professor Kevin J. Smith. Some portions of the liquid sample analysis of the dehydrogenation reactions were done by Liang Zhao. 3. F. Sotoodeh and K.J. Smith (2011) Structure sensitivity of dodecahydro-N- ethylcarbazole dehydrogenation over Pd catalysts, Journal of Catalysis 279, 36-47. A version of this manuscript is included in Chapter 4. The catalyst preparation and characterization, catalyst testing including the experimental reaction design and set−up, performing the reactions and data collection by sampling, data analysis of the experiments and results inter- pretation, kinetic studies of the dehydrogenation reactions, theoretical work including molecular design of the dehydrogenation reaction, DFT calcula- tions using the Material Studio software and the theoretical data analysis, as well as interpretation of the results, have been done by Farnaz Sotoodeh un- der the direct supervision of Professor Kevin J. Smith. This manuscript was prepared and written by Farnaz Sotoodeh with final approval of Professor Kevin J. Smith. 4. F. Sotoodeh, B.J.M. Huber and K.J. Smith, The effect of the N-heteroatom v on the dehydrogenation of polyaromatics used for hydrogen storage, to be submitted. A version of this manuscript is included in Chapter 5. The catalyst preparation and characterization, the hydrogenation and dehy- drogenation reaction experimental set−up and design, performing the hydro- genation reactions of carbazole and N−ethylcarbazole, performing the dehy- drogenation reactions of dodecahydro-N-ethylcarbazole, the kinetic study of the dehydrogenation reactions and the data analysis of the dehydrogenation reactions of dodecahydro-N-ethylcarbazole as well as interpretation of the results have been done by Farnaz Sotoodeh under the direct supervision of Professor Kevin J. Smith. The preparation and writing of the manuscript were done by Farnaz Sotoodeh with final approval of Professor Kevin J. Smith. Some part of the dehydrogenation reactions of dodecahydrocarbazole and dodecahydrofluorene and liquid sample analysis were done by Benjamin J.M. Huber. 5. F. Sotoodeh and K.J. Smith, Density functional theory study of dodecahydro- N-ethylcarbazole dehydrogenation over a Pd catalyst, to be submitted. A version of this manuscript is included in Chapter 6. Molecular design of the dehydrogenation reaction including building the chemical structure of the reactants, products and catalyst surface, perform- ing the geometry optimization of the designed systems using Material Studio software, performing potential energy surface calculations by doing transi- tion state search through each catalytic step, theoretical analysis of the ob- tained results, as well as interpretation of the results through comparison with the experimental results, have been done by Farnaz Sotoodeh under di- rect supervision of Professor Kevin J. Smith. The preparation and writing of the manuscript was done by Farnaz Sotoodeh with final approval of Profes- sor Kevin J. Smith. The following manuscript is included in the “Additional publications” section, Ap- pendix H. vi L. Zhao, F. Sotoodeh and K.J. Smith (2010) Increased surface area of unsupported Mo2C catalyst by alkali-treatment, Catalysis Communications 11, 391-395. Preparation of the 12 h alkali-treated Mo2C catalyst, catalyst characterizations including X-ray diffraction (XRD), BET surface area and pore size distributions measurements of the 6 h and 12 h alkali-treated Mo2C catalysts, as well as dehy- drogenation reactions of tetrahydrocarbazole over a 5 wt % Pd/SiO2 were done by Farnaz Sotoodeh under direct supervision of Professor Kevin J. Smith. Writing the manuscript, some portions of the catalyst preparation and characterization, as well as CO hydrogenation reactions were done by Liang Zhao. vii Table of Contents Abstract . ii Preface . iv Table of Contents . viii List of Tables . xiii List of Figures . xvii Glossary . xxiv Acknowledgments . xxviii Dedication . xxx 1 Introduction . 1 1.1 Introduction . 2 1.2 Objective of this thesis . 3 1.3 Approach
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