Decalin Dehydrogenation for In-Situ Hydrogen Production To
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DECALIN DEHYDROGENATION FOR IN-SITU HYDROGEN PRODUCTION TO INCREASE CATALYTIC CRACKING RATE OF N-DODECANE Thesis Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Master of Science in Chemical Engineering By Christopher Bruening Dayton, Ohio May, 2018 DECALIN DEHYDROGENATION FOR IN-SITU HYDROGEN PRODUCTION TO INCREASE CATALYTIC CRACKING RATE OF N-DODECANE Name: Bruening, Christopher Robbins APPROVED BY: Matthew J. DeWitt, Ph.D. Donald K. Phelps, Ph.D. Advisory Committee Chairman Committee Member Distinguished Research Engineer Senior Research Chemist University of Dayton Research Institute Air Force Research Laboratory Michael Elsass, Ph.D. Kevin Myers, D.Sc., P.E. Committee Member Committee Member Lecturer Professor Department of Chemical and Materials Department of Chemical and Materials Engineering Engineering Robert J. Wilkens, Ph.D., P.E. Eddy M. Rojas, Ph.D., M.A., P.E. Associate Dean for Research and Innovation Dean, School of Engineering Professor School of Engineering School of Engineering ii ABSTRACT DECALIN DEHYDROGENATION FOR IN-SITU HYDROGEN PRODUCTION TO INCREASE CATALYTIC CRACKING RATE OF N-DODECANE Name: Bruening, Christopher Robbins University of Dayton Advisor: Dr. Matthew J. DeWitt Catalytic cracking of paraffinic hydrocarbons is a widely utilized industrial process, but catalyst deactivation over time requires regeneration or replacement of the catalyst bed. A gaseous hydrogen co-feed can be used to promote hydrocracking and decrease deactivation of the catalyst due to coke formation or active site poisoning. One potential alternative approach to extend the lifetime of a cracking catalyst is to generate molecular hydrogen in-situ via catalytic dehydrogenation of a cycloparaffin. In this effort, studies were performed using model compounds to investigate the impact of catalyst configuration and operating conditions on overall performance. For the purpose of this testing, decalin was selected as a model cycloparaffin, with n-dodecane used as a model n-paraffin compound. A blended cycloparaffin/n-paraffin feed was studied in a dual catalyst flow reactor system, containing both a dehydrogenation and cracking catalyst. Testing was performed with either the dehydrogenation catalyst upstream or iii with the two catalysts physical mixed. Products and reactant conversion rates from these studies were compared to those from a baseline n-paraffin cracking study, with no cycloparaffin or dehydrogenation catalyst present. Several commercially available Zeolite catalysts were initially screened for n-dodecane cracking activity to identify an appropriate cracking catalyst for further study. A Zeolite Y catalyst provided adequate n-dodecane reactivity for observation of reactor configuration impact. Prior to the dual-bed and mixed-bed studies, a synthesized Pt/Al2O3 dehydrogenation catalyst was studied independently with neat decalin feed as well as a blended decalin/n-dodecane feed, for the purpose of determining appropriate reactor conditions to be used in subsequent testing. Using the selected Zeolite Y catalyst, extended duration testing was performed at 400°C and 500 psig to characterize the activity and deactivation rate for n-dodecane cracking, to provide a baseline for subsequent comparison. Similar testing was performed with the Zeolite Y catalyst to investigate the impact of blending decalin or naphthalene with the normal paraffin. A dual-bed reactor configuration utilized the Pt/Al2O3 dehydrogenation catalyst in-line and upstream of the Zeolite Y catalyst, with a 1:1 volumetric blend of decalin/n-dodecane at 400°C and 500 psig. The dehydrogenation bed successfully promoted decalin dehydrogenation for generating in-situ molecular hydrogen. However, minimal initial n-dodecane conversion was observed, which was speculated to be due to strong adsorption of naphthalene dehydrogenation product onto the Zeolite Y catalyst, reducing the number of available active sites. After 240 minutes, n-dodecane conversion in the dual-bed reactor system was higher than the baseline, while decalin conversion was very high for the entire duration. In a mixed bed configuration, the two catalyst beds iv were physically mixed with identical testing conditions. This configuration was intended to reduce the absolute naphthalene concentration on the Zeolite Y catalyst and eliminate the inhibition which occurred in the dual bed configuration. The mixed bed configuration promoted higher initial conversion and lower deactivation rate compared to all other feed/reactor configurations. Overall, it was determined that catalytic dehydrogenation of a cycloparaffin can be successfully employed to increase conversion of a normal paraffin in a catalytic cracking reactor, although future work could further optimize catalyst selection/loading, reactor configuration, and reaction conditions. v ACKNOWLEDGEMENTS I would like to extend thanks to my research advisor, Dr. Matthew DeWitt. His advice and support during the thesis project helped to make this document possible. I would also like to extend gratitude to the other members of my thesis committee: Dr. Donald Phelps, Dr. Michael Elsass, and Dr. Kevin Myers, for reviewing my thesis and providing guidance. I would also like to acknowledge the support of University of Dayton Research Institute employees in assisting me with the project. I would like to thank Richard Striebich and Linda Schafer, who assisted in product analysis; as well as Jhoanna Alger and David Gasper, who assisted in experimental testing. Finally, I would like to thank the Air Force Research Laboratory for funding and support. vi TABLE OF CONTENTS ABSTRACT ....................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................... vi LIST OF FIGURES ........................................................................................................... ix LIST OF TABLES ............................................................................................................ xii CHAPTER 1 INTRODUCTION AND BACKGROUND ............................................... 1 1.1 Introduction ............................................................................................................... 1 1.2 Decalin as a Hydrogen Carrier .................................................................................. 2 1.3 Normal and Isomerized Paraffin Cracking Mechanisms utilizing Zeolite Catalysts .......................................................................................................................... 7 1.4 Hydrocracking, Ring Opening, and Alkylation of Cycloparaffinic and Aromatic Species on Zeolite Catalysts.......................................................................... 13 1.5 Presentation of Research ......................................................................................... 20 CHAPTER 2 MATERIALS AND METHODS ............................................................. 22 2.1 Reactor Setup .......................................................................................................... 22 2.2 Analysis Instrumentation ........................................................................................ 26 2.3 Catalyst Synthesis ................................................................................................... 27 CHAPTER 3 ZEOLITE ACTIVITY SCREENING....................................................... 30 CHAPTER 4 DEHYDROGENATION OF DECALIN ................................................. 34 4.1 Experimental Conditions of Study Segments ......................................................... 34 4.2 Experimental Results............................................................................................... 36 4.3 Primary Conclusions from Decalin Dehydrogenation Study .................................. 42 CHAPTER 5 DEHYDROGENATION OF DECALIN BLENDED WITH N- DODECANE..................................................................................................................... 44 5.1 Experimental Conditions of Study Segments ......................................................... 44 5.2 Experimental Results............................................................................................... 45 vii 5.3 Primary Conclusions from Decalin/n-Dodecane Dehydrogenation Study ............. 47 CHAPTER 6 DETERMINATION OF BASELINE DEACTIVATION RATE FOR N-DODECANE CRACKING OVER ZEOLITE Y ................................................ 49 6.1 Experimental Conditions of Study Segments ......................................................... 49 6.2 Experimental Results............................................................................................... 52 6.3 Overall Conclusions from n-dodecane Cracking Study .......................................... 57 CHAPTER 7 CRACKING OF N-DODECANE AND DECALIN BLENDED FEED OVER ZEOLITE Y .............................................................................................. 59 7.1 Experimental Conditions of Study Segments ......................................................... 59 7.2 Experimental Results............................................................................................... 60 7.3 Primary Conclusions from n-Dodecane/Decalin Cracking Study........................... 68 CHAPTER 8 CRACKING OF N-DODECANE AND NAPHTHALENE BLENDED FEED OVER