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The Pennsylvania State University The Pennsylvania State University The Graduate School Energy and Geo-environmental Engineering ROLES OF ZEOLITE SUPPORT AND NOBLE METAL IN SULFUR-TOLERANT CATALYST FOR LOW TEMPERATURE HYDROGENATION OF AROMATICS A Dissertation in Energy and Geo-environmental Engineering by Hyun Jae Kim 2011 Hyun Jae Kim Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2011 The dissertation of Hyun Jae Kim was reviewed and approved* by the following: Chunshan Song Distinguished Professor of Fuel Science and Professor of Chemical Engineering Dissertation Advisor Chair of Committee Yaw D. Yeboah Professor of Energy and Mineral Engineering Department Head of Energy and Mineral Engineering Yongsheng Chen Assistant Professor of Energy and Mineral Engineering Adri van Duin Associate Professor of Mechanical Engineering *Signatures are on file in the Graduate School iii ABSTRACT This dissertation focuses on fundamental understanding of the roles of supports and noble metals in the sulfur-tolerant catalysts for low-temperature hydrogenation of aromatics in the presence of sulfur. Emphasis was placed on investigating the effect of supports and supported metals for high sulfur tolerance and verifying a catalyst design concept for the sulfur-tolerant noble metal catalyst based on shape selective exclusion of sulfur and hydrogen spillover for low- temperature hydrogenation of aromatics [C.S. Song, Chemtech, 29 (1999) 26-30]. The effect of supports was explored for sulfur tolerance of the supported Pd catalyst on tetralin hydrogenation in the presence of benzothiophene by varying the Pd catalysts on different supports (mordenite, zeolite Y, zeolite A, amorphous silica-alumina). The pore structures and pore sizes were both found to be the important factors in determining the catalytic activity of sulfur-tolerant metal catalyst. Among the catalysts tested, the acidic zeolite Y-supported Pd catalyst showed excellent sulfur tolerance while maintaining high catalytic activity, which may be mainly due to its high surface area, acidity and three-dimensional zeolite framework. The hybrid zeolite-supported Pd catalyst was prepared to improve sulfur tolerance, based on the proposed catalyst design concept. The hybrid catalyst consists of Pd supported on Y and A type zeolites. For further investigation on small pore system in hybrid catalyst, surface metal passivation by silica coating and pore size control by potassium ion exchange were employed to zeolite A-supported Pd catalyst. Although Pd on Zeolite A showed no catalytic activity for hydrogenation of tetralin, adding the small-pore catalyst to Pd/Y significantly enhanced sulfur tolerance of the catalyst for both naphthalene and tetralin hydrogenation in the presence of sulfur in the form of benzothiophene. Sulfur tolerance of the hybrid catalyst is mainly attributed to the iv small pore system, inducing size-selective exclusion of bulky sulfur compounds as well as hydrogen spillover from metal inside small pore component. Hydrogen spillover plays two roles in maintaining high sulfur tolerance of the hybrid catalyst: first, regeneration of sulfur-poisoned metal active sites in the large pores of Pd/Y as well as hydrodesulfurization of aromatic sulfur compounds over the zeolite Y support. The effect of metal species for the zeolite Y-supported metal catalyst was investigated using various group 10 metals (Ni, Pd, Pt) as well as Pd-Pt bimetal. The metal type also has major impact on sulfur tolerance of the zeolite supported catalyst for tetralin hydrogenation. Even Pd shows better sulfur-tolerance than other monometallic catalysts, Pd-Pt bimetallic catalyst exhibited exceptionally high sulfur-tolerance, maintaining 100% conversion for tetralin hydrogenation in the presence of sulfur, which can be ascribed to high metal dispersion and electron-deficiency of Pd-Pt. Addition of small pore catalyst (silica-coated Pd/KA catalyst) to Pd- Pt/Y also enhances sulfur tolerance of the Pd-Pt catalyst on tetralin hydrogenation even in the presence of 300ppmw sulfur as benzothiophene. On the basis of the above results and discussion focusing on the importance of the supports and metal types for improving sulfur tolerance, the hybrid catalyst system based on the new design concept of sulfur tolerant catalyst is applicable in the development of sulfur tolerant catalysts for low-temperature hydrogenation of aromatics. v TABLE OF CONTENTS LIST OF FIGURES ................................................................................................................. vii LIST OF TABLES ................................................................................................................... xi ACKNOWLEDGEMENTS ..................................................................................................... xii Chapter 1 Introduction ............................................................................................................ 1 Chapter 2 Literature Review ................................................................................................... 5 2.1. Current industrial hydrotreating process ................................................................... 5 2.2. Sulfur poisoning ........................................................................................................ 11 2.3. Strategies for improving sulfur tolerance of noble metal catalysts ........................... 13 2.3.1. Effect of support ............................................................................................. 13 2.3.2. Effect of noble metal ..................................................................................... 16 2.4. Studies on naphthalene hydrogenation ...................................................................... 21 2.4.1. Reaction network for naphthalene and tetralin hydrogenation ....................... 21 2.4.2. Thermodynamic equilibrium of naphthalene hydrogenation ......................... 22 2.5. Application of literature knowledge to this research ................................................ 30 Chapter 3 Effect of support ..................................................................................................... 33 3.1. Introduction ............................................................................................................... 33 3.2. Experimental ............................................................................................................. 34 3.2.1. Catalyst preparation ........................................................................................ 34 3.2.2. Catalyst characterization ................................................................................ 35 3.2.3. Catalyst evaluation ......................................................................................... 36 3.3. Result and discussion ................................................................................................ 37 3.3.1. Effect of support type ..................................................................................... 37 2.3.2. Effect of acidity .............................................................................................. 47 3.4. Conclusion ................................................................................................................ 51 Chapter 4 Enhanced sulfur tolerance of hybrid zeolite-supported Pd catalyst for low temperature hydrogenation of diaromatics ....................................................................... 52 Abstract ............................................................................................................................ 52 4.1. Introduction ............................................................................................................... 53 4.2. Experimental ............................................................................................................. 55 4.3. Result and discussion ................................................................................................ 57 4.4. Conclusion ................................................................................................................ 66 vi Chapter 5 Sulfur-toleranct hybrid zeolite-supported Pd catalyst based on shape-selective exclusion and hydrogen spillover for low temperature hydrogenation of aromatics ....... 67 Abstract ............................................................................................................................ 67 5.1. Introduction ............................................................................................................... 68 5.2. Experimental ............................................................................................................. 71 5.2.1. Catalyst preparation ........................................................................................ 71 5.2.2. Catalyst characterization ................................................................................ 73 5.2.3. Catalyst evaluation ......................................................................................... 74 5.3. Result and discussion ................................................................................................ 76 5.3.1. Characterization of catalyst ............................................................................ 76 5.3.2. Surface metal passivation of zeolite A-supported Pd catalyst ........................ 80 5.3.3. Tetralin hydrogenation over hybrid catalyst .................................................
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