University of Massachusetts Amherst ScholarWorks@UMass Amherst Open Access Dissertations 2-2011 Pyrolysis Oils: Characterization, Stability Analysis, and Catalytic Upgrading to Fuels and Chemicals Tushar Vispute University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/open_access_dissertations Part of the Chemical Engineering Commons Recommended Citation Vispute, Tushar, "Pyrolysis Oils: Characterization, Stability Analysis, and Catalytic Upgrading to Fuels and Chemicals" (2011). Open Access Dissertations. 349. https://scholarworks.umass.edu/open_access_dissertations/349 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Open Access Dissertations by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. PYROLYSIS OILS: CHARACTERIZATION, STABILITY ANALYSIS, AND CATALYTIC UPGRADING TO FUELS AND CHEMICALS A Dissertation Presented by TUSHAR P. VISPUTE Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY February 2011 Chemical Engineering © Copyright by Tushar P. Vispute 2011 All Rights Reserved PYROLYSIS OILS: CHARACTERIZATION, STABILITY ANALYSIS, AND CATALYTIC UPGRADING TO FUELS AND CHEMICALS A Dissertation Presented by TUSHAR P. VISPUTE Approved as to style and content by: _______________________________________ George W. Huber, Chair _______________________________________ W. Curt Conner, Member _______________________________________ Scott M. Auerbach, Member ____________________________________ T. J. (Lakis) Mountziaris, Department Head Chemical Engineering ACKNOWLEDGEMENTS I would like to deeply acknowledge the help and support of my advisor Prof. George W. Huber on this fascinating research program. George is an excellent mentor and provides an outstanding research environment in the group for graduate students to work and develop. I am fortunate to be one of his first graduate students and witness him build his successful career. I am also very thankful to Prof. Curt Conner and Prof. Scott Auerbach, for being not only very helpful committee members but also invaluable mentors on several occasions. Being one of the first two members of the group, we had to build the Huber group labs from the scratch and Curt was a tremendous help for me in that. I cannot forget that in our first year he took me and Hakan down to New Jersey in his van to buy the used lab equipments to get us started. I would like to thank all the present and past group members of Huber research group for all the enlightening discussions we had in labs and group meetings. Specifically I would like to thank Hakan Olcay and Geoff Tompsett for their insight and help with equipment design. I would like to thank Torren Carlson for the collaboration on catalytic fast pyrolysis project. I would also like to thank Asad Javaid and Xiaoming Pan for the collaboration on bio-oil stabilization project and for carrying out bio-oil filtration and viscosity measurements experiments respectively. I would like to thank Aimaro Sanna and Huiyan Zhang for help with bio-oil hydroprocessing and zeolite upgrading experiments respectively. I would also like to thank Aniruddha Upadhye for help with bio-oil characterization. I would like to thank all the people I met here at UMass that made my five years of stay happy and memorable. I would particularly like to thank Suresh Gupta, Sarvesh iv Agrawal, Vishal Gaurav, Achyuta Teella, and Hakan Olcay for their friendship. My family has been a continuous source of encouragement and support for me. They have guided and supported me through all my decisions. I would like to thank my parents, my sister Prachi, and my brother Tejas for their unconditional love. Lastly I would like to acknowledge my funding agencies. This work was supported by the U. S. Department of Energy Office of Energy Efficiency and Renewable Energy, under grant DE-FG36- 08GO18212 and by the Defense Advanced Research Project Agency through the Defense Science Office Cooperative Agreement HR0011-09-C-0075. v ABSTRACT PYROLYSIS OILS: CHARACTERIZATION, STABILITY ANALYSIS, AND CATALYTIC UPGRADING TO FUELS AND CHEMICALS FEBRUARY 2011 TUSHAR P. VISPUTE B.Chem.Engg., INSTITUTE OF CHEMICAL TECHNOLOGY, UNIVERSITY OF MUMBAI Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor George W. Huber There is a growing need to develop the processes to produce renewable fuels and chemicals due to the economical, political, and environmental concerns associated with the fossil fuels. One of the most promising methods for a small scale conversion of biomass into liquid fuels is fast pyrolysis. The liquid product obtained from the fast pyrolysis of biomass is called pyrolysis oil or bio-oil. It is a complex mixture of more than 300 compounds resulting from the depolymerization of biomass building blocks, cellulose; hemi-cellulose; and lignin. Bio-oils have low heating value, high moisture content, are acidic, contain solid char particles, are incompatible with existing petroleum based fuels, are thermally unstable, and degrade with time. They cannot be used directly in a diesel or a gasoline internal combustion engine. One of the challenges with the bio-oil is that it is unstable and can phase separate when stored for long. Its viscosity and molecular weight increases with time. It is important to identify the factors responsible for the bio-oil instability and to stabilize the vi bio-oil. The stability analysis of the bio-oil showed that the high molecular weight lignin oligomers in the bio-oil are mainly responsible for the instability of bio-oil. The viscosity increase in the bio-oil was due to two reasons: increase in the average molecular weight and increase in the concentration of high molecular weight oligomers. Char can be removed from the bio-oil by microfiltration using ceramic membranes with pore sizes less than 1 µm. Removal of char does not affect the bio-oil stability but is desired as char can cause difficulty in further processing of the bio-oil. Nanofiltration and low temperature hydrogenation were found to be the promising techniques to stabilize the bio-oil. Bio-oil must be catalytically converted into fuels and chemicals if it is to be used as a feedstock to make renewable fuels and chemicals. The water soluble fraction of bio- oil (WSBO) was found to contain C2 to C6 oxygenated hydrocarbons with various functionalities. In this study we showed that both hydrogen and alkanes can be produced with high yields from WSBO using aqueous phase processing. Hydrogen was produced by aqueous phase reforming over Pt/Al2O3 catalyst. Alkanes were produced by hydrodeoxygenation over Pt/SiO2-Al2O3. Both of these processes were preceded by a low temperature hydrogenation step over Ru/C catalyst. This step was critical to achieve high yields of hydrogen and alkanes. WSBO was also converted to gasoline-range alcohols and C2 to C6 diols with up to 46% carbon yield by a two-stage hydrogenation process over Ru/C catalyst (125 °C) followed by over Pt/C (250 °C) catalyst. Temperature and pressure can be used to tune the product selectivity. The hydroprocessing of bio-oil was followed by zeolite upgrading to produce C6 to C8 aromatic hydrocarbons and C2 to C4 olefins. Up to 70% carbon yield to aromatics vii and olefins was achieved from the hydrogenated aqueous fraction of bio-oil. The hydroprocessing steps prior to the zeolite upgrading increases the thermal stability of bio- oil as well as the intrinsic hydrogen content. Increasing the thermal stability of bio-oil results in reduced coke yields in zeolite upgrading, whereas, increasing the intrinsic hydrogen content results in more oxygen being removed from bio-oil as H2O than CO and CO2. This results in higher carbon yields to aromatic hydrocarbon and olefins. Integrating hydroprocessing with zeolite upgrading produces a narrow product spectrum and reduces the hydrogen requirement of the process as compared to processes solely based on hydrotreating. Increasing the yield of petrochemical products from biomass therefore requires hydrogen, thus cost of hydrogen dictates the maximum economic potential of the process. viii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................................................................... iv ABSTRACT ....................................................................................................................... vi LIST OF TABLES ............................................................................................................ xii LIST OF FIGURES ...........................................................................................................xv CHAPTER 1. INTRODUCTION AND OBJECTIVES .................................................................1 1.1 Introduction ............................................................................................1 1.2 Objectives ..............................................................................................5 2. MATERIALS AND METHODS .............................................................................7 2.1 Bio-oil ....................................................................................................7 2.2 Elemental Analysis, Ash Content, Viscometry, Accelerated Stability Testing, Water Analysis, TAN Measurement, Catalyst Characterization and TOC Analysis