A Dissertation Entitled Production of Biofuels and Value-Added
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A Dissertation entitled Production of Biofuels and Value-Added Chemicals from Oleaginous Biomass by Yaser Shirazi Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Chemical and Environmental Engineering ________________________________________ Dr. Sridhar Viamajala, Committee Chair ________________________________________ Dr. Sasidhar Varanasi, Committee Member ________________________________________ Dr. Ana C. Alba-Rubio, Committee Member ________________________________________ Dr. G. Glenn Lipscomb, Committee Member ________________________________________ Dr. Maria R. Coleman, Committee Member ________________________________________ Dr. Patricia Ann Relue, Committee Member ________________________________________ Dr. Amanda Bryant-Friedrich, Dean College of Graduate Studies The University of Toledo March 2018 Copyright 2018, Yaser Shirazi This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Production of Biofuels and Value-Added Chemicals from Oleaginous Biomass by Yaser Shirazi Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Chemical and Environmental Engineering The University of Toledo March 2018 Oleaginous biomass such as oilseeds and microalgae are attractive feedstocks for biofuels and chemicals production due to the presence of energy-dense triglycerides. Pyrolysis is a promising technique that can thermally degrade whole biomass and/or triglycerides to drop-in fuels or fuel precursors. However, low yield of liquid products has remained the major obstacle for commercialization of triglyceride pyrolysis since feedstock price is the most significant component of the cost for fuel production from triglycerides. The current practice of feeding bulk liquids into hot pyrolysis reactors results in excessive decomposition and polymerization due to slow volatilization and long residence time. As such, we designed and built a novel continuous pyrolysis system equipped with an atomizer to introduce micron-sized droplets of oil into hot pyrolysis reactors. This approach facilitates rapid vaporization of the feed such that the subsequent vapor phase degradation is efficient and results in high yields of bio-oil. Further, when the volatilized feedstocks are passed through a heterogeneous catalyst bed, this method enables vapor-phase catalytic reactions with high-selectivity and high-yield (with low coke formation). Besides triglycerides, the pyrolysis system has the ability to process feedstocks containing free fatty acids (e.g. tall oil from wood pulping, waste cooking oils or oils from iii microalgae) that are generally unsuitable for biodiesel production. Finally, the reactor can be used for synthesis of fatty acid derivatives (e.g. fatty nitriles, fatty esters or alcohols) by introducing additional reactants (e.g. ammonia, methanol or hydrogen) and suitable catalysts. Pyrolysis of soybean oil in the absence of catalyst resulted in bio-oil yields as high as 88% (theoretical yield is approximately 92%) at optimal conditions (Trxn =500 °C and τ = 60s) with products consisting of 38% hydrocarbons (22% C5-C12 and 16% >C12), 33% long-chain fatty acids (C16-C18, but primarily oleic acid) and 15% short-chain fatty acids (C6-C12). To promote triglyceride deoxygenation and produce high value aromatics, pyrolysis of soybean oil as well as non-edible oils (such as pennycress, camelina and waste cooking oil) in the presence of zeolite resulted in a yield of nearly 60% liquid products, of which more than 70% was benzene, toluene and xylene (BTX). Regeneration of catalyst allowed prolonger reuse - 12 reaction-regeneration cycles were performed without any measurable loss in catalyst performance. To assess the direct production of fatty acid derivatives, triglyceride feed was allowed to react with ammonia that was co-fed into the reactor. In the presence of V2O5 near-theoretical fatty nitrile yields (84 wt.% relative to the feed mass) were obtained. Energy balance calculations indicate that the one-pot reaction vapor phase reaction requires significantly lower energy than the conventional process that relies on the energy-intense triglyceride hydrolysis. To allow (1) separate recovery of energy-dense lipid pyrolysis products and the lower calorific value bio-oils from the degradation of starch and protein and (2) tailored vapor phase upgrading of the resulting fractions, we implemented a two-stage fractional pyrolysis integrated with vapor phase upgrading on whole microalgae biomass. Chlorella iv sp. was first pyrolyzed at 320 °C to volatilize and degrade the biomass starch and a majority of the protein. Then, the residual biomass was pyrolyzed again at 450 °C to recover products from lipid decomposition. The volatiles from each fraction were passed through an ex-situ zeolite catalyst which resulted in high yield of BTX and catalyst-free biochar. v Dedicated to My Parents vi Acknowledgements I would like to thank Dr. Sridhar Viamajala (my advisor) for his help, advice and mentorship throughout my PhD studies. I also thank him for assisting me to write this dissertation. I thank Dr. Sasidhar Varanasi for his guidance, advice and support during my PhD research. I thank my dissertation committee - Drs. G. Glenn Lipscomb, Sasidhar Varanasi, Ana C. Alba-Rubio, Maria R. Coleman and Patricia Ann Relue for their help to improve my dissertation. I also acknowledge the funding agencies for supporting this thesis. This work was supported by National Science Foundation (CHE-1230609) and the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Bioenergy Technologies Office (BETO) (contract No. DE-EE0005993). vii Table of Contents 1 Background and significance ……………………………………………………..1 1.1 Production of biofuels and value-added chemicals from biomass…..……………..1 1.2 Oleaginous biomass...……………………………………………………………..2 1.3 Triglyceride conversion into biofuels ……………………………………………..5 1.4 Research outline…….……………………………………………………………..8 2 High-Yield Production of Fuel- and Oleochemical- Precursors from Triacylglycerols in a Novel Continuous-Flow Pyrolysis Reactor…...……………………12 2.1 Abstract……..……………………………………………………………………12 2.2 Introduction………………………………………………………………………13 2.3 Experimental..……………………………………………………………………16 2.3.1 Materials…………………………………………………………………………16 2.3.2 Experimental set-up...……………………………………………………………16 2.3.3 Fractionation of pyrolysis liquid products……………………………………….18 2.3.4 Experimental design……………………………………………………………...19 2.3.5 Feedstock analysis………………………………………………………………..20 2.3.6 Gas chromatography analysis…………………………………………………….20 2.4 Results and Discussion…………………………………………………………...23 2.4.1 Design of the experimental pyrolysis system…………………………………….23 2.4.2 Feedstock characterization……………………………………………………….26 2.4.3 Pyrolysis yield ……………………………………………………………………27 2.4.4 Products analysis…………………………………………………………………30 2.4.5 Product distillation and detailed hydrocarbon analysis…………………………...36 viii 2.4.6 Feasibility of isolating oleic acid from soy oil via pyrolysis……………………..40 2.5 Conclusions………………………………………………………………………41 3 High Yield Production of Hydrocarbons from Non-edible Oils Through Reactive Pyrolysis System…………………………………………………………………………43 3.1 Abstract…………………………………………………………………………..43 3.2 Introduction………………………………………………………………………44 3.3 Experimental……………………………………………………………………..48 3.3.1 Materials…………………………………………………………………………48 3.3.2 Experimental set-up……………………………………………………………...49 3.3.3 Experimental design……………………………………………………………...51 3.3.4 Products analysis…………………………………………………………………51 3.3.5 Fractionation of pyrolysis liquid products………………………………………..53 3.4 Results and Discussion…………………………………………………………...54 3.4.1 Catalytic pyrolysis of triglyceride…………………………………………………..54 3.4.1.1 Effects of temperature and residence time on products yield……………………..54 3.4.1.2 Effects of temperature and residence time on products composition……………..58 3.4.1.3 Feasibility of complete deoxygenation of liquid product…………………………62 3.4.1.4 Effect of reaction time on stream…………………………………………………64 3.4.2 Catalytic pyrolysis of non-edible oils feedstock……………………………………67 3.4.2.1 Products yields and compositions………………………………………………...67 3.4.2.2 Catalyst long-term reusability …………………………………………………...69 3.4.2.2.1 Design of reaction-regeneration cycle………………………………………….69 3.4.2.2.2 Products yields and compositions from reaction-regeneration cycle…………...70 ix 3.4.2.2.3 Fractionation of liquid products………………………………………………...71 3.5 Conclusion……………………………………………………………………….73 4 High-Yield Production of Fatty Nitriles by One-Step Vapor Phase Thermo- Catalysis of Triglycerides………………………………………………………………...74 4.1 Abstract…………………………………………………………………………..74 4.2 Introduction………………………………………………………………………75 4.3 Experimental……………………………………………………………………..80 4.3.1 Materials…………………………………………………………………………80 4.3.2 Experimental set-up……………………………………………………………...80 4.3.3 Experimental conditions………………………………………………………….82 4.3.4 Catalyst characterization…………………………………………………………83 4.3.5 Feedstock and products analysis………………………………………………….84 4.4 Results and Discussion…………………………………………………………...85 4.4.1 Feedstock characterization…………………………………………………………85 4.4.2 Catalyst characterization…………………………………………………………...85 4.4.3 Products yields and compositions…………………………………………………..86 4.4.4 Effects of catalyst acidity on fatty nitrile yield……………………………………...89 4.4.5 Effect of NH3/triglyceride molar ratio……………………………………………...90