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Advanced upgrading of pyrolysis oil via liquid-liquid extraction

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131594590,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Yi Wei, Hanwu Lei
Keywords:   Microwave pyrolysis; chloroform; liquid-liquid extraction

Abstract. Biomass is one of important renewable energy sources. It can be used to produce carbon-based liquid fuels through biochemical and thermochemical methods. Pyrolysis is a thermal chemical method that converts biomass to high energy fuels called bio-oils which are expected to replace the transportation fuel. However, the bio-oil from the biomass pyrolysis is an intermediate and cannot be directly used as a fuel as it contains large oxygen content and organic acids. Various organics with quite different oxygen-containing functional groups mix together in bio-oil, leading to the high instability of bio-oils. The bio oil catalytic upgrading is a complex reaction network due to the complex compositions of pyrolysis oils. There are problems relevant to deactivation of catalysts caused by coking and metal decomposition. It is known that coking is one of the major challenges for hydrodeoxygenation (HDO) reaction; and coking has close relationship with the compositions of bio-oils since re-polymerization reactions which are the major reactions leading to coking occur on the catalyst surface, which significantly reduces the active sites by competition with the reactant. As a result, the properties of the adsorbed bio-oil feed have an important effect on coke formation. One way to improve the quality and stabilizing bio-oils is to use liquid-liquid extraction method to separate the bio-oil into different chemical groups. The separated bio-oil should have similar oxygen-containing functional groups. Using liquid-liquid extraction, the bio-oils are separated by their polarities and chemical functional groups in different phases. The extraction process purifies the bio-oil compositions, which further benefit the quality of bio-oils, reduce catalyst coking, and improve the quality of catalytically upgraded biofuels. In this research, several designs have been conduct on two projects: 1) Biomass pyrolysis and characterization of the chemical compounds; 2) Liquid-liquid extraction to separate bio-oils into different phases based on polarities and chemical functional groups. In these studies, Douglas fir pellet will be used to produce bio-oils through microwave pyrolysis; solvents, such as ethyl acetate, ether, and chloroform will be used as extraction solvents. The result showed that when under 1:1 solvent to water-phase ratio, using chloroform as extraction solvent, the organic concentration reaches to a 85% of total phenolic compounds and hydrocarbon analyzed by GC/MS.

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