Impact of solvent type and condition on biomass liquefaction to produce heavy oils in high yield with low oxygen contents

Abstract

Bio-oils produced by processes such as slow or fast pyrolysis typically contain high water and oxygen contents, which make them incompatible with conventional fuels. It is therefore necessary to upgrade the bio-oils to reduce their oxygen and water contents. The bio-oil upgrading process can consume up to 84wt% of the initial bio-oil it is therefore important to develop other alternative approaches to generate high quality bio-oil. Thermolytic liquid solvent extraction (LSE) has been considered as a potential viable process due to the high liquid yield, better product quality and water free nature of the final products.In this study, a novel LSE process of biomass liquefaction has been studied under various conditions of solvent type, temperature, and biomass species. Compared to currently available commercial pyrolysis approaches, this process using tetralin as a solvent is shown to be capable of generating high quality bio-oil with low oxygen contents (ca. 5.9%) at extremely high overall conversions of up to 87 and 92 (%) dry and ash free basis (DAF) from Scotch pine and miscanthus, respectively. Overall, the study has demonstrated the advantages of LSE for bio-oil generation from biomass, in terms of producing high conversions to liquid products that are compatible with existing petroleum heavy feedstocks.