Biobased tar pitch produced from biomass pyrolysis oils

Abstract

Petroleum-based carbon solid materials, such as petcoke and coal tar pitch, have decreased in quality and/or availability due to various factors, such as the declining elemental quality of crude oil and the push towards environmental sustainability. Coal tar pitch acts as a binder in smelting anodes for aluminum production, which contributes significantly to the fossil-based CO2 production globally. In an effort to reduce the carbon footprint of these processes, we synthesized a renewable biopitch based on biomass pyrolysis. In comparison to previous studies on biopitch, we utilized pyrolysis bio-oils with reduced oxygen content (<15%). Guayule and switchgrass biomasses served as the biomass of choice, and their bio-oils underwent continuous distillation. Solid residues underwent extraction to remove toluene insolubles (TI), and the remaining fraction underwent heat treatment to ∼ 380 °C. While both the residues and biopitches contained trace amounts of quinoline insolubles (QI), the pitch TI amounted to 32 – 54 wt%. Coking values exceeded 43 wt% for both pitches, making them feasible for anode utilization. The use of distilled partially deoxygenated oils enables greater flexibility for biorefineries to provide a marketable coproduct alongside hydrocarbon fuels.