(449a) Desulfurization and Coking of Hydrocarbon Fractions from Biomass Pyrolysis Oils

Elkasabi, Y., USDA-ARS
Fast pyrolysis is a thermochemical process for converting biomass into a crude liquid product (bio-oil), which can be hydrotreated into fuel-grade hydrocarbons. Previously, we demonstrated that advanced pyrolysis processes (e.g. tail-gas reactive pyrolysis (TGRP), catalytic fast pyrolysis) produce bio-oils that are partially deoxygenated. Subsequently, these oils undergo facile separations processes like distillation and extraction, producing a hydrocarbon-rich fraction and a phenolic-rich fraction.

Based on the hydrocarbon fraction of bio-oil, we processed the hydrocarbon fraction to produce fuel-grade hydrocarbons and calcined coke. We used bio-oils sourced from switchgrass and guayule bagasse feedstocks, the latter of which contains elevated levels of sulfur (400 – 500 ppm) due to biomass processing. Distilled fractions of bio-oil hydrocarbons were found to contain sulfur ranging from 400 – 700 ppm. Sulfur characterization revealed the sulfur groups to be labile, so Raney Nickel was used for hydrogenation, which reduced sulfur content to < 15 ppm. When co-processed with petroleum coke, the heaviest hydrocarbon fraction produces calcined coke with both a reduced metals concentration and sufficient crystallinity for aluminum smelting applications (~22 – 25 A).