Hybrid Gasoline Production from Black Liquor through Coprocessing

Abstract

A new route is presented as a stepwise upgrading process from black liquor issued from the kraft process to hybrid gasoline: (i) hydrothermal liquefaction (HTL) to produce biocrude, (ii) removal of alkaline metal salts, (iii) hydrodeoxygenation (HDO) for oxygen removal and decrease of molar weight, and finally (iv) coprocessing with vacuum gas oil (VGO) by catalytic cracking to produce gasoline as a second-generation transportation biofuel. A high degree of deoxygenation was found to be quite beneficial to the further cracking of the refined crude oil into gasoline fractions. Thus, for this coprocessing step, it was found that, by limiting the percentage of added pretreated biocrude to about 10 wt %, high naphtha yields (45% compared to 48% for pure VGO cracking) were maintained, and without a significant change in the coke yield. This result is promising since naphtha, the gasoline-rich fraction, is the main target product in FCC. More research is needed in the detailed characterization of the coprocessing products and in checking the quality and compatibility of the hybrid fuel with gasoline standards. Further optimization in the HTL and HDO steps can likely be achieved, possibly allowing coprocessing of larger quantities of HDO biocrude than 10 wt %.