Co-cracking of bio-oil distillate bottoms with vacuum gas oil for enhanced production of light compounds

Authors: Choi, Yongsuck; Elkasabi, Yaseen; Tarves, Paul; Mullen, Charles; Boateng, Akwasi

Submitted to: Journal of Analytical and Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2018
Publication Date: 4/11/2018
Citation: Choi, Y., Elkasabi, Y.M., Tarves, P.C., Mullen, C.A., Boateng, A.A. 2018. Co-cracking of bio-oil distillate bottoms with vacuum gas oil for enhanced production of light compounds. Journal of Analytical and Applied Pyrolysis. 132:65-71.

Interpretive Summary: Pyrolysis is a technology for converting different types of agricultural wastes and crops into a crude oil for making biofuels. This crude oil (termed “bio-oil”) can be converted into usable fuels and chemicals, but the cost of building a new biofuel refinery is quite burdensome. Some explored methods to increase efficiency revolve around refinery integration – i.e. using the same types of equipment and processes found in petroleum refineries to process bio-oil. Also, another method is to utilize some components of petroleum in combination with components of bio-oil, so that they can, together, produce greater yields of desired product than what would be realized by themselves. This strategy is referred to as ‘coprocessing.’ This work explored strategies for coprocessing the heavy fraction of pyrolysis bio-oil together with the heavy fractions of petroleum (vacuum gas oil). Under particular conditions, coprocessing of these two heavy oil fractions can increase production of light gaseous compounds that are highly desired fuels and/or commodity chemicals. These results may make it easier for refineries to accommodate technologies for biorenewable fuels production.

Technical Abstract: Seamless co-processing of pyrolysis bio-oil within existing petroleum refineries is the most synergistic and economic way to improve biorefinery output. Coprocessing bio-oil with vacuum gas oil (VGO) is one logical pathway. Bio-oil has a viscosity and molecular weight range similar to that of VGO, and the hydrogen-rich nature of VGO can chemically complement the bio-oil hydrogen deficiency. Distillation of biomass pyrolysis oils produces solid residues with a significant fraction of fixed carbon and heavy volatiles. Maximization of yields of light compounds like olefins and gasoline-range aromatics are crucial for both attainment of desired product output levels as well as to follow methods that mimic petroleum-based methods and chemistries. Herein we discuss a systematic study on the additive coprocessing of specific bio-oil distillation residues with VGO. Tail-gas reactive pyrolysis (TGRP) bio-oils from spirulina, switchgrass, and guayule biomasses were distilled, and their residues were subject to analytical experiments in mixtures with VGO over different zeolite catalysts (no catalyst, HZSM-5, Y-zeolite). Switchgrass-based bottoms exhibit greater hydrogen deficiency and higher oxygen content compared with that of spirulina or guayule. Switchgrass-based bottoms, with or without VGO, produced more aromatics and less olefins and alkanes, compared with spirulina or guayule residues. When compared across different mixing ratios, thermal cracking of a 10:1 guayule/VGO mixture resulted in higher aromatics yields than even the VGO by itself. Addition of more VGO up to a 1:1 ratio of VGO/switchgrass bottoms nearly tripled the production of BTEX compounds. For hydrogen-rich bottoms spirulina and guayule, LPG-range olefins yields increased nearly 50% for 1:1 VGO/bottoms blends, compared with theoretical yields.