Synergistic effect in co-processing a residue from a transesterification process with vacuum gas oil in fluid catalytic cracking

Abstract

• Co-processing of bio-oil in existing fluid catalytic cracking unit produces biofuel. • Bio-oil oxygen content determines its blends level with vacuum gas oil or VGO. • Distillation residue from biodiesel production using waste fats and oil is used. • Synergistic effect of bio-oil and VGO shows yield of gasoline higher than predicted. • Cracking of 10 wt% bio-oil has the closest coke characteristics compared to VGO. The catalytic co-processing of bottom fuel oil (BFO) with refinery vacuum gas oil (VGO) using a commercial fluid catalytic cracking (FCC) zeolite equilibrium catalyst was carried out to ascertain its potential as a source for biofuels. The BFO used was the distillation residue from biodiesel transesterification process using waste fats and oil; being a mixture of saturated and unsaturated fatty acid methyl esters. The catalytic cracking experiments were performed in a laboratory fixed bed micro activity test (MAT) reactor at 516 °C and atmospheric pressure. As well as the VGO and BFO, three different blends were used with BFO to VGO mass ratios of 10:90, 20:80 and 50:50, and catalyst-to-oil (C/O) ratios of 3.0 – 5.7. The synergistic effect of BFO in VGO blends includes the yield of gasoline, and LPG being higher than predicted for the blends of 10 wt% BFO in VGO. Also, the formation of more CO 2 with the increase in BFO blend level suggests CO 2 production through decarboxylation reactions as a possible route. The compositions of the produced gasoline for pure VGO and 10 wt% BFO are similar as well. The cracking of 10 wt% BFO gives a higher fraction of aromatics, alkenes and naphthenes than other blends. However, some deterioration was observed when higher substitution levels of BFO were used, resulting in a decrease in the gasoline yield and higher yields of LCO, HCO and coke as predicted. Overall, co-processing BFO with VGO may be economically attractive because the BFO is obtained from waste oils and fats which are one of the under-exploited sources of biodiesel feedstocks and add value to waste management.