Sulfur reduction in FCC gasoline with a commercial additive: A microactivity study

The use of advanced FCC catalysts and additives to reduce sulfur in gasoline remains the preferred option to refiners because of its economic and operation incentives. The performance of a commercial sulfur-reducing additive blended with a fresh RE-USY catalyst was assessed in a microactivity (MAT) unit using Arabian Light vacuum gas oil (VGO). The additive was evaluated at different concentrations (0-15 wt%) in terms of sulfur reduction capability and its effect on product yield structure, mainly gasoline. At 5 wt% additive, the results showed a 14 wt% reduction in total gasoline sulfur with minor effect on catalytic activity and product selectivity. Minimal reduction capability was observed towards benzothiophene (BT), which is difficult to crack and remove under cracking conditions. Upon increasing additive concentration to 10 wt%, total sulfur was reduced to 21 wt% compared to 27 wt% reduction at 15 wt% additive. At this additive concentration, aromatic sulfur compounds mainly C4-thiophenes and a portion of BT were cracked to tetrahydrothiophene, or thiophene, which were subsequently cracked to H₂S and light gases.