On the effect of a high reactive sulfur species on sulfur reduction in gasoline

Varying solutions are available for reducing the amount of sulfur contained in gasoline from fluid catalytic cracking units (FCCUs). However, the use of selective catalysts or additives can be the easiest to implement and potentially represent the most cost effective solution. In order to improve overall performance a better understanding of the effects of the feed properties on catalyst activity is needed. In this work we study the effect of a high reactive sulfur compound on the sulfur distribution in cracked products. Experiments were carried out in a fixed fluidized bed reactor using a REUSY equilibrium catalyst (Ecat), a commercial additive for gasoline sulfur reduction and an industrial feed spiked with hexane-2-thiol. The acidity of the materials was studied using FTIR spectra of chemisorbed pyridine. With spiked feeds both Ecat and the additive exhibited lower cracking activity indicating that the hexane-2-thiol had a strong poisoning effect on the materials acid sites. The effect of the type of acidity of the materials used is discussed and a selective adsorption of hexane-2-thiol on Lewis acid sites is proposed to explain the observed results. Similar trends were generated with a high sulfur feed derived from a Mayan crude oil thus leading to the conclusion that the presence of nonthiophenic sulfur compounds in the feed might have a strong negative effect on sulfur reduction. The potential use of an alumina material, possessing Bronsted and Lewis acidity, for sulfur reduction is presented and discussed.