Investigation of the sulfur enrichment mechanism on the catalyst in the FCC process of waste tire pyrolytic oil

Abstract

The high sulfur content of polymer solid waste (like waste tires) pyrolytic oil limits its application as feedstock in fluidized catalytic cracking (FCC), while there are fewer studies on the effect of sulfur on catalysts. To explore the mechanisms of sulfur enrichment on the catalyst, the distribution characteristics of sulfur in the spent catalysts were investigated and the conversion behavior of sulfur during the FCC process of the waste tire pyrolytic oil was analyzed. The results showed that the species of sulfur in the catalyst before and after the FCC process could be well distinguished by using combined physicochemical analysis method. Sulfur mainly existed in the form of sulfates in the spent catalysts and part of the sulfur was confirmed to be bound to the catalysts matrix. The enrichment of sulfur in the catalysts was probably due to the direct and indirect migration of sulfur compounds in waste tire pyrolytic oil in the catalytic cracking stage, rather than SO2 adsorption on the catalyst in the flue gas purification stage. Furthermore, it was suggested that the sulfur-containing compounds reacted with the oxygen-containing functional groups to form sulfones and/or sulfates on the surface of the catalysts. These findings contribute to the clean utilization of solid waste and to a better understanding of the catalyst deactivation mechanism in the FCC processes.