Selective hydrodesulfurization of FCC naphtha over carbon coated alumina supported CoMoS catalysts

Herein, carbon coated alumina (C@Al2O3) samples obtained by chemical vapor deposition of ethylene have been proposed as supports for CoMoS hydrodesulfurization (HDS) catalysts of full-range FCC naphtha. Various degree of support graphitization (from 30 to 74%) was achieved by changing the treatment time of alumina in ethylene from 15 to 120 min. The influence of the alumina graphitization on the state and morphology of the sulfide component and catalytic performance of CoMoS catalysts has been studied in detail. The dispersion of sulfide particles and the CoMoS phase content is found to increase with the growth of the graphitization degree. This is accompanied by an increase in the selectivity of the CoMoS/C@Al2O3 catalysts in the HDS of FCC naphtha, whereas the reverse trend is observed for the activity. Thus, by changing the support graphitization degree, the selectivity of CoMoS catalysts in FCC naphtha HDS can be tuned. An increase in the support graphitization degree to 74% made it possible to reduce the sulfur content in FCC naphtha from 238 to 10 ppm, with a total loss in octane number of less than 1.5 units, which demonstrates the great potential of CoMoS/C@Al2O3 catalysts for commercial application in selective HDS of FCC naphtha.