IN-SITU POISONING OF THE THIOPHENE HYDRODESULFURIZATION ACTIVITY OF CARBON-SUPPORTED TRANSITION-METAL SULFIDE CATALYSTS BY PHOSPHORUS

Carbon-supported transition metal sulfide catalysts, prepared by pore volume impregnation of an activated carbon support with aqueous soluti ons of first, second and third row transition metal salts (Group V-VII I), drying and in situ sulfidation, were tested in thiophene hydrodesu lfurization (723 K, 0.1 MPa). In the poisoning experiments a bed of ph osphorus compound-containing carbon was placed upstream of the catalys t bed. Under the sulfiding and reaction conditions the phosphorus comp ound was volatilized and transported to the catalyst bed where it coul d affect the catalytic properties of the active metal sulfide phase. T his poisoning effect was different for the thiophene conversion to hyd rocarbons and butene hydrogenation, and depended on the transition met al sulfide. Group VIII transition metal sulfides were rather resistant towards the poisoning by the phosphorus compound. Only the hydrodesul furization activity of the carbon-supported nickel catalyst was promot ed in the presence of phosphorus. This beneficial effect of phosphorus on nickel might also explain the gain in activity for the commercial Al2O3-supported Ni-Mo-P catalysts.