Direct measurement of active sites on metal sulfide catalysts for HDS of dibenzothiophene-type sulfur compounds

Direct measurement of active sites on supported CoMo/Al₂O₃ and NiMo/Al₂O₃ sulfide catalysts was conducted through liquid-phase adsorption of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 300°C. The number of active sites on the sulfide catalysts for adsorbing organic sulfur compounds was determined from the amount of adsorbed DBT and 4,6-DMDBT under dynamic flow conditions. Simultaneous HDS of DBT and 4,6-DMDBT was also carried out under comparable conditions (300°C). Turnover frequencies (TOF) of the catalysts for HDS of sulfur compounds were calculated on the basis of the simultaneous HDS of DBT and 4,6-DMDBT. The adsorption of DBT and 4,6-DMDBT at 300°C, the same temperature as HDS reaction, provided lower number of active sites (compared to adsorption at lower temperatures) but higher TOF. The values of active sites determined for CoMo and NiMo sulfide catalysts showed a similar trend with that from the conventional oxygen chemisorption method. This liquid-phase adsorption method may become a viable option for measuring the active sites on metal sulfide catalysts. This is an abstract of a paper presented at the 231st ACS National Meeting (Atlanta, GA 3/26-30/2006).