ABSTRACT
The addition of various amounts of H2S during the reaction of thiophene, cyclohexene and 2,6-dimethylaniline model compounds was used to assess the functionalities of an industrial CoMo /Al2O3 hydrotreating catalyst operating at 4 MPa total pressure. The catalyst was sulfided either by H2S/H2 or DMDS (dimethyldisulfide)/H2. Thiophene and cyclohexene were converted simultaneously at 280°C, while 2,6-dimethylaniline was studied separately at 300°C. The alkylaniline reaction followed three parallel routes which were influenced only up to 1 mol% added H2S: hydrogenation of the benzenic ring and direct C-N bond rupture to m-xylene were strongly inhibited, whereas acidic disproportionation was enhanced. H2S affected thiophene and cyclohexene differently: in the triangular reaction network of thiophene, hydrogenation of thiophene to the intermediate thiolane appeared promoted, and the C-S hydrogenolysis steps were depressed; cyclohexene hydrogenated to cyclohexane much more slowly with H2S, and reacted significantly to cyclohexanethiol. Thiolane and cyclohexanethiol acted as strong inhibitors. Sulfiding the catalyst with DMDS/H2 instead of H2S/H2 yielded more acidic and C-S hydrogenolysing properties but less hydrogenating capabUity. The effect of H2S on the functionalities of the catalyst is discussed in terms of active species arising from dissociated H2 and H2S.
