Development of deep hydrodesulfurization catalysts I. CoMo and NiMo catalysts tested with (substituted) dibenzothiophene

The applicability of CoMo and NiMo based catalysts for the deep hydrodesulfurization (HDS) of diesel fuel was evaluated from gas phase experiments with model reactants. The reactivity of the latter decreased in the order DBT (dibenzothiophene) > 4MDBT (4-methyl dibenzothiophene) >> 4E6MDBT (4-ethyl, 6-methyl dibenzothiophene), caused by the increase in steric hindrance in the direct hydrogenolysis route. An easier (independent) reaction pathway was possible on catalysts with increased hydrogenation activity: when NiMo was supported on amorphous silica-alumina (ASA) instead of alumina, the activity for 4MDBT and especially 4E6MDBT HDS was enhanced. The activity for 4E6MDBT HDS in the presence of 0.2% H2S was considered as indicative for the performance under deep desulfurization conditions: NiMo/ASA had the highest activity, followed by a CoMo/activated carbon catalyst and an optimised CoMo/Al2O3 co-impregnation catalyst. All three catalysts were slightly more active than a commercial CoMo/Al2O3 catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.