Effect of H 2S on the stability of CoMo/Al 2O 3 catalysts during hydrodeoxygenation

Abstract

The effect of H 2S addition on the activity and the stability of CoMo catalyst during hydrotreating of phenol and anisole was studied. The presence of H 2S strongly decreased the HDO activity of the sulfided catalyst, and the ratio of the HDO reaction pathways depended on the H 2S concentration. The hydrogenolysis route to aromatics was suppressed, whereas the conversion of the hydrogenation–hydrogenolysis route to alicyclics at moderate H 2S concentrations remained the same as in the absence of H 2S. This clearly supports the presence of two types of active sites for HDO on the catalyst. Sulfidation of the catalyst was not a prerequisite for demethylation of anisole to phenol, though it increased the activity of the catalyst. Demethylation proceeded effectively even on the acidic sites of the Al 2O 3 support and on the sulfhydryl groups formed on CoMo catalyst in the presence of H 2S. In addition to desulfurization and changes in the structure of the active sulfided catalyst, the formation of coke and high molecular weight compounds on the catalyst decreased its activity but did not affect the selectivity of HDO.