Relation between reduction and sulphidation process during the activation of a Co-Mo/Al2O3 hydrodesulphurization catalyst

Abstract

The course of activation at 673 and 773 K of an industrial hydrodesulphurization catalyst CHEROX 36-01 was followed gravimetrically. Reduction with hydrogen, reductive sulphidation with a H2S/H2 mixture, non-reductive sulphidation with a H2S/He mixture and sulphidation of prereduced catalysts were compared. All sulphidation procedures are much faster than the reduction alone, the latter has, however, a higher apparent activation energy. In the reductive sulphidation with H2S/H2, reduction and sulphidation take place simultaneously, sulphidation being a predominant process at the beginning of the activation, especially at 673 K. It has been shown how the two processes can be decoupled or superposed. The catalytic activity in ethylene hydrogenation develops much more slowly when the catalyst is activated only by reduction than when it is activated by reductive sulphidation, in accordance with the relative velocities of these two activation procedures. The hydrogenation activity of catalysts reduced to a different extent correlates with their oxygen chemisorption capacity at 195 K.