Chemisorption of oxygen and hydrogenation of ethylene on sulphided Co-Mo/Al2O3 catalyst. Effect of activation process

Oxygen chemisorption by pulse dynamic method at room temperature and the activity for ethylene hydrogenation at 300 °C in a flow regime were determined for Co-Mo/Al2O3 catalyst CHEROX 36-01 sulphided by a H2S/H2 (1:10) mixture at 400 °C. The measurements were carried out either immediately after sulphidation or after subsequent reduction of the sulphided catalyst by hydrogen. The chemisorption of oxygen was measured both prior to and after the catalytic reaction. In addition, the reactivation of the catalyst was examined after its passivation by oxygen chemisorption. The reactivation was effected either by resulphidation or by reduction with hydrogen at 400 °C, on repeated reactivation also by combination of both procedures, variables being the time of activation and reactivation steps. The results are discussed from the standpoint of the structure and interrelation between active sites for oxygen chemisorption and catalytic, especially hydrogenation reactions. Formation of coordinately unsaturated sites and SH groups is emphasized. The reasons of possible failures in correlations between chemisorption capacity for oxygen and catalytic activity are mentioned.