New aspects of catalytic functions on sulfide catalysts

The influence of Co on the acidic properties (Lewis and Bronsted) of molybd enum sulfide catalyst were determined by infrared studies of adsorbed pyrid ine or 2,6-dimethylpyridine, These studies show that the promoter addition increases the strength of the Lewis sites and the number of Bronsted sites, These results are correlated to those obtained for dibenzothiophene conver sion. For this reaction, it was observed that the influence of the promoter is very different for the two different routes involved in the reaction sc heme. Consequently, the role of the promoter is not only to increase the nu mber of sulfur vacancies but also to modify the acid-base properties of the catalyst. (C) 2001 Elsevier Science B,V, All rights reserved.