Discovery of a new role of spillover hydrogen emitted by sulfided catalysts: creation of acidic sites on amorphous silica-alumina

Abstract

Sulfided CoMo/SiO2, as a source of spillover species (H-so and D-so) permits an exchange of deuterium with the hydroxyl groups of silica-aluminas (6.5, 12 or 60% wt Al2O3). The exchange was followed by FTIR using a simple physical mixture of sulfided CoMo/SiO2 with the silica-aluminas. These measurements come in complement to our previous publications showing a considerable synergy between CoMo/SiO2 and silica-aluminas in the selective cracking of diphenyl methane to benzene and toluene in the presence of H-2 and H2S. This was interpreted as due to the action of H-so with the surface of the silica aluminas to create Bronsted sites. The present results prove directly this migration of D-so from CoMo/SiO2 to the silica-aluminas. The creation of Bronsted sites by H-so is possible in the absence of H2O or H2S, but is accelerated in the presence of these molecules. The whole picture thus obtained leads to propose a new mechanism for diphenylmethane hydrocracking in the presence of sulfide catalysts.