Effect of spillover hydrogen on amorphous hydrocracking catalysts

The cracking of diphenylmethane on mixtures of sulfided CoMo/SiO2 and amorphous silica-alumina particles was studied. The products were benzene and toluene. The addition of CoMo/SiO2 to silica-alumina strongly increases the cracking rate and the OH-OD exchange, and diminishes the amount of coke formed. This is interpreted by a spillover of dissociated H2 (or D2) onto the silica-alumina, with spillover hydrogen forming Brönsted sites and reacting with coke precursors, and spillover deuterium exchanging with the hydroxyls.