TOLUENE DISPROPORTIONATION OVER NIS/SIO2-USY HYBRID CATALYSTS - EFFECTS OF SPILT-OVER HYDROGEN

Toluene disproportionation was studied on hybrid catalysts composed of physically mixed NiS/SiO2 and USY zeolite at 623 K-723 K, 1.0 MPa and W/F=4.6 g h/mol. The activity of the NiS/SiO2-USY hybrid catalyst was two times higher than that of USY in hydrogen atmosphere. Also USY hybrid catalysts containing NiS/Al2O3, NiS/TiO2 and MoS2/Al2O3 showed high activity for toluene disproportionation. The amount of deposited coke on NiS/SiO2, USY zeolite and NiS/SiO2-USY (USY content 50%) catalysts was 0.45, 16.1 and 7.6%, respectively, which suggests that coke deposited only on the zeolite. Although the rate of coke deposition was scarcely affected by the presence of NiS/SiO2, the deactivation rate was effectively suppressed by the presence of NiS/SiO2 and gaseous hydrogen. It was suggested that hydrogen species supplied by hydrogen spillover at NiS sites and inter-particle migration promote the turnover frequency of toluene disproportionation at Bronsted acid sites on USY zeolite surface.