M-XYLENE TRANSFORMATION OVER NIS AL2O3-USY HYBRID CATALYSTS - EFFECTSOF HYDROGEN SPILLOVER/

m-Xylene transformation (isomerization and aromatics hydrogenation) on Y zeolite (USY) was markedly promoted by the physically mixed sulfide d nickel supported on Al2O3 (NiS/Al2O3) in the presence of hydrogen, w hile NiS/Al2O3 showed no activity for these reactions, and coke deposi tion on USY and m-xylene disproportionation were not affected by NiS/A l2O3. Also, under nitrogen atmosphere, all reactions were unaffected b y NiS/Al2O3. Studies of H-D exchange of OH groups on USY zeolite with gaseous D-2 by FT-IR spectroscopy showed that the ratio of the exchang e rate of USY, Al2O3-USY and NiS/Al2O3-USY catalyst was 3.8, 1 and 14. 5, respectively, at 523 K and 62.5 kPa D-2. It was concluded that the H-D exchange of OH groups (including Bronsted acid sites) on USY surfa ce in the NiS/Al2O3-USY catalyst was mainly due to hydrogen spillover through NiS site dissociating gaseous hydrogen, with the spillover hyd rogen migrating to the USY surface, This probably promoted m-xylene is omerization and helped maintain a higher activity of hydrogenation for aromatic rings on the zeolite.