Preparation, characterization, and catalytic activity of molybdenum carbide or nitride supported on platinum clusters dispersed in EMT zeolite

Bimetallic Pt-Mo catalysts were prepared by vapor deposition of Mo(CO)(6) o nto nanometer size platinum particles previously dispersed an EMT zeolite. Subsequent decomposition of the Mo precursor formed a supported molybdenum carbide phase whereas reaction of the precursor with ammonia formed a suppo rted nitride phase. Results from high-resolution transmission electron micr oscopy and X-ray absorption spectroscopy at the Mo K and Pt Lm edges showed conclusively that highly dispersed particles containing both transition me tals were synthesized by the vapor deposition method. Coverage of Pt by Mo suppressed both the total capacity for dihydrogen chemisorption and the cat alytic activity for benzene hydrogenation. However, compared to monometalli c Mo carbide or nitride clusters supported on EMT zeolite, the bimetallic c atalysts were much more active in the catalytic reactions of n-heptane at 6 23 K. The low thickness of the carbide or nitride phase (about 0.3 nn) allo wed for a synergistic influence of the Mo phase on the small areas of expos ed Pt and/or a direct activation of the nitride or carbide for catalysis. ( C) 1999 Academic Press.