ROLE OF SPILL-OVER HYDROGEN IN THE HYDROGENOLYSIS OF NEOPENTANE

A series of Pt/LTL zeolite catalysts with varying Pt loading and support acidity was studied by hydrogen temperature-programmed desorption (TPD) and reaction of neopentane and propane. Specific desorption peaks in the TPD were associated with hydrogen spilled-over onto the support. The ability of the spilled-over hydrogen to migrate on the support surface was limited to approximately 35 nm from the platinum cluster. Saturation capacity for spilled-over hydrogen was related to the support acidity/basicity, with a maximum of about 10(18) atoms/m(2) for the most acidic support studied. Spilled-over hydrogen was inert to oxygen treatment at 100 degrees C, and did not contribute to catalytic activity for neopentane or propane conversion. Instead, hydrogenolysis TOF and the amount of spilled-over hydrogen were mutually dependent on support acidity/basicity. Both declined with increasing K/Al ratio of the support, and continued to decline even for basic supports with K/Al ratios greater than 1. The continued decline in activity for K/Al > 1 indicates than the metal-support interaction is not dependent on acidic hydroxyls.