Role of Spill-Over Hydrogen in the Hydrogenolysis of Neopentane

Abstract

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}1{}8{ atoms/m}2{ for the most acidic support studied. Spilled-over hydrogen was inert to oxygen treatment at 100}o{C, and did not contribute to catalytic activity for neopentane or propane conversion. Instead, hydrogenolysis TOF and the amount of spilledover 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.