The influence of hydrogen pretreatment on the structural and catalytic properties of a Pt/K-LTL catalyst

A platinum, non-acidic K-LTL catalyst, reduced at 300, 450, and 600 DegC, was characterized by extended x-ray absorption spectroscopy (EXAFS), hydrogen chemisorption, hydrogen temp. programmed desorption (H2-TPD) and methylcyclopentane hydrogenolysis. Redn. at 300 DegC produces small platinum crystallites with an interfacial layer of hydrogen. Redn. at 450 DegC increases the particle size, releasing interfacial hydrogen. This irreversible hydrogen desorption is obsd. in the TPD around 300 DegC. Redn. at 600 DegC results in further growth of the platinum cluster with the loss of the remaining interfacial hydrogen. In the TPD, a second high temp. H2 desorption is obsd. at around 610 DegC. Because of the confined space within the zeolite pore, as the platinum particle size approaches the pore size, there is a redn. in hydrogen chemisorption capacity and catalytic activity compared to a particle of equiv. size on an amorphous support. [on SciFinder (R)]