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Abstract:
A 6.3% Pt/SiO2 catalyst has been pretreated in hydrogen between 483 and 973 K and in air at 723 K. Particle size distribution of platinum after various treatments was monitored by XRD; its surface composition by XPS. The removal of surface carbon is complete in oxygen atmosphere only. These results are compared with the reaction of methylcyclopentane (MCP) model compound after analogous pretreatments. Ring opening is the main reaction; its selectivity is rather sensitive to catalyst pretreatment. XRD shows that the reduction of platinum is complete in hydrogen and sintering occurs likely at the highest temperatures only. The effects in selectivity are attributed, therefore, to various levels of carbon impurity as well as to slight sintering. A possible metal-support boundary effect may only manifest itself on EuroPt-1 pretreated in oxygen.
