The Effect of Hydrogen Partial Pressure on Methylcyclopentane Ring Opening

Article abstract of DOI:10.1006/jcat.1995.1035

The ring opening of methylcyclopentane (MCP) over well-chacterized Pt/SiO2 (EUROPT-1), Pt/γ-Al2O3, and Pt/K-LTL catalysts was studied as a function of hydrogen partial pressure and reduction temperature.The MCP ring opening selectivity did not change in the range of H2:MCP ratios studied (8-200).The turnover frequency (TOF) went through a maximum at the H2:MCP ratio increased.The maximum TOF of the Pt/γ-Al2O3 after reduction at 450 deg C is about three times higher than the maximum specific activity of the Pt/K-LTL and Pt/SiO2 catalysts.The H2:MCP partial pressure ratio at which maximum activity is obtained increases in the Pt/K-LTL < Pt/γ-Al2O3 < Pt/SiO2.This sequence is rationalized using reported adsorption energies of H2 and assuming a decreased adsorption energy of MCP on Pt/K-LTL.The data can be described with a reaction mechanism that includes the cleavage of a C-C bond as the rate determining step.Kinetic analysis of the changes in specific reaction rate as a function of the H2:MCP ratio showed that the reaction proceeds through multiple adsorbed MCP species.The surface reaction rate is more than an order of magnitude higher for the Pt/γ-Al2O3 catalyst than for the Pt/K-LTL catalyst, but decreases with increasing reduction temperature for both catalysts.