Ring opening of methylcyclopentane on alumina-supported Rh catalysts of different metal loadings

Article abstract of DOI:10.1006/jcat.2000.2826

The hydrogenolytic ring opening of methylcyclopentane (MCP) was studied on Rh/Al₂O₃ catalysts (prepared by the incipient wetness process) with varied metal loadings (0.3, 3, and 10%) and altered reduction temperatures, i.e., low-temperature range (573 K, LTR) and high-temperature range (973 K, HTR). The catalysts exhibited a ″selective″ ring-opening mechanism for MCP. Strong dependence was observed in the distribution of ring-opening products as a function of hydrogen pressure and temperature with 10Rh and 3RhHTR. However, 0.3Rh, 3RhLTR catalysts showed random fragment production from each ring-opening surface species. The selectivity depended on the reaction temperature, hydrogen pressure, and catalyst preparation. Changes in metal loading and pretreatment can cause interconversion between the two forms of Rh. Since the changes in TPR and catalytic behavior with metal loading and pretreatment were parallel, the changes in product distribution were ascribed to different morphologies of Rh particles. The results agreed well with earlier assumptions that selective ring opening involves an associative flat-lying intermediate that can be a common surface intermediate for single and multiple C-C bond cleavage.