Influence of the support on the selective ring opening of methylcyclohexane and decalin catalyzed by Rh-Pd catalysts
Résumé
Rh Pd catalysts supported on Al2O3, SiO2 and SiO2 Al2O3 (SIRAL 40) were studied for methylcyclohexane (MCH) and decalin ring opening reactions. It was found that the Rh/Pd atomic ratios were similar to the theoretically expected one and the metal dispersion values varied between 30 and 50%. On bimetallic catalysts supported on Al2O3 and SiO2, Pd and Rh were present mainly in the form of monometallic particles, whereas a heterogeneous distribution constituted of large Pd particles and small bimetallic ones were observed on SIRAL 40. Total and Bronsted acidities followed the order: SIRAL40 Al2O3 > SiO2. Al2O3 supported catalysts were the most suitable for MCH ring opening, while the opening of decalin was favored by using SiO2 Al2O3 (SIRAL 40). The catalysts supported on SiO2 produced mainly dehydrogenated compounds. The higher total and Bronsted acidities of SIRAL 40 series had a great impact on the opening of bicyclic naphthenes, whereas the metal function of the catalyst and the hydrogenolytic activity of Rh had a major role during MCH reaction. Using bimetallic catalysts in the MCH reaction decreased the formation of cracking and dehydrogenated products, and the selective formation of RO products could be optimized by tuning the working temperature