Hydrogenative transformations of methylcyclobutane over silica-supported Rh, Ni, Pt and Pd catalysts at different temperatures

The effect of temperature on the transformations of methylcyclobutane over silica-supported Rh, Ni, Pt and Pd catalysts was studied in a wide temperature range (323-723 K) in a pulse system. The transformations taking place were cracking (hydrogenolysis), hydrogenative ring opening and ring enlargement. The reaction directions were found to depend strongly on the nature of the metal. Over Pt and Pd, hydrogenative ring opening was the main reaction at all temperatures studied. In contrast, Rh and Ni promoted hydrogenolysis at high temperature, and this reaction occurred exclusively above 573 K. The selectivity data on the ring-opening reaction were different over Pt and Pd from those over Rh and Ni. The ring-opening selectivity (ratio of isopentane to both ring-opened products) was close to statistical over Pt and Pd, while sterically less hindered bond scission was the main direction of the ring opening over Rh and Ni.