Hydrocracking of Cyclohexane and Methylcyclopentane over a Cobalt-Alumina Catalyst

Abstract

Ring opening of cyclohexane and methylcyclopentane (MCP) catalyzed by a cobalt-alumina catalyst was investigated at a hydrogen pressure of 10 kg/cm², in the temperature range from 230 to 300°C. MCP can react at a temperature by 30°C lower than cyclohexane (Fig.1). The major product from cyclohexane was methane with relatively small amount of C₂-C₆ normal and branched paraffins, MCP and benzene (Table 1). At lower temperature, the major products from MCP were methane and hexane isomers which consisted of hexane, 2-methylpentane (2-MP) and 3-methylpentane (3-MP). As the temperature increased, the selectivity for methane production increased (Table 3). The ratio of 3-MP with 2-MP in product was from 0.1 to 0.2 for cyclohexane reaction and 0.8 to 0.9 for MCP reaction (Tables 1, 3). The difference in the values between cyclohexane and MCP has been discussed in terms of the specific modes of their activated adsorption on the catalyst (Fig.2). It is suggested that the rate-determining step of hydrogenolysis of cyclohexane is dehydrogenation process to form activated adsorption species, and a reaction scheme for ring opening of cyclohexane is proposed (Fig.3).