Dehydrogenation of C6-saturated hydrocarbons over Pt catalyst

Abstract

The dehydrogenation of 2, 3-dimethylbutane, 3-methylpentane and methylcyclopentane over Pt-C catalyst was studied at low conversion levels and temperatures ranging from 400 to 480°C, under the hydrogen atmospheric pressure. The dehydrogenated products included all possible alkenes and cycloalkenes possessing the same skeletal structures as raw materials and were approximately in thermodynamic equilibrium at conversions as low as 8%. The compositions of these product mixtures observed at 460°C were: 43% 2, 3-dimethyl-1-butene and 57% 2, 3-dimethyl-2-butene; 9% 3-methyl-1-pentene, 11% 2-ethyl-1-butene, 31% 3-methyl-cis-2-pentene and 49% 3-methyl-trans-2-pentene; 68% 1-methylcyclopentene, 20% 3-methylcyclopentene, 10% 4-methylcyclopentene and 2% methylenecyclopentane in each skeletal hydrocarbons, respectively. At the initial step of the reaction, however, it was shown that 2, 3-dimethyl-1-butene, 3-methyl-1-pentene and 3-methylcyclopentene were formed beyond their thermodynamic equilibrium compositions, respectively. It was found that the rate of the dehydrogenation was influenced by the ratio of hydrogen to hydrocarbon and that in the absence of hydrogen the reaction did not proceed at all. The reaction rate increased with the molar ratios, being constant at the molar ratio of one and above. These results suggested that the hydrogen played an important role on the dehydrogenation mechanism over Pt catalyst used in the present study. © 1973, The Japan Petroleum Institute. All rights reserved.