KINETICS OF HYDROGENATION OF CYCLOALKENES ON PALLADIUM-ALUMINA CATALYSTS

Reaction rates for the hydrogenation of bicyclo [2.2.1] hep tene, cyclopentene, cyclohexene, cycloheptene, and cyclooctene from solution in cyclohexane on alumina-supported palladium catalysts are reported. The observed rates at 25.0° near 1 atm are first order in catalyst but they exhibit a fractional order dependence both upon the concentration of the cycloalkene and also upon the hydrogen pressure. The apparant activation energy for cyclohexene is 5.7 × 0.5 kcal mol-1. The fractional order dependence of the rates upon the cycloalkene concentration is explained in terms of a reversible chemisorption of the alkene, while the fractional order dependence upon hydrogen pressure is viewed to reflect an intrinsic zero-order dependence upon which is superimposed a first-order pore diffusional process involving hydrogen. © 1969, American Chemical Society. All rights reserved.