Catalytic hydrogenation of cyclohexene3. Gas-phase and liquid-phase reaction on supported palladium

Abstract

The hydrogenation of cyclohexene was studied in both gas and liquid phases on six different palladium catalysts supported on silica gel and alumina between 264 and 308 K at hydrogen pressures from 4 to 89 kPa, cyclohexene partial pressures from 0.46 to 1.5 kPa, and cyclohexene concentrations from 0.15 to 3.0 M . Under these conditions the turnover frequency is independent of particle size (1.5 to 10 nm) in both liquid and gas phases, of the nature of the support, and of the nature of nonaromatic solvents (methanol, n -heptane, ethyl acetate, and cyclohexene). The order of reaction was one-half with respect to hydrogen for the reaction in both liquid and gas phases and zero with respect to cyclohexene partial pressure (gas phase) or with respect to cyclohexene molar concentration (liquid phase). At the same temperature and hydrogen pressure, the turnover frequency was about twice as high in the gas phase as in the liquid phase.