ON THE HYDROGENATION AND DEHYDROGENATION OF CYCLOHEXENE AND 1,3-CYCLOHEXADIENE ON TRANSITION METALS BY GAS CHROMATOGRAPHIC PULSE TECHNIQUE.

Abstract

Reactions of benzene, 1, 3-cyclohexadiene, cyclohexene and cyclohexane have been investigated on reduced transition metals by using a gas chromatographic pulse technique. Main interest was placed on the applicability of this technique to a prompt evaluation of the selectivity; the destination of the intermediates in benzene-cyclohexane reaction, when injected in a stream of hydrogen, has been determined by taking advantage of the technique. The hydrogenation selectivity was found to be of the sequence Ni<Co<Fe, being reversed with the conversion activity of 1, 3-cyclohexadiene or of cyclohexene to give cyclohexane and benzene. Quite synonymously the dehydrogenation selectivity was in parallel with the conversion activity. The temperature dependency of the relative selectivity was analyzed on the basis of the steady state approximation of the hydrogenation-dehydrogenation reaction. The general trend of the hydrogenation-dehydrogenation reaction of 1, 3-cyclohexadiene and of cyclohexene has been successfully explained with the potential energy level diagram of the reaction.