Hydrogenation of Benzene to Cyclohexylbenzene with Potassium- Graphite Lamellar Compound Catalysts (C₈K or C₂₄4K)

Abstract

Hydrogenation of benzene to give cyclohexylbenzene over potassium-graphite lamellar com-pound catalysts (C_nK, n=8 or 24) was investigated at 200-250° C and under 50-100 kg/cm²-H₂. By-products were cyclohexane and dicyclohexylbenzenes. To produce cyclohexylbenzene catalyzed by CK was found to be due to a characteristic property of lamellar compound cata- lysts C_nK because in the above case catalyzed by the physical mixture of potassium and graphite, cyclohexane was almost selectively obtained. Furthermore, higher ratio of cyclohexylbenzene/ cyclohexane was obtained with Ca, K than that with C8K and these ratios were 7 and 0.4, respectively at 200° C and under 100 kg/cm²-H₂.
X-ray analysis of C_2CK during the initial stage of hydrogenation suggested that absorbed benzene occupied the space of CI, K-layers without being replaced by hydrogen. On the other hand, Cal< changed into somewhat complex species of catalyst, which seemed to be produced by the interaction of C8K-hydride with benzene. Selectivity of CK catalysts to produce cyclohexylbenzene or cyclohexane was discussed in terms of the absorption of benzene or hy- drogen by CnK-layers. Results of hydrogenation of some related hydrocarbons such as toluene and biphenyl were also described.