A Novel Synthesis of Cyclohexanol Derivatives by the Catalytic Hydrogenation of Benzene with Acid Additives

Abstract

The hydrogenation of benzene over a platinum group metal in the presence of various strong acids was carried out. Cyclohexanol derivatives (C6H11X, X = OH, OAc, Cl, Br) were found to be produced by the catalytic hydrogenation of benzene with acid additives. The following two sequences of adsorption strength were observed between platinum metals (adsorbent) and additive reagents (adsorbate) : When a weak adsorbate, such as acetic acid or water, was used as an additive reagent, ruthenium, the strongest adsorbent, exhibited the best selectivity. When hydrogen chloride, a strong adsorbate in the sequence (II), was used an additive reagent, palladium or rhodium, moderately strong adsorbent, exhibited excellent selectivity. By the reaction of 2 ml of benzene, 5 ml of 35% HCl and 0.2 g of 5% Pd/SiO2, under 10 atm-G (P atm-G = 1.013(P + 1) × 105 Pa) hydrogen at 100 °C for 20 h, 8.4% of the yield of chlorocyclohexane was obtained at 64.2% of the selectivity (13.1% of the conversion of benzene).