Combining a Supported Ru Catalyst with HBeta Zeolite to Construct a High-Performance Bifunctional Catalyst for One-Step Cascade Transformation of Benzene to Cyclohexylbenzene
Yihui Song, Ming Zhang, Guoli Fan, Lan Yang, Feng Li
Abstract
Usually, the one-step benzene hydroalkylation to produce cyclohexylbenzene (CHB) can proceed on metal-acid bifunctional catalysts. In this work, we developed a highly active mixed catalyst composed of the Ru-based hydrogenation catalyst (Ru–Zn) and metal-free HBeta alkylation zeolite for one-step highly efficient hydroalkylation of benzene to CHB under batch-operation or continuous-flow conditions. It was shown that the partial hydrogenation of the benzene generated cyclohexene (CHE) intermediate on the Ru–Zn catalyst and subsequently the alkylation of benzene with CHE produced CHB on the HBeta zeolite. The as-combined mixed Ru–Zn|HBeta catalyst showed an excellent catalytic hydroalkylation performance with a CHB yield of ∼44% under batch-reactor reaction conditions (200 °C, 4.0 MPa), higher than those currently reported in patents and the literature. Furthermore, a high CHB yield of 39.1% was attained under milder continuous-flow operating conditions (150 °C, 2.0 MPa). It was revealed that surface acidity and the balance between metal sites on the Ru–Zn catalyst and acid sites on the HBeta were key factors regulating the formation of target CHB produced on Ru–Zn|HBeta mixed catalysts. The present findings offer a promising and high-performance catalyst for one-step hydroalkylation of benzene to produce CHB by a simple combination of the Ru-based catalyst with another zeolite catalyst without complicated construction of double metal and acid sites on the single catalyst.