Enhanced Catalytic Performance of Rhodium-Loaded EWT Zeolite Catalysts: Synthesis, Metal Dispersion, and Structural Effects

Cyclohexanol is a vital raw material in the synthesis of various chemicals and serves as a key intermediate in nylon production, thereby playing a crucial role in the chemical industry. Herein, the preparation and catalytic performance of Rh/EWT zeolite are reported, featuring highly dispersed Rh sites on EWT frameworks. This catalyst exhibits high reactivity in the selective hydrogenation of phenol to cyclohexanol. The findings indicated that selectivity is influenced by the Rh particle size on the support, with Rh particles smaller than 5.0 nm significantly enhancing cyclohexanol selectivity. Time-resolved phenol conversion studies reveal cyclohexanone as the initial product. The encapsulated Rh catalyst accelerates the subsequent conversion of cyclohexanone to cyclohexanol. Additionally, it is observed that cyclohexanol selectivity initially decreases and then increases with rising temperatures between 60 and 120 °C and is proportional to hydrogen pressure. Moreover, it is demonstrated that the catalytic performance differences originate from variations in Rh's electronic properties, which are determined by particle size differences between the zeolite-supported catalysts. Overall, this work underscores the breakthrough potential of Rh/zeolite catalysts, composed of highly dispersed Rh species on zeolites, in hydrogenation processes.