Ru-Zn supported on hydroxyapatite as an effective catalyst for partial hydrogenation of benzene

Design and preparation of efficient and greener catalytic systems for partial hydrogenation of benzene to cyclohexene is an interesting topic in green chemistry. In this work, Ru and Ru-Zn catalysts supported on hydroxyapatite (HAP), which is nontoxic and abundant in nature, were prepared via the simple ion-exchange method. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron spectroscopy (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption methods. The influences of Ru/Zn molar ratio, reaction temperature, pressure, reaction time, and amount of modifier NaOH on the partial hydrogenation of benzene were studied in detail. It was demonstrated that metallic nanoparticles of less than 2 nm were dispersed uniformly on the surface of the HAP, and the bimetallic Ru-Zn/HAP catalysts showed high activity and selectivity. The yield of cyclohexene could reach 33% over Ru-Zn/HAP at the optimized conditions, and the catalyst could be reused at least four times without obvious loss of the activity and selectivity.