Selective dehydrogenation of cyclohexanol to cyclohexanone over biomorphic Cu/ZnO catalysts

Abstract

A high surface area ZnO support (HSA-ZnO) has been fabricated in a unique thermal decomposition process using broken rice grains as a sacrificial template, zinc acetate trihydrate as ZnO precursor. As-prepared ZnO support exhibited a surface area of 145 m2/gm, which is six times higher than the commercial ZnO. Further, copper-supported HSA-ZnO catalysts with different copper loadings (4, 8, 12 and 16 wt%) were prepared by using wet impregnation method and characterized by physicochemical techniques such as X-ray diffraction (XRD), Thermal gravimetric analysis(TGA), BET surface area, CO2 temperature programmed desorption of (CO2-TPD), temperature programmed reduction(TPR) and N2O pulse chemisorption measurements. The catalytic activity of all the prepared catalysts were tested in dehydrogenation of cyclohexanol in a continuous flow reactor. A variety of reaction factors were examined, including the impact of temperature, the influence of copper loadings, and the catalysts stability. Lab-made HSA ZnO presented better properties than the commercial and the one without sacrificial template preparation. Among all the catalysts, 12 wt% Cu/HSA-ZnO catalyst exhibited the highest conversion (75%) and cyclohexanone selectivity (89%). The high activity and stability of optimal 12 wt% Cu-loaded catalysts are due to highly dispersed copper particles, better reducibility, and the strong interactions between the Cu particles and rice-derived ZnO support.