Efficient hydrogenation of cyclohexyl acetate to cyclohexanol with Cu–Zr catalysts

Abstract

The hydrogenation of acetic acid-derived cyclohexyl acetate (CHA) is becoming a safe, efficient and promising route for the production of cyclohexanol (CHOL), an important chemical to produce ε-caprolactam. In this work, Cu–Zr catalysts were prepared via different methods for the hydrogenation of CHA. The results showed that a Cu₃Zr₇-SG catalyst prepared by the sol–gel (SG) method was superior to Cu₃Zr₇-CP and Cu₃Zr₇-IM catalysts prepared by the coprecipitation (CP) and impregnation (IM) method, respectively. The Cu₃Zr₇-SG catalyst showed 97.4% CHA conversion and 95.5% selectivity to CHOL along with 96.3% selectivity to ethanol at 250 °C under 3 MPa of H₂. Moreover, the Cu₃Zr₇-SG catalyst showed a mass specific activity of up to 29.8 g_CHA g_Cu⁻¹ h⁻¹, higher than other Cu-based catalysts under similar conditions. Based on detailed characterization studies, it was found that the larger weak acid sites, more weak and moderate basic sites, higher Cu⁺/(Cu⁰ + Cu⁺) and oxygen vacancies on the surface of the Cu₃Zr₇-SG catalyst were beneficial for the hydrogenation of CHA.