Continuous hydrogenation of hydroquinone to 1,4-cyclohexanediol over alkaline earth metal modified nickel-based catalysts

Effects of different alkaline earth metals (Mg, Ca, Sr) on the nickel-based catalysts for the continuous hydrogenation of hydroquinone were studied, and it was found that the by-products, characterized by GC-MS analysis, were mainly composed of phenol and cyclohexanol. The conversion of hydroquinone was 99.2% and the selectivity to 1,4-cyclohexanediol was above 96.7% over a Ni-Sr/gamma-Al2O3 catalyst at 160 degrees C and 2.0 MPa hydrogen pressure. The high selectivity of the Ni-Sr/gamma-Al2O3 catalyst was ascribed to its weak acidity due to the formation of SrCO3. confirmed from XRD and NH3-TPD characterizations. Moreover, it was proposed that SrCO3 can disperse and stabilize the active Ni species, making the catalyst stable during the 90 h service life test. (C) 2011 Elsevier B.V. All rights reserved.