Hydrogen-free hydrogenation of furfural to furfuryl alcohol and 2-methylfuran over Ni and Co-promoted Cu/γ-Al<inf>2</inf>O<inf>3</inf> catalysts

Abstract

Catalytic transformation of furfural to furfuryl alcohol and 2-methylfuran without H2 supply toward transfer hydrogenation process using 2-propanol as a H2 source was systematically investigated over the bimetallic NiCuAl and CoCuAl catalysts in comparison with the monometallic CuAl, NiAl, and CoAl catalysts. The XRD analysis confirmed the generation of Ni-Cu and Co-Cu alloys after the reduction in presence of H2. The interaction between Cu and Ni or Co resulted in a simplicity of the reduction behavior of Ni and Co species observed in H2-TPR experiments. It was evident from pyridine adsorption FTIR analysis that the formation of bimetallic Ni-Cu and Co-Cu alloys apparently improved the stronger Lewis acidic sites. The influences of reaction temperature and time were examined and optimized to maximize the yields of furfuryl alcohol and 2-methylfuran. The highest two major products yield and selectivity with lower by-products were obtained over the NiCuAl and CoCuAl catalysts compared with the CuAl and NiAl catalysts. The superior performance of the bimetallic catalysts was attributed to the stronger Lewis acidic centre on the catalyst surface. The CoCuAl catalyst was found to have lower catalyst deactivation and carbon deposition among the CuAl and NiCuAl catalysts under H2-free atmosphere.