Highly efficient Cu-based catalysts for selective hydrogenation of furfural: A key role of copper carbide

Copper catalysts showed excellent CO hydrogenation selectivity, but poor ability of hydrogen dissociation. Herein, a strategy to improve the activity of a Cu-based catalyst is developed by thermal treatment of Cu(OH)2 at 100 °C with C2H2/Ar (0.5 vol%) followed by H2 reduction at 300 °C. By means of X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), it was revealed that CuxC crystallites, in addition to Cu crystallites, were present in the prepared catalysts. In furfural hydrogenation at 60 °C and 1.0 MPa, the CuxC-containing catalyst showed significantly higher activity than the Cu counterpart prepared from the same precursor by H2 reduction at 300 °C. The introduction of ZnO improved the dispersion, and thus led to enhanced catalytic performance. The CuxC-Cu-ZnO catalyst with Zn/Cu molar ratio of 0.5 showed considerably high hydrothermal stability in a 70-h run, with furfural conversion of >99.0% and the furfuryl alcohol selectivity of 100%.