Construction of Cu-M-Ox (M = Zn or Al) Interface in Cu Catalysts for Hydrogenation Rearrangement of Furfural

Rational design of promising Cu catalyst requires better understanding of the Cu–support perimeter for reactions such as hydrogenation rearrangement of furfural─a pivotal and alternative transformation to produce cyclopentanol. Herein, a series of Cu catalysts with constructed Cu-M-Ox interfaces (M = Zn or Al) have been synthesized. In freshly reduced Cu/ZnO-Alx samples, aluminum species was enriched surrounding Cu. The Cu-Al-Ox contacting interface was formed, and the CuAl2O4 spinal structure was detected as a combining consequence only if Zn and Al species coexisted. The specific metal–support synergistic interaction and Cu-Al-Ox contacting interface simultaneously aroused the enhanced redox property and large number of surface acid sites, facilitating the adsorption/activation of hydrogen and reactants. During the reaction, Al2O3 retreating from the Cu-Al-Ox interface caused the replacement of Cu-Al-Ox by new Cu-Zn-Ox interface, which was directly correlated with the irreversibly changed chemical structure and decreased cyclopentanol yield, although the furfural conversion was well sustained. In this work, we confirmed that supported copper catalysts were competent for the activation and conversion of furfural, with the turnover frequency reaching 28.1 h–1 by the Cu/ZnO-Al3 sample at temperatures as low as 90 °C. The further transformation of cyclopentanone to cyclopentanol was largely depending on the maintenance of a steady Cu-Al-Ox contacting interface.