Phase tuning of ZrO2 supported cobalt catalysts for hydrodeoxygenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran under mild conditions

Crystal structure of catalyst support has great influence on its surface and electronic properties. Thus, tuning the crystal phase may adjust the catalytic activity. Herein, we prepared a series of monoclinic, tetragonal and mixed phase of Co/ZrO2 catalysts, denoted as Co/m-ZrO2, Co/t-ZrO2 and Co/Mix-ZrO2. They showed different hydrogenation and hydrogenolysis activities in conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF). The characterization and catalytic performance indicated that the interaction between cobalt and t-ZrO2 resulted in cobalt electron-deficiency and higher concentration of Zr(III) species, which contributed to the higher hydrogenation activity of carbonyl on Co/t-ZrO2 than Co/m-ZrO2. While the hydrogenolysis of COH group showed higher efficiency on Co/m-ZrO2, which was determined by the acid concentration on the surface of catalysts. The combination of both high hydrogenation and hydrogenolysis activities in Co/Mix-ZrO2 achieved the highest yield of DMF (90.7 %) under mild conditions of 130 °C and 1 MPa H2.