Mesoporous nickel-cobalt oxide for efficient liquid-phase benzyl alcohol oxidation by air

A series of mesoporous nickel cobalt oxides with different Ni/Co was synthesized by a mild hydrothermal method. The physical and chemical properties of these oxides were characterized using XRD, N2-Physisorption, SEM/TEM, XPS, H2-TPR and O2-TPD. The catalytic performances for liquid-phase oxidation of benzyl alcohol by air were also investigated. It was found that the Ni/Co ratio had remarkable influences on the crystal phase, morphology, surface element composition, redox properties as well as their capability toward O2 activation. Compared with the monoxide, the mixed oxide showed enhanced conversion, particularly the Ni1Co3 with Ni/Co of 1/3 has the highest activity of all. In addition, the Ni1Co3 exhibited good recyclability upon recalcination prior to next run. The excellent performance of Ni1Co3 was closely related to the abundant oxygen vacancy or defect sites, which possibly resulted from the formation of distorted nickel cobalt spinel structure. They were responsible for the enhanced activation of O2 molecules and consequently higher conversion in benzyl alcohol oxidation.