Efficient and stable platinum nanocatalysts supported over Ca-doped ZnAl2O4 spinels for base-free selective oxidation of glycerol to glyceric acid

In the work, highly dispersed platinum nanocatalysts supported over undoped and Ca-doped zinc aluminate spinels were developed and applied for aqueous-phase selective oxidation of glycerol to produce glyceric acid under base-free conditions. As-fabricated Pt-based catalyst with the incorporation of an appropriate Ca/(Ca + Zn) molar ratio of 0.1 into the spinel exhibited a higher catalytic activity, along with a selectivity to glyceric acid (> 81%) and a high turnover frequency of 1160 h(-1), compared with other supported Pt-based ones over zinc aluminates, as well as most of supported Pt catalysts previously reported. The structural characterizations and catalytic experiments showed that surface synergy between highly dispersed metallic Pt species and medium-strength basic sites mainly contributed to its enhanced catalytic efficiency for base-free glycerol oxidation. Moreover, the present Pt catalyst also presented high structural stability and good reusability. The work opens an alternative approach for constructing highly efficient and stable metal-base bifunctional catalysts for a wide range of heterogeneous oxidation processes without the addition of liquid alkalis.