Selective air oxidation of biobased lactate to pyruvate catalyzed by abundant element heterogeneous catalysts

The current chemical industry relies heavily on nonrenewable fossil sources, resulting in the emission of greenhouse gases and other environmental problems. Biomass, the most abundant renewable carbon source, is considered as a ‘green’ alternative to fossil sources. There is a growing interest in upgrading of biomass into commodity chemicals, primarily through a set of simple building blocks, so-called ‘platform molecules’. Lactic acid and its esters are among such promising biomass-derived platform molecules. They can be converted into a variety of important industrial chemicals. In particular, pyruvate esters are important chemicals used in many sectors, such as agrochemicals, foodstuffs, cosmetics, and pharmaceuticals. The catalytic oxidative dehydrogenation of lactates with molecular oxygen is a promising route for producing pyruvates, ideally giving water as the only byproduct. But this oxidation is a challenging process. On one hand, molecular oxygen is the most abundant and the cheapest oxidant but has a high activation barrier. Its activation requires noble metal catalysts or harsh reaction conditions. On the other hand, once dioxygen is activated, the oxygen-rich pyruvate product is easily over-oxidized to unwanted products. As such, we report a series of advanced abundant-element heterogeneous catalysts for selective air oxidation of lactate to pyruvate in liquid phase and in vapour phase, including synthesis and characterization of catalysts with well-defined structures, catalytic activity evaluation and kinetic analysis, operando spectroscopies, and computational calculations. This work provides fundamental insights for developing further simple and cost-effective catalytic systems for highly efficient conversion of biomass derivatives to value-added chemicals under mild conditions.