Sustainable production of high-value gluconic acid and glucaric acid through oxidation of biomass-derived glucose: A critical review

Gluconic acid (GOA) and glucaric acid (GAA) are valuable chemicals for a wide range of applications, yet conventional technologies for their production suffer from low efficiency, high cost, and especially environmental concerns. It is imperative to develop sustainable heterogeneous catalytic systems exhibiting promising catalytic activity and good recyclability. In this review, base-free glucose oxidation over structure-tailored heterogeneous catalysts is discussed, and Au-based catalysts are found to present promising potential in sustainable biorefineries. To address the issue of its cost, introducing secondary metals forming bimetallic catalysts and developing non-noble metal-based catalysts are proposed as possible solutions. GAA production is of particular interest due to its high value and yet limited investigation regarding the mechanisms and system development. The feasibility of raw biomass conversion over bifunctional catalysts is also explored for the sake of industrial application. The potential of emerging technologies including ultrasound-assisted, microwave-assisted, and photocatalytic oxidation is emphasized, which allow for milder operating conditions compared to conventional heating. This review curates the latest findings and highlights the opportunities and limitations of reported technologies, promoting the development of green catalytic systems to achieve sustainable valorization of biomass/food waste through controllable oxidation pathways.