(671f) Catalytic Conversion of Glucose to Tartaric Acid over Synergistic Aupt/TiO2 Catalysts

Catalytic conversion of biomass to fuels and chemicals is important for establishing environment-friendly chemical processes. Aqueous phase oxidation of sugars and polyols is crucial for sustainable production of value-added carboxylic acids and derivatives. Tartaric acid (TA), a high value-added C₄ dicarboxylic acid, has been widely used for additives of food, dyes and pharmaceuticals. Traditionally, Chemical synthesis method of TA is only via oxidation of maleic anhydride, a two-step reaction generating significant amounts of toxic by-products. Up to date, there has been no detailed study on catalytic synthesis of TA from biomass using heterogeneous catalysts. Therefore, in this work, we proposed a family of AuPt/TiO₂ catalysts for facile TA synthesis (yield: 50%) from glucose in base-free condition at 110 °C and 2 MPa O₂.

In this work, conversion and selectivity of different metal catalysts, including Au, Pt, AuM (M: Pt, Pd, Mn, Cu, Fe) supported by TiO₂, were studied for glucose oxidation. It is found that AuPt/TiO₂ catalyst outperformed other candidates in terms of conversion and selectivity. Compared with monometallic Pt/TiO₂ and Au/TiO₂ catalysts, the bimetallic AuPt/TiO₂ catalyst showed remarkable catalytic performances for conversion of glucose (X ~ 100%) at 110 ^oC. Meanwhile, selectivity of TA is approximately 50%, suggesting that AuPt/TiO₂ synergistically leads to formation of C₄ products under reaction condition.

Based on the preliminary studies, we also conducted structure sensitivity analysis for oxidation of glucose and gluconic acid to TA, with the aim at understanding possible reaction mechanism on catalyst surface. Experimental studies have demonstrated that C-H and C=O bond activation tend to follow σ-σ and Ï€-Ï€ bonding mechanism on catalyst surface. The elrectronic reconfiguration contributes to the synergism of bimetallic AuPt/TiO₂ catalysts for both C-H and C-C cleavage reactions. Meanwhile, kinetic modeling on catalytic conversion and electronic reconfiguration at Pt-Au interface will also be interpreted in details.