Aqueous Oxidation of 1,5-Pentanediol to Glutaric Acid Over Pt-Based Catalysts in a Base-Free Medium

Glutaric acid is an important C5 platform compound in the polyester industry. However, catalytic synthesis of glutaric acid from biomass still remains largely unexplored in this field. We reported in this work a bimetallic PtAu/TiO2 catalyst for the facile liquid-phase oxidation of bioderived 1,5-pentanediol to glutaric acid, with a remarkable yield of 87% at 80 °C and 1 MPa O2. It is found that the Pt/TiO2 catalyst displays weak π-donation with a C═O bond, with 5-hydroxypentanal as the dominant product during primary oxidation. However, doping Au into Pt/TiO2 elevates the energy level of dx2–y2 orbitals at Pt sites and promotes the generation of •OH radicals. As a result, fast secondary oxidation reactions were achieved toward the formation of glutaric acid as the target product. The mechanistic information revealed in this work is useful in designing synergistic catalysts for the liquid-phase synthesis of various other biodicarboxylic acids in a base-free medium.