High-efficient oxidation of high-concentration furfural to 2-furoic acid over Ag/ZrO2 catalysts at low-temperature

The selective oxidation of furfural (FF) to 2-furoic acid (FA) represents a significant route toward sustainable chemical production. However, existing catalytic systems often suffer from limitations such as low substrate concentrations, harsh reaction conditions, and inadequate selectivity. In this study, a series of Ag/ZrO 2 catalysts with varying Ag loadings were prepared via a deposition–precipitation method and were used for the aerobic oxidation of FF to FA under mild conditions. The effects of metal loading, catalyst mass, reaction temperature, reaction time, and oxygen pressure on FF conversion and FA selectivity were systematically investigated. Under optimized conditions, nearly 100% FA was achieved under 10 wt% FF concentration at low-temperature (ca. 5 °C), while a high selectivity of 90.3% toward FA was maintained even at 20 wt% FF. The catalysts also exhibited excellent recyclability, retaining over 85% FA selectivity after five consecutive cycles. Comprehensive characterization techniques, including XRD, XPS, and HRTEM, were employed to elucidate the structure-activity relationship of the catalysts. The experimental and characterization findings propose a possible reaction mechanism involving synergistic effects of Ag 0 sites for dehydrogenation and ZrO 2 oxygen vacancies for O 2 activation. This work represents a notable advance in the field, as it develops the high efficient catalytic system under high FF concentrations and low-temperature conditions for the first time.