PtIn nanoalloy supported on Sn-MFI for efficient selective oxidation of glycerol to lactic acid

Developing efficient Pt-based catalysts is crucial for sustainable lactic acid (LA) production via glycerol oxidation. Herein, we synthesized a series of robust PtIn/Sn-MFI catalysts with low Pt loading of 0.5 wt% for glycerol oxidation under base-free conditions. The PtIn/Sn-MFI catalysts with varying In contents exhibited a volcano-shaped trend between turnover frequency (TOF) and In/Pt molar ratio. Among all tested catalysts, the Pt 0.5 In 1.0 /Sn-MFI sample exhibited the highest catalytic activity (1283 h –1 ), achieving 96.8% glycerol conversion with 73.5% LA selectivity, surpassing the monometallic Pt 0.5 /Sn-MFI catalyst. Furthermore, the Pt 0.5 In 1.0 /Sn-MFI catalyst maintained excellent stability, with no significant degradation in catalytic performance even after five consecutive recycling runs. Experimental analysis and characterizations verified the formation of PtIn 2 nanoalloys, accompanied by electron transfer from In to Pt, which significantly enhanced the catalysts’ O−H bond activation ability, resulting in high activity and selectivity. Combined with kinetic studies and density functional theory calculations, we further revealed that PtIn 2 nanoalloy active sites significantly reduce the activation energy barrier for the dehydrogenation of the secondary hydroxy group in the reaction pathway. This work offers new perspectives on the rational design of cost-effective, high-efficiency catalysts for the sustainable oxidation of glycerol to LA.