Oxidative Lactonization of Diethylene Glycol to High-Value-Added Product 1,4-Dioxan-2-One Promoted By a Highly Efficacious and Selective Catalyst ZnO-ZnCr2O4

For the first time, the desired product 1,4-dioxan-2-one (PDO) was successfully synthesized via the oxidative lactonization of diethylene glycol (DEG) under mild conditions. After screening several catalysts (M-Cr-O), we found ZnO-ZnCr₂O₄ (Zn-Cr-O) catalyst exhibited excellent catalytic performance and this chemical transformation obtained moderate to excellent selectivity (96.22%) and conversion (81.95%) within a 4-hour reaction time. Subsequently, the morphology of calcined M-Cr-O was investigated by FT-IR, XRD, FESEM, TEM, and N₂ adsorption-desorption tests for further study on catalytic performances. The strength and quantity of acid and base sites over Zn-Cr-O were also detected by NH₃-TPD and CO₂-TPD, and it was worth noting that the acid/base sites over ZnO-ZnCr₂O₄ (Zn-Cr-O) catalyst could promote this catalytic process well. Recycle studies demonstrated exceptional stability and recyclability of the prepared catalyst without significant efficiency and selectivity loss after 10 consecutive cycles.