Highly efficient conversion of glucose to methyl lactate over hierarchical bimetal-doped Beta zeolite catalysts

BACKGROUND Methyl lactate is widely applied in the chemical, food, cosmetics and pharmaceutical industries. The conversion of carbohydrates over heterogeneous catalysts to methyl lactate is a promising environmentally benign process. RESULTS Hierarchical Sn-Beta zeolite (Sn-Beta) and corresponding bimetal-doped Beta zeolites (M-Sn-Beta; M = Zn, In, La, Ga, Ni) were prepared via a novel modified hydrothermal synthesis method to convert carbohydrates into methyl lactate. The introduction of Zn into Sn-Beta considerably improved the yield of methyl lactate from glucose, while for the catalysts containing In, La, Ga and Ni, such improvements were not observed. CONCLUSIONS A methyl lactate yield reaching up to 66.7% was obtained over Zn-Sn-Beta at 220 °C for 6 h. The enhanced catalytic performance was attributed to high Lewis acid density and strength, together with synergistic effects between framework Sn 4+ and Zn 2+ ions of Zn-Sn-Beta. Additionally, Zn-Sn-Beta demonstrated fructose and sucrose conversion into methyl lactate with yields of 68.4% and 70.0%, respectively. The Zn-Sn-Beta catalyst could be re-used at least five times with only a slight loss of methyl lactate yield. © 2021 Society of Chemical Industry (SCI).