Zeolite-Encapsulated Ni Catalyst for the Direct Conversion of Mono- and Polysaccharides to Ethylene Glycol

We have developed a simple, scalable, postsynthetic treatment for the encapsulation of Ni nanoparticles inside MFI zeolites as size-selective hydrogenation catalysts. We show that size-selective sieving of glucose from glycolaldehyde by the Ni-MFI-type zeolites enables an improvement in ethylene glycol yield by minimizing sorbitol and mannitol formation. This property is applied for the direct conversion of glucose to ethylene glycol, which can achieve 63% yield with less than 2% sugar alcohols in batch operation at lower reaction temperatures than previously reported (170 °C vs 230 °C). This improvement in size selectivity and yield can be extended to polysaccharides. The impacts of catalyst loadings, temperature, pH, and substrate concentration were studied, and optimal conditions for high selectivity were identified for both glucose and starch.