MgO-ZrO2 Mixed Oxides as Effective and Reusable Base Catalysts for Glucose Isomerization into Fructose in Aqueous Media

Abstract

MgO-ZrO₂ mixed oxides prepared with different Mg/Zr atomic ratios (denoted as xMZ: where x is the atomic ratio of Mg/Zr) are investigated for the glucose isomerization to fructose in water at 95 °C. The highest fructose yield of 33 % is obtained over 0.76MZ with ≈74 % selectivity after 3 h. To gain insight into the structure-activity relationships, the prepared catalysts are characterized by N₂ physisorption, XRD, FTIR and CO₂ -TPD. The results indicate that the addition of MgO drastically changed the textual property of ZrO₂ and increased the number of basic sites. The kinetic studies revealed that the Lewis basic sites (cus-O^2- ) generated from the highly dispersed MgO are the active sites responsible for the enhanced isomerization activity. Notably, MZ is reusable for four runs without a significant decrease in catalyst activity. Accordingly, this study provides an easily prepared, cheap, and recyclable catalyst that may hold great potential for fructose production.

Keywords: basicity; fructose; glucose isomerization; heterogeneous catalysis; mixed oxides.