Fabrication of Mg-Al hydrotalcite/carbon nanotubes hybrid base catalysts for efficient production of fructose from glucose

Abstract

Efficient and selective glucose-to-fructose isomerization is a crucial step in biorefinery, usually catalyzed by Lewis acid or Brønsted base catalyst. However, inferior selectivity of Lewis acid and low conversion of Brønsted base hamper the practical application. Herein, a Mg-Al hydrotalcite/carbon nanotubes hybrid catalyst was prepared using bottom-up strategy for glucose isomerization in water. Tunable textural properties and basicity of the catalyst was achieved by tailoring Mg/Al ratio while the introduction of CNT could further change the morphology and surface electronic properties, resulting in a desirable active site exposure and less particle aggregation. Additionally, DFT and in-situ FTIR experiment demonstrated glucose conversion proceed via base-catalyzed route, and the increase of Mg/Al ratio as well as the electron deficiency of the surface would enhance the interaction between glucose and catalyst, which was conducive to the adsorption and deprotonation of glucose. As a result, a fructose yield of 40%, which is close to thermodynamic equilibrium yield, was obtained over HT5:1/CNT in water within 2 h.