N-Doped natural albite mineral as green solid catalyst for efficient isomerization of glucose into fructose in water

Abstract

The catalytic isomerization of glucose to fructose has been considered a crucial step in the field of biomass valorization. As such, the development of environment-friendly and efficient heterogeneous catalysts for glucose isomerization is urgently required. In this study, a green N-doped mineral catalyst (i.e., CS/Ab) was prepared with chitosan as nitrogen precursors deposited on the natural albite. The basicity of pristine albite is limited, but N-doping and calcination can significantly increase the density and strength of base sites. The CO₂-TPD and XPS results identified that the introduction of nitrogen species (mainly pyridine and pyrrole) on the albite surface could impart the weak or medium base character of the catalyst, which is beneficial for fructose production with high selectivity. The CS/Ab catalyst displayed good catalytic performance with 38.9% yield and 85.4% selectivity of fructose at mild temperature (90 °C) in water, and the activation energy for the CS/Ab-catalyzed glucose conversion was calculated to be 46.9 kJ mol⁻¹. This work advances the utilization of biomass waste and minerals as green and efficient catalyst for base-catalyzed biorefinery reaction, and provides insights into the active components for glucose isomerization.