Al2O3‐TiO2 Modified Sulfonated Carbon with Hierarchically Ordered Pores for Glucose Conversion to 5‐HMF

Abstract

AbstractSulfonated carbons with hierarchically ordered pores (SCHOP) are not effective catalysts for glucose to 5‐hydroxymethylfurfural (5‐HMF) although they are very effective for fructose conversion due to insufficient and unsuitable Lewis acid sites in SCHOP unfavorable for isomerization of glucose to fructose. This paper attempts to intensify the Lewis acid sites on the surface of SCHOP by doping Al2O3 and TiO2 (Al−Ti@SCHOP) so as to promote glucose conversion to 5‐HMF. Characterizations by SEM, TEM, BET and N2 adsorption‐desorption showed that the well‐ordered hierarchical pore structure of SCHOP was preserved after doping the metal oxides. EDS and XRD analyses confirmed that Al2O3 and TiO2 were well‐dispersed on the surface. FTIR, Py‐FTIR and NH3‐TPD proved that not only sulfonic acid groups were introduced successfully but also very strong acid sites were formed. Furthermore, the strength of Lewis and Brönsted acid sites on the surface of Al−Ti@SCHOP were tailored by adjusting the mass ratio of Al2O3 to TiO2. Al−Ti@SCHOP with an Al2O3/TiO2 mass ratio of 2:1 demonstrated the highest catalytic activity for glucose dehydration to 5‐HMF. As high as above 96% of 5‐HMF selectivity could be obtained within the initial reaction time of 3.0 h, and a maximum 5‐HMF yield of 57.36% occurred at the reaction time of 5.0 h when reacting at 130 °C. Besides, the catalyst has its good stability.