Calcined hydrotalcite-coated ZSM-5 with acidic and basic bifunctionalities for 5-hydroxymethylfurfural production from glucose

5-hydroxymethylfurfural (HMF) is a high-value intermediate used in many industrial applications, and its production from biomass has been gaining interest towards the goal for sustainability and green energy. However, HMF production from glucose is a two-step process (glucose isomerization and fructose dehydration) which requires two catalysts: a base and an acid catalyst. The physical mixture system is the simplest method for utilizing these two catalysts, but it is often associated with low conversion and yield due to the long diffusion distances of reactants. This study has successfully synthesized a catalyst with basic and acidic sites in proximity by coating ZSM-5 zeolite with hydrotalcite (HT), allowing glucose and fructose to easily access each active site, respectively. The prepared hydrotalcite-coated ZSM-5 (ZSM-5@HT) has moderate-strength basic sites derived from Mg and Al species, improving glucose conversion and HMF yield. Furthermore, the morphology and basic strength of the HT layer remain unchanged, while the thickness increased as the HT coating amount was increased. Adjusting the amount of HT coating on ZSM-5 created effective active sites on the external surface of the catalyst for glucose isomerization to fructose and fructose dehydration to HMF. ZSM-5@HT 0.50 wt% achieved 96.7% of glucose conversion and 68% of HMF yield at 160 °C for 6 h. Kinetic analysis showed the enhancement of isomerization and dehydration rate by HT coating. Therefore, the developed external surface of ZSM-5@HT, with its adjacent acidic and basic sites and highly dispersed hydrotalcite, is an effective structure to achieve selective HMF production from glucose. • Highly dispersed hydrotalcite was coated on the ZSM-5 external surface successfully • ZSM-5@HT provides proximate acid and base sites, enabling easy access • HT coating amount controls the influence of reactive sites on glucose conversion • ZSM-5@HT with balanced acid and base sites enhanced HMF yield from glucose • ZSM-5@HT 0.50 wt% achieved high glucose conversion (96.7%) and HMF yield (68%)