Ultrasonic-assisted synthesis of acidic Al-MCM-41 for enhanced selective production of HMF from glucose

The sustainable transformation of renewable biomass into value-added chemicals is essential to addressing global environmental and energy challenges. Among these, the production of 5-hydroxymethylfurfural (HMF) from biomass-derived glucose is of considerable interest for both scientific and industrial applications. In this study, mesoporous aluminium incorporated MCM-41 catalysts (Al-MCM-41) were synthesized using an ultrasonic-assisted method at room temperature. Their ordered mesoporous structure was preserved even with high concentrations of Al. The catalysts' acidity was finely tuned by varying the Si/Al ratio, enabling the development of an optimal catalyst to enhance the glucose-to-HMF conversion via Brønsted and Lewis acid catalysis. Characterization techniques, including XRD, TEM, N₂ adsorption-desorption, NH₃-TPD, Py-FTIR, ²⁹Si and ²⁷Al MAS NMR, were employed to evaluate the catalysts’ structure and acidity. The results revealed that ultrasonic-assisted synthesis strategy improves Al dispersion, optimizes acid site density, and significantly enhances HMF yield and selectivity. The best-performing Al-MCM-41-10 catalyst can afford ∼90 % glucose conversion with ∼60 % HMF selectivity at 160 °C, and displays excellent reusability under the applied reaction conditions. This study provides valuable insights into designing efficient catalysts for biomass conversion and underscores the broad applicability of the ultrasonic-assisted synthesis method for other heteroatom-doped mesoporous materials, such as Sn-MCM-41.