Influence of Brønsted and Lewis acidity of the modified Al-MCM-41 solid acid on cellulose conversion and 5-hydroxylmethylfurfuran selectivity

The modified Al-MCM-41 solid acids with turning Si/Al molar ratio were successfully fabricated through a hydrothermal route and utilized as a suitable catalyst in the cellulose conversion into 5-hydroxylmethylfurfural (5-HMF). The crystal structure, composition, morphologies and porosity of as-synthesized acids were characterized by XRD, FT-IR, N2 adsorption-desorption, TEM and EDS. The 27Al MAS NMR and 29Si-MAS NMR results revealed the existence of both Al framework and Al extra framework. Besides, the existence of medium-weak and strong acid sites, according to Brønsted and Lewis acidity, in Al-MCM-41 acids was confirmed by NH3-TPD and FTIR-pyridine adsorption. The 30Al-MCM-41 solid acid (Si/Al molar ratio = 30) exhibited excellent activity with the highest 5-HMF yield of 40.56% compared to other samples. We also discovered that 5-HMF production, as well as cellulose conversion, strongly depended on the total acid, strong/medium-weak acid ratio, as well as Brønsted/Lewis acid ratio. Therefore, these parameters have been considered as essential factors for the design of solid acid for 5-HMF production. [Display omitted] •Al-MCM-41 with turning Si/Al molar ratio was fabricated by a hydrothermal router.•The existence of Brønsted/Lewis acidity was confirmed by NH3-TPD and FTIR-pyridine.•Al-MCM-41 was used as effective solid acids for 5-HMF fabrication from cellulose.•The total acid and strong/medium-weak acid ratio affected the 5-HMF selectivity.•5-HMF selectivity strongly depended on the Brønsted/Lewis acid ratio.