Theoretical Study on the Brønsted Acidity of Al Doped SBA-15 for Methanol Dehydration as a Reaction Analog for the Transformation of Pectin to Furfural

The most likely routes for the thermal decomposition of biomass derived D-galacturonic acid leading to furfural were analyzed through comparison of the activation energy barriers associated with possible kinetic pathways. Dehydration steps were associated with significant activation barriers. The effect of a mesoporous catalyst with Brønsted acidity such as Al-SBA-15 was analyzed. The chemical structure of SBA-15 was optimized by means of a comparison from the experimental structural data previously reported in literature and the structural parameters obtained from DFT calculations at B3LYP/6–31 + G (d, p) level of several catalyst surface models. The bicyclic model structure obtained proved to be representative of framework species in SBA-15. The isomorphic substitution of Al in the SBA-15 model structure was made in order to generate Brønsted acidity. The acidity was studied for the dehydration of methanol, this reaction being representative of the dehydration processes that occur in biomass transformation to furfural. A higher Brønsted acidity strength was observed in free silanol type (Q3) and geminal silanol type (Q2) sites, formed by the isomorphic Al substitution of Si.