Insight into the Aromatic Production from Furan Derivatives and Ethylene

Abstract

The one-pot Diels − Alder cycloaddition/dehydration tandem reaction between furanic compounds and ethylene represents a promising route for synthesizing biomass-derived aromatic hydrocarbons. In this study, a combined approach of density functional theory (DFT) calculations and experimental investigations was employed to elucidate the reaction mechanism of H-Beta zeolite-catalyzed transformations involving furan derivatives (2,5-dimethylfuran, 2-methylfuran, and furan) with ethylene. Computational results revealed that the α-methyl group exerts a dual influence on the tandem reaction. In the Diels-Alder step, the α-methyl group enhances the diene’s electron density, thereby promoting the cycloaddition process. Conversely, the steric hindrance introduced by α-substituents decelerates the addition kinetics. Notably, the activation energy barrier for furan’s Diels-Alder reaction with ethylene was found to be significantly higher than those of 2,5-dimethylfuran and 2-methylfuran, accounting for the observed lower conversion efficiency of unsubstituted furan. Regarding the subsequent dehydration step, the α-methyl group stabilizes the carbocation intermediate, resulting in a substantially reduced energy gap for 2,5-dimethylfuran compared to 2-methylfuran and furan. This stabilization effect accelerates dehydration kinetics and improves p-xylene selectivity. Our findings demonstrate how reagent electronic properties and steric effects collectively govern reaction pathways, offering fundamental insights for rational design of tandem reaction catalysts.

Graphical Abstract

Renewble synthesis of aromatics (benzene, toluene, p-xylene) via furanic compounds (furan, 2-methylfuran, 2,5-dimethylfuran) and ethene was achieved on HBeta zeolite, and the influence of α-methyl group were investigated experimentally and theoretically.