Understanding Diels–Alder conversion of 2,5-Dimethylfuran and acrylic acid to para-Xylene over beta zeolites

Conversion of 2,5-Dimethylfuran (DMF) and Acrylic Acid by Diels–Alder cycloaddition reaction over the Beta zeolites has demonstrated potential for producing renewable para-Xylene (PX). However, the reaction process and the structure-activity correlation were not fully characterized. In this work, Beta zeolites were used to catalyze the Diels–Alder reaction of DMF. The structural characterization, selective poisoning experiments, in-situ FTIR spectra measurements, and kinetic analysis were performed. The results illustrated that the reaction to form PX proceeds by cycloaddition and subsequent decarboxylation over Lewis (L) acid sites, and finally dehydration over Brønsted (B) acid sites. 2,5-dimethylbenzoic acid could not produce PX by decarboxylation over Beta zeolites. The FTIR spectra measurements showed that the B acid sites were incorporated into the reaction network. There were strong diffusion limitations in the H-Beta catalyst during the reaction. When diffusion limitations were eliminated by producing mesopores, the reaction was kinetically limited by the dehydration step.