Highly efficient catalytic conversion of 2,5-dimethylfuran and acrylic acid to para-xylene over MCM-22 zeolites

Producing para-xylene (PX) by Diels–Alder (D–A) cycloaddition of 2,5-dimethylfuran (DMF) and acrylic acid (AA) was a potential renewable pathway. In this study, MCM-22 zeolites served as catalysts for the D–A cycloaddition reaction, exhibiting significantly higher activity compared to conventional Beta and ZSM-5 zeolites. The high activity was demonstrated to be derived mainly from the acid sites located within the pocket structures on the external surface of MCM-22. The rate-determining step for the formation of PX was the dehydration process of the B-acid-catalyzed cycloadduct. The external silanols at the pore entrance of the pocket structure could adsorb the reactants and promote the D–A cycloaddition reaction. The MCM-22(15) catalyst achieved 98% DMF conversion with 88% PX selectivity after 10 h at 190 ℃ in the D-A cycloaddition reaction.