One-Pot Selective Synthesis of Renewable p-Xylene by Completely Biomass-Based Ethanol and Dimethylfuran with Functionalized Mesoporous MCM-41

One-pot direct synthesis of renewable p-xylene (PX) via Diels-Alder cycloaddition of completely bio-based ethanol and 2,5-dimethylfuran (DMF) was studied comparatively over dealuminated HBeta zeolite and functionalized mesoporous MCM-41. The sulfonic group-functionalized MCM-41 had better catalytic performances. Under the optimized conditions, an ethanol conversion of similar to 100 %, 2,5-DMF conversion of 79 % and PX selectivity of 80 % were obtained over NH3-Silylated-MCM-41-10 %SO3H catalyst with 0.8 wt % N content, which is much better than HBeta zeolite catalyst. X-ray diffraction (XRD), thermogravimetric analysis (TGA), Si-29 cross-polarization magic-angle spinning (CP/MAS) NMR and infared (IR) characterizations showed that sulfonic and silylated groups have been successfully grafted onto MCM-41. Quantitative H-1 MAS NMR with d5-pyridine adsorption unambiguously demonstrated that silylated MCM-41-SO3H with NH3 pre-treatment has much higher amount and stronger strength of Bronsted acid than zeolite catalyst. This is the vital factor to catalyze the dehydration of ethanol to ethylene and speed up the Diels-Alder cycloaddition reaction, ultimately increase PX selectivity and reduce much less soft-coke deposit on MCM-41-SO3H (similar to 4 wt %) than on HBeta zeolite (similar to 12 wt %). This work demonstrates a simple and economical strategy to further improve the potential for the production of sustainable chemicals from complete biomass.

Automated summary

The study compared the efficiency of dealuminated HBeta zeolite and functionalized mesoporous MCM-41 as catalysts in the direct synthesis of renewable p-xylene from completely bio-based ethanol and 2,5-dimethylfuran via Diels-Alder cycloaddition. It was found that the sulfonic group-functionalized MCM-41 catalyst had better catalytic performance, leading to higher PX selectivity and less soft-coke deposition compared to HBeta zeolite. The NH3 pre-treatment of silylated MCM-41-SO3H significantly increased its Bronsted acid strength, facilitating the dehydration of ethanol to ethylene and accelerating the cycloaddition reaction.