Stable Ga-MFI zeolite for propane dehydroaromatization constructed by healing Silanol-defect in framework.

Propane dehydroaromatization (PDA) provides a promising route to produce valuable chemicals such as benzene, toluene and xylene via non-petroleum feedstocks, in which Ga-modified MFI zeolites demonstrate high activity but are susceptible to severe coke deposition. The defect-derived silanols (Si-OH) in zeolite formed during synthesis has emerged as a predominant factor, making the prolongation of the catalyst longevity a major challenge. Here, we developed a gallosilicate MFI zeolite with silanol-defect remediated (Ga-MFI-AHFS) through an ammonium hexafluorosilicate post-treatment, which exhibited an extraordinary activity and stability. Ga-MFI-AHFS exhibits a nearly unchanged propane conversion around 82.0 % with aromatics selectivity around 64.5 % compared to a 25.4 % conversion decline on the raw zeolite with defects exposed during the 20-h CO2 assisted PDA reaction. The results of FTIR and MAS NMR showed a decreased content of silanol nests as well as the internal Si-OH groups, indicating the successful repair of silicon hydroxyl defects. The restored framework endows the Ga-MFI-AHFS zeolite with an excellent coking resistance, giving a much lower coking-rate of 5.8 × 10-8 molC/molC-in-produced-Aromatics, which is one-sixth of that on Ga-MFI. This work developed a facile route to prepare Ga-MFI zeolite with suppressed silanol-defects, which could help to realize a stable dehydroaromatization of light alkanes.