Constructing silanol nests on ZSM-5 catalyst by deboronation for stable alkylation of toluene with methanol

Abstract

Dealuminization over aluminium-containing ZSM-5 could create silanol nests and improve catalytic activity for alkylation of toluene with methanol. However, obviously damaged microporous structure seriously accelerated catalyst deactivation. Here, we demonstrate highly stable alkylation on ZSM-5 by deboronation treatment over boron-containing ZSM-5.11B MAS NMR, 1H MAS NMR and OH-IR suggested that silanol nests with hydrogen bonds were created at the expenses of the removal of skeleton-B atoms. The formed silanol nests promote the adsorption of toluene, inhibit the methanol self-reaction and corresponding the deep alkylation process. Therefore, alkylation efficiency and toluene conversion could reach 70.8% and 33.5%, respectively. Importantly, the microporous structure of deboronized ZSM-5 was well maintained during deboronation, which determined a greatly improved catalytic stability compared with that of traditional dealuminized ZSM-5. Moreover, the deboronized ZSM-5 still presented relatively good catalytic stability under a higher methanol feedstock although the coke deposition was accelerated.