Liwen Guo,Dao Shi,Tianjun Zhang,Yanhang Ma,Guodong Qi,Jun Xu,Qiming Sun
Propane dehydrogenation (PDH) has emerged as a key on-purpose technology for the production of propylene, but it often depends on toxic chromium and expensive platinum catalysts, highlighting the need for environmentally friendly and cost-effective alternatives. In this study, we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co 1 O 3 H x structure by regulating silanol nests in purely siliceous Beta zeolites. Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity. Additionally, the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles. Notably, the optimized Co 0.3% /deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol C3H6 g cat –1 h –1 , with an exceptional propylene selectivity of 99.1% at 550 °C. Moreover, the Co 0.3% /deAl-meso-Beta catalyst demonstrated excellent stability, with negligible deactivation after 5 consecutive regeneration cycles. This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites, providing valuable insights for the design of high-activity, high-stability, and low-cost PDH catalysts.
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. 11 B MAS NMR, 1 H 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.
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