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由于水蒸气处理HZSM-5生成的骨架外铝在分子筛中体现Lewis酸性,分子筛中骨架外铝物种的可移动性导致Lewis酸与分子筛本身的Br nsted酸在空间上具有临近性.当甲基环己烷分子在HZSM-5的笼中转化时,Lewis酸与Br nsted酸的协同作用加快了甲基环己烷分子的转化速率,且骨架外铝物种浓度越高,这种协同效应越明显.而产物的选择性只与催化剂的孔道结构有关,与水蒸气处理所导致的酸性质的变化无关.
Because of the Lewis acidity in the molecular sieves due to the extra-framework aluminum formed by steam treatment of HZSM-5, the mobility of the extra-framework aluminum species in the molecular sieves results in the spatially close proximity of Lewis acid to the Br nsted acid of the molecular sieve. The synergistic effect of Lewis acid and Br nsted acid accelerates the conversion rate of methylcyclohexane molecules when hexane molecules are converted into cages in HZSM-5, and the more obvious the synergistic effect is, the higher the concentration of extra-framework aluminum species. The selectivity of the product is only related to the pore structure of the catalyst, regardless of the change of the acid property caused by the steam treatment.