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Nanosized Ga-containing ZSM-5 zeolites were prepared via isomorphous substitution and impregnation followed by characterized using various techniques. The catalytic performance of the zeolites for the aromatization of 1-hexene was investigated. The results indicate that isomorphous substitution promotes the incorporation of Ga heteroatoms into the framework along with the formation of extra-framework GaO~+species([GaO~+]a) that have stronger interactions with the negative potential of the framework. In addition, based on the Py-IR results and catalytic performance, the [GaO~+]aspecies with stronger Lewis acid sites produced a better synergism with moderate Br?nsted acid sites and thus improved the selectivity to aromatic compounds. However, the impregnation results in the formation of Ga_2O_3 phase and small amounts of GaO~+species that are mainly located on the external surface([GaO~+]~b), which contribute to weaker Lewis acid sites due to weaker interactions with the zeolite framework. During 1-hexene aromatization, the nanosized Ga isomorphously substituted ZSM-5 zeolite samples(Gax-NZ5) exhibited better catalytic performance compared to the impregnated samples, and the highest aromatic yield(i.e.,65.4 wt%) was achieved over the Ga4.2-NZ5 sample, which contained with the highest Ga content.
The catalytic performance of the zeolites for the aromatization of 1-hexene was investigated. The results indicate that isomorphous substitution promotes the incorporation of Ga heteroatoms into the framework along with the formation of extra-framework GaO ~ + species ([GaO ~ +] a) that have stronger interactions with the negative potential of the framework. In addition, based on the Py-IR results and catalytic performance, the However, the impregnation results in the formation of Ga_2O_3 phase and small amounts of GaO ~ + species [GaO ~ +] aspecies with stronger Lewis acid sites produced a better synergism with moderate Br? Nsted acid sites and thus improved the selectivity to aromatic compounds that are mainly located on the external surface ([GaO ~ +] ~ b), which contribute to weaker Lewis acid sites due to weaker interactions with the zeolite framewor k. During 1-hexene aromatization, the nanosized Ga isomorphously substituted ZSM-5 zeolite samples (Gax-NZ5) better than the impregnated samples, and the highest aromatic yield (ie, 65.4 wt% .2-NZ5 sample, which contained the highest Ga content.