Aromatization over nanosized Ga-containing ZSM-5 zeolites prepared by different methods: Effect of acidity of active Ga species on the catalytic performance

• 来源期刊: 能源化学
• 年，卷（期）: 2017,（4）
• 页码范围: 768-775
• 页数: 8页
• 语种: 英文
• DOI: 10.1016/j.jechem.2017.03.014

摘要

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+]a species with stronger Lewis acid sites produced a better synergism with moderate Br(O)nsted acid sites and thus improved the selectivity to aromatic compounds.However,the impregnation results in the formation of Ga2O3 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.