MoO_3在ZSM-5分子筛上分散及表面状态的研究

STUDIES ON DISPERSION AND SURFACE STATE OF MoO_3 ON ZSM-5 ZEOLITE

将晶相MoO_3同ZSM-5分子筛充分研磨混合后,在450℃下焙烧24h,制成氧化物负载型催化剂,然后进行XRD、IR光谱测定,结果表明,MoO_3能够在ZSM-5上自发分散进入分子筛结构孔道中,分散量为0.070g/g ZSM-5,分子筛晶体结构未受到明显破坏;进行氨溶实验和紫外漫反射光谱测定,结果表明,分散的非晶相表面层钼,存在四面体配位和八面体配位两种状态,后者约占S3％。

Crystalline MoO_3 and ZSM-5 zeolite are mixed thoroughly, and the mixtures are calcined at 450℃ for 24 hours. The MoO_3 loaded zeolites thus formed are studied by XRD and IR spectroscopy. It shows that MoO_3 interacts strongly with the framework of zeolite during calcination. As a result of this interaction MoO_3 migrates into the cavities of zeolite and disperses as a noncrystalline surface species. The dispersion rate is 0.07g/g ZSM-5, and the crystalline structure of the zeolite is not apparently affected. The results of ultraviolet diffuse reflec tancespectra and extraction with aqueous ammonia show that there are two different surface species. One is Mo^(6+) ions in tetrahedral coordination and the another in octahedral coordination with the latter accounts for 63% of the total.