Requlation and Cotolysis of Strong Solid Acid Generated on Extra-Framework Aluminum

用高铝含量的Y型和丝光沸石型样品精确测定了沸石的酸性与组成之间的关系。在实验范围内，解吸的氨的数量(显示酸量)与[Al]-[Na]原子的数量大致相同。这与通常观察到的形成二次相邻铝物种的关系有很大不同。指出即使铝原子位于二次邻位时，分子筛中的同晶取代铝仍按化学计量比产生酸中心，在ZSM-5沸石上程序升温脱附氨气时观察到很强的酸中心。该中心可归因于非骨架铝，它与通常的骨架酸中心相互作用。通过铝离子的浸渍，在沸石骨架中产生了以酸中心为代价的强酸中心，模板分子去除步骤的条件对HZSM-5中强酸位的浓度有很大的影响。还研究了在约373K下氨与水处理对固体酸度的影响，并鉴定了两种方法产生的酸中心的相似性。通过对酸性中心的定量测定，发现很强的酸性中心由两个铝阳离子组成。Na_2H_2-乙二胺四乙酸处理超稳Y沸石形成了酸强度分布窄、量大的强B酸中心，对烷烃裂化具有活性。

The relationship between the acidic property and the composition of a zeolite was precisely measured using Y-and mordenite-type samples with high aluminum contents. The number of the desorbed ammonia, showing the acid amount, was approximately same to the number of [Al]-[Na] atoms over the experimental range. This is quite different from the conventionally observed relationship where the secondary-neighboring aluminum species is formed. It is pointed out that the isomorphously substituted aluminum in zeolite generates the acid site according to the stoichiometry even when the aluminum atoms locate the secondary-neighboring sites.Very strong acid site was observed on the zeolite ZSM-5 in measurements of temperature programmed desorption of ammonia. The site was ascribable to the non-framework aluminum, which interacted with the usual framework acid site. By impregnation of aluminum cation, the strong acid site was created at the expense of the acid site in a zeolite framework.Conditions of a step for template molecule removal affected strongly the concentration of very strong acid site in HZSM-5. Treatment with ammonia with water at ca 373 K was also studied as a procedure to affect the solid acidity, and a similarity of acid sites created by both methods was identified. From the quantitative measurements of acid sites, it was found that the very strong acid site consisted of two Al cations. Catalytic activity for octane cracking was enhanced by the presence of very strong acid site.Strong Bronsted acid site with a narrow distribution of acid strength and large amount, which was active for alkane cracking, was formed by Na_2H_2-ethylenediaminetetraacetic acid treatment of ultra stable Y zeolite.