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首页> 外文期刊>Journal of porous materials >Hierarchical ZSM-5 zeolite designed by combining desilication and dealumination with related study of n-heptane cracking performance
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Hierarchical ZSM-5 zeolite designed by combining desilication and dealumination with related study of n-heptane cracking performance

机译：将脱硅和脱铝与正庚烷裂解性能的相关研究相结合设计的分层ZSM-5沸石

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摘要

The effect of the basic (NaOH) and/or acid (citric acid and EDTA-2Na) treatment of ZSM-5 zeolite has been studied comparing the structural and acidic features and their catalytic performance in n-heptane cracking. The properties of the catalysts have been elucidated using XRD, N-2 low-temperature sorption, Al-27 and Si-29 NMR, pyridine adsorbed FTIR, NH3-TPD, SEM and TEM analysis. The results showed that the degree of desilication and dealumination of ZSM-5 zeolites was greatly dependent on the agents. NaOH obviously created new mesopores on parent ZSM-5 zeolites by desilication. Citric acid contributed to the removal of nonframework Al species, causing the increase of micropore surface area. EDTA-2Na promoted desilication and simultaneously converted part of removed framework Al species into nonframework Al species. The treatment of ZSM-5 combined with those three agents was very effective to obtain a hierarchical structure with partial breakdown of the crystallites and high acid amounts of both Bronsted and Lewis acid sites. Catalytic tests showed that the post-treated ZSM-5 catalysts had higher activity and stability than parent ZSM-5 catalyst at the same reaction temperature. The synergetic effect of Bronsted acid and Lewis acid of ZSM-5 catalyst (Z5-ACE) probably facilitated n-heptane conversion, while more clean micropore and newly created mesopores facilitated the slight increase of olefin selectivity and suppressing the formation of coke deposition in its inherent micropores to some extent.
机译：比较了结构和酸性特征及其在正庚烷裂解中的催化性能，研究了碱性（NaOH）和/或酸（柠檬酸和EDTA-2Na）处理ZSM-5沸石的效果。使用XRD，N-2低温吸附，Al-27和Si-29 NMR，吡啶吸附的FTIR，NH3-TPD，SEM和TEM分析阐明了催化剂的性能。结果表明，ZSM-5沸石的脱硅和脱铝程度在很大程度上取决于试剂。 NaOH显然会通过脱硅作用在ZSM-5母体沸石上产生新的中孔。柠檬酸有助于去除非骨架Al物种，从而导致微孔表面积的增加。 EDTA-2Na促进了脱硅作用，同时将部分去除的骨架Al物种转化为非骨架Al物种。 ZSM-5与这三种试剂的结合非常有效地获得了具有部分晶体分解和高酸量的布朗斯台德和路易斯酸位点的分层结构。催化测试表明，在相同反应温度下，后处理的ZSM-5催化剂比母体ZSM-5催化剂具有更高的活性和稳定性。 ZSM-5催化剂（Z5-ACE）的布朗斯台德酸和路易斯酸的协同作用可能促进了正庚烷转化，而更干净的微孔和新产生的中孔则促进了烯烃选择性的轻微增加并抑制了焦炭沉积在其中的形成。固有的微孔在一定程度上。

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