Hierarchical ZSM-5 zeolite designed by combining desilication and dealumination with related study of n-heptane cracking performance
Hierarchical ZSM-5 zeolite designed by combining desilication and dealumination with related study of n-heptane cracking performance
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脱硅脱铝结合设计多级ZSM-5沸石及正庚烷裂解性能相关研究
DOI：
10.1007/s10934-018-0587-2
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发表时间：
2018-12-01
影响因子：
2.6
通讯作者：
Lin, Jiawei
中科院分区：
文献类型：
--
作者：
Feng, Rui;Yan, Xinlong;Lin, Jiawei
研究了碱（NaOH）和酸（柠檬酸和EDTA-2Na）处理ZSM-5分子筛的效果，比较了它们的结构和酸性特征及其在正庚烷裂解中的催化性能。采用XRD、N2低温吸附、27 Al和29 Si NMR、吡啶吸附FTIR、NH3-TPD、SEM和TEM等手段对催化剂的性能进行了表征。结果表明，ZSM-5分子筛的脱硅、脱铝程度与脱硅剂有很大关系。NaOH脱硅明显地在ZSM-5分子筛上生成了新的介孔。柠檬酸有助于去除非骨架铝物种，导致铝比表面积增加。EDTA-2Na促进脱硅的同时，也使部分脱硅的骨架铝形态转化为非骨架铝形态。ZSM-5与这三种试剂组合的处理非常有效地获得了具有部分破坏的微晶和高酸量的布朗斯台德和刘易斯酸中心的分级结构。催化性能测试表明，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）中的Brönsted酸和刘易斯酸的协同作用可能促进了正庚烷的转化，而更清洁的沸石和新生成的介孔有助于烯烃选择性的略微提高，并在一定程度上抑制了其固有微孔中的积炭。
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, N2low-temperature sorption,27Al and29Si 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 Brönsted 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 Brönsted 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.