Effect of variations in pore structure and acidity of alkali treated ZSM-5 on the isomerization performance
Effect of variations in pore structure and acidity of alkali treated ZSM-5 on the isomerization performance
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DOI：
10.1016/j.molcata.2009.06.006
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发表时间：
2009-09
影响因子：
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通讯作者：
Yueqin Song;Yan-Long Feng;Feng Liu;C. Kang;Xiao-long Zhou;Longya Xu;G. Yu
中科院分区：
文献类型：
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作者：
Yueqin Song;Yan-Long Feng;Feng Liu;C. Kang;Xiao-long Zhou;Longya Xu;G. Yu
制备了一系列碱处理的ZSM-5样品，考察了碱处理条件对正己烷异构化性能的影响。用X射线衍射仪、氮气吸附、X射线荧光、NH3-TPD、Py-IR和核磁共振等手段对ZSM-5进行了表征，结果表明，碱处理条件对ZSM-5的结晶度、织构性质、硅铝比和酸性有影响。轻度碱处理使催化剂的强酸中心减少，孔结构没有明显改变，而强碱处理则产生了较强的酸性中心和新的中孔。建立了酸度、孔结构和异构化行为之间的关系。结果表明，正己烷的转化率与强酸中心的数量有关，与酸中心的性质和孔结构无关。但对异己烷的选择性与催化剂的酸性和孔结构无关。异构体中二甲基丁烷(DMB)和甲基戊烷(MP)的相对含量不仅与ZSM-5的孔结构有关，而且与ZSM-5的酸性有关。适宜的碱处理条件有利于提高同分异构体的产率和生成更多的DMB。
A series of alkali treated ZSM-5 samples were prepared and the effects of the alkali treatment conditions on the n-hexane isomerization performance of Pt/ZSM-5 were investigated. The characterization by XRD, N2-adsorption, XRF, NH3-TPD, Py-IR and NMR revealed that alkali treatment conditions had the effects on the crystallinity, textural property, Si/Al ratio and acidity of ZSM-5. Mild alkali treatment led to the reduction of the strong acid sites and did not distinctly change the pore structure, whereas severe alkali treatment resulted in the creation of the stronger acid sites and new mesopores. The correlation of the acidity and pore structure and isomerization behavior was established. It was proposed that the conversion of n-hexane was dependent on the amount of strong acid sites and irrelevant to the properties of acid sites and the pore structure. However, the selectivity for iso-hexanes was irrelevant to both the acidity and pore structure. The relative amount of dimethylbutanes (DMB) and methylpentanes (MP) in isomers was related not only to the pore structure, but to the acidity of ZSM-5. The suitable alkali treatment condition facilitated the high yield of isomers and the formation of more DMB.