Active sites of a [B]-ZSM-5 zeolite catalyst for the Beckmann rearrangement of cyclohexanone grime to caprolactam
Active sites of a [B]-ZSM-5 zeolite catalyst for the Beckmann rearrangement of cyclohexanone grime to caprolactam
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DOI：
10.1006/jcat.2000.2928
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发表时间：
2000-08-15
影响因子：
7.3
通讯作者：
Hölderich, WF
中科院分区：
文献类型：
--
作者：
Heitmann, GP;Dahlhoff, G;Hölderich, WF
[B]-ZSM-5是用于环己酮肟气相贝克曼重排为ε-己内酰胺的非常活性和选择性的催化剂，在300 ℃和100 mbar下在完全初始转化时具有高达95%的高选择性。[B]-ZSM-5上催化活性位点的性质通过研究合成后改性的影响来确定，在空气中煅烧、酸/碱处理和水热处理对选择性的影响。用FT-IR研究了[B]-ZSM-5分子筛表面的各种羟基和硅醇巢是贝克曼重排反应的活性中心。进一步的研究表明，吸附水对[B]-ZSM-5的催化活性有负面影响，导致其催化活性下降。这种效果被证明是可逆的，可以解释与表面上的氧化硼物种的水合作用。用合成后原样和已经煅烧的[B]-ZSM-5的实验显示了氧化硼物质的影响，其与不含骨架外硼的材料相比将转化率从70%提高到98%。(C)北京大学出版社.
[B]-ZSM-5 is a very active and selective catalyst for the vapor-phase Beckmann rearrangement of cyclohexanone oxime to epsilon-caprolactam with high selectivities of up to 95% at 300 degrees C and 100 mbar at complete initial conversion. The nature of the catalytically active sites on [B]-ZSM-5 was determined by investigating the influence of postsynthesis modifications, e.g., calcination under air, acid/base treatment, and hydrothermal treatment on the selectivity. Using FT-IR various hydroxyl groups and silanol nests on the surface of the [B]-ZSM-5 zeolites were found to be the active sites for the Beckmann rearrangement. Further investigations concerned the negative effect of adsorbed water on [B]-ZSM-5, which led to a decrease of its catalytic activity. This effect was shown to be reversible and could be explained with the hydration of boron oxide species on the surface. Experiments with as-synthesized and already calcined [B]-ZSM-5 showed the influence of the boron oxide species, which enhanced the conversion compared to the material without extraframework boron from 70% to 98%. (C) 2000 Academic Press.