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Impact of Zeolite Structure on Entropic–Enthalpic Contributions to Alkane Monomolecular Cracking: An IR Operando Study
Chemistry - A European Journal ( IF 3.9 ) Pub Date : 2018-03-24 , DOI: 10.1002/chem.201800793
Shashikant A. Kadam 1 , Haoguang Li 1 , Richard F. Wormsbecher 1 , Arnaud Travert 1
Affiliation  

The monomolecular cracking rates of propane and n‐butane over MFI, CHA, FER and TON zeolites were determined simultaneously with the coverage of active sites at reaction condition using IR operando spectroscopy. This allowed direct determination of adsorption thermodynamics and intrinsic rate parameters. The results show that the zeolite confinement mediates enthalpy–entropy trade‐offs only at the adsorbed state, leaving the true activation energy insensitive to the zeolite or alkane structure while the activation entropy was found to increase with the confinement. Hence, relative cracking rates of alkanes within zeolite pores are mostly governed by activation entropy.

中文翻译:

沸石结构对链烷烃单分子裂解的熵焓贡献的影响:红外研究

使用红外操作光谱法同时测定反应条件下活性位点的覆盖率,同时测定MFI,CHA,FER和TON分子筛上丙烷和丁烷的单分子裂解率。这样就可以直接确定吸附热力学和固有速率参数。结果表明,仅在吸附状态下,沸石限制介导了焓-熵的折衷,使真实的活化能对沸石或烷烃结构不敏感,而活化熵随限制而增加。因此,沸石孔内烷烃的相对裂解率主要受活化熵控制。
更新日期:2018-03-24
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