The dehydrogenation and cracking reactions of isobutane over the ZSM-5 zeolite

Milas, Ivan; Nascimento, Marco Antônio Chaer

doi:10.1016/s0009-2614(03)00611-0

Cited by 31 publications

(22 citation statements)

References 24 publications

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“…17 The dehydrogenation and cracking reactions of isobutene on zeolites were studied at the DFT/B3LYP level of quantum theory. 18,19 The protonation of propene, 1-hexene, and 3-hexene over the representative H-ZSM-5 cluster to give covalent alkoxide intermediates was theoretically studied by using the density functional theory (DFT) method. 20 However, mechanism details of n-butane cracking were not clarified because of the complexity of the reactions.…”

Section: Introductionmentioning

confidence: 99%

n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study

2008

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Density functional theory was used to study monomolecular cracking reaction of n-butane on acidic zeolite. Geometry optimizations of the local structures of the species reacting with the zeolite were carried out by using the 5T cluster model at the B3LYP/6-311＋G(3df,2p)//B3LYP/6-31G(d) level. In this work, the deprotonation modes of two different order C atoms in n-butane cracking on H-ZSM-5 were explored in detail by the density functional theory. The calculated activation barriers at the B3LYP/6-311＋G(3df,2p)//B3LYP/6-31G(d) level are 238 kJ/mol for the primary C-C cracking, 217 kJ/mol for the secondary C-C cracking, 296 kJ/mol for the primary dehydrogenation, and 242 kJ/mol for the secondary dehydrogenation, respectively. The difference of the activation barrier is 54 kJ/mol for the deprotonation reactions of two different order C atoms in n-butane. For the dehydrogenation reaction, the results indicate that the reaction is expected to be preferred at the secondary C atom. Additionally, the relation between the acidity and structure of the cluster shows that the acidity effect of the zeolite can be simulated by modifying the peripheral bonds of the cluster for the 5T cluster. Finally, the zeolite acidity effects on the reaction barriers were investigated by changing the cluster terminal Si-H bond length.

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Section: Introductionmentioning

confidence: 99%

n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study

2008

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“…The results suggested that the T9 and T10 are thermodynamically the more stables sites. Milas and Nascimento studied the interaction of isobutane with zeolites using DFT-B3LYP on a 5T [65] and a double-ring 20T clusters [66]. The results show that the activation energy decreases with increasing cluster size.…”

Section: Ab Initio Methods In Catalysismentioning

confidence: 99%

Application of computational methods to catalytic systems

Ruette

Sanchéz²,

Sierraalta

et al. 2005

Journal of Molecular Catalysis A: Chemical

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“…Milas ve Nascimento ise aynı reaksiyonları ZSM-5 zeoliti üzerinde incelemiştir. Her iki reaksiyonda da C-H ve C-C bağları yerine doğrudan yüzey aktif maddenin karbon atomuna atak yaptığı, daha gerideki aktif sitelerin parçalanma reaksiyonu üzerinden dehidrojenasyon reaksiyonunu meydana getirdiği tespit edilmiştir [9]. Sanchez-Castillo ve arkadaşları, H-mordenit ve β-zeolit üzerinde izobütan dönüşümü için reaksiyon kinetik verisi toplamıştır.…”

Section: Gi̇ri̇ş (Introduction)unclassified

İzobütan Dehi̇drojenasyonu İçi̇n Reaksi̇yon Mekani̇zmasinin Araştirilmasi

Çetinyokuş¹

2016

Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi

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ÖZETBu çalışmada, Cr/MCM-41 katalizörü üzerinde izobütan dehidrojenasyonu için reaksiyon mekanizmasının belirlenmesi amaçlanmıştır. Mekanizma çalışmalarına başlamadan önce deneysel reaksiyon hızlarının konsantrasyon ile değişimi değerlendirilmiş ve yüzey reaksiyonu kontrolünün önemli olduğu belirlenmiştir. Deneysel olarak belirlenen reaksiyon kinetik üssünün 1-2 arasında değişim göstermesi yüzey reaksiyonunun mono veya bimoleküler olabileceğini düşündürmüş, bu nedenle çok sayıda mekanizma çalışması arasından yüzey reaksiyon kontrollü (Model I&Model II) basit reaksiyon mekanizmaları üzerinde çalışılmıştır. Üs kuralına dayanan, çeşitli parametrelerin indirgenmesi ile elde edilen denklemler üzerinden de model (Model III) çalışması yürütülmüştür. Model çalışmalarına ait parametrelerin tahmininde SPSS 17,0 (Windows Evaluation Version) programından yararlanılmış doğrusal olmayan regresyon analizleri yapılmıştır. Model sonuçları ile deneysel reaksiyon hızı değerleri arasındaki en iyi uyum, bimoleküler yüzey reaksiyon kontrollü mekanizmada (Model I) belirlenmiştir. Reaksiyon için tahmin edilen aktivasyon enerjisi (49-55 kJ/mol) ve adsorpsiyon denge sabiti (1-3) parametre değerleri literatür ile uyumlu bulunmuştur.Anahtar Kelimeler: İzobütan dehidrojenasyonu, Cr/MCM-41, reaksiyon mekanizması, SPSS REACTION MECHANISM RESEARCH FOR ISOBUTANE DEHYDROGENATION ABSTRACTIn this study, determination of the reaction mechanism on Cr/MCM-41 catalyst for isobutane dehydrogenation was aimed. The change of experimental reaction rate values with concentration was evaluated before the beginning of the mechanism studies and it was determined that it was important to control surface reactions. The reaction order (n) obtained by experimantally for isobutane dehydrogenation showing exchanges between 1-2 indicated that surface reactions would be mono or bimolecular, so surface reaction controlled basic reaction mechanisms (Model I&Model II) were studied among many mechanism studies. On the equations obtained by reduction of various parameters (Model III) based on the rule of order were also studied. Nonlinear regression analysis were carried out to estimate the parameters of the model studies utilizing the SPSS 17.0 program (Windows Evaluation Version). The best agreement with the experimental reaction rate values was determined on the bimolecular surface reaction controlled mechanism (Model I). Parameter values of activation energy (49-55kj / mol) and the adsorpsion equilibrium constants (1-3) estimated for isobutane dehyrogenation reaction were consistent with the literature.

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The dehydrogenation and cracking reactions of isobutane over the ZSM-5 zeolite

Cited by 31 publications

References 24 publications

n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study

n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study

Application of computational methods to catalytic systems

İzobütan Dehi̇drojenasyonu İçi̇n Reaksi̇yon Mekani̇zmasinin Araştirilmasi

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