Chapter 6. Shape selectivity in zeolite catalysis. The Methanol to Hydrocarbons (MTH) reaction

Teketel, Shewangizaw; Erichsen, Marius Westgård; Bleken, Francesca Lønstad; Svelle, Stian; Lillerud, Karl Petter; Olsbye, Unni

doi:10.1039/9781782620037-00179

Cited by 42 publications

(43 citation statements)

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“…This distribution is typical of previous reports of MTG chemistry over ZSM-5 [1][2][3], although it is recognised that the catalyst is in the early stages of its reaction cycle with, for example, little evidence of a coking stage active over the short reaction period studied. This assumption is consistent with the observation that, post-reaction, the originally white pellets had changed to a mild grey colour; cutting across the pellet column revealed that the grey colouration was only present at the catalyst surface, with the inside of the pellets retaining their original clean white colouration.…”

Section: Reaction Testingmentioning

confidence: 63%

“…The past 30 years have seen numerous investigations of the reaction pathways and mechanisms by which methanol is converted to hydrocarbons over acid zeotype catalysts, as reviewed recently for example in references [1][2][3][4]. Three different components of the reaction pathway can be distinguished: (1) the initial reaction steps in which methanol reacts with acid sites in the zeolite or SAPO catalysts; (2) the formation of hydrocarbon products during steady-state working conditions; and (3) the catalyst deactivation through so-called coke formation.…”

Section: Introductionmentioning

confidence: 99%

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Application of Inelastic Neutron Scattering to the Methanol-to-Gasoline Reaction Over a ZSM-5 Catalyst

et al. 2016

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Inelastic neutron scattering (INS) is used to investigate a ZSM-5 catalyst that has been exposed to methanol vapour at elevated temperature. In-line mass spectrometric analysis of the catalyst exit stream confirms methanol-to-gasoline chemistry, whilst ex situ INS measurements detect hydrocarbon species formed in/on the catalyst during methanol conversion. These preliminary studies demonstrate the capability of INS to complement infrared spectroscopic characterisation of the hydrocarbon pool present in/on ZSM-5 during the MTG reaction. Graphical Abstract& David Lennon

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Section: Reaction Testingmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Application of Inelastic Neutron Scattering to the Methanol-to-Gasoline Reaction Over a ZSM-5 Catalyst

et al. 2016

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“…Previous studies on this structure demonstrated that the largest observed major product during methanol conversion is the same as during homogeneous methanol conversion, i.e. hexamethylbenzene (hexaMB) [36,37]. Thus, the AFI topology apparently provides limited, if any, product shape selectivity.…”

Section: Introductionmentioning

confidence: 93%

How zeolitic acid strength and composition alter the reactivity of alkenes and aromatics towards methanol

Erichsen

Wispelaere

Hemelsoet

et al. 2015

Journal of Catalysis

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a b s t r a c tThis work encompasses a combined experimental and theoretical assessment of how zeolitic acid strength and composition affects acid-catalysed methylation reactions. Overall, higher methylation rates were observed over the material with higher acid strength. Co-reactions of methanol with benzene at 250°C over the two isostructural AFI materials H-SSZ-24 and H-SAPO-5 revealed large differences in selectivity. While the stronger acidic H-SSZ-24 mainly produced toluene and polymethylbenzenes, high yields of C 4+ aliphatics were observed over H-SAPO-5. These results strongly suggest that alkene methylation was preferred over H-SAPO-5 even at very low conversion during methanol/benzene co-reactions. Furthermore, a comparison of benzene and propene methylation at 350-400°C revealed a significantly faster rate of benzene than propene methylation in H-SSZ-24, whereas the rates of benzene and propene methylation were similar in H-SAPO-5. The observed difference in reactivity of the two hydrocarbons in both catalysts could be understood by careful analysis of various molecular dynamics simulations of the co-adsorbed complexes. The probability to form protonated methanol was, as expected, higher in the more acidic material. However, in H-SSZ-24, the probability for methanol protonation was higher when co-adsorbed with benzene than when co-adsorbed with propene, while the same was not observed in H-SAPO-5. Furthermore, it was found that benzene and methanol are more likely to form a reactive co-adsorbed complex in H-SSZ-24 compared to propene and methanol, while the opposite was observed for H-SAPO-5. This work shows that molecular dynamics simulations provide insights into the adsorption behaviour of guest molecules in large pore AFI materials. The obtained insights correlate with the experimentally observed reactivities.

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“…2 Many excellent reviews have been published about the MTH process, covering early studies with focus on industrial development and process chemistry, via two decades of studies focusing on mechanistic insight and shape selectivity, to recent studies devoted to single reaction steps and the elucidation of confinement effects by quantum chemistry and molecular dynamics calculations, alone or in combination with experimental studies. He received his PhD from the same institution in 2004.…”

Section: S Svellementioning

confidence: 99%

“…The structures of generated carbenium ions depend on the pore systems of zeolite catalysts. In addition, the structures, the compositions and the evolution mechanism of HCP species are not clear yet despite the fact that olefins are (2) believed to form through repeated methylation and/or cracking of a pool of hydrocarbons, e.g. polymethylcyclopentenyl, [25][26][27][28][29][30][31][32][33][34] polymethylbenzenium, 25,30,[35][36][37][38] and dienylic carbenium, 25,26,39 were recently observed in H-ZSM-5, H-beta, H-SSZ-13 and H-DNL-6 with 13 C NMR spectroscopy (see Table 1), UV/vis spectroscopy and confirmed by theoretical calculations.…”

Section: 1 Recent Progress In Understanding the Hydrocarbon Pool Mecmentioning

confidence: 99%

The formation and degradation of active species during methanol conversion over protonated zeotype catalysts

et al. 2015

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The methanol to hydrocarbon (MTH) process provides an efficient route for the conversion of carbon-based feedstocks into olefins, aromatics and gasoline. Still, there is room for improvements in product selectivity and catalytic stability. This task calls for a fundamental understanding of the formation, catalytic mechanism and degradation of active sites. The autocatalytic feature of the MTH process implies that hydrocarbons are active species on the one hand and deactivating species on the other hand. The steady-state performance of such species has been thoroughly studied and reviewed. However, the mechanism of formation of the initial hydrocarbon species (i.e.; the first C-C bond) and the evolution of active species into deactivating coke species have received less attention. Therefore, this review focuses on the significant progress recently achieved in these two stages by a combination of theoretical calculations, model studies, operando spectroscopy and catalytic tests.

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Chapter 6. Shape selectivity in zeolite catalysis. The Methanol to Hydrocarbons (MTH) reaction

Cited by 42 publications

References 0 publications

Application of Inelastic Neutron Scattering to the Methanol-to-Gasoline Reaction Over a ZSM-5 Catalyst

Application of Inelastic Neutron Scattering to the Methanol-to-Gasoline Reaction Over a ZSM-5 Catalyst

How zeolitic acid strength and composition alter the reactivity of alkenes and aromatics towards methanol

The formation and degradation of active species during methanol conversion over protonated zeotype catalysts

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