On the Reaction Mechanism for Hydrocarbon Formation from Methanol over SAPO-34

Dahl, Ivar M.; Kolboe, Stein

doi:10.1006/jcat.1996.0188

Cited by 628 publications

(237 citation statements)

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“…19 During the induction period, a hydrocarbon pool (HP) is formed, taking the role as co-catalysts for product formation. 6,[20][21][22][23][24] So far there is no full consensus concerning the mechanism governing the formation of such HP species. [25][26][27] One possibility concerns condensation reactions between initially formed ethene and/or propene, which might undergo oligomerization and cyclization reactions.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

et al. 2016

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The role of water in the methanol-to-olefins (MTO) process over H- has been elucidated by a combined theoretical and experimental approach, encompassing advanced molecular dynamics simulations and in-situ micro-spectroscopy. First principle calculations at the molecular level point out that water competes with methanol and propene for direct access to the Brønsted acid sites. This results in less efficient activation of these molecules, which are crucial for the formation of the hydrocarbon pool. Furthermore, lower intrinsic methanol reactivity towards methoxide formation has been observed. These observations are in line with a longer induction period observed from in-situ UV-Vis micro-spectroscopy experiments. These experiments revealed a slower and more homogeneous discoloration of H-SAPO-34, while insitu confocal fluorescence microscopy confirmed the more homogeneous distribution and larger amount of MTO intermediates when co-feeding water. As such it is show that water induces a more efficient use of the H-SAPO-34 catalyst crystals at the microscopic level. The combined experimental theoretical approach gives a profound insight into the role of water on the catalytic process at the molecular and single particle level.

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Section: Introductionmentioning

confidence: 99%

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

et al. 2016

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“…The actual reaction mechanism is particularly complex and consists of many parallel routes. There is now general consensus about the hydrocarbon pool (HP) mechanism assuming that organic reaction centres act as co-catalysts inside the zeolite pores [2,3,4,5,6]. The HP intermediates serve as platforms to which C 1 species can add and from which primary olefin products can dissociate.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical IR study of methanol and ethanol conversion over H-SAPO-34

Hemelsoet

Ghysels

et al. 2011

Catalysis Today

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Theoretical and experimental IR data are combined to gain insight into the methanol and ethanol conversion over an acidic H-SAPO-34 catalyst. The theoretical simulations use a large finite cluster and the initial physisorption energy of both alcohols is calculated.Dispersive contributions turn out to be vital and the final adsorption of ethanol is predicted to be stronger compared to methanol (difference of 14 kJ mol −1 ). Calculated IR spectra of the alcohols and of formed aromatic cations upon conversion are also analyzed and support the peak assignment of the experimental in situ DRIFT spectra, in particular for the C-H and C=C regions. Theoretical IR spectra of the gas phase compounds are compared with those of the molecules loaded in a SAPO cluster and the observed shifts of the peak positions are discussed. To get a better understanding of these framework-guest interactions, a new theoretical procedure is proposed based on a normal mode analysis.A cumulative overlap function is defined and enables the characterization of individual peaks as well as induced frequency shifts upon adsorption.

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“…Although the catalyst samples were fairly resistant toward deactivation, a slight loss of activity was observed. This was corrected for using previously described procedures [6,8]. A primary concern has been to study the catalytic system at low conversion (i.e., high feed rates) to prevent side reactions, while still operating at a realistic reaction temperature and catalyst acid site density.…”

Section: Kinetic Measurementsmentioning

confidence: 99%

“…At present, MTO is one of the most prominent alternatives to crude-oil cracking for the production of light olefins such as ethene and propene [5]. The exact mechanism underlying the conversion process has been debated for decades, but currently there is a consensus on an indirect mechanism in which methanol is converted to light olefins via repeated methylation and/or cracking reactions of a pool of hydrocarbons present inside the zeolite pores [6][7][8][9][10][11][12][13]. In every catalytic cycle proposed to date to explain olefin formation, methylations were found to be key reaction steps [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Methylation of benzene by methanol: Single-site kinetics over H-ZSM-5 and H-beta zeolite catalysts

Mynsbrugge

Visur

Olsbye

et al. 2012

Journal of Catalysis

129

126

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Benzene methylation by methanol is studied on acidic zeolites H-ZSM-5 (MFI) and H-beta (BEA) to investigate the influence of the catalyst topology on the reaction rate. Experimental kinetic measurements at 350 °C using extremely high feed rates to suppress side reactions show that methylation occurs considerably faster on H-ZSM-5 than on H-beta. Theoretical rate constants, obtained from first-principles simulations on extended zeolite clusters, reproduce a higher methylation rate on H-ZSM-5 and provide additional insight into the various molecular effects that contribute to the overall differences between the two catalysts. The calculations indicate this higher methylation rate is primarily due to an optimal confinement of the reacting species in the medium pore material. Co-adsorption of methanol and benzene is energetically favored in H-ZSM-5 compared with H-beta, to the extent that the stabilizing host-guest interactions outweigh the greater entropy loss upon benzene adsorption in H-ZSM-5 vs. in Hbeta.

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On the Reaction Mechanism for Hydrocarbon Formation from Methanol over SAPO-34

Cited by 628 publications

References 0 publications

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

Insight into the Effect of Water on the Methanol-to-Olefins Conversion in H-SAPO-34 from Molecular Simulations and in Situ Microspectroscopy

Experimental and theoretical IR study of methanol and ethanol conversion over H-SAPO-34

Methylation of benzene by methanol: Single-site kinetics over H-ZSM-5 and H-beta zeolite catalysts

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