Benzene co-reaction with methanol and dimethyl ether over zeolite and zeotype catalysts: Evidence of parallel reaction paths to toluene and diphenylmethane

Martínez-Espín, Juan S.; Wispelaere, Kristof De; Erichsen, Marius Westgård; Svelle, Stian; Janssens, Ton V. W.; Speybroeck, Véronique Van; Beato, Pablo; Olsbye, Unni

doi:10.1016/j.jcat.2017.03.007

Cited by 73 publications

(91 citation statements)

References 265 publications

(416 reference statements)

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“…Furthermore, previous mechanistic studies point to a reaction between sorbed species as the rate‐determining step of both hydrogen‐transfer reactions (leading to the first C−C bond formation; i.e. to initiation of the MTH reaction) and alkene/arene methylation reactions (the propagation reactions of the dual‐cycle MTH mechanism) . The rate of such reactions generally increases upon increasing the coverage of the active site, which is, in this case, induced by a higher acid strength.…”

Section: Resultsmentioning

confidence: 97%

“…Recently, however, studies in which methanol and DME were compared as methylating agents of benzene and isobutene, mainly over H‐ZSM‐5, yielded new insight into these reactions. Briefly, the studies revealed a key role of methanol and DME as hydrogen‐transfer agents between the alkene and arene cycles, as well as between monocyclic arenes and heavier analogues . Furthermore, hydrogen‐transfer reactions were found to take place at the Brønsted acid sites, whereas isolated Lewis acid sites had negligible activity for both the methylation and hydrogen‐transfer reactions .…”

Section: Resultsmentioning

confidence: 99%

“…Methane formation from two DME molecules via a methoxy methylene species was recently directly linked to the formation of the first C−C bond in the MTH reaction . Whereas such a direct hydrogen transfer between two oxygenate molecules is feasible, the activation energy of this reaction is far higher than that for hydrogen transfer from a DME or methanol molecule to an adjacent alkene molecule . Methane formation associated with the MTH initiation reaction is, therefore, assumed to take place mainly in the first part of the reactor, in which the concentration of hydrocarbons is negligible .…”

Section: Resultsmentioning

confidence: 99%

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A Systematic Study of Isomorphically Substituted H‐MAlPO‐5 Materials for the Methanol‐to‐Hydrocarbons Reaction

et al. 2017

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Substituting metals for either aluminum or phosphorus in crystalline, microporous aluminophosphates creates Brønsted acid sites, which are well known to catalyze several key reactions, including the methanol to hydrocarbons (MTH) reaction. In this work, we synthesized a series of metal‐substituted aluminophosphates with AFI topology that differed primarily in their acid strength and that spanned a predicted range from high Brønsted acidity (H‐MgAlPO‐5, H‐CoAlPO‐5, and H‐ZnAlPO‐5) to medium acidity (H‐SAPO‐5) and low acidity (H‐TiAlPO‐5 and H‐ZrAlPO‐5). The synthesis was aimed to produce materials with homogenous properties (e.g. morphology, crystallite size, acid‐site density, and surface area) to isolate the influence of metal substitution. This was verified by extensive characterization. The materials were tested in the MTH reaction at 450 °C by using dimethyl ether (DME) as feed. A clear activity difference was found, for which the predicted stronger acids converted DME significantly faster than the medium and weak Brønsted acidic materials. Furthermore, the stronger Brønsted acids (Mg, Co and Zn) produced more light alkenes than the weaker acids. The weaker acids, especially H‐SAPO‐5, produced more aromatics and alkanes, which indicates that the relative rates of competing reactions change upon decreasing the acid strength.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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A Systematic Study of Isomorphically Substituted H‐MAlPO‐5 Materials for the Methanol‐to‐Hydrocarbons Reaction

et al. 2017

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“…Here, further dehydration of the oxonium ion intermediates formed to surface methoxy groups when heated in the TPD experiment occurs with equal propensity due to equal stability of the methoxy group formation with DME or methanol adsorption. Also, the probability for DME protonation is about 2 times higher than methanol suggesting higher tendencies towards larger activation energies of desorption for DME [51].…”

Section: Comparing Desorption Of Methanol To Dmementioning

confidence: 96%

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

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The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a temporal analysis of products reactor. The catalysts were characterized by XRD, SEM, N 2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage. Graphical AbstractElectronic supplementary material The online version of this article (https://doi

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“…Martinez-Espin et al [34] have compared DTH vs. MTH a variety of catalyst (including H-ZSM-5 zeolite) concluding that the former has the following benefits compared with the latter: higher activity, lower yield of aromatics and ethylene (normally regarded as a secondary interest product) and slower deactivation. The same group [35,36] has pointed to the fact that DTH is faster than MTH is due to the faster and thermodynamically favored methylation over hydrogen transfer reactions (in principle unwanted). Li et al [37] proved similar behavior when SAPO-34 catalyst is used.…”

Section: Introductionmentioning

confidence: 99%

Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

et al. 2019

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The conversions into hydrocarbons of methanol, dimethyl ether and chloromethane (MTH, DTH and CTH, respectively) on a H‐ZSM‐5 zeolite catalyst were compared trough ab‐initio calculations and experiments, using a fixed‐bed reactor and in‐situ FTIR spectroscopy. The molecular modelling of the reaction was performed using force field calculations. The nature and location of retained species were assessed by a combination of techniques. The experimental results of activity, product distribution and deactivation match these of the molecular modelling as the three reactions proceed through the dual‐cycle mechanism. However, the initiation, evolution and degradation of hydrocarbon pool species are kinetically different depending on the reactant. The reactions are faster in the order DTH>MTH≫CTH whereas the rate at which coke forms and grows (linked with the rate of deactivation) is in the order CTH≫DTH>MTH.

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Benzene co-reaction with methanol and dimethyl ether over zeolite and zeotype catalysts: Evidence of parallel reaction paths to toluene and diphenylmethane

Cited by 73 publications

References 265 publications

A Systematic Study of Isomorphically Substituted H‐MAlPO‐5 Materials for the Methanol‐to‐Hydrocarbons Reaction

A Systematic Study of Isomorphically Substituted H‐MAlPO‐5 Materials for the Methanol‐to‐Hydrocarbons Reaction

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

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