Understanding zeolite-catalyzed benzene methylation reactions by methanol and dimethyl ether at operating conditions from first principle microkinetic modeling and experiments

doi:10.1016/j.cattod.2018.02.042

Title: Understanding zeolite-catalyzed benzene methylation reactions by methanol and dimethyl ether at operating conditions from first principle microkinetic modeling and experiments

Abstract

In methanol-to-hydrocarbon chemistry, methanol and dimethyl ether (DME) can act as methylating agents. Therefore, in this paper we focus on the different reactivity of methanol and DME towards benzene methylation in H-ZSM-5 at operating conditions by combining first principles microkinetic modeling and experiments. Methylation reactions are known to follow either a concerted reaction path or a stepwise mechanism going through a framework-bound methoxide. By constructing a DFT based microkinetic model including the concerted and stepwise reactions, product formation rates can be calculated at conditions that closely mimic the experimentally applied conditions. Trends in measured rates are relatively well reproduced by our DFT based microkinetic model. We find that benzene methylation with DME is faster than with methanol but the difference decreases with increasing temperature. At low temperatures, the concerted mechanism dominates, however at higher temperatures and low pressures the mechanism shifts to the stepwise pathway. This transition occurs at lower temperatures for methanol than for DME, resulting in smaller reactivity differences between methanol and DME at high temperature. Finally, our theory-experiment approach shows that the widely assumed rate law with zeroth and first order in oxygenate and hydrocarbon partial pressure is not generally applicable and depends on the applied temperature,more » pressure and feed composition.« less

Authors:

^[1]; Martinez-Espin, Juan S. ^[2]; Hoffmann, Max J. ^[3]; Svelle, Stian ^[4]; Olsbye, Unni ^[4]; Bligaard, Thomas ^[3]

SLAC National Accelerator Lab., Menlo Park, CA (United States). SUNCAT Center for Interface Science and Catalysis; Stanford Univ., CA (United States). Dept. of Chemical Engineering; Ghent Univ. (Belgium). Center for Molecular Modeling
Univ. of Oslo (Norway). Centre for Materials Science and Nanotechnology. Dept. of Chemistry; Haldor Topsøe A/S, Kongens Lyngby (Denmark)
SLAC National Accelerator Lab., Menlo Park, CA (United States). SUNCAT Center for Interface Science and Catalysis; Stanford Univ., CA (United States). Dept. of Chemical Engineering
Univ. of Oslo (Norway). Centre for Materials Science and Nanotechnology. Dept. of Chemistry

Publication Date:: 2018-02-24

Research Org.:: SLAC National Accelerator Lab., Menlo Park, CA (United States); Ghent Univ. (Belgium); Univ. of Oslo (Norway)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Belgian American Educational Foundation (BAEF); Research Foundation - Flanders (FWO) (Belgium); European Union (EU)

OSTI Identifier:: 1461966

Alternate Identifier(s):: OSTI ID: 1591661

Grant/Contract Number:: AC02-76SF00515; 606965

Resource Type:: Accepted Manuscript

Journal Name:: Catalysis Today

Additional Journal Information:: Journal Volume: 312; Journal ID: ISSN 0920-5861

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; zeolites; methanol-to-hydrocarbons; microkinetic modeling; methylation; methanol; dimethyl ether

Citation Formats


                    De Wispelaere, Kristof, Martinez-Espin, Juan S., Hoffmann, Max J., Svelle, Stian, Olsbye, Unni, and Bligaard, Thomas. Understanding zeolite-catalyzed benzene methylation reactions by methanol and dimethyl ether at operating conditions from first principle microkinetic modeling and experiments.  United States: N. p., 2018. 
        Web.  doi:10.1016/j.cattod.2018.02.042.

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                    De Wispelaere, Kristof, Martinez-Espin, Juan S., Hoffmann, Max J., Svelle, Stian, Olsbye, Unni, & Bligaard, Thomas. Understanding zeolite-catalyzed benzene methylation reactions by methanol and dimethyl ether at operating conditions from first principle microkinetic modeling and experiments.  United States.  doi:10.1016/j.cattod.2018.02.042.

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                    De Wispelaere, Kristof, Martinez-Espin, Juan S., Hoffmann, Max J., Svelle, Stian, Olsbye, Unni, and Bligaard, Thomas. Sat .  
        "Understanding zeolite-catalyzed benzene methylation reactions by methanol and dimethyl ether at operating conditions from first principle microkinetic modeling and experiments".  United States.  doi:10.1016/j.cattod.2018.02.042.  https://www.osti.gov/servlets/purl/1461966.

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@article{osti_1461966,

  title        = {Understanding zeolite-catalyzed benzene methylation reactions by methanol and dimethyl ether at operating conditions from first principle microkinetic modeling and experiments},

  author       = {De Wispelaere, Kristof and Martinez-Espin, Juan S. and Hoffmann, Max J. and Svelle, Stian and Olsbye, Unni and Bligaard, Thomas},

  abstractNote = {In methanol-to-hydrocarbon chemistry, methanol and dimethyl ether (DME) can act as methylating agents. Therefore, in this paper we focus on the different reactivity of methanol and DME towards benzene methylation in H-ZSM-5 at operating conditions by combining first principles microkinetic modeling and experiments. Methylation reactions are known to follow either a concerted reaction path or a stepwise mechanism going through a framework-bound methoxide. By constructing a DFT based microkinetic model including the concerted and stepwise reactions, product formation rates can be calculated at conditions that closely mimic the experimentally applied conditions. Trends in measured rates are relatively well reproduced by our DFT based microkinetic model. We find that benzene methylation with DME is faster than with methanol but the difference decreases with increasing temperature. At low temperatures, the concerted mechanism dominates, however at higher temperatures and low pressures the mechanism shifts to the stepwise pathway. This transition occurs at lower temperatures for methanol than for DME, resulting in smaller reactivity differences between methanol and DME at high temperature. Finally, our theory-experiment approach shows that the widely assumed rate law with zeroth and first order in oxygenate and hydrocarbon partial pressure is not generally applicable and depends on the applied temperature, pressure and feed composition.},

  doi          = {10.1016/j.cattod.2018.02.042},

  journal      = {Catalysis Today},

  number       = ,

  volume       = 312,

  place        = {United States},

  year         = {2018},

  month        = {2}

}

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DOI: 10.1016/j.cattod.2018.02.042

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Figures / Tables:

Fig. 1: Schematical representation of the concerted and stepwise methylation mechanisms with MeOH or DME as reactant.

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