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This content will become publicly available on February 24, 2019

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

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:
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [3]
  1. 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
  2. Univ. of Oslo (Norway). Centre for Materials Science and Nanotechnology. Dept. of Chemistry; Haldor Topsøe A/S, Kongens Lyngby (Denmark)
  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
  4. Univ. of Oslo (Norway). Centre for Materials Science and Nanotechnology. Dept. of Chemistry
Publication Date:
Grant/Contract Number:
AC02-76SF00515; 606965
Type:
Accepted Manuscript
Journal Name:
Catalysis Today
Additional Journal Information:
Journal Volume: 312; Journal ID: ISSN 0920-5861
Publisher:
Elsevier
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)
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
OSTI Identifier:
1461966