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Insight into the Role of Water on the Methylation of Hexamethylbenzene in H‐SAPO‐34 from First Principle Molecular Dynamics Simulations

Simon Bailleul (UGent) , Sven Rogge (UGent) , Louis Vanduyfhuys (UGent) and Veronique Van Speybroeck (UGent)
(2019) ChemCatChem. p.3993-4010
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Abstract
The methylation of hexamethylbenzene with methanol is one of the key reactions in the methanol-to-olefins hydrocarbon pool reaction cycle taking place over the industrially relevant H-SAPO-34 zeolite. This methylation reaction can occur either via a concerted or via a stepwise mechanism, the latter being the preferred pathway at higher temperatures. Herein, we systematically investigate how a complex reaction environment with additional water molecules and higher concentrations of Brønsted acid sites in the zeolite impacts the reaction mechanism. To this end, first principle molecular dynamics simulations are performed using enhanced sampling methods to characterize the reactants and products in the catalyst pores and to construct the free energy profiles. The most prominent effect of the dynamic sampling of the reaction path is the stabilization of the product region where water is formed, which can either move freely in the pores of the zeolite or be stabilized through hydrogen bonding with the other protic molecules. These protic molecules also stabilize the deprotonated Brønsted acid site, created due to the formation of the heptamethylbenzenium cation, via a Grotthuss-type mechanism. Our results provide fundamental insight in the experimental parameters that impact the methylation of hexamethylbenzene in H-SAPO-34, especially highlighting and rationalizing the crucial role of water in one of the main reactions of the aromatics-based reaction cycle.
Keywords
Physical and Theoretical Chemistry, Inorganic Chemistry, Organic Chemistry, Catalysis

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Chicago
Bailleul, Simon, Sven Rogge, Louis Vanduyfhuys, and Veronique Van Speybroeck. 2019. “Insight into the Role of Water on the Methylation of Hexamethylbenzene in H‐SAPO‐34 from First Principle Molecular Dynamics Simulations.” ChemCatChem: 3993–4010.
APA
Bailleul, S., Rogge, S., Vanduyfhuys, L., & Van Speybroeck, V. (2019). Insight into the Role of Water on the Methylation of Hexamethylbenzene in H‐SAPO‐34 from First Principle Molecular Dynamics Simulations. ChemCatChem, 3993–4010.
Vancouver
1.
Bailleul S, Rogge S, Vanduyfhuys L, Van Speybroeck V. Insight into the Role of Water on the Methylation of Hexamethylbenzene in H‐SAPO‐34 from First Principle Molecular Dynamics Simulations. ChemCatChem. 2019;3993–4010.
MLA
Bailleul, Simon et al. “Insight into the Role of Water on the Methylation of Hexamethylbenzene in H‐SAPO‐34 from First Principle Molecular Dynamics Simulations.” ChemCatChem (2019): 3993–4010. Print.
@article{8627782,
  abstract     = {The methylation of hexamethylbenzene with methanol is one of the key reactions in the methanol-to-olefins hydrocarbon pool reaction cycle taking place over the industrially relevant H-SAPO-34 zeolite. This methylation reaction can occur either via a concerted or via a stepwise mechanism, the latter being the preferred pathway at higher temperatures. Herein, we systematically investigate how a complex reaction environment with additional water molecules and higher concentrations of Brønsted acid sites in the zeolite impacts the reaction mechanism. To this end, first principle molecular dynamics simulations are performed using enhanced sampling methods to characterize the reactants and products in the catalyst pores and to construct the free energy profiles. The most prominent effect of the dynamic sampling of the reaction path is the stabilization of the product region where water is formed, which can either move freely in the pores of the zeolite or be stabilized through hydrogen bonding with the other protic molecules. These protic molecules also stabilize the deprotonated Brønsted acid site, created due to the formation of the heptamethylbenzenium cation, via a Grotthuss-type mechanism. Our results provide fundamental insight in the experimental parameters that impact the methylation of hexamethylbenzene in H-SAPO-34, especially highlighting and rationalizing the crucial role of water in one of the main reactions of the aromatics-based reaction cycle.},
  author       = {Bailleul, Simon and Rogge, Sven and Vanduyfhuys, Louis and Van Speybroeck, Veronique},
  issn         = {1867-3880},
  journal      = {ChemCatChem},
  keywords     = {Physical and Theoretical Chemistry,Inorganic Chemistry,Organic Chemistry,Catalysis},
  language     = {eng},
  pages        = {3993--4010},
  title        = {Insight into the Role of Water on the Methylation of Hexamethylbenzene in H‐SAPO‐34 from First Principle Molecular Dynamics Simulations},
  url          = {http://dx.doi.org/10.1002/cctc.201900618},
  year         = {2019},
}

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