Complete low-barrier side-chain route for olefin formation during methanol conversion in H-SAPO-34

• Published in: Journal of catalysis 2013-09, Vol.305, p.76-80
• Main Authors: De Wispelaere, Kristof, Hemelsoet, Karen, Waroquier, Michel, Van Speybroeck, Veronique
• Format: Article
• Language: English
• Subjects: carbon; Catalysis; Chemical reactions; Chemistry; energy; ethylene; ethylene production; Exact sciences and technology; First-principle kinetics; General and physical chemistry; H-SAPO-34; Heterogeneous catalysis; Ion-exchange; Kinetics; Methanol; Methanol to olefin; olefin; propylene; reaction mechanisms; Side-chain mechanism; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites; Zeolites: preparations and properties
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2013.04.015

A first-principle kinetic study reveals a full low-barrier catalytic cycle for both ethene and propene during methanol conversion in H-SAPO-34. Starting from hexamethylbenzene trapped in the catalyst, an alkyl chain grows and can be eliminated in a water-assisted reaction step. [Display omitted] •A low-barrier path for olefin formation in H-SAPO-34 is found.•Reaction cycle based on the side-chain mechanism starting from HMB.•All free energy barriers below 100kJ/mol.•Non-bonding interactions and water assistance.•Impulse for further experimental and theoretical studies. The methanol to olefins process is an alternative for oil-based production of ethene and propene. However, detailed information on the reaction mechanisms of olefin formation in different zeolite is lacking. Herein, a first-principle kinetic study allows elucidating the importance of a side-chain mechanism during methanol conversion in H-SAPO-34. Starting from the experimentally observed hexamethylbenzene, a full low-barrier catalytic cycle for ethene and propene formation is found. The olefin elimination steps exhibit low free energy barriers due to a subtle interplay between a sp3 carbon center of the organic intermediate, stabilizing non-bonding interactions and assisting water molecules in the zeolite material.