Acidity effect on benzene methylation kinetics over substituted H-MeAlPO-5 catalysts

• Published in: Journal of catalysis Vol. 404; pp. 594 - 606
• Main Authors: Mortén, Magnus, Cordero-Lanzac, Tomás, Cnudde, Pieter, Redekop, Evgeniy A., Svelle, Stian, van Speybroeck, Veronique, Olsbye, Unni
• Format: Journal Article
• Language: English; Norwegian
• Published: Elsevier Inc 01.12.2021
• Subjects: Acid strength; AlPO-5; Computational; Experimental; Kinetics; MeAlPO-5; MTG; MTH; MTO; MTH; AlPO-5; MTG; Experimental; MeAlPO-5; MTO; Kinetics; Acid strength; Computational
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2021.11.002

[Display omitted] •Acidity can be tuned by isomorphic substitution of H-MeAlPO-5 materials.•Static DFT calculations indicate a linear correlation between benzene methylation barriers and acid strength.•Experimental results corroborate computational trends with Mg-, Si- and ZrAlPO-5 catalysts.•Benzene methylation is hindered at high temperature and DME partial pressure.•MgAlPO-5 promotes a selective methylation of alkenes compared to SAPO-5 counterpart. Methylation of aromatic compounds is a key reaction step in various industrial processes such as the aromatic cycle of methanol-to-hydrocarbons chemistry. The study of isolated methylation reactions and of the influence of catalyst acidity on their kinetics is a challenging task. Herein, we have studied unidirectional metal-substituted H-MeAlPO-5 materials to evaluate the effect of acid strength on the kinetics of benzene methylation with DME. First-principle simulations showed a direct correlation between the methylation barrier and acid site strength, which depends on the metal substituent. Three H-MeAlPO-5 catalysts with high (Me = Mg), moderate (Me = Si) and low acidity (Me = Zr) were experimentally tested, confirming a linear relationship between the methylation activation energy and acid strength. The effects of temperature and reactant partial pressure were evaluated, showing significant differences in the byproduct distribution between H-MgAlPO-5 and H-SAPO-5. Comparison with propene methylation suggested that the Mg substituted catalyst is also the most active for the selective methylation of alkenes.