• Media type: E-Article
  • Title: Effect of aluminum and sodium on the sorption of water and methanol in microporous MFI-type zeolites and mesoporous SBA-15 materials
  • Contributor: Li, Zheng; Rieg, Carolin; Beurer, Ann-Katrin; Benz, Michael; Bender, Johannes; Schneck, Christof; Traa, Yvonne; Dyballa, Michael; Hunger, Michael
  • imprint: Springer Science and Business Media LLC, 2021
  • Published in: Adsorption
  • Language: English
  • DOI: 10.1007/s10450-020-00275-8
  • ISSN: 0929-5607; 1572-8757
  • Keywords: Surfaces and Interfaces ; General Chemical Engineering ; General Chemistry
  • Origination:
  • Footnote:
  • Description: <jats:title>Abstract</jats:title><jats:p>The interaction and nature of surface sites for water and methanol sorption on MFI-type zeolites and mesoporous SBA-15 were investigated by solid-state NMR spectroscopy and correlated with the desorption enthalpies determined via TGA/DSC. For siliceous Silicalite-1, <jats:sup>29</jats:sup>Si CPMAS NMR studies support stronger methanol than water interactions with SiOH groups of Q<jats:sup>3</jats:sup>-type. On siliceous SBA-15, SiOH groups of Q<jats:sup>2</jats:sup>-type are accompanied by an enhanced hydrophilicity. In aluminum-containing Na-ZSM-5, Na<jats:sup>+</jats:sup> cations are strong adsorption sites for water and methanol as evidenced by <jats:sup>23</jats:sup>Na MAS NMR in agreement with high desorption enthalpies of Δ<jats:italic>H</jats:italic> = 66–74 kJ/mol. Solid-state NMR of aluminum-containing Na-[Al]SBA-15, in contrast, has shown negligible water and methanol interactions with sodium and aluminum. Desorption enthalpies of Δ<jats:italic>H</jats:italic> = 44–60 kJ/mol hint at adsorption sites consisting of SiOH groups influenced by distant framework aluminum. On H-ZSM-5, Brønsted acidic OH groups are strong adsorption sites as indicated by partial protonation of water and methanol causing low-field shifts of their <jats:sup>1</jats:sup>H MAS NMR signals and enhanced desorption enthalpies. Due to the small number of Brønsted acid sites in aluminum-containing H-[Al]SBA-15, water and methanol adsorption on this material is suggested to mainly occur at SiOH groups with distant framework aluminum species, as in the case of Na-[Al]SBA-15.</jats:p>