H, ²H, and ¹³C Solid-State NMR Studies of Methanol Adsorbed on a Series of Acidic Microporous Zeotype Materials

Abstract

Adsorption of 13CH3OH, CH3OD, CD3OH, and CD3OD on well characterized H-ZSM-5, H-M, H-SAPO-5, FAU type H-Y, and EMT type H-Y microporous materials at various coverages has been studied by using 1H and 13C MASNMR. At low methanol coverages the more acidic molecular sieves are able to protonate methanol molecules producing adsorbed methoxonium ions. In less acidic materials hydrogen bonding occurs involving the Brønsted acid site. As the coverage increases methanol clusters form and the bonding within these clusters weakens as demonstrated by the 1H MASNMR chemical shift trends. This bond weakening gives rise to an increase in mobility of methanol molecules adsorbed within H-ZSM-5 channels and is confirmed by 2H static wide-line spectra of CH3OD adsorbed on D-ZSM-5.

Electrochemically controlled ion exchange: proton ion exchange with sodium zeolite X and A

“…The aluminium content of the samples was examined indirectly by 29 Si-MASNMR. Samples were prepared by heating under vacuum at a rate of 50 K h −1 to 573 K. The samples were held under these conditions (573 K, 0.1 mbar) for a further 24 h before sealing, under vacuum, in a glass ampoule [18,19]. Si-MASNMR, respectively.…”

In situ IR, NMR, EPR, and UV/Vis Spectroscopy: Tools for New Insight into the Mechanisms of Heterogeneous Catalysis

“…A large number of 13 C MAS NMR investigations is concerned with the conversion of methanol into hydrocarbons (MTG: m ethanol to g asoline, MTO: m ethanol t o o lefins) on acid zeolites under batch conditions, that is in sealed glass ampoules. The zeolites H‐ZSM‐5,123–129 H‐SAPO‐5,127, 130 H‐SAPO‐11, 130 H‐SAPO‐34,128, 131–133 H‐Y,127 H‐EMT,127 H‐ZSM‐12,134 H‐ZSM‐23,130 H‐erionite,135 H‐mordenite,127 and H‐offretite,135, 136 as well as montemorillonite,137 and saponite137 have been used as catalysts. Even at reaction temperatures of 373 to 423 K, dehydration of methanol ( δ =50) adsorbed on acidic OH groups to dimethyl ether ( δ =61) occurs.…”

In-situ-IR-, -NMR-, -EPR- und -UV/Vis-Spektroskopie: Wege zu neuen Erkenntnissen in der heterogenen Katalyse

“…Eine große Zahl von 13 C‐MAS‐NMR‐Untersuchungen beschäftigte sich mit der Umsetzung von Methanol zu Kohlenwasserstoffen (MTG: m ethanol‐ t o‐ g asoline, MTO: m ethanol‐ t o‐ o lefins) an aciden Zeolithen unter Satzbedingungen, d. h. in abgeschmolzenen Glasampullen. Als Katalysatoren wurden hierbei die Zeolithe H‐ZSM‐5,123–129 H‐SAPO‐5,127, 130 H‐SAPO‐11,130 H‐SAPO‐34,128, 131–133 H‐Y,127 H‐EMT,127 H‐ZSM‐12,134 H‐ZSM‐23,130 H‐Erionit,135 H‐Mordenit127 und H‐Offretit135, 136 sowie Montmorillonit137 und Saponit137 eingesetzt. Bereits bei Reaktionstemperaturen von 373 bis 423 K findet eine Dehydratisierung von Methanol ( δ =50), adsorbiert an aciden OH‐Gruppen, zu Dimethylether ( δ =61) statt.…”