Acid properties of H-type mordenite studied by solid-state NMR

作者：Hayashi Shigenobu^*; Kojima Natsuko

来源：Microporous and Mesoporous Materials, 2011, 141(1-3): 49-55.

DOI：10.1016/j.micromeso.2009.11.006

• Solid-state NMR
• Acid property
• Trimethylphosphine oxide
• Zeolite
• Mordenite

Acidic properties of H-type mordenite have been studied by solid-state NMR. The framework Si/Al ratios are determined by (29)Si MAS NMR spectra, and the contents of framework Al and Bronsted acid sites are determined. (27)Al MAS NMR spectra show a presence of extra-framework Al as well as "invisible" Al. The (1)H MAS NMR spectra consist of hydrogen-bonded Si-OH, Bronsted acid site, tightly adsorbed water, Al-OH and isolated Si-OH, the amounts of which are evaluated. The average (1)H chemical shifts of Bronsted acid sites without proton exchange are roughly estimated, which are in the following order; HMIO < HMI 5 < HM20. The acid strength of Bronsted acid sites increases with increase in the Si/Al ratio. Trimethylphosphine oxide (TMPO) is adsorbed as a probe molecule from the gas phase to avoid the effect of solvents. A part of the acid sites are sampled by TMPO molecules. The average (31)P chemical shift of chemisorbed TMPO increases with increase in the Si/Al ratio, demonstrating again that the acid strength increases with increase in the Si/Al ratio.

• 出版日期2011-5