Acid property of MFI-type zeolites probed by trimethylphosphine oxide studied by solid-state NMR
| Autor: | Keiko Jimura, Shigenobu Hayashi, Natsuko Kojima |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
chemistry.chemical_classification
Chemistry Chemical shift Inorganic chemistry General Chemistry Condensed Matter Physics Spectral line Acid strength Adsorption Solid-state nuclear magnetic resonance Mechanics of Materials Molecule Physical chemistry General Materials Science Brønsted–Lowry acid–base theory Zeolite |
| Zdroj: | Microporous and Mesoporous Materials. 186:101-105 |
| ISSN: | 1387-1811 |
| DOI: | 10.1016/j.micromeso.2013.11.047 |
| Popis: | Acid properties of ZSM-5 type zeolite are studied by solid-state NMR using trimethylphosphine oxide (TMPO) as a probe molecule. TMPO is introduced from the gas phase at 373 K. The amounts of the loaded TMPO are quantified by the signal intensities of 1 H MAS NMR spectra, which are compared with the numbers of Bronsted acid sites estimated by the Si/A ratio of the framework derived from 29 Si MAS NMR spectra and the content of fourfold-coordinated Al from 27 Al MAS NMR spectra. The use of 373 K for loading the probe molecules increases the loading level of TMPO, and thus almost all the acid sites are probed. The 31 P chemical shifts in the range between 90 and 60 ppm are attributed to TMPO adsorbed on Bronsted acid sites, whereas the signals between 60 and 40 ppm are ascribed to TMPO adsorbed on other sites than Bronsted acid sites. The 13 C chemical shift of methyl groups in the adsorbed TMPO depends mainly on the confined space as well as on the acid strength. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect