Characterization of basic guest compounds on solid catalysts by 13C CP/MAS NMR spectroscopy of surface methoxy groups

✍ Scribed by Udo Schenk; Michael Hunger; Jens Weitkamp

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 77 KB
• Volume: 37
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199912)37:13<s75::aid-mrc536>3.0.co;2-a

✦ Synopsis

Silica gel, dealuminated zeolite USY and cesium-exchanged zeolite Y were impregnated with alkali metal hydroxides or acetates followed by calcination. Surface methoxy groups formed upon loading these samples with methyl iodide were applied as 13 C NMR spectroscopic probes to investigate the formation of well dispersed basic guest compounds. The variation of the isotropic 13 C NMR shifts of methoxy groups bound to different guest compounds on silica gel (49.6-48.7 ppm) shows the same tendency as the electronegativities of alkali metal atoms introduced by impregnation. 13 C CP/MAS NMR studies of surface methoxy groups bound to guest compounds on silica gel and zeolites Y revealed an influence of the support on the 13 C chemical shift tensor. The application of this NMR spectroscopic method on cesium-exchanged zeolite Y impregnated with cesium hydroxide allows one to distinguish at least two types of oxidic guest compounds.