Evaluation of Zeolite Acidity by ³¹P MAS NMR Spectroscopy of Adsorbed Phosphine Oxides: Quantitative or Not?

ABSTRACT: ³¹P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy of adsorbed alkyl-substituted phosphine oxides has witnessed tremendous progress during the last years and has become one of the most informative and sensitive methods of zeolite acidity investigation. However, quantitative evaluation of the number of sites is still a challenge. This study clarifies the main origin of errors occurring during NMR experiments, introduces the appropriate standards (both internal and external), and determines the relaxation parameters and the conditions for the acquisition and integration of spectra. As a result, a methodology for the quantitative measurement of the content of Brønsted and Lewis sites and the amount of internal and external silanol groups is established. The

SUBMITTER: Zasukhin DS 

PROVIDER: S-EPMC9016808 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature