Acidity Characterization of Solid Acid Catalysts by Solid-State 31P NMR of Adsorbed Phosphorus-Containing Probe Molecules

Recent developments on acidity characterization of solid acid catalysts, specifically those invoking P-31 solid-state nuclear magnetic resonance (SSNMR) spectroscopy using phosphorus-containing molecules as probes, have been summarized. In particular, various P-31 SSNMR approaches using trimethylphosphine, diphosphines, and trialkylphosphine oxides (R3PO) will be introduced, and their practical applications for the characterization of important qualitative and quantitative features, namely, type, distribution, accessibility (location/proximity), concentration (amount), and strength of acid sites in various solid acids, will be illustrated.