HETEROGENEOUS CATALYSIS AND NMR-SPECTROSCOPY OF SPIN 1/2 NUCLEI

After a short review of nuclear magnetic resonance (NMR) studies on solid catalysts and heterogeneous catalytic reactions, various possibilities for a quantitative characterization of the acidity of zeolites and related catalysts by NMR methods are discussed. It is shown that proton magnetic resonance offers a unique method to determine quantitatively both the strength and concentration of Brønsted acid sites by magic angle spinning (MAS) of evacuated samples. Two examples for an application of this novel method are given where the catalytic activity could be related quantitatively to the acidic properties of the catalysts. In contrast, NMR methods fail until now to describe Lewis acidity of catalysts with a comparable success. © 1990.