The Study of Aluminosilicate and Related Catalysts by High-Resolution Solid-State NMR Spectroscopy

Abstract

Publisher Summary This chapter reviews the study of aluminosilicate and related catalysts by high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. NMR spectra cannot normally be measured in solids in the same way in which they are routinely obtained from liquids and solutions. However, certain solids have sufficient molecular motion for NMR spectra. The electrons modify the magnetic field experienced by the nucleus. Chemical shift is caused by simultaneous interactions of a nucleus with surrounding electrons and of the electrons with the static magnetic field B 0 . The latter induces, via electronic polarization and circulation, a secondary local magnetic field that opposes B 0 and therefore shields the nucleus under observation. Zeolites are a class of framework silicates built from corner-sharing SiO 4− 4 and AlO 5− 4 tetrahedra and containing regular systems of intracrystalline cavities and channels of molecular dimensions. The full range of 29 Si chemical shifts is over 500 ppm wide. High-resolution 29 Si NMR has been extensively used in solution, enabling the structure of the various silicate anions present in alkali metal silicates, tetraalkylammonium silicates, and solutions of silicic acids to be established.