Solid State 13C NMR in Coal Research: Selected Techniques and Application

Abstract

Developments in solid-state 13C NMR techniques and their applications in coal research are reviewed. These techniques include cross polarization and magic-angle spinning with high-power decoupling, dipolar dephasing, sideband suppression at high magnetic fields, dynamic nuclear polarization and combined rotation and multiple pulse spectroscopy. The quantitative reliability of 13C NMR aromaticity measurements is also discussed. Results from recent studies indicate that not all the carbons in coal are observed in the solid-state 13C NMR measurements. Thus, the question of the quantitative reliability of 13C NMR in coal research remains unresolved. Selected applications of solid-state 13C NMR for the study of pyrolysis and hydroliquefaction of coals are presented. Results of these studies indicate that solid-state 13C NMR can provide valuable information about aromaticity changes that occur during coal processing.