Abstract
High resolution two-dimensional 27Al multiple-quantum magic-angle-spinning (MQMAS) NMR being capable of averaging the second-order quadrupolar interaction was applied in order to characterize the mineral matter in dry coals that have been spotlighted recently in new approach to the coal use. Octahedral aluminum compounds between kaolin and other mineral phases could be clearly distinguished by 27Al MQMAS method. According as the total carbon percent increases, octahedral aluminum species tend to vary from kaolin. The 1H→27Al CP/MQMAS NMR that is a combination of cross polarization and MQMAS was also employed to evaluate the connectivity between aluminum atom and hydrogen atom. As a result, the octahedral compounds containing the linkage of Al-O-H such as kaolin and excluding the Al-O-H bond were separated by this technique. MQMAS and CP/MQMAS is very effective in characterization of inorganic matter including quadrupolar nuclei, which is particularly well suited to the analysis of clay minerals that are noncrystalline materials and present in coals although XRD is difficult to analyze the amorphous compounds.
