Structural Analysis of the Methylated Product of Coal (II)

The purpose of this work is to obtain additional information about molecular structure and solubilization of coal.Two reductive methylation products, one Yubari and the other Taiheiyo, were highly soluble in benzene, and contained n-hexane soluble portion (about 25%)These n-hexane soluble portions were fractionated by the preparative GPC procedure into six fractions raccording to their molecular size, respectively.The GPC fractions obtained were examined by nuclear magnetic resonance and infrared spectroscopy.Fraction mean molecular weights and elementary composition were also measured.From the results of the structural analyses of the fractions, average molecular stru-ctures of fractions showed the gradually decreasing tendency of the numbers of condensed rings and the degree of substitution, and then also the shortening tendency of aliphatic side chains with the increase of fraction number.Structural unit weight of these fractions ranged from 124 to 315 for Yubari, and from 121 to 208 for Taiheiyo. These observa-tions were in agreement with results of petroleum ether soluble portion from original Akabi-ra coal.It has been revealed for Akabira coal that structural unit itself of each fraction which had average molecular weight less than 400, formed one molecule, but as for Yubari and Taiheiyo coals, each fraction molecule less than 400 (Fr.no.4 to 6) consisted of appro-ximately dimer of structural unit.Average molecular weights of n-hexane soluble portions prepared from Yubari and Taiheiyo coals by reductive methylation were similar to those of the oils by hydrogenation using red mud catalyst, nevertheless n-hexane soluble portions from Yubari and Taiheiyo coals had smaller structural units and more high polymerization degree than the oils.Moreover differences in chemical structure between two n-hexane soluble portions were discussed.