Chemical characterization of coal. 3. Qualitative and quantitative aspects of the reductive methylation of coal

• Published in: Fuel (Guildford) 1982-01, Vol.61 (5), p.423-429
• Main Authors: Niemann, Klaus, Richter, Udo-Burckhard
• Format: Article
• Language: English
• Subjects: chemical analysis and testing; chemical structure; coal
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(82)90065-5

The treatment of coal with solvated electrons (formed as a blue solution by treating potassium with the dimethyl ether of ethyleneglycol) followed by solvolysis of the polyanionic coal with dimethylsulphate allows coal derivatives to be prepared, 85 wt% (daf) of which can be extracted with pyridine. Detailed investigations of these products, and of analogous deuterium-labelled derivatives, show that an average of 7 methyl groups per 100 C atoms have been introduced in a single treatment. This value can be increased by a second treatment, l.r. structure-element analysis shows, in addition, that 35% of the hydrogen so introduced forms hydroaromatic species and takes part in the degradation of aromatic structures. The site of the reaction is studied by comparing the results from the deuteromethylation of coal and of model compounds: it is suggested that the marked increase in extractability results from the cleavage of aliphatic bridges of the type ArCH 2CH 2Ar' giving ethyl-substituted aromatics and related products. A method is described which determines increments from quantitative i.r. measurements for model compounds and allows a rapid determination of the Cl 3-content of a deuterated coal.