Studies of the effects of O-alkylation on the extractability of demineralized and reduced Polish coals

Abstract

Two coals of different rank were modified by selective O-alkylation. The coals, which were demineralized and reduced by potassium in liquid ammonia, were then exhaustively alkylated with alkyl iodide in the presence of either tetrabutylammonium hydroxide or sodium hydroxide. Fourier transform infrared spectra of O-alkylated coals proved that the reaction occurring on oxygen atoms had not been completed though the formation of alkyl ether/esters was confirmed by NMR spectroscopy. Thus, the above alkylation methods appeared ineffective in removing the hydrogen bond network in the high volatile bituminous coal K-I (77.0% C, d.a.f.) and medium volatile bituminous coal K-II (85,7% C, d.a.f.). Instead, alkylation with dimethyl sulfate seems more efficient in destroying the hydrogen bonds and in producing extractable materials from coals.