FT-IR investigation of the structural changes of Sulcis and South Africa coals under progressive heating in vacuum

Two samples of coals coming from South Africa and Sulcis (Sardinia, Italy) were subjected to progressive heating up to 800°C in vacuum. The infrared (IR) spectra of the residuals obtained at 100°C intervals from room temperature to 800°C show spectral changes ascribed to transformations at the level of the organic and inorganic components. Comparing these results with those previously obtained by heating the same coals in the presence of air and examining their pyridinic extracts, it appears that the Sulcis coal with respect to the other coals contains a lower amount of clay-minerals. Furthermore, the IR analysis shows that this coal is nearer to being a lignite than a hard-coal.