A study on vitrinite and inertinite interaction in pyrolysis of 3 coals

Coals are composed of macerals, mainly vitrinite (V) and inertinite (I). V and I were reported interacting with each other in pyrolysis in some studies but not interacting with each other in other studies. This paper studies the interaction of V and I in pyrolysis on a thermal gravimetric analyzer coupled online with a mass spectrometer (TG-MS) using blends of V and I prepared from 3 coals. The extent of V and I interaction is discussed based on the differences in characteristic parameters of TG-MS data and the radical concentration of chars determined by electron spin resonance (ESR), and elaborated briefly by the carbon type distribution of the macerals characterized by 13C NMR. The interaction is quantified by the mass loss and its peak depth, and H2O release below 600 °C, as well as by the radical concentration of chars. It is found that the V and I of coals with relatively higher carbon contents do not show significant interaction while those of a coal with a lower carbon content shows significant interaction. The V and I interaction occur mainly in the temperature range of 400−600 °C where the major of devolatilization takes place. The V and I interaction can be related to the difference in carbon distribution between V and I of a coal, and the large is the difference, the large is the interaction. The interaction is attributed to the higher contents of methyl, oxy-methine and, ortho-oxyaromatic protonated carbons in V than in I.