XPS comparative analysis of coal macerals with different reducibility

Reducibility of coal,like rank and maceral,is one of the main factors influencing the properties of coals.The effect of coal reducibility on structural characteristics of macerals is the basic approach for understanding the difference of coal properties from the molecular viewpoint.XPS(X-ray Photoelectron Spectroscopy)analysis was carried out to determine the forms and difference of carbon,oxygen,nitrogen,sulfur on the surface of vitrinite and inertinite from Pingshuo and Shendong coals with similar coal rank and petrographical compositions but different reducibility.The results show that C—C or C—H,C—O,CO,COO are four forms of carbon,and vitrinite has higher content of C—C or C—H than inertinite.The macerals of Pingshuo coal with stronger reducibility has higher content of C—C or C—H than those of Shendong coal with weaker reducibility.The forms of the other three elements in all samples are similar.The dominant form of oxygen is phenolic hydroxyl oxygen.Shendong coal macerals have higher capability of adsorbing oxygen than Pingshuo coal macerals,which is the reason that Shendong coal has lower ignition point and is easy spontaneously combusted.The dominant forms of nitrogen are pyridinic and pyrrolic type,while the thiophenic type is the main form of sulfur.The results indicate that the reducibility of coal influences the surface structure of vitrinite and inertinite,whose representation is the different content of C—C or C—H.