Reactivity and structural modification of coals in HNO3–Ac2O system

The interaction of different rank coals with equimolar HNO3–Ac2O mixture has been studied. This process, proceeding fast at 15–30 °C for several hours, results in changes of spatial and chemical structures because of nitration of coal arenes, formation of oxygen functional groups and partial cleavage of C–C cross-links. As a result, structurally modified coals (SMCs) are obtained as new coal-derived substances. Properties of SMCs were investigated by X-ray diffraction method, DRIFT spectroscopy and thermogravimetry. The main reactions responsible for structural modification have been proposed.