Nitrogenous gas formation mechanisms of chemically modified superfine pulverized coal during pyrolysis

Abstract

ABSTRACT The pyrolysis products are affected by the O-containing groups in coal. The influences of the introduced O-containing groups on nitrogenous gas formation are rarely explored. To investigate this issue, superfine pulverized coal samples were modified by several kinds of selected chemical reagents. 13C nuclear magnetic resonance spectroscopy (NMR) experiments demonstrate that a considerable amount of carboxyl, hydroxyl structures is introduced into the carbon skeleton after peracetic acid modifications. X-ray photoelectron spectroscopy (XPS) experiments reveal that the content of quaternary nitrogen N-Q on the surface of the samples modified by peracetic acid remain unchanged in general. And oxidized nitrogen N-X structures are formed by the oxidation of pyridinic nitrogen N-6 and pyrrolic nitrogen N-5, which induces the proportion of N-X to increase more than 40%. Because of the introduction of O-containing functional groups, the discrepancy of nitrogenous gas composition has been found between the raw and modified samples during pyrolysis. The production of N2O soars between 200°C and 300°C. After H2O2 modifications, the formation paths of nitrogenous gas do not change significantly due to the absence of O-containing group introduction. This research uncovers that the introduced O-containing groups alter the formation paths of nitrogenous gas in coal during pyrolysis and elucidates the mechanism.