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

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.

Graphical Abstract

KEYWORDS:

• Nitrogenous gas formation
• N-containing functional groups
• O-containing functional groups
• coal pyrolysis
• superfine pulverized coal

Disclosure statement

No potential conflict of interest was reported by the authors.