X-ray Photoelectron Spectroscopy (XPS) Investigation of Nitrogen Functionalities during Coal Char Combustion in O₂/CO₂ and O₂/Ar Atmospheres

Abstract

The development of nitrogen functionalities during Datong bituminous coal pyrolysis under severe conditions was investigated by X-ray photoelectron spectroscopy (XPS). The evolutions of the nitrogen functionalities in char as a function of burnoff during high-temperature char (1173 K) combustion in O2/CO2 and O2/Ar atmospheres were also studied. Pyrrolic nitrogen is completely converted into quaternary and pyridinic nitrogen upon severe pyrolysis (1173 K for 2 h). More severe pyrolysis (1473 K for 2 h) results in a conversion of quaternary nitrogen into pyridinic nitrogen. During char combustion, quaternary nitrogen is transformed into pyridone and pyridinic nitrogen in both of the atmospheres. The CO2 gasification has a small effect on the evolution of nitrogen functionalities but has a significant influence on the char combustion rate. The char combustion rate is faster in an O2/CO2 atmosphere than in an O2/Ar atmosphere.