Experimental characterization and molecular simulation of nitrogen complexes formed upon NO–char reaction at 270 °C in the presence of H2O and O2 Original Research Article

Surface nitrogen complexes formation upon reaction of coal char with NO at 270 °C in the presence or absence of O2 and/or H2O was studied by XPS. Complexes such as pyrrolic-N type, pyridine-N-oxide, pyridinic-N and –NO2 were observed. The major increment was in pyridinic-N. Water had a partial inhibition effect while oxygen promotes the formation of the nitrogen complexes probably due to char gasification. The gasification level in mixtures with O2 varied according to the presence or not of H2O. TPD was used to quantify reversible NO adsorption and oxygen surface groups formed on the char during reaction. Molecular modeling was applied to determine the thermodynamics of the reactions. Mechanisms are proposed to explain the formation of pyridinic and –NO2 complexes at low temperatures.