Heterogeneous reduction of nitric oxide on synthetic coal chars

Model compounds, with a controlled heteroatoms content and well-defined functionalities, were used to study the release of nitrogen compounds from char combustion. In the present work, the mechanisms involved in NO-char heterogeneous reduction were studied with a synthetic coal (SC) char as carbon source. Another synthetic char (SN) without any nitrogen in its composition was also employed in these studies. Temperature programmed reduction (TPR) tests with a gas mixture of 400 ppm NO in argon and with isotopically labelled nitric oxide, 15NO (500 ppm 15NO in argon), were carried out. The gases produced were quantitatively determined by means of MS and FTIR analysers.Under the conditions of this work the main products of the NO-C reaction were found to be N2 and CO2. The main path of reaction involves the formation of surface nitrogen compounds that afterwards react with nitrogen from the reactive gas to form N2. It was observed that fuel-N also participates in the overall heterogeneous reduction reaction, although to a lesser extent.