| Abstract
| - The reactions of surface functional groups have an important role in controlling conversion of charnitrogen to NOx during coal combustion. This study involved an investigation of the thermal stability andreactions of nitrogen surface functional groups in nanoporous carbons. Four suites of carbons, which wereused as models for coal chars, were prepared with a wide range of nitrogen and oxygen contents and typesof functional groups. The porous structures of the carbons were characterized by gas adsorption methodswhile chemical analysis, X-ray photoelectron spectroscopy, and X-ray near edge structure spectroscopywere used to characterize the surface functional groups. Temperature programmed desorption andtemperature programmed reduction methods were used to study the reactivity of the surface functionalgroups during heat treatment under inert and reducing conditions. Heat treatment studies show that theorder of stability of the functional groups is quaternary nitrogen > pyridinic > pyrrolic > pyridine N-oxide.Pyridine N-oxide surface groups desorb NO and form N2 via surface reactions at low temperature. Pyrrolicand pyridinic functional groups decompose and react with surface species to give NH3, HCN, and N2 asdesorption products, but most pyrrolic groups are preferentially converted to pyridinic and quaternarynitrogen. The main desorption product is N2. Approximately 15−40 wt % of the original nitrogen wasretained in the carbons mainly as quaternary nitrogen after heat treatment to 1673 K. The results arediscussed in terms of decomposition ranges for surface functional groups and reaction mechanisms ofsurface species.
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