Reactions of nitrogen and oxygen surface groups in nanoporous carbons under inert and reducing atmospheres.
Reactions of nitrogen and oxygen surface groups in nanoporous carbons under inert and reducing atmospheres.
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DOI：
10.1021/la0472495
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发表时间：
2005-04
期刊：
影响因子：
--
通讯作者：
B. Xiao;J. Boudou;Mark Thomas
中科院分区：
文献类型：
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作者：
B. Xiao;J. Boudou;Mark Thomas
煤表面官能团的反应在控制煤焦氮向NOx转化过程中具有重要作用。本研究主要探讨奈米多孔碳材料表面含氮功能团的热稳定性与反应。制备了四组用作煤焦模型的碳，它们具有广泛的氮和氧含量以及官能团类型。通过气体吸附法表征了炭的多孔结构，同时采用化学分析、X射线光电子能谱和X射线近边结构谱表征了炭表面官能团。程序升温脱附和程序升温还原方法被用来研究在惰性和还原条件下的热处理过程中的表面官能团的反应性。热处理研究表明，各官能团的稳定性顺序为：季氮>吡啶>吡咯>吡啶N-氧化物。吡啶N-氧化物表面基团在低温下通过表面反应脱附NO并形成N2。吡咯和吡啶官能团分解并与表面物种反应，得到NH3，HCN和N2作为解吸产物，但大多数吡咯基团优先转化为吡啶和季氮。主要解吸产物为N2。在热处理至1673 K后，约15-40重量%的原始氮主要作为季氮保留在碳中。讨论了表面官能团的分解范围和表面物种的反应机理。
The reactions of surface functional groups have an important role in controlling conversion of char nitrogen to NOx during coal combustion. This study involved an investigation of the thermal stability and reactions of nitrogen surface functional groups in nanoporous carbons. Four suites of carbons, which were used as models for coal chars, were prepared with a wide range of nitrogen and oxygen contents and types of functional groups. The porous structures of the carbons were characterized by gas adsorption methods while chemical analysis, X-ray photoelectron spectroscopy, and X-ray near edge structure spectroscopy were used to characterize the surface functional groups. Temperature programmed desorption and temperature programmed reduction methods were used to study the reactivity of the surface functional groups during heat treatment under inert and reducing conditions. Heat treatment studies show that the order 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. Pyrrolic and pyridinic functional groups decompose and react with surface species to give NH3, HCN, and N2 as desorption products, but most pyrrolic groups are preferentially converted to pyridinic and quaternary nitrogen. The main desorption product is N2. Approximately 15-40 wt % of the original nitrogen was retained in the carbons mainly as quaternary nitrogen after heat treatment to 1673 K. The results are discussed in terms of decomposition ranges for surface functional groups and reaction mechanisms of surface species.