EVOLUTION OF NITROGEN FUNCTIONALITIES IN CARBONACEOUS MATERIALS DURING PYROLYSIS
EVOLUTION OF NITROGEN FUNCTIONALITIES IN CARBONACEOUS MATERIALS DURING PYROLYSIS
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DOI：
10.1016/0008-6223(95)00154-6
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发表时间：
1995-01-01
期刊：
影响因子：
10.9
通讯作者：
THOMAS, KM
中科院分区：
文献类型：
--
作者：
PELS, JR;KAPTEIJN, F;THOMAS, KM
用X-射线光电子能谱(XPS)研究了褐煤及其模型化合物吖啶、咔唑和聚丙烯腈(PAN)焦炭中氮官能团的去向。在XPS图谱中发现了四个不同的峰，对应于至少五种不同的氮功能形式，都是芳香族部分。为了鉴定目的，记录了合成焦的XPS图谱。氮官能团的分布随热解条件的加重而变化。在温和的热解条件下，在碳基质的缩合过程中，吡啶-N的不稳定官能团，如吡啶酮、质子化的吡啶-N和N-氧化物，首先转化为吡啶-N，其次，吡咯-N转化为吡啶-N。在缩合过程中，氮原子取代碳原子并入石墨烯层中。经过严重的热解后，所有的氮最终以吡啶氮的形式存在于石墨烯层边缘的六元环中，或在石墨烯内部以四元氮的形式存在。当暴露在环境中时，可以形成吡啶-N的N-氧化物。在热解过程中，焦炭前体的氮素分布的差异已经缩小。据推测，焦炭中氮分布的剩余微小差异不会显著影响焦炭燃烧过程中氮氧化物的形成。
X-ray photoelectron spectroscopy (XPS) was used to investigate the fate of nitrogen functional forms present in a lignite and its chars, chars derived from the model compounds acridine, carbazole and polyacrylonitrile (PAN). Four different peaks have been found in the XPS patterns, corresponding to at least five different nitrogen functional forms, all being aromatic moieties. The XPS patterns of the synthetic chars were recorded for identification purposes. The distribution of nitrogen functional forms changes with increasing severity of the pyrolysis conditions. Under mild pyrolysis conditions, firstly unstable functionalities like pyridones, protonated pyridinic-N and N-oxides of pyridinic-N are converted to pyridinic-N and secondly pyrrolic-N is converted to pyridinic-N during condensation of the carbon matrix. During the condensation process, nitrogen atoms are incorporated in the graphene layers replacing carbon atoms. After severe pyrolysis all nitrogen is eventually present in 6-membered rings located at the edges of the graphene layers as pyridinic-N or in the interior as quaternary-N. Upon exposure to the ambient, N-oxides of pyridinic-N can be formed. During pyrolysis, differences in nitrogen distribution of the char precursors have diminished. It is presumed that the remaining small differences in the nitrogen distribution of the chars cannot significantly influence the formation of nitrogen oxides during combustion of the chars.