Theoretical study of the effect of hydrogen radicals on the formation of HCN from pyrrole pyrolysis
Theoretical study of the effect of hydrogen radicals on the formation of HCN from pyrrole pyrolysis
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氢自由基对吡咯热解生成HCN影响的理论研究
DOI：
10.1016/j.joei.2018.08.004
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发表时间：
2019-10-01
影响因子：
5.7
通讯作者：
Yang, Yong-ping
中科院分区：
文献类型：
--
作者：
Liu, Ji;Zhang, Xiaolei;Yang, Yong-ping
作为一种典型的化石燃料，煤是氮氧化物(NOx)污染的主要贡献者。煤热解生成NOx的详细机理尚需阐明。在本研究中，我们使用密度泛函理论(DFT)研究了在氢(H)自由基存在的情况下，吡咯热解过程中作为NOx前体的HCN的形成机理。首先，比较了氢自由基攻击的三种不同反应位置。结果表明，氢自由基与吡咯在N邻位的反应只需一步反应，活化能为77.12kJ/mol。此外，为了考察氢自由基在吡咯热解生成HCN中的作用，从理论上研究了12条后续反应路径。研究发现，在所有已报道的反应机理中，氢转移和碳-碳裂解反应的途径之一(a-4途径)是能量垒最低的途径，因此它在煤的吡咯组分生成HCN的过程中起着重要作用。这些结果进一步表明，氢自由基显著降低了吡咯热解的能垒。(C)2018年能源研究所。爱思唯尔有限公司出版。保留所有权利。
As a typical fossil fuel, coal is a major contributor to nitrogen oxide (NOx) pollution. The detailed mechanism of NOx generation from coal pyrolysis need to be clarified. Within this research, we used density functional theory (DFT) to investigate the formation mechanism of HCN as a NOx precursor during pyrolysis of pyrrole in the presence of hydrogen (H) radicals. Firstly, three different reaction positions for hydrogen radical attacking were compared. It was identified that hydrogen radical initially reacts with pyrrole at the location adjacent to N through a single elementary reaction step with an activation energy of 77.12 kJ/mol. Additionally, to examine the role of hydrogen radical in the pyrrole pyrolysis to form HCN, 12 subsequent reaction pathways were theoretically investigated. It was found that one of the pathway (Pathway a-4) involving hydrogen transfer followed by carbon-carbon cleavage processes is the route with the lowest energy barrier of all of the mechanisms reported, thus it plays an important role in the formation of HCN from the pyrrolic components of coal. These results further indicated that the hydrogen radicals significantly reduce the energy barrier of the pyrrole pyrolysis. (C) 2018 Energy Institute. Published by Elsevier Ltd. All rights reserved.