煤粉再燃中煤焦异相还原NO机理的量化研究  

A Quantum Chemistry Study of Heterogeneous Reduction Mechanisms of NO on the Surface of Char During Pulverized Coal Reburning

作　　者：张秀霞[1] 周志军[1] 周俊虎[1] 刘建忠[1] 岑可法[1] 

机构地区：[1]浙江大学能源清洁利用国家重点实验室,杭州310027

出　　处：《燃烧科学与技术》2011年第2期155-159,共5页Journal of Combustion Science and Technology

基　　金：国家高技术研究发展计划(863计划)资助项目(2008AA05Z304)

摘　　要：采用armchair结构的焦炭模型,对焦炭异相还原NO的机理进行了分子水平上的模拟研究.在B3LYP/3-21G*计算水平上优化得到各反应路径上的反应物、产物、中间体和过渡态的几何构型.在B3LYP/6-31G(d)水平上计算优化所得结构的单点能.计算得到两个不同的反应路径,分别对应已提出的两个异相还原反应机理.NO分子与预先吸附在焦炭表面的碳氮组分C(N)结合释放出N2的反应路径中最大能垒为128.8,kJ/mol;两个表面碳氮组分结合释放出N2的反应路径中需翻越的最大势垒为141.1,kJ/mol.NO在焦炭表面异相还原生成N2的反应为放热反应.采用经典过渡态理论计算得到各中间反应的反应速率常数,在典型再燃温度1,473,K时,路径1的反应速率决定步的速率常数为6.12×109,路径2的反应速率决定步的反应速率常数为1.50×1011.Density functional theory calculations were carried out to investigate heterogeneous reduction mechanisms of NO on the surface of char by using a simplified char model with armchair configuration.Both intermediate stable species and transition state geometries were optimized at B3LYP/3-21G＊ calculation level,and their single-point energies were calculated at B3LYP/6-31G（d）level.Two different reaction pathways were obtained for heterogeneous reactions between NO molecules and char model with armchair configuration,which corresponded to the two differ-ent mechanisms proposed.The highest energy barriers were 128.8,kJ/mol for the reaction of surface nitrogen species with one NO molecule,and 141.1,kJ/mol for the recombination of two surface nitrogen species.The overall reactions are exothermic reactions,which are in agreement with the experiment results.Rate constants for intermediate reac-tions were calculated by transition state theory and fitted to 2-parameter Arrhenius expressions.The rate constants of rate-determining steps for pathway 1 and pathway 2 are 6.12×109 and 1.50×1011 at 1 473 K respectively.

关 键 词：焦炭 NO 异相还原 密度泛函理论 

分 类 号：TQ534.9[化学工程—煤化学工程]