【作者】 洪新；

【导师】 齐飞；

【作者基本信息】 中国科学技术大学 ， 同步辐射及应用， 2009， 博士

【摘要】 本论文利用同步辐射真空紫外单光子电离、分子束取样和反射式飞行时间质谱相结合的技术研究了含氮杂环模型化合物的热解,包括五元环含氮体系（吡咯）、六元环含氮体系（吡啶）和替代的六元环含氮体系（4-甲基吡啶）。本论文共分为五章,主要集中于不同含氮体系热解的产物、中间体及自由基的定性和定量分析;并结合G3B3理论计算讨论了不同含氮体系中碳氢和碳氮主要产物的生成路径。第一章首先简述了日益增长的能源应用尤其是广泛的基础能源煤及煤系燃料应用对污染治理的需求,指出了含氮模型化合物的惰性环境下的热解对煤及煤系燃料燃烧的初步的富燃过程的模拟及对可控燃烧过程机理的理解具有现实意义;接着简介了NO_x及形成机理,引出了煤燃料中N元素的存在形态及其转化形式;最后,介绍了热解基本概念如原理、方式、影响因素及分析方法等。与其它的热解诊断方法相比较,分子束质谱结合可调谐的真空紫外光电离技术有更多的优点,这包括:高的信噪比、软电离以及在很宽的范围内连续可调的光子能量。这些优点将有利于热解反应中各物种的鉴定和浓度测量。第二章主要介绍了热解研究所用的实验装置。首先介绍了同步辐射基本概念及优点和特点,国家同步辐射实验室储存环和U10、U14C光束线的结构性能和相关参数,并介绍了U14C光束线新增加的气体滤波器;描述了实验站的工作原理和实验程序;文中还简单介绍热解研究中用到的一些理论计算方法;最后,介绍了热解实验数据的获得及处理方法。第三章研究了低压条件下的五元杂环吡咯模型化合物的热解反应:（1）通过测量和分析热解产物的光电离质谱及光电离效率谱,鉴别了稳定的产物及不稳定的中间产物和自由基,区分了同分异构体和同质异构体。其中主要产物为H₂,C₂H₂,HCN,p-C₃H₄,C₂H₃N,自由基如C₄H₄N,C₂H₂N也同时被探测和鉴别;（2）通过近阈值电离并推导出物种随温度变化的摩尔分数曲线,更详细地定性和定量地描述了产物随温度的变化。（3）用G3B3方法对吡咯的消耗及主要产物的生成路径进行了理论计算,结合实验数据,给出了主要产物的生成路径及反应机理。第四章研究了了低压条件下的六元杂环吡啶模型化合物的热解反应:通过测量和分析热解产物的光电离质谱及光电离效率谱,确定了热解产物的具体结构,推导出了它们的摩尔分数曲线。主要产物为H₂,C₂H₂,C₄H₂,C₃H₃N和C₅H₃N,其中HCN为非低温时的主要热解产物;结合G3B3方法对吡啶的消耗及主要产物的生成路径进行了理论计算,结合实验数据,给出了主要产物的生成路径及反应机理。与吡咯热解初期的形成的复杂异构体不同的是,吡啶热解的主要产物前驱体相对单一,热解产物为母体脱氢的吡啶自由基、母体脱氢开环链状自由基和母体直接开环的产物。与吡咯模型化合物及其它芳香化合物不同的是,吡啶的热解产物相对较少而且不容易形成多环芳香化合物,难以形成炭黑,这与吡啶的结构有关。最后第五章研究了取代的六元含氮模型化合物4-甲基吡啶的热解,结合前章吡啶热解反应路径的研究,从产物的分布得出一些普适的定性结论。主要产物为H₂,C₂H₂,C₄H₂,C₃H₃N和HCN,其中HCN为非低温时的热解产物;通过近阈值电离并导出物种随温度变化的摩尔分数曲线,更详细地定量地描述了产物随温度的变化。4-甲基吡啶热解主要从母体脱甲基和脱氢两个初始反应出发,一种趋势是形成大质量数的苯并或杂环的多环化合物,有助于了解炭黑形成过程中的复杂化学过程;另一趋势是开环生成小的碳氢和腈类物质,实验得出的含氮物质的种类及随温度变化有助于了解NO_x的前驱物质的形成及其变化规律。更多还原

【Abstract】 This dissertation is dedicated to investigate the pyrolysis of the fuel-bonded nitrogen（FBN） model compounds,including five（six）-membered ring nitrogen model compound pyrrole（pyridine） and the substituted six-membered ring nitrogen compound 4-methyl pyridine,with vacuum ultraviolet single-photon ionization combined with molecular beam mass spectrometry technique.This dissertation consists of five chapters.It mainly focuses on the identification and quantification of the pyrolysis products,intermediates and isomers.The consumption reactions and the decomposition channels of nitrogen containing model compounds are calculated by Gaussian-3（G3） method.In Chapter 1,the importance of the pollutant controlling to the widely employed basic energy source especially for coal and coal derived liquid fuel are briefly introduced.And the realistic signification of the inert pyrolysis investigation of the nitrogen containing model compounds to the modeling of the initial rich fuel combustion process has been pointed out.The formation mechanisms of the NO_X and the existing N element together with their conversion are reviewed.Some basic concepts related to pyrolysis are briefly introduced.The powerful combination of molecular beam mass spectrometry（MBMS） with photoionization by tunable VUV synchrotron offers significant improvements over some other pyrolysis diagnostics, including superior signal-to-noise,soft ionization,and tunability in a wide range. These advantages make threshold ionization possible,which can be used to identify isomers and detect active intermediates such as free radicals.In Chapter 2,the pyrolysis experiment equipment is introduced in detail, including the parameters of storage ring of National Synchrotron Radiation Laboratory（NSRL） and the structures of U10 and U14C beamlines.The description of the endstation combined with the principles of molecular beam and reflectron mass spectrometry are presented.A detailed description of the data dealing processes is exhibited.In Chapter 3,the pyrolysis study of pyrrole at low pressure is presented in detail. Major products observed from pyrrole pyrolysis,including H₂,C₂H₂,HCN,p-C₃H₄, C₂H₃N,especially the radical C₄H₄N,C₂H₂N are identified unambiguously by measurements of photoionization efficiency spectra.Mole fraction profiles of these pyrolysis species are measured at the selective photon energies near ionization thresholds.The lowest dissociation channels and consumption reactions of the major products of pyrrole are calculated by Gaussian-3（G3） method.The experimental results are in good agreement with theoretical predictions.In Chapter 4,pyrolysis of six-membered pyridine model compound has been studied.In general,the major products of the pyrolysis of pyridine have been identified by the measurements of photoionization efficiency spectra and the main production pathways have been proposed with respect to the Gaussian-3（G3） method calculation.Different from the primary pyrolysis procedure of pyrrole with the complex tautomers the initial precursors of the major pyrolysis products are simple and the corresponding pathways are more distinct.The pyrolysis is mainly initiated from the hydrogen abstract radicals of pyrrole,the linear radicals from the hydrogen abstract of pyrrole and the direct ring open products.It is worthy of noting that different from the pyrolysis of pyrrole and other aroma compounds the products of pyridine pyrolysis is relatively less in number and has low tendency of sooting.In Chapter 5,the pyrolysis of substituted six-membered ring model compound 4-methyl pyridine has been investigated.Instead of detail theoretical analysis of the reaction mechanism,the general results have been proposed from the products distribution and the combination of the pyrolysis investigation of its analogous pyridine.The major products are H₂,C₂H₂,C₄H₂,C₃H₃N and HCN,here HCN is not a primary initial product at low extent of decomposition.The mole fraction profiles of products have been obtained from the near threshold ionization.The pyrolysis of 4-methyl pyridine is initiated from the methyl abstraction and hydrogen abstraction procedures which are associated with the understanding of the soot formation and the NOX precursor correspondingly.更多还原