有机组分二次离子质谱特征及其裂解机理

摘要

二次离子质谱(SIMS)技术近年来被广泛用于分析煤和油气烃源岩有机组分化学成分和结构特征.在介绍SIMS质谱图解析方法的基础上,分析了有机组分二次离子组成特征；在综合研究有机组分SIMS质谱图特征的基础上,应用化学动力学原理对有机组分SIMS质谱裂解机理进行了探讨.结果表明:有机组分以芳香核为基本结构单元,且含有杂环并带有多种含氧基团和支链；有机组分SIMS质谱裂解由其复杂大分子结构中烷基苯不同化学键的解离能大小决定的；有机质结构中α碳和β碳之间的α—p键和支链碳的C—C键解离能最弱,有机化学结构中的α-β键和支链碳的C—C键容易断裂；与苯环相连支链中,(C6 H5) CH2—C2H5结构中的α-β键和支链碳的C—C键容易断裂而形成(C6H5)CH2-(91)、C2H5-(29)和CH3-(15)等碎片离子,这也是有机组分SIMS质谱图中最主要的碎片离子峰.%Secondary ion mass spectrometry (SIMS) technology is widely used to analyze the chemical composition and structure characteristics of organic compound from coal and petroleum source rocks recently. Analytical method for mass spectrum of SIMS was introduced, and the characteristic of secondary ion composition of organic compound was analyzed; characteristic of mass spectrum of organic compound SIMS was comprehensively studied, and the cracking mechanism was discussed by the means of chemical kinetics principle. The results showed that aromatic nucleus was the basic structural unit of organic compound, which contained heterocycle with various oxygen-containing groups and branched chains; the crack of organic compound SIMS was controlled by the dissociation energy of different chemical bonds in the complex macromolecular structure of organic compound; the dissociation energy of α- β bond of crcarbon and β-carbon and C-C bond of branched-chain carbon were weakest in the structure of organic matter, and α-β bond and C-C bond of branched-chain carbon were easily fractured in the structure of organic chemistry; α-β bond in the structure of (C6H5-C2H5 and C-C bond of branched-chain carbon were easily fractured to form fragment ions including(C6 H5 )CH2+(91), C2H5+(29) and CH3+ (15) in branched chain connected with benzene ring, which were the main peaks of fragment ions in mass spectrum of organic compound SIMS.