Investigation of the Elementary Reaction Mechanism of Surface Mediated Formation of PCDD/F from Aromatic Precursors

摘要CTS96-18433 Dellinger这是一项关于多氯二苯并二恶英(PCDD)、多氯二苯并呋喃(PCDF)及其相关化合物(统称为PCDD/F)形成机理的研究。先前的工作HAQ表明，该过程由250-400(C)范围内的飞灰催化。过渡金属，如铁和铜，似乎也催化这些材料的形成。寻找表面介导反应的证据检验了这一过程的假设机制。含有硅酸盐和氧化铝玻璃(飞灰的替代品)、有机前体(氯苯、苯酚和其他芳香族化合物)和氯化剂(氯、氯化氢和过渡金属氯化物)的各种组合的样品都是在特殊的吸附池中使用电阻加热晶片制备的。化学吸附、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、激光诱导荧光光谱(LIF)、显微拉曼光谱和其他仪器和湿化学技术被用来探测反应中间体。根据这些数据，建立了PCDD/F形成的基本化学反应和动力学模型。消除燃烧来源中含有多氯二苯并二恶英和二苯并呋喃(PCDD/F)的排放是最紧迫的环境问题之一。更好地了解多氯二苯并二恶英的来源和形成机理可能导致制定一项战略，通过工艺修改(防止污染)来避免其形成，从而消除对后处理控制措施的需要。

Abstract CTS 96-18433 Dellinger This is a study of the mechanism of formation of polychlorinated dibenzodioxins (PCDD) polychlorinated dibenzofurans (PCDF), and related compounds (collectively PCDD/F). Previous work haq shown the process to be catalyzed by fly ash in the range of 250-400(C. Transition metals such as iron and copper also seem to catalyze the formation of these materials. A search for evidence of surface mediated reactions tests a hypothetical mechanism for the process. Samples containing various combinations of silicate and alumina glasses (surrogates for fly ash), organic precursors (chlorobenzenes, phenol, and other aromatic compounds), and chlorinating agents (chlorine, hydrogen chloride, and transition metal chlorides) are prepared using resistively heated wafers in a special adsorption cell. Chemisorption, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), laser-induced fluorescence spectroscopy (LIF), micro-Raman spectroscopy, and other instrumental and wet chemical techniques are used to probe reaction intermediates. From these data, an elementary chemical reaction and kinetic model for the formation of PCDD/F is developed. Elimination of emissions containing polychlorinated dibenzodioxins and dibenzofurans (PCDD/F) from combustion sources is among the most pressing of environmental issues. An improved understanding of the origin and mechanism of formation of PCDD/F may lead to a strategy to avoid their formation by process modification (pollution prevention), obviating the need for post-process control measures.