甲烷/空气扩散火焰中碳烟表面官能团的演变及其对碳烟氧化活性的影响

Evolution of Soot Surface Functional Groups in CH_4/Air Diffusion Flame and Its Impact on Oxidation Reactivity of Soot

基于甲烷/空气扩散火焰燃烧系统(初始温度25,℃,甲烷/空气流速比2∶1)及毛细管取样技术,结合傅里叶变换红外光谱仪(FT-IR)、X射线光电子能谱仪(XPS)和热重分析仪(TGA),研究不同火焰高度碳烟颗粒表面官能团及其氧化活性,并分析了表面官能团对氧化活性的影响.结果表明:随着火焰高度的增加,碳烟颗粒表面脂肪族C—H官能团和含氧官能团(C—OH和C=O)的含量呈先升高后降低的趋势,而其氧化特性温度参数和表观活化能则呈先降低后升高的趋势;碳烟颗粒表面官能团对其氧化活性有着直接的影响,表面官能团含量越多,其氧化活性也就越高;碳烟颗粒表面的脂肪族C—H官能团含量对其氧化活性的影响起着更为主要的作用,而含氧官能团含量则起着相对次要的作用.

This paper studied the surface functional groups and oxidation reactivity of soot in a methane/air diffusion flame at different heights above the burner （HAB） and analyzed the correlations between surface functional groups and the oxidation reactivity of soot. The soot was collected from an in-situ capillary sampling system and analyzed by Fourier transform infrared spectrometer（FT-IR）, X-ray photoelectron spectrometer （XPS） and thermo gravimetric analyzer （TGA）. The results show that the content of both aliphatic C--H and oxygenated surface functional groups increases firstly and then decreases with the increase of HAB. However, the apparent activation energies for the oxidation of soot decrease firstly and then increase with the increase of HAB. Surface functional groups have a definite impact on the oxidation reactivity of soot, and higher content of surface functional groups leads to higher oxidation reactivity of soot. The content of aliphatic C--H functional groups acts as a more important factor in governing the soot oxidation than either of the two oxygenated functional groups.