热老化温度对碳烟氧化活性的影响

Effect of Thermal Aging Temperature on Soot Oxidation Activity

由于炽热尾气长时间冲击,柴油机微粒捕集器(DPF)中的沉积碳烟颗粒会发生热老化.本文通过改变惰性气氛下的温度,研究热老化对柴油机碳烟颗粒微观物理化学特性和氧化活性的作用规律.结果表明,随热老化温度的升高,氧化反应特征温度和表观活化能表征的碳烟颗粒氧化活性逐渐降低;氧化活性的降低来源于碳烟颗粒物理化学特性的改变,即微晶尺寸增大,微晶曲率和层间距减小,以A_(D1)/A_G值表征的石墨化程度提高,而以I_(C—H)/I_(C=C)峰高比表征的脂肪族C—H表面官能团相对含量降低.此外,柴油机碳烟颗粒微观结构、表面C—H官能团相对含量与碳烟氧化活性具有良好的相关性,其中微晶曲率对氧化活性影响最大.

The thermal aging of soot particles will occur after the soot particles deposited on the diesel particulate filter suffer a long-term impact of incandescent exhaust.In this paper,the effect of thermal aging on the physicochemical properties and oxidation activity of diesel soot particles was studied under inert atmosphere and different temperatures.Experimental results showed a gradual decrease in soot oxidation activity characterized by oxidation reaction characteristic temperature and apparent activation energy with the increase of the thermal aging temperature.Such a decreased oxidation activity was caused by the variation of physicochemical properties of soot particles,that is,with the increasing thermal aging temperature,the fringe length of soot microcrystals and the degree of graphitization characterized by AD1/AG increased,and the tortuosity and separation distance of soot microcrystals decreased.At the same time,the relative content of aliphatic C—H functional groups characterized by IC—H/IC=C ratio decreased.In addition,the nanostructure parameters of soot particles and the relative content of C—H functional groups had a good correlation with oxidation activity,among which tortuosity showed the greatest impact on oxidation activity.