柴油机排气碳烟催化氧化动力学分析

Kinetic Analysis of Catalytic Oxidation of Diesel Engine Exhaust Soot

基于热重实验系统开展了柴油机排气碳烟在O_(2)气氛下的催化氧化实验,通过Friedman-Reich-Levi(FRL)法、Flynn-Wall-Ozawa(FWO)法、Kissinger-Akahira-Sunose(KAS)法对碳烟催化氧化反应的动力学参数进行计算,并根据线性相关系数R 2挑选出最优计算方法.利用Malek法推断出碳烟催化氧化的最概然反应机理,再通过优化参数法拟合出可近似体现真实反应机理的函数表达式.分析结果表明:相同的实验条件下,Pt催化剂的加入使碳烟氧化速率增加,特征温度降低,碳烟的氧化机理发生了明显的变化.3种方法计算的平均活化能存在以下关系:FRL法>FWO法>KAS法.通过对比R 2可知,FRL法计算的活化能更为准确.碳烟在O_(2)气氛中被Pt催化氧化机理最接近Mampel Power法则中的相边界反应R3机理,通过优化参数法拟合出的机理函数为:f(α)=(1−α)^(0.931)α^(−0.401).

The thermogravimetric experimental system was used to carry out the catalytic oxidation experiment of diesel exhaust soot in O_(2).The kinetic parameters of soot catalytic oxidation reaction were calculated using the Friedman-Reich-Levi(FRL),Flynn-Wall-Ozawa(FWO),and Kissinger-Akahira-Sunose(KAS)methods,and the optimal calculation method was selected according to the linear correlation coefficient R 2.At the same time,the Malek method was used to infer the most probable reaction mechanism for the catalytic oxidation of soot.The mechanism function close to the real reaction was fitted by optimizing the parameters.The analysis results show that under the same experimental conditions,the addition of Pt catalyst increased the soot oxidation rate,reduced the characteristic temperature,and changed the soot oxidation mechanism significantly.In addition,the average activation energy calculated by the three methods has the following relationship:FRL>FWO>KAS.By comparing R 2,the activation energy calculated by the FRL method is more accurate.The mechanism of soot catalytic oxidation by Pt in O_(2) is the closest to the phase boundary reaction R3 mechanism in the Mampel Power law,and the mechanism function fitted by optimizing parameters is f(α)=(1-α)^(0.931)α^(-0.401).