老化态Pd/Rh基三元催化器的起燃及次生污染物生成特性研究

Study on the characteristics of ignition and secondary pollutants generation of aged Pd/Rh three-way catalytic converter

为探究天然气发动机三元催化器(three-way catalytic converter,TWC)长期使用后起燃特性及次生污染物生成特性的变化规律,文章建立当量比燃烧的天然气发动机Pd/Rh基催化器的表面反应机理模型,利用试验数据验证模型的准确性,研究贵金属分散度对CH_(4)、CO、NO排放物起燃特性以及次生污染物NH_(3)、N 2O生成规律的影响。结果表明:相较于新鲜催化器,老化催化器虽然仍能实现对气体排放物的有效转化,但是随着贵金属分散度的降低,CH_(4)、CO、NO的起燃温度明显增加,起燃特性变差;贵金属分散度还会影响次生污染物的生成规律,分散度增加时,催化剂表面对污染物气体的吸附能力增强,增加了次生污染物的消耗,次生污染物的生成有所减少。

In order to explore the influence of long-term use on the ignition and secondary pollutants generation of the three-way catalytic converter(TWC)for a stoichiometric natural gas engine,a surface reaction mechanism model of Pd/Rh catalytic converter in natural gas engine with equivalent ratio combustion was established,and the accuracy of the model was verified by experimental data.The influence of precious metal dispersion on the ignition characteristics of CH_(4),CO and NO emissions and the generation of secondary pollutants NH_(3)and N 2O was studied.The results show that,compared with the fresh catalytic converter,although the aged catalytic converter can still achieve effective conversion of gas emissions,the ignition temperatures of CH_(4),CO and NO increase obviously and the characteristics of ignition become worse with the decrease of precious metal dispersion.The dispersion of precious metal can affect the generation rule of secondary pollutants,with the increase of dispersion,the adsorption capacity of the catalyst surface to pollutant gas enhances,which can effectively increase the consumption of secondary pollutants and reduce the generation of secondary pollutants.