柴油机冷启动HC在LTA沸石中吸附的分子模拟

摘要

为了对柴油机冷启动过程产生的碳氢化合物(HC)进行吸附处理,需要对冷启动过程中的HC吸附过程进行研究.以乙烯(C2H4)和丙烯(C3H6)为探针分子,利用巨正则蒙特卡罗法(GCMC)对LTA型分子筛的HC吸附性能进行分子模拟研究,获得特定温度下的纯组分和混合组分吸附等温线以及吸附粒子云分布.研究结果表明:在柴油机冷启动条件下,C3H6和C2H4在LTA型分子筛上的吸附量显示出类似的趋势,均随着压力的升高而增加,随着温度的升高而减少；当二者同时存在时会发生了竞争行为,C2H4受到的影响比C3H6要大,LTA型分子筛对C3H6的吸附效果要好于对C2H4的吸附效果；C3H6在LTA型分子筛的α笼和β笼中均有分布,而C2H4在LTA型分子筛中的分布主要集中在分子筛的α笼中,只有少量分布在分子筛的β笼中.%The adsorption behaviors of diesel cold starting emissions in LTA zeolite was studied by grand canonical Monte Carlo (GCMC) simulation.Ethylene and propylene were used as probe molecules for HC.Adsorption isotherms under special temperatures for pure component,binary mixtures and mass cloud of the adsorbates were obtained.The results show that the average loading of ethylene and propylene has the similar trend,and both of them increase with the increase of pressure and decrease significantly with the increase of temperature.The binary mixtures show competitive adsorption behavior,and the adsorption effect of propylene in LTA zeolite is better than adsorption effect of ethylene in LTA zeolite.From the mass clouds of the simulation,it can be found that propylene distributes in the α cage and β cage of the LTA zeolite.But ethylene distributes mainly in the α cage,and only a few distribute mainly in the β cage of the LTA zeolite.