汽车尾气净化反应的UBI-QEP法研究

应用单位键指标-二次指数势(UBI-QEP)方法对汽车尾气净化反应中氮氧化物的分解进行了理论分析.结果表明,NOx的分解的可能途径为氮氧化物的直接分解、CO还原助解和氮助解离.在富氧条件下,以CO助解为主.NO的解离存在N2O中间态.Ni与Rh一样,也是优秀的还原NOx催化剂,若能有效克服表面氧的共吸附,Ni-Cu可能是良好的汽车尾气净化催化剂的主体成份.

UBI-QEP Study on Purification of Vehicle Exhaust Gas

The Vehicle exhaust gas generally contains nitrogen oxides and the fossil fuel which do greatly harm to air environment. Although the use of catalytic converters for the vehicle gas has resulted in considerable progress in the past twenty years, a theoretical framework for explaining the experimental observations is still lacking. We use the IJBI-QEP method to analyze the chemisorption species and calculate the energy of elementary reactions on six metal single crystal surfaces, Pt(III)，Pd(III)，Rh(III)，Ag(III)，Cu(III) and Ni(III). It will help us to realize the reaction mechanism and choose the best suitable catalysts. The sequence of chemisorption heat for N0, is Ni>Rh>Cu>Pd>Pt>Ag. The dissociation of N 0,de creases along the series Rh=Ni>Cu>Pd>Pt>Ag. The decomposition of NO can easy happen via NiO intermediate. From calculations at low coverage, we can see two possible pathways of N0, reduction, the direct dissociation and CO-aided dissociation. At high coverage, however, CO-aided dissociation is main pathway. For complete oxidation of carbon monoxide based catalysts may Pt, Pd, Ag and Cu are fine catalysts, but both Ni and Rh can not promote it. The Ni-Cu replace the noble metal catalysts (PI-Pd-Rh)