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考察了Pd-X(X=Ni,Sn,Ca)/TiO2-Al2O3催化剂上氢气选择性还原NOx的性能.发现通过Sn和Ni改性后催化剂在高于200℃后的活性有所提高,尤其是Pd-Sn/TiO2-Al2O3催化剂既能保持Pd/TiO2-Al2O3低温良好活性的同时,高温活性及N2的选择性也有明显提高,Sn的最佳负载量为2%(质量比).X射线衍射(XRD)结果表明改性Pd-Sn/TiO2-Al2O3催化剂中Pd与Sn之间的相互作用促进了Pd在载体上的分散.H2程序升温还原(H2-TPR)结果表明,Sn的加入促进了活性组分Pd以Pd0的形式存在,并且提高了Pd/TiO2-Al2O3催化剂的氧化-还原性能,从而使其活性和N2选择性得到提高.NOx程序升温脱附(NOx-TPD)结果表明,Sn和Ni的添加有助于Pd/TiO2-Al2O3催化剂上NOx的吸附以及NO氧化为NO2的进行,这可能是活性和选择性提高的重要原因.
The performance of selective reduction of NOx on hydrogen over Pd-X (X = Ni, Sn, Ca) / TiO2-Al2O3 catalyst was investigated. The results show that the activity of catalysts modified by Sn and Ni is higher than 200 ℃, The Pd-Sn / TiO2-Al2O3 catalyst not only maintains good activity at low temperature of Pd / TiO2-Al2O3, but also improves the high temperature activity and the selectivity of N2. The optimal loading of Sn is 2% (mass ratio) The results of X-ray diffraction (XRD) indicated that the interaction between Pd and Sn in the modified Pd-Sn / TiO2-Al2O3 catalyst promoted the dispersion of Pd on the support. H2-TPR results showed that the addition of Sn promoted The active component Pd exists in the form of PdO and increases the oxidation-reduction performance of the Pd / TiO2-Al2O3 catalyst, so that its activity and N2 selectivity are improved.NOx temperature-programmed desorption (NOx-TPD) The addition of Sn and Ni contributes to the adsorption of NO x on Pd / TiO 2 -Al 2 O 3 catalyst and the oxidation of NO to NO 2, which may be the reason for the increase of activity and selectivity.