Development of porous nano-structured materials with heterojunction structure and application to low temperature de-NOx catalysts

研究了水滑石Mg_<0.74>Al_<0.26>（OH）_2（NO_3）_<0.26>的阴离子交换性能，并用于制备高分散贵金属多孔催化剂。XAFS分析表明，在用配合物PtCl_6^和PdCl_4^进行阴离子交换时<2-><2->，HT层间的NO_3^-部分取代了配体。在H_2气流中加热时，硝酸根配位体被还原放出N_2，由此形成的空位随后被层间NO_3^-占据。层间贵金属的这种催化作用促进了NO_3^-从层间空间的去除，从而将层状结构转化为多孔骨架。Pt-HT催化剂在70℃时可达到82%的NOx转化率，而负载型Pt/MgO催化剂则需要更高的温度90℃才能达到87%的NOx转化率。与负载型Pd/MgO催化剂相比，Pd-HT催化剂在较低温度下具有较高的NOx转化率。因此，Pt-HT纳米复合物 ...更多信息 在70℃下，用0.1%NO，0- 10%O_2，Pt，|Nafion| Pt、H_2O。在Pt阴极上，具有H^+导电性的固体聚合物电解质（SPE）在催化NO-H_2反应中起着关键作用。结果表明，由于Pt表面被稳定的NO_3物种覆盖，阻碍了氧在Pt表面的吸附，从而抑制了H_2-O_2竞争反应。在[≤]100℃时，H_2-O_2反应的抑制效果最好，与SPE的最佳工作温度范围一致。在阴极室中填充1wt%Pt/ZSM-5催化剂，可以提高NO在过量O_2中的还原效率。SPE电池和Pt催化剂之间的组合可以广泛地应用于强氧化气氛中的新型低温脱硝过程。少

The anion exchange property of hydrotalcite(HT),Mg_<0.74>Al_<0.26>(OH)_2(NO_3)_<0.26>, was studied for the preparation of porous catalysts containing highly dispersed noble metals. In the anion exchange using complexes, PtCl_6^<2-> and PdCl_4^<2->, partial replacement of the ligand with NO_3^- in the HT interlayer occurred as was revealed by XAFS analysis. On heating in a H_2 flow, the nitrate ligand would be reduced to evolve N_2 and the vacant site thus formed can subsequently be occupied by NO_3^- in the interlayer. Such a catalytic role of interlayer noble metals facilitates the removal of NO_3^- from the interlayer space and thus converts the layered structure into a porous framework. The Pt-HT catalyst allowed 82% NO_x conversion at 70℃, whereas a supported Pt/MgO required higher temperature 90℃ where 87% NO_x conversion was obtained. Similarly, Pd-HT catalyst allowed higher NO_x conversion at the lower temperature compared with a supported Pd/MgO catalyst. Thus, Pt-HT nanocompos … More ites were found to be active for the low temperature NO-H_2 reaction in the presence of excess O_2.On the other hand, the reduction of NO to N_2/N_2O in the presence of excess O_2 has been successfully achieved at 70℃ using an electrochemical cell of the type,0.1% NO,0-10% O_2,Pt |NAFION| Pt,H_2O. An H^+-conducting solid polymer electrolyte(SPE) plays a key role in evolving hydrogen on the Pt cathode, where the catalytic NO-H_2 takes place. It was revealed that the competitive H_2-O_2 reaction is suppressed because the Pt surface was covered with stable nitrate(NO_3) species, which blocks oxygen adsorption hereon. The inhibition of H_2-O_2 reaction becomes most efficient at 【less than or equal】100℃ in agreement with the optimal operation temperature range of SPE. The reduction efficiency of NO in an excess O_2 could be improved by packing 1 wt% Pt/ZSM-5 catalyst in the cathode room. The combination between the SPE cell and Pt catalysts can broadly be applied to novel low-temperature deNOx processes in a strongly oxidizing atmosphere. Less