低温等离子体处理对NiO/Al_2O_3吸附NO_x的促进作用

NO_x Storage Capacity Enhancement on NiO/Al_2O_3 Pretreated with a Non-thermal Plasma

采用共沉淀法制备了不同NiO负载量的NiO/Al2O3催化剂,并用于NOx储存还原技术去除NOx反应中.结果表明,当Ni/Al摩尔比为0.3时,NiO/Al2O3样品的NOx吸附量最大;随着Ni含量的增加,NiAl2O4晶相减少.沉淀物在高温煅烧前利用低温等离子体处理后,所得催化剂吸附NOx的能力明显增强,当Ni/Al摩尔比为0.3的催化剂,NOx吸附量由未处理时的345μmol/g增至经处理后的477μmol/g.研究发现,经低温等离子体处理后,催化剂上粒子更加分散,比表面积增大.另外,利用原位红外光谱分析了催化剂吸附NOx的机理.结果表明,吸附的NO首先在催化剂表面以桥式亚硝酸盐形式存在,然后转变成不同形式的硝酸盐.

In the NOx storage reduction （NSR） technology used to remove NOx from lean burn engines,the NOx storage material is crucial.For NiO/Al2O3 catalysts with different NiO loading prepared by coprecipitation,the maximum storage capacity for NOx occurred at a Ni/Al molar ratio of 0.3 in the catalyst.The intensity of the NiAl2O4 diffraction peak decreased with increased nickel content.When the catalysts were pretreated by a non-thermal plasma （NTP） before calcination at high temperature,the adsorption capacities for NOx increased,with an increase from 345 to 477μmol/g on the NiO/Al2O3 catalyst with the Ni/Al molar ratio of 0.3.The metal dispersion was increased with the NTP treatment,which resulted in a high surface area.The NOx storage mechanism was discussed on the basis of DRIFTS results,which indicated that NO was first adsorbed on the surface as bridged nitrites,and then the nitrites species was transformed into different kinds of NO3？ adsorbed species.