NOx Storage Capacity Enhancement on NiO/Al2O3 Pretreated with a Non-thermal Plasma

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 477 μmol/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.

摘要：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 345 μmol/g 增至经处理后的 477 μmol/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.

The NOx storage capacity of NiO/Al2O3-0.30(P) was larger than that of NiO/Al2O3-0.30(C) at both low and high temperatures. NOx amounts desorbed were more from the catalysts after a non-thermal plasma treatment.Figure optionsDownload as PowerPoint slide