碱土元素掺杂的BaFeO3钙钛矿型催化剂的NOx储存性能

采用溶胶-凝胶法制备了Ba_1-xM_xFeO₃ (M=Mg, Ca, Sr; x=0, 0.1, 0.2)系列钙钛矿型NO_x储存还原(NSR)催化剂, 考察碱金属元素Mg、Ca 和Sr 的掺杂对BaFeO₃ 钙钛矿NO_x 储存和氧化性能的影响. 结果表明, 在250-400 ℃范围内Mg的掺杂提高了BaFeO₃钙钛矿的NO_x储存性能, 其中以Ba_0.8Mg_0.2FeO₃样品的NO_x储存性能最佳, 在温度350 ℃时NO_x储存量高达1200 μmol·g^-1以上, NO→NO₂转化率为53.4%. 与BaFeO₃比较,Ba_0.8Mg_0.2FeO₃样品在250 ℃进行NO_x储存时就出现了单齿硝酸盐, 并随储存温度的变化而变化, 它的数量与NO_x储存量有相同的变化趋势. 傅里叶变换红外(FTIR)光谱结果表明, 与BaFeO₃相比, Ba_0.8Mg_0.2FeO₃样品NO_x储存量增大的原因在于: 一方面, 形成了具有A位缺陷的钙钛矿结构, 产生大量能够用于储存NO_x的氧空位; 另一方面, 未进入钙钛矿晶格的Mg元素可能以碱性氧化物的形式与NO_x作用形成了单齿硝酸盐.

NOx Storage Performance of Alkaline Earth-Doped Perovskite-Type BaFeO3 Catalysts

A series of Ba_1-xM_xFeO₃ (M=Mg, Ca, Sr; x=0, 0.1, 0.2) perovskites were prepared by the sol-gel method as NO_x storage reduction (NSR) catalysts. The effect of doping with alkaline earth metals (Mg, Ca, and Sr) on the NO_x storage and oxidation performance of the BaFeO₃ perovskites was investigated. Doping with Mg enhanced the NO_x storage capacity (NSC) of the BaFeO₃ perovskites in the temperature range 250-400 ℃, the Ba_0.8Mg_0.2FeO₃ perovskite exhibited the best NO_x storage performance, which reached its maximum at 350 ℃, with NSC>1200 μmol·g^-1 and the NO→NO₂ conversion of 53.4%. Compared with BaFeO₃, the monodentate nitrate appeared clearly for the Ba_0.8Mg_0.2FeO₃ sample after storing NO_x at 250 ℃. The amount of the monodentate nitrate on Ba_0.8Mg_0.2FeO₃ varied with the NO_x storage temperature in a similar manner to that of its NSC. Fourier transform infrared (FTIR) spectra indicated that doping with Mg induced an A-site deficient perovskite structure in BaFeO₃, which readily generates oxygen vacancies that act as the active sites for NO_x adsorption. Moreover, the residual MgO on the catalyst might also improve the NSC of the sample by forming the monodentate nitrate.