Study On Doping And Anti-deactivation Properties Of Perovskite-type Oxide La₄BaCu₅O_13+δ

Perovskite-type composite oxide is a funtional materials which are widely used, especially the excellent catalytic properties. They have attracted particularly attentions because of their special applications as the most promising to replace precious metals catalysts materials, how to improve the catalytic activity of perovskite-type composite oxide is an important aspect of the study. In this paper we choose perovskte-type oxides as disquisitive object, researched their preparation and properties, and provided academic and experimental data for catalytic instrument of automobile's exhaust.In this paper, a series of layered perovskite-type La-Ba-Cu-based catalyst were synthesized by citrate acid sol-gel method. Doping Sr, Ca, Mg, K in the position of "A", and doping Co, Fe, Cr, Mn in the position of "B" to improve their related properties. The physical and chemical properties and function mechanism of different doping catalysts were characterized by means of XRD, SEM, BET, TPD, the influence of doping on catalytic properties were researched. The catalytic activities were evaluated by testing the conversion efficiency of CO, CH4, and NO gas. Meanwhile, thermal aging and sulfur aging experiments were taken on fresh catalysts, the anti-sulfuration and anti-aging properties on doping catalysts were studied.The XRD spectrum demonstrated that catalysts which single-doped Fe, Co and double doping Fe, Co in the position of "B" and composite doping K, Co in the position of "A","B" were formed a high purity perovskite-type structure at 750℃, but samples which single-doped in the position of "A" almost have a impurity phase La2CuO4. From the microstructure of catalysts, we can be observed that particle size of the doped samples decreased, and evenly dispersed, less conglobation. The more prominent is the La4BaCu4CoO13+δand La4Ba0.5K0.5Cu3Co2O13+δ, their particle size is about 50-100nm. Meanwhile, BET results also confirmed that they had a smaller surface area. The O2-TPD demonstrated that the surface adsorbed oxygen increased on the catalysts which doping Co, Fe in the position of "B" and composite doping K, Co. Catalytic activity tests demonstrated that the catalytic activity is closely related with the concentration of surface adsorbed oxygen, which had the highest activity is La4Ba0.5K0.5Cu3Co2O13+δ, their light-off temperature T50 of CH4, CO, NO were 250℃,265℃,280℃.After thermal aging at 900℃for 8h, the catalysts particles and surface area had an obviously decrease, in which, after aging the La4BaCu4CoO13+δhad largest surface area which was 4.967m2/g, and had better anti-aging properties. After sulfuration, the structure of La4Ba0.8Sr0.2Cu5O13+δremained steady, haven't occurred structural disaggregation, but La4BaCu4CoO13+δand La4BaCu4Fe0.5Co0.5O13+δhave different degree of structural disaggregation, formatted the corresponding metal sulfate.