The Synthesis Of Lanthanum Nickel Perovskite-oxides Catalysts And Its Catalytic Properties In Simultaneous Removal Of Soot And NO_x

Soot and NO_x from diesel engines exhaust were harmful to environment and human health. Therefore, research of the catalysts which can simultaneously remove NO_x and diesel soot has vital significance. Perovskite-type oxides（ ABO3） showed high catalytic activity of simultaneous removal of NO_x and diesel soot due to the special structure. In this study, a series of lanthanum-nickel perovskite-type complex oxide catalysts were synthesized by sol-gel method and the catalysts were modified by doping other elements at A site, B site and co-doped A and B site. The prepared catalysts were characterized by XRD, H2-TPR, BET, XPS and the catalytic activity of the catalysts was evaluated by O2-TPO or NO-TPO. Moreover, the influence of different synthesizing methods and different calcination temperature on structure and the properties of catalysts were also evaluated.1. A series of La1-xKxNi O3 catalysts were synthesized by sol-gel method. The H2-TPR and XPS results showed, with the increasing amount of K+, more adsorption oxygen existed on the surface indicating the presence of more oxygen vacancies in the catalyst and the activity of catalyst with K+ doping quantity increases.. More oxygen vacancies are favorable for forming activation of oxygen species. The XRD results indicated that when x≤0.3 can form stable hexagonal system perovskite structure, the La0.7K0.3Ni O3 catalyst gained the better catalytic activity of removal soot and the Ti and Tm were 312.4 ℃ and 319.3 ℃, respectively.2. A series of La Ni1-yMyO3 catalysts were synthesized by sol-gel method and doped B site by Cu, Co, Mn, Cr, Ag. Then these catalysts were characterized and evaluated by O2-TPO. The XRD results indicated the catalyst was mixed with silver and La Ni O3 when M=Ag; When M=Cu, Co, Mn, Cr, the catalysts were hexagonal system perovskite structure. Besides, the O2-TPO results showed when M=Cu, the catalyst had better catalytic properties.3. When doped A site by K and doped B site by Cu, Co, Mn, Cr, respectively. The H2-TPR and XPS results implied the synergistic effect emerged when co-doped A site and B site by K+ and Cu2+, respectively. That leads La_0.7K_0.3Ni_0.9Cu_0.1O₃ appeared the lowest Ti and Tm were 268.1 ℃ and 272.8 ℃, respectively. The O2-TPO results showed the catalytic activity of removal soot ordered: La_0.7K_0.3Ni_0.9Cu_0.1O₃>La0.7K0.3Ni0.9Mn0.1O3>La0.7K0.3Ni0.9Co0.1O3>La0.7K0.3Ni0.9Cr0.1O3.4. The catalytic properties of La_1-xK_xNi_1-yMyO₃（M=Co, Mn, Cu）in simultaneous removal of NO_x and diesel soot were researched. According to the NO-TPO results, with the increasing amount of K+, the Ti decreased and the PN2%max gradually increased at the same time. Then using Co, Mn, and Cu doped the B site of La0.7K0.3Ni O3, the Ti decreased more and PN2%max increased more. La_0.7K_0.3Ni_0.9Cu_0.1O₃ showed the best catalytic activity in simultaneous removal of NO_x and diesel soot, the Ti and PN2%max were 402.6 ℃ and 93.6%, respectively. Comparing the TPO curve, there is highly positive correlation between TPO curves and PN2% curves, which inferred the mechanism of simultaneous removal of NO_x and diesel soot might be attained mainly by means of combustion soot by activation of oxygen species on the catalysts surface and converting NO to NO2 which has stronger oxidation ability.5. Comparing the sol-gel method, polyacrylamide gel method, biotemplating method and impregnation mothed synthesized La_0.7K_0.3Ni_0.9Cu_0.1O₃ catalysts. The SEM results showed different synthesizing methods could affect the catalyst’s morphology. Biotemplating method and polyacrylamide gel method synthesized catalysts had the developed 3D space network structure. The O2-TPO results showed the biotemplating method synthesized catalyst gained the best catalytic property of combustion soot under the tight contact condition, the Ti and Tm were 253.7 ℃ and 273.6 ℃, respectively. The catalysts prepared by sol-gel method and polyacrylamide gel method showed the worse catalytic property. The impregnation method synthesized catalyst showed the worst catalytic property.6. Study on calcination temperature, the XRD, BET and O2-TPO results indicated that the calcination temperature is too low or too high, the catalyst components, crystallinity, crystallite size and specific surface area will be affected, which influenced the catalytic activity of the catalysts. When calcination temperature was 800 ℃, there was high degree of crystallization of catalyst crystal, grain reunion, specific surface area decreased and the catalytic property declined. When calcination temperature was 600 ℃, the catalyst was mixed with La2O2CO3, Ni O and La Ni O3, the catalytic property was poor. Determined by screening experiment of calcination temperature, 700 ℃ was the appropriate calcination temperature.