Preparation And Catalytic Properties Of Lanthanide-Based Perovskite Type Oxides

Lanthanide perovskite oxides with high crystal structure stability,good catalytic performance and good economic benefits have been widely used in the field of catalytic soot particles and photocatalytic degradation of organic pollutants,and can change their catalytic activity by partial substitution of A and B elements.A series of lanthanide perovskite oxides were prepared by sol-gel method.The catalytic properties of La1-xKx Co0.1Ni0.9O3 perovskite and defective perovskite were investigated by Soot combustion.Meanwhile,the photocatalytic activity of La1-y Ky Ni0.9Fe0.1O3 perovskite was also studied.The main research contents and conclusions of this paper are as follows:（1）Perovskite oxide La_1-xK_xCo_0.1Ni_0.9O₃（x=0.1、0.3、0.5、0.7、0.9） was synthesized by solgel method,and its catalytic oxidation activity to Soot particles was studied.The results of XRD,SEM,EDS,BET and FT-IR showed that the perovskite catalyst had a good crystal structure,a loose porous flocculent structure,uniform particle distribution,all elements were doped and evenly distributed,and the specific surface area was large when the potassium doping amount was 0.3.All the catalysts can reduce the characteristic temperature of Soot combustion,and the catalytic activity of La0.7K0.3Co0.1Ni0.9O3 is the best.Compared with Soot combustion temperature of 692℃,the maximum combustion temperature of La0.7K0.3Co0.1Ni0.9O3 decreased by 243℃,which is 35.1%.The activation energy required by Soot combustion after adding catalyst was 68.84 k J/mol,which decreased by 27.98 k J/mol and 28.8% compared with96.62 k J/mol,indicating that the activation energy required by Soot combustion decreased and the reaction rate was accelerated by adding catalyst.At the same time,the catalyst has good stability.（2）The catalytic activity of perovskites with La_0.7K_0.1Co_0.1Ni_0.9O₃、La_0.5K_0.3Co_0.1Ni_0.9O₃、La_0.3K_0.3Co_0.1Ni_0.9O₃ defects on Soot particles was studied.Defective perovskites all have stable perovskite structure and uniform particle distribution.The activation energy of Soot by catalytic combustion was 56.81 k J/mol,74.61 k J/mol and 89.66 k J/mol,which decreased by39.81 k J/mol,22.01 k J/mol and 6.96 k J/mol compared with 96.62 k J/mol by pure combustion,respectively.Among them,La0.7K0.1Co0.1Ni0.9O3 showed the best catalytic performance,and the activation energy decreased by 41.2%,and the maximum combustion temperature was 414℃,which was decreased by 278℃ and 40.2% compared with pure Soot,suggesting that the defect at the A site was beneficial to improve the catalytic activity of perovskite.（3）Perovskite oxides La_1-yK_yNi_0.9Fe_0.1O₃（y=0.1、0.3、0.5、0.7、0.9） were synthesized by sol-gel method.The degradation effect of La1-Ykyni0.9Fe0.1O3（Y =0.1,0.3,0.5,0.7,0.9）on methyl orange was studied and the degradation mechanism was analyzed.After a series of characterization methods,when the potassium doping amount is 0.1,it has a good perovskite structure,loose and porous surface morphology,uniform particle distribution,large specific surface area and good pore structure,which can expose more active sites and help to catalyze the degradation of methyl orange molecules.All the perovskite catalysts of this series can degrade methyl orange,and La0.9K0.1Ni0.9Fe0.1O3 has the best catalytic effect.After 2h exposure to light,the degradation rate is as high as 96.5%,and the reaction rate constant is 0.0293min-1.It has high catalytic activity and stable reuse rate.