Investigation Of Soot And NO_x Removal Derived From Diesel Vehicles On Perovskite-type Catalysts Modified

With the development of economy and urbanization,motor vehicle has become the most important means of transportation in our life.The emission pollutant gradually becomes a hot topic.Because of its high performance and fuel economy,diesel vehicles have attracted much attention.While the main and the most difficult to remove in the emission are particulate matter and nitrogen oxides.How to improve the removal efficiency of the pollution is the key to control diesel exhaust emissions.Therefore,it is urgent to find a kind of catalyst which has a high-performance to remove the soot particles and NO_x in the diesel exhaust.Perovskite catalyst material is considered to be the most promising material in diesel exhaust treatment with its high catalytic performance.In this paper,LaCoO₃ perovskite type composite oxide catalysts were selected as the basic catalysts.All kinds of catalysts were prepared by citric acid complexation method for catalyst precursors under different conditions.A-site and B-site ions of perovskite type catalysts were partially substituted byalkali metal ions?K+?and transition metal ions(Mn²⁺,Fe³⁺,Cu²⁺,Ni²⁺).The catalytic activity of the prepared catalyst was carried out in a constant pressure fixed bed reactor to investigate the effects of the substitution of A and B on the catalytic performance of catalyst.The catalytic activity was characterized by SEM,XRD,BET and FT-IR methods,and the catalytic mechanism was also discussed.?1?Different LaCoO₃ catalyst samples were prepared by changing the catalyst precursor precursor solution p H and calcinations temperature,to investigate the effects of different preparation conditions on the synthesis of perovskite type.The catalytic activity of catalyst samples was tested in fixed bed.The experimental results and SEM,XRD,BET results showed that the excessive temperature is easy to lead in sintering phenomenon and decreased the specific surface area of the catalyst.Acidic conditions were more favorable for complexation than alkaline conditions.Thus,the preparation of the modified perovskite type catalyst had been conducted at p H 4 for the precursor solution and calcination temperature 650 °C.?2?Addition of K⁺ on the A-site La-based ion of perovskite-type composite oxide ABO3 was carried out to prepare the La_1-x K_x Co O₃ samples?x= 0 0.5?.In order to investigate the effect of the substitution amount of K+ on the catalytic activity of soot and NO.The catalytic performance was tested in fixed bed and characterization results were also analyzed.With the increase of K⁺ doping amount,more and more K⁺ migrated into the lattice of perovskite,which resulted in increasing the oxygen vacancy in the perovskite structure,and reducing the oxidative combustion temperature of soot.The results also showed that La_1-x K_x Co O₃ had the highest catalytic efficiency in all catalyst samples,and the removal rate of soot and NO was 84.7% and 80.8%,respectively,when the K⁺ substitution amount was x = 0.3.?3?Four kinds of transition metal ions of Mn²⁺,Fe³⁺,Cu²⁺ and Ni²⁺ were selected to replace Co-based ions which located in the B-site for the perovskite-type composite oxide ABO3 to obtain La Co_1-y My O3 samples?y=0.1⁰.5?.Through a series of characterization analysis and catalytic activity experiments,it was found that the substitution of the B-site did not only keep the crystal structure of the perovskite type,but also had a stronger catalytic activity for the catalysis of soot and NO.When the substitution amount of Mn²⁺ was 0.4,the removal rate of soot is 89.2%,and the catalytic efficiency of NO is 84.5%.?4?The substitution of Mn²⁺,Fe³⁺,Cu²⁺ and Ni²⁺ with the most efficient substitution amount in the experiment was carried out by using 0.3 doping amount of K+ at the same time.The catalytic properties of catalysts for four kinds of A and B sites were investigated by a fixed bed experiment and a series of characterization analysis.It was concluded that the modified perovskite catalysts La_0.7K_0.3Co_0.6Mn_0.4O₃ sample had the highest removal rate of soot and NO,and the removal rate was 92.8% and 93.4% respectively,which had greatly improved the removal rate of NO.Through the investigation of perovskite type catalyst on the exhaust gas of simulated diesel vehicle,the performance rules of the composite components of perovskite type catalyst materials and the more effective preparation method were obtained,and the optimum removal rate of soot and NO was optimized,catalytic mechanism was also discussed.The results not only obtain a kind of non-precious metal catalytic materials for the removal of soot and NO from diesel vehicles,but also can provide theoretical support for the removal of exhaust gas from diesel vehicles.