Study On Four-way Catalyst Of Purification Diesel Smoke

CO, Cx Hy, PM and NOx from the diesel smoke are the primary offenders of environmental pollution,the most effective method to solve this environmental pollution is catalytic oxidation-reduction after treatment technology of purification diesel fumes.So it is urgent to research the catalyst which is high effiency and cheap price.The study results show that perovskite type four-way catalysts have high catalytic efficiency in purifying diesel smoke,especially the La-K-Co-Mn-O series catalyst.In this paper,K ion replace part of La ions on A bits and Mn(Mn2+、Mn3+、Mn4+、Mn5+、Mn6+、Mn7+)replace part of Co(Co2+、Co3+、Co4+)on B bits in the La Co O3 by chemical tailoring method.Four-way catalysts active components La1-x Kx Co1-y Mny O3 with perovskite structurewere were prepared by soi-gel,citric acid complexation and solution combustion synthesis.La1-x Kx Co1-y Mny O3 were impregnated into the honeycomb ceramic carrier by using solution impregnation method or suspension slurry to get perovskite type catalyst.Removal performance of CO,Cx Hy,PM and NOx,simulated flue gas as diesel exhaust,is tested by self-made performance evaluation device.And by the BET, XRD, SEM, EDS and so on characterization methods to analyse.Study results show:Select La0.8K0.2Co0.8Mn0.2O3 and La0.8K0.2Co0.7Mn0.3O3 as the research object.According to catalytic REDOX CO,Cx Hy,PM and NOx conversion rate of size,Sort for active component calcining temperature:750℃>800℃>700℃>900℃> 600℃;CO,Cx Hy and PM conversion rate are 99.9%,95.4% and 90.3% respectively by 6 h 750℃ calcination synthesis catalyst for catalytic oxidation,PM initial burning temperature is 225 ℃;the maximum conversion temperature is 318 ℃,NOx the maximum conversion rate of 73.6%.Select La0.8K0.2Co0.7Mn0.3O3 of 750 ℃calcined synthesis after six hoursas the research object.Higher catalytic efficiency by solution impregnation method prepared catalyst than suspension slurry method load catalyst.Viscosity and coating amount of middle tier γ-Al2O3 affect catalyst active component impregnation content and service life.Catalyst active component content determines catalyst performance.Experimental results show that Solution dipping method, γ-Al2O3 content as the carrier quality 10%, the content of active component as the carrier quality 10% is the optimal choice of monolithic catalyst from the economy.Air-fuel ratio decision CO, Cx Hy, PM and NOx thoroughness of interactions reaction.Laboratory simulation test shows that:simultaneous removal of CO, Cx Hy, PM and NOx is the most appropriate with 4% oxygen in total volume.All La1-x Kx Co1-y Mny O3 have characteristic peaks of the perovskite structure crystal when x=0.1、0.2、0.3、0.4 and y=0.1、0.2、0.3、0.4.Partly Co3+ shift Co4+ when La3+ in La Co O3 is partly replaced by K+.So at the same time there is Co3+ and Co4+.The ionic radius of Co4+ is smaller than Co3+.Therefore, lattice appeare slight distortion.La1-x Kx Co1-y Mny O3 lattice distortion because ++<33Co Mnrr when Co in La Co O3 is partly replaced by Mn.To increase the degree of distortion when La and Co are simultaneously partly replaced by K and Mn.A small amount of lattice distortion make increase using gap,space structure and space oxygen quantity and specific surface area.It is advantageous to the four effective removal CO,Cx Hy,PM and NOx.Catalytic oxidation PM works best when x=0.2,to achieve 93.8%.Catalytic oxidation-reduction CO,Cx Hy and NOx work best when y=0.3,to achieve respectively 100%,99.9% and 75.8%.From the thermodynamics point of view,the gibbs free energy variables of CO,Cx Hy,PM and NOx mutual reaction are less than zero,which indicate NOx is reducted by CO,Cx Hy and PM.But reaction temperature influence it.La0.8K0.2Co0.8Mn0.2O3 make catalyze oxidation-reductio more easily reaction for CO,Cx Hy,PM and NOx and gibbs free energy variables lower.From the dynamics point of view,La0.8K0.2Co0.7Mn0.3O3 can accelerate catalysis oxidation-reductio reaction rate of CO,Cx Hy,PM and NOx.To improve four-way catalytic efficiency.