Study On The Catalytic Oxidation Of Carbon Soot Particles With Potassium Copper Cerium Zirconium Composite Metal Oxides

Particulate emission of diesel engine has become one of the main sources of atmospheric pollutants,CDPF-catalytic diesel particulate trap regeneration technology could capture soot particles and regenerate them by using the oxidation catalyst,which is an important engine tail gas set for meet the new emission regulations.At present the commonly used CDPF catalyst is Pt,Pd and other noble metal elements catalyst.Although the effect is stable but its cost is too high,it is urgently need to develop excellent performance and low cost of new catalyst to replace noble metal catalyst.A series of CuCeZrO_2-?and KCuCeZrO_2-?catalyst is preparated and coated in the blank vector CDPF for commercial use by using the self propagating high-temperature synthesis method?SHS?.A PM fast loading device is used to simulate the soot particles loading on CDPF carrier coated by catalyst.Using the activity test to select the best performance of the catalyst Cu_0.9Ce_0.05Zr_0.05O_2-?and K_0.18Cu_0.72Ce_0.05Zr_0.05O_2-?,whose temperature of maximum soot oxidation rate of is in 410?and 347?respectively,and the commercial Pt metal catalyst temperature of maximum soot oxidation rate is 500?under the same experimental conditions.It is indicating the oxidation of low temperature of soot particles of Cu_0.9Ce_0.05Zr_0.05O_2-?and K_0.18Cu_0.72Ce_0.05Zr_0.05O_2-?has been better than Pt catalyst for business,their temperature of maximum soot oxidation rate is more close to diesel engine exhaust temperature range150-400?.The CO₂ selectivity of Cu_0.9Ce_0.05Zr_0.05O_2-?and K_0.18Cu_0.72Ce_0.05Zr_0.05O_2-?catalysts was 96.4%and 98.1%respectively,both higher than 95.3%of Pt.The specific surface area and pore size analysis showed that the activity of Cu_0.9Ce_0.05Zr_0.05O_2-?catalyst has positive correlation with its specific surface area,but not K_0.18Cu_0.72Ce_0.05Zr_0.05O_2-?,XRD test shows that the activity of the two catalysts are divided into groups of highly dispersed on the surface of ZrO₂,TEM photos find two kinds of catalyst particles with good roundness and uniform distribution of particle size are nanometer level.The average particle size of Cu_0.9Ce_0.05Zr_0.05O_2-?is 12.4nm,the average particle size of K_0.18Cu_0.72Ce_0.05Zr_0.05O_2-?is10.2nm.Finally,the reaction process and reaction mechanism of Cu_0.9Ce_0.05Zr_0.05O_2-?and K_0.18Cu_0.72Ce_0.05Zr_0.05O_2-?are studied by X ray photoelectron catalyst surface and in situ diffuse reflectance infrared spectroscopy analysis in the soot regeneration.It has found that NO is adsorbed on the surface of catalyst and formed nitrate and nitrite,both nitrate and nitrite and NO in gas phase can oxidate soot particles.Based on this,Two routes of CDPF regeneration mechanism,the mechanism of C-N-O intermediate and Langmuir-Hinshelwood have been proposed.The reaction mechanism of CDPF C-N-O intermediate mechanism regeneration:NO is adsorbed on the catalyst surface and oxidized to NO₂,then the C-N-O complexes is formed on the catalyst surface and C in the complexes is oxidized to achieve the soot oxidation regeneration;The reaction mechanism of Langmuir-Hinshelwood CDPF regeneration:the nitrate and nitrite species are formed on the catalyst surface by the adsorption of O₂ and adsorption and oxidation of NO,the removal of soot particles is achieved by these strong oxidizing species.