Non-noble Metal-based 33DOM(Double) Perovskite-type Catalyst For Catalytic Combustion Of Soot

The soot particulate matter emitted from the exhaust of diesel engines is the main source of PM_2.5in the atmosphere,which not only causes atmospheric pollution problems,but also causes harm to people’s production,life and physical and mental health.Therefore,the elimination of soot particles is imminent,which is also a requirement for the battle against blue sky and the battle against air pollution.Catalytic purification after treatment technology is the most effective control method.The soot catalytic elimination reaction is a complex gas-solid-solid three-phase deep oxidation reaction.The catalyst currently faces three difficult problems to be solved:first,because the exhaust temperature of the motor vehicle is below 400℃,the catalyst must have low temperature performance;second,for gas-solid-solid contact reactions,the solid-solid contact efficiency must be improved;third,the active components of the currently used carbon soot purification catalysts are all precious metals,therefore,it is necessary to find active similar active components reduce the current use of precious metals.Since the particle size of soot is usually greater than 25nm,designing a three-dimensional ordered macropore（3DOM）structure material can enable the soot particles to enter the internal pore channels with the assistance of the reaction gas.The ordered pore structure is beneficial to the diffusion of the substance Increase the effective reaction contact area.（Double）perovskite-type oxides have excellent properties such as low price,stable crystal structure and adjustable valence state.At the same time,by adjusting the elemental composition in（double）perovskite,the oxidation-reduction performance of perovskite can be effectively improved,which can effectively reduce the use of precious metals.This thesis mainly studies the design and preparation of non-precious metal-based three-dimensional ordered macroporous（double）perovskite-type catalysts and their catalytic combustion performance of soot particles.In this paper,a variety of 3DOM（double）perovskite type catalysts are prepared by colloidal crystal template method,methanol glycol complex method and citric acid combustion method.The spatial morphology,elemental composition,phase structure and redox performance of the catalyst were thoroughly investigated using XRD、SEM、TEM、BET、H₂-TPR、Raman、XPS、FT-IR、NO-TPO and In situ-Raman,and the results were also related to the performance of catalytic soot combustion.The mechanism of soot catalytic combustion is discussed in depth.The main innovations and findings of this article are as follows:（1）A series of 3DOM perovskite La_1-xK_xNi O₃catalysts were prepared by colloidal crystal template method and methanol ethylene glycol method.The K element in the 3DOM La_1-xK_xNi O₃catalyst is evenly substituted into the crystal lattice of the perovskite oxide,which can improve the formation of oxygen vacancies and enhance the redox performance.The 3DOM La_1-xK_xNi O₃catalyst exhibited good soot combustion catalytic performance,of which the 3DOM La_0.95K_0.05Ni O₃catalyst has the highest catalytic activity for soot oxidation.The values of T₁₀,T₅₀,T₉₀and S^m_CO2are 289,338,372℃and 98.2%,which are close to the catalytic activity of Pt-based catalysts under loose contact conditions,.his is mainly due to the doping of K element improves the valence of Ni and increases the number of oxygen vacancies,thereby increasing the density of surface active oxygen.（2）A series of 3DOM double perovskite-type La₂Ni B’O₆catalysts（B’=Mn,Fe,Co,Cu）were synthesized using colloidal crystal template method and citric acid combustion method.3DOM La₂Ni B’O₆catalyst can effectively enhance the contact efficiency between the reactants and the catalyst,and can also improve the activation performance of the gaseous reactants（O₂and NO）,thereby improving the catalytic performance of the carbon smoke and the catalyst in loose contact conditions.Among all the catalysts,3DOM La₂Ni Co O₆catalyst has the highest catalytic activity for soot catalytic oxidation.The values of T₁₀,T₅₀,T₉₀,and S^m_CO2are 288,362,412℃,and98.2%,respectively;its TONs and TOF values reached 7.80 and 0.151 h^-1at 310℃,and the apparent activation energy（Ea）value dropped to 65 k J mol^-1,which indicates that the catalyst has the lowest energy barrier during the catalytic oxidation of soot.Based on the characterization results of in-situ Raman,Soot-TPO and NO-TPO,the catalytic mechanism of 3DOM La₂Ni Co O₆soot elimination catalyst is proposed.And it is determined that the step of surface active oxygen oxidizing NO to NO₂is the rate control step of catalytic soot elimination.3DOM perovskite type La₂Ni B’O₆is a typical non-precious metal nanocatalyst,and has practical application potential in eliminating diesel soot.（3）A series of double perovskite La_2-xK_xNi Co O₆（x=0.05-0.40）catalyst with a three-dimensional ordered macropore（3DOM）structure was synthesized by the colloidal crystal template method.The periodic arrangement of[Ni O₆]and[Co O₆]octahedrals and low-valent alkali metals in La_2-xK_xNi Co O₆induces the formation of coordinated unsaturated B-site ions as active sites for activating O₂and NO.The catalytic performance of the 3DOM La_2-xK_xNi Co O₆catalyst depends on the high surface oxygen density,while the 3DOM La_1.80K_0.20Ni Co O₆catalyst exhibits the highest soot combustion activity,with T₅₀,S^m_CO2and TOF_Ovvalues of 348℃,99.3%and 0.204 h^-1.It has better performance than Pt-based catalysts.And the catalyst showed very stable catalytic performance in seven cycles of experiments.The design and synthesis of 3DOM La_2-xK_xNi Co O₆is of great significance for the development of non-precious metal catalysts to eliminate diesel soot particles.