Investigation Of Performance Of Lamellar K₂Ti₄O₉ Soot Combustion Catalyst

Diesel vehicles gradually occupied the market owing to the advantages of high economy,great power and low CO₂ emissions.But the atmosphere was polluted by soot particles of the exhaust gas was a serious threat to human health and development.Diesel Particulate Filter（DPF）was considered as the most effective strategy to reduce soot particle emission.And how to make DPF regeneration became the focus of scholars.Among them,the potassium-based catalysts had good catalytic performance for soot combustion in low-temperature.While it was easy to lead the sublimation of potassium element in high temperature environment,resulting in catalyst deactivation.Fixing K on a stable structure was a feasible design idea to ensure activity and stability.The lamellar structure K₂Ti₄O₉ matched this experimental idea.The main research contents and conclusions of this work were as follows:First,the sol-gel method was used to prepare the lamellar structure K₂Ti₄O₉ with tetrabutyl titanate and potassium acetate as the titanium and potassium source,and the structural characterization and activity test were performed.The results showed that compared with the blank soot experiment,the introduction of K₂Ti₄O₉ catalyst reduced the soot ignition temperature by nearly 130℃,which was only 319℃（loose contact）,and the selectivity to CO₂ increased from 41.23%to 93.21%.In order to further explore the stability of the K₂Ti₄O₉ catalyst,aging experiments and repeatability tests were conducted.The results showed that the aging temperature had some effect on the activity of the K₂Ti₄O₉ catalyst owing to the K₂Ti₄O₉ in the high temperature environment was partially converted to K₂Ti₆O₁₃.The repetitive tests had almost no influence on the activity of K₂Ti₄O₉ catalyst,and after 5 cycles,the T_m and T_f only increased by 22℃and 15℃.Meanwhile the selectivity to CO₂ was still higher than 90%.It indicated that K₂Ti₄O₉catalyst had great catalytic activity and repeatability.Secondly,with the variable amount of CuO and MnO₂ introduced,CuO-K₂Ti₄O₉（X）and MnO₂-K₂Ti₄O₉（X）composite catalysts were designed by the impregnation method.And the soot catalytic combustion process was analyzed and discussed.The activity test results showed that compared with the pure K₂Ti₄O₉ catalyst,CuO-K₂Ti₄O₉（X）and MnO₂-K₂Ti₄O₉（X）composite catalysts reduced the light-off temperature,and the burn-out temperature reduced by about 100℃,extremely,which greatly shortened the soot burning time.The optimized CuO-K₂Ti₄O₉（2）and MnO₂-K₂Ti₄O₉（1/2）reduced the soot ignition temperature to 277°C and 281°C,respectively,and achieved complete soot combustion at 450°C and had a good cycle life.A series of characterization results speculated that the main reason for its high activity were that K⁺occupied the space between the lamellar structure,which can transfer electrons between the catalyst bulk and the surface to induce K₂Ti₄O₉lattice oxygen to be converted to active oxygen species.After the transition metal oxide was introduced to the surface of K₂Ti₄O₉,the interaction may promote the formation of the“pumped”active oxygen species path from K₂Ti₄O₉:a large amount of oxygen vacancies was formed at the interface,and the lattice oxygens of K₂Ti₄O₉ were activated under the action of K⁺,and migrated to the interface to fill the oxygen vacancy.Meanwhile the migration of active oxygen species to transition metal oxides will induce transition metal oxides to generate more active oxygen species as“reactants”.Finally,the active oxygen species migrated to soot surface to produce CO₂.In this system,the catalyst was equivalent to a transfer station for oxygen species,which can adsorb and activate gas-phase oxygen,improve the mobility of lattice oxygen,and continuously supply active species for soot catalytic combustion.