Study On Microwave Assisted Regeneration Characteristics Of Deactivated Three-way Catalyst And System Design

While fuel vehicles bring convenience to the society,they also cause serious pollution to the ecosystem.Automobile emission purification in exhaust pipes is currently a widely adopted measure,where three-way catalyst plays a key role.The catalytic activity largely determines the gas conversion efficiency.Since the catalytic activity damps as time passes,catalyst regeneration is essential to prolong the life of the catalyst and realize the recycling of the catalyst.Based on the unique advantages of microwave penetration and selective heating,this paper proposes a microwave-assisted regeneration method for deactivated three-way catalyst,and optimizes the catalyst regeneration process in terms of catalyst pore structure characteristics and catalytic characteristics.Firstly,under microwave irradiation,the pore expander rapidly expands to vaporize;meanwhile,the specific surface area increases with the expansion of the catalyst pore structure.Based on those two characteristics,the paper investigated the pore structure characteristics of the microwave-assisted regeneration catalyst.Meanwhile,the influence of the type and concentration of pore expander and the power and time of microwave on the pore expanding effect was also studied.It was found that the pore-expansion effect reached the optimum using the ethanol solution volume solubility of 20%,the microwave irradiation power of 800W,and the irradiation time of 420s.The testing results suggested that the specific surface area was increased by 22.95%compared with the deactivated catalyst.Then the pore structure regenerated catalyst under the optimal parameters is selected for testing the conversion effect of gas in the oxygen-enriched and oxygen-depleted environment.Meanwhile,the microwave-assisted catalyst expansion and regeneration process was explored through some characterization methods.The microwave helped the pore expander vaporize and expand the catalyst pore structure,resulting in tiny pores.Hence,the content of active ingredients on the catalyst surface was increased.After the pore expansion of the catalyst mixed with a suitable amount of microwave absorbent silicon carbide,active ingredients appear on the surface of the catalyst even in a high-temperature environment.Secondly,taking advantage of the characteristics of additives to enhance the catalyst regeneration activity,the study of catalytic modification of microwave-assisted regenerated catalyst is carried out.In the investigation of the cerium-based regenerated catalyst mixed with different mass fractions(0.5%,1.0%,2.0%and 4.0%)of CeO2,it is found that the cerium-based regeneration catalyst with 1.0%CeO2 has the best recovering effect.Besides,the cerium-based oxide with excessive addition of CeO2 encapsulates the active components of the catalyst will reduce the catalyst regeneration activity.On this basis,using the combination of CeO2 and ZrO2 with different mixing ratios of 1%mass fraction(8:2,6:4,5:5,4:6,2:8),it is found that when the ratio is 5:5,the recovering effect of the cerium-zirconium bimetallic regeneration catalyst is the best.CexZr1-xO2 crystal is formed after the addition and modification of CeO2 and ZrO2 in equal proportions,which can fully play the role of CeO2 and ZrO2 in adjusting the oxygen content in the redox reaction,improve the stability and dispersion of active components,and enhance the activity of the regenerated catalyst.When the content of CeO2 and ZrO2 is significantly different,the CexZri-xO2 crystal has poor structure stability and poor performance in synergistically regulating the oxygen content of the redox reaction;Furthermore,based on the targeted enhancement of microwave absorbents,the recovery effect of regenerated catalyst with different mass fractions of SiC(0.5%,1.0%,2.0%and 4.0%)was investigated.It is found that the regenerated catalyst doped with 0.5%SiC has the best recovery effect.An appropriate amount of SiC,the strong absorbing medium,is added to enter CexZr1-xO2 solid solution crystals to enhance the hot spot effect of microwave irradiation catalyst.It can make the microwave radiation act on the active site of the catalyst and further increase the crystallization rate of cerium oxide and zirconium oxide in the transition state.Excessive SiC can wrap the additives CeO2 and ZrO2,hinder the additives CeO2 and ZrO2 to assist the metal active center to play its effect,and then irreversible loss occurs.Finally,based on the pore structure characteristics of the microwave-assisted regeneration catalyst and the research on the catalytic modification of the microwave-assisted regeneration catalyst,combined with the structure of the three-way catalyst and the microwave system,a portable deactivated three-way catalyst microwave-assisted regeneration system was designed.