Synthesis Of OMS-2 Supported Pd And Their Low-temperature CO Catalytic Oxidation

It is of great value to explore efficient ways of CO abatement in terms of environmental protection and energy conservation.Exploring highly active and stable catalysts becomes a critical route for catalytic oxidation of CO.Palladium(Pd)component is an active and hydrothermal-stable among platinum group metals(PGMs)and has been commercial applied to the catalytic oxidation of CO and HC.To date,however,to lower the Pd content and light-off temperature of these catalysts are major challenges of developing these catalysts.Adjusting specific surface area(SSA)and surface chemical properties become effective roles of promoting catalytic activity and reducing cost.Octahedral molecular sieves(OMS)of manganese oxide as one kind of a-MnO2 has porous structure,mixed valence,tunable surface acid-base property and ionic-exchange property.In recent years,researchers focusing on octahedral molecular sieves of manganese oxide as support.Thus,the present work attempted to explore the influence of different preparation method and calcination temperature on the composition and structure of OMS-2.As-prepared OMS-2 was supported Pd(1%wt)and employed CO low-temperature catalytic oxidation.Two section of the present works are concluded as follows:(1)Manganese oxide octahedral molecular sieves(OMS-2)synthesized from hydrothermal(H-OMS-2),reflux(R-OMS-2),co-precipitation(C-OMS-2)and solid phase(S-OMS-2)methods have been impregnated with palladium and used for CO catalytic oxidation.The hydrothermal and reflux synthesized OMS-2 exhibited more ordered nanorod structure and higher crystallinity.The co-precipitation(C-OMS-2)and solid phase(S-OMS-2)methods synthesized OMS-2 exhibited the irregular nanoparticles.Moreover,different preparation methods of synthesizing OMS-2 have a significant effect on the chemical states of Mn and O over the final Pd/OMS-2 products.In the four different preparation methods,hydrothermal preparation of OMS-2 loads of Pd catalyst showed the best performance of CO catalytic oxidation.(2)To explore the effects of roasting temperature on the carrier,in this paper,Manganese oxide octahedral molecular sieves(OMS-2)synthesized from hydrothermal were roasted at 300 0C、400 ℃、500 ℃、600 ℃ respectively,and then impregnated with palladium and used for CO catalytic oxidation.The results showed that different roasting temperatures have a significant effect on the CO catalytic oxidation of catalysts at low temperature.The optimal Pd/H-OMS-2-500 catalyst exhibited over 90%of CO conversion at 20 ℃.The characterization results showed that the crystallization and the atomic concentration of Pd increased with the elevating temperature.When the sample is calcined at 600 ℃,the performance of CO catalytic oxidation obviously decreased due to the phase transformation of K2-xMn8O16.Pd/H-OMS-500 has good crystallinity,stable structure and show superior CO catalytic oxidation properties at ambinent temperature.