Investigation Of Preparation Method Of LNT Catalysts Based On Doped Hydrotalcites Derived Oxides And Their Adsorption-reduction Performance With NO

NO_x is one of the most important pollutant emitted from diesel engine,and the Lean NO_x Trap technology is the most potential aftertreatment technology to reduce the emission of NO_x.The traditional LNT catalyst take the BaO as the adsorbent,but it performs not well under low temperature conditions causing that the reduction of NO_x catalyzed by traditional catalyst is worse.The new adsorbents with high performance have been hot spot of research.The author prepared the Mg-Al?Cu-Al?Co-Al?Ni-Al hydrotalcite catalysts by co-precipitation method.Meanwhile,another two series of catalysts Pt/Cu-Mg-Al-O,Pt/BaO/Cu-Mg-Al-O with different Cu doped were prepared by co-precipitation and impregnation methods.The author also explored the crystal structure,micro-morphology,the NO adsorption and desorption performance and the catalytic performance with several advanced technologies.This paper's researching results can supply the reference for developing environment-friendly catalysts.The main research result was showed as follow:The LNT catalyst based on hydrotalcite which was modified by transition metal can be prepared by co-precipitation method.But the replacement of Cu will make the structure less stable and damages the perfection of the crystal structure.The catalysts can be loaded with Pt and BaO evenly by impregnation method.Meanwhile the doped Cu can be scattered in mixed metal oxides.The modified hydrotalcite catalyst M-Al(M=Co,Cu,Ni)'s NO desorption quantity are less than Mg-Al hydrotalcite's.The replacement of Cu,Co,Ni can lower the stability of adsorbed nitrate.It is actually meaningful to improve the NO_x removing efficiency under low temperature.Compared with others,the Cu-Al hydrotalcite catalyst has better performance and need to be continued to research on.The loading of BaO improves the desorption starting temperature of LNT catalysts based on hydrotalcites,that approaches the traditional LNT catalyst.Meanwhile,the loading of BaO restrains the change from the nitrite to nitrate caused by the variation of Cu content.The result is that the bigger portion of absorbed NO exists as nitrite.In addition,the loading of BaO can improve the NO adsorption quantity.Under the alternative reaction mode between adsorption and reaction,The catalysts of 20% Cu content with the loading of BaO or not both can make the NO reduction efficiency up to 90% with H2 as the reductant in the simulated LNT reactions.