Novel NO trapping catalysts derived from Co-Mg/X-Al (X=Fe, Mn, Zr, La) hydrotalcite-like compounds.
Co(2.5)Mg(0.5)/Al1 and Co(2.5)Mg(0.5)/X(0.5)Al(0.5) hydrotalcite-like compounds (where X = Fe, Mn, Zr, La) were synthesized by a constant-pH coprecipitation. The derived oxides from hydrotalcites upon calcination at 800 degrees C for 4 h in static air are mainly of spinel phase, with a surface area of 14.2-23.8 m2/g, where new phase ZrO2 and La2O3 are segregated in Zr- and La-containing oxides, respectively. Incorporation of the fourth element has assisted the reduction of transition-metal cations in the oxide catalysts, which may lead to the enhancement of the NO storage capacity in O2 at 100 degrees C for all catalysts. However, at 300 degrees C, only Zr- and La-containing catalysts improve the NO storage performance. Substantially, La-containing catalyst excels over all other catalysts in NO storage capability both at 100 and 300 degrees C. More remarkably, the NO storage at 300 degrees C (7.56 mg/g) is much higher than that at 100 degrees C (4.69 mg/g). NO adsorption/desorption routes have been proposed to explain the NO storage, the NO-to-NO2 conversion, and the reduction (decomposition) of NO to N2O/N2 in O2 on the catalysts. In addition, the negative influences of CO2 or H2O on the NO storage/reduction have been further revealed in this research.
Yu
Jun Jie
JJ
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China.
Tao
Yan Xin
YX
Liu
Chang Chun
CC
Hao
Zheng Ping
ZP
Xu
Zhi Ping
ZP
D000327:Adsorption; D000393:Air Pollutants / Q000737:chemistry; D000536:Aluminum Hydroxide / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D002384:Catalysis; D008276:Magnesium Hydroxide / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D000393:Air Pollutants; D008670:Metals; D009589:Nitrogen Oxides; D014867:Water; D002245:Carbon Dioxide; C010467:hydrotalcite; D000536:Aluminum Hydroxide; D008276:Magnesium Hydroxide