Novel NO Trapping Catalysts Derived from Co−Mg/X−Al (X = Fe, Mn, Zr, La) Hydrotalcite-like Compounds

• Published in: Environmental science & technology 2007-02, Vol.41 (4), p.1399-1404
• Main Authors: Yu, Jun Jie, Tao, Yan Xin, Liu, Chang Chun, Hao, Zheng Ping, Xu, Zhi Ping
• Format: Article
• Language: English
• Subjects: Adsorption; Air Pollutants - chemistry; Aluminum Hydroxide - chemistry; Applied sciences; Atmospheric pollution; Carbon dioxide; Carbon Dioxide - chemistry; Catalysis; Catalysts; Catalysts: preparations and properties; Cations; Chemical compounds; Chemical engineering; Chemical reactions; Chemistry; Decomposition; Desorption; Exact sciences and technology; General and physical chemistry; Magnesium Hydroxide - chemistry; Metals; Metals - chemistry; Nitric oxide; Nitrogen Oxides - chemistry; Pollution; Prevention and purification methods; Q1; Storage; surface area; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Transports and other; Water - chemistry
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es061538t

Co2.5Mg0.5/Al1 and Co2.5Mg0.5/X0.5Al0.5 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 °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 °C for all catalysts. However, at 300 °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 °C. More remarkably, the NO storage at 300 °C (7.56 mg/g) is much higher than that at 100 °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.