压缩天然气(CNG)汽车因其良好的排放特性,正被越来越多的大型城市公交系统使用,但是汽油车辆用尾气净化催化剂对天然气汽车的主要烃类排放物甲烷转化效率低.针对天然气车辆排放物特点,设计了天然气汽车尾气净化催化剂,其成分包括稀土金属和过渡金属化合物、少量贵金属氧化物、结构稳定剂等.试验结果表明,在700℃以上,CO和CH4转化率达到98%以上,催化剂耐高温性能好,在1 000℃,1.5 h试验时间内HC和CO转化率达到99%,此外该催化剂具有一定的抗硫化物中毒能力.
Aiming at improving the air quality, more and more automobiles with compressed natural gas (CNG) fuel are being used in some big cities now. The three way catalysts (TWC) for gasoline cars are not suitable for CNG cars. In the exhaust gases from CNG cars, the hydrocarbon is mainly methane, which is converted into carbon dioxide quite difficultly compared with other hydrocarbons. In this paper, a specially designed catalyst dosage was developed, which contained lanthanide oxides, transition element oxides and a minor part of noble metal oxides. The catalysts can reach a high conversion ratio for the exhaust pollutants above 700℃. More than 98.0 per cent of CH4 and CO in CNG engine exhaust gases can be converted into CO2 and H2O. At 1 000℃, the catalyst maintains a 99.0 per cent conversion ratio for CH4 and CO in 1.5 h, showing a high thermal stability. A resistance to sulfur oxides was also behaved.
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