稀土基汽车尾气催化剂的研究Ⅰ:催化剂老化和SO_2添加对催化活性的影响

制备了低Pt、Rh担载量的稀土基催化剂体系 ,研究了贵金属担载量、催化剂高温老化、抗硫水热老化和SO2 对催化活性的影响。结果表明 :随着贵金属质量分数从 0 2 5 %降低到0 1% ,CO、碳氢化合物 (HC)和NO的起燃温度分别平均提高 2 0℃ ;随着m(Pt)∶m(Rh)从 5∶1提高到 9∶1,CO、HC和NO的起燃温度分别提高 17、2 0和 5 3℃ ;当在反应体系中添加SO2 ,随SO2 体积分数从 0 0 0 2 %增加到 0 0 1% ,CO和NO的起燃温度和完全转化温度分别平均提高2 0℃ ,而对于HC ,催化活性几乎保持不变 ;催化剂在水热含硫条件下连续老化 4 0 0h ,CO、NO和HC的起燃温度分别为 2 5 2、2 6 7和 30 3℃ ,仍具有良好的反应活性。表明该稀土基催化剂在一定条件下 ,能满足汽车实际工况的要求

Three-way Catalyst for Emission Control with Low Platinum/Rhodium LoadingⅠ:The Effect of Aging and SO2 Addition on Catalytic Activity

For the catalyst with low platinum/rhodium loading,the impact of decreasing the amount of precious metal on catalytic activity is studied by aging and sulfur dioxide poisoning experiments.The light off temperature for CO,HC and NO increases by 20 ℃ in average with decrease of the mass fraction of Pt/Rh loading from 0 25% to 0 10%.When the ratio of m (Pt)∶ m (Rh) increases from 5∶1 to 9∶1,the light off temperature for HC,CO and NO increases by 17,20 and 53 ℃ respectively.An increase of SO 2 addition in the feed from 0 002% to 0 01% leads to an average increase of 20 ℃ for light off temperature and dynamic temperature of CO and NO,while nearly no change is observed for HC.After the catalyst is subjected in 12% H 2O(g) and 0 006% SO 2 at 900 ℃ and continuously aged for 400 h,the catalyst still reveals good activity.It indicates that the catalyst can partially meet the need of application.