自蔓延燃烧法制备Pd_(0.01)Cu_(x)Ce_((1-x)/2)Zr_((1-x)/2)O_(y)催化剂催化NO制NH_(3)反应的性能研究

Catalytic Performance for the Reaction from NO to Ammonia of Pd_(0.01)Cu_(x)Ce_((1-x)/2)Zr_((1-x)/2)O_(y)Prepared by Self-Propagating High Temperature Synthesis

被动式氨SCR系统是一种应用在稀燃发动机,可减少NO_(x)排放,生产SCR用氨的后处理方法,该系统使用NO与H_(2)作为原料气在催化剂的作用下产生氨气用于后续SCR脱硝。通过试验研究,采用自蔓延燃烧合成(SHS)法合成了Pd_(0.01)Cu_(x)Ce_((1-x)/2)Zr_((1-x))/2 O_(y)(x=0,0.1,0.2,0.4)催化剂。用XRD、BET、Raman、H_(2)-TPR、XPS、原位表征等方法研究了它们的催化活性。建立了Pd_(0.01)Cu_(x)Ce_((1-x)/2)Zr_((1-x)/2)O_(y)(x=0,0.1,0.2,0.4)催化剂的反应性与物种组成、酸性质和氧化还原性能的关系。结果表明,适量的铜掺杂可以形成更多的酸性位点,调节表面元素的价态分布,有助于产生更高的催化效率。其中,Pd_(0.01)Cu_(0.1)Ce_(0.45)Zr_(0.45)O_(x)的氨转化率最高,反应温度窗口较宽(225~375℃),NO向NH_(3)转化率大于90%。这是由于高度分散的CuO增强了CuO与Ce_(0.5)Zr_(0.5)O_(2)载体之间的相互作用,从而提高了催化活性。

The passive ammonia SCR system is a novel aftertreatment method for lean-burn engine to reduce NO_(x)emission and produce necessary ammonia for SCR.The reaction between NO and H_(2)was activated and ammonia gas of SCR,denitration was then prepared under the action of a catalyst.Pd_(0.01)Cu_(x)Ce_((1-x)/2)Zr_((1-x)/2)O_(y)catalysts with x parameter of 0,0.1,0.2 and 0.4 were synthesized through self-propagating combustion reaction method.The activities of catalysts were investigated according to XRD,BET,Raman,H_(2)-TPR,XPS,in situ DRIFTS.The relationship between the catalyst reactivity and species composition,acid property,and redox behavior was established in the end.The results showed that a moderate amount of Cu doping could significantly form more acid sites and tune the valence distribution of surface elements so as to lead to a high catalytic efficiency.Pd_(0.01)Cu_(0.1)Ce_(0.45)Zr_(0.45)O_(x)had the highest ammonia conversion rate among all the catalysts with a wide reaction-temperature window of 225-375℃.The conversion rate of NO to NH_(3)was beyond 90%with the catalyst due to the improved catalytic activity led by the fact that highly-dispersed CuO enhanced the interaction between CuO and Ce_(0.5)Zr_(0.5)O_(2)carrier.