Ce-Fe/ZSM-5催化剂NH3选择性催化还原NO性能研究

Research on performance of Ce-Fe/ZSM-5 catalyst for selective catalytic reduction of NO with NH3

通过浸渍法将Ce和Fe负载在ZSM-5载体上,制备了1.40%Fe/ZSM-5(数字为金属组分的质量分数,下同)、0.25%Ce/ZSM-5、0.25%Ce-1.40%Fe/ZSM-5和0.50%Ce-1.40%Fe/ZSM-5催化剂。对催化剂进行了表征并研究了其NH3选择性催化还原(NH3-SCR)NO的性能。实验结果表明,双金属改性的0.25%Ce-1.40%Fe/ZSM-5催化剂的活性温度窗口范围最广,在350~450℃范围内NO转化率超过98%。Ce和Fe以无定型氧化物的形态良好分散在ZSM-5载体表面,没有改变ZSM-5分子筛的微孔结构。0.25%Ce-1.40%Fe/ZSM-5催化剂的有效还原峰面积更大,孤立Fe3+和Ce4+物种含量更多,氧化还原性能显著,催化剂表面具有丰富的中等强度酸性位且酸量较大,有利于NH3-SCR反应的进行。

Ce and Fe were loaded on carrier ZSM-5 prepared by impregnation method to preparea series of catalyst,such as:1.40%Fe/ZSM-5(number stands for mass fractionof metal component,the same below),0.25%Ce/ZSM-5,0.25%Ce-1.40%Fe/ZSM-5 and 0.50%Ce-1.40Fe/ZSM-5 catalyst.The catalysts were characterized and their activities for selective catalytic reduction of NO with NH3 were researched.The experimental results show that the bimetal-modified catalyst 0.25%Ce-1.40%Fe/ZSM-5 has the widest activation temperature range with which the NO conversion rate reaches 98%in the temperature range of 350-450℃.Ce and Fe are well dispersed on the surface of the ZSM-5 carrier in the form of amorphous oxide,so that the micropore structure of the ZSM-5 is not changed.The 0.25%Ce-1.40%Fe/ZSM-5 catalyst has a larger effective reduction peak area and more isolated Fe3+and Ce4+species,which indicate its significant redox performance.There are abundant medium-strength acid sites and a large amount of acid on the surface of the catalyst,which is favorable to the NH3-SCR reaction.