负载型膨胀石墨催化剂低温催化氧化NO研究

Low-temperature catalyzed oxidation for NO supported by the expanded graphite catalyst

膨胀石墨(EG)具有四级孔结构,是一种优良的吸附剂和催化剂载体。采用超声浸渍法制备了Mn/EG催化剂,用于低温催化氧化NO,考察了金属负载量、进口NO质量浓度及O2体积分数对NO氧化效率的影响。结果表明,利用超声浸渍法制备得到的Mn/EG催化剂低温催化氧化活性较好,且催化剂表面的3价Mn对反应活性有重要影响。进口气体中O2体积分数对反应活性有明显的影响,低温时高体积分数的氧能促进NO的转化。150℃时,在NO体积分数为0.05%、O2体积分数为3%、空速为47 770 h-1的条件下,该催化剂的NO催化氧化效率可达42%。

The paper is engaged in a study of the characteristic features of the expandable graphite,which enjoys four levels of porous structure. As is well-known,graphite is a kind of new porous carbon-based excellent support for adsorbing material and catalysts. It is just based on the study of such a kind of absorption feature that we would like to manage to prepare the catalyst Mn /EG in the way of ultrasound-assisted impregnation and study the reaction of the low-temperature catalytic oxidation of NO. For the study purpose,we have taken into account a series of factors,including the metal loading and the impact of the NO concentration and content O2,on the NO oxidation efficiency through testing and analyzing a series of indexical factors. What is more,we have gained a lot of objective experimental findings and data needed for powerful description,which indicate that in the way of the ultrasound-assisted impregnation prepared catalyst Mn / EG enjoys highly reactive activity to the low-temperature catalytic oxidation.Furthermore,the experimental results also show that there exists an efficient method for improving the efficiency of the activated catalysis,that is to say,it can be doped with metal oxide into the EG. Moreover,the Mn3 ＋on the catalyst surface has been found functioning well on the reactivity. At the same time,the experiments we have done have also helped us to detect that NO conversion rate tends to increase with the rise of temperature. For example,when the reaction temperature reaches 150 ℃,it is possible for NO to display its best conversion rate. In addition,with the increase of NO concentration,catalyst oxidation tends to reveal a tendency of increase at first,and then tends to decrease when it reaches to a definite concentration rate. Besides,the oxygen content can also have a great potential effect on the reaction activity.For example,at low temperatures,the highly concentrated oxygen is in a position to promote the conversion of NO,whereas the O2 concentration of the imported gas has been found remarkably affecting the reactivity. For instance,at 100 ℃,under the conditions of the NO volume fraction 0. 05%,O23%,the space velocity can reach 47 770 h- 1,whereas the NO catalyzed oxidation efficiency can be made to reach as high as up to 42%.