聚乙二醇辅助Ce_(0.6)Mn_(0.4)O_(x)催化净化碳烟颗粒物燃烧性能的研究

Combustion performance of polyethylene glycol-assisted Ce_(0.6)Mn_(0.4)O_(x) catalytic purification of soot

以进一步提升具有良好碳烟催化燃烧性能的Ce_(0.6)Mr_(0.4)O_(x)催化剂活性为目的,通过共沉淀法制备该催化剂时加入不同分子量的聚乙二醇(PEG).活性测试结果表明,随着PEG分子量的增加,活性先升高后降低.当PEG分子量为6000时,活性最佳,相比未添加PEG的铈锰混合氧化物催化剂,DSC曲线上燃烧最大值对应温度下降了23℃.XRD和Raman测试结果表明,该系列催化剂均形成了立方萤石结构.当添加分子量为6000的PEG时,结合XRD、Raman、XPS、ICP、H_(2)-TPR和O_(2)-TPD结果表明,此时Mn^(x+)进入CeO_(2)晶格中的量最大,从而产生了更多的表面活性氧,促进了表面化学吸附氧的脱附,表现出了良好的低温还原性能;BET结果表明,该催化剂的比表面积和孔容均优于未添加PEG的催化剂;SEM结果表明,该催化剂在微米和纳米层面均表现出更多的空隙.因此,添加分子量为6000的PEG最有利于促进碳烟催化燃烧.

In this study,a series of Ce_(0.6)Mr_(0.4)O_(x) catalysts were synthesized by coprecipitation method,and during the process polyethylene glycol(PEG)with different molecular weight was added for the purpose of achieving advanced soot catalytic combustion performance.The results of activity test show that with the increase of molecular weight of PEG,the activity increases at first and then decreases.When the molecular weight of PEG is 6000,the corresponding catalyst exhibits best activity.Compared with the blank sample,the maximum combustion temperature on the DSC curve decreases by 23℃.The results of XRD and Raman show that the series of catalysts all have cubic fluorite structure.When PEG with molecular weight of 6000 is added,the results of XRD,Raman,XPS,ICP,H_(2)-TPR and O_(2)-TPD show that largest amount of Mn^(x+)has entered into the CeO_(2) lattice,resulting in the generation of more surface reactive oxygen species,which can promote the desorption of surface chemically adsorbed oxygen,and consequently gives rise to prominent low temperature reduction performance of the catalyst.The BET results show that the specific surface area and pore volume of the catalyst are better than those of the catalyst without PEG.SEM results show that the catalyst exhibits more voids in both micron and nanometer layers.Therefore,the addition of PEG with molecular weight of 6000 is most beneficial to promote soot catalytic combustion of Ce_(0.6)Mr_(0.4)O_(x).