文献类型：期刊文献

中文题名：反应气氛对负载Pd催化剂上CO氧化和C_(3)H_(8)燃烧反应的影响

英文题名：Catalytic Performance for CO Oxidation and C_(3)H_(8)Combustion of Pd-Based Catalyst by Reaction Atmosphere

作者：姜枫妮[1];侯超[1];葛沙沙[1];王丽[1];郭耘[1]

机构：[1]华东理工大学化学与分子工程学院工业催化研究所,上海200030

年份：2021

卷号：45

期号：12

起止页码：1409

中文期刊名：稀有金属

外文期刊名：Chinese Journal of Rare Metals

收录：CSTPCD;;EI(收录号：20220711635112);Scopus;北大核心:【北大核心2020】；CSCD:【CSCD2021_2022】；

基金：国家重点研发计划项目(2016YFC0204300)资助

语种：中文

中文关键词：汽车尾气净化;Pd催化剂;CO氧化;C_(3)H_(8)燃烧;NO_(x)

外文关键词：automobile exhaust control;Pd based catalyst;CO oxidation;C_(3)H_(8)combustion;NO_(x)

摘要：采用浸渍法制备负载Pd催化剂,并考察载体(氧化铝、铈锆复合氧化物和铈锆铝复合氧化物)以及反应气氛对其催化CO氧化和C_(3)H_(8)燃烧反应性能的影响。通过X射线晶体衍射(XRD)、氢气程序升温还原(H_(2)-TPR)、NO程序升温脱附(NO-TPD)以及原位红外(in-situ DRIFTS)等手段对催化剂进行表征。研究发现PdO是C_(3)H_(8)催化燃烧反应的活性中心,而高价态的Pd^(n+)物种则更有利于CO氧化反应的进行。反应气氛的不同会影响催化剂对CO氧化和C_(3)H_(8)燃烧的反应性能,H_(2)O对于CO氧化反应起促进作用是由于在反应过程中H_(2)O起到氧化剂的作用;而对C_(3)H_(8)燃烧起抑制作用是由于H_(2)O抑制了C_(3)H_(8)的吸附和活化。当在反应气氛中引入NO时,对CO氧化和C_(3)H_(8)燃烧均起抑制作用,由于NO会和CO或者C_(3)H_(8)在活性中心发生竞争吸附,从而不利于反应物的吸附和活化。NO对C_(3)H_(8)燃烧反应的起燃温度影响较大,而对转化率达90%对应的温度影响不大。与C_(3)H_(8)燃烧反应性比,NO对CO氧化反应的影响更为显著。
With the development of our society and improvement of our life,the car ownership increased a lot.However,it was wellknown that CO and hydrocarbons(HCs)were the two main pollutants of automobile exhaust.It had long been recognized that 80%~90%hydrocarbon emissions from automobiles occurred during cold start.CO and HCs not only polluted the environment but had significant harmful effects on human being.CO was easy to bind with human hemoglobin,resulting in hypoxia,dizziness,headache and even life danger of human.Hydrocarbon was easy to produce photochemical smog in sunlight.Therefore,great effort and attentions were still needed to solve these pollutants.Until now,various types of catalysts had been investigated with the aim to control those exhaust pollutions.Among them,Pd-supported catalysts were widely accepted as catalysts with good catalytic oxidation activity of CO and HCs.However,the unambiguous understanding of the relationship between the catalytic activities of the Pd–supported catalysts and their supports as well as the reaction atmosphere was still a significantly challenge.In practical,pollutants contained in automobile exhaust were CO,NO,CHs,CO_(2)and H_(2)O.With the help of catalysts,they might interact with each other alternately.As we all know,the presence of water vapor would lead to steam reforming reaction and water gas conversion reaction.In order to guide the functional design of catalysts,it was significantly important to study the interaction of each component in automobile exhaust gas.In this work,the impregnation method was applied to prepare Pd-supported catalysts.The effects of supports(aluminium oxide,cerium zirconium composite oxides,and cerium zirconium aluminum composite oxides)and reaction atmosphere(NO and H_(2)O)on the catalytic performance for CO oxidation and C_(3)H_(8)combustion were investigated.Inductively coupled plasma atomic emission spectrometer(ICPAES),X-ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),NO-temperature programmed desorption(NOTPD),X-ray photoelectron spectroscopy(XPS)and in situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS)were used to characterize the catalysts.The results showed that the interactions between the carriers and Pd had an obvious effect on the existence of Pd species;therefore,it influenced the activity of the catalysts for CO oxidation and C_(3)H_(8)combustion.Pd with high valence(Pd^(n+))was found to be the active site for the CO oxidation reaction while PdO was the active site of C_(3)H_(8)combustion,therefore,Pd/CZ with the highest Pd^(2+)content tested by the XPS and H_(2)-TPR showed the best C_(3)H_(8)combustion activity.T_(90)(the temperature of 90%CO conversion)for the C_(3)H_(8)combustion reaction of Pd/CZ was 290℃while it was about 320 and 340℃for Pd/LA and Pd/CZA respectively.Different reaction atmospheres had obvious effects on catalytic performance for CO oxidation and C_(3)H_(8)combustion with Pd-supported catalysts.The effects of the usual component including H_(2)O and NO in automobile exhaust on the CO oxidation and C_(3)H_(8)combustion were analyzed.The presence of H_(2)O promoted CO oxidation;as a result,T90 for the catalysts(Pd/LA,Pd/CZ and Pd/CZA)was reduced about 10℃.It was due to the oxidability of H_(2)O which could not only oxidize the reactants but the carriers when they lost their lattice oxygen.On the contrary,the introduction of H_(2)O had a prohibitive effect on C_(3)H_(8)combustion.T;for the Pd/LA,Pd/CZ and Pd/CZA catalysts of C_(3)H_(8)oxidation increased about 52,45 and 35℃respectively.It was attributed to the inhibition of H_(2)O that weakened the adsorption and activation of methane on the catalysts.In addition,the side reaction of steam reforming reaction was improved for the existence of H_(2)O,therefore,the main reaction of the combustion of C_(3)H_(8)was inhibited.What’s more,the introduction of NO was harmful for the CO oxidation and C_(3)H_(8)combustion.The results characterized by NO-TPD and in-situ DRIFTS suggested that this was due to the competitive adsorption of NO and reactants(CO or C_(3)H_(8))on the active site surface,which was not conducive to the activation of reactants,therefore,the catalytic activity of the catalysts decreased a lot.Compared with C_(3)H_(8)combustion reaction,NO exhibited stronger inhibition effect on CO oxidation reaction.It thanked to the higher ignition temperature of C_(3)H_(8)combustion than that of the CO oxidation.The NO absorbed on the surface of catalysts desorbed a lot before the combustion of C_(3)H_(8),therefore,more active adsorption sites were exposed.Compared with C_(3)H_(8)combustion,the introduction of NO had more adverse effect on CO oxidation.Furthermore,the presence of NO had negative effect on the light-off temperature of C_(3)H_(8)combustion while it almost had negligible effect on the temperature corresponding to the conversion of 90%.In summary,this novel study showed the interaction between components of automobile exhaust gas and analyzed the active site of Pd species for CO oxidation and C_(3)H_(8)combustion,therefore,it would be a good guidance for the design of catalysts for the two reactions.