氧化共沉淀法制备Ce0.65Zr0.25Y0.1O1．95的结构转化过程

以氨水和碳酸铵为沉淀剂,采用氧化.共沉淀法制备了Ce0.65Zr0.25Y0.1O1.95复合氧化物,并对不同处理温度下制备的样品用热重.差示扫描分析(TG-DSC)、傅里叶变换红外(FT-IR)光谱、X射线衍射(XRD)和表面分析仪(BET)等进行了表征.结果表明,共沉淀法得到的沉淀物同时含有羟基和羧基,随着焙烧温度的升高,分别在100-170 ℃、250-300℃和420-500℃温度范围内先后发生脱水、脱羟基和脱羧基反应,在此过程中固溶体逐渐形成.提出了由沉淀物转变为Ce0.65Zr0.25Y0.1O1.95复合氧化物的结构转变模型.     

Y2O3和CeO2复合掺杂ZrO2纳米晶的制备与表征

以ZrOCl2.8H2O,Y2O3,Ce（NO3）3.5.5H2O为原料,NH3.H2O作沉淀剂,少量表面活性剂PE作分散剂,采用反向共沉淀-喷雾干燥法,结合物理、化学分散技术,成功地制备了Y2O3,CeO2复合掺杂ZrO2纳米粉末。通过DSC-TG,XRD,XPS,BET和SEM等方法对所制得粉末进行了表征。结果表明：以Ce0.1Y0.1Zr0.8O1.95化学计量比制备的多元氢氧化物胶体经过喷雾干燥处理后,在500℃基本完成水合氧化物的分解,577℃附近完成由非晶相向立方相的转变;经过580-1000℃煅烧后,CeO2和Y2O3已经完全固溶到ZrO2中,形成类质同相体,该粉末系列均属于立方相萤石结构;掺杂进入ZrO2晶格中的Ce呈＋4价形式存在;比表面积由22.0 m^2.g^-1（580℃煅烧）减至4.97 m^2.g^-1（1000℃煅烧）;SEM结果显示800℃煅烧的该粉末颗粒尺寸分布均匀,多呈类球状,且粒径在50-80 nm。     

Ce-Zr-O固溶体的制备和表征

采用硝酸盐直接分解法、共沉淀法、苹果酸溶胶 凝胶法和柠檬酸溶胶 凝胶法制备了Ce Zr O复合氧化物并进行了表征。溶胶 凝胶法制得的Ce Zr O为立方的Ce0 .5Zr0 .5O2 复合氧化物 (其中少量具有立方性质的t″相 ) ,而直接分解和共沉淀法制得的是由立方Ce0 .8Zr0 .2 O2 和四方Ce0 .2 Zr0 .8O2 固溶体组成的复合氧化物。不同制备方法制得的样品由于物相组成不同 ,还原性能也有较大差别。差热分析和X射线衍射分析结果表明 ,凝胶在燃烧的同时生成了Ce0 .5Zr0 .5O2 固溶体。     

Ce0.45Zr0.45Y0.07La0.03O1.95/La-Ba-Al2O3质量比对整体式铁基催化剂上稀薄甲烷燃烧的影响

采用共沉淀法和胶溶法分别制备了高性能的储氧材料Ce0.45Zr0.45Y0.07La0.03O1.95(OSM)和耐高温高比表面的La-Ba-Al2O3,并以它们为载体,制备了一系列整体式铁基催化剂.考察了该系列催化剂对甲烷稀薄燃烧的催化性能.并用低温N2吸附-脱附,储氧量(OSC)测试,X射线衍射(XRD)和H2程序升温还原(H2-TPR)等测试手段考察了不同Ce0.45Zr0.45Y0.07La0.03O1.95/La-Ba-Al2O3质量比对催化剂特性的影响.活性测试结果表明,当Ce0.45Zr0.45Y0.07La0.03O1.95/La-Ba-Al2O3质量比为1:1时新鲜和老化催化剂的活性均最好,新鲜催化剂可在50000h-1的高空速条件下使含量为1%(体积分数)的甲烷在446℃起燃,553℃完全转化;低温氮气吸附-脱附测试结果和H2-TPR表明,不同的Ce0.45Zr0.45Y0.07La0.03O1.95/La-Ba-Al2O3质量比使催化剂表现出不同的织构性能和还原性能;XRD测试结果表明,OSM以均一固溶体存在,Fe高度分散在载体上.综合以上表征手段得出:合适的Ce0.45Zr0.45Y0.07La0.03O1.95/La-Ba-Al2O3质量比导致催化剂具有优异的稀薄甲烷催化燃烧活性和热稳定性.     

铋杂对Ce-Zr固溶体储氧性能稳定性的影响

以Ce(NO3)3·6H2O,ZrO(NO3)2·2H2O和Bi(NO3)3·5H2O为原料,氨水为沉淀剂,双氧水为氧化剂,在pH值为9.5～10.5条件下,采用氧化共沉淀法制备了不同比例组成的复合氧化物Ce1-x-yZrxBiyOσ.通过XRD,BET和Raman表征可知,该法制备的样品550 ℃焙烧后均可形成固溶体,当x0.15,y0.2时,高温焙烧后易分相.H2-TPR和CO脉冲测试结果显示Ce0.65Zr0.15Bi0.2Oσ较易被还原,且1050℃焙烧4 h后储氧量仍可达625 μmol·(g cat)-1,这是由于Bi3+取代了Ce0.65Zr0.15Bi0.2Oσ中部分Ce4+和Zr4+形成氧空位,增强了体相晶格氧的移动性,从而使Ce0.65Zr0.15Bi0.2Oσ固溶体中的Ce4+和Bi3+同时被还原.     

铋掺杂对Ce-Zr固溶体储氧性能稳定性的影响

以Ce(NO3)3.6H2O,ZrO(NO3)2.2H2O和Bi(NO3)3.5H2O为原料,氨水为沉淀剂,双氧水为氧化剂,在pH值为9.5~10.5条件下,采用氧化共沉淀法制备了不同比例组成的复合氧化物Ce1-x-yZrxBiyOσ。通过XRD,BET和Raman表征可知,该法制备的样品550℃焙烧后均可形成固溶体,当x0.15,y0.2时,高温焙烧后易分相。H2-TPR和CO脉冲测试结果显示Ce0.65Zr0.15Bi0.2Oσ较易被还原,且1050℃焙烧4 h后储氧量仍可达625μmo.l(g cat)-1,这是由于Bi3+取代了Ce0.65Zr0.15Bi0.2Oσ中部分Ce4+和Zr4+形成氧空位,增强了体相晶格氧的移动性,从而使Ce0.65Zr0.15Bi0.2Oσ固溶体中的Ce4+和Bi3+同时被还原。     

铈基复合氧化物的结构及其对HCl催化氧化性能的影响

采用氨水共沉淀法制备了一系列铈基复合氧化物(Ce0.9M0.1O2,M=Cu、Cr、Zr、Ti、La),借助XRD、Raman、N2吸附-脱附、ESEM和H2-TPR等手段对复合氧化物的结构进行了表征,并考察了其在HCl催化氧化制Cl2过程中的性能.结果显示:Cu、Cr和Zr掺杂能显著减小复合氧化物晶粒尺寸,提高复合氧化物的比表面积和孔容,并提供更多的低温可还原氧物种.而La和Ti的掺杂可以获得较大的表面氧空位浓度以及增加高温可还原氧物种数目.复合氧化物结构和表面性质的变化显著影响了其HCl催化氧化活性,在430℃下铈基复合氧化物催化剂活性顺序为:Ce0.9Cu0.1O2Ce0.9Cr0.1O2Ce0.9Zr0.1O2Ce0.9Ti0.1O2Ce O2Ce0.9La0.1O2,低温可还原氧物种数目直接与催化剂活性有关.反应动力学测试显示催化剂低温可还原氧物种有利于HCl在催化剂表面的吸附和活化,而催化剂表面的氧空位可以促进氧分子的吸附和活化.     

制备方法对Ce0.6Zr0.3Pr0.1O2纳米复合氧化物性能的影响

采用室温共沉淀、分步沉淀和共沉淀、分步沉淀水热法制备了Ce0.6Zr0.3Pr0.1O2纳米复合氧化物。X射线衍射(XRD)、N2物理吸附、透射电镜(TEM)、H2程序升温还原(H2-TPR)和热重分析技术(TG)表征结果表明:分步沉淀水热法有利于锆离子和镨离子进入CeO2晶格和提高Ce0.6Zr0.3Pr0.1O2纳米复合氧化物的热稳定性、氧化还原性能和储释氧性能。制备过程中未加入任何表面活性剂,1000℃焙烧4 h后,其晶粒尺寸可控制在8~15 nm,比表面积仍能保持在66 m2·g-1,释氧量维持在1713μmol[O]·g-1CeO2。     

不同沉淀剂对Ce0.65Zr0.35O2复合氧化物性能的影响

本文选用不同沉淀剂,用共沉淀法制备了稀土储氧材料Ce0.65Zr0.35O2复合氧化物,对用不同沉淀剂制备出的氧化物样品进行了XRD,BET,OSC和H2-TPR的测试和分析。结果表明,用不同沉淀剂制备出的氧化物,均为立方相的铈锆固溶体,经1000℃5小时老化后也无相的分离;以(NH4)2CO3和NH3.H2O的混合物为沉淀剂制备出的氧化物有最大的比表面积,经600℃焙烧后高达120m2/g以上;并且样品具有良好的储氧性能及低温还原能力。     

Ce0.35Zr0.55La0.10O1.95对低贵金属Pt-Rh型三效催化剂性能的影响

采用共沉淀技术制备了Ce0.35Zr0.55La0.10O1.95固溶体, 其织构和结构性能以及氧化还原性能分别采用BET、XRD和程序升温(TP)技术进行了表征. 制备了低贵金属Pt-Rh型三效催化剂, 考察了Ce0.35Zr0.55La0.10O1.95对催化剂性能的影响. XRD和BET的结果表明, 经600 ℃焙烧5 h后, Ce0.35Zr0.55La0.10O1.95具有与Ce0.50Zr0.50O2相似的立方结构和高的比表面积；经1000 ℃焙烧5 h后, 仍能保持稳定的立方结构和47.25 m2•g−1的比表面积, 表现出优越的织构性能和高的热稳定性. H2-TPR和O2-TPO的结果表明, Ce0.35Zr0.55La0.10O1.95具有比Ce0.50Zr0.50O2更好的氧化还原性能. 和含Ce0.50Zr0.50O2的催化剂相比, 含Ce0.35Zr0.55La0.10O1.95的催化剂具有较宽的工作窗口, 优越的低温起燃性能, 较强的水气变换能力；催化剂经1000 ℃高温水热老化5 h后, 仍具有良好的催化活性, 表现出了优异的抗老化性能.     

Structure Evolution Process of Ce0.65Zr0.25Y0.1O1.95 Prepared by Oxidation-Coprecipitation Method

Ce_0.65Zr_0.25Y_0.1O_1.95 oxides were prepared by oxidation-coprecipitation method using ammonia and salvolatile as precipitators. The as-prepared samples were thermally treated at different temperatures and characterized by thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform-infrared (FT-IR) spectrometry, X-ray diffraction (XRD), and specific surface area measurements (BET). The results showed that the hydroxyl and carboxyl groups coexisted in the precipitate and a perfect solid solution was gradually formed with an increase in calcination temperature. The physisorbed water was lost from 100 to 170 °C, hydroxyl groups were removed from 250 to 300 °C, and the carboxyl groups were eliminated from 420 to 500 °C. A structure model was further proposed to understand the Ce_0.65Zr_0.25Y_0.1O_1.95 structure evolution process in depth.     

固体电解质Ce_(0.9)Er_(0.1-x)Pr_xO_(1.95+δ)的微观结构及电性能

采用柠檬酸溶胶-凝胶法制备了固体电解质Ce0.9Er0.1-xPrxO1.95+δ(x=0.02~0.08),利用X射线粉末衍射(XRD)、原子力显微镜(AFM)、拉曼光谱(Raman)、X射线光电子能谱(XPS)和交流阻抗谱研究了样品的微观结构和电性能.XRD结果表明,800℃煅烧的所有样品均形成了单相立方萤石结构;Raman光谱结果表明,Ce0.9Er0.05Pr0.05O1.95+δ具有氧缺位的立方萤石结构;XPS分析表明,Ce0.9Er0.05Pr0.05O1.95+δ存在氧缺位,Pr3+离子和Pr4+离子共存;AFM观测结果表明,1300℃下烧结的样品比1400℃下烧结的样品致密;交流阻抗谱结果表明,Pr掺杂量x=0.05时,Ce0.9Er0.05Pr0.05O1.95+δ的电导率最高(σ600℃=1.34×10-2S/cm,Ea=0.90 e V),比未掺杂Pr的Ce0.9Er0.1O1.95(σ600℃=8.81×10-3S/cm,Ea=0.92 e V)提高了52%,说明在Ce0.9Er0.1O1.95中适量掺杂Pr可提高材料的电导率,降低活化能.     

MnOx/Al2O3/Ce0.45Zr0.45M0.10Oy （M = Mn, Y, La） catalysts used for ethanol catalytic combustion

MnOx/Al2O3/Ce0.45Zr0.45M0.10Oy (M = Mn,Y,La) catalysts were prepared by impregnation method and characterized by BET,TPR and XRD analyses.The catalytic activities toward ethanol combustion were investigated in a microreactor.The results demonstrated that the catalytic activity of MnOx/Al2O3/Ce0.50Zr0.50O2 monolithic catalyst could be improved by doping Mn,Y and La into Ce0.50Zr0.50O2.When doping Y into Ce0.50Zr0.50O2,the catalyst MnOx/Al2O3/Ce0.45Zr0.45Y0.10O1.95 showed the highest activity.The 100% conversion temperature of ethanol was 230 ℃.Furthermore,once the conversion of ethanol started,the complete conversion was quickly achieved.The doping of Mn,Y and La led to better activity for ethanol combustion and lower temperature reduction peaks in TPR profiles.The doping of Mn resulted in enhanced oxygen storage capacity (OSC),larger area of the reduction peaks,and excellent reactivity,and the doping of Y resulted in the lowest reduction temperature and the best activity.     

铈锆摩尔比对Ce0.3+xZr0.6-xY0.1O1.95系列储氧材料性能的影响

研究了铈锆摩尔比对Ce0.3+xZr0.6-xY0.1O1.95系列储氧材料性能的影响, 得到了一些有意义的结果.     

Doping of Ceria-Zirconia Solid Solution with Rare-earth Elements

The increasingly restrictive regulations on car exhaust emissions will necessitate the development of a new generation of three way catalysts (TWC) with better performance1. Ceria (CeO2) is the main component of the current TWC: its key role is to compensate the fluctuations in the exhaust stream composition, therefore, allowing to expand the air/fuel(A/F) operating window of catalytic converters2. This property is related to its oxygen storage capacity (OSC), associated to the redox couple Ce4+/Ce3+. However, CeO2 alone is easy to sinter to lost OSC at high temperature3.Ceria-zirconia (CexZr1-xO2) solid solutions by incorporation of Zr4+ in the CeO2 lattice have enhanced OSC and greater thermal stability, which are becoming the key materials for the new generation of TWC4. OSC of ceria-zirconia solid solutions can be further improved by the addition of M3+ dopants5. Besides Ce, other rare-earth elements such as Pr and Tb can vary their oxidation state. Pr and Tb are particularly suitable for making solid solutions with cerium because the known structure of PrO2 and TbO2 is of the cubic fluorite type, and the ionic radii of Pr4+ and Tb4+ are close to that of Ce4+6.In this paper, Ce0.6Zr0.3M0.1O2 (M=Y, La, Pr, Tb) were prepared by co-precipitation technique and characterized by a series of methods. Meanwhile, palladium-only TWCs were prepared by slurry coating and their catalytic activity was evaluated under the condition of simulated exhaust in the lab.XRD and FT-Raman spectra results show Ce0.6Zr0.3M0.1O2 have cubic fluorite structure which keep unchanging at high temperature. The different dopant ion radii brought different effect on the cell parameter of Ce0.6Zr0.3M0.1O2. The X-ray photoelectron spectroscopy (XPS) results show that the binding energy of Ce3d, Zr3d and O1s for Ce0.6Zr0.3M0.1O2 rose compared with that for Ce0.6Zr0.4O2, indicating dopant elements changed chemistry environment of solid solutions which was available to improve redox performance From TPR results, doping La can not change redox performance of solid solution, but doping Y decreased reduction temperature. Doping Pr and Tb notably improved redox performance of solid solutions due to appearance of low-temperature reduction peak in TPR profile which come from mobility of bulk oxygen.Compared with Pd/Ce0.6Zr0.4O2, doping Y and La unchanged A/F characteristic of TWCs, but doping Pr and Tb widen A/ F operating window and make HC, CO and NO have higher conversion.The light-off temperature of Pd/Ce0.6Zr0.3La0.1O2 was corresponded to that of Pd/Ce0.6Zr0.4O2.However, the light-off temperatures of Pd/Ce0.6Zr0.3M0.1O2 (M=Y, Pr, Tb) were lower than that of Pd/Ce0.6Zr0.4O2, which kept much lower after high temperature treatments. Among Pd/Ce0.6Zr0.3M0.1O2 (M=Y, La, Pr, Tb), Pd/Ce0.6Zr0.3Tb0.1O2 showed wider A/F operating window,higher conversion, lower light-off temperature and better high-temperature resistance     

Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce0.2Zr0.1Al0.7Oδ Catalyst

The transition metals (Cu, Co, and Fe) were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst.The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS.Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals (Cu and Co) significantly increased the activity of catalyst under the conditions of lower reaction temperature,and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts.Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ.     

CexZr1-xO2/Co/C-N催化CO2加氢性能研究

将不同比例的铈锆前驱体负载到ZIF-67,氮气气氛焙烧制备CexZr1-xO2/Co/C-N催化剂,对催化剂进行了XRD,H2-TPR、XPS表征,并在固定床反应器评价其CO2加氢制甲醇性能。XRD结果表明,在铈中加入适量锆形成铈锆固溶体,铈锆固溶体与钴物种较强的相互作用力可以阻止表明金属Co的氧化。但过量加入的锆又会削弱这一作用力,部分金属Co被氧化为Co3O4。H2-TPR结果表明适量的锆的加入改善催化剂的还原性能,催化剂还原温度降低。XPS证实了25%Ce0.67Zr0.33O2/Co/C-N催化剂中含有更多的氧空穴及氮含量,氧空穴和碱性氮都有利于CO2的解离吸附。优化后的25%Ce0.67Zr0.33O2/Co/C-N 催化剂在225 oC,2 MPa,GHSV = 6 L/gcat/h反应条件下取得最高甲醇时空收率,为3.0 mmol/gcat/h。     

Pt/γ-Al2O3/CexZr1-xO2催化剂低温催化燃烧去除饮食油烟

以CexZr1-xO2固溶体做载体, 制备了系列Pt/γ-Al2O3/CexZr1-xO2催化剂(x=1, 0.75, 0.5, 0.25, 0). 应用Brunauer-Emmet-Teller (BET)比表面积分析、X射线衍射(XRD)和H2程序升温还原(H2-TPR)等手段对催化剂进行相关表征, 并系统研究了催化剂在饮食油烟催化燃烧中的催化活性. BET结果表明催化剂的比表面积随Ce/Zr摩尔比的减小而减小. XRD结果表明贵金属Pt很好地分散在氧化铝和CexZr1-xO2固溶体上. H2-TPR结果发现催化剂Pt/γ-Al2O3/Ce0.5Zr0.5O2的还原峰面积最大且氧离子的流动性最好. 催化活性研究结果表明Pt负载在CexZr1-xO2固溶体上有利于油烟的催化燃烧, 降低了反应温度. 随着CexZr1-xO2固溶体中Ce/Zr摩尔比的变化, 催化剂的活性顺序为Pt/γ-Al2O3/Ce0.5Zr0.5O2>Pt/γ-Al2O3/Ce0.25Zr0.75O2>Pt/γ-Al2O3/Ce0.75Zr0.25O2>Pt/γ-Al2O3/CeO2>Pt/γ-Al2O3/ZrO2.