硫中毒对Co_3O_4/CeO_2 复合氧化物上炭黑催化燃烧的影响（英文）

采用共沉淀法制备了CeO2,Co3O4和一系列Co3O4/CeO2复合氧化物催化剂,在400°C下含SO2的氧化气氛中对催化剂进行了硫中毒处理,通过原位红外光谱、X射线衍射、程序升温脱附和X射线光电子能谱对新鲜和硫中毒的样品进行了表征.结果表明,所有测试的硫中毒样品上均形成了硫酸盐,CeO2上累积的硫酸盐明显比Co3O4上的多,Co3O4/CeO2复合氧化物在硫中毒过程中形成了硫酸钴和硫酸铈.对新鲜和硫化样品在NO/O2气氛下进行了催化炭黑燃烧实验,发现Co3O4/CeO2复合氧化物的活性和抗硫性能优于CeO2,但抗硫性能低于Co3O4.     

Co3O4/CeO2的氧化还原性能及反应条件对其CO氧化活性的影响

采用沉淀氧化法制备了Co₃O₄/CeO₂催化剂。运用XRD、BET和TPR表征手段,考察了不同钴铈比及焙烧温度对钴铈复合氧化物物理及化学性能的影响,并分别在干、湿条件下进行了一氧化碳氧化反应研究。结果表明,与纯的Co₃O₄相比,在不同比例的Co₃O₄/CeO₂均经723 K焙烧的各种催化剂中,钴铈原子比为9∶1的复合氧化物粒径较小,比表面积较大,说明适当比例铈的添加能使Co₃O₄具有较小的粒径。此氧化物经538 K温度焙烧制得的钴铈比为9∶1的复合氧化物中Co₃O₄平均粒径为7.2 nm, BET比表面积为167.6 m²/g。经TPR考察发现其具有最优的氧化还原性能。     

SiO2-CeO2复合氧化物的制备及抛光性能

采用正硅酸乙酯溶胶-凝胶法制备纳米SiO₂，并与氯化铈溶液混合，用氨水沉淀法制备了SiO₂-CeO₂复合氧化物。利用XRD、SEM等手段对其物相类型、外观形貌、颗粒大小、表面电位等物理性能进行了表征，测定了它们对3种光学玻璃的抛光速率。结果表明：合成复合氧化物具有立方萤石型结构，由Sherrer方程计算的晶粒D_XRD(200)小于100 nm甚至10 nm。随着SiO₂复配量的增加和煅烧温度的降低，晶粒度减小，比表面增大；激光粒度分析仪测定的中位粒径D₅₀在2～3 μm之间，且随SiO₂复配量的增加呈增大趋势，但随煅烧温度的变化在800 ℃时出现极小值，而此时的ζ电位的负值最大，对3种玻璃的抛光速率也最大。证明抛光速率与表面电位及相应的悬浮性、颗粒大小有直接关系。随着SiO₂复配量的增加，复合氧化物的ζ电位负值及对3种玻璃的抛光速率均增大。因此，在CeO₂中复配SiO₂是提高抛光速率的有效方法，此时，最佳的煅烧温度为800 ℃。     

纳米片聚结Co3O4微球催化甲苯燃烧

采用乙二胺辅助的水热法制备了纳米片聚结的Co₃O₄微球. 利用多种分析技术表征了其物化性质,并评价了其对甲苯燃烧的催化活性. 结果表明,由添加1.0 ml乙二胺经140 ℃水热处理12 h后制得的Co₃O₄样品呈纳米片聚结的微球状表面形貌. Co₃O₄微球样品的比表面积约为66 m² g^-1. 与体相Co₃O₄样品相比,Co₃O₄微球样品具有较高的氧吸附物种浓度和较好的低温还原性. 当空速为20000 ml g^-1 h^-1时,在Co₃O₄微球样品上甲苯转化率达到50%和90%时的反应温度分别为230和254 ℃. 这与该样品具有较大的比表面积、较高的氧吸附物种浓度和较好的低温还原性相关.     

CeO2-Al2O3负载金催化剂用于水煤气变换反应的催化活性

采用浸渍法和沉积 沉淀法制备了CeO₂-Al₂O₃复合氧化物,比较了复合氧化物负载纳米金催化剂对水煤气变换反应的催化活性。通过N2物理吸附、XRD、TEM、H₂-TPR等表征手段对复合氧化物及其负载金催化剂的物相和结构进行分析,发现复合氧化物的制备方法及其焙烧温度对其比表面积、孔结构及水煤气变换反应活性有明显的影响。与沉积 沉淀法相比,浸渍法制备的CeO₂-Al₂O₃复合氧化物具有较大的CeO₂晶粒尺寸,经500℃焙烧后再负载金,所得催化剂具有更高的活性,250℃时CO转化率可达78.1%。     

CeO2/Co3O4氧载体的制备及其甲烷化学链燃烧性能研究

制备了系列甲烷化学链燃烧用CeO₂/Co₃O₄复合氧载体,采用XRD、H₂-TPR、甲烷程序升温和恒温反应对氧载体进行了表征与评价。研究了不同CeO₂的负载量对复合氧载体的结构、氧化还原性、产物选择性的影响。结果表明,氧化铈的添加不仅降低了氧载体的初始反应温度,还延长了有效反应时间,但铈添加量过高会降低产物CO₂选择性,使甲烷向部分氧化进行。CeO₂(30%)/Co₃O₄氧载体在650 ℃经20次循环后甲烷转化率和CO₂选择性均未明显降低,表现出较高的活性和化学链循环稳定性。     

K/CeO2催化剂上碳黑催化燃烧性能及稳定性（英文）

采用不同的钾盐前体制备了一系列K/CeO2催化剂,利用热重和程序升温氧化(TPO)等技术考察了其催化性能及稳定性.结果表明,K/CeO2催化剂可使碳黑完全燃烧温度降低近200oC.钾盐前体对催化活性和稳定性具有较大影响,由于硝酸钾熔点低,金属在载体上的流动性强,有利于催化剂与碳黑的有效接触,因而表现了较高的活性,三次TPO循环试验中催化活性稳定.碳酸钾的熔点高且碱性较强,使碳黑燃烧生成的CO2不可逆吸附在其表面,导致反应活性低,TPO循环实验表明其反应速率降低,失活明显.     

锰改性对ZIF-67衍生Co3O4低温催化氧化甲醛性能的影响

针对ZIF-67衍生Co₃O₄催化剂低温甲醛氧化性能不佳的问题,采用锰（Mn）对Co₃O₄催化剂进行改性以提升其低温甲醛氧化性能。活性评价结果表明,相比于未改性的Co₃O₄催化剂,Mn改性后的Mn-Co₃O₄催化剂甲醛氧化活性显著提升,在118℃下即可实现90%的甲醛转化率(进口甲醛浓度为98.16 mg/m³,空速为60000 mL/（gcat·h）)。XRD、Raman和BET结果显示,Mn改性后催化剂的结晶度降低,缺陷增加,比表面积增大,这有利于反应物分子的吸附和活性位点的暴露。XPS、H₂-TPR和O₂-TPD表征结果表明,Mn-Co间存在的强相互作用显著改善了Mn-Co₃O₄催化剂的低温氧化还原性能和氧活化能力,使其具有更加丰富的Co³⁺和表面吸附氧物种。最终,这些因素共同...     

CeO2-MnOx催化剂上氯乙烯有机废气的催化燃烧

采用柠檬酸(CA)溶胶-凝胶法制备了不同Mn:(Ce+Mn)摩尔比的CeO2-MnOx催化剂,以氯乙烯有机废气的催化燃烧为模型反应,考察了催化剂制备条件和反应条件对于CeO2-MnOx催化剂性能的影响,并用N2吸附、X射线衍射(XRD)和H2程序升温还原(H2-TPR)对催化剂进行了表征.结果表明,CeO2-MnOx催化剂上氯乙烯燃烧反应产物只有HCl,H2O和CO2,没有检测到其他氯代烃和氯气等副产物.当CA:Mn:Ce=0.3:0.50:0.50时,所制备的CeO2-MnOx催化剂活性最高,对于较宽的空速范围(10000～30000h-1)和较宽的浓度范围(0.05%～0.15%),低浓度氯乙烯的催化燃烧反应具有较好的操作弹性.其中当氯乙烯浓度为0.1%,空速为15000h-1时,起燃温度T50=110oC,完全转化温度T99=220oC.XRD和H2-TPR结果表明,在CeO2-MnOx催化剂中只出现立方相萤石结构CeO2的特征衍射峰,没有出现MnOx物种的特征衍射峰;Mn离子进入CeO2晶格形成的Ce-Mn-O固溶体,有利于提高催化剂表面的活性氧物种的活性,乃至催化剂活性.     

水热法制备高纯超细CeO2-ZrO2复合氧化物

Superfine composite powders of CeO₂-ZrO₂ (CZ) and CeO₂-ZrO₂-La₂O₃ (CZL) were prepared by hydrothermal method. The effects of pH、temperature and time for hydrothermal process on the performance of the resulting powders were studied. The optimized reaction parameters were on follows: the precursor′s pH≈9.0, hydrothermal temperature of 200 ℃ holding for 2 h. Thermal stable powders with average particle size smaller than 10 nm and specific surface area of 171 m²·g^-1 were obtained. A BET specific surface area was still at 44 m²·g^-1 after calcination at 1 000 ℃ for 6 hours.     

Co3O4/CeO2 CO氧化的原位红外光谱研究

采用沉淀氧化法制备了Co₃O₄/CeO₂催化剂。分别在干、湿条件下进行了一氧化碳氧化反应研究。运用FT-IR表征手段,在钴铈复合氧化物上进行了CO吸附及CO/O₂共吸附研究。结果表明,与纯的Co₃O₄样品相比,Co₃O₄/CeO₂具有明显的抗湿气能力。Co₃O₄/CeO₂催化剂在进行CO氧化时,表面形成了类碳酸盐物种。当环境温度低于453 K时,催化剂上类碳酸盐的生成与形成类碳酸盐物种后受热分解存在着动态平衡。当环境温度高于493 K,催化剂上生成的类碳酸盐物全部受热分解。氧化铈的加入提高了催化剂的抗湿气性能。较小粒径的Co₃O₄与CeO₂产生的强相互作用可使CeO₂向Co₃O₄提供氧,因而间接提供了CO氧化需要的氧。     

纯相和镍取代的Co_3O_4尖晶石催化剂用于N_2O直接分解(英文)

A series of NixCo1-xCo2O4(0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N2O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500 °C for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co3O4. The N2O decomposition measurement revealed significant increase in the activity of Co3O4 spinel oxide catalyst with the partial replacement of Co2+ by Ni2+. The activity of this series of catalysts was controlled by the degree of Co2+ substitution by Ni2+, spinel crystallite size, catalyst surface area, presence of residual K+, and calcination temperature.     

Pt/Ce0.6Zr0.4O2催化剂催化氧化碳烟过程中活性氧对NO-NO2循环及表面含氧物种的分解作用简

通过在Ce_0.6Zr_0.4O₂载体上浸渍Pt（NO₃）₂制得Pt/Ce_0.6Zr_0.4O₂催化剂,该催化剂在松散接触条件下,于NO+O₂或O₂气氛中均表现出比Pt/Al₂O₃更好的碳烟氧化性能. 进一步研究表明,Pt/Ce_0.6Zr_0.4O₂催化剂中的Pt 与Ce_0.6Zr_0.4O₂存在相互作用,使得催化剂在一定温度范围内对活性氧的利用率大为提高,从而促进了气氛中NO↔NO₂的循环,乃至碳烟与NO₂的反应和碳烟表面含氧中间物种的生成;更重要的是,这部分活性氧本身可加速含氧中间物种的分解. 因此,在NO + O₂的气氛中,Pt/Ce_0.6Zr_0.4O₂催化剂的碳烟起燃温度比Pt/Al₂O₃降低了34 ℃.     

Catalytic oxidation of methane over Pd/Co3O4

The catalytic activity of Pd/Co₃O₄ toward methane oxidation has been examined in this study as a function of Pd loading, reaction temperature, space velocity and methane concentration in the reaction gas mixture. The bare oxide is quite active achieving a 100% methane conversion at 480°C under the reaction conditions used. The catalyst with the highest Pd loading tested of 10 wt.% yields the best activity curve, but the 5 wt.% Pd/Co₃O₄ catalyst performs nearly as well. Complete conversion for this catalyst is attained at 300°C and the activity remains stable over a 90-min test period.     

Room temperature carbon monoxide oxidation over Pt/Co2SnO4 and Pt/(Co3O4+SnO2) catalysts

Catalytic activities of Pt/Co2SnO4, Pt/(Co3O4+SnO2), Pt/SnO2, and Pt/Co3O4 catalysts for CO oxidation were investigated by varying CO concentration at room temperature. Reaction rates over Pt/Co2SnO4 and Pt/Co3O4 catalysts were not affected from increase in CO concentration. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of morphology-controllable mesoporous Co3O4 and CeO2

Recently, extensive works have been devoted to the morphology control of mesoporous materials with respect to their use in various applications. In this paper, we used two kinds of mesoporous silica, SBA-15 rods and spheres as hard templates to synthesize morphology-controllable mesoporous metal oxides. By carefully controlling the loading of metal precursors in the mesopores of the hard template, mesoporous Co₃O₄ and CeO₂ with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were conveniently obtained. The structural properties of these materials were characterized by XRD, BET, SEM and TEM. In addition, it is found that the differences observed in the textural properties of the two mesoporous metal oxides nanocasted from the same template can be attributed to the properties of metal precursors and the interaction between metal oxide and SiO₂. Thus-obtained mesoporous metal oxides with such special morphologies may have a potential application in the field of environmental catalytic oxidation.     

(CeO2)x-(La-Al2O3)1-x复合氧化物对柴油车尾气中可溶性有机成分的催化氧化

采用共沉淀法制备了一系列(CeO₂)_x-(La-Al₂O₃)_1-x复合氧化物(其中x为质量分数, x=0.00, 0.25, 0.50, 0.75, 1.00), 以其为催化剂. 采用热重-差热分析(TG-DTA)法模拟测试该系列催化剂对柴油车尾气中可溶性有机成分(SOF)的催化氧化性能. 结果表明, 当x=0.75时, 催化剂活性最高, 可使SOF在125℃起燃, 355℃完全转化. 并用低温N₂吸附-脱附, 储氧量(OSC)测试, X射线衍射(XRD), X射线光电子能谱(XPS)和H₂程序升温还原(H₂-TPR)等手段对催化剂进行了表征. 研究结果表明, 适量La 和Al 共掺杂增大了氧化铈的比表面积和催化剂中Ce³⁺所占的比例, 从而提高了催化剂对SOF的低温吸附能力和催化剂的储释放氧能力, 因而提高了催化剂对SOF的氧化活性. 所制备的(CeO₂)_0.75-(La-Al₂O₃)_0.25复合氧化物适合应用到柴油车尾气净化催化剂中.     

Effect of CeO2 and CaO Promoters on Ignition Performance for Partial Oxidation of Methane over Ni/MgO-Al2O3 Catalyst

The effect of CeO2 and CaO promoters on the ignition performance over Ni/MgO-Al2O3 catalyst for the partial oxidation of methane （POM） to synthesis gas was investigated. It was found that the POM reaction could not be ignited over lwt%Ni/MgO-Al2O3 catalyst without the promoters in the temperature range from 773 K to 1073 K. CeO2 and CaO promoters enhanced the ignition performance and the POM reactivity of lwt%Ni/MgO-Al2O3 catalyst remarkably. Moreover, the improving effect became greater with the increase of the promoter content under the investigated reactiorrconditions. The modification effects of CeO2 and CaO promoters were closely related to the concentration and reducibility of the surface and bulk oxygen species.     

Partial substitution of rhodium for cobalt in the misfit [Pb0.7Co0.4Sr1.9O3][CoO2]1.8 oxide

The partial substitution of Co by Rh in the [Pb_0⋅7Co_0.4Sr_1.9O₃]^RS[CoO₂]_1.8 family has been investigated. By transmission electron microscopy and X-ray powder diffraction, it is shown that the substitution of Rh for Co takes place at the two cobalt sites of the structure but for the low enough Rh contents, this substitution is made preferentially at the level of the CdI₂-like layer. Thus, a generic formula [Pb_0.7(Co_0.4−zRh_z)Sr_1.9O₃]^RS[Co_1−yRh_yO₂]_b1/b2 (0?y?0.5 and 0?z?0.3) can be proposed for this new family of misfit phase. As observed for the pure misfit cobaltite, the thermoelectric power is also very large, close to +140 μV/K at room temperature. The Rh cation can adopt a mixed valency Rh³⁺/Rh⁴⁺ (4d⁶/4d⁵) with low spin states t_2g⁶/t_2g⁵ equivalent to the ones of low spin Co³⁺/Co⁴⁺ (3d⁶/3d⁵). The large thermopower observed in the Rh substituted compounds is therefore a direct proof that the coexistence of low spin states t_2g⁶/t_2g⁵ contributes to the thermoelectric power enhancement in these oxides.