不同碱土金属氧化物掺杂对纳米二氧化铈催化性能的影响

通过水热法制备了平均粒径约为20nm的CeO₂,并在纳米CeO₂上引入不同浓度的3种碱土金属氧化物（MgO、CaO和BaO）。催化结果显示在用于催化二氧化碳和甲醇直接合成碳酸二甲酯（DMC）的反应中,此3种碱土金属氧化物均未对纳米CeO₂的催化活性起到促进作用。此外通过透射电镜（TEM）、X射线衍射（XRD）、比表面积及孔分布测试（BET）、X射线光电子能谱（XPS）和程序升温吸附（TPD）对所制备的催化剂进行了表征。研究结果表明,少量的碱土金属氧化物的掺杂不会导致CeO₂晶格变形,而是以无序的形式存在;且碱土金属氧化物的掺杂对纳米CeO₂的形貌、尺寸和织构性质影响不大,对其表面的Ce（Ⅳ）/Ce（Ⅲ）和酸碱性位的数量以及强度有较大影响。此外,较高的Ce（Ⅳ）/Ce（Ⅲ）和较多的酸性位是影响纳米CeO₂催化性能的重要因素。     

CeO2的形貌对CuO/CeO2催化剂CO2加氢制甲醇性能的影响

采用水热法制备CeO₂纳米颗粒（W-CeO₂）、CeO₂纳米片（S-CeO₂）、CeO₂纳米棒（B-CeO₂）及CeO₂纳米八面体（O-CeO₂）,用浸渍法负载相同质量分数的铜形成CuO/CeO₂催化剂。通过扫描电镜（SEM）、高分辨透射电子显微镜（TEM）、X射线衍射（XRD）、拉曼光谱（Raman）、自动吸附分析仪（BET）、H₂程序升温还原（H₂-TPR）、N₂O滴定等表征技术对催化剂进行表征,并在可控温控压的固定床石英管反应器中对催化剂的催化性能进行评价。研究了不同形貌CuO/CeO₂催化剂对CO₂加氢制备甲醇的影响;结果表明,CuO/CeO₂催化剂的催化活性存在明显的形貌依赖性,催化剂的暴露晶面、比表面积、表面碱性位点、表面氧缺陷的差异均会对CO₂转化率、甲醇选择性和产率产生影响。其中,不同形貌CeO₂优先暴露晶面的活性顺序为S-CeO₂（{100}+{110}）>W-CeO₂{100}>B-CeO₂{111}≈O-CeO₂{111},暴露晶面活性越高,催化剂表面氧缺陷越多,CuO-CeO₂间相互作用越强,则催化活性越好。当为CuO/S-CeO₂时,催化剂表面中碱性位点最多,催化剂比表面积为88.8m²/g,铜分散度为19.2%,CO₂转化率为6.56%,甲醇选择性和收率为96.3%和0.063g/(g_cat·h),催化活性最好,由活性评价试验得转化率由高到低依次为S-CeO₂>B-CeO₂>W-CeO₂>O-CeO₂,可知CeO₂形貌差异会决定CuO/CeO₂催化剂的物化性能和催化活性,从而提升对不同形貌CuO/CeO₂催化剂催化CO₂加氢制甲醇的基础认识。     

掺杂对CeO2基电解质材料性能的影响研究进展

掺杂CeO₂基电解质是中低温固体氧化物燃料电池（SOFC）理想的电解质材料。首先阐述了掺杂CeO₂基电解质结构与性能的关系,接着介绍了金属离子掺杂对CeO₂基电解质晶体结构和电子结构的影响,重点综述了单元素掺杂和双元素掺杂对CeO₂基电解质性能的影响。通过分析得出：稀土金属元素单掺杂比碱土金属元素单掺杂更能显著提高CeO₂基电解质的导电性和可烧结性,但稀土氧化物的原料成本要远高于碱土氧化物;双元素掺杂比单元素掺杂具有更多的氧空位无序度和更小的氧离子迁移激活能,因此在提高CeO₂基电解质的离子电导率方面更有优势。总结了CeO₂基电解质材料的掺杂规律及构效关系,以期对制备出性能更加优异的CeO₂基电解质起到一定的指导作用。     

氧化铈-二氧化硅介孔材料制备及对铜离子的吸附性能

采用共沉淀法和沉淀浸渍法制备了纳米氧化铈-二氧化硅（CeO₂-SiO₂）介孔材料吸附剂,主要考察了其对水中铜离子（Cu²⁺）的吸附行为。通过X射线衍射（XRD）、扫描电镜（SEM）和氮吸附（BET）等手段对合成的介孔材料进行了性能表征,并通过静态吸附实验分析了溶液pH、溶液初始金属离子质量浓度、吸附剂用量、吸附时间等条件对介孔材料吸附Cu²⁺性能的影响。结果表明：共沉淀法制备的纳米CeO₂-SiO₂介孔材料对Cu²⁺的去除效果较沉淀浸渍法要好;当溶液pH=7.0时CeO₂-SiO₂介孔材料对Cu²⁺的吸附效果最好,20 min时基本达到吸附平衡;溶液初始Cu²⁺浓度增大Cu²⁺去除率降低,Cu²⁺累计吸附量增大;随着吸附剂用量增加Cu²⁺去除率增大,当CeO₂-SiO₂吸附剂用量为0.15 g/L时对Cu²⁺的去除率趋于稳定;CeO₂-SiO₂吸附剂对不同金属离子吸附性能由大到小的顺序为Cu²⁺、Fe²⁺、Mn²⁺,该吸附过程均符合准二级动力学模型。     

铈锆复合氧化物催化HCl氧化中相互作用机制

采用浸渍法制备了不同负载量的ZrO₂/CeO₂·（xZr/Ce）和CeO₂/ZrO₂·（yCe/Zr）两组催化剂。并采用XRD、Raman、N₂-Sorption、TEM和H₂-TPR等手段对xZr/Ce和yCe/Zr的结构和性质进行表征,并结合HCl催化氧化活性研究CeO₂与ZrO₂在反应体系中的相互作用。结果显示,CeO₂表面掺杂适量的Zr⁴⁺可以增加xZr/Ce表面氧空位浓度,提高其HCl氧化反应活性;但当CeO₂表面掺杂过量的Zr⁴⁺,Zr元素会以ZrO₂的形式存在于xZr/Ce表面,覆盖氧空位,降低了xZr/Ce的反应活性。对于yCe/Zr催化剂,ZrO₂表面高分散的CeO₂有利于催化活性的提高,但ZrO₂表层负载的CeO₂对催化活性的贡献具有阈值,当CeO₂负载量超过10%后,额外增加的铈物种对催化活性已无显著促进作用;对比发现xZr/Ce的氧空位主要来自于铈锆固溶体,yCe/Zr的氧空位主要来自于高分散的CeO₂,由铈锆固溶体产生的氧空位对活性提升更有利;与纯组分CeO₂相比,xZr/Ce与yCe/Zr两组催化剂在苛刻条件下的长期稳定性测试中均表现出高反应稳定性。     

NiVP-PBA/g-C3N4赝电容复合材料的构筑及其CDI脱盐性能研究

以PBAs纳米粒子为模板，通过简单共沉淀法、水热反应法和气相沉积法制备出多金属磷化物NiVP-PBA/g-C₃N₄复合材料。利用电子显微镜、X射线衍射仪、N₂吸附/解吸测试仪、电化学工作站等对复合材料进行表征分析。结果表明，NiVP-PBA/g-C₃N₄材料具有中空核壳立方体结构，g-C₃N₄作为高导电性的改性剂均匀包裹在NiVP立方体外。此外，该材料的比表面积为23.43 m²/g,比电容达到80.09 F/g,具有77.63 mg/g的高脱盐能力。中空核壳结构的NiVP-PBA/g-C₃N₄电极具有优良的脱盐能力。     

MnO2纳米空心球的制备及其电化学性能

采用水热法通过添加Ce离子制备了MnO₂纳米空心球电极材料。Ce离子对MnO₂的形貌和结晶程度有很大的影响,添加Ce离子后生成由纳米棒组成的中空球,中空球比表面积(BET)达到315.2 m²·g^-1。MnO₂电极电化学测试结果表明:当铈锰摩尔比为0.2时电极材料具有较好的电化学性能,其比电容达到178.6 F·g^-1,与未加Ce离子相比其比电容提高了2.6倍,而且经过1000次循环稳定性测试后比电容仍保留了90.5%。这些结果表明添加Ce离子有利于形成中空结构,并提高了MnO₂电极的比电容。     

Study on catalytic performance of CeO2/CuO catalysts for preferential CO oxidation

采用水热法合成纳米尺寸的CuO,然后采用微乳液法或浸渍法将CeO₂负载在CuO上制备逆负载的CeO₂/CuO催化剂。通过X射线衍射（XRD）、程序升温还原（TPR）、比表面分析（BET）和富氢气中CO优先氧化活性测试等研究手段对催化剂进行了表征。研究发现,CeO₂/CuO催化剂的活性和选择性与CeO₂和CuO颗粒的尺寸密切相关,大颗粒的CuO载体有利于提高催化剂的选择性;小颗粒的氧化铈负载在大颗粒的氧化铜上,可以产生更多两相接触界面,有助于提高催化剂的活性。     

CeO2/石墨烯纳米复合材料摩擦性能研究

利用水热法合成不同重量比的二氧化铈/石墨烯(CeO₂/G)纳米复合材料。利用X射线衍射仪、X射线光电子能谱仪、红外光谱仪、扫描电子显微镜对复合材料进行了组成结构分析。通过四球摩擦机对所制样品进行摩擦实验,研究不同重量比对CeO₂/G纳米复合材料摩擦性能的影响,并用扫描电子显微镜对小钢球表面磨痕进行表征。结果表明,CeO₂纳米颗粒均匀负载在石墨烯片上,同时作为间隔物防止石墨烯片再次聚集。在摩擦条件载荷392 N,转速1 200 r/min下,添加相同质量分数(0.5%)的样品时,石墨烯和硝酸铈重量比为1∶8的样品减摩抗磨性能更好,使润滑油摩擦系数下降49%,磨斑直径下降20%。     

改性氧化铈/钨酸镍环氧防腐涂层的制备及性能

采用水热法制备出不同质量比的氧化铈/钨酸镍(CeO₂/NiWO₄)的复合粒子,再选用硅烷偶联剂KH560对其进行改性,利用傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）和扫描电子显微镜（SEM）表征了复合粒子的结构与形貌。将改性的复合粒子分散于环氧树脂（EP）中,然后喷涂在碳钢基体上制备CeO₂/NiWO₄/EP复合涂层,利用电化学交流阻抗（EIS）、加速浸泡实验和摩擦磨损试验（Taber）测试涂层的防腐与摩擦性能。结果表明：添加CeO₂/NiWO₄复合粒子的环氧树脂涂层的防腐耐磨性能大幅度提高,而且当复合粒子中CeO₂与NiWO₄的质量比为4∶3时,涂层防腐耐磨性能最好,该复合环氧涂层在3.5%NaCl水溶液中浸泡后期(45天)仍保持较高的阻抗模量(7.36×10⁸ Ω/cm²),比纯环氧树脂涂层高一个数量级。同时,经过10000转摩擦磨损后,此复合涂层的质量损失较纯环氧涂层减少56%,厚度损失量仅为CeO₂/EP的50%,表现出最优异的防腐耐磨性能。     

十水草酸铈的热分解过程以及热分解动力学研究

利用TG-DSC法研究了十水草酸铈在N2和O2氛围下煅烧过程的差异及其分解动力学机理.结果表明,十水草酸铈在N2气氛下煅烧时,煅烧产物CeO2表面附着有黑色的炭黑,而在O2气氛下煅烧时,仅得到浅黄色的CeO2.依据实验结果推测,十水草酸铈在N2气氛下煅烧时经历3步热分解过程;而在O2气氛下煅烧时经历2步分解过程,第1步...     

Potential rare-earth modified CeO2 catalysts for soot oxidation: Part III. Effect of dopant loading and calcination temperature on catalytic activity with O2 and NO + O2

CeO₂ and CeReO_x_y catalysts are prepared by the calcination at different temperatures (y = 500–1000 °C) and having a different composition (Re = La³⁺ or Pr^3+/4+_, 0–90 wt.%). The catalysts are characterised by XRD, H₂-TPR, Raman, and BET surface area. The soot oxidation is studied with O₂ and NO + O₂ in the tight and loose contact conditions, respectively. CeO₂ sinters between 800–900 °C due to a grain growth, leading to an increased crystallite size and a decreased BET surface area. La³⁺ or Pr^3+/4+ hinders the grain growth of CeO₂ and, thereby, improving the surface catalytic properties. Using O₂ as an oxidant, an improved soot oxidation is observed over CeLaO_x_y and CePrO_x_y in the whole dopant weight loading and calcination temperature range studied, compared with CeO₂. Using NO + O₂, the soot conversion decreased over CeLaO_x_y catalysts calcined below 800 °C compared with the soot oxidation over CeO₂_y. CePrO_x_y, on the other hand, showed a superior soot oxidation activity in the whole composition and calcination temperature range using NO + O₂. The improvement in the soot oxidation activity over the various catalysts with O₂ can be explained based on an improvement in the external surface area. The superior soot oxidation activity of CePrO_x_y with NO + O₂ is explained by the changes in the redox properties of the catalyst as well as surface area. CePrO_x_y, having 50 wt.% of dopant, is found to be the best catalyst due to synergism between cerium and praseodymium compared to pure components. NO into NO₂ oxidation activity, that determines soot oxidation activity, is improved over all CePrO_x catalysts.     

Nanophase catalytic oxides: I. Synthesis of doped cerium oxides as oxygen storage promoters

Doped CeO₂ materials were synthesized with the aim to improve the performance of CeO₂ as oxygen storage promoter in gas catalytic reactions. The coprecipitation method was used for the synthesis of fine oxalate precursors of high homogeneity and well defined composition. The chemical and morphological properties of both the coprecipitated oxalates and the calcined oxides were examined. The influence of doping of different metal cations into the CeO₂ structure on the oxygen storage capacity in particular was investigated. Some of the doped oxides Ce_0.9M_0.1 O_{2 − δ} (M = Ca, Nd, Pb, etc.) give an increased oxygen storage capacity, 20–40% higher than the undoped. Their redox activity also remarkably increased.     

Obtaining CeO2–ZrO2 mixed oxides by coprecipitation: role of preparation conditions

The preparation of CeO₂–ZrO₂ mixed oxides preparation was studied by evaluating the influence of several conditions. Coprecipitation was taken as the standard method and the effects brought about by the cerium salt precursor ((NH₄)₂Ce(NO₃)₆ or Ce(NO₃)₃), the introduction of drying and aging steps as well as pH controlling upon precipitation were analyzed. The samples were characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, infrared spectroscopy, oxygen storage capacity and surface area. The use of Ce(NO₃)₃ leads to the formation of c-CeO₂ and t-ZrO₂ mixed oxide whereas a solid solution is achieved by using (NH₄)₂Ce(NO₃)₆. It was observed that the cerium precursor is the most significant parameter of preparation procedure since it defines the crystalline phases and consequently the reducibility behavior of the CeO₂–ZrO₂ system.     

Nano-structured CeO2 supported Cu-Pd bimetallic catalysts for the oxygen-assisted water–gas-shift reaction

The present work focuses on the development of novel Cu-Pd bimetallic catalysts supported on nano-sized high-surface-area CeO₂ for the oxygen-assisted water–gas-shift (OWGS) reaction. High-surface-area CeO₂ was synthesized by urea gelation (UG) and template-assisted (TA) methods. The UG method offered CeO₂ with a BET surface area of about 215 m²/g, significantly higher than that of commercially available CeO₂. Cu and Pd were supported on CeO₂ synthesized by the UG and TA methods and their catalytic performance in the OWGS reaction was investigated systematically. Catalysts with about 30 wt% Cu and 1 wt% Pd were found to exhibit a maximum CO conversion close to 100%. The effect of metal loading method and the influence of CeO₂ support on the catalytic performance were also investigated. The results indicated that Cu and Pd loaded by incipient wetness impregnation (IWI) exhibited better performance than that prepared by deposition–precipitation (DP) method. The difference in the catalytic activity was related to the lower Cu surface concentration, better Cu–Ce and Pd–Ce interactions and improved reducibility of Cu and Pd in the IWI catalyst as determined by the X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) studies. A direct relation between BET surface area of the CeO₂ support and CO conversion was also observed. The Cu-Pd bimetallic catalysts supported on high-surface-area CeO₂ synthesized by UG method exhibited at least two-fold higher CO conversion than the commercial CeO₂ or that obtained by TA method. The catalyst retains about 100% CO conversion even under extremely high H₂ concentration.     

CeO2复合改性ZSM-5分子筛用于催化甲醇制丙烯研究

在甲醇制丙烯(MTP)反应中,ZSM-5分子筛较强的酸性易使甲醇与ZSM-5接触发生氢转移、芳构化等二次反应,堵塞孔道,使得其微孔结构更加不利于分子的扩散,加速催化剂积碳失活,导致丙烯选择性和丙烯/乙烯(P/E)比值下降。因此,本文利用催化活性较高的CeO₂对ZSM-5分子筛进行复合改性以达到有效降低其酸性并增大介孔的目的来提高丙烯选择性和P/E比。通过XRD、NH₃-TPD和N₂吸脱附技术表征,研究了不同ZSM-5硅铝比(摩尔比)、两相质量比(m(CeO₂)/m(ZSM-5))对CeO₂/ZSM-5复合催化剂物化性质的影响。在反应温度480 ℃、重时空速2.6 h^-1、N₂流量100 mL·min^-1、常压纯甲醇进料的条件下,考察了所制备的复合催化剂催化MTP的性能。结果表明,硅铝比为250、m(CeO₂)/m(ZSM-5)为1∶4的复合催化剂比以往研究结果具有更优异的MTP催化性能,甲醇转化率为99.9%,丙烯选择性为42.78%,P/E比为6.3。     

Catalytic wet air oxidation of phenol and acrylic acid over Ru/C and Ru–CeO2/C catalysts

Ru/C catalysts promoted, or not, by cerium were prepared by impregnation of an active carbon (961 m² g⁻¹) with chlorine-free precursors of Ru and Ce. They were characterized by chemisorption of H₂ and of CO and by electron microscopy. TEM and H₂ chemisorption gives coherent results while CO chemisorption overestimates Ru dispersion. In Ru–Ce/C, Ce is in close contact with Ru and decreases Ru accessibility.

Catalytic wet air oxidation (CWAO) of phenol and of acrylic acid (160°C and 20 bar of O₂) was investigated over these catalysts and their performance (activity, selectivity to intermediate compounds) compared with that of a reference Ru/CeO₂ catalyst. Carbon-supported catalysts were very active for the CWAO of phenol but not for acrylic acid. Although high conversions were obtained, phenol was not totally mineralized after 3 h. It was shown that acrylic acid was more strongly adsorbed than phenol. Moreover, the number of contact points between Ru particles and CeO₂ crystallites constitutes a key parameter in these reactions. A high surface area of ceria is required to insure O₂ activation when the organic molecule is strongly adsorbed.     

New ceria-based catalysts for pollution abatement

In the present work, we describe the use of fluorite-structured solid solutions, based on mixtures of CeO₂/La₂O₃/Pr₂O₃, and similar systems, i.e. CeO₂/Ln₂O₃/Pr₂O₃ where Ln=Tb, Sm, and Gd as effective catalysts for methane combustion. Mixed lanthanide oxide doped ceria solid solutions were prepared using an evaporation method from nitrate precursors and were subsequently calcined to 1073 K. Sample characterisation was achieved using powder X-ray diffraction (PXRD) and temperature programmed reduction (TPR). PXRDs obtained subsequent to a 12 h calcination at 1073 K for 12 h all show peaks corresponding to a fluorite-based structure. There are no additional features suggestive of large-scale segregation or ordered superstructure formation. This was confirmed by Rietveld analysis which showed that the lattice possesses cubic nature with a=b=c=5.50 Å. Methane combustion tests show that the most effective catalysts are those lanthanide oxide doped ceria catalysts prepared with 5% Pr molar metal ratios. TPR experiments suggest PrO₂ is an essential component and both surface and bulk chemistries have important roles in catalytic activity.     

Catalytic reduction of NO by CO over NiO/CeO2 catalyst in stoichiometric NO/CO and NO/CO/O2 reaction

A new catalyst composed of nickel oxide and cerium oxide was studied with respect to its activity for NO reduction by CO under stoichiometric conditions in the absence as well as the presence of oxygen. Activity measurements of the NO/CO reaction were also conducted over NiO/γ-Al₂O₃, NiO/TiO₂, and NiO/CeO₂ catalysts for comparison purposes. The results showed that the conversion of NO and CO are dependent on the nature of supports, and the catalysts decreased in activity in the order of NiO/CeO₂ > NiO/γ-Al₂O₃ > NiO/TiO₂. Three kinds of CeO₂ were prepared and used as support for NiO. They are the CeO₂ prepared by (i) homogeneous precipitation (HP), (ii) precipitation (PC), and (iii) direct decomposition (DP) method. We found that the NiO/CeO₂(HP) catalyst was the most active, and complete conversion of NO and CO occurred at 210 °C at a space velocity of 120,000 h⁻¹. Based on the results of surface analysis, a reaction model for NO/CO interaction over NiO/CeO₂ has been proposed: (i) CO reduces surface oxygen to create vacant sites; (ii) on the vacant sites, NO dissociates to produce N₂; and (iii) the oxygen originated from NO dissociation is removed by CO.