固相浸渍法和湿浸渍法制备CuO/CeO2催化剂及其CO氧化性能的对比研究

采用固相浸渍法和常规湿浸渍法制备了一系列CuO/CeO₂催化剂,并结合X射线衍射（XRD）、氢气-程序升温还原（H₂-TPR）、激光拉曼光谱（LRS）、原位漫反射红外光谱（in situ DRIFTS）、X射线光电子能谱（XPS）等手段考察了制备方法对催化剂结构性质及其在CO氧化反应中性能的影响. XPS和H₂-TPR结果表明,固相浸渍法更有利于得到高分散的铜物种,并促进CuO物种的还原. LRS结果表明,相比于湿浸渍法,固相浸渍法能产生更多氧空位,而这些氧空位可以活化参与反应的O₂. CO氧化活性测试结果表明,当铜负载量相同时,固相浸渍法制备的催化剂相比于湿浸渍法表现出更好的催化性能. 结合多种表征结果发现,催化剂CO氧化性能与其表面氧空位和Cu⁺-CO浓度紧密相关,提出了CuO/CeO₂催化剂在CO氧化反应中可能的协同作用机制.     

Ni-Mo氮化物催化剂:合成及其丙烷氨氧化催化性能简

分别采用溶胶-凝胶法、旋转蒸发微波干燥法、共沉淀法、浸渍法和机械混合法制备Ni-Mo氧化物前驱体. 以H₂和N₂的混合气为氮化气体,采用程序升温氮化法合成了镍钼氮化物催化剂. 利用X射线衍射、总氮含量分析、X射线光电子能谱及H₂程序升温还原对Ni-Mo氧化物前体及氮化物催化剂进行了表征. 将上述Ni-Mo氮化物催化剂用于丙烷氨氧化反应中. 结果表明,Ni-Mo氧化物前驱体的制备方法影响其氮化物催化剂上丙烷氨氧化反应性能. Ni-Mo氮化物催化剂中氮物种的移动性及反应性对产物丙烯腈选择性的影响较大,共沉淀法制备的催化剂存在大量的活性氮物种,因而具有良好的催化丙烷氨氧化反应活性.     

Au/α-Fe2O3 催化剂存贮失活环境因素及机理分析

 采用沉积沉淀法制备了 CO 低温氧化催化剂 Au/α-Fe₂O₃, 通过 X 射线衍射、X 射线光电子能谱、N₂ 吸附-脱附、傅里叶变换红外光谱、H₂ 程序升温还原和 CO₂ 程序升温脱附等手段对催化剂进行了表征, 探讨了在室温大气气氛下光线照射以及表面吸附等环境因素所导致的催化剂存贮失活及其作用机理. 结果表明, 经 110 ^oC 干燥的 Au/α-Fe₂O₃催化剂表面同时存在 Au³⁺和 Au^δ+ (0 ≤ δ ≤ 1) 物种, 且前者催化 CO 氧化的活性更高; 在室温大气气氛下, 紫外线照射会引起 Au³⁺的还原和 Au 颗粒的生长, 导致催化剂的不可逆失活. 此外, 空气中的 H₂O 和 CO₂ 可同时吸附在 α-Fe₂O₃的表面, 形成表面碳酸盐物种, 会引起催化剂的可逆失活.     

浸渍/共沉淀法对BaO改性单Pd催化剂净化甲醇汽油车尾气性能的影响

采用浸渍和共沉淀两种方法分别制备了BaO改性的Pd/CeO₂-ZrO₂-La₂O₃-Al₂O₃催化剂.运用N₂吸附-脱附,X射线衍射(XRD),H₂程序升温还原(H₂-TPR),NH₃程序升温脱附(NH₃-TPD),透射电子显微镜(TEM)和X射线光电子能谱(XPS)对催化剂进行表征,并考察其对甲醇,CO, C₃H₈ 和 NO的催化性能.活性测试结果表明,BaO的引入可明显改善Pd催化剂对甲醇,CO, C₃H₈和NO的催化活性,且浸渍法最佳,起燃温度(T₅₀)分别降低了43,31,45和35 ℃.XRD,H₂-TPR及XPS结果表明,浸渍法引入BaO主要通过表面改性方式,强化Pd-Ce界面间的相互作用,改善催化剂的还原性能,进而提高催化剂的低温活性;而共沉淀法则是通过结构改性方式增加CeO₂晶格缺陷,加速活性氧物种的流动,Ce³⁺浓度的增加是促使CO氧化活性显著提高的主要原因.     

载体对Pd-Cu/活性炭催化剂在消除卷烟主流烟气中CO活性的影响

采用等体积浸渍法制备了Pd-Cu/活性炭催化剂, 用脉冲反应考察了催化剂对模拟卷烟主流烟气(4.4 CO-4.2 H₂O-19.2 O₂-72.2 He)(体积分数, %)中CO的常温催化氧化性能, 系统研究了不同的活性炭载体对催化剂的CO常温氧化活性的影响. 研究表明, 在室温条件下, 催化剂对CO氧化反应的活性顺序为: 椰壳活性炭为载体的催化剂(CAC)<木质活性炭为载体的催化剂(WAC)<超级活性炭为载体的催化剂(SAC), 并且活性炭载体对催化剂的反应诱导期也存在显著的影响. 对催化剂的表征结果表明, 不同活性炭载体表面上含氧官能团含量不同, 影响催化剂表面Pd和Cu的存在状态, 使得SAC催化剂上的Pd只以Pd²⁺形式存在, 而CAC和WAC催化剂上的Pd以Pd²⁺和Pd⁰形式存在, 导致SAC催化剂比CAC和WAC两种催化剂具有更好的CO催化氧化活性. 使用催化剂接装的三段式复合滤嘴试验卷烟, 与对照卷烟相比, 卷烟主流烟气中CO的释放量都有所降低, 其中添加SAC催化剂的效果最为明显. 如果将Pd的负载量增加为3.4% (w), SAC催化剂对卷烟主流烟气中CO的去除率高达25.4%.     

镍基催化剂上稻草水蒸气重整制富氢合成气

采用浸渍法制备了SiO₂, γ-Al₂O₃, CaO和TiO₂负载的Ni催化剂, 以及不同MgO含量的MgO-7.5%Ni/γ-Al₂O₃催化剂,利用X射线衍射和N₂吸附-脱附技术表征了催化剂的结构,在固定床反应器上评价了它们在稻草水蒸气催化重整制合成气反应中的催化性能,考察了反应条件对催化剂性能的影响.结果表明, 以γ-Al₂O₃为载体时Ni催化剂活性最高,其中7.5%Ni/γ-Al₂O₃催化剂的H₂收率可达1071.3ml/g,H₂:CO的体积比为1.4:1;同时,MgO的添加进一步提高了该催化剂的性能,当MgO含量为1.0%时,H₂收率可达1194.6ml/g,H₂:CO体积比可达3.9:1.可见MgO的加入促进了Ni基催化剂上稻草水蒸气催化重整制合成气反应的进行,同时使得合成气中CO发生水-汽转换反应,从而大大提高了合成气中H₂含量.     

微波加热分解法制备CuO-Ce0.6Zr0.4O2及其催化CO氧化性能

采用微波加热分解法制备了一系列CuO含量(0-25%, w)不同的CuO-Ce_0.6Zr_0.4O₂催化剂, 并用X射线衍射(XRD)、透射电镜(TEM)、N₂吸附-脱附(BET)和H₂程序升温还原(H₂-TPR)技术对催化剂进行了表征, 利用色谱流动法考察了其催化CO低温氧化性能. 结果表明: 当CuO含量为15%时, 所制备催化剂的催化活性最佳. 在催化剂中存在三种不同类型的铜物种, 即高分散、小颗粒和大颗粒的CuO. 催化剂表面高分散和小颗粒的CuO有利于催化活性的提高, 而大颗粒的CuO对催化活性具有抑制作用.     

Ni-Cu双金属催化剂上乙醇水蒸气重整制氢研究—制备方法对催化性能的影响

我们采用分步浸渍法和共浸渍法制备了一系列的Ni-Cu/mSiO₂催化剂.运用XRD、N₂吸附-脱附、H₂-TPR、SEM、TG-DTG等表征手段对催化剂反应前后的物理化学性质进行分析,催化剂对乙醇水蒸气重整（ESR）反应的催化性能通过常压固定床反应器进行评价.结果表明：催化剂的催化性能与载体上的活性组分分散有关,而活性金属的分散性与制备方法有关.共浸渍法制备的催化剂Ni₁₄-Cu/mSiO₂活性组分分散度较高,抗积碳能力与稳定性更好.在质量空速为2.7 h^-1,水醇摩尔比为9,反应温度为550℃的条件下进行稳定性测试,催化剂Ni₁₄-Cu/mSiO₂测试25 h没有出现失活现象,乙醇转化率保持在100%,H₂的选择性保持在70%以上,反应后的积碳含量仅为5.52%.     

P123软模板对CuO-CeO2结构及其CO催化氧化性能的影响

采用软模板水热法制备了不同Cu/Ce物质的量之比的CuO-CeO₂(n_Cu:n_Ce=1:9、2:8、3:7、4:6、5:5、6:4、7:3)催化剂。考察了n_Cu:n_Ce和制备方法(软模板水热法和无模板共沉淀法)对CuO-CeO₂催化剂低温催化氧化CO性能的影响,并采用XRD、N₂-吸附脱附、TEM、H₂-TPR和XPS等表征手段对催化剂的结构、氧化还原特性和表面化学状态等进行了分析。结果表明,随着nCu:nCe的增加,CuO-CeO₂催化剂的CO催化氧化活性先升高后降低。当n_Cu:n_Ce=5:5时,催化剂在100℃时CO转化率即达到90%以上。采用软模板水热法制备的CuO-CeO₂催化剂大的比表面积、狭窄的孔道分布结构、活性CuO物种高的分散状态和CuO与CeO₂之间存在强相互作用是其具有优异的CO催化氧化活性的主要原因。     

Pt/ZrO2-Al2O3催化剂催化氧化C3H6和CO性能

采用共沉淀法合成了ZrO₂与Al₂O₃的不同质量比的ZrO₂-Al₂O₃复合氧化物,并以此为载体通过等体积浸渍法制备了1.5% Pt/ZrO₂-Al₂O₃（w/w）催化剂。以C₃H₆和CO为反应物的催化性能评价显示,在系列催化剂中以Pt/Zr（0.4）-Al催化剂催化氧化活性最为优异,其C₃H₆和CO的起燃温度（T₅₀）小于125℃,完全转化温度（T₉₀）小于150℃。采用XRD、低温N₂吸附、H₂-TPR、CO脉冲吸附等分析表征技术探索了催化剂物相结构、比表面积、颗粒尺寸等对催化活性的影响规律。结果发现,ZrO₂-Al₂O₃复合氧化物具有Al₂O₃材料的介孔织构和大比表面积特性,且产生了Al_xZr_1-xO_y固溶体新物相。适当的ZrO₂与Al₂O₃的质量比,是改善Pt与ZrO₂-Al₂O₃的相互作用强度,促进贵金属Pt的分散,提升Pt/ZrO₂-Al₂O₃催化剂的低温氧化活性的关键。     

Promotion effect of adsorbed water/OH on the catalytic performance of Ag/activated carbon catalysts for CO preferential oxidation in excess H2

Activated carbon (AC) supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation (PROX) in excess H₂ was evaluated. Ag/AC catalysts, after reduction in H₂ at low temperatures (≤200 °C) following heat treatment in He at 200 °C (He200H200), exhibited the best catalytic properties. Temperature-programmed desorption (TPD), X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicated that silver oxides were produced during heat treatment in He at 200 °C which were reduced to metal silver nanoparticles in H₂ at low temperatures (≤200 °C), simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 °C. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H₂00 treatment displayed similar PROX of CO reaction properties to Ag/SiO₂. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.     

Study of CuO/Ce0.8Zr0.2O2 catalysts for low-temperature CO oxidation

Summary Copper oxide catalysts supported on Ce_0.8Zr_0.2O₂ were prepared via an impregnation method and characterized by XRD and H₂-TPR techniques. The catalytic activity of the samples for low-temperature CO oxidation was investigated by means of a microreactor-GC system. The influence of calcination temperature, calcination time and different CuO content on the catalytic activity was studied. TPR analysis indicated that well-dispersed CuO was responsible for the low-temperature CO oxidation. The results of the investigation showed that the calcination temperature and CuO loadings had larger influence than the calcination time.     

Catalytic carbon monoxide oxidation over CuO/CeO2 composite catalysts

Summary CeO₂ nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supports for CuO/CeO₂ catalysts prepared via the impregnation method. The samples were characterized by XRD, HRTEM, H₂-TPR and XPS. The catalytic properties of the catalysts for low-temperature CO oxidation were studied by using a microreactor-GC system.     

Influence of ceria preparation method on the performance of CuO/CeO2 catalysts

Ceria were prepared by various processes. The prepared samples and commercial ceria were used as supports to prepare the CuO/CeO₂ catalysts via an impregnation method. The samples were characterized by using TEM, XRD, H₂-TPR, and their catalytic activities in low-temperature CO oxidation were also investigated.     

Recent Advances in Preferential Oxidation of CO in H2 Over Gold Catalysts

Recent studies have revealed that supported gold catalysts exhibit comparable or superior catalytic performance relative to platinum group metals, especially at low temperatures, in the preferential oxidation of CO under excess H₂ (CO-PROX). Complete conversion of CO with good selectivity of O₂ for CO₂ and highly stable catalyst performance in the presence of CO₂ and H₂O are considered to be essential for the successful development of CO-PROX catalysts for application in polymer electrolyte membrane fuel cells. The performance of supported gold catalysts in the CO-PROX reaction has been shown to be dependent on the characteristics of gold (size, oxidation state, and its interaction with other metal/oxides), nature of the support (size, composition, preparation method, presence of promoters, and doping with other metal ions), and reaction conditions (temperature and feed composition). Complete CO conversion has been achieved in the presence of certain gold catalysts below 100 °C. The unresolved issues in CO-PROX include the undesired oxidation of H₂, detrimental effects of CO₂ and/or H₂O, and long-term stability of the catalysts. To address these issues, the catalytic activity of gold supported on simple oxides such as TiO₂, CeO₂, Al₂O₃, and Fe₂O₃ has been improved dramatically by the addition of promoters, alteration of the gold-oxide support interface, and modification of the oxide supports. Recently, nanoporous gold has also been recognized to be promising for this reaction. This review highlights recent developments of unsupported and supported gold catalysts for the CO-PROX reaction.     

多孔材料负载金催化剂的制备与应用*

本文综述了微孔材料和介孔材料负载型金催化剂的制备、表征与应用研究的最新进展,从多孔载体的选择（氧化物、微孔分子筛、介孔氧化物、介孔分子筛和介孔碳材料）、金的最新负载方法（沉积-沉淀法、溶胶-凝胶法、原位法/一步法和化学气相沉积法）与表征及其催化性能（一氧化碳低温氧化、氢气/氧气直接合成过氧化氢、直接合成环氧丙烷和有机物的选择性氧化）等方面详尽地评述了微孔材料和介孔材料负载型金催化剂研究概况。同时,提出了多孔材料负载金催化剂存在的一些问题,并展望了其研究和发展的方向。     

固相浸渍法制备NiO/CeO2催化剂及其在CO氧化反应中的应用

采用固相浸渍法制备了一系列NiO/CeO2催化剂,并通过与常规湿浸渍法比较,考察了制备方法对催化剂和CO氧化反应性能的影响.同时结合X射线衍射(XRD),N2吸附-脱附(BET),透射电镜(TEM),氢气-程序升温还原(H2-TPR),拉曼(Raman)光谱,X射线光电子能谱(XPS)等手段对催化剂的结构和表面物种分散状态进行了表征.CO氧化活性测试结果表明,当镍负载量相同时,固相浸渍法制备的催化剂相比于湿浸渍法表现出更好的催化性能.TEM、XPS、H2-TPR结果表明,固相浸渍法更有利于加强镍铈间的相互作用和得到高分散的镍物种,从而促进镍物种的还原.Raman结果表明固相浸渍法相比于湿浸渍法能产生更多氧空位,这有利于氧气在催化剂表面的活化,使得CO氧化反应更容易进行.     

Hydrogen Spillover Enhanced Hydroxyl Formation and Catalytic Activity Toward CO Oxidation at the Metal/Oxide Interface

H₂‐promoted catalytic activity of oxide‐supported metal catalysts in low‐temperature CO oxidation is of great interest but its origin remains unknown. Employing an FeO(111)/Pt(111) inverse model catalyst, we herewith report direct experimental evidence for the spillover of H(a) adatoms on the Pt surface formed by H₂ dissociation to the Pt?FeO interface to form hydroxyl groups that facilely oxidize CO(a) on the neighboring Pt surface to produce CO₂. Hydroxyl groups and coadsorbed water play a crucial role in the occurrence of hydrogen spillover. These results unambiguously identify the occurrence of hydrogen spillover from the metal surface to the noble metal/metal oxide interface and the resultant enhanced catalytic activity of the metal/oxide interface in low‐temperature CO oxidation, which provides a molecular‐level understanding of both H₂‐promoted catalytic activity of metal/oxide ensembles in low‐temperature CO oxidation and hydrogen spillover.     

Palladium Encapsulated by an Oxygen-Saturated TiO2 Overlayer for Low-Temperature SO2-Tolerant Catalysis during CO Oxidation

The development of oxidation catalysts that are resistant to sulfur poisoning is crucial for extending the lifespan of catalysts in real-working conditions. Herein, we describe the design and synthesis of oxide-metal interaction (OMI) catalyst under oxidative atmospheres. By using organic coated TiO₂, an oxide/metal inverse catalyst with non-classical oxygen-saturated TiO₂ overlayers were obtained at relatively low temperature. These catalysts were found to incorporate ultra-small Pd metal and support particles with exceptional reactivity and stability for CO oxidation (under 21 vol % O₂ and 10 vol % H₂O). In particular, the core (Pd)-shell (TiO₂) structured OMI catalyst exhibited excellent resistance to SO₂ poisoning, yielding robust CO oxidation performance at 120 °C for 240 h (at 100 ppm SO₂ and 10 vol % H₂O). The stability of this new OMI catalyst was explained through density functional theory (DFT) calculations that interfacial oxygen atoms at Pd−O−Ti sites (of oxygen-saturated overlayers) serve as non-metal active sites for low-temperature CO oxidation, and change the SO₂ adsorption from metal(d)-to-SO₂(π*) back-bonding to much weaker σ(Ti−S) bonding.     

Oxidation of Carbon Monoxide on Co-, Ni-, and Cu-containing Catalysts Prepared by Pyrolysis of Metal β-Diketonates on Synthetic Foamed Ceramics

Catalytic systems containing Co, Ni, and Cu composite coatings prepared by gas-phase thermolysis of metal acetylacetonates and hexafluoroacetylacetonates on synthetic foamed ceramics were suggested for oxidation of CO to CO₂. The relative activities of the catalysts and the kinetic and activation parameters of CO oxidation were determined. The catalytic activity depends on the catalyst preparation procedure.