0.1%Pt-0.02%Pd/不锈钢整体催化剂上丙酮氧化性能及稳定性(英文)

制备了0.1%Pt-0.02%Pd/不锈钢整体催化剂。选取不锈钢为该催化剂的载体,可克服传统γ-Al2O3和堇青石蜂窝载体热稳定性差的缺点。采用阳极氧化技术在不锈钢上自生长了结构致密的多孔阳极氧化膜,并在其上负载Pt和Pd制备得到挥发性有机物(VOCs)净化催化剂。结果表明,经500、800和1000℃不同温度焙烧后,该催化剂完全氧化丙酮的温度分别为160、160和200℃。该催化剂表现出以下优点:(a)高温稳定性能好;(b)低温催化活性高;(c)贵金属负载量低。通过SEM和EDX等技术对该催化剂的结构及活性组分分散情况进行了表征。     

Property and structure of various platinum catalysts for low-temperature carbon monoxide oxidations

The oxidation of carbon monoxide (CO) has received more attention in the last two to three decades owing to its importance in different fields. To control this CO pollution, catalytic converters have been investigated. Different types of catalysts have been used in a catalytic converter for CO emission control purposes. Platinum (Pt)-based noble metal catalysts show great potential for CO oxidation in catalytic converters with high thermal stability and tailoring flexibility. Pt metal catalysts modified with promoters such as alkali metals and reducible metal oxides have received great attention for their superior catalytic activities in CO oxidation. Temperature, close environment of the catalyst, and chemical composition in the surface layer of the catalyst have a huge effect on the active phase dispersion and O₂ adsorption capacity of the Pt metal catalysts. The main difference in activities of Pt metal catalyst for CO oxidation in O₂ or H₂ atmosphere has found. The addition of supports in Pt metal catalysts has improved their performances and reduced their cost. These improvement strongly depends on the surface structure, morphology, number of active sites, and various Pt-O interactions. Many research articles have already been published in CO oxidation over Pt metal catalysts, but no review article dedicated to CO oxidation is available in the literature.     

Oxidation of Hydrogen by Metal Complexes of Platinum and Palladium Immobilized on Silica

The thermal stability of metal complexes immobilized on the surface of silica and its connection with the catalytic activity in the oxidation of hydrogen were investigated. High catalytic activity was exhibited by heterogenized platinum and palladium acetylacetonate near room temperatures in the initial state and by γ-aminopropylsilicas treated with platinum and palladium complexes. The catalytic activity of the metal complexes correlates with their thermal stability and with the ability to undergo oxidation to a metal state with high valence. This revised version was published online in August 2006 with corrections to the Cover Date.     

中空纤维Au-CeZr/FAU催化膜的制备及在富氢气氛CO选择性氧化反应中的应用

采用浸渍法制备了一系列不同Ce/Zr掺杂比例的FAU分子筛膜, 并进一步负载纳米金, 制备了Au-CeZr/FAU催化膜. 对催化膜的微观形貌及结构进行了表征, 并对其在富氢气氛中催化CO优先氧化性能进行了研究. H₂-TPR结果表明, Ce/Zr掺杂比为1∶1时制得的催化膜Au-Ce₁Zr₁/FAU具有最好的被还原能力, 更有利于Au的分散与还原; O₂-TPD结果表明, 该样品的氧物种比其它样品上的氧物种活性更高. 更好的被还原性能和更高的氧物种活性使得制备的Au-Ce₁Zr₁/FAU催化膜性能最佳, 在60 ℃时CO转化率与O₂选择性可以同时达到100%, 并且在经过10次热循环测试后仍然可以保持稳定的催化性能.     

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.     

Influence of Electronic Effect on Methane Catalytic Combustion over PdNi/Al2O3

A series of PdNi/Al₂O₃ catalysts with different compositions was prepared by co-reduction method. The influence of Ni amount on the catalytic combustion of methane was studied. X-ray diffractometry and X-ray photo-electron spectroscopy were employed to characterize the dispersion and electronic state of the active phase. Tempe-rature-programmed oxidation was carried out to study the thermal stability affected by Ni doping. It has been demonstrated that Ni addition changed particle size and oxidation state of PdO_x. The results indicate that the promotion of Ni to the Pd/Al₂O₃ resulted from both size effect and electronic effect. In addition, the thermal stability of the Ni-doped catalysts were enhanced.     

Amorphous Boron Dispersed in LaCoO3 with Large Oxygen Vacancies for Efficient Catalytic Propane Oxidation

Unsatisfactory oxygen mobility is a considerable barrier to the development of perovskites for low-temperature volatile organic compounds (VOCs) oxidation. This work introduced small amounts of dispersed non-metal boron into the LaCoO₃ crystal through an easy sol-gel method to create more oxygen defects, which are conducive to the catalytic performance of propane (C₃H₈) oxidation. It reveals that moderate addition of boron successfully induces a high distortion of the LaCoO₃ crystal, decreases the perovskite particle size, and produces a large proportion of bulk Co²⁺ species corresponding to abundant oxygen vacancies. Additionally, surface Co³⁺ species, as the acid sites, which are active for cleaving the C−H bonds of C₃H₈ molecules, are enriched. As a result, the LCB-7 (molar ratio of Co/B=0.93:0.07) displays the best C₃H₈ oxidation activity. Simultaneously, the above catalyst exhibits superior thermal stability against CO₂ and H₂O, lasting 200 h. This work provides a new strategy for modifying the catalytic VOCs oxidation performance of perovskites by the regulation of amorphous boron dispersion.     

不同组成和结构LaMnO_3钙钛矿负载Au催化剂的CO氧化活性

采用乙二醇溶胶-凝胶法制备了计量比LaMnO_3和非计量比LaMn_(1.2)O_3钙钛矿,并利用稀硝酸处理LaMnO_3制备得到LaMnO_3-AE,然后采用沉积沉淀法制备钙钛矿负载Au催化剂,以考察载体的结构和性质对Au的热稳定性以及催化剂活性的影响。通过X射线衍射(XRD)、透射电镜(TEM)、X射线光电子能谱(XPS)和H_2程序升温还原(H_2-TPR)等表征,发现LaMnO_3和LaMn_(1.2)O_3钙钛矿载体虽然有利于Au的分散,但是Au的热稳定性相对较差。相反,经稀硝酸刻蚀的LaMnO_3钙钛矿(LaMnO_3-AE)不利于Au的分散,但是有利于提高Au的热稳定性。在CO氧化反应中,当催化剂在低于500°C焙烧时,LaMn_(1.2)O_3钙钛矿负载Au催化剂的活性要显著高于LaMnO_3和LaMnO_3-AE负载Au催化剂的活性,而当催化剂焙烧温度升高至700°C以上时,LaMnO_3-AE负载Au催化剂却要显著优于LaMnO_3和LaMn_(1.2)O_3钙钛矿负载Au催化剂的活性。     

介孔Fe-Cu复合金属氧化物纳米粉催化剂催化低温CO氧化

以环氧丙烷为凝胶剂,采用简便低廉的无表面活性剂的溶胶-凝胶法制备了一系列不同Cu/Fe摩尔比的高比表面积介孔Fe-Cu复合氧化物纳米粉末。运用微反应器-色谱体系考察了它们在低温CO氧化反应中的催化性能。采用X射线衍射、N2吸附-脱附、热重-差热分析、程序升温还原、傅里叶变换红外光谱和透射电镜对所制样品进行了表征。结果表明,这些介孔Fe-Cu复合氧化物催化剂具有纳米晶结构、窄的孔径分布和高的比表面积,在低温CO氧化反应中表现出高的活性和稳定性。 CuO的添加影响了Fe2O3的结构和催化性能。当CuO含量为15 mol%时,催化剂具有最高的比表面积和催化活性,在低温CO氧化反应中表现出较高的催化稳定性。     

不同载体稳定的纳米金催化剂室温催化氧化甲醛研究

甲醛是一种常见的室内空气污染物,人们针对其消除已经做了大量的研究工作.催化氧化法是脱除挥发性有机物的一种重要方法,能在较低温度下通过催化剂作用将甲醛完全氧化为无毒的CO2和H2O.所用催化剂主要为负载型贵金属催
　　化剂和非贵金属催化剂,但只有担载贵金属Pt或Pd的催化剂可在室温下将甲醛完全氧化,而非贵金属一般则需要较高的温度. Au催化剂是近年来催化领域的一个研究热点,但是关于纳米Au催化剂室温消除甲醛的研究较少.本课题组前期研究发现,以可还原性氧化物(CeO2, FeOx)为载体负载的Au催化剂具有优异的室温氧化甲醛活性;并且突破以可还原性载体负载金的传统思路,首次发现“惰性载体”γ-Al2O3,负载的金催化剂在室温、有水条件下具有优异的甲醛氧化活性.本文对比了还原性氧化物(CeO2, FeOx)和非还原性氧化物(Al2O3, SiO2和HSZM-5)载体负载金催化剂,研究了载体氧化还原性质对负载金催化剂在高空速(600000 ml/(g·s))条件下室温催化氧化甲醛的活性和稳定性影响.结果表明,在室温、高空速且相对湿度为50%的条件下, Au/Al2O3催化剂的初活性最高,且较为稳定. Au/SiO2和Au/HZSM-5催化剂的初活性虽然较高,但很快失活.而还原性氧化物载体(CeO2, FeOx)负载的金催化剂初活性较低,但是稳定性较好.通过电镜对负载金催化剂表面Au粒子大小的表征,并将粒子尺寸与负载金催化剂室温氧化甲醛初活性相关联,它与催化氧化甲醛反应速率成线性关系. Au粒子尺寸较小的催化剂(Au/Al2O3和Au/SiO2),在高空速条件下具有更高的氧化甲醛活性,而Au粒子尺寸较大的Au/FeOx催化剂活性较差.载体的氧化还原性质虽然不直接影响Au催化剂初活性,但直接影响催化剂稳定性.由于Au与SiO2或HZSM-5载体的相互作用较弱,导致反应过程中Au粒子聚集长大,使其失活较快;而Au/Al2O3催化剂表面则富含羟基物种,能够与Au形成配体或产生锚定作用,因此反应过程中金粒子没有明显长大.而表面中间物种的沉积并覆盖活性位是负载金催化剂缓慢失活的主要原因.     

Properties of Cu(thd)2 as a precursor to prepare Cu/SiO2 catalyst using the atomic layer epitaxy technique

The new Cu/SiO2 catalyst is developed by the atomic layer epitaxy (ALE) method. The ALE-Cu/SiO2 catalyst with high dispersion and nanoscale Cu particles appears to have very different catalytic properties from those of the typical Cu-based catalysts, which have satisfactory thermal stability to resist the sintering of Cu particles at 773 K. Due to the formation of small Cu particles, the ALE-Cu/SiO2 can strongly bind CO and give high catalytic activity for CO2 converted to CO in the reverse water-gas-shift reaction. The catalytic activity decreases in the order of 2.4% ALE-Cu/SiO2 =... 2% Pt/SiO2 > 2% Pd/SiO2 > 10.3% IM-Cu/SiO2.     

金属磷酸铝分子筛CdAPO-5的合成、结构及催化性能(Ⅰ)

用水热晶化法，以TEAOH（四乙基氢氧化铵）为模板剂会成出了CdAPO-5分子筛晶体。对样品进行XRD、IR、电子探针等分析，确认其具有AIPO4－5型分子筛结构，属六方晶系，并证实金属Cd进入分子筛的结构骨架，同时对其吸附性能、热稳定性及催化活性进行研究，结果表明CdAPO-5分子筛作为催化剂不仅热稳定性好，机械强度高，且对乙炔水合制乙醛、乙醇脱水制乙醚等反应具有良好的催化性能。     

Effect of a precursor on the phase composition and particle size of the active component of Ni-ZrO2 catalytic systems for the oxidation of methane into syngas

The effect the method of preparation has on the formation, phase composition, porous structure, and catalytic properties of the 10% Ni-ZrO₂ system during the partial oxidation of methane into syngas is studied. Stages of the formation of catalysts from precursors and the effect the method of preparation has on the phase composition, particle size, and catalytic properties of the active component during the partial oxidation of methane into syngas are investigated by means of synchronous TG-DTG/DSC and X-ray diffraction. The synthesis of a catalyst precursor via coprecipitation is shown to yield a monophase system with high nickel dispersion, catalytic activity, and stability.     

Enhanced Activity of CuCeO Catalysts for CO Oxidation: Influence of Cu2O and the Dispersion of Cu2O,CuO, and CeO2

CuCeO catalysts prepared by a hydrothermal method with subsequent calcination are tested for the catalytic oxidation of CO. This synthesis method leads to a homogeneous dispersion of Cu₂O, CuO, and CeO₂ in the catalysts. The composition of the catalysts is determined by the molar ratio of the metals, the hydrothermal process, and calcination temperature and influences the catalytic performance. The catalyst containing Cu₂O exhibits high catalytic activity with almost 100 % CO conversion at 105 °C and shows excellent stability with the conversion ratio not decreasing after four months of storage.     

Janus纳米金稳定的Pickering乳液界面催化氧化性能

Janus纳米粒子的结构设计和简易合成是Pickering乳液界面催化的关键. 本文通过在Pickering乳液保护法中操纵共轭亚油酸的自组装、 自交联性和弱还原性, 合成了Janus型自交联吸附胶束修饰的纳米Fe₃O₄ (SCA-Fe₃O₄), 并在其表面原位还原金后, 合成了Janus型催化剂Au-SCA-Fe₃O₄, 考察其同时作为乳化剂和催化剂在乳液界面催化苯甲醇氧化生成苯甲醛的性能. 结果表明, 该Janus纳米粒子的金修饰量(质量分数)仅为0.66%, 兼具乳化性、 催化性和磁响应性. Au-SCA-Fe₃O₄可制备外观稳定(100 μm)和热稳定(90 ℃)的苯甲醇/水型Pickering乳液, 可显著提高互不相溶反应物与催化剂间的接触面积, 使其催化活性达到均匀纳米催化剂的2倍和非乳液催化时的3倍, 其在界面的不可转动性使苯甲醛的选择性高于99.9%, 避免了苯甲醛被过度氧化成苯甲酸.     

Distribution and properties of catalytically active Cu2+ sites in mesoporous MCM-41 modified with Al, Zr, or W ions

The surface of pure mesoporous SiO₂ with an MCM-41 structure has been modified by introducing Al, Zr, or W ions (1 mmol/g). The original and modified materials have been loaded with Cu²⁺ ions. The distribution, properties, and thermal stability of different Cu²⁺ sites have been studied by EPR and IR spectroscopy. The resulting catalysts have been tested for activity in ethane oxidation. The modification of original MCM-41 exerts a very strong effect on the stability of isolated Cu²⁺ ions on the support surface. Among the modified supports, Al-MCM-41 affords the highest thermal stability and degree of dispersion (70–80%) of the copper-containing phase. There is no correlation between the total number of surface Cu²⁺ sites and the catalytic activity. The specific catalytic activity (per Cu²⁺ ion accessible to the reactants) depends strongly on the local structure of the sites. The isolated pentacoordinated Cu²⁺ sites stabilized by the Al-MCM-41 surface show a comparatively high activity in the sample calcined at 520°C. The heat treatment of Cu/Al-MCM-41 at 650–750°C reduces the specific activity of the catalytic sites by a factor of ～20 without sintering the copper phase, as in the case of CuHZSM-5 zeolite. The least dispersed copper phase, which is observed in the original MCM-41 and likely consists of aggregates of weakly interacting Cu²⁺ ions, exhibits the highest specific activity and thermal stability. In the case of Cu/W-MCM-41, heat treatment causes both the sintering of copper particles and a decrease in the specific activity of the surface Cu²⁺ ions.     

High Electrocatalytic Activity of Pt–Pd Binary Spherocrystals Chemically Assembled in Vertically Aligned TiO2 Nanotubes

To obtain noble metal catalysts with high efficiency, long‐term stability, and poison resistance, Pt and Pd are assembled in highly ordered and vertically aligned TiO₂ nanotubes (NTs) by means of the pulsed‐current deposition (PCD) method with assistance of ultrasonication (UC). Here, Pd serves as a dispersant which prevents agglomeration of Pt. Thus Pt–Pd binary catalysts are embed into TiO₂ NTs array under UC in sunken patterns of composite spherocrystals (Sps). Owing to this synthesis method and restriction by the NTs, the these catalysts show improved dispersion, more catalytically active sites, and higher surface area. This nanotubular metallic support material with good physical and chemical stability prevents catalyst loss and poisoning. Compared with monometallic Pt and Pd, the sunken‐structured Pt–Pd spherocrystal catalyst exhibits better catalytic activity and poison resistance in electrocatalytic methanol oxidation because of its excellent dispersion. The catalytic current density is enhanced by about 15 and 310 times relative to monometallic Pt and Pd, respectively. The poison resistance of the Pt–Pd catalyst was 1.5 times higher than that of Pt and Pd, and they show high electrochemical stability with a stable current enduring for more than 2100 s. Thus, the TiO₂ NTs on a Ti substrate serve as an excellent support material for the loading and dispersion of noble metal catalysts.     

A Novel Cu-Mo／ZSM-5 Catalyst for NOx Catalytic Reduction with Ammonia

The Cu-Mo/ZSM-5 catalysts with different Cu/Mo ratios were prepared by wet impregnation method, and their catalytic performance for selective catalytic reduction of NOx was studied. The results showed that Cu-Mo/ZSM-5 is a very effective catalyst for NOx catalytic reduction with ammonia, especially when Cu/Mo molar ratio is about 1.5. It not only exhibited the extremely high catalytic activity, but also showed good stability for 02. The bulk phase structure of Cu-Mo/ZSM-5 catalysts was determined by XRD technique, and the results indicated that there is a maximum dispersion for Cu species when Cu/Mo molar ratio is 1.5, and an interaction between Cu and Mo along with HZSM-5 may be present in Cu-Mo/ZSM-5, which may possibly result in a special structure favorable for the catalytic reduction of NOx over Cu-Mo/ZSM-5 catalyst.     

焙烧温度对柴油车氧化催化剂Pt-Pd-（x）ZrO2/Ce0.3Zr0.7O2-Al2O3性能的影响

制备了氧化铝、铈锆固溶体复合氧化物负载铂、钯的双金属催化剂Pt-Pd/ Ce0.3Zr0.7O2-Al2O3,并添加3% ZrO2助剂改性,用于柴油车尾气中CO、HC和NO的催化氧化,其中贵金属负载量仅为0.68 wt%。考察了制备过程中焙烧温度对催化剂性能的影响。催化剂活性评价结果表明,与未添加ZrO2的催化剂比较。添加ZrO2明显提高了催化剂的低温氧化活性,而且焙烧温度对催化剂的氧化性能有较大影响。焙烧温度为800 ?C时,CO和C3H6的起燃温度最低,分别为168、189 ?C,焙烧温度为700 ?C时,NO转化为NO2的转化率最高,最大转化率为36%,具有较好的热稳定性。通过XRD、N2吸附-脱附、CO化学吸附、XPS、H2-TPR等表征手段考察了催化剂物理化学性质随焙烧温度的变化情况,并分析了与催化剂活性之间的关系,得到贵金属分散度、表面化学吸附氧含量、催化剂的还原性质对氧化性能有重要影响,发挥协同作用。进而可以通过优化焙烧温度提升柴油车氧化催化剂性能,对提高工业应用柴油车尾气后处理系统的净化效率有重要意义。     

Thermal transformations of Cu–Mg (Zn)–Al(Fe) hydrotalcite-like materials into metal oxide systems and their catalytic activity in selective oxidation of ammonia to dinitrogen

Layered double hydroxides (LDHs) containing Mg²⁺, Cu²⁺ or Zn²⁺ cations in the Me^II positions and Al³⁺ and Fe³⁺ in the Me^III positions were synthesized by co-precipitation method. Detailed studies of thermal transformation of obtained LDHs into metal oxide systems were performed using high temperature X-ray diffraction in oxidising and reducing atmosphere, thermogravimetry coupled with mass spectrometry and temperature-programmed reduction. The LDH samples calcined at 600 and 900 °C were tested in the role of catalysts for selective oxidation of ammonia into nitrogen and water vapour. It was shown that all copper congaing samples presented high catalytic activity and additionally, for the Cu–Mg–Al and Cu–Mg–Fe hydrotalcite samples calcined at 600 °C relatively high stability and selectivity to dinitrogen was obtained. An increase in calcination temperature to 900 °C resulted in a decrease of their catalytic activity, possibly due to formation of well-crystallised metal oxide phases which are less catalytically active in the process of selective oxidation of ammonia.