Au/γ-MnO2催化剂催化无溶剂条件下甲苯氧化反应

采用氧化还原法制备了α, δ, γ-MnO₂载体, 采用原位还原法制备了Au负载量为0.5%-3.0%的Au/γ-MnO₂催化剂, 并采用X射线衍射、扫描电镜、透射电镜和N₂物理吸附等手段对其进行了表征. 透射电镜照片表明Au/γ-MnO₂催化剂中Au颗粒的大小约为10 nm. 采用无溶剂存在下的甲苯氧化反应测试所制备样品的催化活性. 结果表明, 甲苯转化率随着Au负载量的增加而增大. 这是由于Au颗粒数量增多, 尺寸减小的缘故. 同时, 负载Au颗粒对苯甲醛具有较高的选择性. Au/γ-MnO₂催化剂具有良好的重复使用性.     

SnO2负载Au和M-Au(M=Pt,Pd)催化剂及其低温催化氧化CO性能

以SnO₂为载体, 采用沉积沉淀法(DP)、共沉淀法(CP)和浸渍法(IM)制备了金负载Au/SnO₂催化剂, 同时采用沉积沉淀法制备了M-Au/SnO₂(M=Pd, Pt)双金属负载催化剂. 通过X射线衍射(XRD)、BET比表面积测定、透射电镜(TEM)和X射线光电子能谱(XPS)等技术对样品进行表征, 并测定其对CO的催化活性. 结果表明: 与CP法和IM 法相比, DP法制备的Au/SnO₂-DP 催化剂, Au 颗粒(<5 nm)较小, 分布均匀; Au/SnO₂-DP 中的Au 是以金属态Au0存在, 而Au/SnO₂-CP 和Au/SnO₂-IM 中, 金以Au⁰和Au³⁺的混合价态存在, 在Au/SnO₂-DP和M-Au/SnO₂中的Au、Pt、Pd和SnO₂之间存在相互作用; Au/SnO₂-DP 催化性能明显优于Au/SnO₂-CP 和Au/SnO₂-IM. Au与Pt 和Pd的双金属复合催化剂催化活性明显提高. 不同方法制备Au/SnO₂催化活性的差别主要是由于Au颗粒大小和Au氧化态的不同而产生. 而M-Au/SnO₂活性提高, 可能是由于Au与Pt 和Pd之间的相互作用.     

Ni-Al复合氧化物/介孔杭锦2#土负载Au催化剂制备及其CO氧化催化性能

采用导向剂共沉淀-水热法合成不同复合量3Ni-Al类水滑石（LDH）/酸化杭锦2^#土载体前驱物.以液相还原-焙烧法制备不同Au负载量的Ni-Al复合氧化物/介孔杭锦2^#土负载Au催化剂.采用电感耦合等离子体发射光谱（ICP-AES）、原子吸收光谱（AAS）、N₂物理吸附-脱附、X射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、紫外-可见漫反射光谱（UV-Vis DRS）、X射线光电子能谱（XPS）等手段对催化剂进行表征;并考察其催化CO氧化活性及稳定性.结果表明,3Ni-Al LDH在酸化杭锦2^#土上复合均匀;其负载Au后经500℃空气气氛焙烧,催化剂具有介孔结构,Au颗粒分散均匀、平均粒径小于10 nm;Ni-Al LDH复合量增加有利于纳米Au分散并抑制其粒径增大,且纳米Au与载体间存在较强相互作用;随Ni-Al LDH复合量和Au负载量增加,负载Au催化剂催化活性提高,当Ni-Al LDH复合量15%（Ni 3.47%）,Au负载量3%时,所得负载Au催化剂性能最佳：T₅₀为48℃,80℃时CO转化率大于90%,180℃连续反应10 h,CO转化率保持100%,空气放置110 d后,虽然其低温活性有所下降,但120℃时,仍可实现CO转化率大于90%.     

焙烧温度对“软-硬”模板法制备的Pd/Ce0.65Zr0.35O2三效催化性能的影响

采用"软-硬"模板法制备了具有高热稳定性的Ce_0.65Zr_0.35O₂（CeZr）。考察了制备过程中焙烧温度对Ce_0.65Zr_0.35O₂及其负载的单Pd三效催化剂（TWC）性能的影响。对样品进行了X射线衍射、比表面、拉曼光谱、X射线光电子能谱、储氧性能和H₂程序升温还原性能测试。结果表明：焙烧温度显著影响催化剂的结构和性能。随着焙烧温度的增加，Ce_0.65Zr_0.35O₂的比表面下降，但在1 000℃焙烧的样品比表面为61 m²·g^-1，显著高于同温度下直接在空气中焙烧的样品。由于高温导致了物相重组，Ce_0.65Zr_0.35O₂的储氧量和还原性能随着焙烧温度的增加而提升。由于高温烧结导致Pd分散性的下降，其负载的催化剂的还原性能随着焙烧温度的增加而下降，从而最终导致催化剂活性的降低。但在"软-硬"模板法中1 000℃焙烧的样品负载的催化剂依然显示出很好的三效催化性能，该催化剂上C₃H₈、CO和NO的起燃温度分别为274、175和133℃，显著低于同温度下空气中直接焙烧的样品负载的催化剂。催化剂的氧化还原性能和Pd的分散性是影响催化活性的主要因素。     

碳纳米管/SnO2复合电极的制备及其电催化性能研究

采用液相沉积法制备碳纳米管(CNTs)/SnO₂复合材料, 并制备成电极, 分别与石墨/SnO₂及活性炭/SnO₂复合电极比较, 考察电催化降解有机废水的性能. 由于CNTs高的比表面积及优良的导电性能, 结合SnO₂良好的催化活性, CNTs/SnO₂复合电极电催化降解有机废水性能优越. 研究发现, CNTs的预处理情况、SnO₂负载量以及煅烧温度对复合电极的电催化性能有重要影响. 当功能化CNTs负载40% SnO₂, 煅烧温度600 ℃时, 所得CNTs/SnO₂复合电极电催化降解有机废水的能力是纯CNTs电极的2倍. 最后, 初步探讨了CNTs/SnO₂复合电极电催化降解有机废水的机理.     

双金属核壳结构负载型Au@Ag/TiO2催化剂的制备及表征

利用溶胶法制备了Au核Ag壳(Au@Ag)结构复合纳米粒子,用粉末-溶胶法和水热合成法使其负载于TiO₂纳米粒子上,利用紫外-可见吸收光谱﹑X射线粉末衍射﹑透射电子显微镜对复合结构材料进行了结构表征,并对其光催化消除臭氧的性能进行了研究。结果表明,制备方法、Au/Ag化学计量比及金属负载量等对光催化消除臭氧的活性均有很大影响。采用粉末-溶胶法制备的1%-Au@Ag/TiO₂(n_Au/n_Ag=1∶3)催化剂,由于TiO₂表面沉积的Au@Ag金属颗粒尺寸小且分散度高,而且1%的金属担载量有利于光生电子空穴的有效分离,光催化消除臭氧的活性最高。     

基于SnO2为修饰层的Au-Pt / SnO2 / Au复合电极研究

用真空镀膜法在Au电极上沉积SnO₂薄膜，在HAuCl₄和H₂PtCl₄的混合溶液中利用直接还原法，将Au-Pt双金属纳米颗粒组装在SnO₂ / Au电极上，得到Au-Pt / SnO₂ / Au复合电极。采用SEM、TEM、XPS及CV曲线测定对Au-Pt / SnO₂ / Au复合电极进行了表征。结果表明:复合电极上双金属纳米颗粒分布均匀，粒子粒径约为25 nm左右。SnO₂作为修饰层以配位键与双金属纳米粒子结合。Au-Pt / SnO₂ / Au复合电极具有良好对甲醇氧化的电化学性能。     

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.     

不同载体对负载型氧化钨催化剂在己二酸合成反应中的结构及性能影响

以SBA-15、六角介孔二氧化硅（HMS）和SnO₂为载体,通过浸渍法合成了含钨负载型催化剂,并考察了三种催化剂在环氧环己烷选择氧化制备己二酸反应中的催化性能. 通过X射线衍射（XRD）,透射电镜/场发射透射电镜（TEM/FETEM）,紫外-可见漫反射光谱（UV-Vis DRS）,拉曼（Raman）光谱,X射线光电子能谱（XPS）以及傅里叶变换红外（FTIR）光谱等手段对各种催化剂的结构进行表征. 结果表明,载体与催化剂的性能有密切的关系. 以SnO₂为载体的WO₃/SnO₂催化剂活性最高,其次是WO₃/HMS催化剂,WO₃/SBA-15 催化剂的活性最差.XRD 分析显示WO₃/SnO₂催化剂中氧化钨物种的晶化程度最低,TEM 和XPS 结果表明氧化钨物种在WO₃/SnO₂催化剂表面高度分散并且粒径尺寸很小（约2 nm）,UV-Vis DRS结果表明在WO₃/SnO₂催化剂中存在孤立[WO₄]四面体和低聚态的钨物种,这些物种的存在可能是WO₃/SnO₂催化剂具有高活性的主要原因. 此外,WO₃/SnO₂催化剂可以重复使用多次,6 次反应后己二酸（AA）得率仍然保持在80%以上,说明氧化钨物种与SnO₂载体间存在强烈的相互作用,从而提高了催化剂的稳定性.     

SO42-/SnO2-Fe2O3固体酸催化下的环酮Baeyer-Villiger氧化反应及缩合反应

采用共沉淀的方法制备了不同Fe 掺杂量的SO₄^2-/SnO₂-Fe₂O₃固体超强酸催化剂. 利用傅里叶变换红外(FTIR)光谱, 粉末X射线衍射(XRD), N₂吸附-脱附实验(BET), 热重(TG)分析和扫描电镜(SEM)等方法对样品进行了表征. 考察了所得催化剂对4-叔丁基环己酮与乙二醇缩合反应的催化性能. 实验结果表明, 与未经过掺杂改性的SO₄^2-/SnO₂固体酸催化剂相比, 改性后催化剂的催化性能得到了改善. 研究了以Fe/Sn 摩尔比为0.5的SO₄^2-/SnO₂-Fe₂O₃固体酸为催化剂, 部分醛酮类化合物与乙二醇及1,2-丙二醇的缩合反应. 考察了反应时间、催化剂用量等因素对反应的影响. 同时, 将所得催化剂应用于环酮Baeyer-Villiger 氧化反应中, 催化剂表现出良好的催化活性, 且催化剂具有一定的循环使用性.     

Gold, palladium and gold–palladium supported on silica catalysts prepared by sol–gel method: synthesis, characterization and catalytic behavior in the ethanol steam reforming

Noble-metal-based catalysts supported on silica (Au/SiO₂, Pd/SiO₂ and Au–Pd/SiO₂) were prepared by the sol–gel method and were evaluated in the steam reforming of ethanol for hydrogen production. The catalysts were characterized by N₂ physisorption (BET/BJH methods), X-ray diffraction, temperature programmed reduction analysis, H₂ chemisorption, atomic absorption spectrophotometry and Raman spectroscopy. The structural characterization of the Au- and Pd-containing catalysts after calcination showed that the solids are predominantly formed by Au⁰, Pd⁰ and PdO species and was observed that the metallic Pd dispersion diminished in the presence of Au⁰. The results revealed that the catalytic behavior could be influenced by the experimental conditions and the nature of the catalyst employed. The Pd/SiO₂ catalyst showed the best performance among the catalysts tested at the highest reaction temperature (600 °C) due to the more effective action of the metallic active phase, which covers a greater area in this sample. At this same reaction temperature, the Au–Pd/SiO₂ catalyst showed a significant deactivation, probably due to the lower Pd dispersion presented by this catalyst.     

Characteristics of Au/MgxAlO hydrotalcite catalysts in CO selective oxidation

Gold catalysts, supported on a solid base of Mg_xAlO hydrotalcite, were prepared by a modified deposition precipitation method for CO selective oxidation. The preparation parameters and pretreatment of the catalysts were investigated. The pH and the HAuCl₄ concentration in the initial solution, and the Mg/Al molar ratio of Mg_xAlO affected the pH in the final solution and determined the actual gold loading of the catalyst. The calcination temperatures of the Mg_xAlO support and the Au/Mg_xAlO catalyst dominated the Au³⁺/Au⁰ ratio on the catalyst. The pretreatment of the catalyst as well as the gold loading and the Au³⁺/Au⁰ ratio, critically determined the activity of the catalyst for CO selective oxidation. Based on XPS and in situ DR-FTIR analyses, a mechanism for CO selective oxidation on 2%Au/Mg₂AlO was proposed. The hydroxyl group on Mg₂AlO also participated in the reaction.     

Influence of pretreatment conditions on low-temperature CO oxidation over Au/MOx/Al2O3 catalysts

Composite oxide MO_x/Al₂O₃ supported gold catalysts for low-temperature CO oxidation were prepared and investigated. The presence of transition metal oxide was proved to be beneficial to the improvement of catalytic performance of Au/Al₂O₃ catalysts for low-temperature CO oxidation. Furthermore, the influence of various pretreatment conditions on Au/MO_x/Al₂O₃ catalysts was studied carefully. The image of TEM showed that gold catalyst with small gold particles only in the form of a fine dispersion exhibited highly catalytic activity. The XPS, Fourier transform infrared (FTIR) spectroscopy characterization results of Au/FeO_x/Al₂O₃ catalyst showed that gold catalysts having partially oxidized gold species have the best catalytic performance. One possible pathway for CO oxidation on Au/FeO_x/Al₂O₃ catalyst is that the CO adsorbed on gold particles reacts with adsorbed oxygen, which is possible to occur on oxygen vacancies on the support or at the metal–support interface.     

Catalytic performance and structural characterization of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation

The preparation and catalytic activity of ferric oxide and its composite oxides supported gold catalysts for low-temperature CO oxidation were investigated detailedly, and characterized extensively by XRD, XPS, TPR, EC and XAFS techniques. It was found that containing highly dispersed Au of partially oxidized state, these nano-structured oxides supported Au/Fe2O3 and Au/NiFe2O4 catalysts had higher low-temperature activities. The possible catalytic active center is the gold of partially oxidized state (Auζ+).     

Characterization of Au-Rh/TiO2 catalysts by CO adsorption; XPS, FTIR and TPD experiments

On X-ray photoelectron spectra of the Au-Rh/TiO₂ catalysts the position of Au4f peak was practically unaffected by the presence of rhodium, the peak position of Rh3d, however, shifted to lower binding energy with the increase of gold content of the catalysts. Rh enrichment in the outer layers of the bimetallic crystallites was experienced. The bands due to Au⁰-CO, Rh⁰-CO and (Rh⁰)₂-CO were observed on the IR spectra of bimetallic samples, no signs for Rh⁺-(CO)₂ were detected on these catalysts. The results were interpreted by electron donation from titania through gold to rhodium and by the higher particle size of bimetallic crystallites.     

小麦粉衍生中孔氮掺杂颗粒炭负载金催化剂用于乙炔氢氯化反应（英文）

聚氯乙烯是五大工程塑料之一,在国民经济中占有重要的地位.基于中国富煤少油缺气的能源格局,我国主要采用基于煤化工的电石法氯乙烯生产工艺,但该工艺必须采用氯化汞催化剂,受到国际限汞公约的影响,无汞催化剂的开发迫在眉睫.其中炭负载金催化剂在该反应中活性最高,近几年来取得了较大进展,有望实现产业化.氮掺杂的炭材料在诸多反应中展现了较好的性能,其负载金属催化剂可以有效提高金属的分散度及稳定性,成为近几年多相催化领域的一个研究热点.最近我们课题组报道了一种氮掺杂中孔成型的制备方法:以小麦粉为原料,通过直接炭化法制备了氮掺杂中孔成型炭,这种氮掺杂中孔成型炭作为无汞催化剂在乙炔氢氯化反应中显示出了优异的催化性能.小麦粉衍生的氮掺杂中孔成型炭具有成型容易.原料价廉易得、易于放大生产等优点,是优选的工业化催化剂的载体.本文以这种氮掺杂的成型炭为载体制备了负载型金催化剂,研究其催化乙炔氢氯化性能.结果表明,氮的掺杂使得中孔炭负载金(Au/N-MC)催化剂上乙炔氢氯化活性明显提高.在氯化氢/乙炔比例1.1、反应温度180℃、乙炔空速600 h~(-1)的条件下,Au/N-MC上的乙炔转化率为50%,是Au/MC催化剂活性的2倍.通过对催化剂的表征发现,氮的掺杂能有效地锚定Au/N-MC催化剂中活性组分Au~(3+),抑制催化剂制备过程中Au~(3+)还原为Au~0,从而提高催化剂活性和稳定性.小麦粉衍生的氮掺杂中孔炭的原料廉价易得,生产工艺简单,易成型,也容易实现工业化生产,是负载型金属催化剂的优良载体,其负载的无汞催化剂性能优越,有望取代电石法氯乙烯产业的汞催化剂,成为新一代无汞催化剂.     

Carbon Monoxide Oxidation by Polyoxometalate‐Supported Gold Nanoparticulate Catalysts: Activity,Stability, and Temperature‐ Dependent Activation Properties

Nanoparticulate gold supported on a Keggin‐type polyoxometalate (POM), Cs₄[α‐SiW₁₂O₄₀]⋅n H₂O, was prepared by the sol immobilization method. The size of the gold nanoparticles (NPs) was approximately 2 nm, which was almost the same as the size of the gold colloid precursor. Deposition of gold NPs smaller than 2 nm onto POM (Au/POM) was essential for a high catalytic activity for CO oxidation. The temperature for 50 % CO conversion was −67 °C. The catalyst showed extremely high stability for at least one month at 0 °C with full conversion. The catalytic activity and the reaction mechanism drastically changed at temperatures higher than 40 °C, showing a unique behavior called a U‐shaped curve. It was revealed by IR measurement that Au^δ+ was a CO adsorption site and that adsorbed water promoted CO oxidation for the Au/POM catalyst. This is the first report on CO oxidation utilizing Au/POMs catalysts, and there is a potential for expansion to various gas‐phase reactions.     

Nanoceria Supported Gold Catalysts for CO Oxidation

Two types of CeO₂ nanocubes (average size of 5 and 20 nm, respectively) prepared via the hydrothermal process were selected to load gold species via a deposition‐precipitation (DP) method. Various measurements, including X‐ray diffraction (XRD), Raman spectra, high resolution transmission electron microscopy (HRTEM), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and temperature‐programmed reduction by hydrogen (H₂‐TPR), were applied to characterize the catalysts. It is found that the sample with ceria size of 20 nm (Au/CeO₂‐20) was covered by well dispersed both Au³⁺ and Au^δ+ (0 < δ < 1). For the other sample with ceria size of 5 nm (Au/CeO₂‐5), Au³⁺ is the dominant gold species. Au/CeO₂‐20 performed better catalytic activity for CO oxidation because of the strong CO adsorption of Au^δ+ in the catalysts. The catalytic activity of Au/CeO₂‐5 was improved due to the transformation of Au³⁺ to Au^δ+. Based on the CO oxidation and in situ DRIFTS results, Au^δ+ is likely to play a more important role in catalyzing CO oxidation reaction.     

Controllable Conversion of CO2 on Non-Metallic Gold Clusters

Gold nanoparticles in metallic or plasmonic state have been widely used to catalyze homogeneous and heterogeneous reactions. However, the catalytic behavior of gold catalysts in non-metallic or excitonic state remain elusive. Atomically precise Au_n clusters (n=number of gold atoms) bridge the gap between non-metallic and metallic catalysts and offer new opportunities for unveiling the hidden properties of gold catalysts in the metallic, transition regime, and non-metallic states. Here, we report the controllable conversion of CO₂ over three non-metallic Au_n clusters, including Au₉, Au₁₁, and Au₃₆, towards different target products: methane produced on Au₉, ethanol on Au₁₁, and formic acid on Au₃₆. Structural information encoded in the non-metallic clusters permits a precise correlation of atomic structure with catalytic properties and hence, provides molecular-level insight into distinct reaction channels of CO₂ hydrogenation over the three non-metallic Au catalysts.