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。     

Iron-catalyzed propylene epoxidation by nitrous oxide: studies on the effects of alkali metal salts

SBA-15-supported iron catalysts with and without alkali metal salt modifications were studied for propylene oxidation by nitrous oxide. The reaction route could be dramatically changed from allylic oxidation to epoxidation by modification of the FeOx/SBA-15 catalyst with alkali metal salts. The KCl-1 wt % FeOx/SBA-15 (K/Fe = 5) catalyst exhibited the best catalytic performances for propylene epoxidation, over which ca. 50% propylene oxide selectivity could be gained at a 10% propylene conversion at 648 K. Characterizations with diffuse reflectance UV-Vis, XANES, and Raman spectroscopic techniques revealed that the modification with KCl increased the dispersion of the iron species and changed the local coordination of iron into a tetrahedral configuration on the inner surface of SBA-15. This tetrahedrally coordinated iron site, which was probably stabilized by potassium ions, was proposed to account for the epoxidation of propylene by nitrous oxide. At the same time, the reactivity of lattice oxygen was inhibited, and the acidity of the FeOx/SBA-15 was eliminated. These changes should also contribute to the increase in the selectivity to propylene oxide. The counteranions in the alkali metal salts exerted a significant influence on the catalytic behaviors probably via an electronic effect.     

Fe-K/AC催化氧化脱硫剂制备及反应机理研究

采用正交实验法制备了负载铁、钾的活性炭(Fe-K/AC)热煤气催化氧化脱硫剂,考察了活性组分铁、钾含量、二价铁和三价铁比例、煅烧温度对催化氧化脱硫反应活性的影响。由正交实验极差分析可知,各因素影响程度依次为:钾含量>铁含量>煅烧温度> Fe²⁺/Fe³⁺,最优制备条件为,铁含量0.5%、钾含量5.0%、煅烧温度600 ℃、Fe²⁺/Fe³⁺比0.5。通过对脱硫剂的孔隙结构和表面形貌分析可知,活性炭表面负载的铁金属氧化物具有催化氧化硫化氢生成单质硫的活性,碱金属氧化物具有协同作用,可以改变表面酸碱性,促进硫化氢的催化转化,但过高的金属氧化物负载量会阻塞孔道,减小反应比表面积,从而降低脱硫剂的反应活性。     

The effect of the conditions for the preparation of iron oxide nanoparticles on their catalytic characteristics in the oxidation of CO

The catalytic characteristics of systems prepared by mechanically mixing iron oxide nanoparticles, produced in the thermolysis of carboxylate complexes at 300–750°C, with aluminum oxide in the oxidation of CO were studied. It was shown that increase in the size of the iron oxide nanoparticles leads to decrease in the catalytic activity of the samples as a result of their different structural and textural characteristics, which change in relation to the synthesis conditions. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 300–305, September–October, 2006.     

Effect of confinement in carbon nanotubes on the activity of Fischer-Tropsch iron catalyst

Following our previous findings that confinement within carbon nanotubes (CNTs) can modify the redox properties of encapsulated iron oxides, we demonstrate here how this can affect the catalytic reactivity of iron catalysts in Fischer-Tropsch synthesis (FTS). The investigation, using in situ XRD under conditions close to the reaction conditions, reveals that the distribution of iron carbide and oxide phases is modulated in the CNT-confined system. The iron species encapsulated inside CNTs prefer to exist in a more reduced state, tending to form more iron carbides under the reaction conditions, which have been recognized to be essential to obtain high FTS activity. The relative ratio of the integral XRD peaks of iron carbide (Fe(x)C(y)) to oxide (FeO) is about 4.7 for the encapsulated iron catalyst in comparison to 2.4 for the iron catalyst dispersed on the outer walls of CNTs under the same conditions. This causes a remarkable modification of the catalytic performance. The yield of C5+ hydrocarbons over the encapsulated iron catalyst is twice that over iron catalyst outside CNTs and more than 6 times that over activated-carbon-supported iron catalyst. The catalytic activity enhancement is attributed to the effect of confinement of the iron catalyst within the CNT channels. As demonstrated by temperature-programmed reduction in H2 and in CO atmospheres, the reducibility of the iron species is significantly improved when they are confined. The ability to modify the redox properties via confinement in CNTs is expected to be of significance for many catalytic reactions, which are highly dependent on the redox state of the active components. Furthermore, diffusion and aggregation of the iron species through the reduction and reaction have been observed, but these are retarded inside CNTs due to the spatial restriction of the channels.     

Fe2O3/CNT催化湿法H2O2氧化苯酚

通过化学沉积法和热处理得到多壁碳纳米管负载Fe2O3催化剂 Fe2O3/CNT, Fe2O3的负载质量分数约为15.1%,XRD表征显示,负载的Fe2O3存在α和γ这2种晶型。考察了Fe2O3/CNT催化湿式H2O2氧化去除废水中苯酚催化性能,通过苯酚的去除率及反应过程中催化剂活性组分的溶出总量,研究了催化剂制备过程中添加聚乙烯醇对催化剂性能的影响。在苯酚和H2O2初始浓度分别为350和1 500 mg/L、催化剂投加量为1.0 g/L、温度80 ℃条件下,经过240 min的反应,苯酚去除率达100％,COD去除率为86.1％。     

Ferritin as a Novel Catalyst for Selective Hydroxylation of Phenol

Ferritin molecule consists of a spherical polypeptide shell (apoferritin) surrounding a nanometeric inorganic core of iron oxide ferihydrite. It has the ability to sequester and store iron in a bio-available form by mobilizing or immobilizing iron through its narrow channels in the stable polypeptide quaternary structure^[1,2].Our original idea was to explore the catalytic activity of the inner nano-sized, iron oxide core. It was also hoped that the spherical hollow polypeptide shell with channels might act as a biological-molecular, sieve, displaying some kinds of shape and size selectivity.     

Effects of oxidation pretreatment temperature on Kovar used as CO_2 reforming catalyst

The effect of oxidation pretreatment temperature(500 ~ 1 000 ℃) on the catalytic activity of Kovar applied on hydrocarbon CO2reforming was examined. Catalytic performance evaluation using tetradecane at 800 ℃ with 70 μmol/s CO2revealed 700 and 1 000 ℃ as the best pre-oxidation temperature in producing CO and H2,respectively. XRD and SEM-EDX analyses showed that a separate metal oxide layer composed of iron oxide(Fe2O3and F3O4),nickel,cobalt,and possibly their respective oxides started to form when oxidation was conducted at 700 ℃ or higher.The presence of iron enhanced the stability of nickel in the structure while the compact structure of Fe3O4resulted into the formation of a thick and rigid metal oxide layer on the surface of the Kovar tube. The strong physical bond between the metal oxide layer and Kovar tube provided the catalyst good mechanical strength and consequently good catalytic activity.     

无定形氧化铁层在纳米多孔BiVO4的光电化学分解水反应中的作用

通过"人工光合成"过程,将太阳能转化成氢能的形式加以存储和利用,是替代传统化石能源的清洁能源的制备有效途径.其中,光电化学分解水是氢能制备的最有潜力的路径之一.n型BiVO4由于具有丰富的储量、较窄的带隙以及合适的能带位置,被称为光电化学领域的研究热点.然而,未修饰的BiVO4光阳极性能并不理想,主要原因在于载流子复合严重、导电性差以及表面催化动力学低等性质的制约.科研工作者们针对这些方面已进行了非常多的研究,例如与电子传输层的复合、产氧电催化剂的担载以及异质结的构建等.其中表面动力学和电荷分离的同时提升是更理想的改善BiVO4光阳极性能的方法.我们在上述研究基础上,采用光化学沉积法在纳米多孔BiVO4电极表面担载无定形氧化铁层,将电极在1.23 V vs.RHE电位下的光电流提升至2.52 mA/cm2,是初始光电化学性能的3倍.采用间歇光照计时电流(i-t)测试,电化学交流阻抗谱(EIS),X射线光电子能谱(XPS),原位和非原位的X射线精细结构能谱(in-situ and ex-situ XAFS)等表征手段研究了无定形氧化铁层的成分和光电化学反应过程中的价态变化,从而分析出光电化学性能提升的原因.间歇光照i-t测试和EIS测试结果表明,无定形氧化铁沉积在BiVO4使电荷累积减少,复合率降低.XPS测试结果发现无定形氧化铁层存在少量的二价铁成分.通过原位XAFS测试发现,BiVO4/FeOx电极中Fe原子的价态在光照和施加外加偏压条件下会有价态的升高,而撤去光照和偏压后Fe原子的价态状态与最初非原位的测试结果重合.这样的结果证明了无定型氧化铁层在光电化学反应过程中由于二价铁成分的存在,能够很好的通过价态改变实现空穴的吸附和传输,即吸附空穴,被空穴氧化成三价或四价,同时结合自身电催化活性,促进表面分解水反应的进行.而水的氧化反应结束时,则伴随着二价铁离子的再生成.这种反应机理为开发更高效的电催化剂,匹配光电极使用,有着重大的指导意义.     

A Case of Strong Metal–Support Interactions: Combining Advanced Microscopy and Model Systems to Elucidate the Atomic Structure of Interfaces

A symbiosis of advanced scanning probe and electron microscopy and a well‐defined model system may provide a detailed picture of interfaces on nanostructured catalytic systems. This was demonstrated for Pt nanoparticles supported on iron oxide thin films which undergo encapsulation by supporting oxide as a result of strong metal–support interactions.     

高分散费—托合成铁／活性炭催化剂的研究：Ⅴ.锰的助剂作用

使用原位穆斯堡尔谱和微型反应器考察了物相、锰含量和制备方法对Fe-Mn/AC催化剂F-T反应性的影响,并讨论了Fe-Mn/AC催化剂的表面结构及其与F-T反应性的关系。对于Fe-Mn/AC催化剂,将铁还原到金属态时具有很高的活性和对气态烯烃和高碳烃的选择性,锰含量对催化剂的活性和选择性影响不大;影响催化剂选择性的主要是受制备制约的铁-锰在活性炭载体表面的结构形态,对此我们提出了模型,只有当铁-锰处于高分散状态,作为助剂锰才能改善催化剂对气态烯烃和高碳烃的选择性,否则锰反而起不利的作用。     

氧化铁负载铂纳米簇催化卤代硝基苯本体氢化性质研究

复相金属催化剂中的载体效应研究具有重要意义。我们以结构不同的氧化铁载体吸附"非保护型"Pt金属纳米簇制备了具有相同Pt纳米簇的Pt/Fe_3O_4、Pt/γ-Fe_2O_3和Pt/α-Fe_2O_3催化剂,考察了其在无溶剂条件下(本体条件)催化邻氯硝基苯(o-CNB)选择性氢化反应的性能,发现三种铂/氧化铁催化剂的催化选择性远高于商购铂/碳催化剂,Pt/γ-Fe_2O_3和Pt/α-Fe_2O_3的催化选择性明显高于Pt/Fe_3O_4,而Pt/Fe_3O_4的催化活性较Pt/α-Fe_2O_3高50%。铂/氧化铁对不同卤代硝基苯的本体选择性氢化反应表现出优良的催化性能,相应卤代苯胺产物的选择性均可达到99%以上。考察了温度、氢气压力对Pt/Fe_3O_4催化o-CNB本体氢化性能的影响。本工作为理解氧化铁负载金属纳米簇催化剂的特殊催化性质,进而发展高效金属纳米簇基催化体系提供了新的基础。     

Promoted aerobic oxidation of benzyl alcohol on CNT supported platinum by iron oxide

The catalytic activity of Pt/CNT for benzyl alcohol aerobic oxidation was remarkably improved by decorating iron oxide on Pt nanoparticles, and electrochemical measurements evidenced the enhanced activation of oxygen and benzyl alcohol at the FeO(x)/Pt interface.     

Shedding Light Onto the Nature of Iron Decorated Graphene and Graphite Oxide Nanohybrids for CO2 Conversion at Atmospheric Pressure

We report on the design and testing of new graphite and graphene oxide-based extended π-conjugated synthetic scaffolds for applications in sustainable chemistry transformations. Nanoparticle-functionalised carbonaceous catalysts for new Fischer Tropsch and Reverse GasWater Shift (RGWS) transformations were prepared: functional graphene oxides emerged from graphite powders via an adapted Hummer's method and subsequently impregnated with uniform-sized nanoparticles. Then the resulting nanomaterials were imaged by TEM, SEM, EDX, AFM and characterised by IR, XPS and Raman spectroscopies prior to incorporation of Pd(II) promoters and further microscopic and spectroscopic analysis. Newly synthesised 2D and 3D layered nanostructures incorporating carbon-supported iron oxide nanoparticulate pre-catalysts were tested, upon hydrogen reduction in situ, for the conversion of CO₂ to CO as well as for the selective formation of CH₄ and longer chain hydrocarbons. The reduction reaction was also carried out and the catalytic species isolated and fully characterised. The catalytic activity of a graphene oxide-supported iron oxide pre-catalyst converted CO₂ into hydrocarbons at different temperatures (305, 335, 370 and 405 °C), and its activity compared well with that of the analogues supported on graphite oxide, the 3-dimensional material precursor to the graphene oxide. Investigation into the use of graphene oxide as a framework for catalysis showed that it has promising activity with respect to reverse gas water shift (RWGS) reaction of CO₂ to CO, even at the low levels of catalyst used and under the rather mild conditions employed at atmospheric pressure. Whilst the γ-Fe₂O₃ decorated graphene oxide-based pre-catalyst displays fairly constant activity up to 405 °C, it was found by GC-MS analysis to be unstable with respect to decomposition at higher temperatures. The addition of palladium as a promoter increased the activity of the iron functionalised graphite oxide in the RWGS. The activity of graphene oxide supported catalysts was found to be enhanced with respect to that of iron-functionalised graphite oxide with, or without palladium as a promoter, and comparable to that of Fe@carbon nanotube-based systems tested under analogous conditions. These results display a significant step forward for the catalytic activity estimations for the iron functionalised and rapidly processable and scalable graphene oxide. The hereby investigated phenomena are of particular relevance for the understanding of the intimate surface morphologies and the potential role of non-covalent interactions in the iron oxide-graphene oxide networks, which could inform the design of nano-materials with performance in future sustainable catalysis applications.     

Integration of electrochemical generator and detector of nitric oxide with the aid of the iron porphyrin

An electrochemical cell of generating nitric oxide (NO) was constructed in order to realize the catalytic reaction of nitrite by iron porphyrin [Y. Chi, J. Chen, K. Aoki, Inorg. Chem. 43 (2004) 8437]. The cell was composed of the generator of the iron porphyrin-including Nafion^®-coated electrode, the ion-exchange membrane, and the electrochemical detector of NO. The reduction of iron porphyrin in the presence of nitrite at the generator coordinates nitrite to form the NO-included complex, of which oxidation releases NO. The water-dissolved NO diffused to the detector through the membrane to block nitrite. It was detected by voltammetry with the aid of the oxidative catalytic reaction of iron porphyrin.     

STRUCTURAL FEATURES AND CATALYTIC PROPERTIES OF AgFeO2 BINARY OXIDE IN THE СО OXIDATION REACTION

Journal of Structural Chemistry - Structural features and catalytic properties of silver and iron binary oxide AgFeO2 in the СО oxidation reaction are investigated. Binary oxide samples...     

氧化铁磁性纳米粒子固定化酶*

纳米粒子作为酶固定化的载体,当其具有磁性时,制备的固定化酶易于从反应体系中分离和回收,操作简便;并且利用外部磁场可以控制磁性材料固定化酶的运动方式和方向,替代传统的机械搅拌方式,提高固定化酶的催化效率。在众多纳米材料中,氧化铁因其在磁性、催化等多方面的良好特性而倍受瞩目。本文对近年来各种氧化铁磁性纳米粒子固定化酶,尤其是固定化脂肪酶和蛋白酶的制备方法及其应用做了较为详细的阐述,对这些氧化铁磁性纳米粒子固定化酶的优缺点和发展前景进行了讨论。     

Catalytic conversions of chloroolefins over iron oxide nanoparticles 2. Isomerization of dichlorobutenes over iron oxide nanoparticles stabilized on the surface of ultradispersed poly(tetrafluoroethylene)

Nanosized iron oxides stabilized on the surface of ultradispersed poly(tetrafluoroethylene) (UPTFE) granules were synthesized by the thermal destruction of iron formate in boiling bed of UPTFE on the surface of heated mineral oil. The particle size of nanoparticles (∼6 nm) containing 5, 10, and 16 wt.% Fe depends weakly on the temperature of synthesis and iron to polymer ratio. The metal state is determined by the synthesis conditions. The nanoparticles synthesized at 280 °C consist mainly of the Fe₃O₄ and Fe₂O₃ phases. The samples obtained at 320 °C also contain iron(II) oxide. The catalytic properties of the obtained samples were tested in dichlorobutene isomerization. Unlike isomerization on the iron oxide nanoparticles supported on silica gel, reaction over the UPTFE supports proceeds without an induction period. The sample with 10 wt.% Fe containing magnetically ordered γ-Fe₂O₃ nanoparticles possesses the highest catalytic activity. Fast electron exchange between the iron ions in different oxidation states and high defectiveness of the nanoparticles contribute, most likely, to the catalytic activity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1383–1390, June, 2005.     

Iron oxide modified diamond blends containing ultradispersed diamond

Iron oxide modified diamond blends containing different amounts of ultradispersed diamond were prepared and characterized by nitrogen physisorption, X-ray diffraction, temperature programmed reduction, M?ssbauer and IR spectroscopy. The catalytic behavior of these composite materials in methanol decomposition to hydrogen, carbon monoxide, and methane has been also studied. The initial state and phase transformations of the supported highly dispersed iron oxide particles in various pretreatment media, as well as their reductive and catalytic properties, strongly depend on the ultradispersed diamond content in the diamond blends.     

Effect of the calcination temperature on the properties of Fe2O3/SiO2 catalysts for oxidation of hydrogen sulfide

The effect of the calcination temperature on the properties of supported iron oxide catalysts for hydrogen sulfide oxidation prepared by impregnation of silica with iron(III) nitrate has been studied. An increase in the calcination temperature was found to diminish the catalytic activity of the Fe₂O₃/SiO₂ catalysts in hydrogen sulfide oxidation. This behavior can be explained by the agglomeration of iron oxide particles and by a decrease in the surface concentration of active sites. It has been shown that an increase in the calcination temperature makes the catalyst more stable towards the sulfidation of the active component (Fe₂O₃) to the iron disulfide phase.