Electrodeposition of Au/nanosized diamond composite coatings

Ultra-dispersed diamond UDD particles were codeposited in gold matrix coatings from a sulphite electrolyte, changing bath load and key operating parameters. The influence of electrolyte pH, current density and bath load on current efficiency, particle co-deposition, surface morphology and microhardness of composite coatings was investigated. UDD incorporation is mainly affected by bath load; however, particle embedding is specifically sensitive to electrolyte pH and deposition current density. The maximum mass fraction of carbon in the coating, about 0.55%, is obtained by depositing from ultrasonically pre-treated electrolytes with UDD concentration 20 g l⁻¹, pH 9.5 and 3 mA cm⁻² . Au/UDD composites are characterised by an increased microhardness and improved wear resistance. When compared to pure gold coatings which are notoriously weak, Au/UDD electrodeposits from sulphite electrolytes represent a significant improvement. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16, 2005     

Ultradispersed diamond as a new carbon support for hydrodechlorination catalysts

The properties of palladium and nickel catalysts supported on ultradispersed diamond (UDD) were studied in the vapor-phase hydrodechlorination (HDC) reaction of chlorobenzene and the multiphase HDC of polychlorobenzenes. The catalysts on UDD exhibited a number of advantages: the vapor-phase HDC of chlorobenzene on Ni/UDD occurred at lower temperatures, and the multiphase HDC of chlorobenzene, 1,3,5-trichlorobenzene, and 2,4,8-trichlorodibenzofuran on Pd/UDD occurred more rapidly than that on catalysts supported on activated carbon. The structure of the catalysts and the electronic states of the active components were studied using IR spectroscopy, temperature-programmed reduction, and adsorption techniques. It was found that the properties of the catalysts depend on the electronic state of palladium, which depends on its concentration in the sample; the structural properties, which are responsible for the accessibility of the active surface to adsorption; and the presence of other metal impurities.     

Fabrication of bimetallic nanoparticles modified hollow nanoporous carbons derived from covalent organic framework for efficient degradation of 2,4-dichlorophenol

Bimetallic nanoparticles modified hollow-structured nanoporous carbons (NPCs) have been fabricated via a convenient one-step carbonizing strategy derived from covalent organic framework. The Pd/Fe/NPCs, Pt/Fe/NPCs and Rh/Fe/NPCs were obtained and can be used as Fenton-like catalysts with good stability and reusability. The catalytic activity was evaluated by the degradation of 2,4-dichlorophenl (2,4-DCP). These fabricated bimetallic catalysts exhibited much higher catalytic activity than Fe/NPCs at room temperature. The enhancement of catalytic ability was benefited from synergetic catalytic effect of bimetallic nanoparticles and accelerated mass transfer of hollow structure. Additionally, the enhanced catalytic mechanism of bimetallic catalysts was studied in detail and the reasonable reaction pathway was proposed. Besides, the bimetallic catalysts were successfully used for degradation of 2,4-DCP in actual industrial wastewater and the removal efficiency could reach 74.3% within 120 min, which demonstrated the promising potential application of bimetallic catalysts in the removal of pollutants in environment.     

磁性纳米固体超强酸的合成、表征及性能

首次制备了SO₄^2-/Co_0.5Fe_2.5O₄-ZrO₂磁性固体超强酸,利用TEM,DTA,XRD和FTIR等手段研究了Co_0.5Fe_2.5O₄磁性基质对ZrO₂的粒子大小、晶化温度与结构的影响.考察了磁性固体超强酸的催化性能及催化剂的寿命、回收率和磁性.结果表明,引入Co_0.5Fe_2.5O₄磁性基质不但赋予催化剂以磁性,而且在固体超强酸形成过程中延迟了ZrO₂由四方晶相向单斜晶相的转变,有助于稳定样品表面的含硫物种,磁性固体超强酸对酯化反应具有较高的催化活性,可活化再生,并保持磁性.     

Fe3O4/Polypyrrole/Au nanocomposites with core/shell/shell structure: synthesis, characterization, and their electrochemical properties

Uniform Fe3O4 nanospheres with a diameter of 100 nm were rapidly prepared using a microwave solvothermal method. Then Fe304/polypyrrole (PPy) composite nanospheres with well-defined core/shell structures were obtained through chemical oxidative polymerization of pyrrole in the presence of Fe3O4; the average thickness of the coating shell was about 25 nm. Furthermore, by means of electrostatic interactions, plentiful gold nanoparticles with a diameter of 15 nm were assembled on the surface of Fe3O4/PPy to get Fe3O4/PPy/Au core/shell/shell structure. The morphology, structure, and composition of the products were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The resultant nanocomposites not only have the magnetism of Fe3O4 nanoparticles that make the nanocomposites easily controlled by an external magnetic field but also have the good conductivity and excellent electrochemical and catalytic properties of PPy and Au nanoparticles. Furthermore, the nanocomposites showed excellent electrocatalytic activities to biospecies such as ascorbic acid (AA).     

Catalytic activity of MCM-48-, SBA-15-, MCF-, and MSU-type mesoporous silicas modified with Fe3+ species in the oxidative dehydrogenation of ethylbenzene in the presence of N2O

MCM-48, SBA-15, MCF, and MSU mesoporous silicas were used as supports for a deposition of Fe oxide species. Iron was introduced using two different methods: the wetness impregnation and the molecular designed dispersion (MDD). The obtained catalysts were characterized with respect to their textural parameters (BET), chemical composition (electron microprobe analysis), and reducibility (TPR). The coordination environment of Fe was determined using EPR and UV-vis/DRS. The samples were tested as catalysts in the oxidative dehydrogenation of ethylbenzene to styrene in the presence of N(2)O. An influence of Fe dispersion and reducibility on the catalytic activity was discussed. Isolated Fe(3+) species appeared to be more selective in the styrene formation, whereas iron oxide clusters showed a higher selectivity in total oxidation of aromatic hydrocarbons. The reaction system was well described by the Mars- van Krevellen mechanism.     

Structural and textural properties of Al,Fe-pillared clay catalysts

Metal oxide pillared interlayered clays (PILCs) represent a new class of materials that have found a wide range of potential applications including catalytic oxidative degradation of organic pollutants in water. Al,Fe-pillared smectite clays with different Fe content were synthesized for possible catalytic application. Starting clay and the obtained PILCs were characterized. Phase composition, textural and morphological properties of the starting clay and synthesized PILCs were determined using X-ray diffraction, physisorption of nitrogen and scanning electron microscopy. Chemical composition of the PILCs was determined using EDX. It was found that the synthesized PILCs have similar phasal composition, textural and morphological properties differing only in Fe content in accordance with the amount of Fe introduced to clay during the pillaring process. The article is published in the original.     

Ni-Fe-Al-O双金属催化剂在生物质基2-羟基四氢吡喃还原胺化合成5-氨基-1-戊醇中的性能研究北大核心CSCD

采用共沉淀法制备了不同Fe/Ni摩尔比(0、0.125、0.25、0.5和0.75)的Al_(2)O_(3)负载型NiFe单、双金属催化剂,并考察了它们在生物糠醛衍生2-羟基四氢吡喃(2-HTHP)还原胺化合成高附加值5-氨基戊醇反应中的催化性能.研究发现当Fe/Ni摩尔比为0.25时表现出最高的5-氨基戊醇收率(在80℃和2 MPa优化条件下达90%).利用N_(2)吸脱附、X射线衍射(XRD)、氢气程序升温还原(H_(2)-TPR)、透射电镜(TEM)等技术对催化剂进行了表征,结果表明适量Fe的掺入可以提高催化剂的分散性和还原性,同时在还原活化催化剂中形成Ni-Fe合金相,继而使相应催化剂表现出更优异的催化活性.通过固定床对比考察了催化剂的稳定性,NiFe(0.25)-Al-O双金属催化剂表现出明显优于NiFe(0)-Al-O单金属催化剂的稳定性,运行120 h前者只有微弱失活而后者显著失活.对比反应后催化剂表征发现,金属Fe的修饰可以有效抑制金属活性颗粒的烧结和流失,从而显著提高其反应稳定性.     

单原子Cr、Fe和Ni催化乙炔环三聚反应机理研究

应用密度泛函理论(DFT)研究了 Cr、Fe和Ni 3种金属原子催化乙炔环三聚生成苯的反应机理.结果表明,Cr、Fe和Ni催化体系均表现出自旋翻转现象,Cr原子催化乙炔环三聚过程在自旋七重态和五重态势能面上进行,速率控制步骤为形成铬金属七元环;Fe和Ni催化体系的速率控制步骤为两分子乙炔耦合过程.Cr催化体系表现出远高...     

置换反应制备Pd-Fe双金属催化剂及其催化加氢性能

以Fe(CO)5为前体采用超声法合成纳米Fe胶体粒子,通过Fe胶体与PdCl2发生金属置换反应制备出活性炭负载Pd-Fe双金属催化剂。研究了表面活性剂聚乙烯吡咯烷酮对制备负载型催化剂的影响。采用XRD、H2程序升温还原（H2-TPR）、TEM、EDX等表征手段对催化剂进行表征,以苯乙炔加氢反应为探针反应考察了Fe含量对于催化剂催化性能的影响。结果表明加氢催化活性较差的金属组分Fe在合适的比例下可以促进Pd基催化剂的加氢催化活性和选择性,然而,过多的Fe也会降低其催化活性。     

Fe_2O_3／ZrO_2催化剂上一氧化碳加氢反应制低碳烯烃──I．催化剂反应性能及反应过程中铁物相的变化

用浸渍法制得一系列不同铁负载量的Ｆｅ２Ｏ３／ＺｒＯ２催化剂，应用催化反应评价结合穆斯堡尔谱对催化剂的ＣＯ加氢反应性能、催化剂活性相结构及催化剂铁物种在合成气反应过程中的物相变化进行了研究．结果表明，铁负载量的大小对于Ｆｅ２Ｏ３／ＺｒＯ２催化剂的Ｆ－Ｔ反应催化性能有很大影响，铁负载量适当时，Ｆｅ２Ｏ３／ＺｒＯ２催化剂铁锆间适当的强相互作用使得催化剂在保持较高催化活性的同时高选择性地生成低碳烯烃，产物分布偏离Ｓｃｈｕｌｚ－Ｆｌｏｒｙ分布规律．     

First insight into catalytic activity of anionic iron porphyrins immobilized on exfoliated layered double hydroxides

Mg-Al layered double hydroxide (LDH) intercalated with glycinate anions was synthesized through co-precipitation and exfoliated in formamide and the single-layer suspension was reacted with aqueous iron porphyrin solutions (Fe(TDFSPP) and Fe(TCFSPP)). The obtained materials were characterized by X-ray powder diffraction, UV-vis, and electron paramagnetic resonance and investigated in the oxidation reaction of cyclooctene and cyclohexane using iodosylbenzene as oxidant. The iron porphyrin seems to be immobilized at the surface of the glycinate intercalated LDH. The catalytic activities obtained in heterogeneous media for iron porphyrin, Fe(TDFSPP), was superior to the results obtained under homogeneous conditions, but the opposite effect was observed on the Fe(TCFSPP), indicating that, instead of the structural similarity of both iron porphyrins (second-generation porphyrins), the immobilization of each one produced different catalysts. The best catalytic activity of the Fe(TDFSPP)/Gly-LDH, compared to Fe(TCFSPP)/Gly-LDH, can be explained by the easy access of the oxidant and the substrate to the catalytic sites in the former, probably located at the surface of the layered double hydroxide pillared with glycinate anions. A model for the immobilization and a mechanism for the oxidation reaction will be discussed.     

Reduction of NO with methane over Fe/ZSM-5 catalysts

<正>The catalytic activity of Fe/ZSM-5 for the selective reduction of NO to N_2 with methane in the presence of excess O_2 was studied.Fe/ZSM-5 catalysts with various Fe loadings were prepared by impregnation method.It is well known that methane is inactive when Fe/ZSM-5 as the catalyst for the selective catalytic reduction(SCR) of NO with methane.However,this paper shows that when the content of Fe was about 0.5%,Fe/ZSM-5 showed higher catalytic activity and selectivity of methane,and put forward measurable activation for CH_4 is an important factor for the reaction of removal of NOx with CH_4.     

介孔铁铝/蒙脱土复合材料：解离柱撑制备、结构及催化羟基化性能

利用极稀悬浮液中蒙脱土的解离作用并结合柱化技术过程，制备了介孔结构的铝铁/蒙脱土复合材料(Fe-Al/mmt)；并采用粉末X射线衍射、氮等温吸脱附、傅立叶红外光谱、紫外可见光漫反射光谱及苯酚催化羟基化反应表征了其结构和性能。结果显示，铁铝聚合前驱液中铁/铝比影响复合材料中蒙脱土的解离程度，且仅当低铁/铝比时(即Fe/(Fe+Al)物质的量的比介于0.05～0.3)，嵌入解离的蒙脱土片层间的混合铁铝物种呈现能耐温350 ℃的热稳定性；氮等温吸脱附分析反映出这种解离的蒙脱土堆积结构呈现介孔特征，孔径分布窄，介于2.0～2.3 nm；红外分析表明材料表面具有L酸和B酸位，并且L酸位量与嵌入解离的蒙脱土结构中的混合铁铝物种相关；由于结构中混合铁铝物种的存在及相应的Si-O → Fe、Al-O → Fe间的电子跃迁，Fe-Al/mmt材料在紫外区呈现宽泛的能量吸收特征。这些结果说明，由于混合铁铝物种嵌入于解离的蒙脱土片层堆积结构中，形成了“卡片屋”式介孔结构。实验条件下，Fe/(Fe+Al)物质的量的比为0.3的Fe-Al/mmt呈现较佳的催化羟基化性能，苯酚转化率为36.7%，二酚产物选择性32.3%；并且初步表明铝掺杂后，通过铁铝比和表面酸性的调整，材料的部分选择氧化性能可以得到改善。     

改性PAN纤维与Fe3+的配位反应及配合物的催化性能

采用盐酸羟胺和水合肼的混合物分别对PAN纤维进行改性制备了偕胺肟改性PAN纤维(AO-PAN)和混合改性PAN纤维(M-PAN), 并分别与Fe³⁺进行配位反应生成两种改性PAN纤维铁配合物(Fe-AO-PAN和Fe-M-PAN). 研究了配位反应的动力学特性及温度和Fe³⁺初始浓度的影响, 并采用DRS和ESR技术比较了两种不同改性PAN纤维铁配合物对偶氮染料活性红195氧化降解反应的催化性能. 结果表明, 在所设定的温度和浓度范围内, 两种改性PAN纤维与Fe³⁺之间的配位反应平衡符合Langmuir 和Freundlich 吸附等温模型以及Lagergren准二级动力学方程, 并且AO-PAN比M-PAN更容易与Fe³⁺发生配位反应. 在相同条件下AO-PAN与Fe³⁺反应的配合量和反应速率常数均比M-PAN与Fe³⁺反应的高. 两种配合物对染料的氧化降解反应具有催化作用, 暗态条件下Fe-M-PAN比Fe-AO-PAN表现出更高的催化活性, 而光辐射条件下Fe-AO-PAN的催化活性显著增强.     

Collaboration of Ni,polyoxometalates and layered double hydroxides: synthesis,characterization, electrochemical and mechanism investigations as nano-catalyst in the Heck coupling reaction

Nickel (Ni) nanoparticles were immobilized on the surface of magnetic MgAl layered double hydroxide intercalated 10-molybdo-2-vanadophosphate (Fe–MgAl/Mo₁₀V₂–Ni) for the first time. The presence of Ni nanoparticles onthe high-surface area Fe–MgAl LDH structure in the presence of Mo₁₀V₂ makes this catalyst an ideal option in terms of efficiency and selectivity for Heck coupling reaction. Synergic effects of Mo₁₀V₂ and Ni were investigated by an electrochemical technique. Increasing of the ECSA of the catalyst compared to Fe–Mg–Al–Ni leads to enhancement of the catalytic activity and proves the synergic effect. A new catalytic mechanism was introduced for this kind of reaction. The resulting structure and its catalytic behavior were characterized by FT-IR, XRD, ICP-AES, TEM, SEM, EDX, EBSD, XPS, BET, VSM, CV, LSV and zeta potential analyses. More importantly, Fe–MgAl/Mo₁₀V₂–Ni can easily be separated from the reaction mixture using an external magnet and reused for at least four successive runs without any substantial reduction in its catalytic activity.     

Catalytic Oxidation of Methane by Nitrous Oxide on H[Al]ZSM-5 Zeolite, Silicalite, and Amorphous SiO2 Modified by Iron, Silver, and Gadolinium Ions

Methane oxidation by an excess of N₂O on the catalytic sites formed in HZSM-5 zeolite, silicalite, and SiO₂ after modification with iron, silver, and gadolinium cations in different combinations is studied. Introduction of iron and silver ions into H[Al]ZSM-5 zeolite is shown to result in the formation of the sites that are active in methane oxidation, while the systems obtained on the basis of crystalline silicalite or amorphous SiO₂ demonstrate poor or no catalytic activity, respectively. Complete oxidation of methane with 100% conversion is observed on the Fe/HZSM-5 and Ag/HZSM-5 catalysts at temperatures higher than 350 and 450°C, respectively. A decrease in the reaction temperature and in the methane conversion is accompanied by coking of the catalysts and, in the case of Fe/HZSM-5, by the appearance of trace amounts of methanol and formic acid in the gas phase. The temperature dependence of the activity and selectivity for the Ag/HZSM-5 and (Ag + Gd)/HZSM-5 catalysts exhibits a pronounced hysteresis at 330–480°C, and the formation of coke proceeds much faster than in the case of iron-containing samples. Catalytic properties of (Fe + Ag)/HZSM-5 are similar to those of Fe/HZSM-5. The introduction of Gd does not influence significantly the activity and selectivity of the catalysts. ESR and TG–DTA were used to determine the state and distribution of Fe, Ag, and Gd in the samples and to examine the processes of coke formation.     

Fe/MgO催化合成碳纳米管和氮掺杂碳纳米管

以MgO负载的Fe为催化剂、正己烷为碳源、乙二胺为氮源, 用催化化学气相沉积法合成了碳纳米管(CNTs)和氮掺杂碳纳米管(CNx). 通过还原焙烧的Mg/Fe水滑石(LDH)和Mg(NO3)2/Fe(NO3)3前驱体得到具有催化活性的Fe催化剂(Fe-LDH和Fe-Mg(NO3)2/Fe(NO3)3). 由这两种催化剂催化合成的CNTs都具有中空的管状结构. Fe-LDH催化合成的CNx具有明显的“竹节”状形貌, 而Fe-Mg(NO3)2/Fe(NO3)3催化合成的部分CNx的形貌与“竹节”状不同. 该CNx具有厚的管壁且在管壁的石墨层与层之间存在大量的空隙. Fe-LDH催化合成的CNx中氮摩尔分数为6.3%, 高于Fe-Mg(NO3)2/Fe(NO3)3催化合成CNx中的5.7%; 但后者具有更多的缺陷, 石墨化程度更加无序.     

稀土-其它过渡金属混合催化剂用于共轭双烯烃的聚合——Ⅳ.(NdCl_3+FeCl_3)·nphen-HAI(i-Bu)_2体系对异戊二烯的聚合

本文报道由(NdCl_3+FeCl_3)·nphen-HAl(i-Bu)_2催化体系引发异戊二烯聚合的结果。在适当Nd/Pe比下,该体系对异戊二烯聚合的活性可超过单一钕或铁催化剂的活性,同时随催化剂中钕和铁含量的不同,所得产物的微观结构变化很大,当体系中钕含量由100％→0时,产物的顺-1,4结构含量由94.4％→22.1％,而3,4结构含量由5.6％→77.9％。Al/M(N=Nd+Fe)比、单体浓度和聚合温度不仅对聚合活性有影响,对产物的微观结构影响也较大。事实表明,该聚合体系中存在着两种过渡金属(Nd和Fe)活性中心,它们按各自的机理进行异戊二烯的聚合。     

聚合物微球固载的催化剂TEMPO在分子氧氧化环己醇过程中的催化特性

醇氧化为羰基化合物是有机合成工业中最重要的化学转变之一,在实验室研究和精细化工生产中都占有非常重要的地位.使用传统的化学计量强氧化剂(如CrO3, KMnO4, MnO2等),不但成本高及反应条件苛刻,还会产生大量污染环境的废弃物.因此,需要大力发展高效、绿色化的醇转变为羰基化合物的氧化途径.以2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)为催化剂,分子氧为氧化剂,可在温和条件下绿色化地实现醇的氧化转变.该催化氧化作用的实质是TEMPO经过单电子氧化过程转化为相应的氮羰基阳离子,该阳离子是一个具有强氧化性的氧化剂,可将伯醇和仲醇分别快速地、高转化率、高选择性地氧化为对应的醛或酮.然而,目前使用的TEMPO大多为均相催化剂,虽然表现出良好的催化活性和选择性,但反应后难以分离回收,不能再循环使用,严重制约着这一催化体系的发展.本文将TEMPO化学键合在聚合物载体上,在非均相催化剂的作用下,以期实现环已醇的分子氧氧化,将其转变为环已酮.首先采用悬浮聚合法,制备了交联聚甲基丙烯酸缩水甘油酯(CPGMA)微球,该聚合物微球表面含有大量环氧基团,为实现TEMPO的固载化提供了条件.以4-羟基-2,2,6,6-四甲基哌啶氮氧自由基(4-OH-TEMPO)为试剂,使CPGMA微球表面的环氧基团发生开环反应,从而将TEMPO键合于微球表面,制得了固载有TEMPO的聚合物微球TEMPO/CPGMA.将此非均相催化剂与Fe(NO3)3组成共催化体系,应用于分子氧氧化环己醇的催化氧化过程,深入考察了该共催化体系的催化性能,并探索研究了催化氧化机理,考察了主要条件对催化氧化反应的影响.结果表明,共催化体系TEMPO/CPGMA+Fe(NO3)3可以有效地催化分子氧氧化环己醇的氧化过程,将环己醇转化为唯一的产物环己酮,显示出良好的催化选择性.助催化剂Fe(NO3)3化学结构中的Fe3+离子和NO3–离子两种物种均参与催化过程,共同发挥助催化剂的作用,伴随着两种价态铁物种Fe(Ⅱ)与Fe(Ⅲ)的转变以及NO3–与NO2–之间的转变,固载化的氮氧自由基TEMPO不断地转变为氮羰基阳离子,该氧化剂物种使环己醇的氧化反应不断地循环进行.对于共催化体系TEMPO/CPGMA+Fe(NO3)3的使用,适宜的反应条件为TEMPO与Fe(NO3)3的摩尔比为1：1,55°C,通入常压O2.反应35 h,环己酮的转化率可达到44.1%.因此,在温和条件下,使用固载化的TEMPO,有效地实现了环己醇向环己酮的转化.此外,固载化催化剂TEMPO/CPGMA在循环使用过程中表现出良好的重复使用性能.