NO 和 NO2 在 V2O5/AC 催化剂表面的反应行为

 采用程序升温脱附、在线质谱和原位漫反射红外光谱等手段, 比较了 NO 和 NO2 在 V2O5 及 V2O5/AC 催化剂表面的选择催化还原 (SCR) 反应行为. 结果表明, 氨以质子态 NH4+和共价态 NH3 分子两种形态吸附于纯 V2O5 表面, V=O 为氨的主要吸附活性位. 无氧状态下, NO 和 NO2 皆可与吸附于 V2O5 表面的 NH3 反应, 并且 NO2 与吸附态 NH3 的反应活性高于 NO. 但在 V2O5/AC 催化剂表面, 同样在无氧条件下, NO 几乎不与吸附态 NH3 反应, 而 NO2 却可以反应并生成 N2. 在 V2O5/AC 表面, NO 很容易被气相 O2 氧化为 NO2, 然后参与 SCR 反应. 可见, NO2 是 NO 在 V2O5/AC 表面发生 SCR 反应的中间体.     

Nanocomposites Produced by Direct Intercalation of Secondary Doped Polyaniline in V2O5

The possibility of the production of nanocomposites based on V₂O₅ and conducting polymers by direct intercalation of macromolecules of secondary doped polyaniline into the interlayer galleries of nanoparticles of aqueous V₂O₅ sol was demonstrated for the first time. The driving force of the intercalation process is substitution of the protons present in the galleries of the V₂O₅ by a polyaniline chain carrying a positive charge.     

Phase Equilibria in the V2O5-Sb2O4 System

Differential thermal analysis (DTA) and X-ray powder diffraction (XRD) were used to study phase equilibria, established in air in the V₂O₅-Sb₂O₄ system up to 1000°C. It has been found that there is a new phase =SbVO₅. The =SbVO₅ has been prepared by two methods: by heating equimolar mixtures of V₂O₅ and α-Sb₂O₄ in air and by oxidation of the known phase of rutile type obtained in pure argon at temperatures between 550 and 650°C. Thermal decomposition of =SbVO₅ in the solid state starts at 710°C giving off oxygen. The results provide a basis for constructing only a part of the phase diagram of the investigated system (up to 50.00 mol% Sb₂O₄). This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrical conductivity of g-Bi2O3-V2O5 solid solution

The total conductivity (σ_T) in bcc γ-Bi₂O₃ doped with V₂O₅ system has been measured in the composition range between 1 and 7 mol% V₂O₅ at different temperatures. Phase transitions for different addition amounts depending on the temperature were investigated by quenching the samples. According to the XRD and DTA/TG results, this bcc type solid solution was stable up to about 720°C and the solubility limit was found at ˜7 mol% V₂O₅ in γ-phase. This system showed predominantly an oxide ionic conduction. As the V₂O₅ addition increased, the ionic conduction increased up to 5 mol% V₂O₅ at which the highest conductivity was found to be 8.318·10^-2 Ω^-1 cm^-1 at 700°C and then decreased. It has been proposed that γ-Bi₂O₃ phase contains a large number of oxide anion vacancies and incorporated vanadium cations at tetrahedral sites which affect the oxygen sublattice of the crystal structure. This revised version was published online in August 2006 with corrections to the Cover Date.     

V2O5/TiO2 Catalyst Xerogels: Method of Preparation and Characterization

This work describes a modified sol-gel method for the preparation of V₂O₅/TiO₂ catalysts. The samples have been characterized by N₂ adsorption at 77 K, X-ray Diffractometry (XRD), Scanning Electronic Microscopy (SEM/EDX) and Fourier Transform Infrared Spectroscopy (FT-IR). The surface area increases with the vanadia loading from 24 m² g^–1 for pure TiO₂ to 87 m² g^–1 for 9 wt% of V₂O₅. The rutile form is predominant for pure TiO₂ but becomes enriched with anatase phase when vanadia loading is increased. No crystalline V₂O₅ phase was observed in the diffractograms of the catalysts. Analysis by SEM showed heterogeneous granulation of particles with high vanadium dispersion. Two species of surface vanadium were observed by FT-IR spectroscopy: a monomeric vanadyl and polymeric vanadates. The vanadyl/vanadate ratio remains practically constant. Ethanol oxidation was used as a catalytic test in a temperature range from 350 to 560 K. The catalytic activity starts around 380 K. For the sample with 9 wt% of vanadia, the conversion of ethanol into acetaldehyde as the main product was approximately 90% at 473 K.     

V2O5-CuO/TiO2催化剂中低温选择性催化NOx还原研究

浸渍法制备了一系列V₂O₅-CuO/TiO₂催化剂,考察中低温(200~300℃)条件下,以氨为还原剂选择性催化还原NO_x的活性,并利用比表面积及微孔孔隙分析仪(BET)、X射线衍射(XRD)对催化剂进行微观表征和分析。结果表明,500℃焙烧的2V16Cu/TiO₂催化剂展示了最佳的中低温催化活性和较宽的活性温度范围,在空速6.0×10⁴ h^-1、225℃条件下,NO_x转化率达97.3%,250℃时达到100%,温度升至300℃,催化活性仍保持在100%。XRD结果表明,随着Cu负载量的增加,逐渐显现CuO的特征峰。结合活性评价数据说明,CuO是VCu/TiO₂催化剂的主要活性组分之一,是降低SCR催化反应温度的重要因素。BET结果表明,CuO的负载对钒钛催化剂的表面结构有较大影响。耐硫性实验结果表明,添加钒氧化物制备的2V16Cu/TiO₂催化剂的抗硫性能有所改善。     

V2O5/ACF催化剂低温下选择性催化还原NO的机理

将V2O5担载在活性炭纤维(ACF)上制得V2O5/ACF催化剂,并采用暂态响应实验和NH3吸附氧化实验等考察了影响V2O5/ACF催化剂上选择性催化还原(SCR)反应的关键因素.结果表明,NH3在催化剂表面的吸附是必要的,而且该吸附是一个快速过程;气相O2的存在有利于形成催化剂中所需的活性氧化态物种.NH3吸附.脱附与原位质谱相结合的实验表明,V2O5/ACF催化剂具有吸附NH3和将NH3氧化为N2H2的能力,N2H2为NH3氧化的一种中间体.     

V2O5 based quadruple nano‐perovskite as a new catalyst for the synthesis of bis and tetrakis heterocyclic compounds

In this article, we presented a novel, efficient and facile approach for using strontium titanate supported catalyst in organic synthesis. Bis and tetrakis of coumarin, indole and xanthene derivatives can effortlessly have prepared using V₂O₅/perovskite nanoparticles (NPs) under solvent‐free condition. V₂O₅/perovskite in (NPs) was prepared and identified using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and scanning electron microscope supported with energy dispersive X‐ray (SEM/EDAX). Calculated crystal size was from the intense XRD peaks was found to range between 50–60 nm in agreement with that obtained from the transmission electron microscopic investigation. EDAX analysis and mapping images reveal a homogenous distribution of all constituents with their calculated ratios in the synthesized catalyst.     

SO2影响V2O5/AC催化剂脱硝活性的机理

通过O2和SO2瞬态响应实验,研究了有水条件下SO2抑制V2O5/AC(活性焦)催化剂脱硝的原因.结果表明,SO2与V2O5反应生成VOSO4,导致V2O5/AC催化剂的脱硝活性下降.VOSO4的量动态变化,既与气氛中SO2的浓度有关,也与催化剂已实现的脱硫量(或硫含量)有关.催化剂的微孔(d<1nm)有利于SO3的迁移和储存,从而有利于脱硝.     

Ein neues Syntheseverfahren für Vanadiumbronzen. Die Kristallstruktur von β?Ag0,33V2O5. Verfeinerung der Kristallstruktur von ϵ?Cu0,76V2O5

A Novel Means of Synthesis for Vanadium Bronzes. Crystal Structure of β? Ag_0.33V₂O₅. Refinement of the Crystal Structure of ?? Cu_0.76V₂O₅ Ag_0.33V₂O₅ and Cu_0.76V₂O₅ were obtained by heating equimolar mixtures of AgI + V₂O₅ (700°C) and CuI + V₂O₅ (525°C), respectively, in sealed quartz glass ampoules. In each case, one of the well-formed crystals served for an X-ray structure analysis. Ag_0.33V₂O₅ has the structure known of the β phase of the vanadium bronzes, i. e. layers of edge-sharing, distorted VO₆ octahedra are liked by certain common octahedron vertices, the Ag atoms randomly occupy two positions with occupation probabilities of 0.5. Cu_0.76V₂O₅ has the previously determined structure of the ? phase, however, its space group is not Cm but C2/m.     

水对V2O5/AC催化剂低温还原NO的影响

 研究了烟气中的水对新型V2O5／AC催化剂选择催化还原NO的影响．结果表明,水通过与反应物（如NO和NH3）的竞争吸附而在一定程度上降低了催化剂的活性．在SO2共存下,水的存在导致硫酸铵盐在催化剂表面的过量沉积,造成催化剂孔道堵塞,比表面积减小,从而使催化剂失活．较高的反应温度（如553K）和／或低空速有利于催化剂的活性和稳定性．脱除活性焦载体中的矿物质可在一定程度上减缓催化剂失活的速率,但不能完全抑制水对V2O5／AC催化剂的毒化作用．     

Temperature-programmed reduction of V2O5 and coprecipitated V2O5−TiO2 by hydrogen

Temperature-programmed reductions (TPR) with H₂ of both pure V₂O₅ and coprecipitated V₂O₅?TiO₂ systems with different titanium concentrations was performed. The original and the reduced samples following each TPR step were characterized by X-ray diffraction, Fourier transform infrared analysis and scanning electron microscopy. Within the temperature range in which TPR analysis was carried out (100–600°C) the V₂O₅ phase was reduced in two or three steps, while no variation in the TiO₂ phase (anatase or rutile) was observed. In the first reduction step only superficial reduction of the oxides was detected. In the following steps, the H₂ reacted with oxygen atoms of the V=O and V?O?V bonds. This led to important changes in the structure and morphology of the system. The experimental evidence allowed the conclusion that titanium stabilizes certain phases of vanadium oxides in which vanadium appears as V(+4) or as a mixture of V(+4) and V(+5). Moreover, when moderate and high titanium concentrations were used, the reduction temperature of the bulk V₂O₅ decreased markedly.     

V2O5-CeO2/TiO2-ZrO2催化剂表征及NH3还原NOx性能

商业选择性催化还原(SCR)催化剂V2O5-WO3(MoO3)/TiO2存在反应温度窗口窄(300–400 oC)和SO3转化率高等缺点,同时占催化剂总质量80%以上的载体TiO2比表面积小,热稳定性差.已有研究发现TiO2-ZrO2固溶体具有较大的比表面积和较强的表面酸性, TiO2与ZrO2的摩尔比为1：1时其比表面积达到最大. CeO2作为SCR催化剂的组成部分,由于其优良的储氧和放氧能力受到广泛关注.研究表明, CeO2-CuO, Ce/Ti-Si-Al和Mo2O3(Co2O3)/Ce-Zr等催化剂具有优良的SCR脱硝活性,同时对V2O5-WO3/TiO2催化剂进行CeO2改性,可提高催化剂的抗SO2中毒能力.实际烟气组分中同时存在SO2和H2O,必定会导致催化剂硫酸盐中毒,而目前对含Ce催化剂的硫酸盐中毒情况研究较少,因此开发新型高效脱硝催化剂十分必要.前期我们研究了xCeO2-3%V2O5/TiO2-ZrO2催化剂,发现CeO2可以显著拓宽脱硝温度窗口,同时增强催化剂酸性位点,但是V2O5含量较高时对环境及人体健康均有较大危害.本文采用共沉淀法制备摩尔比为1：1的TiO2-ZrO2固溶体,用浸渍法负载不同摩尔比的CeO2和1%的V2O5,得到一系列V-xCe/Ti-Zr催化剂,结合X射线衍射(XRD)、比表面积测试(BET)、高分辨透射电镜(HRTEM)、程序升温还原(H2-TPR)、原位漫反射红外光谱(in situ DRIFTS)和程序升温脱附(NH3-TPD)等手段分析催化剂的晶相、活性物质分散程度、氧化还原性质及表面酸性,在200–450 oC范围内考察Ce掺杂催化剂选择性催化还原NOx的脱硝活性,并在250 oC测试催化剂在NH3+NO+O2+SO2+H2O气氛中的脱硝活性,研究催化剂抗硫酸盐中毒能力.研究发现,CeO2掺杂可以拓宽脱硝反应活性窗口, V-0.2Ce/Ti-Zr (摩尔比Ce：Ti =0.2)表现出最优的脱硝性能,在250–350oC范围内脱硝效率均在92%以上,同时与前期研究结果对比发现CeO2含量较高时会导致高温段NOx转化率下降. XRD和HRTEM结果表明,ZrO2的添加可以显著降低载体TiO2的结晶度,复合氧化物TiO2-ZrO2呈无定形态, CeO2高度分散于载体之上,并且催化剂以单晶形式存在. H2-TPR结果表明,CeO2能显著提高催化剂的还原能力,主要的还原反应发生在CeO2的α(200–430oC)和β(430–600 oC)还原峰上,总体而言, V-0.2Ce/Ti-Zr表现出最大的氢气消耗量,即其还原性最强.低V2O5负载有利于较低温度SCR反应, V-0.3Ce/Ti-Zr的钒氧化物还原峰强度最大,其次是V-0.2Ce/Ti-Zr. NH3-TPD测试发现V2O5/TiO2主要存在中强酸及强酸,而V2O5/TiO2-ZrO2主要是弱酸, CeO2负载后随着其含量提高,弱酸强度增加.结合氨气原位漫反射红外光谱发现, CeO2可以增加催化剂Br?nsted和Lewis酸位数量,同时出现反应中间物–NH2, V2O5的负载量较高会抑制1660 cm–1处Br?nsted酸吸收峰的出现. BET结果发现, TiO2-ZrO2和V2O5/Ti-ZrO2比表面积分别可达255.73和143.77 m2/g, V2O5/TiO2仅为66.1 m2/g,表明ZrO2的添加可以显著增大催化剂比表面积,进而有利于SCR反应进行,沉积的氧化物进入载体孔道导致催化剂比表面积降低. V2O5-xCeO2/TiO2-ZrO2表现出较强的抗SO2中毒能力,但是在H2O存在条件下脱硝活性较差,可能是生成的硫酸铵盐及亚硫酸盐阻塞催化剂孔道所致. SO2和H2O停止通入后, V2O5-0.3CeO2/TiO2-ZrO2活性恢复至原有水平, V2O5-0.2CeO2/TiO2-ZrO2恢复至最初的84%.对中毒催化剂进行不同反应温度下的活性测试,发现V2O5-0.2CeO2/TiO2-ZrO2在中温段反应活性显著降低,可能是由于Ce(SO4)2的形成所致,由于V2O5-0.3CeO2/TiO2-ZrO2的Ce含量较高,其在此温度范围内活性依旧较高.两者在高温段NOx转化率均较高,推测是V2O5开始发挥活性组分作用的缘故.     

Synthesis and Characterization of Self-Assembled V2O5 Mesostructures Intercalated by Polyaniline

A new nanocomposite of vanadium pentoxide (V2O5) and polyaniline (PANI) were synthesized by in situ oxidative polymerization/intercalation on V2O5 powder at room temperature. The reaction was facile and topotactic, forming polyaniline as the emeraldine salt. It was indicated that V2O5 itself can catalyze the oxidative polymerization of aniline and that layered structure could make aniline intercalate into the V2O5 framework. It makes the in situ polymerization feasible to occur in the layer of V2O5 structure. XRD results showed PANI/V2O5 nanocomposite possessed lamellar mesostructure, which was determined by an X-ray diffraction peak at 6.5° and SEM photograph. And FT-IR spectrum suggested that there was interaction between PANI and V2O5. The hybrid had better thermal stability in N2 and air ambience.     

V2O5-MoO3-SiO2表面复合氧化物催化剂的制备与表征

采用表面改性法制备了V2O5-SiO2,MoO3-SiO2,V2O5-MoO3-SiO2复合氧化物催化剂,并用TPR和IR技术研究了催化剂的表面结构及V=O,M0=O的活性,同时用化学吸附IR技术研究了催化剂样品对异丁烷的化学吸附性能.实验结果表明:这些复合氧化物催化剂对异丁烷都有较高的化学吸附能力;SiO2能缓解表面Lewis碱位V=O和Mo=O的氧化能力,有利于选择氧化.     

Dispersion state and catalytic properties of vanadia species on the surface of V_2O_5/TiO_2 catalysts

The dispersion state and catalytic properties of anatase-supported vanadia species are studied by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), H2 temperature-programmed reduction (TPR) and the selective oxidation of o-xylene to phthalic anhydride. The almost identical values of the experimental dispersion capacity of V2O5 on anatase and the surface vacant sites available on the preferentially exposed (001) plane of anatase suggest that the highly dispersed vanadium cations are bonded to the vacant sites on the surface of anatase as derived by the incorporation model. When the loading amount of V2O5 is far below its dispersion capacity, the dispersed vanadia species might mainly consist of isolated VOx species bridging to the surface through V-O-Ti bonds. With the increase of V2O5 loading the isolated vanadia species interact with their nearest neighbors (either isolated or polymerized vanadia) through bridging V-O-V at the expenses of V-O-Ti bonds, resulting in the increase of the ra     

V2O5/SiO2催化剂的异丁烷选择氧化反应性能

 采用溶胶－凝胶法和浸渍法制备了V2O5／SiO2催化剂,并用XRD,IR,TPD和活性评价等手段对催化剂的表面构造、化学吸附性能和异丁烷选择氧化反应性能进行了研究．结果表明：催化剂表面由Lewis碱位V＝O双键的端氧和Lewis酸位V5＋构成,异丁烷分子主要通过甲基中的H双位吸附在催化剂表面的Lewis碱位上,异丁烯分子可通过甲基的H吸附在催化剂表面的Lewis碱位,也可通过C＝C双键吸附在催化剂表面的Lewis酸位上．在常压条件下,异丁烷选择氧化产物主要有异丁烯、甲基丙烯醛和甲基丙烯酸,其中深度氧化产物CO2主要由通过C＝C吸附的异丁烯继续反应生成．     

Porous V2O5-SnO2/CNTs composites as high performance cathode materials for lithium-ion batteries

Vanadium pentoxide (V₂O₅) exhibits high theoretical capacities when used as a cathode in lithium ion batteries (LIBs), but its application is limited by its structural instability as well as its low lithium and electronic conductivities. A porous composite of V₂O₅-SnO₂/carbon nanotubes (CNTs) was prepared by a hydrothermal method and followed by thermal treatment. The small particles of V₂O₅, their porous structure and the coexistence of SnO₂ and CNTs can all facilitate the diffusion rates of the electrons and lithium ions. Electrochemical impedance spectra indicated higher ionic and electric conductivities, as compared to commercial V₂O₅. The V₂O₅-SnO₂/CNTs composite gave a reversible discharge capacity of 198 mAh·g^?1 at the voltage range of 2.05–4.0 V, measured at a current rate of 200 mA·g^?1, while that of the commercial V₂O₅ was only 88 mAh·g^?1, demonstrating that the porous V₂O₅-SnO₂/CNTs composite is a promising candidate for high-performance lithium secondary batteries.     

氨法选择性还原氮氧化物 V2O5/TiO2-PILC催化剂的抗硫性能

选择性催化还原(SCR)是目前去除氮氧化物最有效的方法之一. V2O5/TiO2催化剂被广泛应用于氨法选择性还原氮氧化物(NH3-SCR)反应,但该催化剂存在工作温度高(300–400oC)及 SO2氧化率高引起设备腐蚀和管路堵塞等问题,开发低温 SCR催化剂具有重要意义.过渡金属氧化物(如 Fe2O3, MnOx和 CuO等)催化剂用于低温SCR先后见诸文献报道,但这些催化剂在 SO2和 H2O存在下易失活.近年来柱撑黏土(PILC)引起科学家广泛关注, Yang等首次将 V2O5/TiO2-PILC催化剂应用于 NH3-SCR反应,发现其催化活性高于传统 V2O5/TiO2催化剂.柱撑黏土基催化剂在 NH3-SCR反应中也显示出良好抗硫性能,但 V2O5/TiO2-PILC催化剂的抗硫机理至今尚未见深入研究.因此我们制备了一系列 V2O5/TiO2-PILC催化剂,采用原位漫反射红外等方法详细研究了其抗硫性能较好的原因.
　　首先采用离子交换法制备出 TiO2-PILC载体,之后采用浸渍法制备了不同钒含量(质量分数x/%=0,3,4,5)的xV2O5/TiO2-PILC催化剂.同时,制备了传统 V2O5/TiO2和 V2O5-MoO3/TiO2催化剂作为对比.活性评价结果显示,4V/TiO2-PILC催化剂具有最高的催化活性,其催化性能与传统钒钛催化剂相当.在160oC时, NO转化率可达80%以上.同时,4V/TiO2-PILC催化剂还具有较宽的反应温度窗口,在260–500oC范围内, NO转化率保持在90%以上.向反应体系中加入0.05% SO2和10% H2O后,在低温(160oC以下)时所有催化剂的反应活性都有一定提高,可能是由于 SO2的加入提高了催化剂的表面酸性.继续升高温度,4V/TiO2和4V6Mo/TiO2催化剂活性均明显下降,而4V/TiO2-PILC催化剂的活性则未出现明显下降.原位漫反射红外光谱结果显示, SO2在三种催化剂表面的吸附以表面硫酸盐或亚硫酸盐物种以及离子态 SO42–物种形式存在,而在4V/TiO2-PILC催化剂表面离子态 SO42–物种的量最少. X射线光电子能谱及 O2程序升温脱附结果显示,在4V/TiO2-PILC催化剂上,表面吸附氧(Oads)的量最少.综合上述分析可以得出,在 SO2气氛下,离子态 SO42–物种在 SCR催化剂表面的累积可能是导致其失活的主要原因,而离子态 SO42–物种的形成可能与催化剂表面吸附氧的量有关.     

一步法合成多级孔结构ZSM-5分子筛

多级孔结构ZSM-5分子筛的合成过程复杂。利用双模板剂,通过优化晶化条件(如晶化时间与晶化温度)和Si/Al物质的量比等一步水热晶化合成了具有多级孔结构的ZSM-5分子筛,并采用XRD、N₂吸附-脱附、吡啶红外吸脱附、SEM和TEM等方法对样品的晶体结构、孔道结构、表面酸性和形貌等进行了表征。结果表明,一步法合成多级孔结构ZSM-5分子筛的适宜条件是:晶化温度160-180℃,晶化时间24-96 h,反应物组成为SiO₂/Al₂O₃/Na₂O/CTAB/TPABr/H₂O=1/x/0.4/0.05/0.12/280,(x:50-240)。其中,晶化温度160℃、晶化时间48 h和以Si/Al物质的量比50的凝胶合成的样品具有有序的介孔(平均尺寸3.60 nm)结构、较高的结晶度和较强的酸性。