利用失效钒电解液回收钒制备偏钒酸铵工艺

为了提取失效钒电解液中有价钒元素,对全钒氧化还原液流电池失效钒电解液的回收利用进行了研究。在常温常压条件下,以氯酸钠作氧化剂对失效钒电解液进行深度氧化,使低价钒全部转变成五价钒,然后通过浓缩、沉钒、干燥等工艺过程,得到具有高附加值的偏钒酸铵。分析了回收过程的工艺原理,探讨了回收工艺的工艺条件。结果表明：NaClO₃对失效钒电解液的氧化是影响钒回收率的关键工艺过程,V⁴⁺：NaClO₃的最佳摩尔比为1：0.2,V³⁺：NaClO₃的最佳摩尔比为1：0.4;沉钒的最佳工艺条件为：钒液浓度为25～30g/L,pH为8.0～8.5,沉钒温度为50～60℃,加铵系数K为1.0～1.2,沉钒时间为80～120min。该工艺具有钒回收率高、成本低、操作简便、对环境友好等优点,在最佳工艺条件下钒的回收率可高达99%左右,为全钒液流电池失效钒电解液的回收利用提供了一条新途径。     

提钒技术研究进展

综述了1980-2015年期间钒矿、含钒磷铁、废钒催化剂、钢渣和石煤等常见提钒原料之提钒技术的研究进展,对目前较具代表性的提钒工艺技术进行了较系统地分析总结,将这些提钒工艺技术归结为冶金工艺、焙烧工艺、湿法提钒、其他新型工艺四大类进行分类阐述;对各类提钒工艺技术进行了举例说明,对其基本过程进行了概述,并对其优缺点进行了较客观的分析和评述。在此基础上,发现和指出了长期以来我国提钒工艺过程中普遍存在的主要问题:首先,钒资源提钒的工艺技术水平仍然较低,废弃物较多,环境污染较严重;其次伴生矿或元素利用较低,钒资源综合利用程度较低。最后,指出了提钒技术的发展趋势:在强调环境保护的背景下,乞待开发新的环境污染较少、钒资源综合利用程度较高的提钒工艺。     

The effect of vanadium sources on the synthesis and catalytic activity of VMCM-41

Mesoporous VMCM-41 was synthesized hydrothermally using various vanadium sources, viz, tetravalent vanadium such as vanadyl sulfate and vanadyl acetylacetonate, as well as pentavalent vanadium like sodium vanadate and ammonium vanadate. The influence of different vanadium sources on the framework substitution of vanadium, as well as their catalytic activity for the oxidation of cyclohexane, was investigated. Among the different vanadium stocks, the tetravalent vanadium sources showed maximum vanadium incorporation in the silicate framework of MCM-41. As a consequence, these catalysts gave much higher substrate conversion and excellent product selectivity. On the other hand, the catalysts prepared from pentavalent vanadium sources showed lower activity owing to the smaller amounts of vanadium in the matrix. Although the activity of the catalyst slightly decreased after first recycle as due to leaching of small amounts of active vanadium species, it however remained nearly the same even after several recycles. This was further confirmed by washing experiments wherein non-framework vanadium ions were removed upon ammonium acetate treatment; the washed catalysts showed a similar activity to those of the recycled catalysts. Thus, recycled/washed VMCM-41 behaves truly as heterogeneous catalyst. Furthermore, the influence of pore size of the catalyst was tested for the oxidation of bulkier substrate, viz, cyclododecane.     

铁水中钒氧化及钒铁尖晶石形成的研究

以热力学计算结果为依据对铁水中钒的氧化行为及钒渣中钒、铁存在的价态进行了理论分析,模拟铁水中钒的氧化反应制取钒渣,运用X衍射分析了钒铁尖晶石的分子组成,研究了FeO对钒铁尖晶石形成的影响.结果表明,铁水中的钒主要被氧化成V3+,也有少部分被氧化成V2+,钒渣中的铁有Fe2+和Fe3+两种形式;当初渣中氧化剂(FeO)的摩尔量与铁水中V的摩尔量比X<2时,钒渣中的钒铁尖晶石以FeV2O4的形式存在;当23时,钒铁尖晶石以Fe2VO4的形式存在.     

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular structure of vanadium in water and in the solid state and an overview of the spectroscopic techniques enabling to study the chemistry of supported vanadium oxides. In the second part, it will be shown that advanced spectroscopic tools can be used to obtain detailed information about the coordination environment and oxidation state of vanadium oxides during each stage of the life-span of a heterogeneous catalyst. Three topics will be discussed: (1) the molecular structure of supported vanadium oxide catalysts under hydrated, dehydrated and reduced conditions, including the parameters, which influence the molecular structures formed at the surface of the support oxide; (2) elucidation of the active surface vanadium oxide during the oxidation of methanol to formaldehyde, the reaction mechanism and the vanadium oxide---support effect; and (3) deactivation of fluid catalytic cracking (FCC) catalysts by migration of vanadium oxides and the development of a method preventing the structural breakdown of zeolites by trapping the mobile vanadium oxides in an aluminum oxide coating.     

A Mechanistic Study of Vanadium-Sorbent Surface Interaction at High Temperature

A mechanistic study of vanadium-sorbent interaction at high temperature was conducted to investigate the underlying mechanisms of sorbent injection for controlling vanadium emissions from combustion systems. Both calcium- and silica-based sorbents successfully reduced the formation of vanadium submicron particles. The capture of vanadium was found to correlate well with sorbent surface area, demonstrating that the dominant mechanism was condensation. Bimodal lognormal modeling based on the experimental conditions verified that condensation on injected sorbents was a very effective means of scavenging vanadium vapor. However, if vanadium vapor quickly nucleated (e.g., through gas phase hydrolysis in the studied system) to form a large number of ultrafine particles, their much larger specific surface area overshadowed that of the sorbent particles and scavenged the rest of the vanadium vapor. Using the residence times employed in this study, intra-coagulation of and condensation onto these ultrafine vanadium particles was not an effective means of growing the particles to the supermicrometer range. Such a scenario decreased the effectiveness of the sorbent technique. Consequently, enhancing direct vanadium condensation onto sorbent particles and suppressing vanadium nucleation is critical to successful reduction of vanadium emissions from combustion sources.     

不同老化气氛对催化裂化捕钒剂性能的影响

通过改变老化处理气氛,研究其对催化裂化捕钒剂性能的影响。在水蒸汽和氮气气氛下,含有捕钒组分的催化剂与不含捕钒组分的催化剂催化活性接近,捕钒组分的捕钒效果不显著。在水蒸汽和空气气氛下,随着空气体积分数由0增加到50%,不含捕钒组分的催化剂微反活性由58%升高到69%,重油转化率由68. 82%升高到74. 02%;含有捕钒组分的催化剂微反活性由60%升高到73%,重油转化率由70. 04%升高到77. 10%,焦炭和干气选择性也优于不含捕钒组分样品,体现了捕钒组分的捕钒效果。通过控制老化气氛中SO2质量分数为0或0. 16%,考察SO2对捕钒组分的影响,结果表明,SO2对此捕钒组分的性能影响较小。     

石煤钒矿硫酸浸出制备五氧化二钒试验研究

石煤钒矿中的钒以铝氧化钒和氧化钒水合物赋存于矿石云母和黏土矿物中,并以低价态产出。将石煤钒矿破碎磨粉至粒度小于0.15 mm,在添加剂（含氧化剂和络合剂的无机盐混合物）和硫酸的协同作用下,在加热和搅拌条件下,用硫酸直接浸出石煤钒矿中的钒,矿粉中钒的浸出回收率可达76%以上。浸出液经调pH、氧化、分离富集、精钒制备等工序,可以制备出产品质量优于YB/T 5304-2011《五氧化二钒》98级标准的五氧化二钒产品。     

弱氧化剂CO2(g)对含钒铁水吹炼制钒渣的影响

采用弱氧化剂选择性氧化含钒铁水,先弱氧化脱硅,再强氧化提钒,以获得高品位的钒渣。对弱氧化剂CO2浅度氧化含钒铁水炼制钒渣进行了理论分析,确定脱硅保钒反应的物理化学条件,研究了温度、CO2气体流量、搅拌和熔剂等因素对脱硅保钒反应的影响及脱硅反应产物的分布。结果表明,温度1450℃及CO2气体流量1 L/min、有搅拌条件下,脱硅率高达68.62%,而钒氧化率仅为0.73%。     

浅谈五氧化二钒的市场状况和生产工艺

介绍了五氧化二钒的运用领域,并对目前国内、外五氧化二钒的生产及消费状况进行了分析;列举了五氧化二钒不同的生产工艺,并分别讲述了各种工艺流程的技术特点;最后对五氧化二钒产品的市场进行了预测和展望。     

ESR studies on vanadocene/cocatalyst systems for ethylene polymerization

Three vanadocene–cocatalyst catalytic systems for ethylene polymerization—Cp₂ZrCl₂/Al₂Et₃Cl₃ [dichlorobis(η‐cyclopentadienyl)vanadium/ethylaluminumsesquichloride], Cp₂ZrCl₂/MAO [dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane] and Cp₂ZrCl₂/AlEt₃ [dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum]—were monitored by electron spin resonance (ESR) spectroscopy. It was found that at least a certain kind of vanadium complex is formed after mixing dichlorobis(η‐cyclopentadienyl)vanadium with ethylaluminumsesquichloride. After introducing ethylene, a new kind of vanadium complex is detected by ESR. Ethylene can be polymerized by using a dichlorobis(η‐cyclopentadienyl)vanadium/ethylaluminumsesquichloride catalytic system. These results possibly indicate that the vanadium complex exists in the forms ClCp₂VClEtAlCl₂ and ClCp₂VClEtAlClEt, which are responsible for forming active centers. The Dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum systems also were monitored by ESR. Completely different spectra were recorded compared to those of the dichlorobis(η‐cyclopentadienyl) vanadium/ethylaluminumsesquichloride system. Ethylene almost cannot be polymerized by the dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum catalytic systems, showing that resultant vanadium complexes of dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum catalytic systems are different from that arising from the dichlorobis(η‐cyclopentadienyl)vanadium/ethylaluminumsesquichloride system. Plausible mechanisms are suggested for this. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1188–1194, 2001     

粗四氯化钛有机物精制除钒尾渣提钒技术

从四氯化钛有机物精制除钒尾渣中提钒并制备V2O5产品,研究了精制除钒尾渣焙烧温度、浸出剂加入量、液固比、浸出温度、浸出时间对尾渣中钒转化和溶出率的影响。结果表明,焙烧温度大于600℃时,可高效脱除精制除钒尾渣中的碳和氯(?0.1%),且低价钒被氧化为高价,钒主要以V2O5形式存在。对焙烧后的尾渣以Na2CO3水溶液为浸出剂,液固比6 mL/g及80℃下浸出60 min,钒浸出率为85.5%,浸出液仅含少量Si, Al, Ti杂质,以NH4+:V=2.5:1(摩尔比)直接加铵盐沉钒,得到NH4VO3,经干燥、煅烧制得V2O5产品,可满足99级粉钒指标要求,全流程钒收率为75%。     

高硅铁水转炉提钒对钒渣质量的影响及对策

铁水[Si]对转炉提钒钒渣质量影响较大,铁水[Si]抑制钒渣的氧化,钒渣渣态稀,导致钒渣品位下降、产渣率下降、半钢余钒偏高。通过采用提钒复吹工艺、在提钒终点加入碳质还原剂浓缩钒渣、预脱硅技术、优化提钒冷却剂、供氧时间和氧枪枪位等措施,钒渣品位由原来的15.2%提高到目前的16.2%。     

钒渣提取五氧化二钒的研究

研究了从玉钢钒渣中提取五氧化二钒工艺。采用X荧光光谱分析和化学滴定法,系统地研究了添加剂用量、焙烧温度、沉钒温度和pH等因素对玉钢钒渣中五氧化二钒回收率的影响,并制定了合理的提钒流程参数。通过实验发现,在最佳流程参数条件下(添加剂与钒渣质量比为22:100,焙烧温度为850℃保温2h,沉钒时水浴温度为95℃,沉钒pH为2.2),五氧化二钒的回收率达到了85.4%,且五氧化二钒的纯度大于99%。     

废钒催化剂综合利用的实验研究

研究了以废钒催化剂为原料,经水浸-还原酸浸-萃取-沉钒等环节制取五氧化二钒、硫酸钾、液体硅酸钠的方法。考察了以三正辛胺（TOA）-仲辛醇-煤油溶液为萃取液提钒的最佳工艺条件： 将废钒催化剂磨碎至 375 μm左右,经过水浸、还原酸浸后,合并其浸出液进行氧化,在水相pH为2.3时,用9%的TOA-3%的仲辛醇-88%（均为质量分数）的煤油溶液萃取, 在浸取时间为2.5 min条件下, 经三级萃取, 钒的萃取率达99%以上;在pH>8、反萃取剂为0.25 mol NaOH+0.25 mol NaCl、反萃时间为3 min条件下, 经三级反萃, 钒的反萃取率达99.4%。在此工艺条件下, 钒、钾的回收率分别达到91.5%和93.8%,产品五氧化二钒、硫酸钾、液体硅酸钠的主要成分含量均达到相应国家标准要求。     

The effect of the nature of vanadium species on benzene total oxidation

The nature of the vanadium species present on V₂O₅/Al₂O₃ catalysts was investigated by using solid state ⁵¹V NMR, diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD) and temperature programmed reduction (TPR). ⁵¹V NMR and DRS analyses indicated the presence of V⁵⁺ in tetrahedral symmetry at low vanadium loading. A surface polymeric vanadium species and/or the bulk crystalline V₂O₅ were mainly observed at high vanadium loading as also detected by XRD. The positions of the absorption edges determined through the UV–VIS spectra allowed distinguishing between various tetrahedral symmetries. After TPR, the average oxidation state of vanadium depended on the vanadium content. The nature of vanadium species was related to the catalyst behavior on the benzene oxidation reaction. The catalysts containing high vanadium content were more active suggesting that a high amount of V⁴⁺ is responsible for the higher activity.     

Color and Vanadium Valency in V-Doped ZrO2

The distribution and chemical states of vanadium in V-doped ZrO₂ were studied to clarify the origin of the color of vanadium-zirconium yellow pigment in comparison with vanadium-tin yellow pigment. ESCA data and measurements of lattice constants of V-doped ZrO₂ revealed that vanadium was dissolved mainly as V⁴⁺ substituting for Zr in ZrO₂ lattice, and its solubility limit was 0.5 wt% as V₂O₅. It was found that the yellow color of vanadium-zirconium yellow was produced predominantly by the dissolved vanadium and that the contribution of vanadium oxide on ZrO₂ grains to the yellow color was about 1/30 of that of the dissolved vanadium when compared on the basis of equimolar quantity of vanadium. Most of the undissolved vanadium oxide was in an amorphous or a poorly crystallized state.     

钠化焙烧转炉钒渣粉体分形生长的演化行为

转炉钒渣焙烧提钒技术效率低,过程涉及化学反应、传递及相变过程,蕴含物相分形生长的动力学行为。对钒渣分形变化规律的研究有助于促进钒的定向转化,进而对工业提钒具有指导意义。根据金相电镜图,使用“周长-面积法”对不同焙烧条件下钒渣粉体分形维数进行计算,得到分形维数变化与物相转化的规律。结果表明,焙烧前硅相、钒相紧密包裹,分形维数数值为1.60~2.00;加入碳酸钠焙烧后尖晶石破坏,钒相逐渐分离,使分形维数小于1.20;随着钠盐加入量的增加,物相分形维数逐渐下降;二次焙烧后,稳定的钒酸钠生成,体系趋于稳定,使得分形维数进一步下降为1.10~1.20。     

Characterisation of alumina-supported vanadium oxide catalysts by kinetic analysis of H2-TPR data

Alumina-supported vanadium oxide catalysts with vanadium contents of 2, 5 and 11 wt.% were prepared by incipient wetness impregnation and characterised by XRD, Raman spectroscopy and H₂-TPR. The catalysts with the low vanadium contents contained vanadium mainly in the well-dispersed phase, but the catalyst with the highest vanadium content contained also some crystalline AlVO₄ according to XRD and Raman spectroscopic results. The reduction kinetics of the vanadium catalysts was modelled based on the hydrogen consumption during the TPR. The reduction kinetics could be described with a single-reducible-site random nucleation model for the catalyst containing the lowest amount of vanadium. The reduction kinetic models for the other catalysts required a combination of multiple processes to describe the experiments properly. In the catalyst with 5 wt.% V, a part of vanadium species possibly reduces as a homogeneous random nucleation process, but topochemical reduction by nuclei growth also takes place. In the catalyst with 11 wt.% V, reduction by nuclei growth seems to be the predominant reduction mechanism. The characterisation of the reduced catalysts by XRD and during reduction by Raman spectroscopy enabled the identification of the features of the TPR profiles.     

Al2O3或SiO2负载钒氧化物催化剂的紫外-拉曼光谱比较研究

用柠檬酸络合助溶的等体积浸渍法制备了氧化铝和氧化硅负载的系列钒氧化物催化剂，使用紫外-拉曼光谱对催化剂的结构进行了表征。结果表明，负载钒氧化物的结构与钒的负载量和载体类型有关，在低钒负载量时以隔离的钒氧物种为主；在高负载量时，钒氧化物在γ-Al₂O₃载体上以聚合的钒氧物种和V₂O₅共存，在SiO₂载体上主要以隔离的钒氧物种和V₂O₅形态为主，并有少量聚合的钒氧物种。