粗四氯化钛除钒工艺现状及进展

论述了海绵钛和钛白生产中四氯化钛精制除钒工艺生产现状和研究进展,从技术、经济和环保角度对几种主要的除钒方法进行了综合性的评价和探讨。     

Yb3+掺杂KLa(WO4)2激光晶体生长与光谱分析

采用提拉法生长出掺镱钨酸镧钾[Yb:KLa(WO4)2,Yb:KLW]晶体,测试了晶体的红外光谱和Raman光谱,对出现的振动模式进行了归属.从X射线衍射分析得到晶胞参数a=b=0.532 nm,c=1.189 nm.通过热重-差热分析得到晶体的熔点为1 119 ℃,在熔点以下没有相变.测试了晶体的吸收光谱和荧光光谱,计算了相应的光谱参数.结果表明:该晶体发射波长为1 021 nm,在931,981 nm附近有较强、较宽的吸收峰,适合用InGaAs半导体激光泵浦.     

Mn2+在Zn2SiO4中的发光

利用Sol-gel法制备掺Mn^2 的Zn2SiO4的前驱体，并将前躯体在弱氧化气氛下在1000℃煅烧2h，得到掺Mn^2 的Zn2SiO4试样。X射线衍射分析确定试样为α-Zn2SiO4晶相。荧光分析测定试样的激发光谱和发射光谱。结果显示Mn^2 掺杂的α-Zn2SiO4可发蓝色和绿色荧光，这一结果显然不同于以前的文献报道。同时，我们讨论了Mn^2 在Zn2SiO4中产生这一新型发光性质的机理。     

催化动力学光度法测定痕量钒(Ⅴ)的研究

研究了在 p H=4及没食子酸存在下 ,微量钒 ( )催化溴酸钾氧化邻苯二胺的动力学条件 ,建立了催化动力学光度法测定痕量钒 ( )的新方法。方法的测定范围为 0～ 0 .0 2 5 μg· 2 5 m L- 1 ,检出限为 1.18× 10 - 6 g·L- 1 ,相对标准偏差为 4 .6 3% (n=10 ) ,线性回归方程为△ A=2 5 .6 6 c(μg· 2 5 m L- 1 ) - 0 .0 15 7(r=0 .9997) ,表观摩尔吸光系数ε4 6 0 nm=3.2 7× 10 7L· m ol- 1 · cm- 1 。该法灵敏度高 ,选择性好 ,直接应用于水样和食品样中痕量钒( )的测定 ,结果满意     

浅谈国内外钒催化剂的质量差异

从化学组分、强度、活性、物相结构、孔容积及孔径分布等方面，对国产S101-2H、S108-1H钒催化剂和进口LP120、LP110钒催化剂进行剖析、对比。结果表明，国产催化剂强度比进口催化剂低30％左右；国产催化剂测定活性与进口催化剂相近，但实际使用活性明显劣于进口催化剂；进口催化剂载体中存在方英石、硫酸铝钾相，而国产催化剂没有；进口催化剂孔径分布较宽，主要孔径分布在0．50～1．50μm，而国产催化剂孔径分布较窄，主要孔径分布在0．060～0．30μm，不利于反应气体在催化剂内部的扩散。鉴此，建议采用高温煅烧载体，降低其有机物含量；优化配方，填加无机粘结剂；改进成型设备等措施，提高催化剂的强度和活性。     

Bulk and Surface Properties of a VPO Catalyst Used in an Electrochemical Membrane Reactor: Conductivity-, XRD-, TPO- and XPS-study

In the first part of this work, the electrical conductivity of vanadium phosphorous oxide (VPO) catalyst was investigated by means of the 2-probe EIS method. The VPO showed an extremely low conductivity at low oxygen partial pressure, which is the prevailing condition in the anodic compartment in an electrochemical membrane reactor (EMR). In the second part of this study, fresh as well as VPO catalyst already used in an EMR were characterised with XRD, XPS and temperature programmed oxidation (TPO). The XRD measurements revealed an unchanged bulk phase structure after operation in the EMR. Significant differences in the average oxidation states of vanadium in the catalyst layer in the EMR were determined via XPS, where the catalyst surface facing the electrolyte membrane was more oxidised than the surface facing the anodic gas compartment. The lowered uptake and release of oxygen was observed in TPO experiments for the catalyst used in the EMR.     

不同Li/Nb摩尔比In∶Fe∶LiNbO_3晶体的生长及其光学性能

在Li NbO3(LN)中掺摩尔分数为1%的In和掺质量分数为0.03%的Fe,用提拉法技术生长具有不同n(Li)/n(Nb)[n(Li)/n(Nb)=0.94,1.05,1.20,1.38]的In∶Fe∶LN晶体。测试不同n(Li)/n(Nb)的In∶Fe∶LN晶体的吸收光谱、抗光致散射能力和指数增益系数,并计算晶体的有效载流子浓度。结果表明晶体样品随着n(Li)/n(Nb)增加,吸收光谱的吸收边发生紫移,抗光致散射能力增加,指数增益系数和有效载流子浓度增大。采用n(Li)/n(Nb)=1.38的In∶Fe∶LN晶体作记录介质,n(Li)/n(Nb)=1.05的In∶Fe∶LN晶体作位相共轭镜进行全息关联存储实验。实验表明存储系统具有实时处理,成像质量好,信噪比高和能反复使用等优点。     

Reaction pathway of benzonitrile formation during toluene ammoxidation on vanadium phosphate catalysts

The reaction pathway of the ammoxidation of toluene on (VO)₂P₂O₇ used as catalyst and the interaction of potential intermediates with the pyrophosphate were studied by spectroscopic techniques (FTIR, EPR), temperature-programmed chemisorptions/ reactions (TPD, TPRS) and transient studies such as the temporal analysis of products (TAP) technique. NH₃ is chemisorbed on the catalyst surface, forming three different species, i.e., NH ₄ ⁺ ions located on BrØnsted sites, coordinatively bound NH₃ on Lewis sites and NH ₂ ^– groups, presumably P-NH₂. Toluene that is probably adsorbed on Lewis sites reacts in a first step to a benzyl radical. A subsequent partial oxidation by interaction of V^IV=O groups generates a V...O=CH-C₆H₅ surface structure. This benzaldehyde-like surface species reacts with adsorbed NH₃ according to a Langmuir-Hinshelwood mechanism. TAP experiments on ammonium-containing vanadium phosphates revealed that NH ₄ ⁺ ions could act as potential N-insertion species. No formation of benzylamine as well as the generation of V=NH surface groups as possible intermediates or N-insertion sites were observed.     

Synergistic effects of doped Fe3+ and deposited Au on improving the photocatalytic activity of TiO2

Fe³⁺ doped together with Au deposited TiO₂ (Au/Fe³⁺–TiO₂) was successfully prepared, which shows excellent photocatalytic activity for degradation of methyl orange (MO) under both UV and visible light (λ > 420 nm) illumination. Fe³⁺ has been confirmed by EPR to substitute for Ti⁴⁺ in the TiO₂ lattice, and Au exists as Au⁰ on the surface of the photocatalyst indicated by the results of XRD. Fe³⁺ and Au have synergistic effects on improving the photocatalytic activity of TiO₂. A proposed mechanism concerning the synergistic effects is discussed to explain the improvement of the photocatalytic activities.     

Time-of-flight studies on catalytic model reactions

Time-of-flight spectroscopy (TOF) and REMPI-TOF (resonance enhanced multi-photon ionization-TOF) were applied to measure the angular and translational energy distribution, as well as the internal state resolved energy distribution of desorption and reaction products on some model systems. Desorption of hydrogen and deuterium from clean and modified Pd(111) surfaces was studied, where the palladium sample was part of a permeation source. Water formation by reaction of oxygen with hydrogen on palladium was investigated by using different types of hydrogen supply: molecular H₂ exposure and atomic H exposure from the gas phase, as well as H exposure by permeating hydrogen. Vanadium oxide nanostructures on Pd(111) were prepared and the influence on D₂ desorption and D₂O production was investigated with the permeation technique. Additionally, deuterium desorption from sulfur and oxygen covered V(111) and V(100) surfaces was studied by TOF and REMPI-TOF spectroscopy. From the TOF spectra information concerning the reaction and desorption dynamics (activation barriers) could be gained.