Application and challenge of rare earth automotive catalysts in CHINA Ⅵ

China is setting to roll out more strict emissions rule of CHINA Ⅵ Emission Standard which poses huge challenge to automotive catalytic technology.Rare earth elements are the key compositions of the catalysts coating.To develop multiple-component rare earth materials is an important way to improve the performance of the catalyst.The study concluded that quaternary or quinary rare earth materials for CHINA Ⅵ Emission Standard,can improve substantially the oxygen storage capacity and high thermal stability of the catalyst,after the modification by Pr/NdAT elements.It improved the utilization efficiency of precious metal.

Hydrothermal synthesis of mixed rare earth-alkali metal or ammonium fluorides

The recent results on hydrothermal synthesis of mixed rare earth-alkali or ammonium fluorides were presented. The initial ratios of the starting materials, pH value and reaction temperature were the critical factors for obtaining the single-phase product. Four main types of complex rare earth fluorides, AREF4, A2REF5, ARE2F7 and ARE3F10 (A=Na+, K+, Rb+, NH4+), appeared in the primary hydrothermal reactions. The correlation between cation sizes and the formation of mixed rare earth fluorides under mild hydro...

高纯金属钪制备研究进展

稀土元素钪是一种重要的稀土元素,广泛应用于合金、陶瓷等结构材料及燃料电池电解质、射频滤波器等功能材料领域。本文以高纯金属钪的制备工艺展开探讨,先后介绍了氟化钪、无水氯化钪的制取方法,然后详细阐述了卤化钪的金属热还原工艺和粗钪高温真空蒸馏提纯中不同杂质的处理方法,接着探讨了金属钪深度除杂相关的区熔、电迁移、真空电子束熔炼技术。最后指出,无水氯化钪镁热还原制备金属钪相比氟化钪钙热还原技术具有温度低、环境友好、成本小等优势。未来,金属钪的制备研究可集中于金属热还原无水氯化钪进行,通过多次高温真空蒸馏和电子束熔炼脱除杂质元素,使高纯金属钪产品纯度达到4 N甚至5 N级别。真空电子束熔炼、接力区熔法等技术在超高纯金属钪及其他稀土金属的制备领域具有广阔的发展前景。

吸附剂在含氟废水深度处理中的研究进展

金属冶炼、铝电解及电池生产等化工领域排放大量的含氟废水,实现含氟废水的深度处理(<1 mg/L),对保障人体的健康安全具有重要意义。阐述了现有吸附剂的分类、除氟机理及优缺点,总结了适合深度除氟的吸附剂及其改性方式,为含氟废水深度处理技术研究提供参考。

镨钕金属抛光废料回收工艺研究

室温(5~35℃)下,采用筛选、湿法磁选、酸化、草酸沉淀和焙烧等工序对镨钕金属抛光废料中的稀土、氟和铁进行回收循环利用。此方法得到的氧化镨钕和氟化镨钕具有较高的纯度,且稀土、氟和铁均具有较高的回收率,稀土的回收率为96%以上,氟的回收率为90%以上,铁的回收率为93%以上。回收处理酸不溶物过程中产生的废酸和水洗筛上料的粉尘和洗水均可返回下批料的处理中得以回收利用。整套工艺既可实现二次资源的利用,又无废渣的产生,节省生产成本的同时解决了环保中的废渣问题。本工艺提供的镨钕金属抛光废料回收处理方法简单易操作,易于工业化。

离子色谱法测定稀土金属及氧化物中氟量

采用阴离子分离柱AS9(4×250mm)分离,以电导检测器检测,以9.0mmol/LNa2CO3为流动相,以标准曲线法为定量方法,测定稀土金属及氧化物中氟离子的含量。方法检出限为0.010μg/mL,测定下限为0.0050%,回收率为95%～104%,氟含量在0.02%时方法的相对标准偏差为0.084%。方法操作简便、快捷,结果准确、可靠。

微乳液法一步制备NaYF_4∶Yb^(3+),Ho^(3+)@Au

稀土氟化物纳米材料及其贵金属复合物具有独特的光、电、磁性质,在生物标记、光学储存、显示、防伪等领域有着广泛的应用,已成为材料科学领域的研究热点之一。采用微乳液法制备了NaYF_4∶Yb^(3+),Ho^(3+)和NaYF_4∶Yb^(3+),Ho^(3+)@Au复合材料,XRD测试表明NaYF_4∶Yb^(3+),Ho^(3+)的结晶情况良好,无杂质峰,为立方相,NaYF_4∶Yb^(3+),Ho^(3+)@Au产物的衍射峰中同时含有NaYF_4与Au两种晶相;SEM图像显示两种纳米粒子均为形貌、尺寸较为均一的球形粒晶为58nm左右;上转换光谱中显示Ho^(3+)在484,682和767nm处具有很高的发光强度,分别对应于~5S_2→~5I_8,~5F_5→~5I_8,~5S_2→~5I_7跃迁。

稀土金属及氟化稀土中氯量的测定

本文研究了稀土金属中氯根测定的不稳定原因 ,采用正交实验方法 ,建立了既经济又稳定的测定方法。

稀土元素在水体除氟中的应用及进展

水环境中的氟污染已被认为是全球严重威胁人类健康的主要问题之一,吸附法被认为是最具有发展前景的水体除氟技术,各国学者也在研发吸附性强和环境友好的新型吸附剂。对稀土化合物和负载稀土元素的吸附剂在除氟中的应用进行了总结,发现稀土化合物的吸附氟能力强,多金属氧化物、生物材料、金属有机骨架和硅基材料等经负载稀土元素改性后制备的新型吸附剂也表现出良好的除氟能力;不同材料和官能团的协同作用可以有效提高吸附剂的除氟能力。在总结现有除氟剂的基础上,对新型除氟吸附剂的研发进行了展望。

Precious metal-support interaction in automotive exhaust catalysts

Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a cartier for active compotmds in catalysts but also can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature; meanwhile, noble metals can also enhance the redox performance and oxygen storage capacity of support. The mechanism of metal-support interactions mainly includes electronic interaction, formation of alloy and inward diffusion of metal into the support or covered by support. The form and degree of precious metal-sup- port interaction depend on many factors, including the content of precious metal, the species of support and metal, and preparation methods. The research results about strong metal-support interaction （SMSI） gave a theory support for developing a kind of new cata- lyst with excellent performance. This paper reviewed the interaction phenomenon and mechanism of precious metals （Pt, Pd, Rh） and support such as A1203, CeO2, and CeO2-based oxides in automotive exhaust catalysts. The factors that affect SMSI and the catalysts developed by SMSI were also discussed.

Oxygen Storage Capacity of Pt-, Pd-, Rh/CeO_2-Based Oxide Catalyst

CZO （CeO2-ZrO2） and CZYO （CeO2-ZrO2-Y2O3） series of mixed oxides were prepared by coprecipitaion, and a part of these oxides were loaded with precious metals （PM）. XRD, BET, and oxygen storage capacity （OSC） investigations were performed on samples aged at 750, 900, and 1050 ℃. It was observed that BET surface area and OSC showed a marked decrease in CeO2 aged at high temperature, and the erystallite size showed an obvious increase. The CZO samples consist of cubic- and tetragonal crvstal phases, and their crystallite size increase rapidly when aged at high temperature. The CZYO samples consist of single crystal phase when the content of Y exceeds 0.15 mol, and their erystallite size increases slowly during high-temperature aging. It is concluded that additive Y can stabilize the performance of CZYO oxides. In the aged CZO and CZYO mixed-oxide systems, addition of a small amount of precious metals （Pt, Pd, Rh） increased the rate of reduction and led to an obvious improvement in OSC. OSC of CZO and CZYO with precious metals are related to their composition and the type of precious metal.

Recent progress on upconversion luminescence enhancement in rare-earth doped transparent glass-ceramics

The upconversion（UC） of the rare earth doped glass-ceramics has been extensively investigated due to their potential applications in many fields, such as color display, high density memories, optical data storage, sensor and energy solar cell, etc. Many series of them, especially the oxyfluorides glasses containing Ba2 LaF 7 nanocrystals were studied in this review work, due to the thermal and mechanical toughness, high optical transmittance from the ultraviolet to the infrared regions, and a low nonlinear refractive index compared to the other commercial laser glasses. Moreover, the energy transfer（ET） between the rare earth ions and transition metals plays an important role in the upconversion process. The cooperative ET has been researched very activly in UC glasses due to applications in the fields of solar cells, such as in the Er/Yb, Tm/Yb, Tb/Yb, Tb/Er/Yb and Tm/Er/Yb couples. The present article reviews on the recent progress made on：（i） upconversion materials with fluoride microcrystals in glasses and the mechanisms involved, including the UC in double and tri-dopant RE ions activated fluoride microcrystal, energy transfer process; and（ii） the effect of the metal Mn and nanoparticles of Au, Ag, Cu on the enhancement of UC emissions. Discussions have also been made on materials, material synthesis, the structural and emission properties of glass-ceramics. Additionally, the conversion efficiency is still a challenge for the spectra conversion materials and application; challenge and future advances have also been demonstrated.

Influence of Ce_(0.35)Zr_(0.55)Y_(0.10) Solid Solution on Performance of Pt-Rh Three-Way Catalysts

Ce0.35Zr0.55Y0. 10 solid solution was prepared by co-precipitation technique and characterized by specific surface area measurements （BET） and X-ray diffraction （XRD）. Ce0.35Zr0.55Y0.10 was used to prepare low Pt-Rh threeway catalyst （TWC）, and its influence on the performance of TWC was investigated. The results revealed that Ce0.35 Zr0.55Y0.10 had a cubic structure similar to Ce0.50Zr0.50O2 and its specific surface area can maintain higher than Ce0.50 Zr0.50O2 after 1000 ℃ calcination for 5 h. Being hydrothermal aged at 1000 ℃ for 5 h, the catalyst containing Ce0.35 Zr0.55Y0.10 still exhibited higher conversion of C3H8, CO and NO and lower light-off temperature in comparison with Ce0.50Zr0.50O2 TWC.

氟化物体系电解稀土氧化物制备稀土金属研究

概述了国内外氟化物熔盐电解制取稀土金属及合金的发展历程,分析总结了实验室中对稀土氟化物熔盐体系研究,其中包括物化性质和电化学性质的研究。数值模拟技术近年来在熔盐电解法制备稀土金属中也起到了很大的作用,因此概述了数值模拟技术在熔盐电解制备稀土金属的发展。