双稀土氟氧化物Sm-La-O-F催化剂的AFM研究

双稀土氟氧化物ＳｍＬａＯＦ具有良好的乙烷氧化脱氢（ＯＤＥ）催化性能，特别是对于Ｓｍ２Ｏ３ＬａＦ３（１∶１摩尔比），在９７３Ｋ，乙烯选择性为８９７％，乙烷转化率为２２１％，是目前报道的具有高乙烯选择性的ＯＤＥ反应催化剂．比表面积和ＸＲＤ测试表明，Ｓｍ２Ｏ３ＬａＦ３催化剂体相是由单一相结构的双稀土氟氧化物Ｓｍ２／３Ｌａ１／３ＯＦ组成，比表面积较小．原子力显微镜（ＡＦＭ）研究表明，该催化剂的表面颗粒排布规整致密，粒径均匀；而其它乙烯选择性较低的催化剂颗粒排布较为松散，颗粒大小不一．     

Chromatographic separation of inorganic ions on thin layers of lanthanum silicate ion-exchanger

Summary Thin layers of lanthanum silicate have been used to study the chromatographic behaviour of 28 metal ions in aqueous and mixed systems. As³⁺, Mo⁶⁺, Sb³⁺, Ti⁴⁺ and others can be easily separated from a number of inorganic ions. Fast ternary and binary separations have also been achieved and various separations are discussed. It is shown that Alberti's relation is also obeyed by thin layers of lanthanum silicate. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

甲烷在SrO-La_2O_3/CaO催化剂上的氧化偶联 Ⅰ.SrO对La_2O_3/CaO催化剂的助催化作用

在常压流动反应装置上评价了一系列La_2O_3/CaO催化剂和SrO-La_2O_3/CaO催化剂。实验表明:La_2O_3/CaO体系是很好的甲烷氧化偶联催化剂。在1073K和CH_4:O_2:He=4:1:5(总流速120ml/min)的实验条件下,20％La_2O_3/CaO催化剂上的甲烷转化率为26％,C_2选择性为53％;加入助剂SrO(15—20％)后,在同样实验条件下,甲烷转化率为29％,C_2选择性为66％。表明SrO对La_2O_3/Cao催化剂有明显的促进作用。用XRD,XPS和TPD(CO_2-TPD和O_2-TPD)技术表征了SrO-La_2O_3/CaO催化剂体系,结合反应评价结果,认为SrO的促进作用可以归结为:(1)调变了催化剂的碱性强度分布,提高了催化剂表面强碱中心的数目;(2)提高了La_2O_3的分散度;(3)抑制了催化剂的低温氧吸附物类。     

Stability and transport properties of La<Subscript>2</Subscript>Mo<Subscript>2</Subscript>O<Subscript>9</Subscript>

La₂Mo₂O₉ samples were prepared from freeze-dried powder precursors and characterized by XRD, TG/DTA, SEM, electrical and electrochemical measurements. Pellets with different density were obtained by sintering at temperatures between 900 and 1100 °C to obtain nearly dense samples with grain sizes in the range 1–8 m. The electrical conductivity was measured using impedance spectroscopy. The capacitance and relaxation frequencies of the main contributions to the spectra were used to ascribe the contributions of grain interiors and internal interfaces, and their temperature dependence. A coulometric titration technique was used to evaluate the change of oxygen stoichiometry under moderately reducing conditions, and to estimate the stability limits under strongly reducing conditions. An ion-blocking method was used to evaluate the onset of n-type conductivity, and a combination of these results with total conductivity measurements was used to obtain the ionic transport number. A combination of oxygen stoichiometry changes and ion-blocking results was used to obtain estimates of mobility.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

RING-OPENING POLYMERIZATION OF l,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS(2,6-DI-TERT-BUTYL-4-METHYLPHENOLATE)

The ring-opening polymerization of 1,4-dioxan-2-one (PDO) was carried out by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as novel single component initiator. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly(1,4-dioxan-2-one) (PPDO) were explored. PPDO with high viscosity average molecular weight of 1.95×105 can be prepared at 40℃when [PDO]/ [La(OAr)3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a "coordinationinsertion" mechanism with selective rupture of acyl-oxygen bond of PDO.     

稀土单氧化物发射光谱法的研究I.混合稀土浓集物中钐的双波长测定

报道了空气乙炔火焰中ＳｍＯ蒸气的发射光谱行为，试验了Ｌａ、Ｎｄ、Ｅｕ、Ｙ对ＳｍＯ发射强度增强作用，在大量Ｌａ存在下，ＳｍＯ的发射强度与其浓度成正比关系。用大量Ｌａ作增感剂和干扰抑制剂，借助双波长测定法克服光谱干扰，实现了直接测定高Ｙ混合稀土浓集物中的Ｓｍ，方法准确，快速     

甲烷与二氧化碳重整制取合成气反应的研究 (I)Sr_(1-x)La_xNiAl_(11)O_(19)催化活性表征

对具有磁铅石结构的Ｓｒ１－ｘＬａｘＮｉＡｌ１１Ｏ１９对甲烷与二氧化碳重整反应的催化活性、积炭量和稳定性进行了研究．不同还原温度下催化剂的ＸＲＤ和催化活性的实验结果表明，金属镍是ＣＨ４＋ＣＯ２重整反应的活性组分，金属镍含量越大，反应活性越高．反应后催化剂积炭量的分析结果说明，在相同镍含量和分散度的情况下，Ｌａ３＋离子对Ｓｒ２＋离子调变，可以降低催化剂的表面酸性，提高催化剂的抗积炭能力．ＬａＮｉＡｌ１１Ｏ１９是一种具有较好催化活性、稳定性和抗积炭性能的催化剂．     

Determination of A-site deficiency in lanthanum manganite by XRD intensity ratio

A method based on the X-ray diffraction intensity ratio was developed to determine the maximum deficiency that the perovskite-structured La_1−xMnO_3±δ can accommodate at the A-site. Computer simulation predicts that the intensity ratio of (024) and (012) reflections for La_1−xMnO_3±δ in hexagonal setting increases with increasing the La deficiency x. XRD analysis shows that with increasing x until 0.09, the ratio increases as predicted, then levels off with further increase in x. An abrupt change in electrical conductivity is also observed at x of ∼0.10. It is concluded that the maximum deficiency lies in between 0.09 and 0.10 for La_1−xMnO_3±δ. The methodology presented in this paper in principle can be applied to other perovskite-structured materials.     

La3Br3Ni: Jahn–Teller Distortion in the Reduced Rare Earth Metal Halide

A ternary lanthanum bromide La₃Br₃Ni was synthesized from lanthanum, LaBr₃ and nickel under argon at 800 °C. It crystallizes in the tetragonal space group I4₁22 (No. 98) with lattice constants a = 12.1758(9) Å and c = 11.744(2) Å. The structure is derived from the cubic Gd₃I₃C type of space group I4₁32 through a tetragonal distortion resulting in a squeezed nickel‐centered La₆ octahedron. Electronic structure and bonding of the compound have been investigated.     

空气-乙炔火焰原子吸收光谱法测定重整催化剂中的镁

本法研究了硝酸镧作为释放剂消除铝等元素对镁的化学干扰,探讨了空气-乙炔火焰原子吸收光谱法测定镁的最佳条件,在最灵敏吸收波长处测定催化剂中的镁含量,并进行了样品对照和加标回收试验.该法操作简便、快速、重复性好、数据可靠,结果均令人满意.