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61.
62.
CaO和NaCl焙烧混合稀土精矿过程中的分解反应 总被引:5,自引:0,他引:5
用XRD和TG-DTA热分析技术, 研究了含独居石和氟碳铈镧矿的混合稀土精矿在100~1000 ℃焙烧过程中, 添加CaO, NaCl时, REPO4和REFCO3的分解反应. 研究结果表明: 不添加CaO和NaCl时, 仅在377~450 ℃范围内存在REFCO3的分解反应, 其产物是REOF, RE2O3, 以及Ce2O3进一步的氧化产物CeO2, 而REPO4不分解; 添加CaO后在660~750 ℃之间, CaO有3种分解作用: (1) CaO分解REPO4, 其产物是RE2O3和Ca3(PO4)2. (2) CaO分解REOF, 其产物是RE2O3和CaF2. (3) CaO和REOF的分解产物CaF2共同作用分解REPO4, 其分解产物为RE2O3, Ca5F(PO4)3; 添加CaO, NaCl后, 混合精矿的分解率明显提高, NaCl的作用是为反应体系提供了液相, 促进了固相反应物间的传质过程, 加快了反应速度. 与此同时NaCl还可能参加了CaO分解REPO4的反应. 相似文献
63.
Mosstafa Kazemi 《合成通讯》2020,50(13):1899-1935
AbstractCatalysis research under magnetically recoverable nanocatalysts is a well-known topic in organic synthesis. In recent times, catalysis research has clearly experienced a renaissance in the area of utility of ferrite nanoparticles based on their ability to recovery and reusability. In this review, the focus is on the fabrication, characterization and of application the MFe2O4 (M=Co, Cu, and Ni) nanocatalysts in synthesis of heterocyclic structural scaffolds. 相似文献
64.
Ichikawa K Shimomura N Yamada M Ohkubo N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3235-3241
In vitro biomimetic mineralization by means of nanotechnology allows the formation of calcium carbonate polymorphs at low temperatures (<25 degrees C) under a CO(2) atmosphere of 500-1500 ppm. A two-dimensional zinc-ion ordered array (zinc array), which acts as an active-site mimic of carbonic anhydrase, has been prepared by immersing the self-organized monolayer of 3-(2-imidazolin-1-y)propyltriethosilane on mica (ImSi substrate) into aqueous zinc solution. The zinc array mounted on the ImSi substrate catalyzed the conversion from CO(2) to HCO(3) (-), and accelerated the formation of calcium carbonate. In situ X-ray diffraction data of the formed calcium carbonate on the poly(L-aspartate)-coated chitin substrate (pAsp substrate), with calcium ion-recognition sites, demonstrated that the interaction between the zinc array and pAsp substrates formed both vaterite and calcite at low temperature (15 degrees C) and mainly vaterite at 25 degrees C; this interaction also controlled the morphology of calcium carbonate formed on pAsp substrate. 相似文献
65.
Preparation,stability and two-dimensional ordered arrangement of gold nanoparticles capped by surfactants with different chain lengths 总被引:2,自引:0,他引:2
Gold nanoparticles modified with C10NH2, C12NH2, C16NH2 and C18NH2 respectively have been prepared by the reverse micelle method. Nanoparticles stability and their two-dimensional (2D) ordered arrangement were studied by UV-Vis absorption spectra and LB technique. The factors, such as the chain length and the size distribution of particles, which affect the 2D ordered arrangement formation, are discussed. Experimental results show that the longer the chain length of surfactants capping the gold nanoparticles, the more stable the nanoparticles, and the more ordered 2D arrangement of gold nanoparticles. 相似文献
66.
RING-OPENING POLYMERIZATION OF TRIMETHYLENE CARBONATE CATALYZED BY NOVEL SINGLE COMPONENT RARE EARTH CALIXARENE COMPLEXES 总被引:2,自引:0,他引:2
Wei-puZhu JunLing HongXu Zhi-quanShen 《高分子科学》2005,(4):407-410
In this paper, ring-opening polymerization of trimethylene carbonate (TMC) with rare earth (Nd, Y, La) p-tert-butylcalix[n]arene (n=4, 6, and 8) complexes as catalysts has been studied. Poly(trimethylene carbonate) (PTMC) with Mv of 21,400 was produced by bulk polymerization under the conditions as follows: [TMC]0/[Nd] (molar ratio)=1000,80℃,8h. Mechanism study reveals that the polymerization proceeds via a coordination mechanism. 相似文献
67.
The chemical fixation of CO2 with mono-substituted terminal epoxides or cyclohexene oxide to form cyclic carbonates under the ZnCl2/[BMIm]Br catalyst system without using additional organic solvents was achieved in excellent selectivity (>98%) and TOF (5410 h−1) and the catalyst could be used six times almost without losing its catalytic activity and selectivity. Besides, the pure cis-cyclic carbonate of cyclohexene oxide was obtained in this catalyst system. 相似文献
68.
在纳米尺度下构建有序的磁性模板和图形是当前的研究热点之一 [1,2 ] .这种模板在生物样品的分离[1] 、磁电子学研究和信息存储 [2 ] 等领域具有重要意义 .目前 ,光刻 [3] 、微触点印刷 [4 ] 和自组装 [5] 等多项技术已被用来构建各种纳米模板 .1 999年 ,美国西北大学 Mirkin小组 [6 ]发明的 Dip- pen纳米刻蚀技术 (简称 DPN技术 )更在可控组装方面显示出巨大优越性 .这项技术是在一定驱动力作用下 ,使吸附在原子力显微镜 ( AFM)针尖上的分子“墨水”逐渐转移到基底表面上 ,实现纳米模板的可控构建 .与传统技术相比 ,DPN技术可在纳米尺… 相似文献
69.
F. M. Bautista J. M. Campelo A. Garcia D. Luna J. M. Marinas A. A. Romero M. R. Urbano 《Reaction Kinetics and Catalysis Letters》1997,62(1):47-54
The vapor-phase catalytic alkylation of phenol with methanol and dimethyl carbonate on a series of differently prepared CrPO4 (Cr/P=1) and CrPO4-AlPO4 (CrAIP) catalysts, has been studied at different temperatures (473–673 K). The reaction is first order in phenol, giving
a mixture of O- and C-alkylated products (C-alkylation taking place preferentially at theortho-position). Moreover, dimethyl carbonate is a better methylating agent than methanol. 相似文献
70.
Silica nanoparticles for separation of biologically active amines by capillary electrophoresis with laser-induced native fluorescence detection 总被引:1,自引:0,他引:1
This paper describes the analysis of biologically active amines by capillary electrophoresis (CE) in conjunction with laser-induced native fluorescence detection. In order to simultaneously analyze amines and acids as well as to achieve high sensitivity, 10 mM formic acid solutions (pH < 4.0) containing silica nanoparticles (SiNPs) were chosen as the background electrolytes. With increasing SiNP concentration, the migration times for seven analytes decrease as a result of increase in electroosmotic flow (EOF) and decrease in their electrophoretic mobilities against EOF. A small EOF generated at pH 3.0 reveals adsorption of SiNPs on the deactivated capillary wall. The decreases in electrophoretic mobilities with increasing SiNP concentration up to 0.3x indicate the interactions between the analytes and the SiNPs. Having a great sensitivity (the limits of detection at a signal-to-noise ratio (S/N) = 3 of 0.09 nM for tryptamine (TA)), high efficiency, and excellent reproducibility (less than 2.4% of the migration times), this developed method has been applied to the analysis of urinal samples with the concentrations of 0.50 +/- 0.02 microM, 0.49 +/- 0.04 microM, and 74 +/- 2 microM for TA, 5-hydroxytryptamine, and tryptophan, respectively. The successful examples demonstrated in this study open up a possibility of using functional nanoparticles for the separation of different analytes by CE. 相似文献