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1.
2MgO·2B_2O_3·MgCl_2·14H_2O-H_3BO_3-H_2O体系30℃相平衡 总被引:5,自引:0,他引:5
用相平衡方法研究了2MgO·2B_2O_3·MgCl_2·14H_2O-H_3BO_3-H_2O在30 ℃ 不同浓度H_3BO_3水溶液中的溶解转化产物及其溶解度。结果表明,氯柱硼镁石的 溶解转化产物,在H_3BO_3质量分数≤2.50%时为多水硼镁石;在2.50% ~ 5. 00%H_3BO_3范围时为库水硼镁石;当H_3BO_3量在5.00% ~ 5.60%之间时为章氏硼 镁石;而当H_3BO_3量≥5.60%时为三方硼镁石。提出了溶解相转化机理。 相似文献
2.
超亲水TiO2和TiO2-SiO2表面的动态润湿性 总被引:5,自引:0,他引:5
1997年, Fujishima研究组[1]发现TiO2表面经UV光照射能产生较强的亲水性, 同时具有较高的亲油性, 即经UV光照射后的TiO2表面具有超双亲的性质. 这种防雾和自清洁性在工业上应用广泛, 已引起了人们的极大兴趣[2~5]. 进一步的研究发现, 超亲水的TiO2表面在暗处放置会变为疏水表面. 对于这个问题, 除了可以通过UV光照[6]、氩离子或电子束溅射[6]和高温热处理[5]等恢复其超亲水性外, 还可以通过添加摩尔分数为10%~30%的SiO2有效地降低TiO2表面的接触角, 提高UV光诱导的超亲水表面在暗处的稳定性能[3]. 另外, 诱导TiO2的亲水性需要较强的UV线强度(如太阳光), 使它在室内应用受到限制. 为了在室内实现TiO2的自清洁功能, Watanabe等[4]发现在TiO2中添加WO3可使TiO2在室内的照明光下也能实现亲水性转变. 以上这些研究成果为TiO2在工业和生活上的实际应用提供了重要的科学依据. 然而, TiO2的防雾和自清洁功能的实现同时也受其动力学性质的制约. 相似文献
3.
Oligonucleotides containing 2'-C-alpha-methyl and 2'-C-alpha-hydroxymethyl modifications enable strategies for delineation of the distinctive role fulfilled by the 2'-hydroxyl group in RNA structure and function. Synthetic routes to the phosphoramidite derivatives of 2'-deoxy-2'-C-alpha-methylcytidine (14%, 15 steps) and 2'-deoxy-2'-C-alpha-hydroxymethylcytidine (19%, 10 steps) from methyl 3,5-di-O-(4-chlorobenzyl)-alpha-d-ribofuranoside are developed. 相似文献
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2-甲基-2-(2-硝基乙烯基)-1-苯并环酮的对映选择合成 总被引:3,自引:2,他引:1
在有些具有强烈生理活性的天然产物分子中,存在保持其特殊分子骨架的不对称季碳,是具有特定生理活性的决定性因素.利用SMP[S-(-)-2-methoxymethyl-pyrrolidine]作为手性离去基团,通过对映选择加成-消除反应构筑不对称季碳,是... 相似文献
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利用离子色谱法测定尿液中的草酸根、钙、镁离子:测定草酸根时,先在尿液中加入氯化钙使之转化成草酸钙沉淀,分离后用盐酸溶解草酸钙沉淀,然后进行测定测定钙、镁离子时,在酸性尿液中加入氧化剂过硫酸钾,在微沸状态下氧化尿液中的有机物,从而避免对色谱柱的污染:草酸根、钙、镁离子的回收率分别为108.3%~109.7%、94.9%~100.7%、97.2%~97.4%,相对标准偏差分别为2.4%、2.5%、3.1%。 相似文献
6.
NiO-SiO2,NiO-Al2O3和NiO-Al2O3-SiO2催化剂上顺酐选择加氢性能的比较 总被引:1,自引:0,他引:1
以正硅酸乙酯和硝酸铝分别为硅源和铝源,硝酸镍为活性组分前驱物,采用溶胶-凝胶法制备了NiO-SiO2,NiO-Al2O3和NiO-Al2O3-SiO2催化剂。顺酐液相选择加氢活性和选择性评价结果表明:顺酐在三种催化剂上转化率都在99%以上,而产物的选择性有较大的差别,其中NiO-SiO2催化剂上γ-丁内酯的选择性达80.1%,NiO-Al2O3催化剂上丁二酸酐选择性达99%以上,NiOAl2O3SiO2催化剂上两种产物都有。XRD,TPR等体相结构和表面结构的表征说明,三种催化剂的相组成、NiO的分散性及与载体的相互作用存在明显差别,这些差别可能是造成不同选择加氢性能的原因。 相似文献
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I. Ya. Zaitseva I. S. Kovaleva V. A. Fedorov 《Russian Journal of Inorganic Chemistry》2014,59(11):1340-1342
The interaction in the HgBr2-CdBr2-PbBr2 ternary system was studied by differential thermal analysis; the isoconcentration section of the system at 50 mol % CdBr2 was investigated. Based on the results of the study, a projection of the liquidus surface of the HgBr2-CdBr2-PbBr2 ternary system to the composition triangle was constructed; the boundaries of the primary crystallization fields were determined for three phases: HgBr2 (degenerate field), solid solution α based on CdBr2, and solid solution β based on PbBr2; and isotherms were drawn. A ternary eutectic has the composition 93 mol % HgBr2-1 mol % CdBr2-6 mol % PbBr2 and melts at 235°C. 相似文献
9.
Keith A. Monk 《Tetrahedron》2008,64(37):8605-8609
A preparation of a variety of 2-alkoxy-2-phenylpropanoic acids in two steps is described. Epoxidation of α-methylstyrene with mCPBA in methanol or primary alcohol solvents proceeded with an acid-catalyzed in situ ring opening reaction to give the corresponding 2-alkoxy-2-phenyl-1-propanols in 28-91% yield. Lower yields were realized with secondary (22-58%) and tertiary (14%) alcohols. These alcohols were cleanly oxidized to the corresponding carboxylic acids using a mild Heyns' oxidation (O2, Pt/C) in generally good to excellent yields (25-92%). The derived (S)-α-methylbenzylamide diastereomers are nearly all well separated by capillary GC, and the use of this method to determine the enantiomeric purity of brucine-resolved 2-methoxy-2-phenylpropanoic acid was demonstrated. 相似文献
10.
K. Zbudniewek J. Góralski J. Rynkowski 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(13):2057-2062
The development of industry induced a massive increase in the emission of carbon dioxide into the atmosphere. A large amount of CO2 and its general availability causes that it could be a cheap reactant in a reaction that runs in a way similar to photosynthesis in plants. Pure TiO2 and metal doped TiO2 are the most studied semiconductor catalysts for photoreduction of CO2. The TiO2/SiO2 and Pd/TiO2/SiO2 catalysts were prepared and studied by temperature-programmed desorption, X-ray diffraction analysis, SEM-EDS, temperature-programmed reduction and then used for the methanol synthesis. The photoactivity of Pd/TiO2/SiO2 catalysts in the reduction of CO2 with H2O was tested at room temperature using photoreactor equipped with 16 lamps. The wavelength was characteristic of near ultraviolet. Post-reaction products were identified with gas chromatograph equipped with the flame ionization detector. Pd doping made the catalysts photoactive and the photoactivity of catalysts was changing as follows: 1%Pd/5%TiO2/SiO2 > 1% Pd/10% TiO2/SiO2 > 1% Pd/15% TiO2/SiO2. Optimum ultraviolet radiation time in the photoreduction of CO2 to methanol was 7 h. An addition of Pd does not change the surface of the carrier. 相似文献
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TiO2−SiO2 fibres with 0, 5, 10 and 20 volume % SiO2 have been prepared by drawing from a gel followed by sintering at different temperatures. Nearly one meter long fibres can
be drawn easily in conditions of about 50% relative humidity. Addition of SiO2 inhibits the crystallisation of TiO2 and also the anatase → rutile transformation and improves the strength of the fibres. While the pure TiO2 fibres are brittle, those with 5, 10 and 20 volume % SiO2 are flexible and strong. Tensile strength values as high as 3 GPa have been achieved in the 10 volume % SiO2−TiO2 fibres. Fibres heated above 900°C are brittle. The shape of the cross section of the fibres is found to depend on their diameters. 相似文献
14.
V. V. Dotsenko S. G. Krivokolysko S. V. Shishkina O. V. Shishkin 《Russian Chemical Bulletin》2012,61(11):2082-2087
Oxidation of (E)-3-aryl-2-cyanoprop-2-enethioamides with 32% H2O2 under mild conditions gave (E)-3-aryl-2-cyano-1-iminioprop-2-ene-1-sulfenates in 70–88% yields. Under the conditions of the Radziszewski reaction (H2O2, 10% aqueous KOH) or upon prolonged treatment with H2O2, (E)-3-aryl-2-cyanoprop-2-enethioamides underwent transformations leading to complex mixtures of oxidation products. In some cases, 3-aryloxirane-2,2-dicarboxamides were isolated from those mixtures in low yields (<20%). Treatment of 3-arylamino-2-cyanoprop-2-enethioamides with the system H2O2/KOH in ethanol afforded (arylaminomethylidene)malononitriles. 相似文献
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B. A. Trofimov L. N. Sobenina Z. V. Stepanova A. P. Demenev A. I. Mikhaleva I. A. Ushakov T. I. Vakul’skaya O. V. Petrova 《Russian Journal of Organic Chemistry》2006,42(9):1348-1355
Cross coupling of 2-arylpyrrole with benzoylbromoacetylene over aluminum oxide at room temperature gave 45–94% of 2-(benzoylethynyl)-5-arylpyrroles. Intermediate 2-(2-benzoyl-1-bromoethenyl)-5-arylpyrroles were isolated in up to 19% yield. The reaction was accompanied by formation of less than 5% of adducts of the initial pyrroles with the cross-coupling products, 2-benzoyl-1,1-bis(5-arylpyrrol-2-yl)ethenes. 相似文献
16.
N. B. Babanly I. I. Aliev G. A. Azizov M. B. Babanly 《Russian Journal of Inorganic Chemistry》2006,51(4):642-644
Phase equilibria in the Ag-Tl-Bi-Se system in the region Ag2Se-AgTlSe-TlBiSe2 (I) have been investigated by DTA, X-ray powder diffraction analysis, microstructural analysis, and microhardness measurements. The Ag2Se-TlBiSe2, AgTlSe-AgBiSe2 (0–50 mol % AgBiSe2), and Ag3TlSe2-TlBiSe2 polythermal sections and the projection of the liquidus surface have been constructed. It has been found that system I is quasi-ternary; it consists of the primary crystallization fields of the phases based on the Ag2Se, TlBiSe2, AgTlSe, Ag3TlSe2, and Ag7TlSe4 compounds. The system is characterized by peritectic and eutectic four-phase equilibria. The coordinates of the invariant points are the following: 690 K, 50 mol % Ag2Se, 7 mol % TlBiSe2 (P 3); 658 K, 39 mol % Ag2Se, 4 mol TlBiSe2 (P 4); and 650 K, 32 mol % Ag2Se, 3.5 mol % TlBiSe2 (E). 相似文献
17.
Ni/AlO催化-甲基呋喃加氢制-甲基四氢呋喃性能的研究 《燃料化学学报》2018,46(1):54-58
采用浸渍法制备了不同NiO含量的Ni/Al2O3催化剂,并进行了2-甲基呋喃加氢制2-甲基四氢呋喃性能的考察。结果表明,在制备的NiO负载量为10%、20%、25%、30%和40%的Ni/Al2O3催化剂中,随着NiO负载量增加,加氢反应的选择性与2-甲基呋喃的转化率均呈现出先增加后减小的趋势。其原因是由于适当增加NiO负载量有利于催化剂表面活性中心的形成,有利于加氢反应的进行;但是过度负载的NiO容易堵塞Al2O3载体中的介孔通道,降低反应的转化率与选择性。在釜式反应器中进行反应,对加氢反应条件进行了优化,发现在反应压力为3 MPa、反应温度150℃、机械搅拌速率为1000 r/min时,Ni/Al2O3催化2-甲基呋喃加氢制2-甲基四氢呋喃具有较高的选择性。当NiO负载量为25%时,2-甲基四氢呋喃的选择性最高为97.1%,2-甲基呋喃的转化率达到99.4%。 相似文献
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Journal of Thermal Analysis and Calorimetry - In O2/N2 and O2/CO2 atmospheres with oxygen concentrations of 21%, 30%, and 50%, combustion characteristics index, apparent activation energy, and... 相似文献
19.
TiO2–ZrO2的表征及其异丙醇催化转化性能 总被引:1,自引:0,他引:1
用共沉淀法制备了TiO2-ZrO2复合氧化物. 采用N2吸附、XRD、TEM、NH3和CO2吸附量热、NH3吸附红外对TiO2-ZrO2体系的结构及酸碱性等进行了表征. 结果表明: 与单纯的氧化物相比, 形成的复合氧化物为无定形物相, 有介孔结构, 表面积明显提高, 可达218 m2·g-1; 初始吸附热差别不大, 但具有更多的表面B酸位; 随着TiO2掺入量的增大, 复合氧化物表面碱位减少. 异丙醇催化转化, 在无氧条件下, ZrO2、TiO2和TiO2-ZrO2复合氧化物上丙烯的选择性大于90%, 说明这些氧化物具有强的表面酸性; 在有氧条件下, ZrO2和TiO2丙酮的选择性达到70%~85%, 主要体现为氧化还原性; 而在复合氧化物上丙烯选择性增大到70%左右, 丙酮的选择性下降为30%左右, 表明生成的复合氧化物表面上的氧化还原性削弱, 酸性增强. 相似文献
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Phosphoryl chloride reacts with 2-picoline-N-oxide in the presence of triethylamine to give 2-chloromethylpyridine in 90% conversion with 98% selectivity. Diethylchlorophosphate, ethyl chloroformate, chloroacetyl chloride and phosgene also react with 2-picoline-N-oxide to give 2-chloromethylpyridine in moderate yields. Other potential chlorinating agents, titanium tetrachloride, zinc chloride, magnesium chloride and sulfuryl chloride, did not convert 2-picoline N-oxide into 2-chloromethylpyridine. 相似文献