共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
《Electrophoresis》2017,38(13-14):1678-1684
Stable organosols of TiO2 nanoparticles were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in microemulsions of sodium bis(2‐ethylhexyl)sulfoxynate (АОТ) in n‐decane with increasing the content of aqueous pseudophase from 0.15 to 0.85 vol.%. As the water content increased, the hydrodynamic diameter of nanoparticles grew from 10 to 225 nm, and the ζ‐potential, from ‐6 to 18 mV (the surface of TiO2 nanoparticles was recharged when the water content was 0.45 vol.%). Nonaqueous electrophoresis in a capacitor‐type cell made it possible to concentrate nanoparticles with a diameter of 60 to 225 nm (concentration factor was 10), separate 20 nm and 225 nm particles, and decrease the content of АОТ in organosol by an order of magnitude. Preparation of a concentrate of nanoparticles with a low content (0.015 M) of AOT included the following stages: (i) electrophoresis after synthesis; (ii) sampling of the concentrate and its twenty‐fold dilution with pure n‐decane; and (iii) repeated electrophoresis. In situ laser and spectrophotometric scanning of the interelectrode space showed the formation of a sharp boundary between the raffinate and the layer of moving nanoparticles during electrophoresis. 相似文献
3.
Samsonov MD Wai CM Lee SC Kulyako Y Smart NG 《Chemical communications (Cambridge, England)》2001,(18):1868-1869
Uranium dioxide can be dissolved in supercritical CO2 with a CO2-philic TBP-HNO3 complexant to form a highly soluble UO2(NO3)(2).2TBP complex; this new method of dissolving UO2 that requires no water or organic solvent may have important applications for reprocessing of spent nuclear fuels and for treatment of nuclear wastes. 相似文献
4.
V. N. Khrustalev L. N. Nikitin A. Yu. Vasil’kov A. R. Khokhlov 《Russian Chemical Bulletin》2006,55(3):576-578
An organometallic compound, monoacetylferrocene, was for the first time obtained as single crystals by crystallization from
supercritical carbon dioxide. This offers the possibility of utilizing supercritical media for efficient crystallization and
purification of organometallic compounds without using organic solvents.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 555–557, March, 2006. 相似文献
5.
Fürstner A Ackermann L Beck K Hori H Koch D Langemann K Liebl M Six C Leitner W 《Journal of the American Chemical Society》2001,123(37):9000-9006
Liquid or supercritical carbon dioxide (scCO(2)) is a versatile reaction medium for ring-opening metathesis polymerization (ROMP) and ring-closing olefin metathesis (RCM) reactions using well-defined metal catalysts. The molybdenum alkylidene complex 1 and ruthenium carbenes 2 and 3 bearing PCy(3) or N-heterocyclic carbene ligands, respectively, can be used and are found to exhibit efficiency similar to that in chlorinated organic solvents. While compound 1 is readily soluble in scCO(2), complexes 2 and 3 behave like heterogeneous catalysts in this reaction medium. Importantly, however, the unique properties of scCO(2) provide significant advantages beyond simple solvent replacement. This pertains to highly convenient workup procedures both for polymeric and low molecular weight products, to catalyst immobilization, to reaction tuning by density control (RCM versus acyclic diene metathesis polymerization), and to applications of scCO(2) as a protective medium for basic amine functions. The latter phenomenon is explained by the reversible formation of the corresponding carbamic acid as evidenced by (1)H NMR data obtained in compressed CO(2). Together with its environmentally and toxicologically benign character, these unique physicochemical features sum up to a very attractive solvent profile of carbon dioxide for sustainable synthesis and production. 相似文献
6.
超临界二氧化碳介质中有机化学反应研究 总被引:3,自引:0,他引:3
综述了本研究小组近年来在超临界二氧化碳介质中过渡金属催化的有机化学反应的研究结果,主要包括烯烃和炔烃的羰基化反应、氧化反应、自由基反应、低聚反应。 相似文献
7.
Since flow injection (FI) is a dilution technique, efforts have been undertaken to minimize online dilution or dispersion. Solutes in supercritical fluids exhibit increased diffusion coefficients which have been shown to decrease dispersion of the sample zone. This work investigates the use of supercritical fluids (or CO2 modified fluids) as carrier streams for FI. Both a non-reacting tracer and an online chemical reaction were employed to investigate the behavior of solutes in supercritical and near critical systems. Further, these results are compared to those obtained in the system studied with a conventional carrier stream. Plots of peak response vs% CO2 modifier increase with a sharp break at moderate modifier composition (20–30%). Plots of peak variance vs% CO2 modifier show decreased variance with increasing % modifier. The system was also optimized with regards to temperature and pressure. The optimized system displayed improved limits of detection and decreased variance relative to 0% CO2 modifier carrier streams. 相似文献
8.
9.
Wang J Khlobystov AN Wang W Howdle SM Poliakoff M 《Chemical communications (Cambridge, England)》2006,(15):1670-1672
A facile and efficient method has been developed for coating MWNTs with solvent resistant polymer in scCO2, which permits the selective deposition of high molecular weight fluorinated graft poly(methyl vinyl ether-alt-maleic anhydride) polymer onto MWNTs in scCO2 under 100-170 bar at 40 degrees C and forms quasi one-dimensional nanostructures with conducting cores and insulating surfaces. 相似文献
10.
11.
Lee CK Holmes AB Al-Duri B Leeke GA Santos RC Seville JP 《Chemical communications (Cambridge, England)》2004,(22):2622-2623
The regioselectivity of dipolar cycloadditions of mesitonitrile oxide to various dipolarophiles in supercritical carbon dioxide can be tuned by changes in density, the magnesium bromide-mediated cycloaddition to pent-1-en-3-ol proceeding with higher stereoselectivity than in most conventional solvents. 相似文献
12.
Early TR Gordon RS Carroll MA Holmes AB Shute RE McConvey IF 《Chemical communications (Cambridge, England)》2001,(19):1966-1967
Heck and Suzuki reactions proceed in good yield in supercritical carbon dioxide in the presence of palladium acetate and tri-tert-butylphosphine with both free and polymer-tethered substrates. 相似文献
13.
14.
Liquid phase hydrogenation of phenol over Pt/C catalysts was investigated under conventional conditions and supercritical carbon dioxide (scCO2). The equivalent ration of hydrogen to phenol shows a significant effect on the product selectivity. Hydrogenation of phenol in different solvents was also studied, the experimental results show that polarity of solvents influences the yield of cyclohexanone remarkably, scCO2 has the highest one. Catalytic hydrogenation of phenol in scCO2 or sub-scCO2 was emphatically researched. The result is that near the critical point of CO2 phenol has higher reaction activity than that of normal organic solvents, cyclohexanone has 47% in yield and 87% in selectivity. 相似文献
15.
16.
Supercritical carbon dioxide has been considered an appropriate alternative for extraction and purification process of cosmetics, pharmaceuticals, food supplements and natural products. Solubility information of biological compounds is essential for choosing supercritical fluid (SCF) processes. The solubility of iodopropynyl butylcarbamate (IPBC), a fungicide and anti-dandruff agent, was measured in supercritical carbon dioxide with a high pressure apparatus equipped with a variable volume view cell at 313.15, 323.15, and 333.15 K and at pressure between 80 and 35 MPa. The experimental data were correlated well with Peng–Robinson equation of state (PR EOS) and quasi-chemical nonrandom lattice fluid model. 相似文献
17.
《Fluid Phase Equilibria》1998,152(2):299-305
The equilibrium solubilities of dihydroxybenzene isomers pyrocatechol, resorcinol and hydroquinone have been measured in supercritical carbon dioxide using a simple static method. The measurements were performed in the pressure range from 120 to 400 atm at temperatures 35, 45, 55 and 65°C for pyrocatechol and resorcinol and in the pressure range from 120 to 200 atm at temperature 35°C for hydroquinone. The solubility of the isomers in supercritical CO2 was found to vary in the order pyrocatechol>resorcinol≫hydroquinone. The experimental data were correlated by use of the density based model proposed by Chrastil. 相似文献
18.
The dielectric properties of the system water/AOT/dodecane are studied as a function of volume fraction of the dispersed phase and molar ration (water/surfactant). Data shows that the spherical model is valid only at lown values or low values. At high concentrations of dispersed phase, one has to consider micellar aggregation or deformation. 相似文献
19.
20.
The reactions of methylenecyclopropanes (MCPs) and epoxides with alcohols and aromatic amines can be carried out in supercritical carbon dioxide (scCO2) or modified scCO2 with perfluorocarbon which offer a way to synthesize various alcohols, amino-alcohols, homoallylic ethers, and amines under an environmentally benign condition. 相似文献