共查询到20条相似文献,搜索用时 11 毫秒
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The self-diffusion coefficient D for super- and subcritical water is determined by using the proton pulsed-field-gradient spin echo method at high temperatures and low densities. The density of water is ranged in the steamlike region from 0.0041 to 0.0564 g [corrected] cm(-3) at a supercritical temperature of 400 degrees C, also at 0.0041-0.0079 and 0.0041-0.0462 g [corrected] cm(-3) (the steam-branch densities on the coexistence curve and lower) at 200 and 300 degrees C, respectively. The density is precisely determined on the basis of the PVT dependence of the proton chemical shift. The density-diffusivity products in the zero-density limit divided by the square root of the temperature, (rho D)0/square root of T, are 0.94, 1.17, and 1.35 mg m(-1) s(-1) K(-1/2) (mg=10(-3)g) [corrected] at 200, 300, and 400 degrees C, respectively. The (rhoD)0/square root of T obtained decreases with decreasing temperature and is significantly smaller than the temperature-independent value from the hard sphere model, 1.95 mg [corrected] m(-1) s(-1) K(-1/2). The marked temperature dependence reflects the presence of the strong attractive interaction between a pair of water molecules. The magnitude of the experimental D values and the temperature dependence are well reproduced by the molecular dynamics simulation using TIP4P-FQ model. The initial slope of the product rhoD/square root of T against rho is slightly negative at 300 and 400 [corrected] degrees C. 相似文献
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M. Doverstål B. Lindgren U. Sassenberg H. Yu 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,19(4):447-449
The hydrogen uptake for small carbon clusters C4 to C22 has been studied at high hydrogen pressure. This study indicate that both chain and ring structures exist in parallel. 相似文献
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Summary In supercritical fluid chromatography, the sample load that can be injected using the sample solvent evaporation technique is limited by the volume of the loading precolumn. A multiple sample loading procedure is investigated in order to increase the injectable amount and to optimize injection conditions. This work also deals with optimization of solvent removal conditions. 相似文献
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The mass distribution of charged particles from the plasma plume produced by laser ablation of pyrolytic graphite was studied
by an electrostatic probe technique. The velocities of motion of the charged opposite parts of the plume double-electric layer
and the potential of its internal self-consistent field were determined. Using a proposed procedure for the treatment of probe
signals, the amounts of detectable positive and negative ions were evaluated. The negatively charged large carbon particles
with a size of up to 106 atoms were assumed to directly appear from explosive bulk effervescence and spinodal separation of the overheated carbon
phase on the graphite surface. 相似文献
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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
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In the present work,effect of theattr action terms of four recently modified Peng-Robinson(MPR)equations of state on the prediction of solubility of caffeine,cholesterol,uracil and erythromycin was studied.The attraction terms of two of these equations are linear relative to the acentric factor and for the other two are exponential.It is found that the later show less deviation.Also interaction parameters for the studied systems are obtained and the percentage of average absolute relative deviation(%AARD)in each calculation is displayed. 相似文献
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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
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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
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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
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Experimental data on the treatment of detonation carbon in supercritical water are given. 相似文献
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V. V. Aksenova R. M. Nikonova V. I. Lad’yanov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(8):1465-1471
A mixture of stable derivatives of fullerenes containing ether/diketone functional groups, some of which are water-soluble,
were obtained during the destruction of fullerenes upon annealing in air. The results were confirmed by IR and UV spectroscopy. 相似文献
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Hiroo Hasebe Hironori Kuboki Hiroki Okuno Isao Yamane Hiroshi Imao Nobuhisa Fukunishi Masayuki Kase Osamu Kamigaito 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1013-1018
New carbon-nanotube–sputter-deposition-carbon (CNT–SDC) foils were developed and used in the U beam time at the RIKEN RI Beam Factory (RIBF) from October to December 2011. The lifetimes of these new foils were drastically extended, and stable, high-intensity U beams were successfully provided to users. The lifetime of the CNT–SDC foils was 2–5 C, which was 100 times longer than those of static C-foils previously used. The qualitative analysis of the CNT–SDC foils clearly showed that the CNT structure and bundles were broken by beam irradiation. In addition, it was found that CNT bundles in the CNT–SDC foil were grown after the carbon deposition procedure. This structure was considered to be the reason that the CNT–SDC foils maintain advantages of both CNT and SDC foils. 相似文献
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Preparation of liposomes using an improved supercritical reverse phase evaporation method 总被引:2,自引:0,他引:2
Otake K Shimomura T Goto T Imura T Furuya T Yoda S Takebayashi Y Sakai H Abe M 《Langmuir : the ACS journal of surfaces and colloids》2006,22(6):2543-2550
Liposomes of various phospholipids were prepared using an improved supercritical reverse phase evaporation (ISCRPE) method that utilizes supercritical carbon dioxide (scCO(2)) as an alternative to organic solvents. Using this method, in the absence of any organic solvent including ethanol, the maximum trapping efficiency of glucose reached 36% for 20 mM l-alpha-dioleoylphosphatidylcholine (DOPC), compared to less than 10% using the Bangham method. Liposomes prepared by the ISCRPE method were highly stable for one month at room temperature. Freeze fractured TEM observations, osmotic shrinkage measurements, and DSC measurements revealed that the liposomes prepared by the ISCRPE method are unilamellar vesicles with loosely packed phospholipids. Comparison of nitrogen with scCO(2) revealed that the presence of CO(2) is necessary for the formation of liposomes. 相似文献
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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