首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Modification of an experimental device and methodology improved speed and reproducibility of measurement of solubility of β-carotene in pure and modified SuperCritical (SC) CO2 at (313 to 333) K. Solubilities of β-carotene in pure CO2 at (17 to 34) MPa ranged (0.17 to 1.06) μmol/mol and agreed with values reported in literature. The solubility of β-carotene in CO2 modified with (1.2 to 1.6) % mol ethanol increased by a factor of 1.7 to 3.0 as compared to its solubility in pure CO2 under equivalent conditions. The concentration of triolein in equilibrated ternary (CO2 + β-carotene + triolein) mixtures having excess triolein reached values (0.01 to 0.39) mmol/mol corresponding to its solubility in pure SC CO2 under equivalent conditions. Under these conditions, the solubility of β-carotene in triolein-modified CO2 increased by a factor of up to 4.0 in relation with its solubility in pure CO2 at comparable system temperature and pressure, reaching an uppermost value of 3.3 μmol/mol at 333 K and 32 MPa. Unlike in the case of ethanol, where enhancements in solubility where relatively independent on system conditions, solubility enhancements using triolein as co-solvent increased markedly with system pressure, being larger than using (1.2 to 1.6) % mol ethanol at about (24 to 28) MPa, depending on system temperature. The increase in the solubility β-carotene in SC CO2 as a result of using ethanol or triolein as co-solvent apparently does not depend on the increase in density associated with the dissolution of the co-solvent in CO2. Enhancements may be due to an increase in the polarizability of SC CO2, which possibly growths markedly as triolein dissolves in it when the system pressure becomes higher.  相似文献   

2.
Econazole (C18H15Cl3N2O) is one of the common antifungal agents whose poor aqueous solubility restricts its use for the treatment of oropharyngeal candidiasis, which is the first symptom of HIV infection. Therefore, the aim of the current study was to investigate the effect of different preparation methods (i.e. kneading, coevaporation, sealed-heating, and supercritical carbon dioxide (SC CO2)) for obtaining solid inclusion complexes between β-cyclodextrin and econazole. The physico-chemical properties of the different products were characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffractometry (PXRD). For the complexes prepared by the SC CO2 method, the effects of temperature and pressure have also been investigated and related to the solubility of econazole in SC CO2. Results suggested the validity of the SC CO2 method for preparing solid complexes between cyclodextrins and econazole, avoiding the use of organic solvents and problems of their complete removal. Moreover, temperature played a major role in promoting drug-carrier interactions, whereas pressure had limited effects.  相似文献   

3.
The effect of supercritical (SC) CO2 on the bulk hydrogenation of NBR entrapped with the catalyst (RhCl(PPh3)3) was investigated under various reaction times, reaction temperatures, hydrogen pressures and loadings of the catalyst and the thicknesses of the polymer films. CO2 helps in improving the transport behaviour of catalyst in polymer matrices, as well as helping to move catalyst into or out of the polymer. A method for the measurement of the dissolution extent or the apparent solubility of the Rh based catalyst in SC-CO2 was developed. It is found that high temperatures and high SC-CO2 densities would enhance the apparent solubility. Cosolvents, such as acetone, are also found to increase the apparent solubility. Details on the hydrogenation process are also presented.  相似文献   

4.
Supercritical carbon dioxide (SC CO2)-assisted chemical and material processing has shown great success in the fabrication of 2D amorphous materials, while the amorphization mechanism in SC CO2 is quite complicated to be understand. In this review, we introduce different kinds of 2D amorphous materials prepared with SC CO2 and discuss the possible amorphization mechanism and how they affect the structures and properties of 2D materials. Their applications are further presented and discussed. In addition, the prospective of future development of SC CO2-assisted fabrication of 2D amorphous materials is also involved. The investigation of SC CO2 induced amorphization not only provides theoretic understanding of amorphization process, but also directs to the preparation and application of 2D amorphous materials with specific structure and property, suggesting the promising future of SC CO2-assisted process in material design and engineering.  相似文献   

5.
Polymers containing CO2‐philic groups are of great interest for CO2/light gas separation membranes because the affinity toward CO2 can effectively increase CO2 solubility and thus permeability. In this study, polysulfones (PSUs) modified with different degrees of benzyldimethylamine (DMA), benzyltrimethylammonium fluoride (TMAF), and benzyltrimethylammonium iodide (TMAI) were synthesized using sequential post‐functionalization reactions and investigated for CO2/N2 and CO2/CH4 separation. The physical properties of these polymers were studied, including density, fractional free volume, and glass transition temperature. In contrast to the conventional wisdom that tertiary amines exhibit an affinity toward CO2, this study convincingly shows that the DMA substituent has a minimal impact on CO2 solubility and CO2/light gas solubility selectivity in PSUs under dry condition. On the other hand, incorporating TMAF and TMAI in PSU significantly increases CO2 solubility. Particularly, introducing TMAI with a molar ratio of 1.07 relative to PSU repeating units increases CO2/CH4 solubility from 4.4 to 5.2, CO2/CH4 permeability selectivity from 21 to 45, and CO2/N2 permeability selectivity from 24 to 33 at 35 °C, while the CO2 permeability decreases from 5.6 to 1.7 Barrers. The effect of these functional groups in PSUs on gas diffusivity and diffusivity selectivity can be satisfactorily described by the free volume model. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1239–1250  相似文献   

6.
《Fluid Phase Equilibria》1999,164(1):107-115
The equilibrium solubilities of l-carvone and l-limonene in the binary (l-carvone–CO2 and l-limonene–CO2) and ternary (l-carvone–l-limonene–CO2) systems were obtained at 39°C and 49°C and at pressures ranging from 6 to 10 MPa. The solubilities of these components increased with a pressure increase or a temperature decrease. The solubility of l-limonene was higher than that of l-carvone at the same temperature and pressure. The correlation of the solubilities using Chrastil equation revealed that the solubilities of both components were strongly dependent on the density of CO2. In the ternary system simulating the actual spearmint oil composition, the solubility of l-carvone was similar but the solubility of l-limonene was lower as compared to their solubilities in the binary systems.  相似文献   

7.
The density and viscosity of liquid sulfolane saturated (loaded) with single CO2 and H2S gases were measured simultaneously with the solubility of the single CO2 and H2S gases in sulfolane at temperatures ranging from (303.15 to 363.15) K and pressures of up to about 2.4 MPa using a new experimental set-up developed in our laboratory. The experimental density and viscosity values were correlated using a modified Setchenow-type equation. It was observed that the density and viscosity of mixtures decrease by increasing temperature and acid gas solubility (loading) in sulfolane. Acid gas loading has a much profounder effect on the viscosity of solutions than on their density, i.e. at a concentration of 1 mol CO2/H2S per kg of sulfolane the density decreases by less than 3%, but viscosity decreases by more than 30%. Results show that at fixed temperature and pressure H2S is more than four times as soluble as CO2 in sulfolane. The measured solubility and density values were respectively used to obtain Henry’s law constants and partial molar volumes at infinite dilution for dissolution of CO2 and H2S gases in the liquid sulfolane at the temperatures studied. The Henry’s law constants obtained at different temperatures were used to determine infinite dilution partial molar thermodynamic functions (Gibbs free energy, enthalpy and entropy) of solution. The measured solubility data were correlated by using a model comprised of the extended Henry’s law and the Pitzer’s virial expansion for the excess Gibbs free energy.  相似文献   

8.
Interactions of penetrants with gas separation membrane materials can have both desirable and undesirable consequences. Improved permselectivity resulting from specific polymer/penetrant interactions must be balanced against potentially undesirable plasticization effects resulting from such interactions. Consideration is given to the utility of gas solubility measurements in low-molecular-weight solvents as an aid to understanding solubility data for polymer/gas systems. The solubility coefficients of gases in low-molecular-weight liquids and in polymeric media of similar chemical structure tend to be quite different in magnitude. “Equation-of-state” and combinatorial entropy differences for the free energy of mixing of gases with low-molecular-weight solvents and high-molecular-weight polymers presumably cause this discrepancy. The above complications are minimized and useful trends identified by considering the so-called solubility selectivity comprised of ratios of absolute gas solubilities in both low-and high-molecular-weight media of similar chemical natures. For example, both acetone and methyl acetate are highly sorptive of CO2 and display a high degree of solubility selectivity for CO2 relative to CH4. These two solvents have mass densities of carbonyl groups that are similar to that in cellulose acetate and poly(methyl methacrylate). Both of these polymers are also highly sorptive of CO2 and have solubility selectivities for CO2 relative to CH4 that are similar to that of acetone and methyl acetate. Anomalous behavior is encountered in the case of Kapton poly(ether diimide), which contains a high density of carbonyl groups (four per repeat unit). On the basis of the behavior of the other carbonyl-rich polymers, it was expected that Kapton would show high solubility selectivity for CO2 relative to CH4, but this was not observed. A hypothetical explanation for the Kapton behavior is presented. In addition, possible advantages of the Kapton-type behavior are discussed in the context of the reported good plasticization resistance of polyimides.  相似文献   

9.
Independent solubility and permeability data, measured at 35°C at up to 26 atm, are reported to show the influence of aryl-bromination on the transport of CO2, CH4, and N2 in 2,6-dimethyl-1,4-poly(phenylene oxide) (PPO). The permeability of PPO was found to vary with the extent of bromination, and the magnitude of change depends on the nature of the gas. The apparent solubility coefficients of all three gases at 20 atm in the polymer increased with the extent of bromination, and the percentage of increase was higher for the gas with lower condensability. The concentration-averaged diffusivities of CO2 and CH4 also showed some variation with the extent of bromination. In particular, there was a notable increase in the diffusivity of CO2 but a slight decrease in that of CH4 when the extent of bromination was increased to 91%. The gas-transport data were also analyzed according to the dual-mode model. The dual-mode parameters exhibit similar dependence on the extent of bromination as the apparent solubility coefficient and concentration-averaged diffusivity do. These observations are interpreted in terms of changes in the average packing, torsional mobility of the chain segments, and cohesive energy density of the polymer.  相似文献   

10.
The objective of this study was to investigate the effectiveness of supercritical carbon dioxide (SC CO2) technique for preparing solid complexes between β-cyclodextrin and three local anesthetic agents (benzocaine, bupivacaine, and mepivacaine) by comparing it to more traditional methods such as kneading, co-evaporation, co-grinding, and sealed-heating. Effects of variation of experimental conditions, i.e. temperature, pressure and exposure time, on the products prepared by SC CO2 method were also examined. The products obtained were characterized by powder X-ray diffractometry and Fourier transform infrared spectroscopy, and tested for dissolution properties. Results suggested the possibility of complex formation between β-cyclodextrin and the three anesthetic agents, and indicated that it was influenced by the preparation technique. The co-grinding method was the only one resulting in completely amorphous products for all three drugs. Almost amorphous products, with only limited residual crystallinity, were obtained by co-evaporation and kneading techniques, while SC CO2 and sealed-heating methods gave rise to more crystalline systems. As for the SC CO2 method, temperature (for benzocaine and bupivacaine) or exposure time (for mepivacaine) had significant effects on the solid-state properties of the final products. Dissolution studies indicated that all the examined methods were more effective than the simple physical mixing in improving drug dissolution properties, but the different rank orders observed for the different drugs suggested that there is no general rule for the selection of the most effective preparation method, which depends on the type of drug-Cyd system considered. Nevertheless, in all cases, products obtained by the SC CO2 method showed satisfactory dissolution properties.  相似文献   

11.
New experimental results are presented for the solubility of carbon dioxide, hydrogen sulfide in the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]) at temperatures range from (303.15 to 353.15) K and pressures up to about 2 MPa. The solubility of the mixture of CO2/H2S in [C8mim][PF6] under various feed compositions were also measured at temperatures of (303.15, 323.15 and 343.15) K and the pressure up to 1 MPa. The solubility of carbon dioxide and hydrogen sulfide increased with increasing pressure and decreased with increasing temperature and the solubility of H2S is about three times that of CO2 in the particular ionic liquid studied. The measured data were correlated using extended Henry’s law included Pitzer’s virial expansion for the excess Gibbs energy, and the generic Redlich–Kwong cubic equation of state proposed for gas/ionic liquid systems. The correlations from the two models show quite good consistency with the experimental data for CO2/IL and H2S/IL binary mixtures within experimental uncertainties. For CO2/H2S/IL ternary mixtures, the RK model shows better correlation with the experimental values. We also studied the effect of cation alkyl chain length on the CO2 and H2S solubility by comparison of the experimental data of this study with those of previous reports. As the cation alkyl chain length became longer, the solubility of CO2 and H2S increased in the ionic liquid. Additionally, the influence of the anion on the solubility is studied by comparing the solubility of CO2 and H2S in [C8mim][PF6] with those in [C8mim][Tf2N]. As a result, CO2 and H2S have higher solubility in the IL with [Tf2N] as the anion.  相似文献   

12.
In this paper, ascorbic acid as a new carbon dioxide (CO2) absorbent was investigated. The equilibrium solubility of CO2 into 0.5, 1 and 1.5 mol dm−3 (M) aqueous ascorbic acid solutions were measured experimentally with a stirred batch reactor at total atmospheric pressure over the CO2 partial pressure ranging from 0 to 45 kPa and temperatures between 298 and 313 K. The results of the gas solubility are presented as loading capacity (mol CO2/mol ascorbic acid) as function of partial pressure of CO2 for all experimental runs. Experimental results showed that solubility of CO2 increases with increase in molar concentration of ascorbic acid solution at a given temperature and decreases with increase in temperature at a given concentration. The densities and viscosities of the ascorbic acid solutions were measured at the same conditions of the solubility measurement. Some corrosion rate tests were also performed on carbon steel at temperature of 308 K. It was observed that viscosity and corrosion rate increase when the molar concentration of ascorbic acid solution increases.  相似文献   

13.
The solubility of quercetin and its thermal degradation was studied in CO2-expanded ethanol and ethyl lactate. An equipment setup was constructed that enabled the separation of the products of degradation while quantifying the solubility of quercetin. Three different conditions of temperature were analyzed (308, 323, and 343 K) at 10 MPa. Higher solubility and thermal degradation of quercetin were observed for CO2-expanded ethyl lactate in comparison with CO2-expanded ethanol. At the same time, as the amount of CO2 was increased in the CO2-expanded liquids mixtures, the thermal degradation of quercetin decreased for almost all the conditions of temperature considered in this work. The importance of considering thermal degradation while performing solubility measurements of compounds that are thermally unstable such as quercetin was highlighted.  相似文献   

14.
In this study, sorption and diffusion of carbon dioxide (CO2) in wood‐fiber/polystyrene composites were investigated. The effects of gas pressure and fiber content on the solubility and diffusion coefficients were evaluated. A statistical analysis indicated that pressure is more important than fiber content in determining the solubility and diffusivity of CO2. An increase in saturation pressure causes an increase in the solubility and diffusion coefficients, whereas inclusion of the fibers decreases both of these properties. Models were developed to predict the uptake and diffusion coefficients of CO2 in the composite samples as functions of pressure and fiber content. A theoretical model based on Henry's law and the Langmuir equation compared favorably to the experimental data for CO2 solubility. This dual mode model also described both the transient sorption and desorption data, but only if the concentration‐dependent value of diffusivity was treated as a history‐dependent parameter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 723–735, 2002  相似文献   

15.
Electrochemical reduction of carbon dioxide (CO2) into value‐added chemicals is a promising strategy to reduce CO2 emission and mitigate climate change. One of the most serious problems in electrocatalytic CO2 reduction (CO2R) is the low solubility of CO2 in an aqueous electrolyte, which significantly limits the cathodic reaction rate. This paper proposes a facile method of catholyte‐free electrocatalytic CO2 reduction to avoid the solubility limitation using commercial tin nanoparticles as a cathode catalyst. Interestingly, as the reaction temperature rises from 303 K to 363 K, the partial current density (PCD) of formate improves more than two times with 52.9 mA cm?2, despite the decrease in CO2 solubility. Furthermore, a significantly high formate concentration of 41.5 g L?1 is obtained as a one‐path product at 343 K with high PCD (51.7 mA cm?2) and high Faradaic efficiency (93.3 %) via continuous operation in a full flow cell at a low cell voltage of 2.2 V.  相似文献   

16.
Halogen bonding interactions between several halogenated ion pairs and CO2 molecules have been investigated by means of density functional theory calculations. To account for the influence of solvent environment, the implicit polarized continuum model was also employed. The bromide and iodide cations of ionic liquids (ILs) under study can interact with CO2 molecules via X O interactions, which become much stronger in strength than those in the complexes of iodo-perfluorobenzenes, very effective halogen bond donors, with CO2 molecules. Such interactions, albeit somewhat weaker in strength, are also observed between halogenated ion pairs and CO2 molecules. Thus, the solubility of CO2 may be improved when using halogenated ILs, as a result of the formation of X O halogen bonds. Under solvent effects, the strength of the interactions tends to be weakened to some degree, with a concomitant elongation of intermolecular distances. The results presented here would be very useful in the design and synthesis of novel and potent ILs for CO2 physical absorption.  相似文献   

17.
Polymeric membrane-based gas separation technology has significant advantages compared with traditional amine-based CO2 separation method. In this work, SEBS block copolymer is used as a polymer matrix to incorporate triethylene oxide (TEO) functionality. The short ethylene oxide segment is chosen to avoid crystallization, which is confirmed by differential scanning calorimetry and wide-angle X-ray scattering characterizations. The gas permeability results reveal that CO2/N2 selectivity increased with increasing content of TEO functional group. The highest CO2 permeability (281 Barrer) and CO2/N2 selectivity (31) were obtained for the membrane with the highest TEO incorporation (57 mol%). Increasing the TEO content in these copolymers results in an increase in CO2 solubility and a decrease in C2H6 solubility. For example, as the grafted TEO content increased from 0 to 57 mol%, the CO2 solubility and CO2/C2H6 solubility selectivity increased from 0.72 to 1.3 cm3(STP)/cm3 atm and 0.47 to 1.3 at 35°C, respectively. The polar ether linkage in TEO-grafted SEBS copolymers exhibits favorable interaction with CO2 and unfavorable interaction with nonpolar C2H6, thus enhancing CO2/C2H6 solubility selectivity.  相似文献   

18.
Ionic liquids with tetracyanoborate ([TCB]?) and bis(trifluoromethanesulfonyl)amide ([Tf2N]?) anions generally have low viscosities and high CO2 capacities, and thus they are attractive solvents for CO2-related applications. Herein, we have investigated physical and CO2-absorption properties of 1-ethyl-3-methylimidazolium tetracyanoborate ionic liquid ([emim][TCB]) to discuss the anion effects of [TCB]? in comparison with the previous results of [emim][Tf2N]. The density, viscosity, electrical conductivity, and isobaric molar heat capacity were measured as a function of temperature at atmospheric pressure. [emim][TCB] has both lower density and isobaric molar heat capacity than [emim][Tf2N]. [emim][TCB] shows superior transport properties (lower viscosity and higher electrical conductivity) compared to [emim][Tf2N], whereas the Walden plots of molar conductivity against fluidity (reciprocal of viscosity) have smaller values in [emim][TCB] than in [emim][Tf2N] at certain fluidities. The high-pressure CO2 solubilities were also determined in [emim][TCB]. The mole fraction scaled solubility of CO2 in [emim][TCB] is slightly larger than that in [emim][Tf2N] at certain pressures and temperatures. The former ionic liquid shows much higher molarity scaled solubility of CO2 than the latter because of the smaller molar volume. It is suggested that both anions have similar strength of intermolecular interaction with CO2 and comparable changes in the solvent structure between neat and CO2 solution, in view of the thermodynamic parameters of dissolution.  相似文献   

19.
Foamed polylactide (PLA), PLA–PBAT (poly (butylene adipate‐co‐terphathalate)) blend and their composites with CaCO3 were prepared in a batch process using supercritical carbon dioxide (CO2) at 12 MPa and 45°C. The solubility of CO2 and its diffusion patterns in different PLA samples was investigated. PLA systems had a relatively high CO2 solubility related to the carboxyl groups. CO2 desorption behaviors in PLA systems first followed the Fickian diffusion mechanism in short time and then decreased slowly to a plateau. The addition of both PBAT and CaCO3 into PLA impeded the desorption of CO2. In the presence of second phase PBAT, nanoparticles CaCO3 and dissolved CO2, the PLA crystallization behavior investigated by DSC technique was greatly changed. As the desorption time increased, the gas induced crystallinity slightly decreased in consequence of less CO2 content in each system and thus less plasticization effect. The cell morphology of foamed PLA and PLA composites showed interesting microstructure patterns. The prepared pure PLA foam exhibits a typical bimodal structure because of the foaming in both the amorphous and crystalline zones. With PBAT and CaCO3 into PLA, the composite foam presented significant increase in cell uniformity and cell density. With less CO2 content in each PLA sample, the cell structure showed interesting variation. Pure PLA foam presented transition from bimodal structure to more uniform cell structure with decreased cell density. In contract, PLA–PBAT foam show unfoamed regions because of none CO2 left in the separated PBAT phase. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
Supercritical carbon dioxide (CO2) and poly(ethylene glycol) (PEG) can be utilized as an environmentally friendly biphasic solvent system for catalysis reactions and subsequent product separation. To efficiently implement this technology, it is important to understand how solutes partition between these phases as well as how dissolved CO2 in PEG affects the solvent properties. The work presented here explores the influence of CO2 on the solubility of four different solutes in PEG. The transferable potentials for phase equilibria-united atom force field and configurational-bias Monte Carlo molecular simulation were employed to determine the solubilities of ethylbenzene, 1-octene, 1-pentanol, and 2-pentanone at 323.15 K and 15?MPa in PEG-600 using an ideal vapor phase with a Poynting-corrected vapor pressure. The effect of CO2 concentration within the PEG phase was determined by varying the amount from no CO2 to the saturation limit. The results indicate that while there is preferential solvation of CO2 around the solutes, solubility of non-polar solutes is unchanged whereas there is a modest increase for polar solutes as the concentration of CO2 increases. Increased solubility is analyzed in terms of both modified solvent structure and direct solute–CO2 interactions.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号