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Liquid Systems (liquid + system)
Selected AbstractsPhase Transfer Catalysis in Solid,Liquid System as a Selective Method of Mono-alkylation of ,-Sulfonyl Thioesters.CHEMINFORM, Issue 40 2002Blanka Wladislaw Abstract For Abstract see ChemInform Abstract in Full Text. [source] Experiments, Modeling and Simulation of Drop Size Distributions in Stirred Liquid/ Liquid SystemsCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 8 2005A. Gäbler No abstract is available for this article. [source] Lanthanide Bis[(trifluoromethyl)sulfonyl]imides as Reusable Catalysts for Mononitration of Substituted Benzenes in Ionic LiquidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Shuojin Wang Abstract Lanthanide bis[(trifluoromethyl)sulfonyl]imides as a kind of effective catalyst were used in quaternary ammonium ionic liquids to afford a useful new method for the nitration of substituted benzenes with concentrated nitric acid (95%) as nitrating agent. The less expensive lanthanum bis[(trifluoromethyl)sulfonyl]imide was found to be the most effective catalyst employed in the ionic liquid tributylammonium bis[(trifluoromethyl)sulfonyl]imide. The lanthanum bis[(trifluoromethyl)sulfonyl]imide/tributylammonium bis[(trifluoromethyl)sulfonyl]imide system demonstrated high catalytic activity for the nitration of halobenzenes and rendered good to excellent yields. This catalyst/ionic liquid system could be recovered by simple procedures and recycled for at least 5 times. [source] Disjunctive optimization design models for complex liquid,liquid multistage extractorsAICHE JOURNAL, Issue 10 2001Juan A. Reyes-Labarta A new method for the optimal design of multicomponent liquid,liquid extraction processes using multistage countercurrent extractor systems is proposed. The method determines the optimum number of equilibrium stages and flow rates needed to obtain a specified product separation and recovery, and accounts for the possibility of side feed streams and product extractions. A superstructure is proposed that has embedded all potential configurations and interconnections. Based on this superstructure representation, the problem is formulated as an optimization problem using generalized disjunctive programming (GDP) to minimize the total cost of the process, subject to design specifications. The robustness and computational efficiency of the model is illustrated with different cases involving single and complex countercurrent cascades in a quaternary liquid,liquid system. [source] Screening of antioxidant phenolic compounds in Chinese Rhubarb combining fast counter-current chromatography fractionation and liquid chromatography/mass spectrometry analysisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2010Ruilin Hu Abstract In this paper, an effective method combing fast elution-extrusion counter-current chromatography (CCC) and LC/MS for rapid screening of antioxidative phenolic compounds in Chinese Rhubarb is presented. An integrated three-coil CCC column (40,mL each coil) was used to accomplish the optimization of biphasic liquid system. In a single run (approximately 40,min), the solvent system composed of n -hexane/ethyl acetate/methanol/water (1:1:1:1, v/v) was selected as optimum CCC liquid system for fast fractionation of the crude ethanol extract. With a 140,mL-capacity CCC instrument, 100,mg Chinese Rhubarb extract was separated under the optimized conditions, producing six fractions in only 100,min. The quantities of each fraction were ,15,mg. In addition, each fraction was subjected to antioxidant activity assay and characterized by LC/MS analysis. Fifty compounds, including phenolic acids, phenolic glucosides and hydroxyanthraquinones, were detected by LC/MS/MS analysis. As a result, gallic acid together with Fr I showed excellent antioxidant activity, which was well consistent with previous studies and exhibited great potential for natural drug discovery program of the present method. [source] A new effective combination of a thin-film extractor and gravity setterTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2001Yuli Berman Abstract Previous and present studies demonstrate that the new thin-film extractor with the gravity settler have superior performance over other conventional devices. This is because the volume of the extractor and the settler are significantly reduced, on the average, by factors of 100 and 10, respectively, for a similar power input. Correlations for a water-iodine-kerosene liquid system developed in the past (Berman and Tamir, 2000) for the mass transfer and pressure drop were modified by incorporating the ratio R/Rr This ratio takes into account the impact of the liquids on the walls of the reactor where R is the radius of the free film and Rr is the radius of the reactor. In addition, an equation was proposed, which demonstrates the dependence of the extraction efficiency on the operating parameters. The gravity settler combined with the thin-film extractor was tested thoroughly yielding two correlations for estimating its height, i.e. the fluidized-bed and dense-packed zones. In the present case the sedimentation zone is absent. A scale up procedure based on the model developed is proposed as well as a principle scheme of a pilot plant based on the new effective combination Les études antérieures tout comme la présente étude démontrent que le nouvel extracteur à film mince combiné à un séparateur gravitaire a une performance supérieure par rapport à d'autres systèmes conventionnels. Cela est dû au fait que les volumes de l'extracteur et du sédimenteur sont largement réduit, en moyenne, d'un facteur 100 et 10 respectivement, pour une alimentation énergétique comparable. En introduisant le rapport R/Rr on a modifié des corrélations pour un système liquide eau-iode-kérosène déjà établies (Berman et Tamir, 2000) pour le transfert de matière et la perte de charge. Ce rapport tient compte de l'impact des liquides sur les parois du réacteur, où R est le rayon du film libre et Rr le rayon du réacteur. De plus, une équation est proposée, qui démontre que l'efficacité d'extraction dépend des paramètres de fonctionnement. Le séparateur gravitaire combiné à l'extracteur à film mince a été testé en profondeur, ce qui a conduit à deux corrélations pour estimer sa hauteur, c'est-à-dire les zones lit fluidisé et garnie-dense. Dans le cas présent, la zone de sédimentation est absente. Une mise à l'échelle est proposée d'après le modèle élaboré ainsi qu'un schéma de principe d'une usine pilote à partir de cette nouvelle combinaison efficace. [source] Influence of carbonation on aroma release from liquid systems using an artificial throat and a proton transfer reaction,mass spectrometric technique (PTR,MS)FLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2009Maria Ángeles Pozo-Bayón Abstract To determine whether carbonation affects aroma release from liquid systems, carbonated and non-carbonated flavoured model systems were prepared and volatile release was determined under static (equilibrium) and dynamic conditions. A model flavour system was added as a single compound or as a mixture of the six aroma compounds used in this study. Volatile release under dynamic conditions involved using a home-made device simulating an artificial throat, coupled to a proton transfer mass spectrometer (PTR,MS). The results showed that carbonation increased the release of most of the aroma compounds in both static and in dynamic testing conditions. The extent of this effect depended, however, on the physicochemical characteristics of the aroma compounds (the most volatile and most hydrophobic compounds were affected more). Release was also increased if the aroma compounds were added as a mixture rather than as individual compounds. CO2 appears to be a key factor responsible for the enhanced release of flavourings from carbonated liquid systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Luminescent Soft Material: Two New Europium-Based Ionic LiquidsHELVETICA CHIMICA ACTA, Issue 11 2009Sifu Tang Abstract Two new Eu-based ionic liquid systems, [C4mim][DTSA],:,[Eu(DTSA)3] and 2[C4mim] [DTSA],:,[Eu(DTSA)3] were synthesized at 120° under inert conditions from 1-butyl-1-methylimidazolium ditoluenesulfonylamide ([C4mim][DTSA]). The identity and purity of the synthesized compounds were confirmed by elemental analysis, IR, Raman, and 1H-NMR spectroscopy. As they solidify below 100° as glasses they qualify as ionic liquids. Fluorescence measurements show that the materials exhibit a strong red luminescence of high color purity. Therefore, they have the potential to be used for optical applications such as in emission displays. [source] Level-set based numerical simulation of a migrating and dissolving liquid drop in a cylindrical cavityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2004Edmondo Bassano Abstract In the present paper the dissolution of a binary liquid drop having a miscibility gap and migrating due to thermo-solutal capillary convection in a cylindrical cavity is studied numerically. The interest in studying this problem is twofold. From a side, in the absence of gravity, capillary migration is one of the main physical mechanisms to set into motion dispersed liquid phases and from the other side, phase equilibria of multi-component liquid systems, ubiquitous in applications, often exhibit a miscibility gap. The drop capillary migration is due to an imposed temperature gradient between the cavity top and bottom walls. The drop dissolution is due to the fact that initial composition and volume values, and thermal boundary conditions are only compatible with a final single phase equilibrium state. In order to study the drop migration along the cavity and the coupling with dissolution, a previously developed planar two-dimensional code is extended to treat axis-symmetric geometries. The code is based on a finite volume formulation. A level-set technique is used for describing the dynamics of the interface separating the different phases and for mollifying the interface discontinuities between them. The level-set related tools of redistancing and off-interface extension are used to enhance code resolution in the critical interface region. Migration speeds and volume variations are determined for different drop radii. Copyright © 2004 John Wiley & Sons, Ltd. [source] Prediction of two-phase pressure drop and liquid holdup in co-current gas,liquid downflow of air,Newtonian systems through packed bedsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2006Ponnan Ettiyappan Jagadeesh Babu Abstract The dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed. Our experimental data (825 data points obtained using four liquid systems and three different particles) along with those of the available literature (776 data point from five different sources) were used for the analysis. The applicability and the limitations of the literature correlations were evaluated using the available data. Based on the analysis, new correlations for the estimation of pressure drop and liquid holdup, valid for low and high interaction regimes have been developed using the available data, with a wide range of variables. Copyright © 2005 Society of Chemical Industry [source] Minimum fluidization velocity and gas holdup in gas,liquid,solid fluidized bed reactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2002K Ramesh Abstract Experiments were performed to study the hydrodynamics of a cocurrent three-phase fluidized bed with liquid as continuous phase. Based on the 209 experimental data (with four liquid systems and five different particles) along with 115 literature data from six different sources on minimum fluidization velocity, a unique correlation for the estimation of minimum fluidization velocity in two-phase (ug,=,0) as well as in three-phase systems is developed. A data bank consisting of 1420 experimental measurements for the fractional gas phase holdup data with a wide range of variables is used for developing empirical correlations. Separate correlations are developed for two flow regimes observed in this present work. The proposed correlations are more accurate and simpler to use. © 2002 Society of Chemical Industry [source] Computational analysis of an instantaneous chemical reaction in a T-microreactorAICHE JOURNAL, Issue 6 2010Dieter Bothe Abstract We extend and apply a method for the numerical computation of convective and diffusive mixing in liquid systems with very fast irreversible chemical reaction to the case of unequal diffusivities. This approach circumvents the solution of stiff differential equations and, hence, facilitates the direct numerical simulation of reactive flows with quasi-instantaneous reactions. The method is validated by means of a neutralization reaction which is studied in a T-shaped micromixer and compared with existing experimental LIF-data. Because of their large are-to-volume ratio, microreactors are well suited for fast chemical reactions which are seriously affected by the slow diffusive transport in aqueous media. Numerical computations for different reactor dimensions reveal the fact that, in a dimensionless setting, the obtained conversion is independent of the reactor size, if the flow conditions are the same. This corresponds to an increase of space-time-yield proportional to the square of the inverse scale factor. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Acrylic polymers as thickening agents for tetraglycol cosolventJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2006Giulia Bonacucina Abstract This article evaluated the thickening properties of two different Eudragits, L and RS, in tetraglycol cosolvent in order to obtain high viscosity systems characterized by controlled release properties. Tetraglycol was chosen for its ability to dissolve a wide range of water insoluble drugs, while Eudragit RS and L for their specific dissolution and permeability properties under physiological conditions. Study of the rheological properties was performed to characterize elastic and viscous properties of Eudragit/tetraglycol samples in function of frequency and temperature. For all systems, the results outlined a liquid like behavior, as observed for dilute polymer solutions. In fact the fitting of the log G,-log G,, versus frequency curves showed a good agreement with the Rouse or Zimm models. So despite the increase in viscosity, samples still behaved like liquid systems. After the addition of paracetamol the release characteristics were defined pointing out the great release control properties of both Eudragit L and RS, which showed different release kinetics depending on the pH of the environment. Semisolid Eudragits/tetraglycol systems can be considered as a new alterative for the sustained release of insoluble or poorly water-soluble drugs. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:726,736, 2006 [source] Analysis of time-resolved X-ray scattering data from solution-state systemsACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2010Kristoffer Haldrup As ultrafast time-resolved studies of liquid systems with the laser pump/X-ray scattering probe method have come of age over the past decade, several groups have developed methods for the analysis of such X-ray scattering data. The present article describes a method developed primarily with a focus on determining structural parameters in the excited states of medium-sized molecules (~30 atoms) in solution. The general methodology is set in a maximum-likelihood framework and is introduced through the analysis of the photoactive platinum compound PtPOP, in particular the structure of its lowest triplet excited state (3A2u). Emphasis is put on structure determination in terms of model comparisons and on the information content of difference scattering signals as well as the related experimental variables. Several suggestions for improving the accuracy of these types of measurements are presented. [source] Prediction of Minimum Fluidization Velocity in Two and Three Phase Inverse Fluidized BedsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003Thiruvengadam Renganathan Abstract Generalized equations for predicting minimum fluidization velocities in two-phase L-S and three-phase G-L-S inverse fluidized bed are developed covering a wide range of variables using the experimental data obtained from the present work and that available in the literature. It is found that the classical Wen and Yu equation for predicting minimum fluidization velocity can satisfactorily be used for two-phase inverse fluidized bed. A model based on empiricism and another based on the gas perturbed liquid model, which reduce to limiting conditions such as liquid solid and three-phase batch liquid systems are proposed. Des équations généralisées pour la prédiction des vitesses de fluidisation minimales dans des lits fluidisés inverses biphasique liquide-solides et triphasique gaz-liquide-solides ont été établies pour une vaste gamme de variables à l'aide des données expérimentales issues du présent travail et de la littérature scientifique. On a trouvé que l'équation classique de Wen et Yu pour prédire la vitesse de fluidisation minimale peut être utilisée pour le lit fluidisé inverse biphasique. On propose un modèle empirique et un autre basé sur le modèle de liquide perturbé par le gaz, qui se réduisent aux conditions limitantes tels les systèmes liquides discontinus liquide-solides et triphasiques. [source] Development of a Novel Polyimide Hollow-fiber OxygenatorARTIFICIAL ORGANS, Issue 5 2004Motohiro Niwa Abstract:, We have developed a membrane oxygenator using a novel asymmetric polyimide hollow fiber. The hollow fibers are prepared using a dry/wet phase-inversion process. The gas transfer rates of O2 and CO2 through the hollow fibers are investigated in gas,gas and gas,liquid systems. The polyimide hollow fiber has an asymmetric structure characterized by the presence of macrovoids, and the outer diameter of the hollow fiber is 330 µm. It is found that the polyimide hollow-fiber oxygenator can enhance the gas transfer rates of O2 and CO2, and that the hollow fiber provides excellent blood compatibility in vitro and in vivo. [source] Ultrasonically enhanced delivery and degradation of PAHs in a polymer,liquid partitioning system by a microbial consortiumBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Pedro A. Isaza Abstract The current study examined the effects of ultrasonic irradiation on mass transfer and degradation of PAHs, by an enriched consortium, when delivered from polymeric matrices. Rates of release into methanol under sonicated conditions, relative to unmixed cases, for phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene were increased approximately fivefold, when delivered from Desmopan 9370 A (polyurethane). Similar effects were observed in Hytrel and Kraton® D4150 K polymers as well as recycled Bridgestone tires. Enhancements were also displayed as shifts to higher release equilibria under sonicated conditions, relative to non-sonicated cases, agreeing with current knowledge in sonochemistry and attributed to cavitation. Ultrasonic effects on microbial activity were also investigated and cell damage was found to be non- permanent with consortium re-growth being observed after sonic deactivation. Finally, the lumped effect of sonication on degradation of phenanthrene delivered from Desmopan was examined under the absence and presence of sonication. Rates of degradation were found to be increased by a factor of four demonstrating the possibility of using ultrasonic irradiation for improved mass transport in solid,liquid systems. Cellular inactivation effects were not evident, and this was attributed to the attenuation of sonic energy arising from the presence of solid polymer materials in the medium. The findings of the study demonstrate that sonication can be used to improve mass transport of poorly soluble compounds in microbial degradations, and alleviate limiting steps of soil remediation processes proposed in previous research. Biotechnol. Bioeng. 2009; 104: 91,101 © 2009 Wiley Periodicals, Inc. 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