Liquid-phase Systems Research Articles

A jet mixing study in two phase gas–liquid systems

All studies concerned with jet mixing have been focused on liquid phase systems and no studies have been found on jet mixing for gas–liquid two phase systems. In the present study the use of jet fluid as a mixer in gas–liquid systems was proposed. Further by installing an experimental setup, the mixing behavior of liquid phase was studied. Gas flow and jet flow are injected to the mixing vessel countercurrently. In this study, the effect of jet injection, location of the conductivity probe, aeration rate and jet Reynolds number on the mixing time are investigated. The created flow pattern was extracted for each condition and the results often analyzed on the basis of them. It is observed that, for low aeration rates, the injection of jet decreases the mixing time considerably. By increasing the aeration rate, the difference in mixing times between the two cases of jet injection and without jet is reduced. Results also show that the closer the probe is to encounter location of the jet and airflow, the lower the mixing time obtained. Dependence of mixing time on the probe location decreases by increasing the mixing intensity and eliminating dead zones. It is obtained, on the basis of Re j and the amount of jet travelling in the vessel, increasing the aeration rate has different effects on the performance of mixing. Generally, four different trends for the variation of mixing time with increasing the aeration rate are observed.

Preparation technology of effective fraction of Catharsius molossus based on determination of effective composition and characterization of physico-chemical property

To optimize the preparation technology of effective fraction of Catharsius molossus, and investigate the feasibility of process control by the physical and chemical characterization of extracts. Used single-factor test method, choosed the main effective components of peptides and amino acids as indexes, combined with theology, chemistry, electricity, and other characterization, the study researched the prepared technology of effective fraction of C. molossus including extraction, concentration, separation, purification, drying and so on. The optimal preparation technology of effective fraction of C. molossus was that soaked an amount of crude drugs with three times of 85% ethanol for 48 h, added 10 times of 85% ethanol, percolated in 4 mL x min(-1) x kg(-1), collected percolation liquid, concentrated to 1:1 at 50-55 degrees C, removed fat by frozen, adopted DA201-C macroporous resin, used 1 BV of water and 4 BV of 70% ethanol as eluting agent, collected eluant respectively. The water part was concentrated and dried, then washed twice with 85% ethanol, collected washing liquid and mixed with 70% ethanol eluant. The product was obtained by concentrating and dring. At the same time, the liquid-phase system of each link was characterized in preparation of effective fraction of C. molossus, which showed that the surface tension related to polypeptide was essentially unchanged, and the conductivity related to salt decreased by about 90% with ineffective substances closely related to salt The results showed that the preparation technology maximumly retained the effective information, and removed the invalid information. The preparation technology of effective fraction of C. molossus is stable and reliable, and the process control in physico-chemical characterization of extracts is feasible.

Grafting of Imidazolium Based Ionic Liquid on the Pore Surface of Nanoporous Materials—Study of Physicochemical and Thermodynamic Properties

Supported ionic liquid phase (SILP) systems were prepared by immobilizing a methylimidazolium cation based ionic liquid onto the pore surface of two types of support, MCM-41 and Vycor. The "grafting to" method was applied, involving (3-chloropropyl)-trialkoxysilane anchoring on the supports' silanol groups, followed by treatment with 1-methylimidazole and ion exchange with PF(6)(-). Optimum surface pretreatment procedures and reaction conditions for enhanced ionic liquid (IL) loading were properly defined and applied for all modifications. A study on the effect of different pore sizes on the physical state of the grafted 1-(silylpropyl)-3-methylimidazolium-hexafluorophosphate ([spmim][PF(6)(-)]) was also conducted. The [spmim][PF(6)(-)] crystallinity under extreme confinement in the pores was investigated by modulated differential scanning calorimetry (DSC) and X-ray diffraction (XRD) and was further related to the capacity of the developed SILP to preferentially adsorb CO(2) over CO. For this purpose, CO(2) and CO absorption measurements of the bulk ionic liquid [bmim][PF(6)(-)] and the synthesized alkoxysilyl-IL were initially performed at several temperatures. The results showed an enhancement of the bulk IL performance to preferentially adsorb CO(2) at 273 K. The DSC analysis of the SILPs revealed transition of the melting point of the grafted alkoxysilyl-IL to higher temperatures when the support pore size was below 4 nm. The 2.3 nm MCM-41 SILP system exhibited infinite CO(2)/CO separation capacity at temperatures below and above the melting point of the bulk IL phase, adsorbing in parallel significant amounts of CO(2) in a reversible manner. These properties make the developed material an excellent candidate for CO(2)/CO separation with pressure swing adsorption (PSA) techniques.

Impact of Multi-Interface Surfactant Adsorption on Wettability in Dense Nonaqueous Phase Liquid Systems

The wettability, and hence the distribution and transport, of dense nonaqueous phase liquid (DNAPL) wastes in the subsurface is strongly affected by surfactants that are present in the wastes. To understand their impact, this work examined the dependence of the contact angle of quartz/tetrachloroethylene (PCE)/water systems containing the anionic surfactant Aerosol OT (AOT) or/and the nonionic surfactant hexaoxyethylene glycol mono-n-dodecyl ether (C12E6) on the surfactants' adsorption at both the PCE/water and silica/water interfaces. Results showed that C12E6 enhanced oil wetness at low pH. However, the system reverted to water-wet upon the addition of AOT, which by itself, did not alter the wettability of the system. To mechanistically explain such behavior, it was proposed that, based on measurements of adsorption onto quartz and calculations of surface excess using an equation-of-state approach, the increased oil-wetness in systems containing C12E6 is due to the entropy-driven attraction between the oxyethylene groups of the adsorbed C12E6 at both the PCE/water and water/silica interfaces. Addition of AOT reduced the adsorbed C12E6 at both interfaces, lowering the attraction between PCE and silica. Thus, a consideration of surfactant adsorption at both interfaces, and the subsequent interaction between the molecules sorbed at both interfaces, is critical to explaining the wettability behavior of waste DNAPLs.

In vitro Study of a Novel Method to Repair Human Enamel

AbstractThe chemical regeneration method of human enamel was improved for the probable clinical application: an oral medical device was designed to significantly reduce the necessary amount of remineralization liquid; the reactive liquid phase system was redesigned, thus the solution could be stored for long time.

Thermodynamic Study of Liquid Phase Synthesis of Ethyl tert-Butyl Ether Using tert-Butyl Alcohol and Ethanol

In this study, a detailed thermodynamic analysis of the ethyl tert-butyl ether (ETBE) synthesis reaction between tert-butyl alcohol (TBA) and ethanol is performed to determine a liquid phase equilibrium constant expression. The result is of practical significance in view of the imminent prominence of ETBE to be produced from TBA and ethanol, as a gasoline blending oxygenate. In this study, enthalpy of formation, Gibbs, enthalpy of vaporization, and heat capacities (as a function of temperature) of the reactants and products were estimated. At 298 K, the standard molar enthalpy of reaction for ETBE from TBA and ethanol was found as −1.23 kJ·mol−1. The liquid phase nonideality of the system was tested, and it was found that the system approaches ideal conditions. The thermodynamic analysis approach given here is expected to be useful for other liquid-phase systems.

Potential of adsorption isotherm measurements for closer elucidating of binding in chiral liquid chromatographic phase systems

The human body is a chiral environment and many drugs are chiral and interact differently depending on the type of enantiomer. Therefore, the interest in analytical and preparative separations of enantiomers has steadily increased over the years. LC is today the most important technique in analytical laboratories worldwide. The key to understand the separation system lies in the adsorption isotherm, which describes the equilibrium distribution of solutes between the mobile and stationary phases. By measuring adsorption isotherms in chiral phase systems, a deeper interpenetration concerning enantioselective and non-selective binding energies and adsorption processes is possible. Furthermore, this data provides the core information needed to optimize preparative chromatographic processes for purification of single enantiomers. However, the measurement of adsorption isotherms is a delicate matter and there are many dangerous pitfalls that may produce erroneous results and even wrong mechanistic conclusions. This review summarizes the most relevant methods and a workflow will be given for avoiding the common pitfalls and obtaining reliable data. Several applications from the literature are also treated to give insight in what information can potentially be obtained from using this methodology.

Sitosterol bioconversion with resting cells in liquid polymer based systems

The use of a biocompatible water-immiscible organic phase as a substrate and product pool has been acknowledged as an effective tool to overcome the low volumetric productivity of aqueous bioconversion systems involving hydrophobic compounds. The growing environmental and public health awareness is nevertheless leading to restrictions in the use of organic solvents in industrial processes, in order to render these more environmentally friendly. Different approaches are hence being assessed for the design of alternative bioconversion media, involving the use of supercritical fluids, ionic liquids and natural oils and liquid polymers, among others. In this work, the use of liquid polymers as key components in the bioconversion media for a multi-step microbial bioconversion was assessed. The model system used was the selective cleavage of the side-chain of β-sitosterol by free resting cells of Mycobacterium sp. NRRL B-3805, a well established industrial multi-enzymatic process involving the use of nine catabolic enzymes in a fourteen-step metabolic pathway. High product yields were obtained when silicone B oil was used as substrate carrier/product pool, both in single oil and in oil:buffer two liquid phase system.

Characteristics of pseudo-second-order kinetic model for liquid-phase adsorption: A mini-review

Since the introduction of pseudo-second-order (PSO) model for the description of adsorption kinetics in 1999, it has been widely applied in liquid-phase adsorption systems. An approaching equilibrium factor ( R w) was defined and deduced from the PSO model in this work. The adsorption characteristic curves were built up, in which three different zones of the PSO model were classified. Activated carbons with various particle sizes were prepared from fir wood with KOH activation for the adsorption of phenol, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and methylene blue (MB) from water. Suitable ranges of the PSO model and the effect of adsorbent particle size on the R w value were analyzed. It was found that the quantity k 2 q e was exactly the inverse of the half-life of adsorption process. It could be used as an indicator of kinetic performance because it was a key parameter affecting the fractional adsorption at any time. That is, k 2 q e, a newly defined rate index, could provide the related information between the static and dynamic behavior of adsorption processes in engineering practice.

Peak parking method for measurement of molecular diffusivity in liquid phase systems

The combination of series of measurements of band broadening made with the peak parking (PP) method, using successively an open capillary tube and a HPLC column, gives a convenient procedure for the measurement of the molecular diffusivity ( D m) of compounds in solutions, of their axial dispersion coefficient ( D ax,m) in chromatographic columns, and of the tortuosity or obstructive factor of the column bed. The molecular diffusivity measured for benzene in methanol was in excellent agreement with literature data. The ratio of the axial dispersion coefficient to this diffusivity gives the obstructive factor ( γ m) of the packed bed, which was 0.74 for the column used. The values of D m in other solutions were obtained from the D ax,m values measured by the PP method, by correcting the D ax,m values with the γ m value. The D m values determined by this method were in good agreement with those previously reported or estimated using literature correlations. These results showed that the PP method is effective for the experimental measurement of D m.

Cross-Platform Comparison of Methods for Quantitative Metabolomics of Primary Metabolism

Quantitative metabolomics is under intense development, and no commonly accepted standard analytical technique has emerged, yet. The employed analytical methods were mostly chosen based on educated guesses. So far, there has been no systematic cross-platform comparison of different separation and detection methods for quantitative metabolomics. Generally, the chromatographic separation of metabolites followed by their selective detection in a mass spectrometer (MS) is the most promising approach in terms of sensitivity and separation power. Using a defined mixture of 91 metabolites (covering glycolysis, pentose phosphate pathway, the tricarboxylic acid (TCA) cycle, redox metabolism, amino acids, and nucleotides), we compared six separation methods designed for the analysis of these mostly very polar primary metabolites, two methods each for gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). For analyses on a single platform, LC provides the best combination of both versatility and robustness. If a second platform can be used, it is best complemented by GC. Only liquid-phase separation systems can handle large polar metabolites, such as those containing multiple phosphate groups. As assessed by supplementing the defined mixture with (13)C-labeled yeast extracts, matrix effects are a common phenomenon on all platforms. Therefore, suitable internal standards, such as (13)C-labeled biomass extracts, are mandatory for quantitative metabolomics with any methods.

Assessment of the surface area occupied by molecules on activated carbon from liquid phase adsorption data from a combination of the BET and the Freundlich theories

A new equation is derived from a combination of the BET (Brunauer, Emmett, Teller) and Freundlich isotherms fitted for liquid phase adsorption data on activated carbons. This equation, depending on the Freundlich parameters and the equilibrium adsorption–desorption constant can be used for assessment of the surface area occupied by the solute molecules on a surface in a liquid phase system under some conditions.

Analysis of Oxygen Reduction Reaction Activity of Pt/C Catalysts for Actual PEFC MEAs

The dependence of the oxygen reduction reaction (ORR) activity of Pt/C catalysts used in actual polymer electrolyte fuel cell membrane electrode assemblies (PEFC MEAs) on cell temperature, O2 partial pressure and catalyst loading has been investigated. Based on physical chemistry and electrochemistry points of view, the charge transfer coefficient (α) was demonstrated to vary with potential over a narrow range of 0.5–0.6. The double Tafel slope occurring at potentials above 0.8 V vs. RHE was considered to be caused by the effect of adsorption or reaction of oxygen-containing species sourced by water. As a result, the α was assumed constant at 0.5 irrespective of the potential, and used in the estimation of the ORR activity [A/cm2-Pt]. The ORR activity was observed to increase linearly with increasing temperature. It was also found to be dependent on O2 partial pressure (considered as O2 concentration) until it reached a plateau at an O2 concentration of 40%, and then remained almost constant. This finding implies that in gas-phase PEFC MEAs, adsorption of O2 as a reactant can influence and govern the electrochemical reaction. In addition, the ORR activity is demonstrated to be independent of the Pt/C ratio of the catalyst not only for Pt plate electrodes in liquid-phase systems, but also for MEA electrodes in the gas-phase system of actual single-cell PEFCs. The ORR activity was found to be almost constant at 2.6 × 10–6 A/cm2-Pt at 60°C for Pt/C ratios from 19.3 to 55.8 wt%.

Analysis Method of Trace Compounds by Hollow-fiber Liquid-phase Microextraction with Electric Field Enhancement of Mass Transfer

Abstract A novel electric-field-enhanced liquid-phase microextraction system based on hollow fiber membrane has been developed. By introducing the radially enhancing electric field into this system, it is feasible to accelerate the mass-transfer rate of analyte and shorten the equilibrium time. In the process, the extract time was less than 4 min, which is much less than that of traditional liquid-phase microextraction. Further study is in progress.

Direct formation of silver nanoparticles in cuttlebone-derived organic matrix for catalytic applications

Development of biologically derived materials for the construction of materials with new functions is a crucial intersection of materials science and biotechnology, which is currently a topic of research interest. In this paper, we report on the use of cuttlebone-derived organic matrix (CDOM) as scaffold and reducer for the formation of silver nanoparticles (AgNPs). The experiment was carried out by simple immersing of CDOM in tollen’s reagent and incubating at 80 °C. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs are influenced by the incubation time and protein component in CDOM. Furthermore, the AgNPs–CDOM composite was applied to catalyze the reduction of 4-nitrophenol in the presence of NaBH 4, and it can be easily separated from the liquid-phase reaction system during the reusing cycles.

Luminescent characteristics of liquid-phase systems and polymer compositions containing europium β-diketonates solubilized with pluronics

The solubilization of europium β-diketonate complexes with amphiphilic polymers, ternary block copolymers of ethylene and propylene oxides (Pluronics), was shown to change luminescence intensity in such complexes. The association of europium β-diketonate complexes with Pluronics was proved by atomic force microscopy of agglomerates crystallized on mica surfaces from chloroform solutions of Pluronic F-127 in the presence and absence of the luminophores under study. In the absence of luminophores, Pluronic F-127 crystallized on a mica surface had a dendrite-like structure, while the evaporation of chloroform solutions containing both europium β-diketonates and Pluronic F-127 gave crystallized luminophore-Pluronic associates as compact islands with a characteristic size of ∼0.5 μm.

Preparation of supported H3PW12040·6H2O for thiophenic compounds alkylation in FCC gasoline

In FCC gasolines, thiophenic compounds alkylation with olefins of the feed followed by distillation of heavy sulfur compounds is a good alternative to classical hydrodesulfurization to eliminate sulfur. Among several acidic catalysts, silica-supported H3PW12O40·6H2O (HPW) has been found to be the best catalyst for the alkylation of 3-methylthiophene (3MT) with 2-methyl-2-butene (2M2B) taken as a model reaction in heterogeneous liquid phase systems at 358 K under nitrogen. The preparation of this catalyst has been optimized for this reaction and continuous catalytic tests have proved that this solid was very promising compared to traditional supported phosphoric acid or zeolites previously tested and used in industrial processes.

Potential Photooxidation Pathways of Dicarboxylic Acids in Atmospheric Droplets

Low molecular weight (LMW) dicarboxylic acids (DCAs) have received increasing attention because of their hygroscopic properties and capability of acting as cloud condensation nuclei (CCN). Based on the concentration profiles of intermediates identified during laboratory photooxidation of C7–C9 DCAs in a liquid-phase reaction system, chemometric analyses were conducted to examine the degradation pathways of DCAs for the formation of secondary DCAs. Among all secondary DCAs formed during the reaction, C4 and C5 DCAs showed the largest stoichiometric coefficients, indicating that sequential decarboxylation suggested in literature is unlikely the dominant pathway; other reaction routes e.g. preferential abstraction of hydrogen from carbon located at the central position of the DCA molecules by ·OH, followed by subsequent decomposition through the breakage of C-C bond, could play an important role.

Development of a comprehensive multidimensional liquid chromatography system with tandem mass spectrometry detection for detailed characterization of recombinant proteins

A multidimensional comprehensive liquid-phase separation system (2DLC) coupled on-line to an electrospray-ionization time-of-flight (ESI-TOF) mass spectrometer (MS) was used to resolve structural alterations and/or post-translational modifications for detailed protein characterization. The system described in this work consists of cation-exchange chromatography in the first dimension and reversed-phase chromatography in the second dimension. A unique spiked gradient was employed in the first dimension to enhance recovery of peptides. This combination of separation followed by MS detection offered the advantages of unique selectivity and high efficiency of the separation methods combined with the mass specificity and sensitivity of MS. During the course of this study it was determined that altered or modified peptides were shown to be better resolved than during a one-dimensional separation. The 2DLC/ESI methodology allowed for a comprehensive evaluation of post-translational modifications and chemical reactions of recombinant proteins, providing a meaningful evaluation of product quality that was not possible with other current analytical approaches. In addition, the system can be used to provide sequence coverage of complex proteins.

Physicochemical processes with coal particles in liquid-phase reduction. I

901 The reducing agent used in slag melt is coal, which enters the melt at temperatures of 1450‐1500 ° C. The coal undergoes coking here, with heating at 30‐50 K/s or more. The hydrogen, oxygen, and nitrogen in the coal’s organic mass enter the gas phase, along with some of the carbon and sulfur. The remainder of the carbon and the mineral components of the ash remain in the coke residue and subsequently participate in the processes occurring in the bath: combustion with the blast oxygen; and reduction by the metal oxides in the slag melt [1, 2]. To describe and control the processes in the slag bath, we require information on the quantitative and qualitative characteristics of coal coking at typical bath temperatures. There are extensive literature data on the coking of various coals [3, 4]. However, these data mainly refer to relatively low heating rates (10‐20 K/min) and coking temperatures of 900‐1000 ° C, whereas the temperature of the slag bath is 1400‐1500 ° C, with heating rates of 30‐50 K/s. Moreover, interest focuses here on the coking not of the bed but of individual particles. In that case, the following data are required for practical purposes: the yield and composition of the volatiles; the yield of coke and its content of solid carbon and ash; the removal of sulfur; the breakdown of the coal particles; the evaporation and conversion of water in pyrolysis. Because the processes occurring are so complex, it is not possible to obtain such information (except for the coke yield) in practice. Given the lack of experimental data, attempts have been made to calculate the corresponding characteristics [5]. The only remaining option is to formulate laboratory experiments corresponding to the operating conditions of the liquid-phase reduction system. In the present work, the experiments are conducted on OS Anzhersk coal from the Kuznetsk Basin, with the characteristics in Table 1. The yield and composition of volatiles are determined on equipment including a reactor, a flask with fiberglass for the absorption of tar, a flask with calcium chloride for the absorption of water, a flask with KOH for the absorption of CO 2 , a vessel with activated coal for the absorption of benzene and its derivatives, and a gasometer for gas collection. Before beginning the experiment, all the traps are weighed. In the experiment, the temperature of the trap for tar condensation is maintained at 125 ° C. To prevent further reaction of the decomposition products and the gaseous atmosphere of the reactor with the coke residue, pyrolysis is conducted in the volume of a slag (or metallic) melt. Tin is used as the metallic melt. A series of experiments on pyrolysis are also conducted in the reactor with no liquid phase. This corresponds to pyrolysis at the surface of the slag melt. The experimental results obtained here are identical.