Phase Splitting Behavior Research Articles

Novel biphasic solvent based on 2MPRZ absorbent for post-combustion CO2 capture with low viscosity, superior phase-splitting behavior and low energy consumption

The CO2 phase change absorbents(CPCAs) formed by introducing phase-splitting agents have attracted increasing attention because of their great energy-saving potential. However, the volatilization problem of the phase-splitting agents and the high viscosity of the solution affect the application of CPCAs. In this work, a novel CPCAs based on 2-Methylpiperazine (2MPRZ)/H2O was established by introducing triethylene glycol monobutyl ether (TGBE) with a high boiling point as a phase-splitting agent, and the 2MPRZ/H2O/TGBE system exhibited low volatility and low viscosity. The CO2 capture performance of the novel CPCAs with different ratios was investigated in this work. The best CO2 absorption rate was achieved by 2.5 M 2MPRZ/H2O/TGBE. The viscosity of this system before and after the CO2 absorption process was merely 7.68 mPa·s and 11.64 mPa·s, respectively, and no volatilization of the phase-splitting agent was observed simultaneously. A convenient and rapid titration method was employed to determine the distribution of the 2MPRZ products in the two phases, which showed that 98 % of the 2MPRZ products were located in the CO2-rich phase. In addition, the CO2-rich phase captured 99 % of the total CO2, indicating that this system has superior phase-splitting behaviors. The regeneration energy consumption of this biphasic absorbent was 2.59 GJ/t CO2, which was 32.6 % lower than that of traditional MEA. Furthermore, the salting-out effect was proved to be the cause of the phase-splitting behavior by 13C NMR analysis.

Boosting CO2 absorption and desorption of biphasic solvent by nanoparticles for efficient carbon dioxide capture

Introduction of nanoparticles (NPs) in the solvent was treated an efficient route to enhance mass and heat transfer, therefore, it was a promising strategy to boost carbon dioxide (CO2) absorption and desorption, especially for the biphasic solvent with weak absorption rate and low heat capacity. Herein, powder TiO2 and SiO2 with nanoscale was selected to prepare nanofluid for CO2 capture, based on DMPA-NHD biphasic solvent. The stability of nanofluid and the effect of NPs on CO2 absorption–desorption, phase-splitting was comprehensively explored in this work. Experimental results revealed that 0.06 wt% dosage of 30 nm TiO2 presented excellent performance for CO2 absorption. The liquid film resistance decreased by 11.8% after introducing NPs, therefore, the maximum mass transfer coefficient was 1.88 × 10-10 mol·cm−2·s−1·Pa (at 30 °C), increasing by 30% than the blank. In addition, 0.06 wt% dosage of 50 nm SiO2 leaded to significant promotion for CO2 desorption, with the maximum desorption rate at 3.9 mmol/min, and the desorption energy consumption reduced by 9.5% compared with blank case. Importantly, introduction of NPs had no significant effect on the phase splitting behavior, according to the time-profile phase-splitting measurements. The advantage influence of NPs was well validated by current DEEA-AEEA and MEA-sulfolane biphasic solvent. Furthermore, the bench-scale CO2 absorption and desorption evaluation revealed that the relative energy consumption was respectively reduced by 15.9% and 10.0%, after introduction of 50-Si-NPs and 30-Ti-NPs.

Review of recent trends and various techniques for CO2 capture: Special emphasis on biphasic amine solvents

In the present scenario, the hazardous impacts of greenhouse gases can be restricted by adopting carbon capture and storage (CCS) technology that captures most of the CO2 emitted by numerous industries, human activities, and mostly from thermal power plants. This paper reviewed the main CO2 capturing technologies, i.e., pre-combustion, post-combustion, and oxy-combustion, along with their different operating conditions, performances, and comparisons. Some industrial processes used to capture CO2 by physical solvents are presented with their properties and working conditions. Methodologies like absorption, adsorption, membrane technology, cryogenic separation, and microalgae process are presented. Single alkanolamine-based solvents have limited CO2 loading and high regeneration energy demand, attracting researchers to work on their various amine blends. In today’s scenario, biphasic solvents play a vital role in the field of CO2 capture. Some amine solvent blends show biphasic behavior, leading to faster reaction, higher absorption capacity, and lower regeneration energy. The solvent screening for the biphasic solvent is very rigorous and still challenging. In this work, various blends selected by the researchers with the potential for phase-splitting behavior are reviewed, and the best among them is reported.

Studies on the aggregation behavior of mineral acid and Zr(IV) loaded Tris(2-methylbutyl) phosphate and tri-n-alkyl phosphate systems using small angle neutron scattering

ABSTRACT The third-phase phenomenon has been observed during the extraction of certain metal ions and mineral acids by 30% (v/v) tri-n-butyl phosphate (TBP) in n-dodecane in the solvent extraction stage of spent nuclear fuel reprocessing. At molecular scale, it has been predicted that the self-organization of the extracted polar species to form reverse micelle-like structure is primarily responsible for third-phase formation. In this regard, the aggregation behavior of solutions of three different trialkyl phosphates in n-alkanes loaded with monoprotic mineral acids (HClO4, HCl and HNO3) as well as tetravalent Th and Zr has been evaluated using Small Angle Neutron Scattering (SANS). The aggregation of TBP has been compared with two of its five carbon analogues i.e. tri-n-amyl phosphate (TAP) and tris(2-methylbutyl) phosphate (T2MBP), which have gained its attention in the course of development of an alternate extractant for the reprocessing process. The effects of trialkyl phosphate structure, diluent chain length and extractant concentration on the aggregation have been emphasized. The contribution of the polar (anionic and cationic component) as well as the apolar part of the reverse micelle toward the phase splitting behavior has been analyzed. The SANS results are in agreement with the earlier reported solvent extraction data.

Aggregation and organic phase splitting behavior of a synergic extractant system probed by dynamic light scattering spectroscopy

A synergic solution of N,N-di-n-octyl-2-hydroxyacetamide (DOHyA) and bis-(2-ethylhexyl)diglycolamic acid (HDEHDGA) in n-dodecane has been proposed for the single-cycle separation of Am(III) and Cm(III) from high-level nuclear waste containing chemically similar lanthanides in 3–4 M nitric acid medium. The reverse micellar aggregation behavior of the binary extractants in n-dodecane has been studied in the synergic extraction regime (>1 M nitric acid) by dynamic light scattering (DLS) spectroscopy. The results were compared with the individual extractants in n-dodecane. The aggregation of reverse micelles increased with increase in the loading of nitric acid and Nd(III) in the organic phase in all organic solutions. The organic phase underwent splitting into two phases, with the lighter one “diluent-rich” and the heavier one “aggregate rich” at a particular limiting value of Nd(III) and nitric acid loading in the organic phase. Accordingly, the limiting reverse micellar aggregate size in organic phase for third phase formation was determined, and it was found to increase with increase in the polarity of the ligand in organic phase. Studies with simulated nuclear waste revealed that the binary solution composed of (0.2 M DOHyA +0.1 M HDEHDGA)/n-DD would not undergo phase splitting as the aggregate size formed in organic phase was much lower than the limiting aggregate size of 15 nm for phase splitting in the present case.

Splitting between two subgroups of the SCN neurons with instantaneous feedback

Phase-splitting and various arrhythmic behaviors have been observed in mammals. Although it is known that desynchronization of SCN neurons plays an important role, the exact mechanisms underlying this behavior are still not completely understood. A previous study suggested that phase-splitting behavior was explained by the SCN output signal feeding back to the SCN with a time delay of about 12 h. However, experimental evidence showed that the feedback is instantaneous and does not have a time delay. In the present study, a Kuramoto model with instant feedback is proposed to explain the mechanisms underlying phase splitting and arrhythmic behavior. Our results show that phase-splitting and arrhythmic behavior results from the feedback which is described by two key parameters, the strength of the feedback as well as the phase difference of the feedback to the SCN activity. Additionally, in accordance with experimental findings, we observe that the SCN period in the split state is equal to 24 h, while it is larger than 24 h for a state that has a robust circadian rhythm. Our study provides an alternative explanation for the phase-splitting and arrhythmic behavior and opens a window to understand how feedback influences the SCN, and consequently its behavior.

On the use of ionic liquids as adjuvants in PEG-(NH4)2SO4 aqueous biphasic systems: Phase diagrams behavior and the effect of IL concentration on myoglobin partition

Abstract The introduction of ionic liquids (ILs), either as phase forming components or as adjuvants, in the implementation of aqueous biphasic systems (ABS) enabled to finely tune the properties of the two aqueous phases in equilibrium thus providing the opportunity to increase extraction efficiencies and selectivities of biomolecules. Nevertheless, the effect of ILs addition on the phase diagram behavior and partitioning of biomolecules changes depending on the polymer, salt, ILs and biomolecules used and is still not fully understood. In this context, the influence of the addition of 7 different ILs based on imidazolium, pyrrolidinium or pyrydinium cation on PEG 3350 + ammonium sulfate ((NH4)2SO4) ABS at 25 °C is studied in this work. In terms of phase equilibrium, it was observed that the chemical nature of the IL leads to either a decrease or increase of two-phase region, therefore in the latter affording a decrease in concentrations of phase forming compounds needed for the liquid-liquid demixing. It is shown, that the IL anion affinity for water or the anion’s hydrogen-bond basicity controls the phase splitting behavior and thus [C4mim][N(CN)2] is able to greatly enhance two-phase region. Moreover, these PEG 3350 + (NH4)2SO4 + IL ABS were tested in the extraction/concentration of myoglobin from aqueous solutions. The obtained results indicate that the myoglobin partition is strongly influenced by its hydrophilicity and pH of the phases in equilibrium. Consequently, it preferentially partitions to the salt-rich phase. However, partitioning studies in presence of ILs as adjuvants show that these compounds can tune the polarity of the PEG-rich phase thus offering a tunable platform for the purification of myoglobin. This ability greatly depends on the chemical structure of the IL used and closely follows the IL hydrogen-bond basicity (β), enabling the most hydrophilic IL – [C4mim][CH3CO2] – to change the myoglobin partitioning behavior from salt-rich to the PEG-rich phase.

Performance of sulfolane/DETA hybrids for CO2 absorption: Phase splitting behavior, kinetics and thermodynamics

The phase splitting solvent as a promising alternative to MEA for CO2 capture has received an increasing attention due to its low energy consumption. In this paper, the mixture of diethylenetriamine (DETA) and sulfolane was employed to absorb CO2 from the simulated flue gas. Its phase splitting behavior was investigated. The species in each separated phase were identified using nuclear magnetic resonance (NMR), revealing that the upper layer was a CO2-rich phase and mainly consisted of DETA and DETA-carbamate. Whereas, the lower layer was CO2-lean phase with the sulfolane presented individually. The CO2 absorption kinetics was also measured in a wetted-wall column as a function of temperatures, CO2 loadings, and gas flow rate. Their impacts on the enhancement factor and mass transfer resistance were calculated by the Vapor-Liquid Equilibria (VLE) model, implying that the main CO2 mass transfer resistance gradually transferred from the gas side to the liquid side with the CO2 loading increasing from 0 to 2.21 mol L−1. During the CO2 absorption process, sulfolane acted as an inert solvent for substituting the role of water and separated from the absorption product. Consequently, the sensible heat and vaporization heat were substantially decreased by 59% and 12%, respectively. Hence the total heat duty was lowered by 19% which might noticeably advance the CO2 capture technology.

Effect of T-junction diameter ratio on stratified-wavy flow separation

Most of the research carried out on reduced diameter ratio T-junctions concluded that partial phase separation can be improved by decreasing the diameter ratio. Despite using very small diameter ratio T-junctions, petroleum industry has always faced the problem of continuous and sometimes very high liquid carryovers. In this regard, the separation of air-water stratified-wavy flow in 1.0, 0.52, 0.67, 0.27 and 0.20 diameter ratio T-junctions was examined to investigate the effect of diameter ratio on phase separation. Phase distribution of each T-junction was evaluated by observing the point at which liquid carryover starts (liquid carryover threshold) and the maximum liquid carryover delivered (peak liquid carryover). For optimum separation it is essential that liquid carryover threshold is high and peak liquid carryover is low, however these parameters were found to decrease with the reduction in diameter ratio. It was observed that in stratified-wavy flow, the drop in liquid carryover threshold was reasonable and thus in this flow regime a decrease in diameter ratio was always found to enhance phase separation. Two correlations were also developed to predict the phase splitting behavior, under a wide range of operating conditions.

Experimental investigation of phase split of gas–liquid two-phase flow through small holes at the pipe wall

An experimental and analytical study on phase split of gas–liquid two-phase flow through small holes at the main pipe wall has been performed in this paper. The inner pipe diameter of the test section is 40mm and the diameter of sampling hole is 2.5mm. Experiments were conducted in an air–water two-phase flow loop and four types of sampler with different arrangement of sampling-holes were tested. Stratified-wavy, annular and slug flows were observed. Experimental results show that phase splitting behavior is significantly influenced by the number and positions of the sampling-holes and the superficial velocities of the gas and liquid. If a swirl vane is mounted at the upstream of the four-hole sampler, an interesting phenomenon that the liquid extraction ratio maintains constant and is independent of the inlet flow patterns can be observed.

Salting-out induced three-liquid-phase separation of Pt(IV), Pd(II) and Rh(III) in system of S201−acetonitrile−NaCl−water

Salting-out induced three-liquid-phase system (TLPS) of diisopentyl sulfide (S201)−acetonitrile−NaCl−water was explored to extract and separate platinum, palladium and rhodium with one-step method. The influences of phase-forming behaviors of TLPS on partition of platinum-group metal (PGM) ions were investigated by changing the phase-forming salt and its concentration, HCl concentration in equilibrating salt aqueous phases and the initial volume ratio of acetonitrile to aqueous NaCl solution. Experimental results indicated Pd(II), Pt(IV) and Rh(III) were selectively concentrated into the S201 organic top phase, acetonitrile-rich middle phase and NaCl aqueous bottom phase respectively. The three-liquid-phase partition of platinum metal ions occurred with the salting-out induced two-phase splitting of acetonitrile–water mixtures. A micro-mechanism model is proposed to explain the influence of salting-out induced phase splitting behavior of three-liquid-phase system on mass transfer of PGM ions. Appearance of microscopic molecular aggregates accounts for the micro-phase enrichment of platinum metal ions. The competition of two opposite processes, salting-out induced dehydration of acetonitrile molecules in aqueous solutions while strong re-hydration of salting-out acetonitrile molecules in separated acetonitrile-rich phase, plays an important role in affecting the phase-forming behaviors and three-liquid-phase mass transfer of different platinum metal ions.

Mechanism of phase splitting in two coupled groups of suprachiasmatic-nucleus neurons

The phase-splitting behavior of coupled suprachiasmatic-nucleus neurons has been observed in many mammals, and its mechanism is still not completely understood. Based on our previous work [C. Gu, J. Wang, and Z. Liu, Phys. Rev. E 80, 030904(R) (2009)] on the free-running periods of neurons in the suprachiasmatic nucleus, we present here a modified Goodwin oscillator model to explain the mechanism of phase splitting. In contrast to the previous phase model, the modified Goodwin oscillator model contains the information on both the phase and amplitude and, thus, can show more features than the purely phase model, including all three behaviors of synchronization, phase splitting, and amplitude death and the distributed periodicity in the regions of synchronization and phase splitting, etc. An analytic phase model is extracted from the modified Goodwin oscillator model to explain the dependence of periodicity on the parameters. Moreover, both the modified Goodwin oscillator model and the analytic phase model show that the ensemble frequency can be enhanced or reduced by the time delay.

Dynamics of reactive distillation processes with potential liquid phase splitting based on equilibrium stage models

A dynamic reactive distillation (RD) column model is developed for highly non-ideal systems with potential phase splitting. Dynamic simulations and non-linear dynamic analysis are performed for recovery of acetic acid from waste waters by esterification with n-butanol, which is an interesting alternative to non-reactive separation processes. Two alternative RD column designs were tested with respect to their open loop transient responses to process disturbances. One parameter continuation with eigenvalue calculations reveals existence of multiple steady states with stable and unstable branches. These steady states were found to have totally different phase splitting behavior of the original liquid phase inside the column. Conclusions are drawn for process operation.

Use of Glycol Ethers for Selective Release of Periplasmic Proteins from Gram-Negative Bacteria

Genetic modification of Gram-negative bacteria to express a desired protein within the cell's periplasmic space, located between the inner cytoplasmic membrane and the outer cell wall, can offer an attractive strategy for commercial production of therapeutic proteins and industrial enzymes. In certain applications, the product expression rate is high, and the ability to isolate the product from the cell mass is greatly enhanced because of the product's compartmentalized location within the cell. Protein release methods that increase the permeability of the outer cell wall for primary recovery, but avoid rupturing the inner cell membrane, reduce contamination of the recovered product with other host cell components and simplify final purification. This article reports representative data for a new release method employing glycol ether solvents. The example involves the use of 2-butoxyethanol (commonly called ethylene glycol n-butyl ether or EB) for selective release of a proprietary biopharmaceutical protein produced in the periplasmic space of Pseudomonas fluorescens. In this example, glycol ether treatment yielded approximately 65% primary recovery with approximately 80% purity on a protein-only basis. Compared with other methods including heat treatment, osmotic shock, and the use of surfactants, the glycol ether treatment yielded significantly reduced concentrations of other host cell proteins, lipopolysaccharide endotoxin, and DNA in the recovered protein solution. The use of glycol ethers also allowed exploitation of temperature-change-induced phase splitting behavior to concentrate the desired product. Heating the aqueous EB extract solution to 55 degrees C formed two liquid phases: a glycol ether-rich phase and an aqueous product phase containing the great majority of the product protein. This phase-splitting step yielded an approximate 10-fold reduction in the volume of the initial product solution and a corresponding increase in the product's concentration.

Cyclohexanol Production via Esterification of Cyclohexene with Formic Acid and Subsequent Hydration of the EsterReaction Kinetics

An alternative to current production routes to cyclohexanol, the esterification of cyclohexene with formic acid and subsequent splitting of the ester can overcome many of the drawbacks associated with conventional processes. The process that is being considered could be carried out in a reactive distillation column. To develop such a process, reliable data on liquid−liquid and vapor−liquid phase-splitting behavior and on reaction kinetics is of high importance. The current publication focuses on the reaction kinetic aspects of such a process. Reaction kinetic data for the three equilibrium reactions are being presented

VLE and LLE Data Set for the System Cyclohexane + Cyclohexene + Water + Cyclohexanol + Formic Acid + Formic Acid Cyclohexyl Ester

The six-component system cyclohexene + water + cyclohexanol + cyclohexane + formic acid + formic acid cyclohexyl ester is currently being studied with the aim of carrying out the reaction of cyclohexene and water to cyclohexanol in a reactive distillation (RD) column. Because the direct reaction path of cyclohexene hydration is strongly limited by slow reaction rates with the known catalysts, an intermediate ester-formation step with formic acid was included in the studies. The challenge that this six-component system poses for a reactive separator such as an RD column lies in the liquid−liquid phase splitting behavior. This adds a third effect besides reaction and distillation. Cyclohexane is included in these studies to represent any inert C6 components present under industrial conditions. To be able to design an RD column, measurements were conducted of the liquid−liquid and vapor−liquid equilibria, and appropriate NRTL parameters matching both vapor−liquid and liquid−liquid phase splitting behavior we...

Manipulation of the Liquid−Liquid Equilibrium of Vertrel-XF + Hydrocarbon Solvent Systems with the Addition of a Third Component

Phase-transition extraction (PTE) is a recently developed separation technique using partially miscible solvent systems that demonstrate temperature-dependent phase splitting behavior. This separation technique exploits the ability to shift solvent systems across their liquid−liquid coexistence curves, alternating between homogeneous and two-phase systems to achieve the desired separation. This work examines the phase behavior of fluorinated−hydrocarbon solvent systems and the ability to manipulate their critical solution temperatures (CSTs) with the addition of a third component. In addition to PTE, knowledge of the liquid−liquid equilibria (LLE) of these systems has applications to biphasic and homogeneous fluorous phase chemistry and the improved recycling and recovery of fluorous solvents. The LLE of ternary systems containing a hydrofluorocarbon, Vertrel-XF, n-decane, and either n-hexane or 1-octene were determined in the temperature range of 273−323 K. The ability to manipulate the CST of Vertrel-XF + n-hexane and Vertrel-XF + 1-octene with the addition of n-decane was examined. Experimental data were correlated using the UNIQUAC and NRTL activity coefficient models. These models were capable of representing the temperature-dependent types I and II phase behavior observed for these systems.