Measurement and Correlation of Liquid-liquid Equilibria for 1-Hexene-n-Hexane-3-Methysulfolane

Utilizing solvent extraction to separate alkanes and olefins from catalytic light gasoline is an effective method for maximizing the utility of gasoline fractions.This study presents the determination of liquid-liquid equilibrium data for the ternary system of 1-hexene-n-hexane-3-methylsulfolane at 30℃,40℃,and 50℃under atmospheric pressure.The obtained data facilitated the construction of a ternary phase diagram for the system.The results showed that the extraction selectivity of 1-hexene/n-hexane exceeded 1.5 when using 3-methylsulfolane as the extraction solvent.Furthermore,the thermodynamic consistency of the experimental data was examined using Hand’s equation and the Othmer-Tobias method.The correlation coefficient,R^(2)≥0.9578,indicated the acceptable reliability of the phase equilibrium data.Subsequently,the NRTL(non-random two liquid)model was used to correlate the liquid-liquid phase equilibrium data and derive the binary interaction parameter.Notably,the results demonstrated that the root mean square deviation of the NRTL model correlation values from the experimental values did not exceed 2.5%.

Liquid-Liquid Equilibria of Water + Butyric Acid + Nonanol Ternary System

Liquid-liquid equilibrium (LLE) data for the water + butyric acid + nonanol system have been determined experimentally at the temperatures of 298.15 K, 308.15 K and 318.15 K. Tie-line compositions were correlated by Othmer-Tobias method. The universal quasichemical functional group activity coefficient (UNIFAC) and modified UNIFAC methods were used to predict the phase equilibrium in the system using the interaction parameters between CH3, CH2, COOH, OH and H2O functional groups. Distribution coefficients and separation factors were evaluated for the immiscibility region.

Liquid-Liquid Equilibria of the Water-Ethanol-Dimethyl Succinate Ternary System

Liquid-liquid equilibrium (LLE) data for the ternary systemwater-ethanol-dimethyl succinate have been determined experimentallyat temperatures ranging from 298.15 to 318.15 K at 5 K intervals.Complete phase diagrams were obtained by determining solubility andthe tie-line data. Tie-line compositions were correlated byOthmer-Tobias method. The universal quasichemical functional groupactivity coefficient (UNIFAC) and modified UNIFAC methods were usedto predict the phase equilibrium in the system using the interactionparameters deter- Mined from experimental data between groups CH_3,CH_2, OH, CH_3 COO and H_2O.

AN NEW GROUP-CONTRIBUTION EQUATION OF STATE AND ITS APPLICATION TO PHASE EQUILIBRIUM CALCULATIONS(Ⅲ)Application to Liquid-Liquid Equilibria

Based on the group interaction parameters determined from binary VLE data,the VDW-GC EOS developedin Part I~[13] is extended to binary and multicomponent liquid-liquid equilibrium calculations.Equilibrium phasecompositions and the temperature effects on LLE can be predicted with reasonable accuracy.

Experimental Study on Liquid-Liquid Equilibria of Alcohol- Ester-Water-CaCl_2 System

The binary liquid-liquid equilibrium(LLE) data for salt-containing systems of 1-butanol+water+CaCl2, n-butyl acetate+water+CaCl2 and ethyl acetate+acetic acid+water+CaCl2 were determined and the salt effect was analyzed. The results showed that an obvious salt effect could be identified for the systems of 1-butanol+water+CaCl2 and ethyl acetate+acetic acid+water.

Phase equilibria relations in the V_(2)O_(5)-rich part of the Fe_(2)O_(3-)TiO_(2)-V_(2)O_(5) system at 1200℃ related to converter vanadium-bearing slag

The efficient recycling of vanadium from converter vanadium-bearing slag is highly significant for sustainable development and circular economy.The key to developing novel processes and improving traditional routes lies in the thermodynamic data.In this study,the equilibrium phase relations for the Fe_(2)O_(3)-TiO_(2)-V_(2)O_(5)system at 1200℃in air were investigated using a high-temperature equilibrium-quenching technique,followed by analysis using scanning electron microscopy-energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy.One liquid-phase region,two two-phase regions(liquid-rutile and liquid-ferropseudobrookite),and one three-phase region(liquid-rutile-ferropseudobrookite)were determined.The variation in the TiO_(2)and V_(2)O_(5)contents with the Fe_(2)O_(3)content was examined for rutile and ferropseudobrookite solid solutions.However,on further comparison with the predictions of FactSage 8.1,significant discrepancies were identified,highlighting that greater attention must be paid to updating the current thermodynamic database related to vanadium-bearing slag systems.

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Upper-rim-modified thioether thiacalix[4]arene used for liquid-liquid extraction of Au(Ⅲ)and Pd(Ⅱ)in hydrochloric acid medium

Gold(Au)and palladium(Pd)play an increasing role in the production and human life;Therefore,it is of great significance to study their recovery.A 5,11,17,23-tetra-ethylthio-25,26,27,28-tetra-hydroxyl thiacalix[4]arene(TCAET)was synthesized specifically for the capture of Au(Ⅲ)and Pd(Ⅱ)from HCl medium by liquid-liquid extraction.In a 0.1 mol·L^(-1)HCl medium,the transfer of Au(Ⅲ)and Pd(Ⅱ)from the aqueous phase to the organic phase was highly efficient,with a transfer ratio of 100%for Au(Ⅲ)and 98%for Pd(Ⅱ).Furthermore,the extraction equilibrium time for Au(Ⅲ)was just 5 min.Job's method data demonstrated that TCAET formed complexes with Au(Ⅲ)and Pd(Ⅱ)in a ratio of 2:3 and 1:1,respectively,during the extraction process.TCAET showed high selectivity toward Pd(Ⅱ)and Au(Ⅲ)over other competing metal ions.Moreover,both Au(Ⅲ)and Pd(Ⅱ)could be successfully stripped from the loaded organic phases with a 1.0 mol·L^(-1)thiourea in 0.5 mol·L^(-1)HCl and 0.5 mol·L^(-1)thiourea in 0.5 mol·L^(-1)HCl,respectively.Results obtained from five consecutive extraction-stripping cycles showed good reusability of TCAET toward Au(Ⅲ)and Pd(Ⅱ)recovery.The conclusion can provide a certain reference for thiacalixarene in the recovery of precious metal species.

Study on Osmotic Pressure and Liquid-Liquid Equilibria for Micelle, Colloid and Microemulsion Systems by Yukawa Potential

An equation of state (EOS) was established to study the osmotic pressure and liquid-liquid equilibria for micelle, colloid and microemulsion systems. The Carnahan-Starling equation was used for the hard sphere repulsion. The Yukawa potential was used to describe both the attractive dispersion and the double-layer repulsion. By using the established EOS, the osmotic pressures for charged colloid, uncharged micelle, uncharged and weakly charged microemuslion, the phase equilibria for uncharged micelle and charged colloid systems were studied.

The extraction of aromatics using N-methylpyrrolidone: Liquid-liquidequilibrium determination and mechanism exploration

LLE data of cyclooctane/3-methylpentane + benzene/toluene + N-methylpyrrolidone (NMP) at 298.15 Kand 313.15 K under a pressure of 101.3 kPa were measured in this work. The Othmer-Tobias and Handequations were adopted to validate the reliability of LLE data, where the correlation coefficients (R2) wereclose to unity, indicating the high reliability of the experimental data. The experimental data were analyzed using the distribution coefficient (D) and separation factor (S), and the effect of NMP extracting benzene and toluene from aromatics was explored. Meanwhile, the reason for the different extractionefficiencies of benzene and toluene using NMP was analyzed by quantum chemical calculations. TheNRTL and UNIQUAC thermodynamic models were used to correlate the liquid–liquid equilibrium data,and the relevant binary interaction parameters were obtained. The calculated root mean square deviation(RMSD) were all less than 0.0063, indicating that the obtained binary interaction parameters can be usedto simulate and calculate the extraction of aromatics using NMP.

STUDIES ON VAPOR-LIQUID AND LIQUID-LIQUIDVAPOR EQUILIBRIA FOR THE TERNARY SYSTEM METHANOL-METHYL METHACRYLATEWATER (Ⅱ) TERNARY SYSTEM

Isothermal P-x data for homogeneous, and P-x’-x" data for partially miscible mixtures for the ternary system methanol-methyl methacrylate-water have been determined at 25, 35, 45, 55 and 60℃. By using a modified UNIQUAC model and binary parameters only, the predicted ternary phase equilibrium data were found to be in good agreement with the experimental results, indicating the adequacy of using binary model parameters in computing vapor-liquid and liquid-liquid-vapor equilibria covering pressures ranging from reduced to atmospheric.

Helically symmetric equilibria for some ideal and resistive MHD plasmas with incompressible flows

In this paper, the problem of finding exact solutions to the magnetohydrodynamic(MHD) equations in the presence of incompressible mass flows with helical symmetry is considered. For ideal flows, a similarity reduction method is used to obtain exact solutions for several MHD flows with nonlinear variable Mach number. For resistive flows parallel to a magnetic field, the governing equilibrium equation is derived. The MHD equilibrium state of a helically symmetric incompressible flow is governed by a second-order elliptic partial differential equation(PDE) for the helical magnetic flux function. Exact solutions for the latter equation are obtained. Also, the equilibrium equations of a gravitating plasma with incompressible flow are derived.

Investigation on small molecule-aptamer dissociation equilibria based on antisense displacement probe

Food safety is a major issue to public health and have attracted global attention.Fast,sensitive,and reliable detection methods for food hazardous substances is highly desirable.Aptamers which can bind to the target molecules with high affinity and specificity represent an attractive tool for the recognition of food hazardous substances,which play an important role in the development and application of new food safety detection technology.But current assays for characterizing small molecule-aptamer binding are limited by either the mass sensitivity or the size differentiation ability.Herein,we proposed a comprehensive method for assessing the dissociation equilibria of small molecule-aptamer,which is immobilized-free under ambient conditions.The design employs the Le Chatelier’s principle and could be used to effectively measure small molecule-aptamer interactions.ATP binding aptamer and anti-aflatoxin B1 aptamer were used as the model system to determine their affinity,in which their dissociation equilibria measurements are in excellent close to their previous work.Due to the simplicity and sensitivity of this new method,we believe that it could be recommended as an effective tool for characterizing small molecule-aptamer interactions and promote the further application of small molecular aptamer in food safety.

CO_(2)-海水水合物生成强化方法研究

海水中的盐离子成分阻碍水合物成核进程,使得水合物法海洋碳封存耗时长、封存比率低。结合水合物非均相成核特征考虑,认为在局部区域内实现水合物优先成核,进而带动大片海域内水合物扩展生成的封存方法极具工业可行性。因而,开展海水水合物强化生成方法基础研究是推进水合物法海洋碳封存应用落地的基础。基于此,以高效、高转化率生成水合物为目标,在实验室尺度分别探究了高过冷度、添加剂四丁基溴化铵(TBAB)以及变温速率对海水水合物生成特性的影响。结果表明,受到盐离子抑制作用,400 m深度海水中水合物自然生成难度极大,而提高生成过程的过冷度可增强水合物生成驱动力;热力学添加剂TBAB难以显著改善海水水合物的生成条件,但可使生成速率有所提高;0.3 K/min降温速率下的水合物转化率分别是过冷度作用和添加剂作用下的1.28倍和1.19倍。在后续研究中,应考虑多种强化生成方法的耦合作用效果,开发更能缓解海水水合物生成难题的技术手段。

基于稳定性分析的含酸/醇烃水体系相平衡计算

油气开发的井流物多以油气水混相形式存在。对于酸性油气田,还常伴有硫化氢或二氧化碳等酸性气体。为了避免水合物生成堵塞管道,加注醇类防冻剂是常用的方法。因而油气田井流物易于呈现含酸、含醇的多相烃水混输状态。含酸/醇烃水体系相平衡的准确计算,是预测其物性特征的基础,也是支持该复杂体系多相混输流动仿真的关键。但目前被广泛应用的基于经典立方型状态方程计算油气水体系相平衡的方法,存在对液烃及水相分布预测准确性不高的问题。为此,引入稳定性分析的方法,构建适用于含酸/醇烃水体系的稳定性检验方式,结合SRK-HV状态方程,建立了耦合稳定性分析的含酸/醇烃水多相多组分相平衡计算模型及算法。经多角度验证,本研究所提模型具有较高的准确性与稳定性。

锂钠镁共存硫酸盐体系多温相图及其应用

针对硫酸钠亚型盐湖卤水钠锂比高、镁锂比高带来的锂分离难题,通过开展锂钠镁共存硫酸盐体系多温相图研究,获取锂钠镁硫酸盐之间的作用关系和结晶析出规律,并应用于指导降低卤水中钠镁含量工艺设计。采用等温溶解平衡法获取了四元体系Li_(+),Na_(+),Mg^(2+)//SO_(4)2--H_(2)O 303.2、318.2 K固液相平衡数据,采用X射线粉晶衍射法(XRD)测定了共饱点的平衡固相类型。复盐分析:采用XRD、扫描电镜(SEM)和热重分析法(TG-DSC)进行了各复盐的晶体结构分析、晶体形貌表征和热分析。研究发现,四元体系Li_(+),Na_(+),Mg^(2+)//SO_(4)^(2-)-H_(2)O303.2、318.2 K下均为复杂体系,相图均包含4个四元共饱点、9条单变量曲线和6个结晶区。303.2 K时,该体系相图结晶区为:Na_(2)SO_(4)、Na_(2)SO_(4)·10H_(2)O、Li_(2)SO_(4)·H_(2)O、MgSO_(4)·7H_(2)O、Na_(2)SO_(4)·MgSO_(4)·4H_(2)O、Li_(2)SO_(4)·3Na_(2)SO_(4)·12H_(2)O;318.2 K时,该体系相图结晶区为:Na_(2)SO_(4)、MgSO_(4)·7H_(2)O、Li_(2)SO_(4)·H_(2)O、Na_(2)SO_(4)·MgSO_(4)·4H_(2)O、Li_(2)SO_(4)·Na_(2)SO_(4)、Li_(2)SO_(4)·3Na_(2)SO_(4)·12H_(2)O。对比该四元体系288.2、298.2、303.2、318.2、323.2 K多温相图发现,温度对体系的影响主要表现在水合盐和含锂复盐的结晶形式及各盐类结晶区面积的变化。根据四元体系多温相图中含锂复盐(Li_(2)SO_(4)·Na_(2)SO_(4)、Li_(2)SO_(4)·3Na_(2)SO_(4)·12H_(2)O)、白钠镁矾(Na_(2)SO_(4)·MgSO_(4)·4H_(2)O)和三元体系Na_(+),Mg^(2+)//SO_(4)2--H_(2)O多温相图中盐类的结晶规律,给出了硫酸钠亚型盐湖脱钠镁及白钠镁矾的分离加工建议。

六氟化铀及氟化物汽液相平衡数据预测及精馏过程模拟

精馏技术提纯六氟化铀是铀转化工艺的重要环节,该精馏工艺的模拟可为工艺设计及操作优化提供关键支撑。然而,由于六氟化铀及氟化物汽液相平衡数据及物性数据的缺乏,六氟化铀提纯精馏工艺的建模和模拟难以开展。为此,利用COSMOtherm和Turbomole软件,预测UF_(6)与TiF_(4)二元体系汽液相平衡数据。通过预测已知的WF_(6)-UF_(6)二元体系汽液相平衡实验数据以间接验证COSMO-RS模型预测的准确性。利用Aspen Plus软件的物性常数估算系统(property constant estimation system),估算出缺失的无限稀释水溶液Gibbs生成能等物性参数。文献中UF_(6)饱和蒸气压实验数据与模拟值进行对比,相对误差在1.76%以内。根据文献中的实验数据和预测的汽液相平衡数据,利用Aspen Plus软件回归NRTL模型的二元交互作用参数。针对六氟化铀及氟化物的分离,设计直接分离序列和间接分离序列提纯UF_(6)的两种方案。设定UF_(6)产品纯度,以总年度费用(TAC)最小化为目标,采用灵敏度分析对塔板数、进料位置和回流比的关键参数进行优化,结果表明,间接分离序列提纯UF_(6)方案的TAC更低。

三元混合制冷剂R290+R600a+N2汽液相平衡实验研究

在氢气液化工艺中,预冷循环是重要的一环,其中混合制冷剂(mixed refrigerant,MR)预冷循环是单位能耗比较低的,故对MR性能的优化显得尤为重要.为此利用液相单相循环法搭建汽液相平衡(Vapor-liquid equilibrium,VLE)实验系统,研究了R290+R600a+N_(2)三元体系的VLE性质,在273.15 K~323.15 K的温度范围内,对三元混合工质R290+R600a+N_(2)进行实验研究,并获得18组实验数据.同时使用Peng-Pobinson-Stryjek-Vera (PRSV)状态方程结合van der Waals(vd W)混合法则对R290+R600a、R290+N_(2)、R600a+N_(2)三组二元体系的VLE文献数据进行了拟合计算,得到二元交互作用系数,拟合结果与文献数据吻合良好.以此为基础,推算该三元体系的VLE性质.最后将实验数据与计算结果对比表明,体系压力平均相对偏差AARDp为0.85%,系统组分R290、R600a和N_(2)的气相平均绝对偏差AADy_(1)、AADy_(2)和AADy_(3)分别为0.0064、0.0027和0.0063,证明实验结果数据合理可靠,可以满足工程上的应用.

三元体系Na+(Mg^(2+)),Ca^(2+)//Cl^(-)-H_(2)O 278.2 K稳定相平衡研究

含钠镁钙水盐体系的多温相平衡研究,可为含钙镁盐湖资源的持续开发提供数据支撑。因此,采用等温溶解法开展了两个三元体系Na+,Ca^(2+)//Cl^(-)-H_(2)O和Mg^(2+),Ca^(2+)//Cl^(-)-H_(2)O在278.2 K下的相平衡研究,测定了溶解度、折射率和密度,并绘制了相应的相图。结果表明,三元体系Na+,Ca^(2+)//Cl^(-)-H_(2)O和Mg^(2+),Ca^(2+)//Cl^(-)-H_(2)O在278.2 K时均为简单体系,无复盐或固溶体生成。三元体系Na+,Ca^(2+)//Cl^(-)-H_(2)O在278.2 K时的氯化钠结晶区远大于氯化钙,对比该体系273.2、278.2、298.2、348.2 K多温相图可知,随温度升高,氯化钠结晶区增大,氯化钙结晶形式由CaCl_(2)·6H_(2)O转变为CaCl_(2)·2H_(2)O。三元体系Mg^(2+),Ca^(2+)//Cl^(-)-H_(2)O在278.2 K时的MgCl_(2)·6H_(2)O结晶区大于CaCl_(2)·6H_(2)O,对比该体系273.2、278.2、303.2、308.2、348.2、383.2 K多温相图发现:303.2、308.2、348.2、383.2 K时体系中形成复盐2MgCl_(2)·CaCl_(2)·12H_(2)O,且其结晶区随温度升高而增大;383.2 K时体系中同时存在两种复盐2MgCl_(2)·CaCl_(2)·12H_(2)O和MgCl_(2)·2CaCl_(2)·6H_(2)O。

NaHCO_(3)溶液浓度改变引起的支配质子转移反应变化:从HCO_(3)^(-)质子自递反应到HCO_(3)^(-)水解反应

NaHCO_(3)水溶液中存在多个质子转移反应和多重化学平衡。随溶液浓度改变,各质子反应所占的相对比重将发生变化,与质子转移相关的产物H_(2)CO_(3)、H^(+)、OH^(-)和CO_(3)^(2-)的相对含量也会发生变化。绘制了[H_(2)CO_(3)]、[H^(+)]、[OH^(-)]和[CO_(3)^(2-)]随溶液浓度c变化的动态图。从动态图上,可以直观地观察到哪些酸碱组分是主要组分,哪些组分是次要组分。较浓溶液中,[H_(2)CO_(3)]≈[CO_(3)^(2-)]>>[OH^(-)]>>[H^(+)],表明能够产生H^(+)或OH^(-)的质子反应占据次要地位,质子反应HCO_(3)^(-)+HCO_(3)^(-)-H_(2)CO_(3)+CO_(3)^(2-)占据支配地位。9.1×10^(-6) mol-L^(-1)溶液中,[OH^(-)]≈[H_(2)CO_(3)]>>[H^(+)]≈[CO_(3)^(2-)],表明质子反应H_(2)O+HCO_(3)^(-)-H_(2)CO_(3)+OH^(-)占据支配地位。极稀溶液中,[OH^(-)]≈[H^(+)]>>[H_(2)CO_(3)]>[CO_(3)^(2-)],表明H_(2)O-H^(+)+OH^(-)占据支配地位。溶液的酸碱性质主要由起支配作用的质子转移反应控制。