超临界二氧化碳和脂质体系相平衡计算

对超临界CO2和一些脂质体系相平衡计算问题进行了研究.应用Peng-Robinson状态方程及Panagiotopoulos和Reid混合规则,改进能量参数a(T)后,用于计算脂质和超临界CO2组成的二元和三元体系的相平衡,结果与实验数据拟合精度较好.对于一些复杂的混合物如大豆油脱臭馏出物与超临界CO2体系,简化成拟三元、四元等体系进行了计算,计算结果达到一定的精度.     

超临界二氧化碳与二苯醚相平衡研究

为了解决煤焦油及其轻质化产物中二苯醚的萃取精馏分离问题以及为后续的高效分离过程提供工程数据,本文自行设计并搭建了一套流动法可视化高温高压相平衡测定装置,对二苯醚-二氧化碳体系的相平衡数据进行了测定,测定温度为313.15K、333.15K和353.15K,测定压力为8～18MPa,并使用Peng-Robinson (PR)和Soave-Redlich-Kwong（SRK）状态方程结合Quadratic、Adachi-Sugie、Mathias-Klotz-Prausnitz混合规则对的超临界二氧化碳与二苯醚相平衡数据进行了关联计算,关联结果表明PR和SRK状态方程结合AS混合规则可以获得较为准确的关联结果,而传统二次型混合规则得到的计算结果误差相对较大。此外,关联计算还表明,选择合适的混合规则后,不同状态方程的关联结果相差不大。这表明,对于低挥发性的液体与二氧化碳这类非对称混合物体系,相平衡模拟计算的关键在于选取合适的混合规则。     

神经网络计算脂肪酸酯与超临界CO_2体系相平衡

用2×2×1结构的BP神经网络计算了脂肪酸酯 超临界CO2体系的液相相边界溶解度数据,用2×4×2结构的BP神经网络对相平衡数据进行了计算,计算结果比较令人满意。同时对神经网络计算过程中涉及的一些参数也进行了讨论。     

二氧化碳和醇类体系相平衡的研究进展

CO2和醇类混合物的高压相平衡是化工、食品及药品工业设计和运行过程中的基础数据。笔者对CO2-醇类二元体系相平衡的实验测定和理论模型方面的进展进行了总结,并分析了适用于CO2和醇类体系高压相平衡计算的交叉缔合模型的发展方向。     

超临界CO2和植物油脱臭馏出物相平衡研究

研究了植物油脱臭馏出物在超临界CO2中的相平衡问题。基于组分的相似性把含有复杂组分的植物油脱臭馏出物简化为两种虚拟组分,用改进的混合规则和超临界组分的能量参数计算式,结合PR状态方程进行计算：理论计算与实验数据相吻合,为间歇式或连续逆流式超临界CO2萃取分离的设计提供了依据。     

新基团贡献型状态方程VDW—GC应用于超临界流体萃取过程的相平衡计算

本文将新开发的基团贡献型范德华方程应用于超临界流体萃取过程涉及的气-固、气-液两相平衡及气-固-固和气-液-液三相平衡的预测计算,取得了较为满意的结果。     

超临界CO2二元系统相平衡的数值模拟

应用微扰理论,借助微扰状态方程,对超临界CO2 系统相平衡进行了模拟。编制了求解程序,介绍了状态方程中各参数的确定方法和程序模块的设计思想。针对超临界CO2 /非极性体系、超临界CO2 /极性体系,在不同温度、压力条件下的气液相平衡进行了计算,将计算结果与实验结果进行了比较,结果表明:微扰状态方程适合模拟超高压下的CO2 二元体系的相平衡。     

RG-CPA方程计算超临界CO2-醇体系汽液相平衡

综合考虑缔合作用和密度涨落的影响,将经重整化群修正的CPA方程（RG-CPA方程）扩展到二元体系汽液相平衡的计算。通过一个温度下的汽液相平衡数据回归得到二元交互作用参数,预测其他温度下的相平衡。采用这种方法计算了超临界CO₂与醇二元体系的汽液相平衡性质和临界曲线。结果表明,RG-CPA方程预测超临界CO₂与醇二元体系的气液相组成和密度具有较高的精度,液相组分平均绝对偏差为0.032,气相组分平均绝对偏差为0.019。与原始CPA方程相比,RG-CPA方程能更好地预测气液临界曲线。     

超临界二氧化碳-乙醇二元体系的高压相平衡

High-pressure phase behavior of supercritical (SC) CO2 ethanol system was investigated at 333.2 K,348.2K, 353.2K, 368.2K, 413.2K and 453.2K and pressure from 2.0MPa to 14.3MPa. The measurement was carried out in a cylindrical autoclave with a moveable piston and a window for adjustment and observation of phase equilibria at given T and p. The samples were taken from two coexisting phases and were analyzed to obtain their compositions. It is shown that the solubility of SC CO2 in ethanol increases drastically with pressures at the given temperature, but the content of ethanol in CO2-rich phase increase faintly.     

超临界甲醇制备生物柴油的多元相平衡研究进展

超临界甲醇制备生物柴油与传统方法制备生物柴油相比具有着多方面的优点,包括无需催化剂、反应速率快、对原料要求低、产物不需要后处理,因而近年来越来越受到国际社会的关注。由于与酯转化相关的反应物、中间产物以及产物在甲醇中的高压相平衡是理解与调控超临界甲醇反应的基础,为更好的理解多元混合物高温高压相行为对于酯转化反应的控制条件和机理,需要对相关体系的高压相平衡、转酯化反应动力学以及二者之间的关系等基础性问题进行深入研究。但由于超临界流体对温度、压力变化的敏感性和高温高压取样的困难性,使得在相平衡方面的研究起步较晚,基础数据缺乏。本文比较了当前几种生物柴油生产方式的优缺点,同时对现有超临界甲醇制备生物柴油的多元相平衡研究进展情况进行了总结。     

Phase equilibria of alcohols in supercritical fluids Part II. The effect of side branching on C8 alcohols in supercritical carbon dioxide

This paper is a continuation of a previous study and investigated the phase equilibria of six C₈ alcohols (2,2,4-trimethyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 2-ethyl-1-hexanol, 2-propyl-1-pentanol, 4-methyl-3-heptanol and 6-methyl-2-heptanol) in supercritical carbon dioxide. Data has been measured between 308 and 348 K for alcohol mass fractions between 0.660 and 0.0162. The results show that the position, size and quantity of side chains have a significant effect on the phase behaviour by changing the shape of the molecule and the effect of the hydroxyl group on the polarity of the molecule. The pressure required for total solubility increases in the following sequence: 4-methyl-3-heptanol < 2,2,4-trimethyl-1-pentanol < 6-methyl-2-heptanol < 2,4,4-trimethyl-1-pentanol < 2-propyl-1-pentanol < 2-ethyl-1-hexanol < 1-octanol. The difference in phase behaviour is believed to be a result of a difference in shielding of the hydroxyl group. Greater shielding of the hydroxyl group results in a less asymmetric system, and this, in turn, results in higher solubility of the molecule.     

Partial oxidation kinetics of m-hydroxybenzyl alcohol with noble metal catalysts in supercritical carbon dioxide

Partial oxidation of m-hydroxybenzyl alcohol was studied over several supported noble metal catalysts in a temperature range from 373 to 413 K, up to 2 MPa of oxygen pressure and 20 MPa of carbon dioxide pressure. The major product detected was m-hydroxybenzaldehyde. A charcoal supported palladium catalyst gave the highest yield of the aldehyde. For high temperature above 393 K and high oxygen pressure above 0.5 MPa, total oxidation was observed, which caused the selectivity of m-hydroxybenzaldehyde to decrease. Supercritical carbon dioxide medium seemed to improve heat dissipation of the reaction to allow the partial oxidation of m-hydroxybenzyl alcohol to occur under mild conditions. The partial oxidation of benzyl alcohol over a charcoal supported palladium catalyst was also examined for comparison and the major product formed was benzaldehyde. The conversion of benzyl alcohol and the selectivity to benzaldehyde was higher than those for the case of partial oxidation of m-hydroxybenzyl alcohol.     

Phase equilibria of free fatty acids enriched vegetable oils and carbon dioxide: Experimental data,distribution coefficients and separation factors

In present work, the oils were treated by saponification procedure to release fatty acids from triglycerides to obtain free fatty acids (FFA) enriched oils and glycerol. Phase equilibria data for systems FFA enriched rapeseed oil–CO₂, FFA enriched corn germ oil–CO₂ and FFA enriched borage oil–CO₂ were determined at temperatures 35, 45, 65 and 85 °C, and in pressure range from 100 to 550 Bar. Experiments using FFA enriched oils were performed using high-pressure variable–volume view cell, where phase inversions were also observed at temperatures 35 and 45 °C. Samples from liquid and vapor phases were analyzed by gas chromatography for the content of free fatty acids, and based on obtained data; the distribution coefficients and the separation factors between FFA and glycerol were calculated.     

Determination and calculation for solubility of m-nitroaniline and its mixture in supercritical carbon dioxide

Equilibrium solubility of m-nitroaniline and p-nitroaniline in supercritical carbon dioxide (SCCO₂) is essential to design the process of SCCO₂ extraction and to investigate the effect of each solute on the solubility in SCCO₂ ternary system. However, the solubility data is not reported so far. We performed the solubility measurements at the temperatures of 308–328 K and in the pressure range of 11.0–21.0 MPa. The experimental results showed the solubility of m-nitroaniline and p-nitroaniline was enhanced in m-nitroaniline + p-nitroaniline + SCCO₂ ternary system. The improvement factor (i), separation factor (μ) and separation efficiency (HE) in the ternary system were defined and calculated, and the best separation result could be obtained at 21.0 MPa and 328 K using SCCO₂ extraction, where the separation efficiency was up to 90.9%. Based on the chemical association theory, a new model was developed to calculate the solubility of mixed solutes in SCCO₂. The correlation result of the new model was tested by about 500 solubility data from 15 kinds of two solutes mixtures in SCCO₂. The correlated result showed that the new model could achieve much better AARD (%) than those of frequently used Sovova and Sovova-T models.     

Solubility of non-ionic poly(fluorooxetane)-block-(ethylene oxide)-block-(fluorooxetane) surfactants in carbon dioxide

The impact of side chain and midblock length on the solubility of ABA triblock copolymers of fluorooxetane-(ethylene oxide)-fluorooxetane in carbon dioxide is examined. The use of short fluorinated side chains instead of long fluorinated chains prevents issues with bioaccumulation of the degradation products of the surfactant. At 40 °C for the same degree of polymerization, increasing the number of perfluoro-units from one to four results in a non-monotonic change in the cloud point pressure; the cloud point pressure decreases as the side chain is increased from perfluoromethyl to perfluoroethyl. However, further increasing the fluorinated side chain to perfluorobutyl results in a significant increase in the cloud point. However when the temperature is increased to 60 °C, the cloud point pressure for the surfactants with perfluoroethyl and perfluorobutyl side chains is statistically similar, while the perfluoromethyloxetane based surfactant requires a substantially larger pressure to obtain comparable solubility. An increase in cloud point pressure is observed when increasing the hydrophilic ethylene oxide segment. These results illustrate that commercially available fluorooxetane-(ethylene oxide)-fluorooxetane surfactants are highly soluble in CO₂.     

Calculation of the solid solubilities in supercritical carbon dioxide using a new G mixing rule

The aim of this study is to develop a new EOS/G^ex-type mixing rule with special attention to calculating the solid solubilities of aromatic hydrocarbons, aliphatic carboxylic acids, aromatic acids, and heavy aliphatic and aromatic alcohols in supercritical carbon dioxide. A volume correction term is applied with a combination of second and third virial coefficients which the equation for the third virial coefficient is quadratic, according to the suggestion by Hall and Iglesias-Silva. In this study, the cubic Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) equations of state have been used to calculate the solid solubilities of 23 solutes in supercritical CO₂, by using six mixing rules, namely, the Wong-Sandler (WS) rule, the Orbey-Sandler (OS) rule, the van der Waals one fluid rule with one (VDW1) and two (VDW2) adjustable parameters, the covolume dependent (CVD) rule and the new mixing rule. In all cases, the NRTL model was chosen as the excess Gibbs free energy model. The coefficients of the NRTL model and the binary interaction parameters of six mixing rules with two EOSs (PR and SRK EOSs) have been determined for 100 data sets of 23 binary systems over a wide range of temperatures and pressures covering more than 970 experimental data points which are reported in the literature. The results show that the PR EOS with the new mixing rule model is more accurate than the PR and SRK EOSs with the other mixing rules for solid solubility calculations in supercritical carbon dioxide.The regressed interaction parameters of the binary system, without any further modification, were then extended to four ternary mixtures, giving satisfactory results of the solid solubilities in supercritical CO₂.     

Determination and calculation of solubility of bisphenol A in supercritical carbon dioxide

Supercritical fluid technology (SFT) as a new technique is very important for clean environment and removal of chemical pollutants. The lack of solubility data of solid solute in certain supercritical fluid is a great obstacle to the successful implementation of SFT. In this work, the solubility of bisphenol A in supercritical carbon dioxide was determined by the dynamic method at the temperatures ranging from 308 to 328 K and pressure range of 11.0–21.0 MPa. The effects of temperature and pressure on solubility were analyzed according to molecular motion theory. The solubility data were correlated using eight different semi-empirical models (Chrastil, Adachi–Lu, Kumar–Johnston, Tang, Sung–Shim, Bartle, Méndez Santiago–Teja and Yu). The comparison between different models was discussed. The thermodynamic properties (total enthalpy ΔH, enthalpy of sublimation Δ_subH and enthalpy of solvation Δ_solvH) of the solid solute were obtained.     

Polymerization of acrylonitrile in supercritical carbon dioxide

A series of fluorinated diblock copolymers, consisting of styrene (St)-acrylonitrile (AN) copolymer [poly(St-co-AN)] and poly-2-[(perfluorononenyl)oxy]ethyl methacrylate, with various compositions as well as with different molecular weights were synthesized by atom transfer radical polymerization and characterized. Dispersion polymerization of acrylonitrile in supercritical carbon dioxide (scCO₂) at 30 MPa and at 65 °C with this kind of amphiphilic block copolymer as a stabilizer and 2,2′-azobisisobutyronitrile as an initiator was investigated. The experimental results indicated that, in the presence of a small amount of poly(St-co-AN) (5 wt% to AN), spherical particles of polyacrylonitrile (PAN) were prepared with small diameter and narrow polydispersity (d_n = 153 nm, d_w/d_n = 1.12), resulting from the high stabilizing efficiency of this fluorinated block copolymer. Furthermore, the polymerization of AN in scCO₂ under different initial pressures especially under low pressure (<14 MPa) was studied. When the polymerization was carried out around the critical pressure of CO₂ (7.7-7.8 MPa), the PANs with high molecular weight (M_ν ≈ 130,000-194,000) were synthesized at high monomer conversion (>90%) no matter whether the stabilizer was added, compared to those synthesized by dispersion polymerization at 30 MPa. It was also found that the crystallinity of PAN synthesized at 7.7-7.8 MPa was somewhat higher than that synthesized at 30 MPa, while its crystallite size did not change.     

Evaluation of density-based models for the solubility of solids in supercritical carbon dioxide and formulation of a new model

Many models have been developed to calculate supercritical solubility behavior and most can be either a semi-empirical relationship or based on an equation of state. In this work, density-based, semi-empirical models were evaluated in terms of their ability to accurately correlate solid solubility in supercritical carbon dioxide. The models considered were the methods of Chrastil, del Valle and Aguilera, Adachi and Lu, Méndez-Santiago and Teja, and Bartle. Six binary systems (solid + supercritical carbon dioxide), each with three isotherms, were selected for this evaluation. The average error was calculated for all 18 isotherms with each of the models evaluated. The solid compounds used in this study were naphthalene, anthracene, fluorene, hydroquinone, 1,5-naphthalenediamine, and cholesterol. The solubility data were obtained from literature. Of the previously mentioned models, the Adachi-Lu and del Valle-Aguilera equations provided, in general, lower average error than the other models. Since the Adachi-Lu equation and the del Valle-Aguilera equation correct for different effects, a new model is proposed in this work as a combination of the previous two methods. The proposed equation provided the least overall average error compared to all other models considered in this study. The new model is particularly useful when the reduced density of the solvent is below 1 where previous models tend to fail. This work also emphasizes on the advantages of expressing density-based models in dimensionless form to avoid dimensional inconsistencies in Chrastil-type models. One of the benefits, for example, is that parameters obtained by different authors can be readily compared, regardless of the units used.