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A generalized two parameter model is presented which uses molecular properties of pure fluids to predict interaction parameters in the attractive term of the Peng-Robinson equation of state. The predictive method is based on a consideration of London (dispersive) forces and includes attractive forces between polar and non-polar molecules that result from induction. Polar-polar effects and quantum forces are omitted. A large body of experimental vapor-liquid equilibrium data measured at near and supercritical conditions (that excludes quantum components and polar-polar systems) was used to calibrate the generalized model. Overall bubble point pressure deviations calculated using the proposed generalization were 5.66% for 3240 data points which compares to average deviations of 3.27% obtained by using regressed binary interaction parameters. Average vapor mole fraction deviations were just under 0.01 using both the generalized and the regressed interaction parameters. The sensitivity of predicted phase envelopes to dispersive and inductive term in the generalized correlation is shown graphically for several systems. Comparisons are also made to another recent interaction parameter generalization presented by Nishiumi et al. (1988). 相似文献
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Vapor-liquid phase equilibrium data including composition, densities, molar volume and equilibrium constant of isobutanol in supercritical carbon dioxide from 313.2 K to 353.2 K were measured in a variable-volume visual cell. The properties of critical point were obtained by extrapolation. The results showed that critical temperature, critical pressure and critical compressibility factor of CO2-isobutanol system decreased with the increase of critical CO2 content. The phase equilibrium model was established by Peng-Robinson equation of state and van der Waals-2 mixing regulation, and model parameters were determined by optimization calculation of nonlinear least square method. The correlation between calculated values and the experimental data showed good agreement. 相似文献
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超临界状态下的CO2在含有有机溶剂的水溶液中可作为萃取剂。这种情况可用于水和有机酸的分离,也可以用于从水溶液中萃取产品。要设计这样的过程,CO2-H2O-有机酸系统相平衡的数据是必不可少的。为此,在实验室建立了一套高压相平衡装置。为了验证这套装置的可靠性,测定了CO2-H2O-HAc体系在313K以及压力在15、20、25和30MPa下的相平衡数据,用Peng-Robinson方程^[1,2]进行了计算,并与文献值进行了比较。 相似文献
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Yang Su Zihao Wang Saimeng Jin Weifeng Shen Jingzheng Ren Mario R. Eden 《American Institute of Chemical Engineers》2019,65(9):e16678
Deep learning rapidly promotes many fields with successful stories in natural language processing. An architecture of deep neural network (DNN) combining tree-structured long short-term memory (Tree-LSTM) network and back-propagation neural network (BPNN) is developed for predicting physical properties. Inspired by the natural language processing in artificial intelligence, we first developed a strategy for data preparation including encoding molecules with canonical molecular signatures and vectorizing bond-substrings by an embedding algorithm. Then, the dynamic neural network named Tree-LSTM is employed to depict molecular tree data-structures while the BPNN is used to correlate properties. To evaluate the performance of proposed DNN, the critical properties of nearly 1,800 compounds are employed for training and testing the DNN models. As compared with classical group contribution methods, it can be demonstrated that the learned DNN models are able to provide more accurate prediction and cover more diverse molecular structures without considering frequencies of substructures. 相似文献
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Cloud‐point data between 40 and 240°C and pressures to 2750 bar are presented for a low molecular weight, semicrystalline polyester resin of 53.4 mol % adipic acid and 46.6 mol % 1,4‐cyclohexanedimethanol in supercritical CO2, dimethyl ether (DME), and chlorodifluoromethane (CDFM), and in mixtures of CO2 with DME, CDFM, methanol, ethanol, butanol, octanol, hexafluoroisopropanol, acetone, and cyclohexane. Carbon dioxide, by itself, is an extremely weak supercritical fluid (SCF) solvent because this polyester only dissolves at pressures in excess of 2000 bar and at temperatures over 180°C. However, DME and CDFM are excellent solvents for this polyester, which dissolves at 16 bar and 40°C in CDFM and at 167 bar and 55°C in DME. The melting point of this polyester is reduced from 105 to 40°C in CDFM and to 55°C in DME, which makes the polyester amenable to high intensity mixing for the efficient dispersion of inorganics or crosslinking agents and other hard to deposit materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2642–2648, 2001 相似文献
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超临界流体萃取中的相平衡研究 总被引:2,自引:0,他引:2
本文综述了超临界流体萃取过程中的相平衡模型及其实验研究的新进展,特别着重介绍了压缩气体模型,膨胀液体模型,经验模型和计算机模拟模型,研究体系包括液体/SCF,固体/SCF,固体/SCF/夹带剂体系。 相似文献
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Cloud point curves for several narrow fractions of polystyrene dissolved in cycloheptane, in cyclooctane and in cyclodecane have been established, and the critical solution temperatures extrapolated to give the respective temperatures. All three cycloalkanes are good solvents for the polymer. A comparison is made between the phase behaviour of polystyrene dissolved in cyclic alkanes and in n-alkanes using free volume polymer solution theory. 相似文献
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J. Gregorowicz Z. Fra? G. Rokicki S. Dziewulski 《The Journal of Supercritical Fluids》2010,55(2):786-796
Hyperbranched polyethers and polyesters have been synthesized, and their phase behaviour in carbon dioxide and light hydrocarbons explored as a function of concentration and temperature. The synthesis includes modifications of the terminal OH groups with aliphatic carboxylic acids derivatives, trimethylchlorosilane, and trifluoroacetic acid anhydride. Modified polyesters show good solubility in carbon dioxide, ethane and propane. The comparison with the literature data shows that the silane and fluorinated derivatives of the hyperbranched polyesters are soluble in carbon dioxide to the same extent as the most CO2-philic polymeric materials synthesized till now. It seems that the nature of the end groups is an important factor that influences phase equilibria of hyperbranched macromolecules in supercritical solvents. However, the nature of the interior of the macromolecule is also significant. The results obtained show that in general hyperbranched polyesters are better soluble in carbon dioxide than hyperbranched polyethers. In light hydrocarbons as solvents the opposite effect is observed. 相似文献
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Maja Habulin
eljko Knez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2001,76(12):1260-1266
The stability and activity of lipases from Pseudomonas fluorescens, Rhizopus javanicus, Rhizopus niveus, porcine pancreas and Candida rugosa in a non‐solvent system at atmospheric pressure, in supercritical carbon dioxide (SC CO2), and near‐critical propane at 100 bar and 40 °C were studied. Esterification of n‐butyric acid with ethanol and isoamyl alcohol was used as a model system. In supercritical carbon dioxide there was a great loss in activity of the examined lipases. Decreased relative activity of lipases in SC CO2 was attributed to the interactions between CO2 and the enzyme. The second reason for this effect was the differences in water partitioning between the enzyme and its surroundings. In contrast, the use of near‐critical propane improved the activity of lipases in the comparison to the non‐solvent system by four‐ (porcine pancreas lipase) to nine‐times (Rhizopus javanicus lipase). The use of near‐critical propane also improved the thermal stability of porcine pancreas lipase compared with the non‐solvent system. The calculated deactivation constant for esterification between butyric acid and isoamyl alcohol, catalyzed by porcine pancreas lipase, showed that there was more than twice as much inactive as active enzyme in the non‐solvent system studied whereas the ratio in propane was 1. © 2001 Society of Chemical Industry 相似文献
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Sh. Jafari Nejad R. Mohammadikhah H. Abolghasemi M. A. Moosavian M. G. Maragheh 《加拿大化工杂志》2009,87(6):930-938
Solubility data of organophosphorous metal extractants in supercritical fluids (SCF) are crucial for designing metal extraction processes. We have developed a new equation of state (EOS) based on virial equation including an untypical parameter as BP/RT, reduced temperature and pressure for prediction of solute solubility in supercritical carbon dioxide (SC CO2). Solubility experimental data (solubility of tributylphosphate in SC CO2) were correlated with the two cubic equations of state (EOS) models, namely the Peng–Robinson EOS (PR‐EOS) and the Soave–Redlich–Kwong EOS (SRK‐EOS), together with two adjustable parameter van der Waals mixing and combining rules and our proposed EOS. The AARD of our EOS is significantly lower than that obtained from the other EOS models. The proposed EOS presented more accurate correlation for solubility data in SC CO2. It can be employed to speed up the process of SCF applications in industry. 相似文献
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《Ceramics International》2023,49(8):12166-12172
Digital light processing is a vital additive manufacturing technology used for manufacturing ceramic parts. The particle size distribution of ceramic suspensions significantly affects the cure behaviour and mechanical properties of ceramics. In this study, the cure behaviour and mechanical properties of Si3N4 ceramics with a bimodal particle size distribution were studied. The results indicated that the suspension with coarse particles had a higher cure depth for a lower absorbance but poor mechanical properties. The bending strength of the samples with the optimal ratio (coarse:fine particles = 3:7) reached a maximum of 728.7 ± 10.33 MPa, which is 16.5% higher than that of the samples prepared using only fine particles. 相似文献
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Atul Kumar Varma 《Fuel》2002,81(10):1321-1334
The coal quality, temperature, pressure, heating rate, various processes and reactor type affect coking behaviour of coal and resulting coke properties. Several petrographic and chemical methods were proposed earlier for prediction of coking behaviour of coals. Inertinite rich coal samples (Immf>30 vol%) having different petrographic compositions were selected for thermogravimetric investigations (DTA, DTG and TGA) and their coking behaviour was studied. The petrographic build up, micro-structural properties (porosity and cell wall thickness) and mechanical strength of the resulted cokes were also investigated. ΔH and ΔHmax (the main endothermic area of heat absorption and fast absorbing main endothermic area, respectively) were distinguished in DTA curves. ΔA and ΔAmax (the main decomposition area and fast disintegrating main decomposition area) under DTG curves were identified. ΔHmax/ΔAmax shows good correlation with Roga's indices (RI, caking properties) as well as with petrographic caking ratio (PCR). The coarse mosaic content of cokes seem to depend on LΔTmax/ΔTmax (ratio of weight loss during fast decomposing main reaction to temperature difference) under DTG. LmΔT/ΔT (ratio of weight loss during main decomposing reaction to temperature difference) under DTG exhibits correlation with p1 (mean pore size) and t1 (mean cell wall thickness) of cokes. ΔAmax/(LmΔTmax) also indicates good relationship with mechanical strength of cokes. (LmΔTA−TB)/(LmΔT) (i.e. ratio of weight loss during main endothermic reaction under DTA to weight loss during main decomposing reaction) appears to have relationship with DD (compactness) of cokes. The course of main endothermic reaction/main decomposition reaction under DTA, DTG and TGA seems to govern coking behaviour and the resulting coke strength, which in turn is controlled by microlithotypes. 相似文献
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The demixing behaviour of polystyrene fractions in binary combinations of acetone (1) and a series of n-alkanes (2) containing up to twenty carbon atoms has been established and the data presented as phase contour diagrams. Each binary liquid system exhibits the characteristics of classic cosolvency and the maximum molecular weight of polymer that may be dissolved is ca. 106 gmol?1 in combinations of acetone and tridecane. The shapes of the phase contour diagrams can be related to the solvent behaviour of the n-alkane used towards polystyrene, although cosolvent action is not a simple linear function of the mixture composition. 相似文献
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Miscibility conditions and volumetric properties of solutions of poly(dimethylsiloxane) in supercritical carbon dioxide have been determined as a function of polymer molecular weight, polymer concentration, temperature, and pressure. Measurements have been conducted in a variable volume view cell equipped with an LVDT sensor to identify the position of a movable piston and thus the internal volume of the cell and consequently the density of the solution at a given pressure and temperature. The demixing data (in the form of P‐T curves for a given concentration, or as P‐x diagrams at a given T) and the density isotherms are presented for solutions of two polymer samples with different molecular weights (Mw = 38,600; Mw/Mn = 2.84 and Mw = 94,300; Mw/Mn = 3.01) at several concentrations in the range from 0.05 to 10 mass % over a temperature range from 302–425 K. Solution densities corresponding to the demixing points also have been identified. Representation of the demixing densities on the density isotherms, i.e., pressure‐density plots is a new methodology that gives a direct assessment of the volumetric expansion the solution must undergo before phase separation. The temperature–composition diagrams generated at selected pressures show that the poly(dimethylsiloxane) + CO2 solutions display both lower critical solution and upper critical solution type behavior. The lower critical solution temperature moves to lower temperatures and the upper critical solution temperature moves to higher temperatures with decreasing pressure and they eventually merge together at lower pressures forming an hourglass‐shaped region of immiscibility. This behavior is linked to the solvent quality of supercritical carbon dioxide that changes with pressure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1397–1403, 2000 相似文献
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Dispersed Phase Holdup in a Tall and Low Plate Free Area Liquid Pulsed Sieve-Plate Extraction Column
《分离科学与技术》2012,47(1):175-182
Dispersed phase holdup is studied in a tall and low plate free area pulsed sieve-plate extraction column. The 5.0 cm internal diameter column consists of 80 number of plates with percent free area of 13.5. The effects of pulse velocity (product of amplitude and frequency), superficial phase velocities, and solute addition are studied for five liquid-liquid systems with a wide range of interfacial tensions. The experimental holdup data is tested against the most widely recommended correlations and a new correlation has been developed that best fits the data. 相似文献