Multi-fluid Nonrandom Lattice Fluid Research Articles

High pressure phase behavior for the binary mixture of pentafluoropropyl methacrylate and poly(pentafluoropropyl methacrylate) in supercritical carbon dioxide and dimethyl ether

Pressure-composition isotherm is obtained for the carbon dioxide+2,2,3,3,3-pentafluoropropyl methacrylate (PFPMA) using static apparatus with a variable volume view cell at temperature range from 40 °C to 120 °C and pressure up to 130 bar. This system exhibits type-I phase behavior with a continuous mixture-critical curve. The experimental result for carbon dioxide+PFPMA mixture was modeled using the Peng-Robinson (P-R) and multi-fluid nonrandom lattice fluid (MF-NLF) equation of state. Experimental cloud-point data of pressure up 470 bar and temperature to 182 °C were reported for the binary mixture of poly(2,2,3,3,3-pentafluoropropyl methacrylate) [Poly(PFPMA)] in supercritical carbon dioxide and dimethyl ether (DME). The Poly(PFPMA)+carbon dioxide and Poly(PFPMA)+DME systems showed LCST behavior.

A crossover multi-fluid nonrandom lattice fluid model for pure hydrocarbons and carbon dioxide near to and far from the critical region

The multi-fluid nonrandom lattice fluid model with the local composition concept is capable of describing thermodynamic properties for complex systems, but this model cannot represent the singular behavior of fluids near the critical region. In this research, the multi-fluid nonrandom lattice fluid model for pure fluids is combined with a crossover theory to obtain a crossover multi-fluid nonrandom lattice fluid model which incorporates the critical scaling laws valid asymptotically close to the critical point and reduces to the original classical multi-fluid nonrandom model far from the critical point. The crossover multi-fluid nonrandom lattice fluid model shows a great improvement in prediction of the thermodynamic properties of pure compounds near the critical region.

A multi-fluid nonrandom lattice fluid model for mixtures containing nonionic surfactants

Surfactant systems show highly non-ideal phase behavior because of the inter-association and intra-association hydrogen bond. We present a lattice fluid equation of state that combines the multi-fluid nonrandom lattice fluid model with modified Veytsman statistics for intra+inter molecular association to calculate phase behavior for mixture containing surfactant systems. The literatureresults fitted to this model show good accordance for mixtures containing nonionic surfactant systems.

Measurement and correlation of (vapor + liquid) equilibria for the {2-propoxyethanol (C 3E 1) + n-hexane} and the {2-propoxyethanol (C 3E 1) + n-heptane} systems

2-Propoxyethanol (C 3E 1) is one of nonionic surfactants which are a particularly interesting class of substances due to both inter-molecular and intra-molecular association. Binary (vapor + liquid) equilibrium data were measured for {2-propoxyethanol (C 3E 1) + n-hexane} and {2-propoxyethanol (C 3E 1) + n-heptane} systems at temperatures ranging from (303.15 to 323.15) K. A static apparatus was used in this study. The experimental data were correlated well with a lattice fluid equation of state that combines the multi-fluid non-random lattice fluid model with Veytsman statistics for (intra + inter)-molecular association.

A multi-fluid nonrandom associating lattice fluid model

A lattice fluid theory valid from pure fluids to multi-component mixtures of molecules having any number of associating donor and acceptor groups formulated. Under the fundamental assumption that the intermolecular forces are divided into physical and chemical forces, the Veytsman statistics for associating contribution was combined with the multi-fluid nonrandom lattice fluid (MLF) equation of state developed recently by the present authors. The physical contribution is characterized by temperature independent molecular parameters representing close packed volumes of a mer, segment numbers and energy parameters of a pure fluid, and a binary interaction parameter for a binary mixture. The chemical part is represented by internal energy and entropy of associating system. The resulting multi-fluid nonrandom associating lattice fluid (MALF) equation of state was applied to describe thermodynamic properties of pure fluids and phase equilibrium of mixtures. The results for alkane–alcohol and alcohol–alcohol mixtures were found satisfactory for most systems when compared with the MLF and the statistical associating fluid theory (SAFT) model.

A multi-fluid nonrandom lattice fluid model: General derivation and application to pure fluids

A multi-fluid nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers and energy parameters of pure systems is presented. The multi-fluid nonrandom lattice fluid (MF-NLF) model with the local composition concept was capable of describing properties for complex systems. However, the MF-NLF model has strong temperature dependence of energy parameters and segment numbers of pure systems; thus empirical correlations as functions of temperature were represented for reliable and convenient use in engineering practices. The MF-NLF model without temperature dependence of pure parameters could not predict thermodynamic properties accurately. It was found that the present model with three parameters describes quantitatively the vapor pressure and the saturated density for the pure fluid.

A multi-fluid nonrandom lattice fluid model: Mixtures

A multi-fluid nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers and energy parameters of pure systems and its consistent method for phase equilibrium calculation were presented in the previous paper. In this work, the model was extended to mixtures by using consistent method for phase equilibrium calculation with fugacity coefficients derived from the present equation of state and it was applied to vapor-liquid equilibrium. We consistently tested the present model on 17 phase equilibrium data sets of vapor-liquid equilibria and compared it with the MF-NLF model and the SAFT model. The present model (3 pure parameters for pure component and one binary interaction parameter) showed better results for most systems than the MF-NLF model (6 adjustable pure parameters and one binary interaction parameter) and the SAFT model (3 pure parameters and one binary interaction parameter).

Measurement and correlation of vapor-liquid equilibria of the binary carbon dioxide-chloroform mixture system

Binary vapor liquid equilibrium data of the carbon dioxide+chloroform system were measured at five isotherms from 310.13 K to 333.32 K. A circulating type apparatus with on-line gas chromatography was used in this study. The experimental data were correlated by classical Peng-Robinson equation of state using van der Waals one fluid mixing rules and the multi-fluid nonrandom lattice fluid (MF-NLF) equation of state.

Vapor–liquid equilibria for the system 1-propanol+n-hexane near the critical region

Vapor–liquid equilibria and critical point data for the system 1-propanol+n-hexane at 483.15, 493.15, 503.15 and 513.15K are reported. The critical pressures determined from the critical opalescence of the mixture were compared with published data for the system 2-propanol+n-hexane. Phase behavior measurements were made in a modified circulating type apparatus with a view cell. These mixtures are highly nonideal because of the hydrogen bonding of 1-propanol. Modeling of the experimental data has been performed using the multi-fluid nonrandom lattice fluid with hydrogen-bonding (MF-NLF-HB) equation of state and the Peng–Robinson–Stryjek–Vera (PRSV) equation of state with Wong–Sandler mixing rule. The critical points and the critical locus were also calculated.

A multi-fluid nonrandom lattice fluid theory for thermodynamic properties of hydrogen bonding fluids

A unified equation of state theory valid from pure fluids to multicomponent associated mixtures of molecules having any number of hydrogen (proton) donor and acceptor groups was formulated. Under the fundamental assumption that the intermolecular forces are divided into physical and chemical forces, generalized Veytsman's statistics for hydrogen bonding theory was combined with the nonrandom lattice-fluid theory. By the two-fluid approximation, configurational Helmholtz free energy was derived from the lattice of the Guggenheim combinatory. The Veytsman's statistics extended for dimers and n-mers was employed for the description of some associating systems including organic acid.

Measurements and correlation of hydrogen-bonding vapor sorption equilibrium data of binary polymer solutions

Vapor sorption equilibrium data of ten binary polymer/solvent systems were measured using sorption equilibrium cell equipped with a vacuum electromicrobalance. Tested solvents were water, methanol, ethanol and npropanol and polymer solutes were poly(ethylene glycol), poly(propylene glycol), poly(tetramethylene glycol) and poly(ethylene oxide). The measured sorption obtained in the present work, were compared with existing literature data and the degree of reliability of the measured data was discussed. Vapor sorption equilibrium data obtained in the present study were correlated by UNIQUAC model and the multi-fluid non-random lattice fluid hydrogen bonding equation of state (MF-NLF-HB EOS) recently proposed by the present authors.

Phase behavior of water + hydrocarbon binary systems by using multi-fluid nonrandom lattice hydrogen bonding theory

A simple lattice hydrogen bonding theory for water+hydrocarbon systems is formulated. The theory is derived under the assumption that the intermolecular forces are divided into physical and chemical parts. Veytsman’s statistics for the hydrogen bonding (HB) contribution is combined with the multi-fluid nonrandom lattice–fluid (MF-NLF) model previously developed by the present authors. The present MF-NLF-HB theory contains two molecular parameters representing molecular size and energy, and one additional interaction parameter for binary systems. The model is applied to quantitatively describe the thermodynamic properties of complex binary systems containing water and hydrocarbon.

Measurements and correlation of high-pressure VLE of binary CO 2–alcohol systems (methanol, ethanol, 2-methoxyethanol and 2-ethoxyethanol)

High-pressure vapor–liquid equilibrium (VLE) data were measured for binary CO 2–alcohol systems (e.g. methanol, ethanol, 2-methoxyethanol, and 2-ethoxyethanol) at various isotherms (313.15–345.15 K). The quantitative VLE data and mixture critical conditions were measured using a new design for a circulation VLE system. The measure data were correlated by the classical Peng–Robinson and the multi-fluid nonrandom lattice fluid hydrogen-bonding (MF-NLF-HB) equation of state. The MF-NLF-HB model was formulated previously by the present authors based on the proton donor–acceptor principle to the hydrogen-bonding interaction in CO 2–alcohol systems. For the measured and calculated data of CO 2–alcohol systems, the relative accuracy of the data was discussed.

Phase behavior measurement of the binary carbon dioxide– N, N-dimethylacetamide and carbon dioxide– N, N-diethylacetamide systems at high pressure

Pressure-composition isotherms are obtained for the carbon dioxide– N, N-dimethylacetamide ( N, N-DMA) and for the carbon dioxide– N, N-diethylacetamide ( N, N-DEA) systems at 40, 60, 80, and 100°C. These two carbon dioxide–polar solute systems have continuous critical mixture curves that exhibit maximums in pressure at temperatures between the critical temperatures of carbon dioxide and N, N-DMA or N, N-DEA. The experimental data are modeled using the multi-fluid-nonrandom lattice fluid (MF-NLF) equation of state. The coefficient of energy and volume parameters for each pure N, N-DMA or N, N-DEA is determined from a fit of the vapor pressure curve and saturated liquid densities. A good fit of the data is obtained with the MF-NLF equation using one adjustable mixture parameter that is temperature-independent, for the carbon dioxide– N, N-DMA and carbon dioxide– N, N-DEA systems.