Oliver Pfohl

Phase equilibria in systems containing o-cresol, p-cresol, carbon dioxide, and ethanol at 323.15–473.15 K and 10–35 MPa

Abstract Phase equilibria in binary and ternary systems containing o -cresol, p -cresol, carbon dioxide, and ethanol have been investigated experimentally at temperatures between 323.15 K and 473.15 K and pressures ranging from 10 MPa to 35 MPa. The experimental results provide a systematic basis of phase equilibrium data, yielding the effect of temperature on the influence of the position of the methyl groups of cresols that are in phase equilibria with carbon dioxide. Based on the different solubilities of the cresol isomers in carbon dioxide, the separation of o -cresol and p -cresol was investigated. The dependence of the separation factor between both cresol isomers on concentration, temperature, and pressure is obtained from experiments in the ternary system, o -cresol+ p -cresol+carbon dioxide. The influence of ethanol added to each of the binary systems, cresol isomer+carbon dioxide, in order to enhance the solubility of the cresols in the carbon dioxide-rich phase is also shown. The experimental data have been correlated using seven different equations of state, whereof four explicitly account for intermolecular association: Statistical Association Fluid Theory (SAFT) by Chapman, Gubbins, Huang and Radosz, the SAFT modification by Pfohl and Brunner for near-critical fluids, a modified cubic-plus-association equation of state (CPA EOS) according to the ideas by Tassios et al., and one of the EOS by Anderko. The mixing rule proposed by Mathias, Klotz, and Prausnitz, with two binary interaction parameters per binary system influencing intermolecular attractive forces, is used for all EOS as a basis for an objective comparison of the EOS.

Thermophysical properties—Industrial directions

Changing conditions in the companies have necessarily led to changes in the work in thermodynamics groups in industry during the last 20 years. While many companies have reduced activities in the field of applied thermodynamics or even have closed their thermodynamics group, other companies, including Bayer, have put more emphasis in the field of applied thermodynamics. Here, ten industrial directions in the field of applied thermophysical properties are discussed. It is shown, where and when expertise in applied thermodynamics within the company is needed. At Bayer, this expertise can be delivered most efficiently by a group of thermodynamicists who use either internal sources, e.g. a laboratory, a database or estimation methods, or coordinate and supervise the use of external sources.

Two- and three-phase equilibria in systems containing benzene derivatives, carbon dioxide, and water at 373.15 K and 10–30 MPa

Abstract Phase equilibria in binary and ternary systems containing benzene derivatives, carbon dioxide, and water have been investigated experimentally at a temperature of 373.15 K and pressures ranging from 10 to 30 MPa. The experimental results and literature data for further systems in cluding benzene derivatives, carbon dioxide, and water provide a basis of experimental phase equilibrium data, clearly showing the influence of the number and the position of methyl and hydroxy groups of benzene derivatives that are in phase equilibria with carbon dioxide and water. The experimental data have been correlated using the equations of state by Peng and Robinson [D.-Y. Peng, D.B. Robinson, A new two-constant equation of state, Ind. Eng. Chem., Fundam., 15 (1976) 59–64] and Yu and Lu [J.-M. Yu, B.C.-Y. Lu, A three-parameter cubic equation of state for asymmetric mixture density calculations, Fluid Phase Equilibria, 34 (1987) 1–19] with the mixing rule proposed by Mathias et al. [P.M. Mathias, H.C. Klotz, J.M. Prausnitz, Equation-of-State mixing rules for multicomponent mixtures: The problem of invariance, Fluid Phase Equilibria, 67 (1991) 31–44]. The phase behavior of ternary systems determined experimentally, can be predicted well, using two binary interaction parameters per binary system, optimized to reproduce the phase equilibria of the binary subsystems.

Measurement and correlation of vapor-liquid-liquid equilibria in the glucose + acetone + water + carbon dioxide system

Abstract Phase equilibria in the glucose + acetone + water + carbon dioxide system have been investigated experimentally in the three-phase region at temperatures of 313, 323, and 333 K and pressures of 4, 6, and 8 MPa. The experimental method was checked by measuring phase equilibria in the binary and ternary subsystems acetone + carbon dioxide and acetone + water + carbon dioxide and comparing the results with literature data. The experimental data for the quaternary system have been correlated using the Soave-Redlich-Kwong equation of state (EOS) with the mixing rule proposed by Mathias, Klotz and Prausnitz (1991). The binary interaction parameters for the binary subsystems without glucose have been regressed from phase equilibria of the binary subsystems, and the interaction parameters for glucose have been regressed from the glucose K-factors determined in the quaternary system investigated. With these interaction parameters the extent of the three-phase region can be well predicted and the partioning of glucose between the three phases can be reproduced.

Partitioning of carbohydrates in the vapor-liquid-liquid region of the 2-propanol + water + carbon dioxide system

Abstract Partitioning of five carbohydrates in the vapor-liquid-liquid region of the 2-propanol + water + carbon dioxide system has been investigated experimentally. Phase compositions of all three coexisting phases have been determined at temperatures between 325 and 343 K and pressures between 9 and 13 MPa. The experimental method was checked by measuring vapor-liquid-liquid equilibria (VLLE) in the ternary subsystem 2-propanol + water + carbon dioxide and by comparing the results with the literature. In contrast to recently published experimental data of VLLE in the glucose + acetone + water + carbon dioxide system, adding carbohydrates to the 2-propanol + water + carbon dioxide system causes a significant extension of the VLLE region to lower pressures. With increasing pressure at constant temperature and decreasing temperature at constant pressure, the composition of the middle phase becomes more similar to the composition of the gas phase. Simultaneously, the capacity of the middle phase for carbohydrates decreases and the selectivity for different carbohydrates increases.

PE — a Scientific Computer Program for the Calculation of Fluid-Phase Equilibria

The calculation of phase equilibria may serve as a cheap alternative compared to the measurement of phase equilibria. This is especially true for high pressure where the necessary equipment to measure phase equilibria is more expensive than at low pressure. The calculation may often serve as a fast alternative compared to measurements, also. The program PE (= Phase Equilibria) has been developed for modeling phase equilibria with equations of state (EOS) [1,2]. PE offers more than 40 different EOS, allowing the user to choose the one which best fits his needs. PE also offers powerful routines to determine adjustable EOS pure-component and mixture parameters by correlating experimental data and subroutines to use these parameters for predictions at conditions not investigated experimentally, yet.

Partitioning of carbohydrates in the three-phase region of systems containing carbon dioxide, water and a modifier at high pressure

Publisher Summary This chapter examines the partitioning of carbohydrates in the vapor–liquid–liquid (VLL) regions of the acetone+water+carbondioxide system and the 2-propanol+water+carbon dioxide system experimentally between 313 and 343 K and between 4 and 13 MPa. Both series yields the same qualitative results. Partitioning of the carbohydrates between the two liquid phases of the vapor–liquid–liquid equilibria (VLLE) shows the dependencies of the carbohydrate K-factors on pressure and temperature. The carbohydrate solubility in a phase rises when the phase becomes more similar to the water-rich lower liquid phase. At the same time, the separation of different carbohydrates becomes more difficult because selectivity decreases. Theoretically based models can help to find an optimum of capacity and selectivity and to minimize the number of necessary experiments. The Soave–Redlich–Kwong equation of state is suitable to reproduce carbohydrate partitioning in the glucose+acetone+water+carbon dioxide system.