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Vapor–liquid equilibrium (VLE) and vapor–liquid–liquid equilibrium (VLLE) data were measured for the ethanol/diisopropyl ether (DIPE)/water, n-propanol/DIPE/water, and n-propanol/2,2,4-trimethylpentane (isooctane)/water systems at 101.3 kPa. The data were carefully measured in a Guillespie type still, equipped with an ultrasonic homogenizer. The VLE data were found to be thermodynamically consistent, and the LLE part of the VLLE data followed a regular profile according to the Othmer–Tobias correlation. VLLE were observed in the temperature ranges of (334.19 to 336.29) K, (335.31 to 345.76) K, and (347.74 to 352.31) K for the ethanol/DIPE/water, n-propanol/DIPE/water, and n-propanol/isooctane/water systems, respectively. These VLLE regions encompassed wide ranges for water and entrainer composition, with alcohol mole fractions of up to approximately 0.4. The ethanol/DIPE/water and n-propanol/isooctane/water systems displayed ternary heterogeneous azeotropes at (334.19 and 347.74) K, respectively. However, no ternary heterogeneous azeotrope was found for the n-propanol/DIPE/water system. The measured data were subsequently modeled in Aspen Plus with the nonrandom two-liquid (NRTL), universal functional UNIFAC(VLE), UNIFAC(LLE), and universal quasichemical UNIQUAC activity coefficient models, applying the default regression parameters built into Aspen Plus. UNIFAC(VLE) predicted the ethanol/DIPE/water system most accurately, while UNIQUAC performed the best for the n-propanol/DIPE/water. However, none of these models could predict the n-propanol/isooctane/water system with acceptable accuracy. The results of this study strongly support proposals that DIPE or di-n-propyl ether (DNPE) could be used as effective entrainers for alcohol dehydration, replacing the more traditional entrainers like benzene and cyclohexane.

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A new association scheme for sPC-SAFT, denoted as 2C, is presented for more-accurate predictions of 1-alcohol/water phase equilibria than with the 2B or 3B association schemes. This 2C association scheme consists of one bipolar association site and one negative electron donor site and is a combination of the 1A and 2B/3B association schemes. The performance of the 2C scheme is evaluated and compared to the 2B and 3B schemes by modeling the vapor–liquid equilibria and liquid–liquid equilibria of alcohol/water, alcohol/alcohol and alcohol/alkane mixtures. Liquid–liquid equilibria of multicomponent systems are also considered. Compared to sPC-SAFT with the 2B or 3B schemes, sPC-SAFT-2C provides improved phase equilibria predictions for the investigated alcohol/water vapor–liquid systems, as well as for liquid–liquid equilibria of water/alcohol/alkane and water/alcohol/alcohol ternary systems. However, a slight deterioration in the prediction of binary alcohol/alkane phase equilibria is observed with the 2C scheme, compared to the 2B scheme. Furthermore, related VLE predictions with sPC-SAFT-2C compare well to predictions with the Cubic-Plus-Association (CPA) equation of state.

During the last 30 years, there has been a great evolution in p-xylene production technology, with many equipment improvements being instituted in the industry. Typically, these improvements bring economic as well as processing advantages to the producers. Such developments are vital, as the capital costs for process equipment to separate xylene isomers, especially into highly purified p-xylene, still remain very high. In view of this, research efforts have recently focused on the development of zeolite membranes for the separation and production of p-xylene, the precursor for the production of terephthalic acid, for which the current p-xylene world demand stands at about 86% of the production. Over a list of about 200 references, this review reports on the present state-of-the-art in p-xylene separation from lesser used isomers (o-and m-xylene) by means of MFI-type zeolite membranes, and on the most recent achievements in o/m-xylene isomerization to p-xylene using extractor-type catalytic membrane reactors.  2009