Separation of Mixtures of Polar and Nonpolar Organic Liquids by Pervaporation and Nanofiltration (Review)
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ration of Mixtures of Polar and Nonpolar Organic Liquids by Pervaporation and Nanofiltration (Review) A. A. Yushkina, G. S. Golubeva, I. A. Podtynnikova, I. L. Borisova, V. V. Volkova, and A. V. Volkova, * a
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received May 12, 2020; revised July 12, 2020; accepted July 14, 2020
Abstract—The review summarizes the accumulated scientific results on the separation of mixtures of organic solvents by pervaporation and reverse osmosis. It has been shown that the pervaporation process makes it possible to achieve generally higher selectivity as compared to the reverse osmosis process; however, a number of developments, such as membranes from polyketone or PIM-1, make it possible to effectively separate components with similar molecular weights. Such membranes allow the main advantage of reverse osmosis— lower energy consumption due to the absence of phase transitions—to be gained. It is noted that with the use of reverse osmosis membranes, the highest efficiency can be achieved in the case of separation of mixtures of organic liquids that differ significantly in their polarity, a process that is especially important for the regeneration of polar extractants in the petrochemical industry. Keywords: pervaporation, nanofiltration, reverse osmosis, membrane separation processes DOI: 10.1134/S0965544120110201
The separation of organic mixtures for the production of solvents is an important task for the chemical industry. Thus, the volume of production of aromatic hydrocarbons (HCs) and, first of all, benzene, toluene, and xylenes (BTX fraction) accounts for almost a quarter of the world’s petrochemical products. The main processes for producing BTX are catalytic reforming of crude oil (68%), pyrolysis of oil fractions (29%), and coking of coal (3%) [1, 2]. The composition of liquid products of catalytic reforming and pyrolysis depends on the feedstock and process conditions. The mixtures consist of nonpolar hydrocarbons: arenes, alkanes, cycloalkanes, and alkenes impurities. The BTX components have similar boiling points with some cycloalkanes and alkanes, forming azeotropic mixtures with them; therefore, separation of the reforming catalyzate by distillation is ineffective and extraction methods are used to separate the products. Industrial polar solvents such as glycols, sulfolane, dimethyl sulfoxide, N-methylpyrrolidone are used as extractants. Further, the extractant is separated from the product by distillation. For effective recovery of the polar solvent from the extract by distillation, a significant difference between the boiling points of the extractant and the product is required. At the same time, distillation is a very energy-intensive process, which accounts for up to 15% of world energy consumption [3]. Extraction methods in this case also often include a distillation step at the solvent recovery stage.
Membrane processes, such as pervaporation or filtration, can be an alternative to extract
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