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A low-energy separation process combining distillation and membrane vapor permeation is introduced as an alternative to conventional distillation. The process can be applied to any liquid mixture for which appropriate selective membranes are available. However, in this paper, the discussion is limited to water/organic solvent mixtures using membranes that preferentially permeate water. Such membranes are available. The process is illustrated with two mixtures: ethanol (light component)/water (heavy component) and acetic acid (heavy component)/water (light component) mixtures. In both cases, the combination process reduces the energy consumption of the separation to half that of simple distillation.

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This paper describes the development of membranes based on perfluoro polymers for the separation of aqueous ethanol mixtures in pervaporation or vapor permeation mode. Hydrophobic perfluoro polymers were selected because their chemical and thermal stability allows them to be used at temperatures up to 130 °C in hot ethanol/water vapors. The permeance and selectivity of membranes made from these polymers are quite different from the properties of the cross-linked hydrophilic membranes that are commonly used to separate water/ ethanol mixtures. Perfluoro polymers absorb less than 1% liquid in mixtures ranging from pure water to pure ethanol. As a result, the water permeance and water/ethanol selectivity of the membranes are essentially independent of feed water/ethanol composition. However, the water permeances of perfluoro membranes are low for commercial applications. Multilayer composite membranes, consisting of a perfluoro protective layer and a selective hydrophilic polymer underlayer, have the stability of hydrophobic perfluoro membranes combined with the high permeances and good selectivities of hydrophilic membranes.

Carbon dioxide capture, utilization, and storage (CCUS) has been identified as an effective method of mitigating anthropogenic CO 2 emissions. To date, most research and development has centered on capturing CO 2 emitted from coal power plants, as they are the largest point source emitters globally. However, cement and steel plants also emit large amounts of CO 2 and are potentially easier targets for a CO 2 capture process because the CO 2 in their flue gas tends to be more concentrated. In this paper, the feasibility of capturing CO 2 from cement and steel plants is examined using currently available membrane technology. Coal power plant flue gas contains 13−15% CO 2 ; cement and steel plant flue gas contains 20−30% CO 2 ; this higher CO 2 concentration is useful for all separation technologies, but especially for membranes where separation is strongly dependent on the partial pressure driving force. Membrane-based systems can capture 80% of the CO 2 emitted from cement or steel production processes at costs of $40 to $50/tonne of CO 2 captured. Lower costs are possible if lower capture rates are considered. This makes CO 2 capture from these gas streams an attractive first application for commercial membranes recently developed for flue gas treatment. Article pubs.acs.org/IECR