What is the commonly used dehydration process for isopropyl alcohol in industry? Do you know?

Isopropyl alcohol is an important organic feedstock with a solid foundation in chemical engineering; it is primarily used as a solvent, an industrial cleaning agent, and an antifreeze in chemical processes. During its handling and application, stringent specifications are imposed on impurities, particularly water content. Because isopropyl alcohol and water form an azeotropic system, yielding an azeotrope that cannot be separated by conventional methods.

The commonly used industrial methods for dehydrating isopropyl alcohol include azeotropic distillation, extractive distillation, and adsorption–separation. Azeotropic distillation requires the use of an azeotrope‑forming agent to separate water from isopropyl alcohol, after which the solvent is recycled; benzene is often selected as such an agent. However, this method entails high energy consumption, leaves residual benzene in the product—leading to contamination—and poses occupational health and safety risks while contributing to environmental pollution. Ethylene glycol is frequently employed as an extractant in distillation, leveraging its selective solubility to remove water from isopropyl alcohol. Nevertheless, this approach suffers from product contamination, high energy demand, low extractant recovery, and operational complexity. Adsorption–separation exploits the difference in molecular size between isopropyl alcohol and water, using solid adsorbents to selectively capture water. Its advantages include avoiding the introduction of third‑party impurities, thereby enhancing product quality; however, the alternating adsorption–desorption cycle is non‑steady‑state, generates large volumes of wastewater containing isopropyl alcohol, and results in overall poor process performance.

Isopropyl alcohol dehydration via pervaporation is a novel membrane technology for separating mixtures, offering notable advantages such as high efficiency, excellent separation selectivity, and low energy consumption. It also features a simple process that requires minimal auxiliary treatment, with high system reliability and stability. Moreover, the process does not introduce additional components, making it an efficient and environmentally friendly technique. Research on applying pervaporation to the dehydration of aqueous isopropyl alcohol has been ongoing for a long time; however, existing findings remain insufficient for industrial-scale implementation, particularly in terms of processing efficiency, product purity, and comprehensive process integration. Consequently, how to scale up while maintaining the desired level of dehydration—or, conversely, how to further reduce energy consumption during scale-up—has remained a key area of intensive investigation for researchers in this field.

A method for the dehydration and purification of isopropyl alcohol, together with an integrated low-energy‑consumption unit for the deep dehydration of aqueous isopropyl alcohol tailored to this method.

The method for dehydrating and purifying isopropyl alcohol comprises the following steps: an aqueous isopropyl alcohol feed is conveyed at a mass flow rate of 800–1200 kg/h to a heat exchanger for preheating; the preheated feed is then vaporized and introduced into a membrane separation module at a pressure of 0.2–0.4 MPa and a temperature of 100–130°C to effect dehydration; the water‑free isopropyl alcohol product vapor (i.e., the permeate) is first routed to a heat exchanger for heat exchange with the feed, after which it is condensed and collected as the final isopropyl alcohol product.