Extractive distillation for separating short-chain alcohols from water using cyclic carbonates as an extractive solvent: Experimental and process simulation
Alejandro Belinchón, Pablo Navarro, Ayala Rubias, Rubén Santiago, Elisa Hernández, José Palomar
Abstract
• Cyclic carbonates in the alcohol/water separation by extractive distillation. • Selection of cyclic carbonates deeply interacting with water by COSMO-RS. • Vapor-liquid equilibria of alcohol + water + cyclic carbonate systems by HSGC. • Glycerol carbonate as an efficient CO 2 -based solvent at process scale. Bioethanol has gained increasing importance in recent years due to the potential scarcity of fossil fuels and the urgent need to reduce CO 2 emissions. Other light alcohols, such as bioisopropanol, have significant potential, like ethanol, as gasoline additives, while tert -butanol plays a crucial role in the chemical industry. However, a major challenge arises to each alcohol separation from water (the most common impurity) due to the presence of an azeotrope. Among the dehydration technologies for these alcohols, extractive distillation stands out as one of the most efficient operations due to its energy savings. On the other hand, cyclic carbonates derived from CO 2 conversion processes have recently become very important as solvents for a wide range of applications. This work proposes the use of cyclic carbonates as extractive agents for separating various mixtures of light alcohol and water through extractive distillation. This work demonstrates the universality of this approach in terms of the cyclic carbonates applicability in a new system as well as their effectiveness for a series of light alcohols, for the first time. After preselecting and characterizing two cyclic carbonates, a whole process was designed to meet two purity levels for the three alcohols evaluated. Glycerol carbonate has shown to be a very competitive solvent, with energy consumption moving from 4000 to 11000 kJ/kg −depending on the alcohol type (tertbutyl alcohol < 2-propanol < ethanol) and purity assessed (0.99 < 0.995)-, confirming that cyclic carbonates are CO 2 -derived designer solvents capable of working well for polar mixtures.