Extractive distillation and pressure-swing distillation for THF/ethanol separation

BACKGROUNDDuring the synthesis of a liquid crystal monomer, an effluent including tetrahydrofuran(THF) and ethanol is produced. Since THF and ethanol are both important solvents used in the chemical industry, it is necessary to separate the mixture of THF and ethanol for reuse. However, it is hard to effectively separate the mixture via simple distillation because a minimum azeotrope is formed in the binary system. RESULTExtractive distillation and pressure-swing distillation are adopted to separate the mixture and carefully optimized to achieve minimization of the total annual cost (TAC). A comparison between the two processes is carried out. Pressure-swing distillation is used to separate mixtures of THF and ethanol with various compositions. CONCLUSIONThe results indicate that pressure-swing distillation performs better than extractive distillation from the standpoint of both economic considerations and product purity. The feasible sequence of high and low pressure of two columns in a pressure-swing distillation is related to the feed composition. (c) 2014 Society of Chemical Industry