BACKGROUND During the synthesis of isopropyl alcohol (IPA) by hydration of propylene, diisopropyl ether (DIPE) is usually produced as a by-product. Because IPA and DIPE can form a binary homogeneous azeotrope with the minimum boiling temperature at atmospheric pressure, it is difficult to separate the binary mixture by simple distillation. RESULT For separating the azeotrope IPA + DIPE, side-stream extractive distillation column (SSED) and extractive dividing wall column (EDWC) processes with three entrainers [2-methoxyethanol (2-MEA), 2-ethoxyethanol and propylene glycol ethyl ether (PGEE)] were simulated and optimized based on the minimal total annual cost (TAC). Moreover, CO2 emissions of the six sequences were calculated and the impact on the environment evaluated. CONCLUSIONS The sequence of SSED with PGEE as entrainer can reduce TAC by <= 34.48%, but EDWC with PGEE can offer TAC reduction of <= 52.46%. The results demonstrate that the EDWC sequence with PGEE as entrainer is favourable for separating the binary azeotrope IPA + DIPE. (c) 2020 Society of Chemical Industry