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Design, Simulation, and Pilot Verification of a Coupled Azeotropic and Extractive Distillation Process for the Production of Propylene Oxide with High Purity

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journal contribution
posted on 29.04.2021, 16:40 by Song Hu, Jinlong Li, Mujin Li, Weisheng Yang
To obtain the production of propylene oxide (PO) with high purity, a coupled azeotropic and extractive separation process is proposed to remove the impurities such as aldehyde, methanol, methyl formate, 2-methylpentane, water, propylene glycol (PG), and so forth from crude PO. n-Butane is screened as an azeotropic entrainer for the disposal of the light impurities, while n-octane is employed for PO purification. For the PG removal, the process of withdrawing the PG and n-octane azeotropic mixture from the side of the solvent recovery column and then separating them through liquid–liquid phase split is designed. The simulation and the total annual cost (TAC) analysis are performed by Aspen Plus with the non-random-two-liquid thermodynamic model. The key design variables such as the ratio of solvents to crude PO, the theoretical plate number, the feed stage, and so forth are analyzed and determined based on the minimal TAC method, in which the capital, energy, and raw material costs are comprehensively considered. The result that is verified through the pilot experiment shows that the purity of the PO product exceeds 99.99 % in mass and the impurity contents of formaldehyde and water are lower than the national standard value of China (GB/T 14491-2015).