Comparative Analysis of Separation Schemes of Reaction Mixtures of Epichlorohydrin Production in the Presence of Various Solvents

Abstract

On the basis of a thermodynamic–topological analysis of phase equilibrium diagrams of reaction mixtures formed during the liquid phase epoxidation of allyl chloride with an aqueous solution of hydrogen peroxide in an organic solvent in the presence of a heterogeneous catalyst, two principal technological separation schemes are proposed. Two lower alcohols are considered as solvents: methanol and propanol-2. Both schemes are aimed at the isolation of all components in pure form and are based on the use of special separation methods: extractive rectification with dimethyl sulfoxide (separation of allyl chloride–methanol and propanol-2–water component pairs) and a combination of rectification and delamination (separation of binary allyl chloride–water and water mixtures–epichlorohydrin). The material balances of separation schemes for mixtures of a specific composition are calculated (one composition for both mixtures is considered). To determine the operation parameters of rectification columns (the number of separation stages, feed plate, and reflux ratio), a computational experiment is conducted using the Aspen Plus® software. Preference is given to parameters ensuring the production of all substances with a purity that meets GOST (State Standard) with minimum energy consumption. The separation scheme of the mixture with propanol-2 containing one column less is characterized by a lower total number of separation stages (by 32 theoretical plates) and lower (by 11%) energy consumption compared to the separation scheme of the mixture with methanol. In addition, the epoxidation reaction with an excess of propanol-2 (the alcohol concentration should be at least 68 wt %) can significantly simplify the allocation of the target product of epichlorohydrin, which is impossible for a system with methanol.