Epichlorohydrin from Propylene (Allyl Alcohol Intermediate)

The process under analysis comprises two major sections: (1) Allyl Alcohol Synthesis; and (2) Epichlorohydrin (ECH) Production.

Allyl Alcohol Synthesis. Propylene is mixed with acetic acid and oxygen. The mixture, in the vapor phase, is passed through a fixed palladium-based catalyst bed, where the formation of allyl acetate takes place. The reactor effluent comprises allyl acetate, unreacted feeds and carbon dioxide formed by side reactions. The effluent is divided into a gaseous and a liquid stream. The gases (mostly unreacted oxygen and propylene), also containing CO2, are routed to a CO2 Removal system and then recycled to the reactor inlet. The liquid portion of the reaction effluent is transferred to the Hydrolysis reactor, where allyl acetate is converted into allyl alcohol and acetic acid. The hydrolysis product is treated in the allyl alcohol purification system, where unreacted allyl acetate and acetic acid are recovered and recycled to the hydrolysis reactor and acetoxylation reactor, respectively. An aqueous solution of allyl alcohol is transferred to the Epichlorohydrin synthesis section.

Epichlorohydrin Production. Aqueous allyl alcohol, hydrochloric acid, and gaseous hydrogen chloride are mixed and fed to the chlorination reactors, where 2,3-dichloro-1-propanol is obtained. Reaction effluent is sent to the Hydrogen Chloride Recovery column, where hydrogen chloride is recovered both as dry vapors and aqueous solution. 2,3-dichloro-1-propanol is then fed to the saponification reactor along with a calcium hydroxide slurry. The saponification reaction results in Epichlorohydrin and calcium chloride, which is removed in by means of a distillation column downstream. Finally, light and heavy impurities are separated through a last distillation step, and high-purity Epichlorohydrin is obtained.