Process for the continuous preparation of propylene oxide

In a liquid phase continuous process for producing propylene oxide comprising oxidizing propylene by contacting propylene with a molecular oxygen-containing gas in a solvent comprising an organic solvent which is water-insoluble and is as immiscible with organic carboxylic acids as possible and selected from the group consisting of monochlorobenzene, dichlorobenzene, trichlorobenzene and tetrachlorobenzene and mixtures thereof at a temperature and pressure necessary for the oxidation reaction and condensing the gaseous reaction products, the improvement comprising:

• adding to the condensed gaseous reaction products an amount of water necessary to dissolve substantially any undissolved organic carboxylic acids present therein thereby producing a two-phase system comprising (1) an aqueous phase containing said acids and (2) an organic phase containing said solvent and unreacted propylene;
• separating said aqueous phase from said two-phase system and recycling said organic phase to said reaction;
• removing a liquid containing propylene oxide from the reaction system;
• and
• recovering said propylene oxide from said liquid.