Patent GB-623583-A (GB)
Title: Improvements in or relating to the recovery of ethylene oxide
IPC: C07D301/32
Filed: 1946-11-13
Abstract: Ethylene oxide is recovered from a dilute aqueous solution thereof obtained by the absorption of dilute gaseous ethylene oxide in an aqueous solvent, by subjecting the solution to the action of steam at sub-atmospheric pressure, subjecting the resulting vaporous ethylene-oxide-steam mixture to compression in more than one stage up to a pressure at which the ethylene oxide is capable of being absorbed by a much smaller volume of aqueous solvent than was used for the original absorption, with cooling of the vapours after each stage of compression in order to remove the bulk of the water vapour by condensation, and then absorbing the ethylene oxide in an aqueous solvent to form a solution of substantially higher concentration than the initial solution.  The ethylene oxide may then be recovered by distillation from the concentrated solution.  The pressure of the ethylene oxide-steam mixture is preferably approximately doubled at each stage of the compression and the pressure up to which the mixture is compressed is preferably such that it is capable of being absorbed in a volume of aqueous solvent which is less than one-twentieth and advantageously less than one-fiftieth of that which was used for the original absorption.  The introduction of steam into the dilute aqueous solution and the subatmospheric pressure may be such that the temperature of the solution is not materially altered or such that a rise in temperature, preferably of from 3 DEG  to 5 DEG  C., takes place.  In examples: (1) a dilute aqueous solution of ethylene oxide is admitted to the top of a packed tower and steam is fed into the base of the tower to flow upwards counter-current to the descending ethylene oxide solution, the pressure at the top of the tower being maintained at 42 mm. of mercury.  The stripped solution is withdrawn from the base of the tower together with some condensed steam, while the vapours from the top of the tower are fed to the first stage compressor for compression from 42 mm. to 110 mm. of mercury, and then into a condenser for cooling.  The uncondensed vapours are then compressed from 110 mm. to 290 mm. in a second compressor and the compressed vapours again cooled in a second condenser, the uncondensed vapours being then finally compressed to atmospheric pressure and the compressed vapours cooled in a final condenser. The uncondensed vapours consisting of ethylene oxide and a small amount of water are then absorbed in a small packed tower by a counter-current flow of water and the solution obtained is combined with the solution withdrawn from the final condenser to form an approximately 12 per cent by weight solution of ethylene oxide in water which can be distilled to give pure ethylene oxide. The dilute ethylene oxide solutions withdrawn from the first and second condensers can be pumped to an intermediate point in the final absorption tower without reducing the final concentration of the ethylene oxide solution; (2) a dilute aqueous solution of ethylene oxide is treated as in (1) except that the pressure at the top of the stripping tower is maintained at 27 mm. of mercury, the first compression is from 27 mm. to 80 mm. of mercury, the second compression from 80 mm. to 250 mm. of mercury, while the final compression raises the pressure of the vapours to atmospheric pressure as in (1).  Specifications 533,054, 564,646 and 589,547 are referred to.