Recovery of propylene oxide by plural stage distillation

Claim 1

IN A PROCESS FOR RECOVERING PROPYLENE OXIDE IN A HIGH STATE OF PURITY FROM A CRUDE PROPYLENE OXIDE PRODUCT OBTAINED BY THE CATALYTIC EPOXIDATION OF PROPYLENE WITH AN OGANIC HYDROPEROXIDE, SAID PRODUCT INCLUDING PROPYLENE, PROPYLENE OXIDE, ACETALDEHYDE, PROPIONALDEHYDE AND OTHER MATERIAL HAVING A HIGHER BOILING POINT THAN THAT OF PROPYLENE OXIDE, THE IMPROVEMENT CONSISTING OF THE SEQUENTIAL STEPS OF A. REMOVING PROPYLENE BY DISTILLATION FROM SAID PRODUCT TO OBTAIN A SUBSTANTIALLY PROPYLENE-FREE CRUDE PROPYLENE OXIDE PRODUCT, FOLLOWED BY B. CHARGING THE SAID SUBSTANTIALLY PROPYLENE-FREE, CRUDE PROPYLENE OXIDE PRODUCT INTO A FIRST FRACTIONATOR, WITHDRAWING THEREFROM A FIRST DISTILLATION OVERHEAD CONTAINING ACETALDEHYDE, AND WITHDRAWING THEREFROM A FIRST DISTILLATION BOTTOMS CONTAINING PROPYLENE OXIDE, PROPIONALDEHYDE, AND SAID MATERIAL HAVING A HIGHER BOILING POINT THAT THAT OF PROPYLENE OXIDE, FOLLOWED BY C. CHARGING THE SAID FIRST DISTILLATION BOTTOMS TO A SECOND FRACTIONATOR, WITHDRAWING THEREFROM A SECOND DISSILATION OVERHEAD CONTAINING PROPYLENE OXIDE SUBSTANTIALLY FREE OF ALDEHYDES AND OF SAID HIGHER BOILING MATERIAL, AND WITHDRAWING THEREFROM A SECOND DISTILLATION BOTTOMS CONTAINING SAID HIGHER BOILING MATERIAL.