Purification of propylene oxide by distillation

• US 3,909,366 A
• Filed: 06/28/1972
• Issued: 09/30/1975
• Est. Priority Date: 09/07/1967
• Status: Expired due to Term

• Current Assignee: ARCO Chemical Technology LP A Partnership of de
• Original Assignee: Alfredo Garcia Jr, John P. Schmidt
• Inventors: Schmidt, John P., Garcia, Alfredo Jr.
• Primary Examiner(s): Yudkoff, Norman
• Assistant Examiner(s): Sanders, D.
• Application Number:
  US05/266,962
• Time in Patent Office: 1,189 Days
• Field of Search: 203/69,68,70 260/348.5L
• US Class Current: 203/69
• CPC Class Codes: C07D 301/32 Separation; Purification

Abstract

Propylene oxide is purified with respect to contaminating paraffinic and olefinic hydrocarbons by extractive distillation in the presence of an aromatic hydrocarbon having from 6 to 12 carbon atoms in the molecule.

Claims

1. A PROCESS FOR PURIFYING PROPYLENE OXIDE CONTAINING AS IMPURITIES HYDROCARBONS HAVING 5 TO 7 CARBON ATOMS WHICH COMPRISES EXTRACTIVELY DISTILLING SAID IMPURE PROPYLENE OXIDE WITH AN EXTRACTIVE DISTILLATION SOLVENT CONSISTING ESSENTIALLY OF A MONO-CYCLIC HYDROCARBON HAVING 6 TO 12 CARBON ATOMS AND HAVING A MELTING POINT BELOW 50*C IN AN EXTRACTIVE DISTILLATION COLUMN WHEREIN SAID PROPYLENE OXIDE IS INTRODUCED INTO SAID EXTRACTIVE DISTILLATION COLUMN, SAID AROMATIC HYDROCARBON IS INTRODUCED INTO SAID COLUMN AS A SEPARATE STREAM AT A POINT HIGHER THAN THE POINT OF INTRODUCTION OF SAID PROPYLENE OXIDE, PURIFIED PROPYLENE OXIDE IS REMOVED AS A DISTILLATE FROM SAID EXTRACTIVE DISTILLATION COLUMN, AND SAID AROMATIC HYDROCARBON ENRICHED IN SAID HYDROCARBON IMPUITIES IS REMOVED AS BOTTOMS FROM SAID EXTRACTIVE DISTILLATION VOLUMN.

2. A process according to claim 1, wherein the aromatic hydrocarbon is present in a quantity of at least about 1 part by weight per 3 parts by weight of propylene oxide.

3. A process according to claim 1, wherein the aromatic hydrocarbon has from 7 to 8 carbon atoms in the molecule.

4. A process according to claim 1, wherein the extractive distillation is carried out at pressures of from about 3 psia to about 100 psia.

5. A process according to claim 1, wherein the impure propylene oxide is produced by the epoxidation of propylene.

6. A process according to claim 5, wherein the epoxidation is effected by means of an aromatic hydroperoxide.

7. A process according to claim 1, wherein the impure propylene oxide contains propylene derivatives.

8. A process according to claim 1, wherein the aromatic hydrocarbon is ethylbenzene.

9. A process for purifying propylene oxide formed by the epoxidation of propylene and containing paraffinic and olefinic hydrocarbon contaminants having 5 to 7 carbon atoms which comprises extractively distilling the impure propylene oxide with an extractive distillation solvent consisting essentially of a mono-cyclic aromatic hydrocarbon having a melting point below 50*C, in an extractive distillation column by introducing said impure propylene oxide into said column, introducing said aromatic hydrocarbon into said column as a separate stream at a point higher than the point of introduction of said propylene oxide, separating purified propylene oxide as a distillate, and separating said aromatic hydrocarbon enriched in said contaminants as bottoms, said aromatic hydrocarbon being present in the amount of at least about one part by weight per three parts by weight of propylene oxide.

10. A process according to claim 9, wherein the aromatic hydrocarbon is present in the liquid phase in a quantity of from about 1 part by weight to about 20 parts by weight per 1 part by weight of propylene oxide.

11. A process according to claim 9, wherein the aromatic hydrocarbon has from 7 to 8 carbon atoms in the molecule.

12. A process according to claim 9, wherein the impure propylene oxide is obtained by the epoxidation of propylene by means of an aromatic hydroperoxide, contains propylene derivatives having 6 carbon atoms in the molecule, and the extractive distillation is carried out at pressuRes of from about 3 psia to about 100 psia.

13. In a process wherein propylene is epoxidized by means of an aromatic hydroperoxide to produce propylene oxide contaminated with hydrocarbons which are propylene derivatives having 5 to 7 carbon atoms and the propylene oxide is freed of said propylene derivatives by extractive distillation, the improvement which comprises effecting said distillation in the presence of an extractive distillation solvent consisting essentially of the aromatic hydrocarbon corresponding to the aromatic hydroperoxide used in said epoxidation, by introducing said contaminated propylene oxide into an extractive distillation column, introducing said aromatic hydrocarbon into said column as a separate stream at a point higher than the point of introduction of said propylene oxide, removing purified propylene oxide as a distillate from said extractive distillation column, and removing said aromatic hydrocarbon enriched in said propylene derivatives as bottoms from said extractive distillation column.

14. A process for purifying propylene oxide containing as impurities hydrocarbons having 5 to 7 carbon atoms which comprises extractively distilling said impure propylene oxide with an extractive distillation solvent which is a mono-cyclic aromatic hydrocarbon having 6 to 12 carbon atoms and having a melting point below 50*C, in an extractive distillation column wherein said propylene oxide is introduced into said extractive distillation column, said aromatic hydrocarbon is introduced into said column as a separate stream at a point higher than the point of introduction of said propylene oxide, purified propylene oxide is removed as a distillate from said extractive distillation column and said aromatic hydrocarbon enriched in said hydrocarbon impurities is removed as bottoms from extractive distillation column.