Claims
- 1. A process for separating 1-methoxy-2-propanol and 2-methoxy-1-propanol from an aqueous composition containing same, comprising:
a) dewatering of the aqueous composition comprising 1-methoxy-2-propanol and 2-methoxy-1-propanol to a concentration of 1-methoxy-2-propanol and 2-methoxy-1-propanol of at least 90 percent by weight in total to obtain a product, and b) isolating 1-methoxy-2-propanol and/or 2-methoxy-1-propanol or mixtures thereof from the product of step a) by distillation.
- 2. The process of claim 1, wherein the aqueous composition is a waste water stream obtained from the production of propylene oxide by reaction of propylene and hydrogen peroxide in the presence of methanol.
- 3. The process of claim 1, wherein the 1-methoxy-2-propanol and 2-methoxy-1-propanol in the aqueous composition are present in a concentration of less than 55 percent by weight in total.
- 4. The process of claim 1, further comprising concentrating the aqueous composition by a pre-distillation prior to dewatering step a) to contain 1-methoxy-2-propanol and 2-methoxy-1-propanol in an amount of at least 10 percent by weight in total.
- 5. The process of claim 1, further comprising adjusting the pH of the aqueous composition to be at least 6 prior to dewatering step a).
- 6. The process of claim 4, further comprising adjusting the pH of the aqueous composition to be at least 6 prior to the pre-distillation.
- 7. The process of claim 1, wherein at least 70 percent of the water contained in the aqueous composition is removed in dewatering step a).
- 8. The process of claim 1, wherein the concentration of water is reduced to less than 1 percent by weight in dewatering step a).
- 9. The process of claim 1, wherein dewatering step a) is operated as an azeotropic distillation with an additive, that forms a heteroazeotrope with water with a boiling point minimum.
- 10. The process of claim 1, wherein dewatering step a) is operated as an extractive distillation.
- 11. The process of claim 1, wherein dewatering step a) is operated as a membrane separation, using a semipermeable, hydrophilic membrane.
- 12. The process of claim 11, further comprising combining the membrane separation with an additional distillation, where a retentate is obtained in the membrane separation and residual water contained in the retentate of the membrane separation is removed as a distillate and this distillate is returned as feed of the membrane separation.
- 13. The process of claim 11, wherein the membrane separation is operated as a pervaporation with a liquid feed.
- 14. The process of claim 11, wherein the membrane separation is operated as a vapor permeation with a gaseous feed.
- 15. The process of claim 14, further comprising combining vapor permeation with a pre-distillation in such manner, that vapor from the top of the pre-distillation column is directly contacted with a semipermeable membrane of the vapor permeation unit without prior condensation.
- 16. The process of claim 1, wherein the distillation in step b) is a distillation method using a dividing-wall column.
REFERENCE TO A RELATED APPLICATION
[0001] This application claims the benefit of provisional application 60/389,896 filed Jun. 20, 2002 which is relied on and incorporated by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60389896 |
Jun 2002 |
US |