Process for the purification of crude propene oxide

A technology of propylene oxide and compound, applied in the field of purification of crude propylene oxide, can solve the problems of inability to remove methanol, slow reaction and the like

Inactive Publication Date: 2005-12-28
EVONIK OPERATIONS GMBH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

From the fact that at high propylene oxide concentrations there is only a very small difference in the volatility of methanol and propylene oxide, a person skilled in the art can conclude that the process disclosed in EP-B 004 019 involving simple distillation is economically viable When operating at low cost, methanol cannot be removed to the desired level below 100ppm due to limitations in the number of separation stages and reflux ratio
[0009] EP-B 004 019 also teaches that aqueous hydrazine solutions have certain disadvantages when used to remove acetaldehyde: slow reaction with aldehyde and reaction with acetaldehyde to produce insoluble products
[0011] All known methods of purifying crude propylene oxide have the disadvantage that more than one distillation step is required to purify crude propylene oxide containing more than 1% by weight of methanol and more than 200 ppm of acetaldehyde to achieve a low methanol and acetaldehyde content. Required purity at 100ppm

Method used

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  • Process for the purification of crude propene oxide
  • Process for the purification of crude propene oxide

Examples

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Embodiment 1

[0082] Crude propylene oxide comprising 52.7 wt. % propylene oxide, 44.3 wt. % methanol, 2.2 wt. % water, 1500 wppm acetaldehyde and 430 wppm methyl formate was subjected to continuous extractive distillation. The extractive distillation was carried out in a structured-packed column with a separation efficiency of 80 theoretical orders at a reflux ratio of 2 and operating at a pressure of 1.8 bar absolute. At stage 20 (counting from the bottom) 1241 g / h of crude propylene oxide was added. At the same time, 207 g / h of a 1.5% by weight aqueous solution of hydrazine were fed on stage 40 (counted from the bottom). At the top of the column, purified propylene oxide comprising 99.92% by weight of propylene oxide, 36 wppm of methanol, 70 wppm of water, less than 20 wppm of acetaldehyde and 390 wppm of methyl formate was extracted at a flow rate of 658 g / h.

Embodiment 2

[0084] Repeat Example 1, the difference is only in:

[0085] 1301 g / h of crude propylene oxide comprising 51.3% by weight of propylene oxide, 46.13% by weight of methanol, 2.0% by weight of water, 1200 wppm of acetaldehyde and 280 wppm of methyl formate were mixed with 80 g / h of 0.5% sodium hydroxide The aqueous solutions were mixed and the mixture was allowed to react in a tubular reactor at 60°C for 30 minutes before being added to the extraction column. The aqueous hydrazine solution was added at a lower flow rate of 100 g / h. At the top of the column, purified propylene oxide comprising 99.98% by weight of propylene oxide, 33 wppm of methanol, 50 wppm of water, 8 wppm of acetaldehyde and 52 wppm of methyl formate was extracted at a flow rate of 658 g / h.

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Abstract

The present invention relates to a method for purifying crude propylene oxide containing methanol and acetaldehyde by extractive distillation operated continuously, wherein an extraction solvent capable of reducing the volatility of methanol is used, and the crude propylene oxide is fed into a distillation column above the feed point of the crude propylene oxide A compound containing unsubstituted NH2 groups and capable of reacting with acetaldehyde is added to obtain purified propylene oxide containing less than 100 ppm methanol and less than 100 ppm acetaldehyde. The present invention also relates to a method for catalytic epoxidation of propylene comprising said purification step.

Description

technical field [0001] The present invention relates to an improved process for the purification of crude propylene oxide in which methanol and acetaldehyde impurities are removed in separate distillation steps to levels below 100 ppm, and to a process for the preparation of propylene oxide using said purification step. Background technique [0002] From EP-A 100 119 it is known that propene can be converted by hydrogen peroxide to propylene oxide if titanium silicalite is used as catalyst. Methanol is the preferred solvent for high catalytic activity. The crude propylene oxide obtained by the process generally contains more than 1% by weight of methanol and more than 200 ppm of acetaldehyde from side reactions. Depending on the reaction conditions, the crude propylene oxide may also contain methyl formate in an amount exceeding 200 ppm. [0003] Most propylene oxide is used to prepare polyether polyols, and the polyether polyols thus prepared are used as raw materials for...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C45/83C07D301/32
CPCC07D301/32C07C45/83
Inventor 维利·霍芬托马斯·哈斯沃尔夫冈·韦尔格奥尔格·蒂勒
Owner EVONIK OPERATIONS GMBH
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