JPS60126241A - Production of triethylene glycol - Google Patents

Abstract

PURPOSE:To produce a dioxane-free triethylene glycol useful as a raw material of detergent, cosmetic, surface active agent, cellophane, etc., by reacting ethylene oxide with diethylene glycol in the absence of catalyst. CONSTITUTION:Diethylene glycol is made to react with ethylene oxide at a molar ratio of 2-10 at 150-300 deg.C and 20-50kg/cm<2>G to obtain the titled compound. The reaction may be carried out batchwise or continuously. EFFECT:Since there is no addition of a basic substance to the reaction system, the post-treatment is absolutely unnecessary. The coloring problem and toxicity problem in the cosmetic use, etc. can be avoided because of the absence of dioxane in the product.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing triethylene glycol.

Triethylene glycol is an important substance as a raw material for detergents, cosmetics, surfactants, cellophane, etc. As a method for producing triethylene glycol, a method has been proposed in which ethylene oxide and diethylene glycol are reacted using a basic catalyst such as sodium hydroxide or potassium hydroxide (JP-A-50-82005). This method has the advantage of a high reaction rate and can be carried out at relatively low temperature and low pressure, but the triethylene glycol obtained by this method contains about 0.1 to 1.0% dioxane as an impurity. It has been found that this has an important relationship with the quality of triethylene glycol, especially the problem of coloring. In particular, dioxane as an impurity is a toxic substance and is unsuitable for use in cosmetics and the like.

As a result of intensive research into a method for producing triethylene glycol that does not substantially contain dioxane, and therefore has no coloring, the present inventor has found that, for example, as described in the specification of JP-A-50-82005, Contrary to the point that it is not economical as an industrial production method in the absence of a catalyst, it is possible to obtain dioxane-free triethylene glycol in the absence of a catalyst. This is the heading that led to the completion of the present invention.

That is, the method for producing triethylene glycol of the present invention is characterized by reacting ethylene oxide and diethylene glycol in the absence of a catalyst in order to produce triethylene glycol that does not substantially contain dioxane.

Ethylene oxide, which is a reaction raw material used in the present invention, can be produced by a direct oxidation method in which it is reacted with air or molecular oxygen-containing gas on a catalyst mainly composed of silver in the gas phase, or by a direct oxidation method in which ethylene oxide is reacted with air or a molecular oxygen-containing gas on a catalyst mainly composed of silver. There are ethylene oxides etc. obtained by the chlorohydrin method, which is synthesized and hydrolyzed.

The diethylene glycol used is one produced by a conventional method, specifically one produced by reacting ethylene oxide obtained by a direct oxidation method or a chlorohydrin method with water. When this production is followed, diethylene glycol is obtained as a mixed aqueous solution of mono-, di-, tri-, and tetraethylene glycol, so each glycol component is separated and purified as follows.

That is, after removing excess water from these ethylene glycol aqueous solutions, monoethylene glycol is separated by distillation, the bottom liquid of the distillation column is distilled in the next distillation column, and diethylene glycol is separated from the top of the column. As another method for producing diethylene glycol, for example, when ethylene oxide is produced by a direct oxidation method, the oxidized product is absorbed in water to recover the ethylene oxide, and then the ethylene oxide is diffused from the absorbed water to obtain ethylene oxide. In this step, a portion of the ethylene oxide reacts with absorbed water to form mono-, di-, tri- and polyethylene glycols.

Diethylene glycol is obtained from the ethylene glycols thus produced by the separation method described above. Any of these diethylene glycols can be used in the present invention.

The molar ratio of diethylene glycol/ethylene oxide used in the present invention is from 1 to 100, preferably from 2 to 10.
is within the range of If the molar ratio of diethylene glycol/ethylene oxide becomes too large, the circulating amount of diethylene glycol will increase too much, which is not preferable. On the other hand, if the molar ratio of diethylene glycol/ethylene oxide is too small, the production of tetra or polyethylene glycol will increase, and the temperature of the reaction system will increase due to the heat of reaction between ethylene oxide and diethylene glycol, or the pressure in the reactor will increase. becomes large, which is not desirable.

The present invention can employ either a batch type or a continuous type reactor.

The reaction temperature is 100-350°C, preferably 150-350°C.
00°C, reaction pressure is 5-10°Kif11G1, preferably 20-50 My/cn1G.

Since the method of the present invention does not add a basic substance such as sodium hydroxide into the reaction system, there is no need for any associated post-treatment, and the target triethylene glycol is actually free of dioxane. Since it is not contained, there is no problem of coloring or toxicity in applications such as cosmetics, and the production method is industrially extremely significant.

Hereinafter, the present invention will be specifically explained using examples.

Example: 500 i/hr of diethylene glycol and 5 kp/hr of ethylene oxide were introduced into the reactor, and the pressure was 5
5 Kf/Cm G z The reaction was carried out at a temperature of 270°C. The reaction rate of the raw material ethylene oxide was 99% or more. The selectivity of triethylene glycol in the reaction mixture is 91.0%
Met. Also 1. As a result of measuring dioxane in triethylene glycol by gas chromatography, it was not detected at all.

Comparative Example Diethylene glycol was introduced into the reactor at 5 ooip/hr, ylated ethylene at 5 o Ky/hr, and 45% potassium hydroxide G as a catalyst, IKg/hr.
The reaction was carried out at 5 to 103°C and 1.4 to 2.0 Kg/crlG.

The reaction rate of the raw material ethylene oxide was 99% or more, but the selectivity of triethylene glycol in the reaction mixture was 88%.
It contained 9% dioxane and 0.27% dioxane.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1) A method for producing triethylene glycol, which comprises reacting ethylene oxide and diethylene glycol in the absence of a catalyst to produce triethylene glycol substantially free of dioxane.