JPH058692B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to a method for producing triethanolamine. More specifically, the present invention relates to a method for producing triethanolamine that does not develop an abnormal color when neutralized with an organic or inorganic acid. [Prior Art] Triethanolamine is usually produced by reacting ethylene oxide and aqueous ammonia. In this case, the reaction product leaving the reactor is sent to a stripper after separating unreacted ammonia, where water is removed to obtain mixed ethanolamine containing mono-, di-, and triethanolamine. . Next, this mixed ethanolamine is sent to a first distillation device to separate monoethanolamine by vacuum distillation, the bottom liquid is sent to a second distillation device to separate diethanolamine by vacuum distillation, and the bottom liquid is sent to a third distillation device. It is sent to a distillation device and triethanolamine is separated by vacuum distillation. The triethanolamine thus obtained usually contains diethanolamine in 4-
Since it contains 10% by weight, it is necessary to separate and purify diethanolamine again by vacuum distillation, or separately send the bottom liquid of the second distillation unit to the next distillation unit and separate the low-boiling components by vacuum distillation. High purity triethanolamine is produced by further distilling the bottom liquid under reduced pressure using the following distillation apparatus. [Problems to be solved by the invention] On the other hand, triethanolamine is used as fatty acid amide and higher alkyl sulfate ester in cosmetics, detergents,
Used as a raw material for emulsifiers, etc. Therefore, not only high purity is required, but also when performing secondary reactions during use, for example, when neutralizing with organic or inorganic acids such as acetic anhydride, citric acid, sulfuric acid, hydrochloric acid, and phosphoric acid. , those that do not exhibit abnormal coloring are required. However, although it is possible to achieve high purity using conventional manufacturing methods, it is extremely difficult to achieve high quality, as the hue and acid coloring tend to be high, and even if the manufacturing method is low, changes over time are large. Ta. In addition, in order to achieve high purity and high quality in conventional production methods, it is necessary to sufficiently separate low-boiling fractions and high-boiling fractions, so the reflux ratio of the distillation column is increased and separation is required. Operations such as increasing the amount of distillation or the amount taken out from the bottom are required. As a result, the yield of the product was reduced, which was disadvantageous in terms of economy, and on the other hand, the effect of improving acid neutralization coloration was not obtained. For this reason, various methods have been proposed as methods for producing highly purified triethanolamine with little coloring during acid neutralization. For example, Japanese Patent Publication No. 41-13978 discloses a method for long-term prevention of hue and citric acid coloring by adding and mixing alkali borohydride to triethanolamine obtained by distillation. Additives are expensive, and when added in small amounts, the effect of improving the hue and citric acid coloring immediately after treatment is recognized;
The problem is that the effect is not sustainable, and in order to prevent changes over time, it is necessary to increase the amount added, which increases the product cost. Furthermore, in JP-A-56-2942, after triethanolamine is distilled out by vacuum distillation, it is immediately brought into contact with an oxygen-containing gas at a temperature of 25 to 100°C to color it during acid neutralization. A method for preventing this is disclosed. However, this method has the disadvantage that, among acid-neutralized coloring, acetic anhydride, sulfuric acid, etc. have the effect of reducing the degree of coloring, but the effect against phosphoric acid is not sufficient, and the hue usually worsens. In view of the above, an object of the present invention is to provide a method for producing highly pure triethanolamine that is less colored during acid neutralization. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventor conducted extensive research and completed the present invention. That is, the present invention provides a method for producing ethanolamines by reacting ethylene oxide and ammonia, in which crude triethanolamine obtained by separating unreacted substances from the reaction product and monoethanolamine and diethanolamine is treated with oxygen. This is a method for producing triethanolamine that does not become colored during acid neutralization, which is characterized by carrying out a heat treatment at a temperature of 170 to 250° C. for 1 to 10 hours under conditions where the acid is inactive, followed by distillation under reduced pressure. The method of the present invention will be explained in more detail. The crude triethanolamine of this invention is separated in a conventional manner from a mixture of ethanolamines prepared by the conventional reaction of ethylene oxide and ammonia. In the method of the present invention, there is no problem even if the production ratio of the ethanolamines obtained is different. The reaction product is first separated from unreacted ammonia, and then sent to a dehydration tower to remove water to obtain a mixed ethanolamine containing mono-, di-, and triethanolamine. Next, monoethanolamine is separated from this mixed ethanolamine by vacuum distillation in a first distillation device, and the bottom liquid is sent to a second distillation device to separate diethanolamine by vacuum distillation. In the present invention, the bottom liquid obtained here, that is, crude triethanolamine, is supplied to a heat treatment apparatus and subjected to heat treatment. The heat treatment temperature of crude triethanolamine in the method of the present invention is 170 to 250°C, and if the heating temperature is less than 170°C, the heat treatment will take a long time and will not be practical and may not produce sufficient effects. I can't do it,
Moreover, when the temperature exceeds 250°C, the quality deteriorates due to new coloring caused by products of thermal decomposition. The heat treatment time is 1 to 10 hours, and within an appropriate temperature range, the heating time can be lengthened if the heat treatment temperature is low, and shortened if it is high. Particularly preferable heat treatment temperature is 190 to 210℃, time is 5
~2 hours. The operating pressure can be pressurized, normal pressure, or reduced pressure.
There are no particular limitations. The heat treatment of the present invention can be carried out either batchwise or continuously. Further, the heat treatment apparatus according to the method of the present invention does not require any complicated equipment; it is a heating pot type having an ordinary heat exchanger or jacket or internal coil, and is capable of maintaining a predetermined residence time. Good to have. However, when using a continuous method, plug flow is preferable because mixed flow types may sometimes produce variations in effectiveness due to shot passes. In addition, in the case of batch type, good effects can be obtained by stirring or pump circulation. The crude triethanolamine that has been heat-treated in this way is sent to a third distillation device, and purified triethanolamine of high quality is obtained by distillation under reduced pressure. It is also possible to combine batch heat treatment and batch distillation, for example, as follows. That is, the bottom liquid of the second distillation apparatus is supplied to the batch distillation column pot, heated while being circulated to the reboiler, and after heat treatment under predetermined conditions, low boiling point components are separated by vacuum distillation, and then triethanolamine is separated. It can be produced by distillation and separation. In the method of the present invention, it is further necessary to carry out these heat treatments and the subsequent vacuum distillation under conditions where oxygen is excluded. In order to achieve the purpose of the present invention, it is important to prevent air from leaking into the heat treatment equipment, triethanolamine vacuum distillation column, and ancillary equipment, and also to ensure that the inside of the equipment is sufficiently purged with nitrogen, etc. at the time of startup. It is necessary to use the product after removing oxygen gas. Conventionally, triethanolamine is susceptible to thermal deterioration, and it is said that the quality deteriorates when heated at high temperatures for long periods of time.In particular, under conditions of 190℃ or higher, there are problems such as discoloration of distillate products and large changes over time. was believed to occur. However, the triethanolamine obtained by the method of the present invention through high temperature treatment and vacuum distillation while strictly preventing contact with oxygen surprisingly has a good color, almost no acid neutralization coloring, and also shows no change over time. It is a small high quality triethanolamine. [Examples] The present invention will be specifically explained below using Examples and Comparative Examples. Example 1 In an ethanolamine production plant, ethylene oxide and a 30% by weight ammonia aqueous solution were reacted at a molar ratio of 1:3 under pressure at a reaction temperature of 60°C, unreacted ammonia was removed from the reaction solution, and then dehydrated and mixed. Ethanolamine was obtained, and then monoethanolamine and diethanolamine were separated by vacuum distillation to obtain crude triethanolamine as a column bottom liquid, consisting of 95-96% by weight of triethanolamine and the remainder being diethanolamine and a few high-boiling substances. was used as a raw material for the following treatment. The heat treatment equipment is a stainless steel autoclave with a capacity of 2 equipped with a nitrogen inlet/outlet and a stirrer, and the distillation equipment is a glass Widmer column with a diameter of 3 cm and a height of 50 cm, a nitrogen inlet/outlet and a capillary tube for nitrogen.
A glass flask was used, and the autoclave and vacuum distillation apparatus were directly connected through a conduit so that the crude triethanolamine after heat treatment could be transferred from the autoclave to the vacuum distillation apparatus using nitrogen pressure without coming into contact with air. The autoclave was purged with nitrogen to eliminate oxygen, and then 1 kg of the crude triethanolamine was charged therein. Furthermore, remove oxygen by replacing with nitrogen, and add 0.2
After pressurizing to Kg/cm ² G, the mixture was heated to 190° C. for 5 hours while stirring. After the heat treatment, the liquid was transferred from the autoclave to the distillation apparatus using nitrogen pressure so as not to come into contact with air. Then distilled under reduced pressure to 175 ~
A fraction at 178°C/3 mmHg was collected to obtain 850 g of triethanolamine with a purity of 98.7%. This purified triethanolamine was subjected to hue (APHA) measurement and phosphoric acid neutralization coloring test. Hue (APHA) is the value obtained by measuring the absorbance at a wavelength of 420 nm using a spectrophotometer based on distilled water and converting it to APHA. Moreover, phosphoric acid neutralization coloring is a value obtained as follows. That is, 45 g of triethanolamine was placed in a stoppered Erlenmeyer flask, 5 g of water was added and stirred, then 10 g of phosphoric acid and further 12.5 g of propylene glycol were added, mixed well, the flask was stoppered, and heated in a 75°C water bath for 20 minutes. It was determined by measuring the absorbance (-logT) at wavelengths of 420 nm and 530 nm with distilled water as a reference using a spectrophotometer. (The same applies hereinafter.) The hue (APHA) of the obtained purified triethanolamine is 10>, and the coloration due to phosphoric acid neutralization is
It was 0.015 at 420 nm and 0.008 at 530 nm. Comparative Example 1 In the same manner as in Example 1, crude triethanolamine was not heat-treated and only vacuum distillation was performed to obtain purified triethanolamine. Its hue is
30, Phosphoric acid neutralization coloring is 0.042, 530nm at 420mm
0.027, which was significantly inferior to the purified triethanolamine of Example-1. Examples 2 to 10 and Comparative Example 2 Examples 2 to 10 were carried out in the same manner as Example 1 except that the heating temperature and heating time were changed in Example 1.
I went there. Tables 1 and 2 show the processing conditions, the hue of the obtained purified triethanolamine, the results of phosphoric acid neutralization coloring, acetic anhydride neutralization coloring, and sulfuric acid neutralization coloring, Example 1, Comparative Example 1 This will be shown together with the results.
Further, Table 2 shows the acid neutralization coloring results of purified triethanolamine obtained by carrying out Comparative Example 2 in the same manner as Comparative Example 1. Note that acetic anhydride neutralization coloring refers to adding 1 ml of acetic anhydride to 30 g of triethanolamine, holding it at 80°C for 30 minutes, and using a spectrophotometer to measure the absorbance (-) at wavelengths of 530 nm and 445 nm using distilled water as standard.
logT), and sulfuric acid neutralization coloring refers to triethanolamine mixed with distilled water at a ratio of 1:1.
(by volume) and diluted with 62% by weight sulfuric acid.
After neutralizing to PH6.5 using a PH meter, the wavelength of 445 nm and
This is a value obtained by measuring absorbance (-logT) at 580 nm.

【table】

【table】

〔Effect of the invention〕

According to the method of the present invention, it is possible to easily and economically produce high-quality triethanolamine with high purity, almost no acid-neutralized coloring, and a good hue. In addition, the triethanolamine produced by the method of the present invention prevents coloring without any additives, so no impurities are mixed in.
It can be extremely advantageously used as a raw material for liquid detergents, body shampoos, cosmetics, etc.

Claims (1)

[Claims] 1. In a method for producing ethanolamines by reacting ethylene oxide and ammonia,
Crude triethanolamine obtained by separating unreacted substances, monoethanolamine, and diethanolamine from the reaction product is heat-treated at a temperature of 170 to 250°C for 1 to 10 hours in the absence of oxygen, and then distilled under reduced pressure. A method for producing triethanolamine without coloring during acid neutralization.