JPS60174765A - Purification of caprolactam with ozone - Google Patents

Abstract

PURPOSE:To obtain high-purity caprolactam, etc., by forming ozonized oxygen by an ozonizer using O2 as a raw material, diluting O2 in the ozonized oxygen with an intert gas to a concentration safe in use to give an O3 gas, purifying caprolactam, etc. by the use of the O3 gas. CONSTITUTION:Ozonized oxygen (O2+O3) is formed by an ozonizer using O2 as a raw material, this ozonized oxygen is blended with air or N2 or another inert gas, so that O2 concentration in the ozonized gas is diluted to a desired value. The ozone gas after dilution is used as a purifying gas, bubbled through caprolactam, etc. impurities contained in caprolactam are oxidized, converted into precipitate, etc., and removed, to give high-purity caprolactam useful as raw material for nylon, etc. EFFECT:Since a discharge area in the ozonizer required is 1/2 the area of use of air as a raw material and a dehumidifying column is not required, installation cost can be extremely reduced, and economically operation cost such as power consumption, etc. after that can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a method for purifying caprolactam, etc., which is used as a raw material for nylon, etc., by using ozone.

[Prior art]

It is desired that raw materials for producing caprolactam-based nylon and the like be as pure as possible. For this reason, these raw materials undergo pre-treatment to remove impurities before use.
will be carried out. Impurities are colored substances, etc., which are oxidized with an oxidizing agent in an aqueous raw material solution, and removed and purified in place of a precipitate.

As such a conventional oxidizing agent, for example, potassium permanganate is used. Potassium permanganate is a well-known reddish-purple crystal, and when it is added to an aqueous solution of caprolactam, etc., as the oxidation reaction progresses, it loses its color and its oxidizing power decreases. Once it disappears, it turns colorless.

In recent years, ozone has been increasingly used industrially as an oxidizing agent for purification in place of solid oxidizing agents such as nigra. Ozone can be continuously produced using an ozone generator equipped with a silent discharge tube using either air or oxygen as the raw material.

When using C as an oxidizing agent for purification, it is bubbled in an aqueous solution of caprolactam or the like to oxidize C impurities.

Here, from the viewpoint of industrially using ozone as an oxidizing agent for purification, we will discuss the cases where oxygen is used as the raw material for ozone production and the case where air (20% oxygen) is used.

First, when comparing the amount produced under the same conditions such as discharge area, discharge voltage, temperature, and flow rate of raw material gas, it is found that since ozone production progresses monthly with respect to oxygen concentration, the amount produced in the case of air is If it is 1, then in the case of oxygen it is 2, which means that twice the amount of oxygen produced can be obtained. Therefore, when the same amount of ozone is obtained, when oxygen is used, the number of discharge tubes (discharge surface) is only % of that when air is used, and the equipment cost is halved. °Also, it is necessary to use a sufficiently dry raw material gas, but when air is used as a raw material, general atmosphere is used, so a dehumidification tower is required. etc. are required.

When oxygen is used as a raw material, there is no need for such a dehumidification tower. Therefore, considering the elimination of the need for a dehumidifying tower and the scale of the discharge section mentioned above, the use of oxygen is much more advantageous in terms of equipment costs.

Furthermore, regarding the subsequent operating costs, the amount of electricity used is much lower when oxygen is used as the raw material, so the use of oxygen is more advantageous in this respect as well.

As described above, if the costs of oxygen and air, and the respective raw material gas costs themselves, are not considered, it is much more advantageous to use oxygen as a raw material in terms of both equipment costs and operation costs.

However, in general, ozone generators generate a part of the raw material gas as ozone, and when oxygen is used as a raw material, the ozone generator generates ozonized oxygen (02
+03). For this reason, the exhaust gas after refining caprolactam must be oxygen-rich, and if there are oil-like impurities precipitated during the refining process, the coexistence of these oil-like impurities and the oxygen-rich gas may lead to dangers such as explosions. There was a problem. In this respect, although the use of oxygen is more advantageous in terms of cost as mentioned above, ozone generators using oxygen as a raw material for generating refined gases such as caprolactam have not been used.

[Purpose of the invention]

This invention was developed by focusing on these conventional problems, and uses an oxygen raw material as an ozone generator, and after diluting the ozonized oxygen generated by this ozone generator with an inert gas. It is an object of the present invention to solve the above-mentioned problems by using this gas as a gas for purification. The method is characterized in that the ozonated oxygen is mixed with air or other inert gas such as nitrogen to dilute the oxygen concentration in the ozonated oxygen to a required value, and the diluted ozonated gas is used to purify caprolactam and the like.

〔Example〕

First, an example of a device to which the present invention is applied will be explained with reference to the drawings. Reference numeral (1) in the figure is a known silent discharge type ozone generator, and a required number of discharge tubes (not shown) are arranged in parallel in this generator (1), and a discharge voltage is supplied to these discharge tubes. A step-up transformer, voltage regulator, etc. are attached. An oxygen gas supply pipe (2) is connected to the raw material gas introduction side of the ozone generator (1) via an oxygen gas flow meter (3a), and a discharge pipe (4) for the ozonized oxygen to be produced is connected to a mixer. (5). A blower (6) for supplying dilution air is separately introduced to the mixer (5) via a dilution gas flow meter (3b) at a temperature of °C. Then, the diluted ozonized gas feed pipe (7) led out from the mixer (5) is led to the purification tower (8).

The diluted ozonized gas is bubbled into the caprolactam aqueous solution contained in the granulation tower (8) and used for oxidation removal of impurities. (9) is a discharge pipe, and C11 is an ozone decomposer.

Next, a method and operation of purifying caprolactam using the above-mentioned apparatus will be explained.

Purification of caprolactam is usually carried out as a pretreatment when producing nylon using caprolactam as a raw material. As the raw material oxygen gas supplied from the C supply pipe (2) to the ozone generator (1), oxygen gas generated as a by-product of the nitrogen gas used in the production of nylon is used. That is, when producing nylon using caprolactam as a raw material, the upper part of the polymerization tower containing the caprolactam raw material is sealed with nitrogen gas during the polymerization process. This nitrogen gas is produced by fractionating liquid air.
Oxygen gas is generated. This oxygen gas is used as a raw material gas for ozone production. Oxygen gas obtained by fractional distillation from liquid air is dry and of high purity, so it is suitable as a raw material gas for ozone production.

Then, ozonized oxygen (02+03) is generated by diosine generation a(1) by using oxygen such as °C as a raw material and silent discharge at °C. The raw material oxygen does not have to be 100% oxygen, but may have a content in the range of 40 to 100%. In this case, the ozone content of such raw oxygen is typically 20 to 30.
Ozonated oxygen of mV/18 degrees is produced. That is, the generated ozonized oxygen contains a large amount of unreacted oxygen.

In the present invention, instead of using such oxygen-rich ozonized oxygen as it is as an oxidizing agent for caprolactam purification, it is diluted with air or nitrogen or other inert gas to reduce the oxygen content. vx>U is reduced to a value within a safe range for use. In the example shown in the figure, air is used as the diluent gas, and the required flow rate is sent from the blower (6) to the mixer (5) via the flowmeter (3b) to adjust the oxygen concentration to the required value. It has been reduced to. The amount of oxygen lachrymation after dilution should be about 20 to 30% more than that when ozone is generated using air as raw material.Then, this diluted ozonated gas is sent to a purification tower (8
) and bubbled into the aqueous caprolactam solution to oxidize impurities contained in caprolactam and convert them into precipitates, which are removed and purified. *i7 The exhaust gas after H decomposes ozone in the ozone decomposer a1 and then releases it appropriately. In the process of emitting 1'A% as shown in Figure 1, the oxygen content in the C ozonated gas is diluted to the required value that is safe for use, so impurities such as oil and fat are present. Even if it is exposed to air, it does not pose any danger such as explosion, and safety is guaranteed.

In addition, in the above-mentioned examples, the substances to be subjected to C recycling are:
Although the case of caprolactam has been described above, this invention is not limited to such caprolactam.
Objects other than caprolactam can also be purified as long as they can be purified by 'C using an oxidizing agent equivalent to potassium permanganate.

〔Effect of the invention〕

This invention uses an ozone generator made of oxygen Jα, and dilutes the ozonized oxygen generated by this ozone generator with air or nitrogen or other inert gas to adjust the oxygen content to a level that is safe for use. Since the diluted product is used to purify caprolactam, etc., the discharge area for ozone generation is only % of that for air raw material, and a dehumidification tower is not required, reducing equipment costs. It is possible to significantly reduce the amount of electricity used, and furthermore, the operating costs such as the amount of electricity used thereafter can also be lowered, which is extremely advantageous in terms of economic efficiency.

゛Also, according to an example in which oxygen obtained as a by-product during the production of nylon using caprolactam is used as an oxygen raw material, the cost of the oxygen raw material can be almost ignored, so operating costs etc. can be further reduced. You can get the effect of

[Brief explanation of the drawing]

The figure is a block diagram showing an example of an apparatus applied to the method for purifying capro2cutam etc. using ozone according to the present invention. 1 Niosin generator 2: Oxygen gas supply pipe 5: Mixer 6
: Proar 8: Sheath tower 10 Niosin decomposer Japan Ozone Co., Ltd. Agent Ashi 1) Direct circulation

Claims (1)

[Claims] Ozonized oxygen is generated using an ozone generator using oxygen as a raw material, and the ozonized oxygen is mixed with air or nitrogen or other inert gas to dilute the oxygen concentration in the ozonized RA to the required value. , a method for preparing fa such as caprolactam using ozone, which is characterized by purifying caprolactam etc. with this diluted ozonized gas.