JPS588366B2 - Cyclohexane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for concentrating saponification waste liquid discharged in a cyclohexane oxidation process.

Cyclohexanone is well known as a raw material for Kabukuchi lactam, which is usually produced by oxidizing cyclohexane.

The products produced by this oxidation are cyclohexanol and some cyclohexanone, but this oxidation product usually contains organic acids, esters, etc. as organic impurities, and these impurities are dissolved in aqueous solutions of alkaline substances such as caustic soda. In the case where a soda salt aqueous solution (caustic soda is used), this case will be explained below.

) is separated from the oxidation products.

The aqueous soda salt solution discharged in this manner is called saponification waste liquid and is normally sent to a by-product recovery facility or an incineration facility for treatment.

However, since the concentration of solids or active ingredients in this waste liquid is generally not very high, it is necessary to concentrate it in advance.

Concentration is carried out by evaporation and dehydration according to a conventional method, but since a large amount of foam is generated during this process, the pressure reduction capacity is significantly reduced, making smooth operation difficult.

Moreover, due to this foaming, a large amount of the impurities are entrained in the waste water generated by evaporation and dehydration, causing a pollution problem.

In order to suppress this foaming, silicone-based and other well-known antifoaming agents have been used, but their effects have not been satisfactory and their costs have been considerable.

In view of the above circumstances, the present inventor conducted extensive research, solved the above problems, and arrived at the present invention.

That is, the present invention effectively suppresses foaming caused when concentrating the saponification waste liquid discharged in the cyclohexane oxidation reaction process at a low cost, and as a result, it can be used industrially without entraining organic impurities into the waste water. It is an object of the present invention to provide a method for concentrating the above-mentioned waste liquid advantageously, the object of which is to saponify the cyclohexane oxidation reaction product in an aqueous medium and separate it into an aqueous phase and an oil phase. In concentrating the saponification waste liquid forming the aqueous phase, the oil phase is purified by dehydrogenation and distillation to remove low-boiling impurities and/or high-boiling impurities discharged in the process of producing cyclohexanone. This is accomplished by a method of concentration.

The present invention will be explained in detail below.

Oxidation of cyclohexane is usually carried out by oxidizing with oxygen or an oxygen-containing gas in the presence of a cobalt organic acid salt, boric acid, etc. as a catalyst.

The oxidation reaction temperature is usually in the range of 80 to 200°C, and the reaction pressure may be in a range sufficient to maintain the liquid phase of the raw material cyclohexane at the reaction temperature, usually between normal pressure and 30°C.
It is selected from within the range of 0 kg/cm2.

The oxidation product thus obtained contains organic impurities such as organic acids and esters in addition to the raw materials cyclohexane, cyclohexanol, and cyclohexanone.

When boric acid is used as a catalyst, cyclohexanol is obtained as a boric acid ester, so the oil phase after hydrolysis and separation of boric acid into the aqueous phase is recovered as an oxidation product.

Cyclohexane is recovered from the oxidation product according to a conventional method, and organic impurities such as organic acids and esters are separated and removed, and the product is generally referred to as KA oil.

In order to remove the above-mentioned organic impurities from the oxidation product, it is saponified with an alkali such as caustic soda or caustic potash to make it water-soluble and transferred to the aqueous phase.

At this time, cyclohexanol and cyclohexanone migrate to the oil phase.

The aqueous phase containing organic impurities is the saponification waste liquid, which is usually subjected to by-product recovery treatment or, due to its high COD load, incinerated.

However, since the solid content concentration of saponification waste liquid is usually as dilute as 5 to 15% by weight, it is necessary to concentrate it in advance before subjecting it to the above treatment. Must be concentrated to a concentration of ~70% by weight.

Concentration is carried out by evaporative dehydration according to well-known methods.
The conditions need not be special.

For example, saponification waste liquid at 30 to 100°C
Concentration is carried out by introducing it into an evaporator at 600 mmHg.

Concentration can be carried out either batchwise or continuously, and the number of stages of the evaporator may be one or multiple.

The most significant feature of the present invention is that during concentration, KA oil as described below is dehydrogenated and used as a by-product waste oil discharged during distillation and purification as an antifoaming agent.

This by-product waste oil is obtained as follows.

KA oil consists of cyclohexanol and cyclohexquinone, and in order to convert this cyclohexanol component into cyclohexanone, KA oil is subjected to a dehydrogenation reaction.

The dehydrogenation reaction is generally carried out at a high temperature of 200 to 450°C by contacting with a catalyst in the gas or liquid phase.

However, in carrying out this reaction, it is not necessary to take any special means to generate by-product waste oil as an antifoaming agent used in the present invention.

The product liquid from the dehydrogenation reaction step is purified by distillation, and first, by-products with a lower boiling point than cyclohexanone are separated.

The term "low-boiling impurities" as used in the present invention refers to this fraction, and part or all of it is used alone or together with high-boiling impurities described below as an antifoaming agent during the concentration of saponification waste liquid.

In the above distillation purification, cyclohexanone is distilled out following low-boiling impurities and is recovered.

Cyclohexanol then distills off and is similarly recovered.

The former is recycled to the oxime step, and the latter is recycled to the dehydrogenation step.

Thus, the high-boiling fraction remaining after recovering cyclohexanol is the high-boiling impurity referred to in the present invention, and this fraction may be partially or completely as it is or combined with the low-boiling impurity mentioned above to be used in the present invention. It is used as an antifoaming agent in concentrating saponification waste liquid.

Therefore, in order to obtain low-boiling and high-boiling impurities as antifoaming agents used in the method of the present invention, it is not necessary to adopt special distillation conditions.

The components of these impurities have not all been clarified, but low-boiling impurities include pentanols and cyclohexanones, while high-boiling impurities include cyclohexanol, ethers, etc. Contains.

However, the amount of these low-boiling and high-boiling impurities added to the saponification waste liquid as an antifoaming agent is not particularly critical, but it is usually 0.5 to 5% by weight, preferably 1 to 3 weight% of the saponification waste liquid. be.

The antifoaming agent may be added to the saponification waste liquid in advance, or may be supplied to the evaporator.

The method of the present invention has been described in detail above. According to the method of the present invention, the by-product waste oil discharged in the cyclohexanone distillation process, which has not been used effectively in the past, can be used for defoaming during the concentration of saponification waste liquid. By using it as an antifoaming agent, foaming can be suppressed more economically and efficiently than known antifoaming agents, and the industrial value of the present invention is enormous.

Next, the method of the present invention will be explained by examples, but the present invention is not limited to these examples unless it departs from the gist thereof.

EXAMPLE A 25% aqueous solution of caustic soda was added to the reaction product obtained by catalytic air oxidation of cyclohexane under conditions of 165° C. and 10 kg/cm 2 (gauge pressure), followed by saponification treatment and phase separation.

The solid content concentration in the aqueous phase obtained by this liquid separation, that is, the saponification waste liquid, was 13%.

On the other hand, unreacted cyclohexane was removed by distillation from the liquid phase obtained by the above liquid separation, and the resulting fraction mainly consisting of cyclohexanone and cyclohegisanol was subjected to a catalytic reaction with a copper-diatomite catalyst at normal pressure. Thereafter, the mixture was cooled to obtain a product containing a large amount of cyclohexanone.

From this product, low-boiling components were removed under conditions of 95° C. and 200 mm (mercury column), and the low-boiling components were recovered as by-product waste oil.

Next, cyclohexanone was recovered under the conditions of 78° C. and 60 mm (mercury column), and cyclohexanol was recovered under the conditions of 78° C. and 3 Q mm (mercury column).

The remaining high-boiling components were recovered as by-product waste oil.

A mixture of low-boiling and high-boiling by-product waste oils (weight ratio: approximately 1:1) was added in an amount of 2% by weight (based on the saponification waste liquid) to the saponification waste liquid, and the mixture was heated at 80°C and 350 mm (mercury column). Evaporative dehydration was performed to concentrate the waste liquid until the solid content was 57%.

The results are shown in the following table, together with the results when conventionally known silicone oil was used.

Claims (1)

[Claims] 1. The cyclohexane oxidation reaction product is saponified in an aqueous medium, separated into an aqueous phase and an oil phase, and the raw material cyclohexane is recovered from the oil phase. A mixture mainly consisting of cyclohexanol and cyclohexanone is then heated in the presence of a catalyst. Lower 2
In a method for producing cyclohexanone by dehydrogenating at a temperature of 00 to 450°C and then distilling, in concentrating the aqueous phase, low-boiling impurities containing pentanols and cyclohexanone recovered in the distillation, A method characterized by concentrating in the presence of high-boiling impurities containing/or cyclohexanol and ethers.