JPH0320373B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides at least one organic compound that forms a minimum azeotrope with anisole, methanol, water, and water, and whose azeotropic point is higher than the boiling point of the azeotrope of anisole and water. The present invention relates to a method for separating anisole in a mixture consisting of:

Water and anisole have low mutual solubility, and this mixture can be almost completely separated into oil and water into anisole and water at temperatures below 80°C. However, when methanol is added to this system, their mutual solubility increases. For example, if anisole is less than 10% by weight and methanol is more than 55% by weight, a homogeneous solution is formed, making oil-water separation impossible. Therefore, separating anisole from such a three-component system requires a separation operation such as distillation, and requires complicated equipment.

In the case of a three-component system of anisole, water and methanol, it is possible to isolate nisole by subjecting the liquid after methanol has been removed by distillation to an oil-water separation operation, but it is possible to isolate nisole using a normal industrial reaction product liquid. , such as the reaction product from the catalytic alkylation of phenols or anisole with methanol.
Valuable components are often mixed in the fourth or higher component (hereinafter this part will be collectively referred to as the fourth component, and a mixture containing the fourth or higher component in the above three-component mixture will be referred to as a four-component system). . In particular, if one of these valuable components forms the lowest azeotrope with water, anisole also forms an azeotrope with water, so even if you simply distill it, the fourth component will be mixed with anisole and water from the top of the column. If this were a homogeneous solution, it would be impossible to separate the anisole by oil/water separation. Furthermore, even if oil-water separation is possible, there are many difficulties in separating anisole, such as the need for complicated wastewater treatment if the fourth component is soluble in water. Also, for example, 4 above
Even if water in a liquid obtained by removing methanol from the component system by distillation can be separated from toluene by azeotropic distillation, it is necessary to further separate the alcohol. That is, in order to separate anisole from the above-mentioned four-component system, at least three separation operations are required.

An object of the present invention is to provide an improved method by which anisole can be easily separated from the four-component system.

A further object of the present invention is to provide a method in which anisole in the four-component system can be separated by only one continuous distillation operation and one oil-water separation operation.

The method of the present invention is characterized by subjecting the four-component mixed liquid to continuous distillation to separate methanol as an overhead liquid, and producing a liquid with a methanol/water weight ratio of 4 or less in the distillation column concentration section. The purpose is to take out the side stream liquid and separate the oil and water from this side stream liquid to obtain anisole.

The present inventors investigated various methods for efficiently separating anisole from a four-component system having the above-mentioned problems, discovered the following facts, and arrived at the present invention. That is, the amount and azeotropic temperature of water in the azeotropic mixtures of water-anisole, water-phenol and water-orthocresol at normal pressure are 40.5% by weight and 95.5°C, 90.8% by weight and 99.5°C and 88% by weight, respectively. Although it is considered extremely difficult to separate anisole from phenol or cresol in the presence of water at 99°C, the concentration distribution of each component in the column concentration section is as shown below. If multiple side stream liquid extraction ports are installed in the lateral stream, side cuts are made from a location where the anisole concentration is high and the methanol concentration is low depending on the operating conditions, and the obtained side stream liquid is cooled and oil/water is separated, anisole and anisole can be separated. It has been found that water separation can be carried out.

Regarding the concentration distribution of each of the above components, although there is some variation depending on the distillation operating conditions, high-purity methanol is accumulated in the upper quarter of the column from the top of the concentrating section, and in the lower part. Now, the methanol concentration is rapidly decreasing. On the other hand, anisole has a low concentration in the upper and lower parts of the column concentration section (near the supply section), but is concentrated to a high concentration in the middle section.
Water is hardly detected at the top of the tower, but it becomes highly concentrated by the middle part, and from then on it is distributed at an almost constant concentration until the bottom of the tower. In addition, the concentration of phenol or orthocresol decreases rapidly above the feed section, and at about 3/4 of the column concentration section from the top of the column,
Almost non-existent. That is, despite the fact that anisole, phenol, or orthocresol independently forms an azeotrope with water under almost the same conditions, in the above four-component system, water is highly concentrated in the middle part and below of the concentration section of the methanol distillation column. It has become clear that there are areas where almost no phenol or orthocresol is present, even though phenol or orthocresol is present. The reason for this is unknown, but it is presumed that the normal azeotrope composition has changed because the vapor partial pressure of methanol is relatively high in the concentration section.

In this way, anisole has a high concentration while methanol has a low concentration in the middle of the concentration section, so by extracting this liquid as a side stream and cooling it, phenol or orthocresol can be extracted. Anisole can be separated from water by oil-water separation without substantially containing it.

Even if the fourth component is an organic compound other than phenol and orthocresol, and its azeotropic temperature is higher than the boiling point of the azeotropic mixture of water and anisole, demethanol is performed by distillation to ensure good separation of anisole and water. I was able to achieve this.

Examples of organic compounds used in the present invention that form the lowest azeotrope with water and whose azeotropic point is higher than the boiling point of the azeotrope of anisole and water include phenols, cresols, xylenols, 2, aliphatic and aromatic alcohols such as 3-dichloro-1-propanol, heptanol, benzyl alcohol and their derivatives;
These include amine compounds and their derivatives such as aniline, N-ethylaniline, and tributylamine, acids such as crotonic acid and valeric acid, esters such as ethyl benzoate and dimethyl phthalate, and nitrobenzene, acetophenone, and nicotine. The higher the content of water in the azeotropic mixture of these compounds with water, the easier they are to be separated, and those having an azeotropic composition of 80% by weight or more of water are particularly preferred.

For continuous distillation in the present invention, ordinary pressure, reduced pressure, or pressurized distillation equipment can be used. There is no particular restriction on the concentration of the four-component system serving as the feed liquid, but the anisole concentration is preferably 0.05% by weight or more. If it is less than this, a distillation column with an extremely high number of plates is required to clearly separate the high concentration part of anisole and the low concentration part of methanol, or it is necessary to reflux an extremely large amount of methanol. In addition, in the side cut method, since the appropriate extraction section differs depending on the operating conditions, an extraction section is provided in each distillation stage (or equivalent part) from 1/4 to 3/4 from the top of the column concentrating section. It is best to select a withdrawal section that provides a side stream liquid from which the liquid after cooling can be separated into oil and water and from which as much anisole as possible can be separated.

The conditions that enable oil-water separation in the present invention are as follows:
Most of the methanol and the fourth component are almost completely removed by the distillation operation, so methanol,
Judgment may be made based on the mutual solubility of the 3-component system of water and anisole. Specifically, if the anisole concentration is 50% by weight, the methanol/water weight ratio is 4 or less; if the anisole concentration is 10% or more, the methanol/water weight ratio is 1.5 or less, and the anisole concentration is 1% by weight or more. If the weight ratio of methanol/water is 3/7 or less, and the following conditions are satisfied, anisole is separated from the three-component system of anisole, water, and methanol by oil-water separation.

The temperature for oil/water separation varies depending on the composition of the three-component system, but is generally 90°C or lower, preferably 60°C or lower. The oil/water separation operation can be carried out under increased pressure or reduced pressure, if necessary.

The four-component system used is one derived from a gas-phase catalytic alkylation reaction product of phenol with methanol. However, the method of the present invention is not limited to this, and can be applied to all four-component systems that satisfy the above conditions.

According to the present invention, anisole can be easily isolated from the four-component system. That is, anisole can be isolated from the four-component system simply by one continuous distillation operation and one oil-water separation operation.

The present invention will be further explained by showing examples below.

In the examples, percentages are by weight.

Example 1 Using a perforated plate distillation column with an inner diameter of 208 mm and 60 plates, methanol 15%, water 10%, anisole 0.13
A homogeneous solution consisting of 0.87% phenol, 6% orthocresol and 68% 2,6-dimethylphenol was fed from the top of the column to the 37th stage at 84 kg/hr.
Demethanol distillation was performed. The column top pressure was atmospheric pressure and the distillation rate was 12.5 Kg/hr to obtain methanol with a purity of 99.4%. The side cut was made at the 20th stage from the top of the tower, using 37% methanol, 35% water, and anisole.
A 28% composition liquid could be extracted at a rate of 0.35Kg/hr. Other components were 0.01% or less. 40% of this liquid
Upon cooling to 0.degree. C., two-phase separation occurred and 95% pure anisole was separated. The separation rate with respect to the anisole fed to the distillation column was 78%.

Example 2 Methanol 31.7%, water 47.5%, anisole 4.1
%, orthocresol 14%, metacresol 2%
The mixed liquid of 0.7% of 2,4-dimethylphenol was a heterogeneous liquid with a trace amount of oil layer at room temperature, but this was subjected to demethynol distillation in the distillation column of Example 1. Methanol with a purity of 99.5% was obtained from the top of the column by feeding it from the top of the column to the 37th stage at a feed rate of 84 kg/hr. Side cut is performed at the 25th stage from the top of the tower, and 15% methanol, 45% water and anisole are used.
A 40% solution was withdrawn at 8.56 Kg/hr. Other ingredients are
It was less than 0.01%. This liquid was cooled to 40°C and separated into oil and water, allowing anisole to be separated with a purity of 98%. The recovery rate for the amount of anisole fed to the distillation column reached 98%.

Example 3 Methanol 39.2%, water 28.6%, anisole 3.6
%, benzyl alcohol 10%, dimethyl phthalate
A mixed solution of 10% and 8.6% nicotine, diameter 25
mm, and was supplied at a rate of 100 g/hr to the 25th stage from the top of a 45-stage glass-made older-style distillation column. The pressure at the top of the column was normal pressure, and methanol with a purity of 99.2% was obtained from the top of the column.

A side cut was made at the 17th stage from the top to obtain a solution containing 49% methanol, 28% water, and 23% anisole. The fourth component, benzene alcohol, was 0.02%, and the other components were 0.01% or less. This liquid
Upon cooling to 25° C., two phases were separated and 90% pure anisole was separated. The separation rate of anisole based on the amount of anisole supplied was 52%. The loss of pendyl alcohol was less than 0.03%.

Comparative Example 1 Methanol distillation was carried out in the same manner as in Example 1 using the same distillation column and solution of the same composition without side cutting. The raw material liquid was supplied to the 37th stage at 84 kg/hr. 99.6% pure methanol from the top of the tower at 12.65%
Obtained in Kg/hr. The amount of anisole mixed in was less than 0.01%, and the other impurity was water.

The bottom liquid from which methanol had been removed was distilled again using the above-mentioned distillation column. Although the top liquid was mostly water, almost all of the anisole and phenol supplied and a trace amount of orthocresol were dissolved, and it was not possible to separate them.

Comparative Example 2 When the bottom residue from which methanol was removed in the first distillation operation of Comparative Example 1 was distilled again in the above distillation column, toluene was supplied to the first stage at the top of the column and azeotropic distillation was carried out. Got water and toluene. Although highly pure water could be separated by oil-water separation of this fraction, anisole could not be separated because it was dissolved in toluene, and a further separation operation was required.

Claims (1)

[Scope of Claims] 1 Consists of at least one organic compound that forms the lowest azeotrope with anisole, methanol, water, and water, and whose azeotropic point is higher than the boiling point of the azeotrope of anisole and water. When anisole in the mixture is separated, methanol is continuously distilled and separated from the mixture as a column top liquid, and a liquid having a methanol/water weight ratio of 4 or less is taken out as a stream liquid in the distillation column concentration section. A method for separating anisole, which comprises obtaining anisole by separating a side stream liquid into oil and water. 2. The method according to claim 1, wherein the organic compound is phenol, cresols and/or dimethylphenols.