JPH0468297B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention involves carrying out a gas phase contact reaction between phenol or/and orthocresol and methanol in the presence of a metal oxide to produce an ortho-methylated phenol compound. The present invention relates to a method for economically recovering phenol and ortho-methylated phenolic compounds from phenolic wastewater discharged from a manufacturing process.

Both the phenol and the ortho-methylated phenol compound recovered by the method of the present invention are useful as industrial raw materials. For example, phenol is a raw material for phenolic resins and cresols, and 2,6-xylenol is a raw material for polyphenylene ether and agricultural chemical ingredients.
- It is a raw material for xylidine, while orthocresol is useful as a raw material for medicines, agricultural chemicals, etc.

(Prior Art) A method for producing an ortho-methylated phenol compound by bringing phenol or/and orthocresol into contact with methanol in a gas phase is known and is practiced industrially.

This reaction is a reaction in which methylation produces water in the same molar amount as the methylation, and the mixture after the reaction is
Contains unreacted phenol, unreacted methanol, ortho-methylated phenol compounds, etc. It is necessary to discharge the water produced stoichiometrically from this mixture to the outside of the system, but normally water and methanol are separated from the phenols by distillation from the mixture after the above-mentioned reaction, and then water and methanol are separated from the phenols by distillation. Methods include separating methanol, or separating methanol from the mixture after the above reaction by distillation, separating phenols and water into two layers, and removing the aqueous layer from the system.

In any case, the water-phenol azeotropic condition is
The azeotropic conditions for water-2,6-xylenol are 90.8% by weight of water, azeotropic temperature of 99.5°C, and 88.5% by weight of water, and azeotropic temperature of 99°C. Orthocresol 2.2
% by weight and 0.6% by weight of 2,6-xylenol, it is extremely difficult to separate phenols from water, and normally the produced wastewater discharged outside the system will contain a small amount of phenols. The phenols contained in this wastewater are extremely expensive;
Furthermore, phenol is regulated by the Water Pollution Control Law, and the regulated concentration is actually very strict.

Conventionally, combustion incineration treatment, activated sludge treatment, solvent extraction method, and adsorption method are generally known as methods for treating phenolic wastewater.

Methods for recovering industrially useful phenols include solvent extraction and adsorption methods. Although it is possible to recover phenols using the solvent extraction method, the wastewater after the phenols have been recovered is It is not economical because some of the solvent remains and requires activated sludge or incineration treatment, and some of the solvent is also distributed to the wastewater side, making it necessary to replenish the solvent.

On the other hand, adsorption methods include adsorption with resin and adsorption with activated carbon.Resin adsorption methods are not economical due to the high cost of replenishing the resin due to the use of expensive resins. The activated carbon adsorption method is based on two points: how to regenerate activated carbon that has adsorbed phenol;
What is important is how much the performance of the regenerated activated carbon is recovered. Currently, the heating regeneration method is widely used as a method for regenerating activated carbon, and other methods include alkali regeneration and solvent regeneration. According to JP-A No. 51-54895, the regeneration rate (adsorption amount of recycled coal/adsorption amount of new coal) is low in the low-temperature heating regeneration method that uses steam at 120 to 150°C, and that In the thermal regeneration method, there is a large loss of expensive activated carbon due to the water gasification reaction, and the amount of equipment required increases significantly, making it uneconomical. In addition, the regeneration method using alkali requires complicated operations and poses a problem in alkali treatment after extraction.

An experimental example of the solvent regeneration method was presented at the 18th Autumn Conference of the Japan Chemical Industry Association SH-317 (1984). The best regeneration rate (regenerated coal adsorption amount/new coal adsorption amount) was 89% ethanol, and the worst was 69% methanol.
In addition, when examining the influence of the number of regenerations of ethanol recycled coal, the regeneration rate was 80% after four regenerations. In addition, in an experimental example at the 19th Autumn Conference of the Japan Association of Chemical Engineers SG-317 (1985), the regeneration rate of ethanol for various adsorbates was investigated, and in the case of sodium anthraquinone-2-sulfonate, the regeneration rate was 40%.

As mentioned above, the problem with the solvent regeneration method is that the regeneration rate of activated carbon is low. In particular, when methanol is used, the regeneration rate is 69% the first time, and when used repeatedly, the regeneration rate is extremely low, making it uneconomical. In addition, in the case of adsorption of sodium anthraquinone-2-sulfonate, the regeneration rate with ethanol is as low as 40%, and depending on the adsorbent, it is judged that the regeneration rate will be extremely reduced in the case of methanol regeneration. There must be.

Furthermore, there have been no concrete experimental examples of application to phenol-containing wastewater, and the activated carbon adsorption method by regenerating solvents such as methanol has remained an unestablished industrial field.

(Problems to be Solved by the Invention) As mentioned above, in the conventional technology, an aqueous solution of phenol, which is a simple mixture of phenol itself and water, was adsorbed on activated carbon and regenerated using a methanol solvent. However, the regeneration rate was low and was not at a level that was industrially satisfactory.

(Means for Solving the Problems) The present inventors have proposed a method for producing an ortho-methylated phenol compound by carrying out a gas phase contact reaction between phenol or/and orthocresol and methanol in the presence of a metal oxide. When we recovered phenols and/or ortho-methylated phenolic compounds from phenol-containing wastewater discharged from manufacturing processes, we were surprised to find that the regeneration rate of activated carbon was greatly improved, making it easier to use. It was found that it could be used continuously without deteriorating.

The present invention was made based on the above findings, and includes a method for producing an ortho-methylated phenol compound by carrying out a gas phase contact reaction of phenol or/and orthocresol and methanol in the presence of a metal oxide. This is a method for recovering phenol and/or ortho-methylated phenol compounds, which is characterized by adsorbing phenol-containing wastewater discharged from a manufacturing process with activated carbon, and then desorbing the adsorbed substance using methanol.

The catalyst applied to the present invention has, as a metal component,
Iron, vanadium, manganese, magnesium, chromium, and indium may be used alone or in combination, and alkali metals, alkaline earth metals, rare earth metals, etc. may be added to these components.

2,6-xylenol or/in the present invention
and for the production of orthocresol, the molar ratio of methanol to phenol or/and orthocresol in the feedstock varies depending on the catalyst species, but ranges from 1:1 to 20. Further, water vapor or an inert gas can be introduced as necessary, but in the case of water vapor, the molar ratio to phenol and/or orthocresol is preferably 1:0 to 15.

The reaction temperature varies depending on the catalyst type, but is between 250 and 600℃.
A range of is preferred.

The reaction can be carried out at normal pressure, reduced pressure or increased pressure.

If the phenol-containing wastewater discharged from the manufacturing process of the ortho-methylated phenol compound contains a small amount of methanol, it is desirable to remove the methanol in advance by distillation or the like. By performing activated carbon adsorption after excluding methanol, the amount of adsorption of the active ingredients of phenol, orthocresol and 2,6-xylenol is increased, and it is economical, and depending on the discharge conditions after wastewater treatment. , due to reasons such as the need to reduce COD.

Methanol, phenol, 2,6-xylenol,
In addition to the useful components of orthocresol, it contains trace amounts of impurities. Examples of impurities include:
Examples include anisole, 2,4-xylenol, 2,5-xylenol, 2,4,6-trimethylphenol, formic acid, and acetic acid.

For activated carbon adsorption, fixed-bed or moving-bed equipment is usually employed. The activated carbon used is
Granular coal, crushed coal is selected. The amount of activated carbon relative to the amount of liquid passed is not particularly limited. When the amount of activated carbon is large, the amount of adsorption is naturally large, so the number of times the activated carbon is regenerated is reduced, but the adsorption equipment becomes larger. On the other hand, when the amount of activated carbon is small, the amount of adsorption is small and the number of times the activated carbon is regenerated increases, but the adsorption equipment becomes smaller and the number of adsorption and desorption operations increases. For example, when using a fixed bed method and processing by continuously switching between two columns, it is necessary to select an adsorption time that is longer than the regeneration time of activated carbon, but when using a fixed bed method and repeating adsorption and regeneration using one column, There is no need to particularly limit the adsorption time. The adsorption temperature and adsorption pressure during adsorption are normal temperature and normal pressure.

When desorbing with methanol, it is desirable to have a high methanol concentration in order to reduce the amount of methanol used. It is better to use a larger amount of methanol in view of the recovery rate of phenol, orthocresol, and 2,6-xylenol, but desorption takes time and attachment efficiency deteriorates. On the other hand, if the amount of methanol used is small, the desorption time will be short and the equipment efficiency will be increased.
The recovery rate of 6-xylenol decreases. The conditions for an economical amount of methanol with a recovery rate close to 100% are that the concentration of phenol, orthocresol, and 2,6-xylenol in the desorption solution is 1% by weight.
It is preferable that it is below.

Phenol, orthocresol and 2,6-
The demethanolized liquid containing xylenol is recycled to the process for producing orthocresol and 2,6-xylenol without performing a separation and concentration operation.

There are concerns when adsorbing phenolic wastewater containing many impurities discharged from the process of manufacturing ortho-cresol and 2,6-xylenol with activated carbon. When regeneration using a methanol solvent is repeated, the regeneration rate is extremely reduced due to the accumulation of impurities, and the activated carbon must be completely replaced, making it uneconomical.

However, when applied to wastewater from the above manufacturing process, the activated carbon regeneration rate was 90%, which is a significant improvement compared to conventional techniques, and does not deteriorate even after several hundred regenerations using methanol solvent. This phenomenon is presumed to be due to interaction between the multiple components of the phenol-containing wastewater, including phenol, orthocresol, 2,6-xylenol, and impurities.

(Effects of the Invention) In the present invention, phenol-containing wastewater discharged from the phenol or/and ortho-methylated phenol compound manufacturing process is adsorbed with activated carbon,
By desorbing using methanol solvent, the adsorption performance of activated carbon does not deteriorate even if the activated carbon is used repeatedly, and the regeneration rate is greatly improved to 90%.
Can be used continuously for a long time.

Furthermore, it is possible to recover nearly 100% of the useful components of phenol and/or ortho-methylated phenol compounds in phenol-containing wastewater, improving raw material efficiency, and since the treated water contains almost no phenol, it can be used as a secondary It has remarkable effects such as being able to be discharged into public waters without the need for treatment.

(Example) The present invention will be explained below with reference to Examples.

According to the flow sheet of FIG. 1, phenol and methanol are reacted in the presence of iron and vanadium metal oxides in the reactor 1, the reaction product is cooled in the heat exchanger 2, and the gas separation column 3 Methanol and water are passed through line 4 from the bottom of the column and separated by distillation in dehydration tower 5, and then distilled from the top of dehydration tower 5. Methanol and water are passed through line 6 and separated by distillation in methanol column 7. Line 8 for phenolic mixtures
is passed through to the next process. Phenol-containing wastewater containing phenol, orthocresol, 2,6-xylenol, and other cresol impurities is discharged from the bottom of the methanol column 7 through a line 9. Methanol contained in this wastewater was removed in a methanol distillation column 10.

After methanol removal, phenol-containing wastewater contains phenol, orthocresol, and 2,6
- Contained a total of 2.53% by weight of xylenol.
This wastewater is introduced into the fixed bed type activated carbon adsorption equipment 12 through line 11, and immediately before the phenols in the treated liquid in line 16 leak,
The liquid flowing from 1 was switched to activated carbon adsorption equipment 13 and discharged through line 16. Next, the phenol, orthocresol and 2,6
- Xylenol was desorbed through line 15.
When the concentration of desorbed methanol, that is, phenols in line 15, decreased to 6000 ppm, the flow of methanol through line 14 was stopped.

Next, immediately before the phenols in the line 16 via the activated carbon adsorption equipment 13 leaked, the system was switched to the activated carbon adsorption equipment 12 filled with the regenerated activated carbon, and the above operation was repeated 230 times.

By the above treatment method, the treated solution of phenol-containing wastewater had a phenol concentration of 1 to 2 ppm and was rendered harmless. Furthermore, the regeneration rate of activated carbon was 89% on average after the second activated carbon regeneration, and despite 230 repetitions, the regeneration rate did not drop economically at all.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing the manufacturing process of the example.

Claims (1)

[Claims] 1 In a method for producing an ortho-methylated phenolic compound by carrying out a gas phase contact reaction of phenol or/and orthocresol and methanol in the presence of a metal oxide, the phenol-containing wastewater discharged from the production process is subjected to activated carbon adsorption. A method for recovering phenol or/and ortho-methylated phenolic compounds, which comprises: desorbing the adsorbed substance using methanol.