JPH04346954A - Recovery of phenols - Google Patents

Abstract

PURPOSE:To recover valuable phenolic compounds in high efficiency from waste water containing phenolic compounds and discharged in the production of o- cresol and 2,6-dimethylphenol by the vapor-phase catalytic reaction of phenol with methanol in the presence of a metal oxide. CONSTITUTION:Waste water containing phenols is made to contact with a styrene/divinylbenzene polymer based synthetic adsorbent to effect the adsorption of the phenols. The adsorbed phenols are desorbed and recovered with a desorbent such as methanol.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a useful method for producing o-cresol and 2,6-dimethylphenol from the wastewater discharged from the gas phase catalytic reaction of phenol and methanol in the presence of metal oxides. The present invention relates to a method for recovering phenols. Orthocresol and 2,6-xylenol are useful compounds as disinfectants and preservatives, and as raw materials for agricultural chemicals, medicines, phenolic resins, plasticizers, and the like.

0002

BACKGROUND OF THE INVENTION A method for producing ortho-methylated phenol by subjecting phenol and methanol to a gas-phase catalytic reaction in the presence of a metal oxide is known and is practiced industrially. In this reaction, water is produced in an amount equal to that of methylation, so the reaction product contains not only the target orthocresol and 2,6-dimethylphenol but also unreacted raw materials and water produced by the reaction.

The reaction product water needs to be discharged from the system, and the usual method is to separate the reaction product into a water and methanol system and phenols by distillation, and then to separate water and methanol by distillation. After methanol is separated by distillation, phenols and water are separated in two phases, or methanol, water, and phenols are separated in one column using a side-cut distillation method. Although the water (wastewater) obtained by separation contains a small amount of phenols, these are industrially useful as raw materials for various resins, and from the viewpoint of environmental issues, it is desirable to recover almost completely.

Conventionally, known methods for treating phenolic wastewater include incineration, activated sludge treatment, solvent extraction, and adsorption. Solvent extraction methods and adsorption methods are common methods for industrially recovering phenols. In the solvent extraction method, trace amounts of phenol remain in the wastewater after treatment, requiring further secondary treatment such as activated sludge treatment and incineration, and the solvent is also distributed into the wastewater and discharged. It is hard to say that it is a preferable method.

[0005] As a method for recovering phenols in wastewater produced in the process of producing methylphenols from the reaction of phenol and methanol by an adsorption treatment method, a method using activated carbon as an adsorbent is disclosed in JP-A-1-14.
It is disclosed in Japanese Patent No. 6838. However, the phenol-containing wastewater generated in this process contains trace amounts of organic acids such as formic acid and acetic acid, as well as impurities such as anisole and 2,4-dimethylphenol. was concentrated, and corrosion of the equipment material was a problem.

In order to prevent this, it is necessary to use expensive materials or to recycle and decompose the phenols containing organic acids into the reaction system, but the desorbed and recovered phenols contain a considerable amount of 2, Since it contains 6-xylenol, when it is recycled to the reaction system, a part of it becomes 2,
The drawback is that it is converted into by-products such as 4,6-trimethylphenol. Activated carbon also has a problem in that it has a low regeneration rate with solvents. Furthermore, when a packed tower is used as an adsorption device, there is a problem that during desorption of phenols, the desorbed phenols precipitate at the liquid-liquid interface between the desorption solvent and the wastewater remaining in the packed tower.

On the other hand, JP-A No. 51-34874 discloses a method for adsorbing and separating phenol by treating crude phenol wastewater (500 ppm of phenol) using poly(styrene/divinylbenzene) as an adsorbent. However, the same method is said to be applicable to aqueous solutions containing organic acids such as maleic acid.

[0008]

[Problems to be Solved by the Invention] An object of the present invention is to reduce the amount of gas emitted when producing ortho-cresol and 2,6-dimethylphenol by subjecting phenol and methanol to a gas phase catalytic reaction in the presence of metal oxides. The objective is to efficiently recover useful phenols from wastewater.

[0009]

[Means for Solving the Problems] The present invention provides a method for producing ortho-cresol and 2,6-dimethylphenol by subjecting phenol or/and ortho-cresol and methanol to a gas phase catalytic reaction in the presence of a metal oxide. A method for recovering phenols, which comprises bringing the discharged phenol-containing wastewater into contact with a styrene/divinylbenzene-based synthetic adsorbent to adsorb the phenols, and then desorbing and recovering the phenols using a desorbent. be.

[0010] The mixing ratio of phenol or/and orthocresol and methanol in the reaction process of the present invention is 1:1 to 1, depending on the desired production ratio of 2,6-xylenol and orthocresol to be produced. :20
, preferably in the range of 1:1 to 1:10. The catalyst used in this reaction is an oxide of iron, vanadium, manganese, chromium, indium, titanium, etc. alone or in combination as a metal component, and further contains an alkali metal, an alkaline earth metal, or a rare earth metal as a metal component. It may be used by adding oxides of metals, etc.

[0011] The reaction temperature is 300 to 450°C, and the reaction pressure is 1 to 10 kg/cm2G. The reaction liquid obtained in the above gas phase contact reaction is separated into methanol, water (wastewater) and phenols by one-stage or multi-stage distillation or phase separation. The phenols consist of phenol, ortho-cresol, 2,6-xylenol, and heavy substances, and are separated and purified by distillation or the like to obtain the desired ortho-methylated phenol. The obtained ortho-cresol is recycled to the reaction system and remethylated to produce 2,6-
Xylenol can also be produced.

The adsorbent used in the present invention is a copolymer resin of styrene and divinylbenzene, and although the composition is not limited, a resin having a degree of crosslinking of 20% or more is preferable. The shape of the adsorbent is also not particularly limited, but the diameter is 0.2 to 0.
．． Preferably, it is in the form of fine particles of 5 mm. Specifically, Amberlite XAD-4 manufactured by Rohm and Haas, etc. may be mentioned.

[0013] The adsorption method may be a fixed bed method or a moving bed method. The amount of adsorbent relative to the amount of liquid passed is not particularly limited. If the adsorbent filling amount is large, the number of times of regeneration will be reduced, but the adsorption equipment will be larger. Adsorption conditions are not particularly limited, but at a temperature of about 40 to 60°C, normal pressure to 10°C.
A pressure range of Kg/cm2 is suitable.

[0014] Examples of the desorbent used in the present invention include alcohols such as methanol, propanol, and butanol, and ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Alcohols are preferred, and methanol is particularly preferred because it is economical. It is optimal in terms of performance and effective use within the process.

That is, when methanol is used, the liquid after desorption treatment contains methanol and recovered phenol, orthocresol, 2,6-dimethylphenol, and other phenols, so it can be used as is. , 2,6-dimethylphenol, etc. can be recycled to the reaction system and used as a raw material. Also, if desired,
The recovered liquid can also be recycled to the distillation purification system.

[0016]

[Effect of the invention] According to the method of the present invention, the resin used as the adsorbent has a very high regeneration rate (ratio of the adsorption capacity of the regenerated adsorbent to the adsorption capacity of the new adsorbent), so it can be used continuously. Therefore, there is almost no resin replenishment cost, and organic acids such as formic acid and acetic acid are discharged without being accumulated, so the material of the adsorption treatment equipment can be made at low cost without considering corrosion caused by organic acids. material can be selected. Further, precipitation of phenols does not occur in the packed column, and the recovery rate of phenols is high with a small amount of desorbent.

[0017]

[Examples] The present invention will be explained in more detail with reference to Examples below. <Example 1> Water obtained by separating the reaction product obtained by subjecting phenol and methanol to a gas phase contact reaction in the presence of a metal oxide into methanol, water (wastewater), and phenols by distillation. (Wastewater) contains 1.8% by weight of phenols,
Methanol 0.35% by weight, formic acid 550ppm, acetic acid 5%
It contained 00 ppm. This is ROHM AND
Amberlight XAD-4 100c manufactured by HAAS
A column with an inner diameter of 15 mm was filled with C in a fixed bed at 40°C.
, which was circulated under normal pressure. Effluent phenol concentration is 50p
The adsorption capacity and amount of treated liquid were measured with the point at which the temperature reached pm as the breakthrough point. At the same time, the adsorption amounts of formic acid and acetic acid were also measured.

The adsorbent that had reached its breakthrough point was subjected to desorption regeneration treatment by passing methanol through it. The amount of methanol liquid until the concentration of phenols in the effluent during regeneration (regenerated liquid) became 50 ppm or less and the regeneration rate were measured. After adsorbing wastewater and regenerating with methanol, the adsorbent is passed through water to remove methanol, and then backwashed by flowing water from the bottom of the adsorbent packed bed to initialize the filled state of the adsorbent. returned to the state of The above operation was repeated. The results are shown in Table 1.

[0019] Here, adsorption capacity (g/l) = phenols (g)/
Amount of resin (l) Amount of methanol required for regeneration (l
/l)=methanol amount (l)/resin amount (l)
Regeneration rate (%) = (Adsorption capacity of regenerated adsorbent / Adsorption capacity of new adsorbent) × 100 Adsorption rate of organic acid (%) = (Amount of organic acid adsorbed / Amount of organic acid in wastewater) × It is 100.

<Comparative Example 1> The same procedure as in Example 1 was carried out using activated carbon (Diahope 008 manufactured by Mitsubishi Kasei Corporation, average particle size 1 mm) as the adsorbent and pure methanol as the desorbent. The results are shown in Table 1.

[0021]

[Table 1]

Claims (1)

[Claims] Claim 1: Waste water containing phenols discharged when producing ortho-cresol and 2,6-dimethylphenol by subjecting phenol or/and ortho-cresol and methanol to a gas phase catalytic reaction in the presence of a metal oxide. A method for recovering phenols, which comprises adsorbing the phenols by contacting them with a styrene/divinylbenzene-based synthetic adsorbent, and then desorbing and recovering them using a desorbent.