JPS63190849A - Collection of 1,4-naphthoquinone - Google Patents

Abstract

PURPOSE:To collect 1,4-naphthoquinone efficiently in bringing a formed hot gas obtained by catalytic vapor phase oxidation of naphthalene with molecular oxygen-containing gas, by suppressing remarkable foaming by the use of a Venturi scrubber. CONSTITUTION:In collecting 1,4-naphthoquinone useful as a raw material for dye, etc., by bringing a formed hot gas containing 1,4-naphthoquinone obtained by catalytic vapor phase oxidation of naphthalene with molecular oxygen- containing gas, phthalic anhydride and an unreacted raw material into contact with water, the contact of the formed hot gas and water is carried out by a Venturi scrubber 1 to collect the aimed compound in high collection efficiency without causing remarkable foaming. Since an ordinarily useful Venturi scrubber can be utilized,the method is simply performed and operating conditions can be readily controlled. Further there is no demerits such as danger followed by use of organic solvent, bad influence on environment, cost, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a product containing 1,4-naphthoquinone, phthalic anhydride and unreacted naphthalene obtained by catalytic gas phase oxidation of naphthalene with a molecular oxygen-containing gas. from hot gas,
The present invention relates to a method for efficiently collecting 1.4-naphthoquinone.

(Prior Art) 1.4-Naphthoquinone is useful as a raw material for the synthesis of dyes and organic compounds.

1.4-Naphthoquinones are generally produced by catalytic gas phase oxidation of naphthalene with a molecular oxygen-containing gas in a fixed bed or fluidized bed, and the catalysts used in this process include vanadium pentoxide, alkali metal sulfates and It is well known that a catalyst component comprising an alkali metal pyrosulfate and optionally other metal oxides is supported on a carrier such as silicic acid or diatomaceous earth. Naphthalene is usually mixed with air or other molecular oxygen-containing gas at a ratio of 1vo1% or less and is supplied to the catalyst layer at a high temperature of 350° C. or higher.

In the above method, the oxidized hot gas released from the catalyst layer is generally
In addition to the produced 1,4-naphthoquinone, it is a mixed gas containing a large amount of phthalic anhydride and a small amount of unreacted naphthalene in a gas such as air.

Since 1.4-naphthoquinone is an unstable substance and tends to decompose or polymerize if kept in solution for a long time, it is necessary to carefully collect 1.4-naphthoquinone from the hot gas produced by oxidation.

Methods that have been proposed so far for collecting 1.4-naphthoquinone can be roughly divided into methods in which 1.4-naphthoquinone is absorbed by contacting IL+ generated gas with an organic solvent;
and (2) there is a method in which 1,4-naphthoquinone is precipitated in water by contacting the generated gas with water and recovered in the form of a slurry.

Among these, the collection method using organic solvent (11) brings the organic solvent into contact with high-temperature oxidation generated hot gas, so
If the generated gas is cooled to avoid the dangers of fire and explosion, the reaction products will adhere to the pipes and cause problems such as pipe blockages. Furthermore, the use of organic solvents is undesirable in terms of air pollution and deterioration of the working environment, as well as complicating wastewater treatment and the cost of the solvent.

Japanese Unexamined Patent Application Publication No. 51-98254 is available! A method for collecting 1,4-naphthoquinone by contacting it with a liquid mixture of a solvent and water is disclosed. According to this method, 1.4
- Naphthoquinone and naphthalene are collected in the organic solvent layer, and phthalic anhydride is collected in the water layer, and the collection rate of 1,4-naphthoquinone is relatively good. However, since this method also uses an organic solvent, although there is no danger of fire or explosion, it is not free from the drawbacks due to the use of organic solvents described above.

As a method of collecting 1,4-naphthoquinone from the hot gas produced by oxidation using water, there are known methods of bubbling the gas into water or injecting or spraying water onto the gas. For example, JP-A-47-177407 discloses a method for obtaining a slurry containing naphthoquinone, phthalic acid, and naphthalene by washing the generated gas with water.

Such a method using water as the collection medium avoids the above-mentioned problems associated with the use of Ia solvents, and also
．． Since 4-naphthoquinone is relatively stable in the form of a slurry in water, it can be said to be an advantageous method. However, the problem with the collection method by contact with water is that the collection efficiency is low (generally, the maximum collection rate for 1,4-naphthoquinone is about 98%
% or less), the foaming of the produced slurry is severe, and as the slurry concentration of the collecting liquid increases to 5 to 10% by weight, defoaming becomes difficult, and the collecting liquid overflows from the apparatus due to flooding. This remarkable foaming that causes flounding occurs not only when contact with water is carried out by bubbling, but also when a contact method is adopted in which water is sprayed or injected from a spray tower (Tokuko Kokō 5).
(See Column 3, Lines 1 to 8 of Publication No. 3-20024).

In order to avoid this foaming, in the method described in Japanese Patent Publication No. 53-20024, an aqueous slurry having a slurry concentration of 3 to 30% in which 3 to 20% of maleic acid has been dissolved is brought into contact with the generated gas. - Collection of naphthoquinone and phthalic anhydride. However, contact with a slurry containing such a large amount of acid components adversely affects the purity of the 1,4-naphthoquinone recovered from the collection liquid.

(Problems to be Solved by the Invention) Therefore, it is an object of the present invention to produce significant foaming from the hot gas produced by catalytic gas phase oxidation of naphthalene with an oxygen-containing gas, using water as a collection medium. An object of the present invention is to provide a method for collecting 1,4-naphthoquinone, which can collect 1,4-naphthoquinone with high collection efficiency.

(Means for Solving the Problems) As a result of repeated studies on the method of contacting the hot gas produced by oxidation with water, the present inventors discovered that when the produced gas is brought into contact with water using a Pentier scrubber, Even though the water comes into contact with the gas in the form of droplets as in a spray tower, foaming is minimized and flooding does not occur, and the collection efficiency of 1,4-naphthoquinone is also lower than that of a conventional spray tower or bubbling. It was found that this method was superior to the previous method.

In this regard, the present invention provides 1,4-naphthoquinone obtained by catalytic gas phase oxidation of naphthalene with a molecular oxygen-containing gas,
A method for collecting 1,4-naphthoquinone by contacting a hot mixed gas containing phthalic anhydride and unreacted naphthalene with water, characterized in that the hot mixed gas and water are brought into contact with a Venturi scrubber. , 1.4-
This is a method for collecting naphthoquinone.

(Operation) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The gas treated in the method of the invention is a high temperature mixed gas produced by catalytic gas phase oxidation of naphthalene with a molecular oxygen-containing gas. This generated hot gas generally has a temperature of 350°C or higher, and contains the generated 1,4-naphthoquinone and phthalic anhydride as well as unreacted naphthalene in the molecular oxygen-containing gas (usually air) used in the reaction. It usually also contains small amounts of by-products such as maleic anhydride.

When using a catalyst consisting of a mixture mainly consisting of vanadium pentoxide, alkali metal sulfate, and alkali metal pyrosulfate, which exhibits high activity for this catalytic gas phase oxidation reaction,
The generated gas is, for example, 15g7No? It contains the above 1,4-naphthoquinone, 20 g/Nrrr or more of phthalic anhydride, and a much smaller amount of unreacted naphthalene and by-produced maleic anhydride.

In the method of the present invention, the hot gas generated from the catalytic gas phase oxidation reaction of naphthalene is introduced into a venturi scrubber and brought into contact with water. Venturi scrubbers have conventionally been used as high-performance cleaning dust collectors to collect dust in gases, but are not generally used for the purpose of collecting gaseous components as in the present invention. Unexpectedly, it has been found that when a Venturi scrubber is used to bring the generated hot gas into contact with water, 1,4-naphthoquinone in the gas can be collected very efficiently.

A variety of venturi scrubbers for dust collection can be utilized in the method of the present invention. A schematic diagram of the pentier scrubber is shown in the attached drawing.

In the venturi scrubber 1 shown in the attached drawing,
The oxidized hot gas containing 1.4-naphthoquinone is introduced into the Venturi scrubber through the Venturi tube 2. Before this hot gas is introduced into the Venturi scrubber, it is cooled by appropriate means such as a heat exchanger so that the temperature at the venturi scrubber reaches about 50 to 200°C. The purpose of this cooling is to recover waste heat. If the gas temperature is lower than 50°C, tar-like substances are likely to adhere to the piping (and there is a risk of piping blockage, etc.).The flow of the introduced hot gas is accelerated in the throat section 3 of the Venturi scrubber. .

At the throat of the Hencherry scrubber, water is injected from path 4 toward the gas stream, and the water is atomized into droplets by the action of the accelerated, high-speed gas stream. On the other hand, the hot gas stream is cooled by contact with water, and the components contained therein, such as 1,4-naphthoquinone, phthalic anhydride, and naphthalene, precipitate or dissolve in water and are collected in water droplets. be done.

The exhaust gas from which the contained components have been collected is exhausted from the exhaust port 5. On the other hand, the droplets that have collected the components in the gas accumulate at the bottom of the Venturi scrubber and become slurry, which is passed through the path 6.
be extracted from.

In carrying out the method of the present invention, the optimal operating conditions of the venturi scrubber to obtain a high collection efficiency of 1,4-naphthoquinone vary depending on factors such as the type of equipment used and the temperature and composition of the introduced gas and water. However, for example, it is preferable to adopt the following conditions.

Gas velocity at throat: 0-130 m/sec Water/gas ratio: 0.3-1.511 Nrd Gas pressure loss: 400-500 mm1 (20 bench area)
The slurry discharged from the scrubber contains 1,4-naphthoquinone, phthalic anhydride, unreacted naphthalene, and small amounts of other by-products (such as maleic anhydride). 1,4-naphthoquinone can be separated from this slurry by known methods. For example, when an alkali is added to this slurry, phthalic anhydride and maleic anhydride are dissolved and removed in water, and the resulting filter cake is fluidized and heated to remove naphthalene, 1,4-naphthoquinone is left as a residue. can get.

After removing each component from the slurry, the water still containing small amounts of components can be recycled as part of the water feed to the Venturi scrubber.

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

A catalyst formed into a pellet shape with a diameter of 5 dragons and a length of 5 cranes having the following composition: Vt, Kt + sSz + FetSns, *5 tib was placed in a stainless steel reaction tube with an inner diameter of 30 m at 1000 cc.
Filled. This catalyst layer has a purity of 95% and a sulfur content of 0.
Catalytic gas phase oxidation of naphthalene was performed for 100 hours by flowing a naphthalene/air mixed gas containing 7% by weight of naphthalene in air at a temperature of 420°C. The naphthalene content in the mixed gas was 0.7 volX, and the mixed gas was supplied at a space velocity of 1650 hr.

The product gas contained 17 g of naphthoquinone in INr/24 g of phthalic anhydride, 0.4 g of maleic anhydride, and 0.4 g of unreacted naphthalene. This generated gas was cooled to 180°C and introduced into a vertical venturi scrubber. The operating conditions of the Pentieri scrubber were as follows.

Water/gas ratio: 0.5 J/Nn? Gas velocity at throat: 3Q m/sec Gas pressure loss 7
470111H! 0 Water used was tap water at room temperature. The exhaust gas discharged from the Pentieri scrubber is 0.2g/Nn? naphthoquinone and 0.2g/Nn
The naphthoquinone collection rate was 98.9%. During operation of the Venturi scrubber, no significant foaming of the liquid was observed.

(Effect of the invention) The method of the present invention provides the following effects.

■ Significant foaming, which was a drawback of the conventional method using water as a collection medium, can be avoided.

(2) A higher collection efficiency of 1,4-naphthoquinone can be achieved compared to the conventional collection method of bubbling water or water spraying.

■It can be easily implemented by simply using a conventional Venturi scrubber as a collection device, and the operating conditions can be easily controlled.

■Since no organic solvent is used, there are no disadvantages such as danger, negative impact on the environment, or cost associated with the use of aN agents.

[Brief explanation of the drawing]

The accompanying drawing is a schematic diagram of one example of a Venturi scrubber that can be used in the method of the invention. 1 Pentier scrubber 2 Venturi tube 3 Throat part 4 Water supply route 5 Exhaust port 6 Slurry discharge route

Claims (1)

[Claims] (1) 1,4-naphthoquinone obtained by catalytic gas phase oxidation of naphthalene with a molecular oxygen-containing gas, a hot gas containing phthalic anhydride and unreacted naphthalene is brought into contact with water to produce 1,4-naphthoquinone. A method for collecting 1,4-naphthoquinone, characterized in that the hot gas produced is brought into contact with water using a ventilate scrubber.