JPH047335B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for collecting quinones from a high temperature mixed gas containing quinones such as anthraquinone and naphthoquinone. Specifically, the present invention relates to a method for collecting quinones as crystals using an aqueous medium from a high-temperature mixed gas containing quinones produced by catalytic gas phase oxidation or a high-temperature mixed gas containing a carrier gas produced by sublimation. .

Conventionally, anthraquinone is anthracene, 1-
It is produced by catalytic gas phase oxidation of methyl-3-phenylindane, ortopenzyltoluene, diphenylmethane, etc. with a molecular oxygen-containing gas. Naphthoquinone is also produced by catalytic gas phase oxidation of naphthalene with a molecular oxygen-containing gas. In such a gas phase oxidation reaction, quinones are obtained as a high temperature mixed gas, so it is necessary to collect the quinones from the mixed gas. Furthermore, when anthraquinone or naphthoquinone is purified by sublimation, it is necessary to collect quinones from the gas containing these quinones generated together with the transport gas.

Conventionally, when separating and collecting quinones from a high-temperature mixed gas containing such quinones,
Industrially, there are indirect cooling methods in which crystals are formed on the wall of the cooler by cooling the high-temperature mixed gas by leaving it to cool or forced cooling, and direct cooling methods in which cold gas or cold liquid is introduced into the high-temperature mixed gas to bring it into gas-liquid contact. Cooling methods are being used.

However, the collection method using indirect cooling method is
In order to remove the crystallized crystals, it is important to stop the equipment and scrape off the crystals that have formed on the wall of the cooler.
Alternatively, it is necessary to stop the process, heat it, melt it, and take it out, which has the disadvantage that if you want to collect it continuously, you have to alternately switch between at least two cooling devices to cool and take it out. . Furthermore, the scraping method requires a great deal of labor and equipment, which is economically disadvantageous, and when carried out manually, it causes hygiene problems.
On the other hand, with the heat melting method, high melting point (287°C) like anthraquinone requires heating and melting with a high temperature heat medium, resulting in large energy loss, and due to its nature, naphthoquinone tends to polymerize and deteriorate when melted. Therefore, it is difficult to apply.

On the other hand, the direct cooling collection method using cold gas or cold liquid has the problem of not only the collection rate of the target object but also difficult problems in recovering or processing the cold gas or cold liquid. The difficulty increases as the concentration of quinones in the hot gas mixture decreases.

On the other hand, in order to collect quinones from a high-temperature mixed gas, methods have been proposed that use water or an aqueous medium, which is inexpensive and easy to recover or treat. Since this is a method of spraying an aqueous medium in the form of raindrops or film, the high-temperature mixed gas is rapidly cooled, and the water-insoluble quinones are turned into extremely fine particles and atomized. The atomized quinone particles float in the gas of the device, and their collection is extremely difficult due to the nature of the atomized material, and cannot be collected by economical methods.

In order to solve this problem of atomization, the quinones are introduced into a condenser with walls that are kept below the precipitation temperature of the quinones and have an aqueous medium flowing down so as to thinly cover the walls, and the quinones are condensed. A collection method by depositing on the wall of a vessel has been proposed (Japanese Patent Application Laid-open No. 66571/1983). However, in this method, there is a large temperature difference between the dew point of the quinones in the high-temperature mixed gas and the water or aqueous medium.
Crystals of quinones crystallize at the point of contact between the high-temperature mixed gas and water or an aqueous medium in the collection device, and grow into lumps, clogging the device and causing problems such as degrading the quality of quinones. It is not easy to collect quinones stably and efficiently.

The present invention was made in order to eliminate the various drawbacks of the conventional methods as described above, and it is possible to heat a high-temperature mixed gas containing quinones selected from the group consisting of anthraquinone and naphthoquinone to the dew point or 100°C below the dew point. The mixed gas is introduced into a wet wall column formed of water or an aqueous medium at a high temperature, and heat exchange is performed with the high temperature mixed gas and water or an aqueous medium to lower the temperature of the high temperature mixed gas below the dew point. A method for recovering quinones, which comprises introducing quinones into a washing tower and bringing them into contact with water or an aqueous medium to collect the quinones, and recovering the quinones as a slurry from the bottom of the wet wall tower and the washing tower. It is.

That is, the present invention introduces a hot mixed gas stream containing quinones into a wetted wall tower formed of water or an aqueous medium, and after heat exchange between the hot mixed gas and water or an aqueous medium, The goal is to collect quinones in water or an aqueous medium.

The advantage of the wet wall column in the present invention is that, firstly, when high-temperature mixed gas is heat exchanged with water or an aqueous medium, the temperature of the high-temperature mixed gas gradually decreases, resulting in the growth of crystallized crystals. There is almost no atomization, and collection can be easily carried out. In other words, when water or an aqueous medium is sprayed onto a high-temperature mixed gas in the form of raindrops or a film, the high-temperature mixed gas comes into direct contact with the low-temperature water or aqueous medium in a short period of time, resulting in a rapid drop in the mixed gas temperature. However, the crystallized crystals remain fine and become atomized, making collection difficult. However, according to the present invention, crystals of quinones that can be collected are obtained.

The second advantage is that the inside of the wet wall column is covered with fluid water or an aqueous medium, so crystals such as quinones do not precipitate or settle on the wall surface of the vessel. Since it is continuously carried out of the wet wall tower together with the aqueous medium, it can be operated continuously.

The third advantage is that a considerable distance and space can be provided between the hot mixed gas inlet and the cold water or aqueous medium. Crystals do not precipitate at the supply port and make operations difficult.

The fourth advantage is that since it is a wet wall tower, it has good heat exchange efficiency and the apparatus can be made smaller compared to an air-cooled crystallizer.

Although the shape of the wet wall tower used in the present invention is not particularly limited, it is desirable to have a structure in which the water or aqueous medium forming the wet wall does not form raindrops or mist. In addition, the size of the wetted wall tower can be appropriately determined depending on the amount and characteristics of the high-temperature mixed gas introduced, as long as it can cool the high-temperature mixed gas to the temperature at which crystals are precipitated. .

Examples of the high temperature mixed gas containing quinones introduced into the wet wall tower include anthracene, 1-
An anthraquinone-containing mixed gas which is a product of a catalytic gas phase oxidation reaction using a molecular oxygen-containing gas such as methyl-3-phenylindane, orthobenzyltoluene, or diphenylmethane, and a catalytic gas-phase oxidation reaction product of naphthalene using a molecular oxygen-containing gas. There are naphthoquinone-containing mixed gases, anthraquinones, or mixed gases using an inert gas such as nitrogen during sublimation purification of naphthoquinones as a carrier gas, and particularly preferred are anthraquinone-containing mixed gases, which are the products of the catalytic gas-phase oxidation reaction. Such a high temperature mixed gas is introduced into the wetted wall tower at a temperature higher than the dew point of the mixed gas, taking into account blockages in gas flow pipes, precipitation of crystals at the wetted wall inlet, etc. The column is a crystallizer, and considering the separation operation of the collected quinones, the temperature should be as close to the dew point as possible, and 100℃ below the dew point.
A high temperature, preferably about 20°C higher than the dew point, is suitable.

Water or aqueous media forming wet walls include:
In addition to water such as pure water, tap water, and industrial water, water containing chemicals and surfactants used to improve the quality of collected quinones, aqueous slurry containing collected quinones, and In the case of a separated liquid obtained by separating collected quinones or a quinone-containing gas during gas phase air oxidation, it may be water to which a chemical for suppressing the precipitation of by-products has been added.

The temperature of the water or aqueous medium is not particularly limited as long as it is in liquid form and flows through the container walls, but when using the water or aqueous medium in circulation, the calorific value of the high-temperature mixed gas and the evaporated water are released outside the system. Usually 40~
Operated at 60℃. The flow rate of water or aqueous medium is
The amount should cover the entire wall surface of the wetted wall tower, and is determined by the type of wetted wall tower and the amount of evaporation associated with heat exchange.

The temperature of the high-temperature mixed gas containing quinones is lowered in the wet wall tower, and the quinones contained therein crystallize. Although some of the crystallized solids are collected by the water or aqueous medium flowing down the wet wall column, the majority remains in the gas mixture and is brought into contact with the water or aqueous medium in the washing column. When the quinone-containing gas that has passed through the wet wall column comes into contact with water or an aqueous medium in the form of raindrops or spray, the quinones no longer become atomized and can be easily collected.

Next, one embodiment of the present invention will be described with reference to the drawings. That is, a high-temperature mixed gas containing quinones is passed through a line 3 at the top of a wet wall tower 2 to which water or an aqueous medium is supplied near the top by a nozzle 1.
will be introduced. The high temperature mixed gas introduced is
While passing through the wet wall tower 2, it contacts the film-like water or aqueous medium that forms the wet wall and exchanges heat, and the temperature decreases while crystallizing a portion of the quinones. Collected within a film of media.
As a result, the slurry produced is transferred from the bottom of the column to line 4.
The solid-liquid separator 5 is then discharged. The heat-exchanged mixed gas is supplied to the bottom of the cleaning tower 7 through line 6, and while rising inside the tower, it is brought into countercurrent contact with water or an aqueous medium supplied from the tower top through shower nozzle 8, and the quinones are removed. be captured. As a result, the resulting slurry is discharged from the bottom of the tower through line 9 to solid-liquid separator 5. Note that the exhaust gas is discharged from the top of the tower through line 10 to the outside of the system. Note that the contact between the water or the aqueous medium and the mixed gas may be a cocurrent contact.

The solid and liquid are separated in the solid-liquid separator 5, and water-insoluble quinones are passed through the line 11 as a solid.
is discharged from. The separated liquid is supplied via line 12 to wet wall column 2 and washing column 7. Further, a portion of the liquid is discharged from the system through line 13. Note that water or an aqueous medium is replenished into the liquid in line 12 from line 14 . Also,
The liquid in line 12 may contain line 15 if necessary.
From there, a drug is added to adjust the fluidity. When the quinone-containing mixed gas is a catalytic gas phase oxidation product gas, such agents may be used to lower the pH of water or an aqueous medium to 4 to prevent the precipitation of by-product organic acids.
-8, preferably 4-6, alkalis such as sodium hydroxide and potassium hydroxide are preferred.

Next, the present invention will be explained in more detail by giving examples.

Example 1 A stainless steel pipe with an inner diameter of 160 mm and a height of 1000 mm.
A wet wall tower in which an anthraquinone separated liquid is flowing down at a rate of 4/min as an aqueous medium, and an anthraquinone separated liquid flowing from the top with a wetted wall tower of the same shape connected to this column at a rate of 6/min.
A washing tower was used with a circular all-over spray nozzle emitting water at 1/min.

Anthraquinone-containing gas at 450° C. was obtained by catalytic gas phase oxidation of anthracene with air in an oxidation reactor in an amount of 14 m ³ /hr (standard conditions).
This mixed gas stream contained 389 g/hr of anthraquinone,
It contained 11 g/hr of phthalic anhydride, 4 g/hr of benzoic acid, 5 g/hr of maleic anhydride, and 2 g/hr of 2,3-naphthalene dicarboxylic acid, and trace amounts of unidentified by-products. This anthraquinone-containing gas is
The heat was recovered, the temperature was adjusted to 230°C, and the mixture was introduced into the wet wall tower and then passed through the washing tower. The solids collected in the wet wall column and washing column were recovered as a slurry in an aqueous medium. This slurry was separated into anthraquinone and an aqueous medium by flotation separation, and the anthraquinone was further washed with water and then dried. On the other hand, a part of the aqueous medium separated here was extracted from the system at a rate of about 130 g/hr in order to prevent the accumulation of oxidized by-products, and the remainder was recycled for use in the wet wall tower and washing tower. Approximately 10/hr of water is added to the circulating aqueous medium in order to make up for the lack of water contained in the outflow and exhaust gas, and the pH of the aqueous medium is adjusted to 4 to 6 in order to prevent the precipitation of by-product organic acids. 110g/hr of 25% sodium hydroxide aqueous solution to maintain
was supplied at the rate of Purity 99.3 after 72 hours of continuous operation
% anthraquinone 27.78Kg was obtained. The collection rate of anthraquinone is equivalent to 99.2%. The collection ratio between the wet wall tower and the washing tower was approximately 65:35.

Comparative Example 1 The same method as in Example 1 was carried out except that the wet wall tower was removed and two washing towers were used. Five hours and 30 minutes after the start of operation, the inlet for the anthraquinone-containing gas was blocked by anthraquinone crystal precipitation, making operation impossible. In addition, the exhaust gas was atomized. The amount collected in 4 hours was 1422 g, corresponding to a collection rate of 91.4%.

Example 2 A wet wall tower made of stainless steel pipe with an inner diameter of 70 mm and a height of 1500 mm, with water flowing down at a rate of 2.5/min,
A cleaning tower was used, which was connected to a stainless steel pipe with an inner diameter of 160 mm and a height of 1000 mm, and had a circular all-over spray nozzle from which water was spouted from the top at a rate of 6/min.

Melt anthraquinone by heating to 320℃, 10m ³ /
Through nitrogen gas in the amount of hr (standard conditions), 18.50
Anthraquinone was evaporated at a rate of Kg/hr to obtain an anthraquinone-containing gas. This anthraquinone-containing gas was introduced into a wet wall tower and then into a washing tower to collect anthraquinone at a rate of 18.38 Kg/hr.
This corresponds to a collection rate of 99.4%.

Comparative Example 2 In Example 2, two cleaning towers were used in succession, each of which was made of stainless steel pipe with an inner diameter of 160 mm and a height of 1000 mm, and had a circular all-over spray nozzle that spouted water from the top at a rate of 6/min. Except for this, the same method as in Example 2 was carried out. The amount of anthraquinone collected was 16.10 kg in 1 hour. Collection rate is 87.0
Corresponds to %.

Example 3 In an apparatus similar to Example 1, a naphthoquinone-containing gas obtained by catalytic gas phase oxidation of naphthalene with air in an oxidation reactor was used. The 10 m ³ /hr of naphthoquinone-containing gas (standard conditions) contained 116 g/hr of 1,4-naphthoquinone, 94 g/hr of phthalic anhydride, 28 g/hr of unreacted naphthalene and small amounts of oxidized by-products. After 48 hours of operation, 1,4-naphthoquinone was separated and dried to obtain 5490 g. The collection rate is equivalent to 98.6%.

Comparative Example 3 Anthraquinone-containing gas was collected in the same manner as in Example 1, except that the washing tower was removed and two wet wall towers were used. 1638 g of anthraquinone was obtained in 5 hours of operation. The collection rate of anthraquinone was equivalent to 84.2%.

[Brief explanation of drawings]

The drawing is a flow sheet illustrating one embodiment of the invention. 1... Nozzle, 2... Wet wall tower, 7... Washing tower, 8... Shower nozzle, 5... Solid-liquid separation device.

Claims (1)

[Claims] 1. A high-temperature mixed gas containing quinones selected from the group consisting of anthraquinone and naphthoquinone is heated at its dew point or at a temperature 100°C higher than the dew point,
The high-temperature mixed gas is introduced into a wet wall tower formed of water or an aqueous medium, and the temperature of the high-temperature mixed gas is lowered below the dew point by exchanging heat with the water or an aqueous medium, and then the mixed gas is washed. A method for recovering quinones, which comprises introducing the quinones into a column and collecting the quinones by contacting them with water or an aqueous medium, and recovering the quinones as a slurry from the bottoms of the wet wall column and the washing column. 2. The method for recovering quinones according to claim 1, wherein the aqueous medium is water. 3. The method for collecting quinones according to claim 1, wherein the aqueous medium is a liquid obtained by collecting the quinones and separating the quinones. 4. The method for collecting quinones according to claim 1, wherein the aqueous medium contains solid content generated by collecting quinones. 5. The method for collecting quinones according to any one of claims 1 to 4, wherein the water or aqueous medium has a pH of 4 to 8. 6. The method for collecting quinones according to any one of claims 1 to 5, wherein the quinone-containing mixed gas is a product gas obtained by a catalytic gas-phase oxidation reaction. 7. The method for collecting quinones according to any one of claims 1 to 5, wherein the quinone-containing mixed gas is a gas produced by heating and sublimating crude quinones. 8. The method for collecting quinones according to any one of claims 1 to 7, wherein the quinones are anthraquinones.