JPH0796550B2 - Method for producing naphthalic anhydride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for producing naphthalic anhydride useful as a dye intermediate or the like.

[Conventional technology]

Although naphthalic anhydride is industrially obtained by liquid phase oxidation of acenaphthene, this method is not only low in yield but also difficult to attain a purity of 95% or more. That is, since naphthalic anhydride decomposes near the boiling point and there are few suitable solvents that selectively dissolve it, it becomes difficult to purify it by distillation or recrystallization. Therefore, a process has been proposed in which impurities by-produced in the oxidation step are removed by multistage washing and then dried to increase the purity of phthalic anhydride, but the recovery rate of naphthalic anhydride is low and the process is complicated. There is a drawback that.

Further, Japanese Patent Publication No. 51-44714 discloses a method of producing naphthalic anhydride by catalytic gas phase oxidation of acenaphthene in the presence of an oxidation catalyst at a temperature of about 300 to 400 ° C.
However, there is no description in this document regarding the collection or purification of naphthalic anhydride.

A switch condenser type collector is known as a collector for a sublimable solid typified by phthalic anhydride (Japanese Patent Publication No. 58-44609, etc.), but in the case of naphthalic anhydride, the melting point is It cannot be used due to its high cost and its alteration on melting.

[Problems to be solved by the invention]

An object of the present invention is to produce naphthalic anhydride from acenaphthene in high yield and high purity.

[Means for solving problems]

The present invention, in the presence of an oxidation catalyst, at a temperature of 300 to 400 ° C.,
Catalytic gas phase oxidation of acenaphthene using air or a gas containing molecular oxygen to produce a gas stream of oxidation products containing naphthalic anhydride, followed by introduction of a cooling gas into this gas stream. Thus, it is a method for producing naphthalic anhydride, which is cooled to 30 to 150 ° C. to separate and collect naphthalic anhydride as a solid content.

The oxidation catalyst used in the present invention oxidizes acenaphthene to naphthalic anhydride, and specific examples thereof include a catalyst containing vanadium pentoxide as a main catalytically active component. As an example, titanium dioxide 70-90 wt%, V ₂ O ₅ 10-
Examples of the catalyst include 30 wt% and 0.5 to 5 wt% of an alkali metal compound (however, calculated as a sulfate) on which a non-porous inert carrier is supported.

The reaction conditions are such that naphthalic anhydride is produced,
It is advantageous that the unreacted acenaphthene in the oxidation product is 1 wt% or less, preferably 0.5 wt% or less.
However, if the reaction proceeds too much, maleic anhydride,
Since the side reaction products such as phthalic anhydride increase, it is advantageous to set the conditions such that the unreacted acenaphthene remains in an amount of 0.001 wt% or more, preferably 0.05 wt% or more. Such conditions are
Although it varies depending on the type of oxidation catalyst, in many cases, the temperature is in the range of 300 to 400 ° C., the space velocity is in the range of 1000 to 10000 hr ⁻¹ , and the acenaphthene concentration is in the range of ^{30 to} 80 g / m ³ −air. The raw material acenaphthene may be an acenaphthene-containing material, but it is preferably purified to some extent. When acenaphthene is recovered from coal tar, it contains a small amount of impurities such as diphenylene oxide, methylbiphenyl, dimethylnaphthalene, and biphenyl.
The presence of impurities of about 10 wt% does not matter. However, if the amount of impurities is large, the product yield decreases, so it is preferable to set the acenaphthene concentration to 95 wt% or more.

Since the gas flow of the oxidation product containing naphthalic anhydride, which leaves the reactor, maintains a temperature of around 300 to 400 ° C, a cooling gas is introduced into this gas so that the temperature is 30 to 150 ° C, preferably 50 Cool to ~ 100 ° C. Incidentally, before introducing the cooling gas, the gas flow may be indirectly cooled to a temperature at which crystals do not precipitate, for example, a temperature of 200 ° C. or higher, and by using such a cooling gas. The amount can be reduced. As the cooling gas, any gas may be used as long as it is a gas at room temperature and is inert to naphthalic anhydride, but air is advantageous. Further, as long as it becomes a gas after introduction, it may be a liquid at the time of introduction. Also,
The lower the temperature of this gas, the smaller the amount used, but it does not matter even if it is room temperature. If the temperature after quenching is too low, the adsorption of side reaction products such as phthalic anhydride, maleic anhydride, and naphthoquinone on naphthalic anhydride will increase, which not only lowers the purity but also causes water to condense and filter pressure. It causes increased loss and blockage. If the temperature after quenching is too high, the loss of naphthalic anhydride is large.

The amount of cooling gas used can be calculated. For example, when the air-cooling tower inlet temperature is 330 ° C. under the conditions of Example 1, the usage amount is as shown in Table 6. However, if there is cooling due to heat dissipation or indirect cooling, the value will be lower than this.

As an apparatus for introducing the cooling gas, an air cooling tower type apparatus is preferable. Examples of such an apparatus include a rotary flow type centrifugal solid separator (ROBERT H, PERRY / LECIL H CHILTON CH
EMICAL ENGINEER'S HAND BOOK (Fifth Edition) Chapter 20 P87
20-102) and the like. In a cooler that only cools from the side wall, naphthalic anhydride adheres to the side wall, making it difficult to take out.

By this rapid cooling, naphthalic anhydride is precipitated from the gas flow of the oxidation product. However, by-products benzoic acid, maleic anhydride, phthalic anhydride, naphthoquinone,
Since acenaphthylene or unreacted acenaphthene has a higher vapor pressure than naphthalic anhydride, it hardly deposits and is not adsorbed by solid naphthalic anhydride, and thus remains in the gas flow. Not only is the purity of the precipitated naphthalic anhydride high, but it is spherical and has a high density, so it is easy to collect.

The naphthalic anhydride powder that is rapidly cooled but is partly entrained in the gas flow is preferably collected by a filter such as a cross filter or a fiber layer filter. Here, the cross filter includes a screen type filter, a bag filter type and the like, and the fiber layer filter includes a reverse jet filter type and the like, all of which can be backwashed. Recently, materials for filters have been developed one after another. In addition to organic filters, there are metal, carbon, and ceraminek-made materials, but any material can be used as long as it is a reverse type filter.

Hereinafter, the present invention will be described in detail with reference to the drawings showing an example of the embodiment of the present invention.

The mixed gas of acenaphthene and air is fed from the tube 1 to the reactor 2
Be introduced to. From the reactor 2, a gas flow of an oxidation product containing naphthalic anhydride flows out from a pipe 3.

This gas flow is introduced into the air cooling tower 4 and rapidly cooled by the cooling gas supplied from the pipe 5. The precipitated naphthalic anhydride becomes powder and is extracted from the lower part of the air cooling tower 4.
The naphthalic anhydride entrained in the gas is sent from the pipe 5 to the bag filter 6, where the powder is collected. The collected powder is blown off intermittently for a short time by compressed air blown from the opposite direction, and is withdrawn from the lower part. The exhaust gas flowing out of the pipe 7 from the upper portion of the bag filter still contains by-products, so it is purified by washing with water or the like.

〔Example〕

A mixed gas consisting of acenaphthene and air is passed through a reactor filled with an oxidation catalyst, which is a porcelain carrier carrying catalytically active components consisting of 80 wt% TiO ₂ , 18 wt% V ₂ O ₅ and ₂ wt% Cs ₂ SO _4. Let Niter temperature of the reactor 325 ℃,
The concentration of acenaphthene was 40 g / Nm ³ -air, the space velocity was 3000 hr ^-1 , and the raw material acenaphthene shown in Table 1 was used.

The gas flow of the oxidation product flowing out of the reactor was inserted into the air cooling tower, and cooling air was introduced to quench the gas, and then the gas flow was introduced into the bag filter. The composition of the oxidation product is shown in Table 1.

The temperature of the gas flow from the reactor at the inlet of the air cooling tower is 20
The temperature of the cooling air was 0 ° C, and the temperature of the bag filter was adjusted by changing the amount of air blown into the cooling air. Note that the amount of cooling air used was in the range of 0.1 to 10 times the volume due to heat radiation from the device.

The results of Examples 1 to 3 are shown in Tables 2 to 4, respectively. Table 5 shows the relationship between the temperature at which the filter exits and the naphthalic anhydride collection rate in Example 1.

[Effects of the Invention] According to the production method of the present invention, highly purified naphthalic anhydride exceeding 95% can be obtained in a high yield without special purification of a distillation column.

[Brief description of drawings]

 The figure is a process flow of the present invention. 2 ... Reactor 4 ... Air cooling tower 6 ... Bag filter

Claims (2)

[Claims] 1. A gas of an oxidation product containing naphthalic anhydride by catalytically vapor-phase oxidizing acenaphthene using air or a gas containing molecular oxygen in the presence of an oxidation catalyst at a temperature of 300 to 400 ° C. Is produced, and then a cooling gas is introduced into the gas stream to rapidly cool it to 30 to 150 ° C., and naphthalic anhydride is separated and recovered as a solid content. Method for producing acid. 2. A gas stream of an oxidation product is subsequently introduced into an air cooling tower, a cooling gas is injected and cooled, and the cooled gas stream is discharged through a filter and deposited in the air cooling tower. The method for producing naphthalic anhydride according to claim 1, wherein the solid content collected and the solid content collected by the filter are recovered as naphthalic acid.