JPS5815935A - Preparation of benzaldehyde - Google Patents

Abstract

PURPOSE:To obtain a benzaldehyde continuously in a very short time, by hydrolyzing a benzal chloride which may be substituted by a halogen or CF3, in the vapor phase in the presence of an inexpensive active carbon treated with an acid as a catalyst. CONSTITUTION:A benzal chloride expressed by formulaI(X is halogen or CF3; n is 0, 1 or 2) in the vapor phase is hydrolyzed in the presence of active carbon treated with an acid, e.g. sulfuric acid, as a catalyst to prepare a benzaldehyde expressed by formula II. The catalyst is capable of advancing the hydrolysis in a very short time even in the case of the benzal chloride having a strong electron attractive group, e.g. CF3, as a raw material , and the activity thereof is not deteriorated by hydrogen fluoride generated by the hydrolysis of part of the CF3. Thus, the activity can be maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for producing benzaldehydes useful as raw materials, and more specifically, a method for producing benzaldehydes useful as raw materials, and more specifically, hydrolysis of penzal chlorides substituted or unsubstituted with halogen atoms or trifluoromethyl groups. The present invention relates to a method for producing hesaldehydes.

In general, if penzal chlorides are simply mixed with water and heated, the rate of hydrolysis to benzaldehydes is slow, so conventionally, various catalysts have been used to hydrolyze penzal chlorides to produce benzaldehydes. method is known.

For example, (1) a method for producing benzaldehyde compounds by hydrolyzing henzal chloride using an acid or alkaline aqueous solution [Organic S
inthesis) Collective Volume 1, page 155, Analytica Chemiriki Acta (Analytica
Chimica Acta) vol 4
0, P4ro], (2) A method for producing benzaldehyde by hydrolyzing penzal chloride in the presence of cuprous chloride or cupric chloride (Japanese Patent Publication No. 46-792-7)
(No. 51-6'l29), (3) An aqueous solution of iron salts in benzal chlorides? A method for producing benzaldehydes by adding and hydrolyzing (
(4) A method for producing benzaldehydes by hydrolyzing he/zalchlorides in the presence of anhydrous zinc chloride (Japanese Patent Publication No. 5B-766);
5) There is a method of producing benzaldehydes by hydrolyzing benzal chlorides in the presence of zinc oxide (Japanese Unexamined Patent Publication No. 52-257 Roro).

However, the above method has the following drawbacks.

The method (1) using an aqueous acid or alkali solution is likely to cause side reactions and has little effect on benzal chlorides having an electron-withdrawing group such as a trifluoromethyl group. In addition, when this method is carried out industrially, a considerably large reaction vessel is required for the raw materials, and treatment of waste alkali or waste acid is troublesome.

(21, (3), (4) methods using metal salts as catalysts generally have a slow reaction rate, especially in the case of benzal chlorides having electron-withdrawing groups, and the catalyst amount is increased by 2. and side reactions such as polymerization reactions increase.

Is the method using zinc oxide as a catalyst in (5) trifluoro-substituted benzal chloride? When used as a raw material, not only does the reaction hardly proceed, but it also involves a step of separating zinc oxide and the reaction product, making it unsuitable for continuous reaction methods.

As described above, the conventional methods have drawbacks such as generation of by-products, low container efficiency, inability to perform continuous processing, post-treatment of reaction residues, and extremely slow reaction rate for trifluoro-substituted benzal chlorides. Therefore, it is difficult to say that it is an industrially suitable method.

In addition to the above hydrolysis in the liquid phase, silicon dioxide or aluminum oxide alone, or cupric chloride or cupric chloride? A method of hydrolyzing benzal chlorides in the gas phase using a supported catalyst has been proposed (
Japanese Patent Publication No. 48-5755).

However, although this method is suitable for continuous processing, the initial reaction rate is extremely slow, especially when benzal chlorides with strong electron-withdrawing groups such as trifluoromethyl groups are used as raw materials, and the Silicon dioxide or aluminum oxide is fluorinated by the hydrogen fluoride produced as a by-product when a portion undergoes hydrolysis, and the activity further decreases rapidly, so that it cannot be applied to trifluoromethyl group-substituted benzal chlorides at all.

The present inventors have demonstrated the ability to produce benzyloldehydes that can be reacted in an extremely short time even when benzylchlorides having strong electron-withdrawing groups such as trifluoromethyl groups are used as raw materials, and that can be processed continuously. As a result of extensive research into the method, it was discovered that this object could be achieved by using activated carbon treated with an acid such as sulfuric acid as a catalyst, leading to the present invention.

That is, the present invention hydrolyzes benzal chlorides represented by the general formula (X represents a halogen atom or a trifluoromethyl group 2, and n = 01112 k) in the gas phase in the presence of acid-treated activated carbon. The present invention relates to a method for producing benzaldehydes, characterized by producing benzaldehydes represented by the general formula (X and n are as described above).

The present invention uses acid-treated activated carbon as a catalyst, and examples of this acid include fluorine, phosphoric acid, etc., and these acids exhibit catalytic activity in the form of being adsorbed and supported on activated carbon.
Good results can be obtained. Furthermore, this reaction is a gas phase reaction, and the reaction takes place at a temperature of approximately 200°C, although it depends on the type of benzal chloride used as the raw material. Therefore, it is more preferable to select an acid whose boiling point is higher than the reaction temperature. ,
An example of this is sulfuric acid;
Sulfuric acid is said to be the most preferable acid from the viewpoint of ease of handling. Activated carbon catalysts treated with such acids show extremely high activity in hydrolysis, and can be hydrolyzed in an extremely short time even when benzal chlorides, which have strong electron-withdrawing groups such as trifluoromethyl groups, are used as raw materials. Allow the decomposition to proceed,
Moreover, the reaction can be carried out continuously, and the activity can be maintained for a long period of time. That is, the acid-treated activated carbon catalyst of the present invention maintains extremely high activity for a long period of time without decreasing its activity even by hydrogen fluoride generated by hydrolysis of a portion of the trifluoromethyl group.

Furthermore, the activated carbon used in the present invention is not particularly limited in its type, shape, particle size, etc., and may be any commonly used commercially available activated carbon. Acid treatment is not particularly limited as long as the activated carbon surface is sufficiently immersed in VC acid. For example, when using sulfuric acid, a high sulfuric acid concentration is preferable in terms of surface activity, and generally 95% by weight or more. The immersion temperature and time are not particularly limited, and a range from room temperature to the boiling point depending on the sulfuric acid concentration used for several hours is sufficient. The acid-treated activated carbon is washed with water to make it easier to handle, dried at about 80 to ion°C, and then subjected to the reaction.

Typical benzal chlorides used in the present invention include benzal chloride, 0-2m-, or p-chlorobenzal chloride, o + m + '' or p-brombenzal chloride, o-, m- , or p
-fluorobenzal chloride, o-, m-, or p
-) Lifluoromethylbenzal chloride, 2,4-dichlorobenzal chloride, 2,5-dichlorobenzal chloride, 2,6-dichlorobenzal chloride, 2
, 4-dibromobenzal chloride, 2,5-dibromobenzal chloride, 2,6-dibromobenzal chloride and the like.

Next, a case in which the present invention is carried out in a continuous manner using activated carbon treated with sulfuric acid as a catalyst will be described in more detail.

First, water and raw material benzal chloride are sent into a heated vaporizer stationary using a metering pump and vaporized. The temperature in this case need only be above the boiling point of the benzal chloride used, and should be within a temperature range that allows the gas phase to be maintained throughout the reaction and at the same time does not allow the sulfuric acid supported on the activated carbon to vaporize and escape. It is efficient and the temperature can be determined in this way. Generally 200-5
Water and benzal chloride are fed into the vaporizer heated to 00'C as described above, and the heated rain-sound mixture gas is heated. This gas mixture is passed through a packed bed of sulfuric acid-treated activated carbon catalyst heated to 160-200'C, and contacted with the catalyst to cause a hydrolysis reaction. In this continuous process, the molar ratio of Henzal chloride to water vapor used is preferably approximately 1 mole of water vapor per -C,HCl2 group, but usually 5 to 1 mole.
The water vapor has a 0-fold molar excess, and the velocity passing through the catalyst packed bed is (L, )(, s, v, (liquid hourly space velocity), which is 0.
．． The reaction time is preferably from +5 to +5 hr', and the reaction time is usually several seconds to several tens of seconds, preferably about 2 seconds to 20 seconds. The generated benzaldehydes and unreacted water vapor are cooled and condensed by a cooler at the bottom of the reaction tube and stored in a receiver.

Most of the benzaldehydes continuously produced in this way are obtained in a state separated from water, but some aldehydes are obtained in a state suspended in water. In the latter case, it can be isolated by extraction with a suitable organic solvent, and further purified by vacuum distillation.

As described above, the present invention makes it possible to continuously produce benzaldehydes over a long period of time by a gas phase method using an extremely inexpensive catalyst called acid-treated activated carbon. It is an industrial product that shows high activity against benzal chlorides, which have strong electron-withdrawing groups, which were thought to be difficult to absorb, and is not easily affected by hydrogen fluoride due to hydrolysis of a part of the trifluoromethyl group. This is an excellent method.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Water was added at 0.57 i/min to a vaporizer heated to 250°C.
0.65 benzal chloride! Each metering pump was used at a rate of J/min. A gas mixture of vaporized benzal chloride and water vapor was heated to 180°C in a catalyst packed bed (
4 to 10 meshes of activated carbon were immersed in 95% concentrated sulfuric acid at room temperature for 2 hours, washed with water, and air-dried at 80° C. for 5 hours, followed by introduction of 25 M (filling with 25M) K and contact reaction. The generated gas was cooled in a cooler, and the resulting suspension was extracted with ether. After drying, the ether was distilled off, and vacuum distillation was performed under a nitrogen stream.

When benzalchloride i 0ag was continuously reacted in the manner described above, no tar by-product was observed, and benzaldehyde 64. Oji was obtained. The yield of product was 97.2% of theory.

Example 2 Id a, 21 g/min was continuously vaporized in a vaporizer at 250 °C, and a catalyst packed bed at 200 °C (4 to 10 meshes of activated carbon was immersed in 95% sulfuric acid at 150 °C for 5 hours). , then washed with water and air-dried at 100°C for 5 hours.
(filling) to react.

In this way, m-chlorhensal chloride 100! As a result of continuous reaction of j, 69.1 g of m-chlorobenzaldehyde was obtained. The product yield was 96.2% of theory. In this case as well, no tar by-product was observed.

Example 2 0-trifluoromethylbenzal chloride was supplied under the same conditions as in Example 2, except that the supply rate was 0.26 g/min of fluoromethylbenzal chloride and 9 g/min of water. As a result of continuous hydrolysis of 10gTh of chloride, 71.0 g of 0-trifluoromethylbenzaldehyde was obtained. The yield of product was 95.5% of theory. Note that the boiling point of the product was 82-b. Also, no tar by-product was observed in this case.

Comparative Example 1 o-)') Fluoromethylbenzal chloride 0.
γ-k120550 m calcined at 400°C for 5 hours as a catalyst with a water supply rate of 0°18g/min for 2391 minutes.
The reaction was carried out continuously under the same conditions as in Example 5 except that 1 was charged. The conversion rate of 0-trifluoromethylbenzal chloride in this case was about 25% after 1 hour and about 5% after 6 hours.

Comparative example 2 0-trifluoromethylbenzal chloride o, 2sE
/min, water o, +8,97 min supply rate, 4~ as catalyst
Example 6 except that 10 meshes of untreated activated carbon was used.
It was made to react continuously with 0-trifluoromethylbenzal chloride 1oo9 under the same conditions as above. The conversion rate of 0-trifluoromethylbenzal chloride in this case is 1.
In case 5, the conversion rate was slightly higher at 54.7%, but due to the high reaction humidity, phthalic acid was produced as a by-product.

Agent: 1) Akira Agent Ryo Hagi Hara -

Claims (1)

[Claims] In the presence of acid-treated activated carbon, a benzal chloride compound represented by the general formula (X represents a halogen atom or a trifluoromethyl group, and represents n.0.i, 2) is separated into a gas phase. 1. A method for producing benzaldehydes, which comprises producing benzaldehydes represented by the general formula (x and n are as described above) by hydrolysis.