JPH0564623B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing phenylacetaldehyde by isomerizing styrene oxide at high temperature in a reactor filled with a high-boiling organic solvent in which a catalyst is suspended. It is related to.

Phenylacetaldehyde is used in agricultural medicines, fragrances,
It is an important compound as an intermediate for artificial sweeteners, and demand for it has been increasing in recent years.

(Prior Art and its Problems) Conventionally, the following various routes have been proposed for this manufacturing method.

a Styrene oxidation b Isomerization of styrene oxide c Dehydration of styrene glycol d Phenylethyl alcohol oxidation e Decomposition of phenyl glycide ester, etc. are known. However, in the above-mentioned conventional methods, there are many problems industrially because phenylacetaldehyde is highly reactive and is easily changed by oxidation, polymerization, etc. A production method using isomerization of styrene oxide has been proposed which improves these problems.

For example, JP 52-3913, JP 59-141534,
JP-A No. 59-144727, etc., and it is produced by a gas phase fixed bed reaction using a special catalyst at high temperature.

However, in these methods, highly reactive phenylacetaldehyde is produced through a gas-solid catalytic reaction at high temperatures, so polymers etc. adhere to the catalyst surface and the catalyst activity deteriorates, so the reaction is interrupted and air is removed. etc., it is necessary to perform regeneration to burn off the polymer, which requires complicated operations. In addition, since the reaction product also contains polymers or is colored, purification by distillation or the like is required, resulting in loss of phenylacetaldehyde during purification.

According to Japanese Patent Publication No. 49-25932, phenylacetaldehyde is obtained by isomerizing styrene oxide by suspending activated clay as a catalyst in liquid paraffin. With this method, the distillate may be colored yellow-green or some of the polymer or heating medium may be distilled out, so it is necessary to take measures such as purifying the distillate, and during this process the reactivity may be reduced. This is not an industrially satisfactory method as it has the disadvantage of loss due to polymerization of phenylacetaldehyde.

(Means for Solving the Problems) The present inventors have conducted intensive studies on methods for producing highly pure phenylacetaldehyde without coloration by suppressing the polymerization loss of highly reactive phenylacetaldehyde. The inventors have discovered that the problem can be solved and have arrived at the present invention. That is, the present invention has the following features: 1. (A) Styrene oxide is supplied in gas or liquid form from the bottom of the reactor to a reactor filled with a high-boiling organic solvent in which a catalyst is suspended, and (B) Starting materials are supplied under reduced pressure. (C) The reaction product is reacted to a conversion rate of 99.5% or more in a reaction system maintained at a temperature higher than the temperature at which the reaction product vaporizes, and (C) the reaction product is extracted through a distillation column directly connected to the reactor. A method for producing phenylacetaldehyde.

2. A part of the above-mentioned high-boiling organic solvent is continuously or intermittently withdrawn from the reaction system, and the corresponding regenerated or new solvent and catalyst are similarly replenished. This is the method described in Section 1.

The catalyst used in the present invention is not particularly limited as long as it can generally convert an epoxy compound into an aldehyde. Commonly used catalysts include solid acid catalysts such as synthetic silica-alumina, activated clay, alumina, silica-boria, silica-magnesia, or cobalt sulfate, sulfates such as nickel sulfate, and potassium aluminum sulfate, and acidic ion exchange. Examples include resin.

The high boiling point organic solvent is one having a boiling point at least higher than that of phenylacetaldehyde, preferably a high boiling point hydrocarbon having a boiling point of 250° C. or higher. For example, liquid paraffin, diethyl diphenyl (trade name Therm-S 700, a product of Nippon Steel Chemical Co., Ltd., the same applies hereinafter), triethyl diphenyl (trade name Therm-S
600) Hydrogenated triphenyl (trade name Therm-S)
900) etc.

As the reactor used in the present invention, a stirred tank type having a stirrer or an upright circular reaction tube without a stirrer can be used. Also, the styrene oxide is fed from the bottom of the reactor, ensuring sufficient transit time in the reaction zone. When charging this in gaseous form, it is also possible to install a vaporizer to vaporize it outside the reactor. It is advantageous to use a sparge ring or the like to improve the dispersibility of styrene oxide within the reactor. When it is applied in liquid form, it is also possible to entrain it with an inert gas such as nitrogen.

As the distillation column directly connected to the reactor, a bubble column, a perforated column, a packed column, etc. are used. The number of stages in the distillation column varies depending on the boiling point difference between the organic solvent used and the phenylacetaldehyde produced, but several stages are sufficient. Furthermore, since the reaction is almost complete with a raw material conversion rate of 99.5% or more, there is no unreacted styrene oxide in the reaction product gas, which promotes fractional distillation of by-product high-boiling substances and improves the product appearance (APHA). Inherit.

When carrying out the present invention, the reaction consists of suspending the catalyst in a high-boiling organic solvent, charging styrene oxide at a rate depending on the reaction rate, and distilling the generated phenylacetaldehyde out of the reaction system.

Usually, the following operating conditions are adopted. The catalyst concentration in the organic solvent varies depending on the type of catalyst, but
0.1-10% is appropriate. Reaction temperature is 160~220℃
is preferred. If the reaction temperature is high, polymers etc. will be produced and the catalyst life will be shortened, and if the reaction temperature is low, unreacted styrene oxide will be mixed in. The reaction pressure varies depending on the boiling point difference between the organic solvent used and phenylacetaldehyde, the reaction temperature, etc., but is generally 5.
A range of ~50 mmHg is preferred. The feed rate of raw material styrene oxide is supplied according to the reaction rate so that the conversion rate is 99.5% or more, but there are also changes in the reaction temperature, pressure, type of catalyst, concentration, etc. It should be determined appropriately by experiment, since it depends on the allowable amount.

The resulting phenylacetaldehyde does not require any further purification such as distillation, has high purity without coloring, and has sufficient commercial value.

In addition, when renewing the organic solvent and catalyst in the present invention, if the organic solvent is contaminated with polymers such as phenylacetaldehyde or catalyst deterioration occurs, the reaction must be stopped and restarted by replacing them. A solvent purified by a continuous method, or by continuously extracting a portion of the solvent and catalyst from the reaction system while continuing the reaction, and converting the degraded catalyst into an organic solvent from which it has been separated, or by distilling the separated organic solvent, etc. It can be carried out in a continuous manner by adding fresh catalyst back to the reactor. However, a continuous method of operation is advantageous.

(Example) Next, the present invention will be specifically described with reference to Examples.

Reference Example (Catalyst Preparation) 120 g of Aerosil 380 (silica gel manufactured by Nippon Aerosil Co., Ltd.) is suspended in 1.2 g of water. Separately, 80 g of Cataloid AP (manufactured by Catalyst Chemical Industry Co., Ltd., alumina content 67%) was added to 400 ml of water and suspended to obtain an alumina sol. The obtained alumina sol was added to the silica gel suspension solution while stirring, and then a 14% ammonia aqueous solution was added until the pH reached 7.2 to obtain a slurry. After drying this slurry at 150°C, it was calcined at 500°C for 2 hours and pulverized to obtain a catalyst. (composition, 31%
Al ₂ O ₃ −69%SiO ₂ ) Example 1 (See Figure 1) Cylindrical reactor 4 with a length of 500 mmH and an inner diameter of 45 mmφ
300 g of liquid paraffin and 10 g of the catalyst obtained above were charged in advance, and heated to 180° C. under a reduced pressure of 10 mmHg while being forcibly stirred via a circulation pump 8. Then, styrene oxide was added at a rate of 30 g/hour.
The raw material was vaporized in a vaporizer 3 via a feed pump 2 from a raw material container 1 and then continuously supplied. The generated phenylacetaldehyde was passed through a perforated plate distillation column 5 with five stages and an inner diameter of 35 mm, which was attached to the upper part of the reactor, and was continuously distilled into a product container 7 via a condenser 6 at a reflux ratio of 0.5. (Reaction time was 58 hours) During this period, the total amount of raw materials charged was 1785 g, and the total distilled amount of products was 1650 g.

As a result, the concentration of phenylacetaldehyde in the distillate was 98.6%, and unreacted styrene oxide was not detected. The hue of the distillation rate was colorless and ApHA10. (Styrene oxide conversion rate 99.8%, phenylacetaldehyde yield 92.5%) Comparative Example A reaction was carried out for 54 hours using the same catalyst and the same reaction conditions as in Example 1, except that only the distillation column section was removed. During this period, the total amount of raw materials charged was 1616g, and the total amount of product distilled was
It weighed 1521g.

As a result, the concentration of phenylacetaldehyde in the distillate was 98.5%, and unreacted styrene oxide was not detected. The color of the distillate was yellow-green and ApHA50.

Example 2 (See Figure 1) Reactor with length 2000mmH and inner diameter 1500mmφ and length
The reaction was carried out for 75 hours under the same reaction conditions as in Example 1, except that a packed column of 2000 mmH and an inner diameter of 450 mmφ was used, and the following changes were made: 700 kg of liquid paraffin, 50 kg of catalyst, and a feed rate of 100 kg/hr.

Then, the organic solvent containing the catalyst is added every hour.
It was extracted at a rate of 16.5 kg, and the catalyst and by-product high-boiling substances were separated from liquid paraffin using a separator 9. Then, add 3.5 kg of recovered liquid paraffin to 3.5 kg of new liquid paraffin corresponding to the separated amount and 0.5 kg of new catalyst.
was replenished into the reactor every hour. (Reaction time was 25 hours) As a result, the composition of the distillate was 98.5% phenylacetaldehyde, 0.2% unreacted styrene oxide, and the remaining 1.3%, and the color of the distillate was colorless and ApHA10.
It was hot.

[Brief explanation of drawings]

FIG. 1 is a system diagram schematically showing an example of an apparatus for carrying out the method of the present invention. In the figure, 1...raw material container, 2...preparation pump, 3
... vaporizer, 4 ... reactor, 5 ... distillation column, 6 ...
... Condenser, 7 ... Product container, 8 ... Circulation pump,
9... Liquid separator.

Claims (1)

[Claims] 1 (A) Styrene oxide is supplied in gaseous or liquid form from the bottom of the reactor to a reactor filled with a high-boiling organic solvent in which a catalyst is suspended, (B) Starting under reduced pressure The raw material conversion rate is maintained within the reaction system at a temperature higher than that at which the raw materials and reaction products vaporize.
React to 99.5% or more, (C) and pass through a distillation tower directly connected to the reactor.
A method for producing phenylacetaldehyde, which comprises removing a reaction product. 2. A part of the above-mentioned high-boiling organic solvent is continuously or intermittently withdrawn from the reaction system, and the corresponding regenerated or new solvent and catalyst are similarly replenished. The method described in Section 1.