JPS64938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing α-acetoxy or propionyloxy-propionaldehyde by a hydroformylation reaction of vinyl acetate or vinyl propionate using a rhodium complex compound as the main catalyst. This reaction is shown by the following formula.

(R represents a methyl group or an ethyl group) α-acetoxy or propionyloxy-propionaldehyde is extremely useful industrially as a starting material for various organic synthesis reactions, including as a starting material in the production of lactic acid, lactic acid ester, threonine, etc. It is a compound.

It is already well known that α-acetoxy or propionyloxy-propionaldehyde can be produced in relatively high yields by the hydroformylation reaction of vinyl acetate or vinyl propionate catalyzed by a rhodium complex compound (for example, Publication No. 1575, J.Chem.Soc., (A)2753
(1970), Japanese Patent Application Laid-Open No. 143617). As is well known, rhodium complex compounds are extremely expensive, so when producing α-acetoxy or propionyloxy-propionaldehyde by hydroformylation of vinyl acetate or vinyl propionate on an industrial scale, it is difficult to use rhodium complex compounds from the reaction mixture. To efficiently separate the target product, α-acetoxy or propionyloxy-propionaldehyde, which is relatively unstable thermally and chemically, from the rhodium complex compound, and to circulate the catalyst while maintaining the catalytic activity of the rhodium complex compound. Reuse is particularly important from a technical standpoint. However, to date, there have been no research reports intended to solve these technical problems. Rather, conventionally known methods do not solve these technical problems at all. When separating α-acetoxy or propionyloxy-propionaldehyde from the hydroformylation reaction mixture, a distillation separation method has been used in the conventionally known method. A) α-
Acetoxy or propionyloxy-propionaldehyde causes undesirable side reactions such as decarboxylation, polycondensation, and oxidation reactions under distillation separation conditions; (b) repeated hydroformylation and distillation separation; As the number of cycles increases, there are problems such as a decrease in the catalytic activity of the rhodium complex compound that is recycled and an accumulation of high-boiling by-products, and the distillation separation method cannot be adopted industrially.

According to the present invention, vinyl acetate or vinyl propionate is hydroformylated with a mixed gas of hydrogen and carbon monoxide in the presence of a substantially water-insoluble rhodium complex compound and a trisubstituted phosphine in an organic solvent, By subjecting the reaction mixture obtained in step) to an extraction operation with an aqueous medium, α-acetoxy or propionyloxy-propionaldehyde is extracted and separated into an aqueous medium layer, and a raffinate layer containing the catalyst component obtained in step) is obtained. is circulated to the hydroformylation reaction step of step), and fractionated from the aqueous medium layer containing α-acetoxy or propionyloxy-propionaldehyde obtained in step) while keeping the temperature of the still distillate below 90°C. and obtaining α-acetoxy or propionyloxy-propionaldehyde. According to this method, not only α-acetoxy or propionyloxy-propionaldehyde is produced at a high reaction rate and high selectivity, but also the catalytic activity of the rhodium complex compound is stably maintained over a long period of time. Furthermore, during extraction, the loss of rhodium complex compounds and trisubstituted phosphine due to elution into the aqueous medium layer is extremely small, and it is possible to separate and obtain α-acetoxy or propionyloxy-propionaldehyde from the aqueous medium layer in high yield and purity. α-acetoxy or propionyloxy by hydroformylation reaction of vinyl acetate or vinyl propionate.
Propionaldehyde can be produced industrially advantageously.

Considering the balance between hydrophilicity and hydrophobicity assumed from the structural formula of α-acetoxy or propionyloxy-propionaldehyde, the above-mentioned aldehydes can be extracted extremely efficiently by the extraction operation of the hydroformylation reaction mixture with an aqueous medium as described above. Being separated is quite surprising.

In the method of the present invention, a substantially water-insoluble organic medium is used in consideration of the extraction step using an aqueous medium. There are many organic solvents that can be used, but the solubility of the catalyst components, loss of elution of the catalyst components into the aqueous medium layer, price, physical properties considering the subsequent separation process, and chemical Considering stability, hydroformylation reaction results, etc., aromatic hydrocarbons that may be substituted with lower alkyl groups, such as benzene, toluene, xylene, and ethylbenzene, and substituted or unsubstituted aromatic hydrocarbons, such as cyclohexane and methylcyclohexane, are used. Preferred examples include substituted saturated alicyclic hydrocarbons. Among these, benzene, toluene and xylene are particularly preferably used. As the rhodium complex compound, any rhodium complex compound that has hydroformylation catalytic ability under hydroformylation reaction conditions and is substantially insoluble in an aqueous medium can be used. Many such rhodium complex compounds are already known, and most of these conventionally known rhodium complex compounds can be used in the method of the present invention. Specifically, HRh(CO)(PA ₃ ) ₃ (A: aryl group), RhCl
(PA ₃ ) ₃ , Rh (acac) ₃ (acac: acetylacetonate group), Rh (OAc) ₃ (OAc: acetic acid group), Rh ₄ (CO) ₁₂ ,
Rh ₆ (CO) ₁₆ , [Rh (CO) ₂ (PA ₃ ) ₂ ] ₂ , RhCl ₃・
Examples include 3H ₂ O, Rh ₂ O ₃ , etc. Among these,
HRh(CO)(PA ₃ ) type ₃ rhodium complex compounds are particularly preferred from the viewpoints of catalytic activity, solubility, ease of handling, and the like. In addition, it is also possible to separately provide a catalyst adjustment tank, prepare the rhodium complex compound therein by a known method, and feed the resulting mixed solution as it is to the hydroformylation reaction tank to carry out the reaction. The rhodium complex compound is usually hydroformylation reaction solution 1
0.1-25 mmol per, more preferably 0.1
Used in a concentration range of ~10 mmol. If the concentration of the rhodium complex compound is less than 0.1 mmol per reaction solution, an industrially satisfactory reaction rate cannot be obtained;
The use of an unnecessarily high concentration of 25 mmol or more is disadvantageous from an economical point of view and also because the loss of elution of the rhodium complex compound into the aqueous medium layer during the extraction step (step) becomes large.

The trisubstituted phosphine used in step) in the process of the present invention has the general formula PR′R″, R(R′ and
R" represents an aromatic hydrocarbon group, and R represents an aromatic hydrocarbon group or a saturated aliphatic hydrocarbon group having 3 or more carbon atoms. Examples of such trisubstituted phosphine include triphenylphosphine, tritolyl Examples include substituted or unsubstituted triarylphosphines such as phosphine and trinaphthylphosphine, and diarylalkylphosphine such as diphenylpropylphosphine and diphenylhexylphosphine. Among these, substituted or unsubstituted triarylphosphines are particularly preferably used.According to the research of the present inventors,
The amount of trisubstituted phosphine used depends on the selectivity to α-acetoxy or propionyloxy-propionaldehyde, reaction rate, catalyst activity life, amount of rhodium eluted into the aqueous medium layer, and amount of trisubstituted phosphine eluted into the aqueous medium layer. etc., the selection rate,
Regarding the reaction rate and the amount of trisubstituted phosphine eluted into the aqueous medium layer, the smaller the amount of trisubstituted phosphine used, the better the catalyst activity life and the amount of rhodium eluted into the aqueous medium layer. A more favorable result can be obtained. As described above, trisubstituted phosphine has contradictory effects depending on the amount used, but when all these points are comprehensively judged from an industrial viewpoint, the desirable amount of trisubstituted phosphine used is approximately 5 to 50% per rhodium atom. The concentration is in the molar range, and more precisely, it is practical to use the concentration in the range of 10 to 150 mmol per hydroformylation reaction solution. There is no problem in using two or more trisubstituted phosphines in any combination.

In the method of the present invention, the hydroformylation reaction in step) is performed under the reaction conditions generally employed in conventional hydroformylation reactions, that is, the reaction temperature is 50°C.
The reaction can be carried out at ~120°C, a carbon monoxide partial pressure of 0.1-150 Kg/cm ² , and a reaction pressure of 0.5-200 Kg/cm ² . If the reaction temperature is less than 50°C, the reaction rate will be extremely slow, while if the reaction temperature exceeds 120°C, undesirable side reactions may occur. The higher the carbon monoxide partial pressure in the hydrogen/carbon monoxide mixed gas, the higher the selectivity to α-acetoxy or propionyloxy-propionaldehyde, but if the carbon monoxide partial pressure exceeds a certain limit, the reaction will occur. Since a tendency for the speed to decrease is also observed, taking these points into consideration, the preferable range of carbon monoxide partial pressure is 4 to about 50 Kg/cm ³ . As the molar ratio of hydrogen to carbon monoxide in the hydrogen/carbon monoxide mixed gas, the molar ratio proposed for general hydroformylation reactions is applied as is. When carrying out a hydroformylation reaction using a mixed gas with a molar ratio of hydrogen and carbon monoxide of about 0.5 to 5, the reaction pressure is α-acetoxy or propionyloxy-
Considering the selectivity to propionaldehyde, reaction rate, catalyst activity life, etc., it is desirable to keep it at about 25 Kg/cm ² or more. A more preferable upper limit for the reaction pressure is 150 Kg/cm ² .

The hydroformylation reaction according to the method of the invention is
Like the usual hydroformylation reaction of olefins, the reaction can be carried out in a continuous or batchwise manner in a stirred reactor or bubble column reactor known per se. During the reaction, the accumulation of reaction heat is suppressed, and α-acetoxy or propionyloxy-
vinyl acetate or vinyl propionate in the reaction system by continuously feeding vinyl acetate or vinyl propionate to improve the selectivity to propionaldehyde and prevent the accumulation of high-boiling byproducts. It is advantageous to carry out the reaction while maintaining the concentration of . The concentration of α-acetoxy or propionyloxy-propionaldehyde in the reaction mixture also depends on the accumulation of high-boiling byproducts, the amount of rhodium complex compounds and trisubstituted phosphine eluted into the aqueous medium layer, and the concentration of α-acetoxy or propionyloxy-propionaldehyde in the aqueous medium layer. From the viewpoint of extraction efficiency of -acetoxy or propionyloxy-propionaldehyde, it is advantageous to maintain the amount in the range of about 0.5 to about 3 mol per reaction mixture.

The reaction mixture containing α-acetoxy or propionyloxy-propionaldehyde, which is the target product obtained in the vinyl acetate or vinyl propionate hydroformylation reaction step (step), is subjected to an extraction operation with an aqueous medium in step), The α-acetoxy or propionyloxy-propionaldehyde is thereby extracted and separated into the aqueous medium layer. In the process of the invention, the aqueous medium used is water or an aqueous solution containing a small amount of an organic carboxylic acid derived from vinyl acetate or vinyl propionate. According to detailed studies by the present inventors, the extraction rate of α-acetoxy or propionyloxy-propionaldehyde into the aqueous medium layer, the elution amount of rhodium complex compounds and trisubstituted phosphine into the aqueous medium layer, Contact efficiency between the layer and the hydroformylation reaction mixture layer, extraction temperature, α- in the reaction mixture
The higher the contact efficiency between the aqueous medium layer and the hydroformylation reaction mixture layer, the higher the contact efficiency between the aqueous medium layer and the hydroformylation reaction mixture layer, depending on the acetoxy or propionyloxy-propionaldehyde concentration, the volume ratio of the aqueous medium to the reaction mixture, the atmosphere of the gas phase during extraction, etc. The lower the extraction temperature, the
The larger the volume ratio of the aqueous medium to the hydroformylation reaction mixture, the higher the extraction rate of α-acetoxy or propionyloxy-propionaldehyde into the aqueous medium layer, and the higher the extraction rate of α-acetoxy or propionyloxy-propionaldehyde into the aqueous medium layer. A tendency for the elution amount to decrease was observed. In terms of contact efficiency between the aqueous medium layer and the hydroformylation reaction mixture layer in the extraction step, the preferred type of extraction tower is a stirred tank type, and an RDC type extraction tower is particularly preferred.
The extraction temperature is selected from a range of about 5 to 40°C. The volume ratio of the aqueous medium to the hydroformylation reaction mixture depends on the concentration of α-acetoxy or propionyloxy-propionaldehyde in the reaction mixture, but when the concentration is about 0.5 to about 3 mol per reaction mixture, It is preferable to select from the range of 0.3 to 3. The extraction operation with an aqueous medium in step) is performed using substantially oxygen-free inert gases such as nitrogen gas, helium gas and argon gas, or hydrogen/carbon monoxide with a carbon monoxide partial pressure of at least 0.1 Kg/ ^cm2 . It is preferable to conduct the reaction under an atmosphere of a mixed gas or a hydrogen/carbon monoxide mixed gas having a carbon monoxide partial pressure of 0.1 Kg/cm ² or more diluted with the above-mentioned inert gas. Elution of complex compounds can be suppressed. Although the extraction operation can be carried out in a batch manner, it is industrially advantageous to carry out the extraction operation in a continuous manner.

The raffinate layer containing the catalyst component obtained in step) is recycled to the hydroformylation reaction step and reused in the next step). In this case, if necessary, a part of the raffinate layer can be separately taken out, subjected to a known catalyst activation treatment, and then recycled to the hydroformylation reaction step.

α-acetoxy or propionyloxy-propionaldehyde is obtained by fractional distillation from the aqueous medium layer containing α-acetoxy or propionyloxy-propionaldehyde obtained in step (step). It has been found that it is necessary to maintain the temperature of the distillate liquid below 90°C during fractional distillation in order to obtain α-acetoxy or propionyloxy-propionaldehyde in high yield and at a purity within a practical range. The temperature of the still liquid is 90
If the temperature exceeds 95°C, for example, hydrolysis reactions and polycondensation reactions occur simultaneously during distillation, resulting in α-
The purity and yield of acetoxy or propionyloxy-propionaldehyde decreases. The fractional distillation operation is usually carried out under reduced pressure depending on the aldehyde produced while maintaining the temperature of the distillate liquid at 90° C. or lower. For example, in the case of α-acetoxypropionaldehyde, a degree of vacuum of 10 to 90 mmHg is applied, and in the case of α-propionyloxypropionaldehyde, a degree of vacuum of 1 to 40 mmHg is applied.
In the method of the present invention, prior to such a fractional distillation operation, the aqueous medium layer is subjected to an extraction operation using an organic solvent or an adsorption treatment using an adsorbent such as activated carbon. Fractional distillation can also be carried out after partially removing trace amounts of rhodium complex compounds and organic phosphorus compounds contained in the mixture. α-acetoxy or propionyloxy-
Regarding the purity of propionaldehyde, it is possible to obtain highly purified α-acetoxy or propionyloxy-propionaldehyde that is substantially free of impurities if desired, but in order to increase the yield of these products, a very small amount of water and It is advantageous to isolate it as a product containing an organic carboxylic acid derived from vinyl acetate or vinyl propionate.

The method of the present invention will be explained in more detail below using Examples.

Example 1 HRh(CO) [P(C ₆ H ₅ ) ₃ ] ₃ 276 mg (0.3 mmol),
786 mg (3 mmol) of triphenylphosphine was mixed with hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio =
2/1) By dissolving in 130 ml of toluene at room temperature under an atmosphere, and then contacting this twice with 130 ml of distilled water purged with nitrogen gas for 30 minutes while stirring at a rotational speed of 500 rpm. Then, a cleaning treatment was performed. A stainless steel electromagnetic stirring autoclave with an internal volume of 300 ml, equipped with a thermometer, pressure regulator, off-gas flow control valve, and raw material feed port, is fully charged with hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 2/1). After replacing the toluene solution, _the interior of the autoclave was charged with the toluene solution that had been subjected to the cleaning treatment described above.
molar ratio = 2/1) and 30Kg/cm ² (carbon monoxide partial pressure 10
Kg/cm ² ), the autoclave was immersed in an oil bath and heated until the internal temperature was constant at 70°C.
Start stirring at a rotation speed of 600 rpm, and add 5.5 g of vinyl acetate from the vinyl acetate feed port.
(180 mmol) was introduced continuously over a period of 1 hour. During the reaction, a hydrogen/carbon monoxide mixed gas kept at the above molar ratio was passed from a small gas storage tank through a pressure regulator so that the off-gas flow rate was 8.5/hr, keeping it constant at 30 Kg/ ^cm2 . Introduced.
Low-boiling compounds (vinyl acetate, propionaldehyde, etc.) entrained in the off-gas were collected in a trap in a dry ice-acetone bath. After the addition of vinyl acetate was completed, the reaction was continued for an additional 2 hours under constant pressure (30 Kg/cm ² ) and constant temperature (70° C.) with stirring. The conversion rate of vinyl acetate 3 hours after the start of the reaction from the gas chromatography analysis of the reaction mixture is:
The selectivity of α-acetoxypropionaldehyde was 94% based on converted vinyl acetate.

After the reaction, the reaction mixture was cooled to room temperature, depressurized, and transferred to a 300 ml glass extraction device with a stirring device connected to an autoclave under a hydrogen/carbon monoxide mixed gas atmosphere maintained at the above molar ratio. did. Adding 40 ml of distilled water purged with nitrogen gas at 25° C. under the hydrogen/carbon monoxide mixed gas atmosphere (carbon monoxide partial pressure 0.33 Kg/cm ² ) to the extraction device,
By stirring for 15 minutes at a rotational speed of 500 rpm.
α-acetoxypropionaldehyde in the reaction mixture was extracted with water. The same operation was repeated by adding 35 ml of distilled water to the toluene solution layer after separation of the extracted water layer. The amount of distilled water (75 ml) used for the extraction operation was 1/1 in volume ratio to the reaction mixture.
It was 2. By the extraction operation, 96% of the produced α-acetoxypropionaldehyde was extracted into the aqueous layer. The rhodium concentration (measured by atomic absorption spectrometry) in the extracted aqueous layer was 0.05 ppm, and the phosphorus concentration (measured by colorimetric analysis) was 2 ppm.

Example 2 After the raffinate containing the catalyst component obtained as a result of the extraction operation in Example 1 was pumped from the extractor to the autoclave which had been purged with the hydrogen/carbon monoxide mixed gas used in Example 1, Vinyl acetate was continuously introduced and reacted in the same reaction procedure as in 1 over a period of about 55 minutes until the amount of vinyl acetate in the reaction system reached 15.5 g (180 mmol). The reaction mixture was subjected to extraction operation of the produced α-acetoxypropionaldehyde with water under the same operation and conditions as in Example 1. In this manner, the vinyl acetate hydroformylation reaction and extraction operation were repeated 10 times in total. As a result, the conversion rates of vinyl acetate in the 3rd, 6th, and 10th runs were 89%, 91%, and 90%, respectively, and no decrease in catalyst activity was observed due to repeated drying of the reaction and extraction operations. The rhodium concentrations (measured by atomic absorption spectrometry) in the third, sixth, and tenth extracted aqueous layers were 0.04, 0.03, and 0.06 ppm, respectively. The raffinate obtained after the reaction was repeated 10 times was transferred to a vacuum distillation apparatus under a nitrogen atmosphere, and the solvent, unreacted vinyl acetate, and residual α-acetoxypropionaldehyde were removed under reduced pressure at a temperature of 80°C. When distilled off, no accumulation of high-boiling by-products was observed in the residue. On the other hand, 250ml of the extracted aqueous layer was placed in a vacuum distillation apparatus that had been replaced with nitrogen in advance, and the temperature of the distillate was adjusted to
Fractional distillation was carried out under reduced pressure over a period of about 1 hour while maintaining the temperature at 65°C. Analysis by gas chromatography showed that the acquisition rate of α-acetoxypropionaldehyde (based on α-acetoxypropionaldehyde present in the extracted water layer) was 98%. Except for the presence of very small amounts of water and acetic acid, no other impurities were observed in the α-acetoxypropionaldehyde fraction.

Example 3 207 mg (0.23 mmol) of HRh(CO) [P(C ₆ H ₅ ) ₃ ] ₃ and 393 mg (1.5 mmol) of triphenylphosphine were added to a hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 2). /1) Dissolved in 125 ml of toluene at room temperature under an atmosphere, and then purged with nitrogen gas for 30 minutes while stirring at a rotation speed of 500 rpm.
The cleaning treatment was carried out by contacting the sample twice with distilled water. A stainless steel electromagnetic stirring autoclave with an internal volume of 300 ml, equipped with a thermometer, pressure regulator, off-gas flow control valve, and hydrogen/carbon monoxide mixed gas feed port, was equipped with a hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 2). After sufficient substitution with /1), the toluene solution subjected to the washing treatment and 22 g (256 mmol) of vinyl acetate were charged therein. The inside of the autoclave was filled with hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 2/1).
After pressurizing to 40Kg/cm ² (carbon monoxide partial pressure 13.3Kg/cm ² ), immerse the autoclave in a brewing bath until the internal temperature reaches 80℃.
It was heated until it became constant. Stirring was started at a rotation speed of 600 rpm, and the off-gas flow rate was 10/hr during the reaction.
By passing the hydrogen/carbon monoxide mixed gas from a small gas storage tank through a pressure regulator so that
Kg/ ^cm2 was kept constant and introduced. Through these operations, constant pressure (40Kg/cm ² ) and constant temperature (80℃) can be maintained.
The hydroformylation reaction of vinyl acetate is shown below.
It lasted 2.5 hours. The conversion rate of vinyl acetate 2.5 hours after analysis of the reaction mixture by gas chromatography was 92%, and the selectivity of α-acetoxypropionaldehyde based on the converted vinyl acetate was 93%.

After the reaction, the reaction mixture was cooled to room temperature, the pressure was released, and 70 ml of the reaction mixture was poured under an atmosphere of hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 1/1).
was transferred to an extraction device with an internal volume of 200 ml equipped with a stirring device. The extractor was replaced with nitrogen gas at 25°C under a hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 1/1) atmosphere (carbon monoxide partial pressure 0.5 Kg/cm ² ).
ml distilled water (1/2 volume ratio to reaction mixture)
was added and stirred for 30 minutes at a rotational speed of 500 rpm to extract α-acetoxypropionaldehyde in the reaction mixture with water. Through the extraction operation, 89% of the produced α-acetoxypropionaldehyde was extracted into the aqueous layer.
The rhodium concentration (measured by atomic absorption spectrometry) in the extracted aqueous layer was 0.06 ppm.

The remaining 70 ml of the reaction mixture was transferred under a nitrogen atmosphere to an extraction device with an internal volume of 200 ml equipped with a stirring device.
In a nitrogen gas atmosphere, α-acetoxypropionaldehyde was extracted under the same conditions as above using 35 ml of distilled water purged with nitrogen gas (volume ratio 1/2 to the reaction mixture). The extraction rate of α-acetoxypropionaldehyde was 88%, and the rhodium concentration (measured by atomic absorption spectrometry) in the extracted aqueous layer was 0.04 ppm.

Example 4 Vinyl propionate was prepared in the same manner as in Example 3, except that 25 g (250 mmol) of vinyl propionate was used instead of vinyl acetate, and 456 mg (1.5 mmol) of tritolylphosphine was used instead of triphenylphosphine. The hydroformylation reaction of nate was carried out. The conversion rate of vinyl propionate is 88
%, and α- based on converted vinyl propionate.
The selectivity of propionyloxypropionaldehyde was 91%. After the reaction mixture was cooled to room temperature, it was treated twice with 75 ml of nitrogen-substituted distilled water (total volume ratio of water used to reaction mixture: 1/1).
Extraction operation was performed by the method of Example 1. The extraction rate of α-propionyloxypropionaldehyde is 90%, and the rhodium concentration in the extracted water layer is
It was 0.03ppm. Next, 150ml of the extracted aqueous layer
was charged into a vacuum distillation apparatus that had been purged with nitrogen in advance, and fractional distillation was carried out under reduced pressure over about 30 minutes while maintaining the temperature of the bottom liquid at 75°C. Analysis by gas chromatography showed that the acquisition rate of α-propionyloxypropionaldehyde (based on α-propionyloxypropionaldehyde present in the extracted aqueous layer) was 96%. Except for the presence of very small amounts of water and propionic acid, no other impurities were observed in the α-propionyloxypropionaldehyde fraction.

Comparative Example 1 HRh(CO) [P(C ₆ H ₅ ) ₃ ] ₃ 276 mg (0.3 mmol).
786 mg (3 mmol) of triphenylphosphine was mixed with hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio =
2/1) A hydroformylation reaction of vinyl acetate was carried out in the same manner as in Example 1, except that a catalyst solution was prepared by dissolving the catalyst in 130 ml of dioctyl phthalate (DOP) at room temperature in an atmosphere. The conversion rate of vinyl acetate was 86%, and the selectivity of α-acetoxypropionaldehyde based on the converted vinyl acetate was 92%.

After the reaction, the reaction mixture was cooled to room temperature, depressurized, and charged into a vacuum distillation apparatus connected to an autoclave under an atmosphere of hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 2/1). The produced α-acetoxypropionaldehyde was distilled and separated under reduced pressure over a period of approximately 1 hour while maintaining the liquid temperature at 90°C. As a result of distillation separation, some of the α-acetoxypropionaldehyde present in the reaction mixture was removed.
85% were obtained. The residual liquid from the vacuum distillation turned brown, and metalization of the catalyst was observed. This vacuum distillation residue was again pumped into the autoclave under an atmosphere of hydrogen/carbon monoxide mixed gas (H ₂ /CO molar ratio = 2/1), and 15.5 g (180 mmol) of vinyl acetate was extracted.
The reaction was repeated under the same conditions as in Example 1, with continuous introduction of 1 hour over a period of 1 hour.

When the hydroformylation reaction of vinyl acetate and the distillation separation of the produced α-acetoxypropionaldehyde were repeated in this manner, it was observed that the catalytic activity decreased significantly as the number of repetitions increased.

Comparative Example 2 Of the extracted water obtained by the same method as Example 1
250 ml of the distillate was charged into a vacuum distillation apparatus which had been purged with nitrogen in advance, and the extracted aqueous layer was fractionated under reduced pressure for about 1 hour while maintaining the temperature of the distillate at 100°C.
The acquisition rate of α-acetoxypropionaldehyde (based on α-acetoxypropionaldehyde present in the extracted aqueous layer) was 85% based on the analysis results by gas chromatography. In addition, it was observed that a hydrolysis reaction of α-acetoxypropionaldehyde (acetic acid was a by-product) was partially occurring.

Comparative Example 3 In the same manner as in Example 1 except that 56 mg (0.075 mmol) of Rh ₄ (CO) ₁₂ was used instead of HRh (CO) [P (C ₆ H ₅ ) ₃ ] ₃ and triphenylphosphine. The reaction was carried out. The conversion rate of vinyl acetate is
The selectivity of α-acetoxypropionaldehyde was 94% based on converted vinyl acetate. The rhodium concentration in the extracted water layer was 2.98 ppm.

Claims (1)

[Claims] 1. Hydroformylation of vinyl acetate or vinyl propionate with a mixed gas of hydrogen and carbon monoxide in the presence of a substantially water-insoluble rhodium complex compound and a trisubstituted phosphine in an organic solvent. The reaction mixture obtained in step) is subjected to an extraction operation with an aqueous medium to extract and separate α-acetoxy or propionyloxy-propionaldehyde into an aqueous medium layer, and the raffinate containing the catalyst component obtained in step) is obtained. The layer is circulated to the hydroformylation reaction step of step), and fractionated from the aqueous medium layer containing α-acetoxy or propionyloxy-propionaldehyde obtained in step) while keeping the temperature of the still distillate below 90°C. A method for producing α-acetoxy or propionyloxy-propionaldehyde, which comprises obtaining α-acetoxy or propionyloxy-propionaldehyde.