JPH04173757A - Production of alpha-alkylacrolein - Google Patents

Abstract

PURPOSE:To obtain the title substance by reacting an alkylaldehyde with formaldehyde in the presence of a catalyst comprising specific amounts of an organic carboxylic acid and a secondary amine firstly in a reactor of complete blender, then in a piston flow reactor and introducing the resulting substance to a decomposition column. CONSTITUTION:A compound shown by the formula (R1 is H or 1-10C alkyl) is allowed to react with formaldehyde in a molar ratio of 1:(1-1.5) in the presence of a catalyst comprising an organic carboxylic acid and a secondary amine through three processes to give a corresponding alpha-alkylacrolein. In the catalyst, the amount of the organic acid used (e.g. acetic acid) is 1-5 equivalents to 1mol compound shown by the formula and 0.5-2 equivalents to 1 equivalent of the secondary amine (e.g. dimethylamine). The objective substance is produced through the three processes of the first process in a reactor of complete blender at 30-120 deg.C, the second process in a piston flow type reactor at 30-120 deg.C and the third process in a decomposition column at 80-150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a compound represented by the formula % (I) (wherein R1 represents H or an alkyl group having 1 to 10 carbon atoms). The present invention relates to an improved method for producing α-alkyl acrolein by reacting an aldehyde with formaldehyde.

[Prior art and problems to be solved by the invention] α-alkyl acrolein is an industrially useful intermediate raw material,
Many manufacturing methods have been proposed. From among these,
In recent years, due to the ease of obtaining raw materials, α by the reaction of the aldehyde represented by the above general formula (I) and formaldehyde
-The method for producing alkyl acrolein has become important.

Examples of the method for producing α-alkyl acrolein by the reaction of the aldehyde represented by the general formula (I) with formaldehyde include Chemical Abstracts (C, A,),
Volume 56 (I962), pages 2321 and 2322, describes a method for obtaining methacrolein from propionaldehyde and formaldehyde using a catalyst containing sodium oxide and silicic acid at 275°C with a yield of 46%. . However, this method has a low yield and is problematic for industrially producing methacrolein. .

According to West German Patent No. 875194, piperidine is added to a boiling mixture of an aqueous formaldehyde solution, propionaldehyde, sodium chloride and butyric acid over a period of 2 to 3 hours, and the reaction is allowed to proceed for a further 3 hours. , metaacrolein was obtained in a high yield of 95%. This method has the disadvantage that the reaction time is very long, and is not satisfactory as a method for industrially obtaining methacrolein.

According to JP-A-58-188831, it is reported that methacrolein can be obtained in high yield in the presence of an aqueous formaldehyde solution, propionaldehyde, a secondary amine, and an acid.

However, in this case, a high pressure and a high temperature of 150° C. or higher are required, and in the case of industrialization, the equipment cost would be enormous, and also from an operational standpoint it is not satisfactory as a method for obtaining methacrolein industrially.

According to US Pat. No. 2,848,499, a Mannich base is synthesized in the presence of an aqueous solution of formaldehyde, propionaldehyde, a secondary amine and an acid.1. It has been reported that methacrolein can be obtained in high yield by supplying this base to the decomposition layer and decomposing the base. In this method, a piston flow type reactor is used to increase the reaction rate at the stage of synthesizing Mannich base. A piston flow type reactor has a higher reaction rate than a complete mixing tank type reactor, but in the case of an intense and exothermic reaction like this one, it is difficult to efficiently dissipate the intense reaction heat near the reactor inlet. It is very difficult to remove it, and it is not satisfactory as a method for industrially obtaining methacrolein due to the increase in side reaction products and safety.

As mentioned above, there are many problems in industrially producing the corresponding α-alkyl acrolein from the aldehyde represented by the general formula (I) and formaldehyde using conventional techniques, and it is difficult to produce α-alkyl acrolein in high yield. , there is a strong desire to develop a technology for producing it under as mild reaction conditions as possible.

[Means to solve the problem]

The present inventor has completed the present invention as a result of intensive studies to solve the above problems.

That is, the present invention provides an aldehyde (hereinafter abbreviated as aldehyde (I)) represented by the formula (I) (wherein R1 represents H or an alkyl group having 1 to 10 carbon atoms). ) and formaldehyde to produce the corresponding α-alkylacrolein from aldehyde (I
) 1 to 1.5 moles of formaldehyde are used per mole of aldehyde (I), an organic carboxylic acid and a secondary amine are used as catalysts, and the amount of organic carboxylic acid used is 1 to 5 equivalents per mole of aldehyde (I), and 0.5 to 1 equivalent of secondary amine
2 equivalents, and the reaction was carried out in three steps. In the first step, the reaction temperature was set at 30 to 120°C in a complete mixing tank reactor.
The reaction was carried out to a rate of change of aldehyde (I) of 50 to 90%, and the crude reaction liquid was supplied to the second step. In the second step, the reaction was carried out in a piston flow type reactor at a reaction temperature of 30 to 120 °C. After the reaction is terminated, the crude reaction liquid of the second step is supplied to the decomposition tower of the third step, heated at 80 to 150°C, and α-
The present invention provides a method for producing α-alkyl acrolein, which is characterized by obtaining alkyl acrolein.

The alkyl group R in the base (I) of the aldehyde (I) used as a starting material for the present invention has 1 to 10 carbon atoms. This group may be linear or branched, or may be partially substituted with an aromatic group. Some examples of aldehydes (I) used in the present invention include acetaldehyde, propionaldehyde (propanal), n-butanal, 3-methylbutanal,
These include n-pencunal, n-hexanal, 3-methylhexanal, 4-methylhexanal, n-heptanal, and phenylacetaldehyde. Among these, propanal, n-butanal, and 3-methylbutanal are particularly effective according to the present invention.

In the present invention, formaldehyde can be used in an aqueous solution or in a polymerized form such as trioxane or varapormaldehyde, but it is generally preferable to carry out the reaction in the form of an aqueous solution.

The reaction is usually carried out in the form of an aqueous solution, but it can also be carried out in a solvent such as a hydrocarbon or alcohol.

In the present invention, the molar ratio of aldehyde (I) to formaldehyde is preferably 1 to 1.5 mol of formaldehyde per 1 mol of aldehyde (I). If the amount of formaldehyde is less than 1 mole per mole of aldehyde (I), a condensation reaction of the aldehyde (I) itself will occur, and this reaction product will enter the α-alkyl acrolein product, which is undesirable. In addition, if formaldehyde is more than 1.5 mol per 1 mol of aldehyde (J), a large amount of formaldehyde must be recovered, which not only causes loss in the recovery process, but also causes secondary damage due to inactivation of the catalyst by formaldehyde. There are problems such as an increase in the amount of grade amine used.

The catalyst system of the present invention consists of a mixture of an organic carboxylic acid and a secondary amine. Any organic carboxylic acid can be used, and is carried out in the form of mono-, di- or polycarboxylic acids. Preferred organic carboxylic acids include carboxylic acids having 1 to 10 carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, oxalic acid,
Succinic acid, glutaric acid, adipic acid, malic acid, tartaric acid,
Examples include citric acid, pyromellitic acid, phthalic acid, and fumaric acid.

The secondary amine used in the present invention is represented by the following formula, and low-molecular and high-molecular secondary amines can be used.

(In the formula, R2 and R3 represent organic groups which may be the same or different, and R2 and R3 may form a ring together with N.) Examples of suitable secondary amines used in the present invention In Toshi,
Dimethylamine, diethylamine, methylethylamine, methylpropylamine, dipropylamine, dibutylamine, diisopropylamine, diisobutylamine,
Methylisopropylamine, methylisobutylamine,
Methyl 5ec-butylamine, methyl-(2-methylpentyl)-amine, medyl-(2-ethylhexyl)-
Amine, pyrrolidine, piperidine, morpholine, N-methylpiperazine, N-hydroxyethyl-piperazine,
Examples include piperazine, hexamethyleneimine, jetanolamine, methylethanolamine, methylcyclohexylamine, methylcyclopentylamine, dicyclohexylamine, and these amines alone or a mixture of these amines can be used.

The amount of catalyst used is 1 to 5 per mole of aldehyde (I).
It is carried out using 0.5 to 2 equivalents of organic carboxylic acid per equivalent of secondary amine in the presence of an equivalent amount of organic carboxylic acid. If the amount of the organic carboxylic acid used relative to the aldehyde (I) is out of the above range, the reaction rate will not only slow down, but also the amount of side reaction products will increase, which is undesirable. Furthermore, when the amount of organic carboxylic acid is less than 0.5 equivalent per equivalent of secondary amine, the reaction rate increases, but polymerization of the reaction product is promoted. Furthermore, if the amount of organic carboxylic acid exceeds 2 equivalents per equivalent of secondary amine, the reaction rate decreases, which is undesirable.

A major feature of carrying out this reaction is that the reaction is carried out in three steps. The first step uses a completely mixed tank reactor to continuously supply the raw materials aldehyde (I) and formaldehyde and the catalyst organic carboxylic acid and secondary amine, and the reaction temperature is 30 to 120°C. ) to a rate of change of 50 to 90%. If the reaction temperature is less than 30°C, the reaction rate becomes slow, which is not preferable. 120 again
If the temperature exceeds .degree. C., the reaction rate will be faster, but the reaction pressure will be higher and the equipment cost will be enormous, which is not preferable.

The rate of change of raw material aldehyde (I) in the first step is 50
If it is less than %, heat generation at the inlet of the piston flow type reactor in the second step becomes large, which is not preferable. If the rate of change exceeds 90%, the heat generation at the inlet of the reactor in the second step will be reduced, but the reaction time in the first step will be longer, which is economically disadvantageous. The fully mixed tank reactor used in this first step is a seed reactor, in which the reaction liquid in the reactor is sufficiently mixed and the concentration and temperature are considered to be uniform at each point within the reactor. It is about. The reaction operation method may be continuous, batch, or semi-batch, but it is preferable to carry out the reaction continuously. In a continuous seed reactor, the introduced reaction raw materials are immediately mixed, the reaction proceeds, and the reaction products are discharged from the reactor with the same concentration and temperature within the reactor.

The reaction crude liquid produced in the first step is supplied to a piston flow type second reactor to complete the reaction. The piston flow type reactor used here is a back type reactor.
The liquid in the reactor flows as if being pushed out by a piston,
This is a reactor in which concentration distribution occurs because fluids are not mixed in the flow direction. The reaction temperature and reaction time in this second step depend on the raw material change rate in the first step, but the reaction temperature
The temperature is from 0 to 120°C for a few minutes to about 1 hour. The reaction crude liquid of the second step is supplied to the decomposition column of the third step,
The mixture is heated at 100° C. to obtain α-alkyl acrolein from the top of the column. If the decomposition temperature is less than 8°C, the decomposition time will be long, which is economically disadvantageous. Moreover, if the temperature exceeds 150°C, the pressure will be high and the equipment cost will be enormous, which is not preferable. Further, the catalyst liquid recovered from the bottom of the column can be recycled and used in the first step, and industrially it is preferable to recycle the catalyst liquid.

〔Example〕

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited by these Examples unless the gist thereof is exceeded.

Note that parts in the examples are based on weight.

Example 1 81 parts (1 mole) of a 37% formaldehyde aqueous solution and 58 parts of propionaldehyde were added to a stirred complete mixing tank reactor per hour.
1 mol), 148 parts (2 mol) of propionic acid, 258 parts (2 mol) of n-dibutylamine, and 327 parts of water were reacted at a reaction temperature of 90° C. and a residence time of 30 minutes to continuously form a reaction crude. I took out the liquid. The conversion rate of propionaldehyde was 85%. The reaction crude liquid was supplied to a piston flow type reactor heated with hot water at 90°C, and the reaction was completed in a residence time of 20 minutes. The rise in reaction temperature at the reactor inlet was less than 1°C. 872 parts of the reaction crude liquid per hour is taken out from the second reactor and continuously supplied to the decomposition column, and the decomposition is carried out at a residence time of 20 to 25 minutes and a decomposition temperature of 105°C.
69.3 g of methacrolein and 0.14 g of methacrolein dimer and 2-methylbentenal were added from the top of the column.
139 g of the liquid containing the filtrate was obtained. 148 parts of propionic acid, 258 parts of n-dibutylamine, and 327 parts of water were obtained from the bottom of the column and recycled to the first reactor.

Comparative Example 1 81 parts of a 37% formaldehyde aqueous solution, 58 parts of propionaldehyde, 148 parts of propionic acid, 258 parts of n-dibutylamine, and 327 parts of water were supplied per hour to a piston flow type reactor heated with hot water at 90°C. The reaction was carried out for a residence time of 35 minutes, and the reaction crude liquid was continuously taken out. The reaction temperature at the inlet of the reactor rose by 21°C, and a vigorous reaction was observed. 872 parts of the reaction crude liquid per hour is taken out from the reactor and continuously fed to the decomposition column for a residence time of 20 to 2 hours.
The decomposition was carried out for 5 minutes at a temperature of 105°C, and 68.3 g of methacrolein, methacrolein dimer and 2-
A liquid containing 0.97 g of methylpentenal was obtained.

〔Effect of the invention〕

According to the present invention, it is surprisingly possible to obtain α-alkyl acrolein in a high yield in a short time under relatively mild reaction conditions, and it is also possible to obtain α-alkyl acrolein in a high yield in a short period of time, and also to obtain a product of high purity with less impurities such as aldehyde dimers. Since a high amount of α-alkyl acrolein can be obtained, for example, when producing methacrylic acid using the produced methacrolein, there is an advantage that no special purification process is required.

Claims (1)

[Claims] 1. Corresponding aldehydes and formaldehydes represented by the general formula R_1-CH_2-CHO...(I) (wherein R_1 represents H or an alkyl group having 1 to 10 carbon atoms) In a method for producing α-alkyl acrolein,
1 to 1.5 mol of formaldehyde is used per 1 mol of aldehyde represented by general formula (I), an organic carboxylic acid and a secondary amine are used as catalysts, and the amount of organic carboxylic acid used is according to general formula (I). 1 to 5 equivalents per mole of aldehyde expressed, and 0.5 to 5 equivalents per equivalent of secondary amine
2 equivalents, and the reaction was carried out in three steps. In the first step, the reaction temperature was set at 30 to 120°C in a complete mixing tank reactor.
The rate of change of aldehyde represented by general formula (I) is 50~
After reacting to 90%, the crude reaction liquid is supplied to the second step, and in the second step, the reaction temperature is carried out in a piston flow type reactor at 30 to 120°C to terminate the reaction, and the crude reaction liquid of the second step is A method for producing α-alkyl acrolein, which comprises supplying α-alkyl acrolein to a cracking tower in the third step, heating it at 80 to 150°C, and obtaining α-alkyl acrolein from the top of the tower. 2. The method for producing α-alkyl acrolein according to claim 1, wherein the organic carboxylic acid and secondary amine of the catalyst are recovered from the bottom of the column in the third step and recycled for use in the first step.