JPH04338353A - Production of alpha-alkylacrolein - Google Patents

Abstract

PURPOSE:To produce an alpha-alkylacrolein from an aldehyde and formaldehyde in high yield with excellent stability by using a specific amount of a cyano compound as a catalyst. CONSTITUTION:An aldehyde (e.g. propionaldehyde) expressed by formula II (R1 is H, 1-10C alkyl or aryl) is reacted with formaldehyde at 0-250 deg.C by using a cyano compound (e.g. acetonitrile, propionitrile, butyronitrile, crotononitrile or benzonitrile) expressed by formula I (R2 is 1-10C alkyl, alkenyl or aromatic residue which may have substituent group) as a catalyst in an amount so as to provide 0.01-10.0 equiv. based on 1mol aldehyde expressed by formula II as a catalyst to afford an alpha-alkylacrolein (e.g. methacrolein). The objective compound is obtained in high yield under relatively mild conditions in a short time according to the aforementioned method excellent in stability. The cyano compound is rapidly reactive with water in an aqueous solution to form an amine salt which is an active species and thereby promote the reaction. Water present in the system is also utilized.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention is based on the general formula R1-CH2-
CHO (I) (wherein R
1 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group. The present invention relates to an improved method for producing α-alkyl acrolein by reacting an aldehyde represented by formula (1) with formaldehyde.

0002

[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, a method for producing α-alkyl acrolein by reacting an aldehyde represented by the above general formula (I) with formaldehyde has become important.

[0003] As a method for producing α-alkyl acrolein by reacting the aldehyde represented by the general formula (I) with formaldehyde, for example, Chemical Abstracts (C.A.), Vol. 56 (1962), 2321 ，
On page 2322, using a catalyst containing sodium and silicic acid from propionaldehyde and formaldehyde
A method is described to obtain methacrolein with a yield of 46% at 275°C. However, this method has a low yield and is problematic for industrially producing methacrolein.

As another method for producing α-alkyl acrolein by the reaction of the aldehyde represented by the above general formula (I) with formaldehyde, a method using a Mannich base has been proposed. It has been reported that salts of primary and secondary amines are used as catalysts in the production of α-alkyl acrolein using Mannich bases. For example, according to US Pat. No. 2,518,416, methacrolein is obtained from formaldehyde and propionaldehyde using monomethylamine hydrochloride as a catalyst, but the yield is not disclosed in this specification. When the present inventor conducted additional experiments, the yield was low, and when using this method, methylamine resulting from the decomposition of monomethylamine hydrochloride as a catalyst was mixed into the methacrolein produced, resulting in only very unstable methacrolein being obtained. It has been found. Further, according to US Pat. No. 2,518,416, etaacrolein is obtained from formaldehyde and butyraldehyde using monoethanolamine hydrochloride as a catalyst in a yield of 52% (based on the charged butyraldehyde).

[0005] These reports have fatal flaws in industrialization due to low yields and poor product stability. Furthermore, since amine hydrochloride is used, there are problems such as severe corrosion of the equipment.

In addition, in the case of JP-A-55-87737, since the reaction is carried out in an amine-excess system, in the distillation step for removing the target product α-alkyl acrolein from the reaction product liquid after the reaction is completed, α-alkyl acrolein is removed from the reaction product liquid. -Polymerization of alkyl acrolein occurs, and amines are mixed into the α-alkyl acrolein product, resulting in poor product stability.

As mentioned above, according to the prior art, the general formula (
There are many problems in industrially producing the corresponding α-alkyl acrolein from the aldehyde represented by I) and formaldehyde, and α-alkyl acrolein with high yield and excellent stability
- There is a strong desire to develop a technology for producing alkyl acrolein.

[0008]

[Means for Solving the Problems] The present inventor has completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention has the general formula R1-CH2-CHO (
I) (wherein R1 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group) (hereinafter abbreviated as aldehyde (I)) and formaldehyde, the corresponding α- In the method for producing alkyl acrolein, the general formula R2-CN is used as a catalyst.
(II) (wherein, R2 represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group, or an aromatic residue which may have a substituent) (hereinafter referred to as cyano compound (II) ) is the aldehyde (I) 1
0.01 to 10.0 equivalents, preferably 0.01 to 10.0 equivalents per mole.
Used in an amount of 1 to 2.0 equivalents, and heated at 0 to 250°C.
, preferably at a temperature of 20 to 150° C.

In the present invention, the cyano compound (II) used as a catalyst rapidly reacts with water in an aqueous solution,
The amine salt, which is an active species, is formed to promote the reaction. Therefore, the present invention does not require the step of preparing a catalyst salt by mixing an acid and an amine as in the conventional method, and is also economically advantageous because it utilizes water that is abundant in the reaction solution.
The selectivity of the reaction was also improved.

The alkyl group represented by R1 in the general formula (I) of the aldehyde (I) used as a starting material in 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,
These include 3-methylbutanal, n-pentanal, n-hexanal, 3-methylhexanal, 4-methylhexanal, n-heptanal, and phenylacetaldehyde. Among these, according to the present invention, propanal, n
-butanal and 3-methylbutanal are effective.

In the present invention, formaldehyde can be used in the form of an aqueous solution or a polymerized form such as trioxane or paraformaldehyde, 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.

[0012] In the present invention, the molar ratio of aldehyde (I) to formaldehyde is not restricted, but it is preferably 0.9 to 1.5 mol of formaldehyde per 1 mol of aldehyde (I). preferable. Formaldehyde is 0.9 per mole of aldehyde (I)
If the amount is less than mol, a condensation reaction of the aldehyde (I) itself occurs, which is not preferable. If the amount of formaldehyde is more than 1.5 mol per mol of aldehyde (I), a large amount of formaldehyde must be recovered, which not only causes loss in the recovery process, but also causes cyano compounds ( There are problems such as an increase in the amount of use of II).

The feature of the present invention is that a cyano compound (
II). Some examples of the cyano compound (II) used in the present invention include acetonitrile,
Propionitrile, acrylonitrile, 3-butenenitrile, cyclopropanecarbonitrile, crotonitrile, butyronitrile, isobutyronitrile, 2-pentenenitrile, 3-pentenenitrile, valeronitrile,
pivalonitrile, isovaleronitrile, 2-methylbutyronitrile, hexanenitrile, 4-methylvaleronitrile, 1-cyclopentenacetonitrile, 1-cyclohexylacetonitrile, 1-cyclohexenylacetonitrile, benzonitrile, o-tolnitrile, m-tolnitrile, p -Tolnitrile and the like. Particularly preferred cyano compounds are acetonitrile, propionitrile, butyronitrile, crotonitrile and benzonitrile.

In the present invention, the amount of cyano compound (II) used is 0.01 to 1 mole of aldehyde (I).
10.0 equivalents, preferably 0.1 to 2.0 equivalents. If the amount of cyano compound (II) used is out of this range, the reaction rate will slow down, and even if it is added more than necessary, the reaction rate will not increase, and on the contrary, side reaction products will increase, which is not preferable.

[0015] The reaction of the present invention is carried out at a pH of 2.5 to 12.0.
, preferably pH 4.5-7.5, reaction temperature 0-2
It is carried out continuously or discontinuously at 50°C, preferably from 20 to 150°C, under normal pressure, increased pressure or reduced pressure. The water content of the reaction mixture is preferably 20 to 20% in the starting mixture.
It is 60% by weight.

The reaction of the present invention can be carried out as follows. Aldehyde (I), formaldehyde, cyano compound (I)
The mixture of I) is held at the above reaction temperature for 5 to 120 minutes. The target substance is then separated from the reaction mixture in a conventional manner, for example by phase separation and/or distillation.

[0017]

EXAMPLES The present invention will be explained 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 A 35% formaldehyde aqueous solution was added to a mixture of 410 parts (10 moles) of acetonitrile and 800 parts of water at 20°C.
811 parts (10 moles) and propionaldehyde 58
0 parts (10 moles) are added and after the addition is complete the reaction mixture is held at 70° C. for 1.0 hour. From the reaction product liquid, 620 parts (88.5% of the theoretical value) of methacrolein was obtained from the top of the column by azeotropy of methacrolein and water.

Example 2 550 parts (10 mol) of propionitrile and 800 parts of water
811 parts (10 mol) of a 35% formaldehyde aqueous solution and 5 parts of propionaldehyde at 20°C.
80 parts (10 moles) are added and after the addition is complete the reaction mixture is held at 70°C for 1.0 hour. From the reaction product liquid, 622 parts (88.9% of the theoretical value) of methacrolein was obtained from the top of the column by azeotropy of methacrolein and water.

Example 3 A 35% formaldehyde aqueous solution was added to a mixture of 690 parts (10 mol) of butyronitrile and 800 parts of water at 20°C.
811 parts (10 moles) and propionaldehyde 58
0 parts (10 moles) are added and after the addition is complete the reaction mixture is held at 70° C. for 1.0 hour. From the reaction product liquid, 610 parts (87.1% of the theoretical value) of methacrolein was obtained from the top of the column by azeotropy of methacrolein and water.

Example 4 A 35% formaldehyde aqueous solution was added to a mixture of 1030 parts (10 moles) of benzonitrile and 800 parts of water at 20°C.
811 parts (10 moles) and propionaldehyde 58
0 parts (10 moles) are added and after the addition is complete the reaction mixture is held at 70° C. for 1.0 hour. From the reaction product liquid, 625 parts (89.3% of theory) of methacrolein was obtained from the top of the column by azeotropy of methacrolein and water.

[0022]

According to the present invention, it is surprisingly possible to obtain α-alkyl acrolein in a high yield in a short period of time and with excellent stability under relatively mild conditions. In addition, in the present invention, a cyano compound (
II) quickly reacts with water in an aqueous solution to form the amine salt as an active species and promote the reaction, so there is no need for a catalyst salt preparation step by mixing an acid and an amine as in conventional methods, and the system It is economically advantageous because it utilizes the abundant water inside, and the selectivity of the reaction has also improved.

Claims (1)

[Claims] Claim 1: General formula R1-CH2-CHO
(I) (wherein R1 is a hydrogen atom or has 1 to 10 carbon atoms)
represents an alkyl group or an aryl group. ) A method for producing the corresponding α-alkyl acrolein from an aldehyde and formaldehyde represented by the formula R2-CN as a catalyst.
(II) (wherein R2 has 1 to 1 carbon atoms
It shows an aromatic residue which may have 10 alkyl groups, alkenyl groups or substituents. ) of the cyano compound represented by
．． Used to give an equivalent of 0 to 10.0, and 0 to 250
A method for producing α-alkyl acrolein, characterized by carrying out the reaction at a temperature of °C.