JPH051008A - Production of 1,4-dicyanobutene compounds - Google Patents

Abstract

PURPOSE:To produce the subject 1,4-dicyanobutene compound useful as a precursor for adiponitrile in a high selectivity, while extremely preventing the production of polymeric by-products, by dimerizing acrylonitrile. CONSTITUTION:When acrylonitrile is dimerized in the presence of a phosphinite catalyst or phosphonite catalyst, preferably a compound of formula I or II (Ar is aromatic nucleus; X, X' are H, alkyl, alkoxy, alkylamino; R, R' are alkyl, cycloalkyl, aryl), especially the phosphinite catalyst to produce a 1,4- dicyanobutene compound useful as a precursor of an intermediate for synthetic fibers or plastics, an aromatic amide compound of formula III (R1 is 6-12C aryl; R2 is H, 1-6C alkyl, cycloalkyl, aryl) is added to the reactional system to reduce the production of polymeric by-products, thereby giving the objective compound in a higher selectivity than by conventional methods.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 1,4-dicyanobutenes. More specifically, it relates to an improvement in the method for producing 1,4-dicyanobutenes by dimerization of acrylonitrile.

[0002]

BACKGROUND OF THE INVENTION 1,4-Dicyanobutenes (cis-1,
4-dicyanobutene-1, trans-1,4-dicyanobutene-1 and trans-1,4-dicyanobutene-2
Etc.) are important substances as precursors of adiponitrile, which is an intermediate for synthetic fibers and plastics. Conventionally,
As a method for selectively obtaining 1,4-dicyanobutenes by dimerization of acrylonitrile, for example, JP-B-59-59
JP-A-36906 and JP-B-61-17819 disclose a method for dimerizing acrylonitrile in the presence of a phosphinite catalyst or a phosphonite catalyst in an alcohol solvent.

In the above method, a desired dimer and a considerable amount of acrylonitrile hexamer and other oligomers and polymers (hereinafter collectively referred to as polymer by-products) are produced, and the polymer by-products are produced. Of the dimer causes a decrease in the selectivity of the dimer. In particular, a solid polymer by-product may undesirably block pipes and causes various difficulties in the process.

On the other hand, JP-A-53-65822 discloses that in the above method, an anhydrous metal compound such as anhydrous zinc salt or cobalt salt is added to suppress solid polymer by-products. However, the generation of polymer byproducts other than solids could not be sufficiently suppressed, and the selectivity of the dimer was insufficient. Further, JP-A-61-158953 describes the use of formamide as an extraction solvent for the dimerization product in the above method, but in this case as well, formation of a polymer by-product is avoided. Instead, a considerable amount of solid is formed. Further, in Japanese Patent Publication No. 61-17817, an organic phosphite catalyst is used, but in this case as well, a polymer by-product is produced and there is a problem in stability of the organic phosphite catalyst.

It has been proposed to add a hydrocarbon solvent in order to suppress the formation of a polymer by-product in the above-mentioned method, but not only the dimerization reaction rate decreases but also
The suppression effect is not sufficient.

[0006]

DISCLOSURE OF THE INVENTION The present invention suppresses the formation of polymer by-products in the method for producing 1,4-dicyanobutenes by dimerizing acrylonitrile as much as possible, and provides 1,4-dicyanobutene with high selectivity. The purpose is to obtain the kind.

[0007]

Means for Solving the Problems As a result of repeated studies to achieve the above object, the present inventors have identified a dimerization reaction when acrylonitrile is dimerized using a phosphinite catalyst or a phosphonite catalyst. When it is carried out in the presence of an aromatic amide compound having a structure, it is confirmed that the production of polymer by-products is suppressed, and the desired 1,4-dicyanobutenes can be produced with a high selectivity, and thus the present invention was reached did. That is, the gist of the present invention is to dimerize acrylonitrile in the presence of a phosphinite catalyst or a phosphonite catalyst and an aromatic amide compound represented by the formula (1) in claim 1, 1, 4 -In the process for the production of dicyanobutenes.

The present invention will be described in detail below. The catalyst used for the dimerization of acrylonitrile in the present invention includes various phosphinite catalysts or phosphonite catalysts. Particularly, the compound represented by the following formula (2) or (3) is preferable.

[0009]

[Chemical 2]

[0010]

[Chemical 3]

[In the formulas (2) and (3), Ar represents an aromatic nucleus, and X and X'represent a hydrogen atom, an alkyl group,
It represents an alkoxy group or an alkylamino group, which may be the same or different from each other. R and R'represent an alkyl group, a cycloalkyl group or an aryl group, which may be the same or different. ]

Specific examples of Ar in formulas (2) and (3) include a phenyl group and a naphthyl group.
X and X ′ are hydrogen atom; methyl group, ethyl group,
Alkyl group such as isopropyl group; alkoxy group such as methoxy group, ethoxy group, propoxy group, t-butoxy group;
Examples thereof include an alkylamino group such as a dimethylamino group and a diethylamino group, and X and X ′ may be the same as or different from each other.

R and R'in the equations (2) and (3)
Specific examples of the alkyl group having 1 to 8 carbon atoms such as methyl group, ethyl group, isopropyl group, neopentyl group; cycloalkyl group such as cyclohexyl group; phenyl group, p-methoxyphenyl group, biphenyl group, naphthyl group. Examples thereof include a substituted or unsubstituted aryl group having 6 to 15 carbon atoms such as a group, and R and R ′ may be the same or different from each other.

An example of a typical phosphinite catalyst is methyldiphenylphosphinite (Ph ₂ POM).
e), ethyldiphenylphosphinite, isopropyldiphenylphosphinite, cyclohexyldiphenylphosphinite, methylbis-p-tolylphosphinite, ethylbis-p-tolylphosphinite and the like.

As an example of a typical phosphonite catalyst, diethylphenylphosphonite [PhP (OEt)]
₂ ], dimethylphenylphosphonite, diethyl-p-
Examples include tolylphosphonite, dimethyl-p-tolylphosphonite, diisopropylphenylphosphonite, diisopropyl-p-tolylphosphonite and the like.

The amount of these phosphinite catalysts or phosphonite catalysts used is not particularly limited, but is usually 0.1 to 60% by weight based on the total amount of the components such as the raw material, catalyst and solvent in the dimerization reaction, Preferably 1 to 30
It is selected from the range of weight%. Although the phosphinite catalyst and the phosphonite catalyst described above are both effective in the reaction of the present invention, the phosphinite catalyst is more preferable from the viewpoint of stability of the catalyst.

In the present invention, when acrylonitrile is dimerized using the above-mentioned catalyst to produce 1,4-dicyanobutenes, the dimerization reaction is carried out by the following formula (1).

[Chemical 4] (In the formula, R ₁ represents an aryl group having 6 to 12 carbon atoms, and R ₂
Represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group or an aryl group), and is an essential requirement to carry out in the presence of an aromatic amide compound represented by Thereby, the target 1,4-dicyanobutenes can be obtained with a higher selectivity than in the conventional method.

Since the aromatic amide compound acts as a hydrogen donor during the dimerization of acrylonitrile, it has at least one donable hydrogen atom. Specific examples of R ₁ in the formula (1) include a phenyl group and p
- tolyl group, a biphenyl group, a naphthyl group and the like, also R ₂
As, a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group and a t-butyl group,
Examples thereof include cyclohexyl group and phenyl group. Specific examples of these aromatic amide compounds are, for example, benzamide, 1-naphthalenecarboxamide, 1,1′-biphenyl-4-carboxamide, benzanilide and the like.

The amount of the aromatic amide compound represented by the formula (1) to be used is usually 0.1 to 20 times equivalent, preferably 0.5 to 10 times, the molar number of the phosphinite catalyst or phosphonite catalyst used. It is selected from the equivalent range. In the present invention, in addition to the above components, benzene, toluene, as a co-solvent for suppressing the formation of polymer by-products,
It is preferable to add a hydrocarbon solvent such as ethylbenzene, xylene, hexane, heptane or decane. The amount of these auxiliary solvents is not particularly limited, but if a large amount is added, the reaction rate will decrease.

The dimerization reaction of acrylonitrile according to the method of the present invention is usually carried out by mixing a predetermined amount of acrylonitrile, a phosphinite catalyst or a phosphonite catalyst, an aromatic amide compound and preferably a hydrocarbon solvent under an inert gas atmosphere. , Usually -10 to 100 ° C, preferably 5
It is carried out by stirring at a temperature of about -80 ° C.
Since the presence of water hinders the progress of the reaction, it is desirable to sufficiently dry the above components in advance.

[0021]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples below, the products were analyzed by gas chromatography and gel permeation chromatography. Further, the "conversion rate" indicates a weight% of acrylonitrile converted into a dimer and a polymer by-product with respect to a charged acrylonitrile. The "selectivity" of a product is
It is the value in% of the weight ratio of the product to the weight of the converted acrylonitrile. Further, 1,4-dicyanobutenes include cis-1,4-dicyanobutene-1, trans-1,4-dicyanobutene-1 and trans-1,
Represents 4-dicyanobutene-2.

Example 1 2.01 g (37.9 mmol) of acrylonitrile, 4.1 g of benzene, 0.85 g (7.02 mmol) of benzamide were placed in a 30 ml-volume flask under an argon atmosphere.
And isopropyldiphenylphosphinite 0.96g
(3.9 mmol) was charged and heated to 60 ° C on an oil bath to 1
The mixture was stirred for a time to carry out a dimerization reaction. After completion of the reaction, the product was quantitatively analyzed by gas chromatography using an internal standard method (internal standard substance: biphenyl). The conversion rate of acrylonitrile reached 63.2%. The selectivity of 1,4-dicyanobutenes was 92.7%, the selectivity of 2-methyleneglutaronitrile was 5.9%, and the selectivity of all dimers was 98.6%. Only trace amounts of solid polymer by-product were detected.

Example 2 The amount of benzamide used in Example 1 was 3.50 mm.
When the reaction was carried out in the same manner as in Example 1 except that ol was used, the conversion rate of acrylonitrile was 54.0%, and 1,4
-Selectivity of dicyanobutenes is 88.5%,
The selectivity of methyleneglutaronitrile is 6.0%,
The selectivity of all dimers was 94.5%. No solid polymer by-products were detected.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that 0.42 g (7 mmol) of isopropanol was used instead of the benzamide used in Example 1, and the conversion rate of acrylonitrile was found to be 46.2%, the selectivity of 1,4-dicyanobutenes is 87.2%, the selectivity of 2-methyleneglutaronitrile is 5.6%, and the selectivity of all dimers is 92.8. %Met. In addition, solid polymer by-products were detected with a selectivity of 5.6%.

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that 0.32 g (7 mmol) of formamide was used instead of the benzamide used in Example 1, and the conversion rate of acrylonitrile was 66. 1%, the selectivity of 1,4-dicyanobutenes is 79.9%, the selectivity of 2-methyleneglutaronitrile is 5.0%, and the selectivity of all dimers is 84.9%. there were. In addition, solid polymer by-products were detected at a selectivity of 9.2%.

Comparative Example 3 A reaction was conducted in the same manner as in Example 1 except that 0.41 g (7 mmol) of acetamide was used instead of the benzamide used in Example 1, and the conversion rate of acrylonitrile was 43. 4%, the selectivity of 1,4-dicyanobutenes is 78.9%, the selectivity of 2-methyleneglutaronitrile is 5.8%, and the selectivity of all dimers is 84.7%. there were. In addition, solid polymer by-products were detected at a selectivity of 12.5%.

[0027]

According to the present invention, the aromatic amide compound represented by the above formula (1) is used together with a phosphinite catalyst or a phosphonite catalyst when dimerizing acrylonitrile to produce 1,4-dicyanobutenes. By doing so, the production of polymer by-products can be suppressed and the target product can be obtained with high selectivity.

Claims (1)

What is claimed is: 1. A phosphinite catalyst or a phosphonite catalyst, and a compound represented by the following formula (1): (In the formula, R ₁ represents an aryl group having 6 to 12 carbon atoms, and R ₂
Represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group or an aryl group) and dimerizes acrylonitrile in the presence of an aromatic amide compound represented by 1, Process for producing 4-dicyanobutenes.