JPS6244534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carboxylic acids by isomerizing formic acid esters in the presence of a catalyst and carbon monoxide.

Methods for producing carboxylic acids by isomerizing formic acid esters include a method using a rhodium catalyst and a halogen compound cocatalyst in the presence of carbon monoxide (Japanese Patent Publication No. 49-3513), and a method using a rhenium catalyst in the presence of carbon monoxide. Also known are methods using halogen compounds (Japanese Unexamined Patent Publication No. 1986-65703). However, since these metals are expensive, it is difficult to use them industrially unless the catalytic activity is extremely high and the decrease in activity is minimal.

As a result of various studies on methods for isomerizing formic acid esters using relatively inexpensive palladium-based catalysts, the present inventors discovered that a catalyst consisting of metal palladium or a palladium compound and an alkyl halide or a hydrogen halide was further combined with an amine, an amide, or a phosphine. The present inventors have discovered that when formic acid ester is isomerized in the presence of carbon monoxide in the presence of a base such as It is something.

The present invention will be explained in detail below.

Specifically, the formic acid ester used as a raw material in the present invention has the following general formula HCOOR (wherein R is a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group,
Straight-chain or branched alkyl groups such as t-butyl groups, alkenyl groups such as allyl groups, benzyl groups,
Represents an aralkyl group such as a phenethyl group. ), and the carboxylic acid which is the isomerization product is represented by the following general formula RCOOH (wherein R is the same as defined above).

Metal palladium or palladium compounds that are one of the catalyst components include metal palladium such as palladium black and supported metal palladium, Ovalent palladium complexes such as tetrakis(triphenylphosphine) palladium, palladium oxide, palladium chloride, and palladium nitrate. , inorganic compounds such as tetraamminedichloropalladium, palladium acetate, α-
Organic acid salts such as palladium picolinate, chelate compounds such as bis(acetylacetonato)palladium, palladium complex salts such as palladium bis(triphenylphosphine)diacetate, [Pd ₄ (CO) ₄
Examples include palladium cluster compounds such as (OCOCH ₃ ) ₄ ]・2CH ₃ COOH. When supporting these on a carrier, activated carbon, silica, alumina,
Supports such as silica alumina, zeolite, diatomaceous earth, titania, and magnesia are used. The amount of metal palladium or palladium compound to be used is appropriately selected within the range of 0.1 to 100 milligram atoms, preferably 1 to 50 milligram atoms, in terms of palladium alone, per mol of formic acid ester as a raw material. .

Specific examples of alkyl halides include methyl bromide, methyl iodide, and ethyl iodide, and specific examples of hydrogen halides include hydrogen bromide, hydrogen iodide, and the like. These halides are
0.1 to 1000 mol, preferably 1 to 100 mol is used.

The base, which is another component constituting the catalyst, includes organic bases such as amines, amides, and phosphine. Specifically, heteroaromatic tertiary amines such as pyridine, picoline, lutidine, pyrimidine, pyrazine, quinoline, 1,10-phenanthroline, 2,2'-bipyridyl, triethylamine, tributylamine, benzyldimethylamine, Aliphatic or alicyclic tertiary amines such as N,N,N',N'-tetraethylethylenediamine, tricyclohexylamine, N- such as N-ethylpyrrolidine, N-methylpiperidine, N,N'-dimethylpiperazine, etc. substituted heterocyclic tertiary amine,
N-substituted lactams such as N-methylpyrrolidone and N-ethylpiperidone, N,N-disubstituted fatty acid amides such as N,N-dimethylacetamide, tertiary phosphotriamides such as hexamethylphosphotriamide, tributylphosphine, Trialkylphosphine such as dimethyloctylphosphine, tricycloalkylphosphine such as tricyclohexylphosphine, triarylphosphine such as triphenylphosphine, dimethylphenylphosphine, 1,2-bis(diphenylphosphine) ) Tertiary alkylaryl phosphines such as ethane and the like. The amount of these bases used is 0.1 to 10,000 mol, preferably 1 to 1,000 mol, per gram atom of palladium.

In carrying out the method of the present invention, the use of a reaction solvent is not essential, but if desired, ethers such as diethyl ether, dioxane, tetrahydrofuran, ethylene glycol dimethyl ether,
Ketones such as acetone and ethyl methyl ketone, alcohols such as methanol, ethanol and butanol, fatty acids and their esters such as acetic acid, propionic acid, butyric acid and ethyl acetate, nitriles such as acetonitrile and benzonitrile, benzene,
Aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, aliphatic saturated hydrocarbons such as pentane, hexane, and octane, and the like can be used.

The isomerization reaction of formic acid ester according to the present invention can be carried out in any of a liquid phase homogeneous system, a liquid phase suspension system, and a gas phase fixed bed system. The reaction is 100~
Under a temperature condition of 350℃, preferably 150-250℃, 1
It is carried out under a carbon monoxide partial pressure of ~250Kg/cm ³ , preferably 10-200Kg/cm ³ , more preferably 30-150Kg/cm ³ , and as carbon monoxide, hydrogen may be used in addition to pure carbon monoxide. Carbon monoxide diluted with a gas inert to the reaction, such as nitrogen, can be used.
However, when using hydrogen as the diluent gas,
If the amount used is too large, side reactions due to reduction will occur, so the amount of hydrogen used is 20 mol% or less, preferably 5 mol% or less.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 In a 300 ml titanium autoclave, 28.2 g (470 mmol) of methyl formate and 0.18 g of palladium chloride were added.
g (1 mmol), methyl iodide 5.68 g (40 mmol) and α-picoline 0.93 g (10 mmol)
charged, carbon monoxide partial pressure 100Kg/cm ³ , reaction temperature
The reaction was carried out at 200°C for 3 hours. After the reaction was completed, the autoclave was left to cool and the pressure was released, and the reaction product liquid was analyzed by gas chromatography. As a result, the conversion rate of methyl formate was 99.0%, and the yields of acetic acid and methyl acetate were 60% and 10%, respectively.

Comparative Example 1 An experiment was conducted in the same manner as in Example 1 except that α-picoline was not used. As a result, the conversion rate of methyl formate was 53.5%, and the yields of acetic acid and methyl acetate were 2.7% and 5.0%, respectively.

Example 2 2% Pd/activated carbon 5 instead of palladium chloride
The experiment was conducted in the same manner as in Example 1, except that 1 mmol of Pd was used. the result,
The conversion rate of methyl formate was 99.1%, and the yields of acetic acid and methyl acetate were 62% and 6.5%, respectively.

Example 3 An experiment was carried out in the same manner as in Example 1 except that 10 mmol of triphenylphosphine was used instead of α-picoline. As a result, the conversion rate of methyl formate was 99.1%, and the yields of acetic acid and methyl acetate were 57% and 4%, respectively.

Example 4 An experiment was conducted in the same manner as in Example 1 except that the carbon monoxide partial pressure was changed to 50 Kg/cm ³ . the result,
The conversion rate of methyl formate was 87.1%, and the yields of acetic acid and methyl acetate were both 14%.

Example 5 An experiment was conducted in the same manner as in Example 1, except that 344 mmol of ethyl formate was used instead of methyl formate. As a result, the conversion rate of ethyl formate was 54.5%
The selectivity of propionic acid was 30%.

Example 6 Same as Example 1 except that hydrogen-carbon monoxide mixed gas (H ₂ /CO = 1/4) was used instead of carbon monoxide and the carbon monoxide partial pressure was 80 Kg/cm ³ conducted an experiment. As a result, the conversion rate of methyl formate is
64%, and the yields of acetic acid and methyl acetate were respectively
They were 10% and 18%. Further, formalin was not detected, and it was confirmed that hydrogenolysis of methyl formate did not occur.

Claims (1)

[Claims] 1 Metallic palladium or palladium compound,
A method for producing a carboxylic acid, which comprises isomerizing a formate in the presence of a catalyst consisting of an alkyl halide or a hydrogen halide and a base, and carbon monoxide.