JPS5839815B2 - Production method of oxalic acid diester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing oxalic acid diesters.

Oxalic acid diesters have a variety of industrial uses, such as analytical reagents, solvents, and raw materials for oxamide and odantic acid.

Conventionally, a method for producing an oxalic acid diester by reacting an acetal or a boric acid ester with carbon monoxide and oxygen is known.

For example, US Pat. No. 4,005,131 discloses a method for producing an oxalic acid diester using an acetal as a raw material, and US Pat. No. 4,041,068 discloses a method for producing an oxalic acid diester using a boric acid ester as a raw material.

However, in all of these methods, metal salts, amine bases, alcohols, etc. are used in combination as catalysts, and the catalyst systems are extremely complicated.

Therefore, these methods not only require complicated operations such as recovery, regeneration, and recycling of the catalyst, but also produce a large amount of carbon dioxide gas as a by-product, which reduces the yield of the oxalic acid diester, which is the target product. It has disadvantages such as poor selectivity and has not been put to practical use.

The present inventors have conducted various intensive studies in order to establish a method that improves the various drawbacks of these known methods using acetal or boric acid ester as raw materials.

As a result, they found that oxalic acid diesters can be produced extremely effectively by using palladium metal or its salts as catalysts and nitrite esters or nitric acid as reaction promoters, and have completed the present invention.

That is, the present invention provides oxalic acid by reacting an acetal or borate with carbon monoxide and oxygen in the presence of (4) palladium metal or its salt, and (8) nitrite or nitric acid. A method for producing diesters is provided.

Compared to conventional methods using acetal or boric acid ester as raw materials, the present invention not only simplifies the catalyst system and makes it extremely easy to recover, regenerate, or recycle it, but also suppresses the production of by-products. , the desired oxalic acid diester can be produced with high yield and high selectivity.

Acetal, which is a raw material in the present invention, has the general formula RCH
(OR')2, R is preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and R1 is preferably an alkyl group having 1 to 20 carbon atoms. It may have a hydrocarbon or aromatic hydrocarbon as a side chain.

Specific examples include dimethoxymethane, jetoxymethane, dipropoxymethane, dibutoxymethane, dipentyloxymethane, dihexyloxymethane, dioctyloxymethane, didodecyloxymethane, dihexadecyloxymethane, 1,1-dimethoxyethane. ,1,1
-jethoxyethane, 1,1-dimethoxypropane, l
, ■-dimethoxybutane, 1,1-dibutoxybutane,
1.1-jethoxybutane, 1,1-dibutoxyethane, 1,1-hexyloxyhexane, 1,1-dinonylokidinonane, 1,1-undecyloxyundesane,
Examples include 1,1-dipentadecyloxypentadesane.

The other raw material, boric acid ester, is represented by the general formula B(OR2)3, where R2 has 1 to 20 carbon atoms.
is preferably an alkyl group, which may have an alicyclic hydrocarbon or aromatic hydrocarbon as a side chain in its carbon chain.

Specific examples include trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triamyl borate, trihexyl borate, triheptyl borate, trioctyl borate, trinonyl borate, tridodecyl borate, and triborate. Examples include pentadecyl, triotadecyl borate, and tribenzyl borate.

The reaction of the present invention proceeds according to the following formula, and oxalic acid diester is produced.

Useful catalysts in the present invention include palladium metal, or nitrates, hydrochlorides, sulfates, phosphates, and acetates of palladium metal.

The amount used is preferably 0.11) 1 m to 2% by weight based on the acetal or boric acid ester used as the raw material.

In addition, when carrying out the present invention industrially, in order to facilitate the recovery of the catalyst or products and to prevent loss of the catalyst, these catalysts may be treated with activated carbon, silica gel, alumina, silica alumina, diatomaceous earth, It may be used by being supported on a carrier such as magnesia, pumice, or monocular sieve.

Nitrite ester or nitric acid is used as a reaction accelerator, and nitrite esters include methyl nitrite, ethyl nitrite, propyl nitrite, butyl nitrite, amyl nitrite, hexyl nitrite, heptyl nitrite, and nitrite. Nonyl, decyl nitrite, tridecyl nitrite, hexadecyl nitrite, benzyl nitrite, and the like are useful.

The concentration of these nitrites or nitric acid used can vary over a wide range, but in order to obtain a satisfactory reaction rate, the concentration of these nitrites or nitric acid used should be at least 0.5% by weight based on the reaction medium.
It is necessary to have the nitrite ester present at a concentration above.

The upper limit of the concentration used can be arbitrarily selected so as to obtain the desired reaction rate.

The carbon monoxide used in the process of the invention can be pure or diluted with an inert gas, such as nitrogen, or it can contain small amounts of hydrogen or methane gas.

The partial pressure of carbon monoxide in the reaction system is usually 5 to 200
It is desirable to be within the atmospheric pressure range.

Further, oxygen may be diluted with an inert gas such as nitrogen, or may be air.

The partial pressure is determined in consideration of the explosion limit, and is normally adjusted so that the oxygen concentration in the introduced gas is 8% by volume or less.

In order to introduce this oxygen into the system, it is usually advantageous to introduce carbon monoxide and oxygen into the reaction system through the same inlet or through separate inlets, either simultaneously or separately.

However, oxygen does not necessarily need to be introduced into the reaction system together with carbon monoxide; if desired, carbon monoxide and nitrite can be reacted first, and then oxygen can be introduced in a subsequent step.

This reaction may be carried out without a solvent or in a solvent inert to this reaction.

Particularly when the desired product, oxalic acid diester, has a high melting point and is crystalline, it is advantageous to carry out the reaction in a uniform liquid phase using a solvent.

Suitable solvents include, for example, lower fatty acid esters such as ethyl acetate, propyl acetate, butyl acetate, amyl acetate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, dimethyl oxalate, oxalate, etc. aliphatic dicarboxylic acid diesters such as diethyl acid, dipropyl oxalate, dibutyl oxalate, dimethyl succinate, diethyl succinate, dimethyl adipate, carbonic acid diesters such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, benzoic acid Aromatic carboxylic acid esters such as methyl, ethyl benzoate, and dimethyl phthalate, ethers such as dioxane and dibutyl ether, hydrocarbons such as benzene, toluene, xylene, cyclohexane, and n-hexane, and other monochlorobenzenes. , dichlorobenzene, nitrobenzene, acetophenone, alkyl sulfone, alkyl sulfoxide, etc. can be used.

In the method of the present invention, it is usually preferable to carry out the reaction within the range of 20 to 150°C, and it can be carried out either batchwise or continuously, but the continuous method is industrially advantageous because the heat of reaction can be easily removed. It's a method.

Next, examples of the present invention and comparative examples will be given.

Example 1 In an autoclave with an internal volume of 300 doors, 1,1-di-n-
Butoxy n-butane 50wL11 benzene 5 as solvent
0rrL11 Palladium metal supported on activated carbon 0.1
? (10wt%Pd) and n-butyl nitrite 2.5
1 was charged, and after sealing, 60 kg/=a of carbon oxide was press-fitted.

Next, after raising the temperature to 90°C, oxygen was added at a rate of 4JlcrA at a rate of 2
The mixture was pressurized twice and the reaction was carried out at 90°C for 1 hour.

After the reaction was completed, the product was analyzed by gas chromatography.

As a result, di-n-butyl oxalate was 22.1 mmol
0.6 mmol of di-n-butyl carbonate and 24.5 mmol of carbon dioxide were produced as by-products.

Example 2 70 wt% nitric acid 1.8 instead of n-butyl nitrite
The experiment was conducted in the same manner as in Example 1, except that Example 2 was used.

As a result, di-n-butyl oxalate was 15.2 mmol.
Although 41.8 mmol of carbon dioxide gas was produced as a by-product, no di-n-butyl carbonate was observed as a by-product.

Example 3 60.2f of 1,1 jetoxyethane was placed in an autoclave with an internal volume of 300rrLl. , palladium metal supported on activated carbon 0.1 ? (2wt%Pd) and nitrite n-
After charging 2.51 butyl and sealing, add 60 k of carbon oxide.
g/cd G press fit.

Then, after raising the temperature to 110'C, oxygen was added at 4 kg/cri
'i' was injected twice, and the reaction was carried out at 110'C for 0.5 hour.

After the reaction was completed, the product was analyzed by gas chromatography.

As a result, 18.5 mmol of diethyl oxalate was produced, and no by-products were produced at all.

Example 4 An experiment was conducted in the same manner as in Example 3, except that the amount of n-butyl nitrite used was IOS' and the reaction temperature was 90°C.

As a result, 25.5 mmol of diethyl oxalate was produced, and no by-products were produced at all.

Example 5 Boric acid) I instead of 1.1-di-n-butoxy n-butane
An experiment was conducted in the same manner as in Example 1, except that 25 rrtl of Jn-butyl and 75 rrLl of benzene were used.

As a result, di-n-butyl oxalate was 29.0 m mo
1 was produced, and di-n-butyl carbonate was 0.1 mmol.
And 12.9 mmol of carbon dioxide gas was produced as a by-product.

Example 6 1.1-Di-n-butoxy 2511 Ll of tri-n-butyl borate was used instead of n-butane, and the amount of benzene used was 75 rrLl, and 7 was used instead of n-butyl nitrite.
An experiment was conducted in the same manner as in Example 1, except that 1.82% of 0 wt% nitric acid was used.

As a result, 21.2 mmol of di-n-butyl oxalate was produced, 0.1 mmol of di-n-butyl carbonate, and 20.5 mmol of carbon dioxide gas were produced as by-products.

Example 7 Same as Example 1 except that 50ml of 1゜l-jethoxyn-butane was used instead of 1.1-di-n-butoxyn-butane, and 0.11ml of palladium acetate was used instead of palladium metal. The experiment was conducted using the following operations.

As a result, diethyl oxalate was 24.1 mmol
0.3 mmol of diethyl carbonate was produced as a by-product.

Example 8 In an autoclave with an internal volume of 300 m1, boric acid trin-
Butyl 50ml 1. As a solvent, 40 parts of benzene, 0.1 f (2 wt% Pd) of palladium metal supported on activated carbon, and 10 parts of n-butyl nitrite were charged, and after sealing, the carbon oxide content was reduced to 60 parts! 9/Cf? LG was press-fitted.

Next, the temperature was raised and maintained at 90°C, and 4 kg/cr of oxygen was injected over a period of 20 minutes. After 20 minutes, -carbon oxide was injected until the pressure reached the pressure before the oxygen was injected, and again 4 kg/cr? of oxygen was injected. i to 2
It took 0 minutes to press fit.

This injection operation of oxygen and carbon monoxide was performed one more time.

After the reaction was completed, the product was analyzed by gas chromatography, and it was found that 90.5m of di-n-butyl oxalate was present.
mol was produced, and 0.5 mmol of di-n-butyl carbonate was produced as a by-product.

Example 9 An experiment was conducted in the same manner as in Example 8, except that 0.11% of palladium nitrate was used instead of palladium metal.

As a result, 72.6 mmol of di-n-butyl oxalate was produced, and 1.2 mmol of di-n-butyl carbonate was produced as a by-product.

Example 10 Palladium acetate 0.051 was used instead of palladium metal, and 70 wt% nitric acid 1.0 was used instead of n-butyl nitrite.
The experiment was conducted in the same manner as in Example 1, except that No. 81 was used.

As a result, 12.4 mmol of di-n-butyl oxalate, 0.3 mmol of di-n-butyl carbonate, and 45.6 mmol of carbon dioxide gas were produced as by-products.

Example 11 In an autoclave with an internal volume of 300 rI'Ll, 25 ml of tri-n-butyl borate and 75 ml of benzene as a solvent were added.
1゜Palladium chloride 0.05r and 70wt% nitric acid ■
, 82 and after sealing - 60kg/c4G of carbon oxide
It was press-fitted.

Next, after raising the temperature to 90°C, oxygen was added at 4 kg/cr? L
After 20 minutes of pressurizing the mixture twice, -carbon oxide was pressurized until the pressure reached the pressure before oxygen was pressurized, and the reaction was carried out at 90° C. for 1 hour.

As a result, 18.5 mmol of di-n-butyl oxalate was produced, and 1.5 mmol of di-n-butyl carbonate was produced as a by-product.

Comparative Example 1 In an autoclave with an internal volume of 3001 rll, 50a1 of benzene as a solvent and 50a1 of 1-di-n-butoxyn-butane.
0TrL11n-butanol 3g, palladium chloride 0.
15S'1 lithium chloride 0.051i? , copper chloride 3゜0
8P,) Prepare 2.34S' of ethylamine hydrochloride,
The subsequent operations were performed in the same manner as in Example 1.
, 005, 131 was carried out.

As a result, di-n-butyl oxalate was 0.5 mmol
Although only a small amount of by-product di-n-butyl carbonate was produced, a large amount of carbon dioxide gas was produced as a by-product, 51.0 mmol.

Comparative Example 2 The method described in USP 4,041,068 was prepared in the same manner as in Comparative Example 1, except that 25 ml of tri-n-butyl borate was used instead of 1.1-di-n-butoxy-n-butane. A follow-up test was conducted on the invention.

As a result, di-n-butyl oxalate was 6.5 mmol
Although di-n-butyl carbonate was not observed as a by-product, a large amount of carbon dioxide gas, 68.2 mmol, was produced as a by-product.

Claims (1)

[Claims] 1. A method characterized by reacting an acetal or a boric acid ester with carbon monoxide and oxygen in the presence of (4), palladium metal or a salt thereof, and (2) a nitrite or nitric acid. , a method for producing oxalic acid diester. 2 general formula, RCH(OR')2 (wherein R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and R' represents an alkyl group having 1 to 20 carbon atoms). The manufacturing method according to claim 1, which uses the following. 3. The manufacturing method according to claim 1, which uses a boric acid ester represented by the general formula B (OR2) 3 (wherein R2 represents an alkyl group having 1 to 20 carbon atoms).