Claims
- 1. A process for the continuous preparation of a diester of oxalic acid, which comprises
- (1) a first step of passing gas containing carbon monoxide and an ester of a saturated monohydric aliphatic or alicyclic alcohol having 1 to 8 carbon atoms with nitrous acid into a reactor packed with a solid catalyst comprising a platinum group metal or its salt, and catalytically reacting said carbon monoxide and ester of nitrous acid in the gaseous phase at a temperature of from 50.degree. to 200.degree. C. and a pressure of from ambient pressure to 10 kg/cm.sup.2 (gauge) to obtain a product containing (i) a diester of oxalic acid together with (ii) a by-product diester of carbonic acid and (iii) also containing nitrogen monoxide;
- (2) a second step of passing the product of the first step to a condenser to separate said product into a non-condensed gas containing nitrogen monoxide formed by the catalytic reaction of the first step from a condensed liquid containing (i) the diester of oxalic acid together with (ii) said by-product diester of carbonic acid;
- (3) a third step of passing the non-condensed gas of the second step to a regeneration column and therein contacting it with a gas containing molecular oxygen and an alcohol to react with nitrogen monoxide in said non-condensed gas to regenerate said ester of nitrous acid as the regeneration gas and to provide a concentration of nitrogen monoxide in said regeneration gas withdrawn from the regeneration column of from 2 to 7% by volume, and recycling said regeneration gas containing said ester of nitrous acid to the reactor of the first step;
- (4) a fourth step of passing the condensed liquid of the second step to a distillation column and distilling out an alcohol containing said diester of carbonic acid formed as a by-product by the catalytic reaction of the first step, and obtaining a liquid diester of oxalic acid; and
- (5) a fifth step of passing the distillate of the fourth step to a hydrolysis column and hydrolyzing the diester of carbonic acid in the gas into its acid and alcohol components and recycling the alcohol thereby obtained to the third step as an alcohol source for the third step.
- 2. The process as claimed in claim 1, wherein said solid catalyst comprises palladium or a palladium salt.
- 3. The process as claimed in claim 1 or 2, wherein said catalytic reaction is carried out at a temperature of from 80.degree. to 150.degree. C.
- 4. The process as claimed in claim 1, wherein the product of the first step is contacted with an alcohol in said condenser and is cooled in said condenser at a temperature of at most the boiling point of said alcohol.
- 5. The process as claimed in claim 4, wherein said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 6. The process as claimed in claim 1, wherein the amount of said gas containing molecular oxygen in the third step is in the range of from 0.08 to 0.2 mole in terms of oxygen relative to one mole of nitrogen monoxide passed into in said regeneration column.
- 7. The process as claimed in claim 1, wherein the amount of the alcohol used in the third step is from 2 to 5 parts by volume relative to one part by volume of nitrogen monoxide passed into said regeneration column.
- 8. The process as claimed in claim 1, wherein the hydrolysis of the fifth step is carried out by a gas phase reaction in the presence of an alumina catalyst at a temperature of from 150.degree. to 250.degree. C.
- 9. The process as claimed in any one of claims 4, 6, 7 or 8, wherein said solid catalyst comprises palladium or a palladium salt, said catalytic reaction is carried out at a temperature of from 50.degree. to 200.degree. C. and under a pressure of between ambient pressure and 10 kg/cm.sup.2 (gauge).
- 10. The process as claimed in any one of claims 2, 4 or 8, wherein the amount of the alcohol used in the third step is from 2 to 5 parts by volume relative to one part by volume of nitrogen monoxide passed into said regeneration column, and the amount of the alcohol used in the third step is from 2 to 5 parts by volume relative to one part by volume of nitrogen monoxide passed into said regeneration column.
- 11. The process as claimed in any one of claims 2, 6, 7 or 8, wherein said catalytic reaction is carried out at a temperature of from 80.degree. to 150.degree. C. and under a pressure of ambient pressure to 10 kg/cm.sup.2 (gauge); the product of the first step is contacted with an alcohol in said condenser and is cooled in said condenser at a temperature of at most the boiling point of said alcohol; and said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 12. The process as claimed in claim 10, wherein said catalytic reaction is carried out at a temperature of from 80.degree. to 150.degree. C. and under a pressure of ambient pressure to 10 kg/cm.sup.2 (gauge); the product of the first step is contacted with an alcohol in said condenser and is cooled in said condenser at a temperature of at most the boiling point of said alcohol; and said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 13. The process as claimed in any one of claims 1, 2, 4, 5, 6, 7 or 8, wherein said ester of nitrous acid is the methyl ester of nitrous acid, said diester of oxalic acid is the dimethyl oxalate, said diester of carbonic acid is the dimethyl ester of carbonic acid, and said alcohol is methyl alcohol.
- 14. The process as claimed in claim 11, wherein said ester of nitrous acid is the methyl ester of nitrous acid, said diester of oxalic acid is the dimethyl oxalate, said diester of carbonic acid is the dimethyl ester of carbonic acid, and said alcohol is methyl alcohol.
- 15. The process as claimed in claim 12, wherein said ester of nitrous acid is the methyl ester of nitrous acid, said diester of oxalic acid is the dimethyl oxalate, said diester of carbonic acid is the dimethyl ester of carbonic acid, and said alcohol is methyl alcohol.
- 16. The process as claimed in any one of claims 1, 2, 4, 5, 6, 7 or 8, wherein said ester of nitrous acid is the ethyl ester of nitrous acid, said diester of oxalic acid is the diethyl oxalate, said diester of carbonic acid is the diethyl ester of carbonic acid, and said alcohol is ethyl alcohol.
- 17. The process as claimed in claim 11, wherein said ester of nitrous acid is the ethyl ester of nitrous acid, said diester of oxalic acid is the diethyl oxalate, said diester of carbonic acid is the diethyl ester of carbonic acid, and said alcohol is ethyl alcohol.
- 18. The process as claimed in claim 12, wherein said ester of nitrous acid is the ethyl ester of nitrous acid, said diester of oxalic acid is the diethyl oxalate, said diester of carbonic acid is the diethyl ester of carbonic acid, and said alcohol is ethyl alcohol.
Priority Claims (1)
Number |
Date |
Country |
Kind |
118343 |
Aug 1980 |
JPX |
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Parent Case Info
This is a continuation of application Ser. No. 293,702, filed Aug. 17, 1981, now abandoned.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4229589 |
Nishimura et al. |
Oct 1980 |
|
4229591 |
Nishimura et al. |
Oct 1980 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
2025950 |
Jan 1980 |
GBX |
Continuations (1)
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Number |
Date |
Country |
Parent |
293702 |
Aug 1981 |
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