Claims
- 1. A process for continuously preparing 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 (guage) to obtain a product containing a diester of oxalic acid;
- (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 the diester of oxalic 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 the non-condensed gas to regenerate said ester of nitrous acid as a gas and to provide a concentration of nitrogen monoxide in said gas at the outlet of the regeneration column of from 2 to 7% by volume; and
- (4) a fourth step of recycling the outlet gas of the third step containing the ester of nitrous acid and from 2 to 7% by volume of nitrogen monoxide to the reactor of the first step.
- 2. 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 0.08 to 0.2 mole in terms of oxygen relative to one mole of nitrogen monoxide passed into said regeneration column.
- 3. The process as claimed in claim 1, wherein the amount of the alcohol used in the third step is in the range of 2 to 5 parts by volume relative to one part by volume of nitrogen monoxide passed into said regeneration column.
- 4. The process as claimed in claim 1, wherein said solid catalyst comprises palladium or a palladium salt.
- 5. The process as claimed in claim 4, wherein said catalytic reaction is carried out at a temperature of from 80.degree. to 150.degree. C.
- 6. 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.
- 7. The process as claimed in claim 6, wherein said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 8. The process as claimed in claim 1, wherein (i) the amount of said gas containing molecular oxygen in the third step is in the range of 0.08 to 0.2 mole in terms of oxygen relative to one mole of nitrogen monoxide passed into said regeneration column; (ii) the amount of the alcohol used in the third step is in the range of 2 to 5 parts by volume relative to one part by volume of nitrogen monoxide passed into said regeneration column; and (iii) said ester of nitrous acid is an ester of a saturated monohydric aliphatic or alicyclic alcohol having 1 to 8 carbon atoms with nitrous acid.
- 9. The process as claimed in claim 8, wherein (i) said solid catalyst comprises palladium or a palladium salt; (ii) said catalytic reaction is carried out at a temperature of from 50.degree. to 200.degree. C.; and (iii) said catalytic reaction is carried out under a pressure of ambient pressure to 10 kg/cm.sup.2 (gauge).
- 10. The process of claim 8, wherein (i) said solid catalyst comprises palladium or a palladium salt; (ii) said catalytic reaction is carried out at a temperature of from 80.degree. to 150.degree. C.; and (iii) said catalytic reaction is carried out under a pressure of ambient pressure to 10 kg/cm.sup.2 (gauge).
- 11. The process as claimed in claim 8, wherein said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 12. The process as claimed in claim 9, wherein said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 13. The process as claimed in claim 10, wherein said alcohol is a lower alcohol having 1 to 4 carbon atoms.
- 14. The process as claimed in any of claims 8, 10, 11 or 13, 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.
- 15. The process as claimed in any one of claims 1, 8, 10, 11 or 13, wherein said ester of nitrous acid is the methyl ester of nitrous acid; said diester of oxalic acid is the dimethyl oxalate; and said alcohol is methyl alcohol.
- 16. The process as claimed in any one of claims 1, 8, 10, 11 or 13, wherein said ester of nitrous acid is the ethyl ester of nitrous acid; said diester of oxalic acid is the diethyl oxalate; and said alcohol is ethyl alcohol.
- 17. The process as claimed in claim 14 wherein said gas at the outlet of said regeneration column contains substantially no nitrogen dioxide and no oxygen.
- 18. The process as claimed in claim 1 wherein said gas at the outlet of said regeneration column contains substantially no nitrogen dioxide and no oxygen.
Priority Claims (2)
Number |
Date |
Country |
Kind |
55-116456 |
Aug 1980 |
JPX |
|
55-116458 |
Aug 1980 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 293,703, filed Aug. 17, 1981, 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 |
293703 |
Aug 1981 |
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