Process for preparing a diester of oxalic acid in the gaseous phase

Abstract

A process for preparing a diester of oxalic acid which comprises bringing carbon monoxide into contact with an ester of nitrous acid or with an alcohol and a nitrogen oxide or a hydrate of the nitrogen oxide in the gaseous phase in the presence of a solid catalyst containing metallic palladium or a salt thereof, a gas containing molecular oxygen being introduced into the reaction system in cases where said nitrogen oxide or a hydrate of the nitrogen oxide requires molecular oxygen together with the alcohol to form an ester of nitrous acid.

We claim: 
     
       1. A process for preparing a diester of oxalic acid which comprises contacting an ester of nitrous acid with carbon monoxide in the gaseous phase under ambient or reduced pressure in the presence of a solid catalyst containing metallic palladium or a salt thereof at a temperature of 50° to 200° C., .[.and.]. .Iadd.said .Iaddend.ester of nitrous acid being an ester of nitrous acid with an alcohol having 1 to 8 carbon atoms selected from the group consisting of a saturated monohydric .[.alphatic.]. .Iadd.aliphatic .Iaddend.alcohol and an alicyclic alcohol, to produce the diester of oxalic acid containing the same ester group as that of said ester of nitrous acid. 
     
     
       2. The process of claim 1, wherein a gas containing molecular oxygen is added to the gaseous reaction mixture. 
     
     
       3. The process of claim 1, wherein an alcohol having 1 to 8 carbon atoms selected from the group consisting of a saturated monohydric alcohol and an alicyclic alcohol is added to the gaseous reaction mixture. .Iadd. 4. A process for preparing a diester of oxalic acid which comprises bringing, in a zone in which a liquid phase is not accumulated, carbon monoxide together with a vaporized ester of nitrous acid in a gaseous phase into contact with a solid catalyst containing metallic palladium or a salt thereof at a temperature of 50° to 200° C. and under a pressure in the range where a liquid phase is not accumulated in said zone, said ester of nitrous acid being an ester of nitrous acid with an alcohol having 1 to 8 carbon atoms selected from the group consisting of a saturated monohydric aliphatic alcohol and an alicyclic alcohol, to produce in said zone the diester of oxalic acid containing the same ester group as that of said ester of nitrous acid. .Iaddend..Iadd. 5. The process of claim 4 wherein said zone is under a pressure from ordinary pressure to about 10 kg/cm 2  G. .Iaddend..Iadd. 6. The process of claim 4 wherein said zone is under a pressure from ordinary pressure to about 5 kg/cm 2  G. .Iaddend..Iadd. 7. The process of claims 4, 5 or 6, wherein a gas containing molecular oxygen is added to said gaseous phase. .Iaddend..Iadd. 8. The process of claims 4, 5 or 6, wherein an alcohol having 1 to 8 carbon atoms selected from the group consisting of a saturated monohydric alcohol and an alicyclic alcohol is added to said gaseous phase. .Iaddend..Iadd. 9. The process of claim 4 wherein the ester of nitrous acid is fed to said zone. .Iaddend.