Process for preparing oxalic acid and esters of same

A process for the preparation of oxalic acid and alkyl esters of oxalic acid by the oxidation, in the liquid phase, of carbon monoxide and a liquid selected from the group consisting of water and monofunctional alkyl alcohols with a gas selected from the group consisting of oxygen and oxygen-containing gases, in the presence of a catalyst system of the redox type consisting essentially of palladium salts of Pd (II) or of metallic Pd (zero valent) and of soluble salts of a metal more electropositive than palladium selected from the group consisting of Cu, Co, Fe and Ni, having at least two oxidation states, being further characterized in that the reaction is conducted at a temperature ranging from 20.degree. to about 100.degree. C. and a pressure ranging from 10 to about 150 atm. abs. in the presence of an effective amount of a co-catalyst consisting essentially of ammonia, the concentration of the palladium salt being between 0.0001 mole per liter and 1 mole per liter, the concentration of the salt of the metal more electropositive than palladium being between 0.01 and 1 mole per liter and the molar ratios of the salt of the metal more electropositive than palladium to ammonia ranging from 1:1 to 1:5.