Patent ID: 8269036

Claim:
A process for producing an oxalate by coupling of CO, comprising a) feeding a nitrite and CO as feedstock to a first reaction zone to contact them with a first palladium-containing catalyst, to form a first reaction effluent containing unreacted nitrite, CO and oxalate product; b) passing the first reaction effluent into a gas-liquid separator to conduct gas-liquid separation, to obtain a liquid product stream and a gas mixture stream; c) feeding the liquid product stream obtained from b) to a separation unit, to obtain a first portion of the oxalate product; d) feeding the gas mixture stream obtained from b) to a second reaction zone to contact it with a second palladium-containing catalyst, to form a second reaction effluent containing the oxalate; and e) feeding the second reaction effluent to the separation unit, to obtain a second portion of the oxalate product, wherein the molar ratio of the CO to the nitrite in the feedstock fed to the first reaction zone is from 1:1 to 5:1.