Abstract: In an exothermic liquid-phase reaction involving a liquid reactant and a gaseous reactant, the gas from the reactor vapor phase is subjected to gas-liquid separation and the non-condensible gas thus separated is recycled to the reactor liquid phase. As the non-condensible gas is recycled to the reactor liquid phase, the liquid components in the liquid phase are vaporized and the resulting latent heat of vaporization removes heat. Therefore, the reaction temperature can be easily controlled by regulating the flow rate of the non-condensible gas so recycled. This method of controlling the reaction temperature can be applied with particular advantage to a commercial process for producing a carbonic ester from an alcohol, carbon monoxide and oxygen.