Method for producing nitrous acid ester, and method for producing dialkyl oxalate and dialkyl carbonate

A method for producing nitrous acid ester in which an alcohol is supplied to an upper part of a reaction column for producing nitrous acid ester, is made to flow downward from the upper part to a lower part of the reaction column, nitric oxide and oxygen, or a gas mixture thereof is supplied to the lower part of the reaction column, and nitric oxide, oxygen, and the alcohol are reacted, thereby generating nitrous acid ester, the method comprising:

• a step of extracting a bottom liquid containing water, nitric acid, and an alcohol from the bottom part of the reaction column so as to supply the bottom liquid to a reactor, and supplying nitric oxide and/or carbon monoxide to the reactor;
• a step of generating nitrous acid ester by brining nitric oxide and/or carbon monoxide into contact with the bottom liquid in the reactor;
• a step of supplying nitrous acid ester obtained in the reactor to the reaction column;
• a step of supplying a reaction liquid containing water, nitric acid, and the alcohol to a nitric acid condensing column from a lower part of the reactor;
• and
• a step of separating a low-boiling point component by distillation from the reaction liquid in the nitric acid condensing column under control of a concentration of an alcohol in a condensed liquid being generated at a bottom part of the nitric acid condensing column to be less than 4.0% by weight, and extracting the condensed liquid from the lower part of the nitric acid condensing column so as to introduce the condensed liquid into the reactor.