Method for producing purified phthalonitrile and method for purifying phthalonitrile

A method for producing a purified phthalonitrile, which comprises:

• a production reaction step for obtaining a reaction product gas comprising a phthalonitrile and a cyanobenzamide by reacting ammonia, oxygen and xylene in the presence of a catalyst;
• a collection step for obtaining a collection liquid by bringing the reaction product gas into contact with an organic solvent that has a boiling point lower than that of the phthalonitrile;
• a separation step for distilling the collection liquid by a high boiling point fraction-separating column, thereby obtaining a gas that comprises the phthalonitrile and the organic solvent from the column top, while obtaining a bottom liquid that comprises a cyanobenzamide from the column bottom, said bottom liquid having a phthalonitrile content of 90% by mass or less;
• a combustion step for subjecting the obtained bottom liquid to combustion, while being kept in a liquid state;
• and
• a rectification step for obtaining a purified phthalonitrile by removing the organic solvent from the gas obtained from the column top.