PRODUCTION OF SURFACTANT

PROBLEM TO BE SOLVED: To prevent harm caused by a by-product peroxide in a surfactant production process including a bleaching step under acidic conditions by keeping the concentration of a by-product peroxide in a liquid phase and the oxygen concentration in a gas phase in the bleaching step, each at a specified value or lower. SOLUTION: The concentration of a by-product peroxide in a liquid phase is kept at 1,500 ppm or lower; and the oxygen concentration in a gas phase, at 15 vol.% or lower. The by-product peroxide concentration in a liquid phase can be adjusted by controlling the reaction temperature in the bleaching step, the temperature being preferably 90 deg.C or lower. The oxygen concentration in a gas phase is adjusted by feeding an inert gas before or in the bleaching step. Preferably, the oxygen concentration is also kept even after the bleaching step. Preferably, hydrogen peroxide is used as the bleaching agent. This invention is especially suitable for a bleaching step of an anonic surfactant such as an α-sulfo-fatty acid ester salt or an alkylsulfate.