Method for reducing content of butenal in production process of polyvinyl alcohol

The invention discloses a method for reducing the content of butenal in a production process of polyvinyl alcohol. According to the method, the content of the butenal which enters a solvent methanol in the production process of the polyvinyl alcohol is reduced through adopting a reaction distillation method under an alkaline condition. The method particularly comprises the following steps: adding a strong alkali solution with the volume percentage concentration of 20% into the methanol containing the butenal; distilling at the temperature of 65 to 70 DEG C until the content of the butenal in the methanol is less than or equal to 0.008%; the adding amount of sodium hydroxide is 0.01% to 0.5% of the weight of the methanol. The method is simple in process and does not generate pollution.