GB1144118A - Thiourea dioxide - Google Patents

Abstract

1,144,118. Preparation of thiourea dioxide. FMC CORP. 27 Sept., 1967, No. 43984/67. Heading C2C. A continuous process for the production of amino-imino-methane-sulphinic acid (thiourea dioxide), comprises continuously feeding an aqueous solution of thiourea containing from 0À7 to 10% by weight of thiourea to a reaction zone, concurrently continuously feeding an aqueous solution of hydrogen peroxide into the reaction zone and producing an intimate mixture of these reactants, the amount of H 2 O 2 thus introduced being such as to produce a reaction mixture containing from 1À5-12% by weight of H 2 O 2 and the hydrogen peroxide and thiourea being reacted in approximately stoichiometric proportions, continuously withdrawing reaction mixture from the reaction zone, maintaining the reaction zone at a temperature within the range of from 5-80‹ C., controlling the rate of flow of the aqueous solution of thiourea and the stream of H 2 O 2 and the rate of withdrawal of the reaction mixture from the reaction zone so that the residence time of the reactants and the reaction product in the reaction zone is within the range 0À1 1 sec.- 10 mins., and the pH of the reaction mixture is from 3-7, cooling the reaction mixture immediately upon withdrawal from the reaction zone thus forming a slurry of amino-iminomethane sulphinic acid crystals, and continuously separating the amino-iminomethanesulphinic acid crystals from the slurry.