GB1286915A - Method of producing alkali metal hydrosulphates from formates - Google Patents

Abstract

1286915 Alkali metal hydrosulphites VIRGINIA CHEMICALS Inc 22 April 1970 [28 April 1969] 19189/70 Heading C1A Alkali metal hydrosulphites are prepared by adding a solution of SO 2 in a water-miscible alcohol and an aqueous solution of an alkali metal hydroxide and an alkali metal formate to a heated and stirred water miscible alcohol. The reaction may be carried out at superatmospheric pressure and at a temperature in the range 60-90‹ C. In an example 550 parts of methanol were placed in a reactor 10 and heated to 83‹ C. with stirring at a pressure of 25 p.s.i.g. Feed of a solution containing 540 parts NaOH and 1360 parts HCO 2 Na in 830 parts H 2 O was commenced via line 16 at a rate such that all the solution was fed to the reactor in 48 mins. 8 minutes after the commencement of this addition feed of a solution of 1856 parts of SO 2 in 3250 parts of CH 3 OH was commenced via line 18 at such a rate that 78% of this solution was added in 40 minutes. The remaining SO 2 / CH 3 OH solution was added over a further 48 minutes. Throughout these additions the temperature in the reactor was maintained at 83‹ C. and the pressure at 25 p.s.i.g. by venting CO 2 formed during the reaction, and these conditions were maintained for a further 84 minutes to complete the reaction. After cooling to 70‹ C. the reaction mixture was filtered to recover 2038 parts of anhydrous sodium hydrosulphite after rinsing with CH 3 OH and drying at 70‹ C. under vacuum. In the above description all parts are by weight.