GB1309982A - Method of producing alkali metal hydrosulphites from formates - Google Patents

Abstract

1309982 Alkali metal hydrosulphites VIRGINIA CHEMICALS Inc 25 May 1971 [16 Nov 1970] 16891/71 Heading C1A In a process for the production of alkali metal hydrosulphites solutions of (a) SO 2 in a water miscible alcohol and (b) alkali metal hydroxide and formate in water are added to (c) a heated stirred water miscible alcohol containing as an added reactant a formate derived from the alcohol. The preferred temperature range is 60-90 degrees at a preferred press. of 10-50 p.s.i.g. Thus in an example using the apparatus illustrated 1100 p.b.w. of methyl alcohol and 150 p.b.w. methyl formate in reactor 10 were stirred at 83‹ C. and 25 p.s.i.g. A solution of 650 p.b.w. NaOH and 1190 p.b.w. in 880 p.b.w. H 2 O was prepared by heating to 160‹ C. and this solution was added to the reactor via line 16 over 60 minutes. Six minutes after commencement of this addition, addition of a solution of 1920 p.b.w. SO 2 in 2700 p.b.w. CH 3 OH was commenced via line 18 at such a rate that when all the aqueous NaOH/HCO 2 Na soln. had been added 26% of the SO 3 /MCOH solution remained, and this was then added over a further 104 minutes. Throughout these additions the conditions within the reactor were maintained at 83‹C./25 p.s.i.g. and such conditions were maintained for a further 76 minutes before cooling the reactor contents using coils 12 and then the slurry was removed via line 28, the product rinsed with 1200 p.b.w. methanol and dried at 70‹ C. under vacuum to yield 2269 p.b.w. of 92% anhydrous sodium hydrosulphite. During the reaction the pressure was maintained by venting CO 2 evolved and other vapours evolved, e.g. HCO 2 CH 3 were condensed in condensers 22 and 29 and returned to the reactor.