SE7707235L - METHOD FOR THE PREPARATION OF SODIUM DITIONITE FROM SULFUR DIOXIDE, SODIUM FORMAT AND SODIUM CARBONATE WITH MINIMUM QUANTITY OF SOLVENT - Google Patents

Abstract

"PRODUCTION OF SODIUM DITHIONITE FROM SULFUR DIOXIDE, SODIUM FORMATE, AND SODIUM CARBONATE WITH MINIMUM SOLVENT" A batch process having high sodium efficiency is described for producing anhydrous sodium dithionite by using minimum amounts of water and methanol while reacting sulfur dioxide with sodium formate and with sodium carbonate. Based on sodium, yields of pure sodium dithionite exceed 73%, and productivity in terms of pounds per hour per gallon of reactor volume is at least about 0.6. An improved soda-ash batch process is also described for producing anhydrous sodium dithionite by using minimum amounts of water and methanol while pre-reacting sulfur dioxide with sodium carbonate in methanol and admixing the reaction product, as a methanol slurry, with aqueous sodium formate at up to maximum concentration. This externally reacted process results in at least 25% greater yield than the standard caustic soda process while consuming less SO2 and less equivalent NaOH. A second improved process utilizes the reaction product of soda ash with a portion of the sulfur dioxide by adding sodium metabisulfite and about 30% of the sulfur dioxide to the methanol and adding the slurry to the same concentrated aqueous solution of sodium formate while adding the remaining 20% of the sulfur dioxide thereto. This MBS process produces sodium dithionite having excellent particle size and dust properties at about 20% greater yield than the standard caustic soda process while consuming less equivalent NaOH.