Chemical process deveoopment for sodium dithionite- a kinetic study of sodium formate process

Abstract

(1) The kinetics of formation of sodium dithionite has been investigated in homogeneous aqueous phase. The rate of hydrolysis of sodium formate has been found to be the rate?controlling step. The following rate equation has been proposed for the product formation: r = k · 2c?f [x? + h] where k is given by: k = 1.05 × 10¹? exp (–32,000 / RT) lit·mole?¹·min?¹ The activation energy is found to be 32 kcals/g·mole, which is consistent with the values generally observed in homogeneous reactions. (2) Aqueous?phase reaction is not advantageous for the commercial production of sodium dithionite because of low solubility of sulphur dioxide in water at the reaction temperature and also because of low equilibrium concentrations of formic acid, which is formed due to hydrolysis. (3) The use of non?aqueous solvents like methanol in the reaction medium helps to generate large concentrations of formic acid by extraction from the aqueous phase. The solubility of sulphur dioxide is also considerably enhanced by the use of methanol.