Mixed solvent reactive recrystallization of trona (sodium sesqui-carbonate) into soda (sodium carbonate anhydrate)

A new conversion process for the production of soda (Na₂CO_3(s)) from trona (Na₂CO₃·NaHCO₃·2H ₂O_(s)) and other sodium bicarbonate containing sodium carbonate sources is presented. By using a mixed solvent consisting of ethylene glycol and water, the boiling point of the solution was increased and the stability of trona could be decreased to such a degree, that it spontaneously recrystallized to anhydrous soda (Na₂CO_3(s)) and wegscheiderite (Na₂CO₃·3NaHCO_3(s)). Additionally, the sodium bicarbonate content could be completely decomposed thermally in the mixed solvent into sodium carbonate, which crystallized as stable, pure anhydrous soda. Fundamental mechanisms of this process are discussed: The stability of trona as a function of mixed solvent composition, water activity and temperature is reported. The dissolution rate, the bicarbonate decomposition rate as well as the (pseudo) solid phase conversion rate of trona were investigated as functions of mixed solvent composition and temperature. It was found that beyond a certain temperature, depending on the mixed solvent composition, the trona would convert via the (pseudo) solid state.