The vanadium method for making potassium carbonate

KVO3 was prepared in 90.2% yield from pure V2O5 and solid KCl (30% excess) in 4 h/773 K on a 3-mm SiO2 as carrier (120% excess) and with steam (10-fold excess). The V2O5 was replaced by a spent V catalyst, 0.710-1.400 mm, precalcined 8 h/1123 K, and the reaction was run 6 h/823 K with 140% KCl and steam (10-fold excess) to give KVO3 in 83% yield. A saturated brine prepared from the KVO3 was carbonated to 100%. Solubility isotherms studied in the KVO3-NH4HCO3-NH4VO3-KHCO3-H2O system at 303 K showed NH4VO3 and KHCO3 to form a permanent pair and their crystallization planes to meet NH4VO3 was the least soluble salt and its crystallization field was the largest. The carbonated suspension is to be filtered to collect NH4VO3 and the filtrate containing most KHCO3 and minor amounts of NH4VO3 and KVO3 to be evaporated to remove NH3 and CO2 and calcined to yield K2CO3. No wastes are generated.