Method for producing trivalent and tetravalent mixed vanadium compound and method for producing vanadium electrolyte

摘要

The present invention provides method of producing a trivalent and tetravalent mixed vanadium compound having excellent solubility with sulfuric acid directly from a tetravalent or pentavalent vanadium compound by using a reducing agent,and a method of producing a vanadium electrolyte. For example, a vanadium compound mainly containing a pentavalent vanadium compound; sulfur and concentrated sulfuric acid in molar ratios with respect to (one mol of vanadium atom in the pentavalent vanadium compound) 0.35 to 0.4:1.2 to 1.9 are kneaded into paste form, and the paste-form mixture is calcined at a temperature of not less than 150° C. to less than 440° C. so that a trivalent and tetravalent mixed vanadium compound is obtained, and a redox flow battery-use vanadium electrolyte is obtained by dissolving the trivalent and tetravalent mixed vanadium compound in a sulfuric acid solution.