Vanadyl hydrate and vanadium carbide prepn. - by vanadate ion redn., solvent extn. and stripping to form vanadyl hydrate ppte., then reacting with carbon to form carbide

摘要

Vanadyl hydrate is produced by (a) adding sulphur dioxide and a non-oxidising acid to an aq. soln. of vanadate ions to reduce vanadate to vanadyl ions; (b) extracting vanadyl ions with an organic solvent; (c) stripping the solvent to form a vanadyl hydrate ppte.; and (d) sepg. the ppte. Vanadium carbide is produced by the further steps of (e) mixing the ppte. with carbon; and (f) treating the mixt. in a furnace to form vanadium carbide. The starting soln. is pref. a leach soln. contg. Na metavanadate. In step (a), pref. gaseous SO2 and sulphuric acid are added to give a pH of 1-3 (esp. 2) or an electrochemical potential of -150 to -300 (esp. -200)mV. In a batch process, the SO2 is added first but, in a continuous process, SO2 and sulphuric acid can be added together. In step (b), extn. is pref. carried out in a counter-current manner in at least two stages, pref. with sulphuric acid addn. After the first stage to give pH 1.5-3.5 (pref. 2.5-3), pref. using a 10 vol.% soln. of di-2-ethylhexyl phosphoric acid in a 3 vol.% isodecanol/87 vol.% kerosene solvent. In step (c), vanadyl ions are pref. stripped with NH4OH to form VO(OH)2.xH2O. The resulting organic phase, aq. phase and ppte. are sepd. e.g. in a decanter-concentrater, the ppte. (which does not form an emulsion) being filtered off. The moist filter cake can then be mixed with carbon, pelletised, dried in the absence of oxygen or air and then heated in vacuo or in an inert atmos. to produce V2C.