ϕ–pH diagrams and kinetics of V2O3 prepared by solution-phase hydrogen reduction

Abstract

Solution-phase hydrogen reduction (SpHR) was introduced into V2O3 preparation to overcome disadvantages of traditional reduction roasting, which include a long process, high energy consumption, and generation of pollution. The research mainly focuses on ϕ–pH diagrams and kinetics of SpHR. Thermodynamic analysis of ϕ–pH diagrams for the V–H2O system demonstrates that V2O3 preparation via SpHR requires a high temperature, a high vanadium concentration, and sufficient hydrogen in acidic solution. Kinetic analyses show that the activation energy of V2O3 preparation via SpHR is 38.0679 kJ/mol, indicating that the reduction is controlled by a combination of interfacial chemical reaction and internal diffusion. Effects of H2 partial pressure (slope K=0.05246) on the reaction rate is not as significant as the vanadium concentration (K=1.58872). V2O3 crystals with a purity of 99.59% and a vanadium precipitation rate of 99.83% were obtained under the following conditions: pH=5–6, c(V2O5)=0.5 mol/L, p(H2)=4 MPa, m(PdCl2)=10 mg, T=250 °C, and t=2.5 h.