High-purity, low-Cl V2O5 via the gaseous hydrolysis of VOCl3 in a fluidized bed

Abstract

Present-day all-vanadium redox flow batteries (VRFBs) generally require high purity vanadium oxide as a raw ingredient. The chlorination procedure presents distinct technical advantages with regard to preparing high purity vanadium pentoxide (V2O5) using vanadium oxytrichloride (VOCl3) as a highly pure intermediate. To efficiently prepare high purity V2O5 from VOCl3, a single-step fluidized bed chemical vapor deposition (FBCVD) method was explored in the present work. Based on thermodynamic analyses, the direct and complete conversion of VOCl3 to V2O5 is difficult, and may result in a small amount of residual Cl in the product. Consequently, the effects of temperature and the H2O/VOCl3 molar ratio on the quantity of residual Cl were assessed. The Cl concentration was found to decrease with increasing temperature or increasing H2O/VOCl3 molar ratios. Additionally, Cl was determined to be present only in the form of ClV bonds, while ClH and ClCl bonds were not detected in a V2O5 product made at 200°C with a H2O/VOCl3 molar ratio of 18. A Cl concentration of less than 0.05wt% was obtained under the optimal synthesis conditions, demonstrating that the FBCVD method is a viable means of preparing high purity V2O5 via the gaseous hydrolysis of VOCl3.