Thermal Decomposition of NbCl₅ in Reductive Atmosphere by Using Hydrogen Gas

The present investigation is a preliminary study of metallic niobium purification process from ferroniobium, by thermal decomposition of niobium pentachloride in reductive atmosphere. Niobium pentachlorides was produced from the chloride separation and distillation of ferroniobium chlorination process. The study aims to provide some basic data related with the experimental condition of niobium pentachloride reduction. The thermal treatment process was conducted at 1373–1523 K for about 6 hours. The gas utilized in the process was 40% H₂ balanced with Ar or commercial quality (CQ) H₂ which was flowed at 0.3 l/min. The optimum experimental condition was found at the temperature of 1473–1523 K by using CQ H₂. The products of thermal decomposition consist of chips, black, gray and yellow/white powders. In this condition, chips were recovered as the highest content of niobium product, that reach at about 98 mass% niobium. The chip product is composed of a mixture phase of Nb and NbO with the average of mass fraction of about 0.85 and 0.15, respectively. NbO seems to be formed mainly due to dechlorination of niobium oxychloride compound, as an impurity of the raw material.