KINETICS OF THERMAL-DISSOCIATION OF AMMONIUM METAVANADATE

The solid products of thermal decomposition of ammonium metavanadate c an be used as catalysts in many important, processes, and a knowledge of the dynamics of these processes is therefore essential. The thermal dissociation of ammonium metavanadate was studied under non-isotherma l conditions in air atmosphere. This process occurred in three steps u nder the applied experimental conditions, and was associated with the elimination of ammonia and water below 330 degrees C and with the form ation of nitrogen oxides above 330 degrees C. The kinetics of particul ar stages of (NH4)(2)OV2O5 decomposition was evaluated from the dynami c mass loss data by means of the integral method, with applycation of the Coats and Redfern approximation. The first stage of decomposition to ammonium hexavanadate is governed by a random nucleation model, the second step by a three-dimensional diffusion or contracting volume mo del, and the last stage again by a random nucleation model. The appare nt activation energies found for the particular stages were 144.97, 37 8.31 or 184.40 and 260.65 kJ mol(-1), respectively.