Kinetics studies of recrystallization process of metallic catalysts for ammonia synthesis

The kinetics of the process of recrystallization of iron-based and cobalt-based catalysts for ammonia synthesis were investigated by measuring the specific surface area using thermal desorption method. During sintering of the catalysts in constant temperature their surface areas asymptotically approach a non-zero value, which is the residual surface area (Sr). An equation analogous to the General Power-Law Equations model (GPLE) was used to quantitatively describe this process. It was found that the recrystallization rate for both catalysts depends exclusively on their initial surface area and the sintering temperature. The apparent activation energy of the recrystallization process was calculated, which amounted to 50 kJ mol−1 for both catalysts.