Abstract:
The kinetics of chloridization of finely divided as well as granulated nickel oxide:by gaseous HCl were studied in the temperature range 150 degrees C to 400 degrees C. The rate of chloridization depended upon temperature, partial pressure of HCl, and granule size. The conversion of NiO to NiCl2 follows the logarithmic rate law or a pore-blocking model, which is attributed to the large increase in molar volume of the product phase. The blocked pores decreased the diffusion of gaseous reactant through the product layer. This observation has been supported by the low value of activation energy, the high order of reaction with respect to the partial pressure of HCl (g), and a slope value of -2 for the log-log plot of rate constant vs grain size. The morphological characteristics of both unreacted and chloridized nickel oxide have been studied with the help of a scanning electron microscope.