Kinetic Study on the Thermal Dehydration of CaCO_3 centre dot H_2O by the Master Plots Method

摘要

Thermal dehydration process of calcium oxalate monohydrate,CaC_2O_4 centre dot H_2O,was reinvestigated from a viewpoint of reaction kinetics.On the basis of data of thermo-gravimetry,kinetic analysis was performed under nonisothermal conditions using an integral composite procedure,which includes a integral isoconversional method and an integral master plots method.The results of the integral isoconversional method of TGA data at various heating rates suggested that dehydration of CaC_2O_4 centre dot H_2O followed a single step with an activation energy of 99.02 +-2.61 kJ/mol,and from the master plots method,the reaction was described by an R_n model.Finally,it was estimated that the pre-exponential factor A =(2.82 +-1.81)X10~9 s~(-1),and the kinetic exponent n =2.3 +-0.2.The results of nonisothermal kinetic analysis of the thermal dehydration reactions of CaC_2O_4 centre dot H_2O suggested that the integral composite procedure be very successful in evaluating kinetic parameters and describing kinetic model of solid-state reactions.