CaCO_3分解机理和动力学参数的研究

The decomposition mechanism of CaCO_3 and its kinetics parameters

在升温速率为 5～ 30K/min的范围内利用热天平对平均粒径为 13.4 μm的CaCO3 进行了分解过程的实验研究 .应用等转化率法 ,在不假定机理函数的情况下 ,得到了CaCO3 分解的活化能随转化率变化的规律 ,并将转化率外推为零 ,得到了理论上新物相晶核形成时的活化能Eα→ 0 =2 4 3.6 2kJ/mol.同时 ,对于N2 气氛 .不同升温速率下CaCO3 的热分解 ,在假定CaCO3 分解机理函数的情况下 ,得到了 30种不同机理函数所对应的动力学参数 .将升温速率外推为零 ,得到了理论上系统处于热平衡状态下的动力学参数Eβ→ 0 与lnAα→ 0 .将Eβ→ 0 与Eα→ 0 相比较 ,确定了CaCO3 分解的最可能机理是n =2 / 3的成核与生长过程 .

Decomposition mechanism of calcium carbonate was studied by using thermogravimetric technique. The heating rate was 5～30?K/min, and the mean particle size of the sample measured by Malvern Laser Master Size Analyzer was 13.4?μm. The method of equal conversion rate, when the decomposition mechanism need not be proposed, was used to determinate the decomposition active energy value of CaCO 3. The derived value E α→0 was 243.62?kJ/mol when the conversion fraction was extrapolated to zero. The active energy values of CaCO 3 with different heating rate in nitrogen, by which the mechanism was defined, were obtained. The active energy value E β→0 , the heating rate was extrapolated to zero, was obtained. By comparing E β→0 with E α→0 , the decomposition mechanism of CaCO 3 turned out to be nuclear producing and growing process ( n =2/3).