地开石热分解过程及非等温动力学研究

用傅利叶变换红外光谱仪研究了湖南晨溪地开石热分解前后的红外光谱,加热反应后原矿粉红外光谱在3620.73、3695.34cm-1处的地开石羟基伸缩振动吸收峰和在916.06、1009.33cm-1处的羟基弯曲振动吸收峰都消失,表明其质量失重为羟基脱水.在298～1123K,用TG DTA综合分析仪研究了地开石在程序升温下的热分解行为.结果表明,在600～1000K,其质量损失为13.7%,与理论计算的脱水量相近.根据TG DTG曲线上的基础数据,联合运用积分法(Coats Redfern方程、HM方程、MKN方程)和微分法(Achar方程)对地开石脱水反应过程进行了非等温动力学研究,结果显示,地开石热分解反应的机理函数为F2,求得反应的动力学参数:反应级数为2.1,表观活化能为131.62kJ/mol,指前因子为108.3s-1.作为一种验证方法,使用Ozawa方程对不同升温速率TG曲线上相同分解率处的绝对温度进行线性回归分析,求出的表观活化能值为133.07kJ/mol,此值不仅与上述各种方法的表观活化能值相近,也与确定机理函数时的表观活化能值相近.说明实验求得的动力学参数在很大程度上是可靠的.

Thermal Decomposition and Non-isothermal Kinetics of Dickite

Fourier-transform infrared emission spectroscopy was used to study the dehydroxylation behavior of the thermal decomposition of dickite from Chenxi, Hunan Province, China. Dehydroxylation of dickite was followed by a loss of intensity of the 3620.73, 3695.34 cm~-1 OH-stretching bands and 916.06, 1009.33 cm~-1 OH-bending bands. The thermal decomposition was investigated by thermogravimetric analysis (TGA). A good agreement is found with TG curves of dickite and the mass loss is 13.7% (close to the theoretical value). The non-isothermal kinetics of the thermal decomposition of dickite was studied in TG-DTG curves over the temperature range from 298 K to 1123 K by thermogravimetry and differential thermal analysis in air. Mathematical analysis of TG-DTG data using the integral methods (Coats-Redfern equation, HM equation, MKN equation) and differential method (Achar equation) shows that the thermal decomposition of dickite accords F2 mechanism. The kinetic parameters such as the activation energy (E=131.62 kJ/mol), pre-exponential factor (A=10~8.30 s~-1) and reaction order (n=2.1) are reported. The Ozawa method was used to analyse the activation energy of the same sample at different heating rate and gave 133.07 kJ/mol. The kinetic parameters calculated from different equation are rather close to each other.