A New Approach to Obtaining Kinetic Parameters for the Non-isothermal Thermogravimetry

• Main Authors: Yue-Ching Lin, 林月琴
• Other Authors: Hsi-Jen Chen
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/24161484780067126254

碩士 === 淡江大學 === 化學工程學系 === 90 === A new method, which uses exact formula involving the E2-function, is proposed for the determination of kinetic parameters from non-isothermal thermogravimetric analysis (TGA) data. This method is applied to the pyrolysis studies of calcium hydroxide and calcium oxalate.There is one stage for degradation of calcium hydroxide. Under the heating rate of 5 K/min, we obtained the possible domain of reaction orders ranging from 1.1 to 1.3 and the activation energy was found 286.77-332.07 kJ/mole. When the heating rate is 10 K/min, reaction orders ranging from 0.9 to 1.1 and the activation energy was found 279.39-321.79 kJ/mole. For the heating rate of 20 K/min, reaction orders ranging from 0.7 to 0.9 and the activation energy was found 174.77-237.64 kJ/mole. Under the heating rate of 30 K/min, reaction orders ranging from 1.1 to 1.3 and the activation energy was found 190.91-218.29 kJ/mole. There are three stages for degradation of calcium oxalate. The first stage of the reaction (split water), we obtained the possible domain of reaction orders ranging from 0.5 to 0.7 and the activation energy was found 68.58-105.61 kJ/mole. The second stage of the reaction (split carbon monoxide), reaction order ranging from 0.3 to 0.6 and the activation energy was found 195.3-218.91 kJ/mole. The third stage of the reaction (split carbon dioxide), reaction order ranging from 0.3 to 0.8 and the activation energy was found 165.64-215.76 kJ/mole. Essentially, we find while the parameters E and A decrease as the heating rate increases, the reaction order, n, does not remain constant. The results of calcium oxalate were somewhat lower than the data from similar studies in the literature. There were no published data for comparison with the calcium hydroxide; however, we found the data obtained are somewhat lower when compared with that obtained by Coats-Redfern method and the non-linear regression method. We believe that the proposed methodology has the merits of both the simplicity in formulation and the accuracy in calculation.