Nonisothermal Decomposition Kinetics of Abietic Acid in Argon Atmosphere

Abstract

Abietic acid was isolated from rosin by means of reaction-crystallization coupled with exposure to ultrasonic waves, and it was then characterized by its specific rotation, infrared spectra, and 13 C nuclear magnetic resonance spectra. The thermal decomposition of abietic acid in argon atmosphere was studied under nonisothermal conditions using TG-DTG techniques with heating rates of 5, 10, 20, and 25 K/min. For the kinetic study, the nonisothermal kinetic parameters were obtained via the analysis of the TG-DTG curves by using the Flynn-Wall-Ozawa (FWO) method, the Kissinger method, and the integral method. The results showed that the nonisothermal decomposition mechanism of abietic acid in argon atmosphere followed Mampel Power law with n = 3/2, whose differential and integral forms were f ( α ) = 2/3 α –1/2 and G ( α ) = α 3/2 . The apparent activation energy E a and the pre-exponential factor A were 123.44 kJ/mol and 1.78 × 10 11 s –1, respectively. The kinetic equation can be expressed as d α /d t = 1.19 × 10 11 α –1/2 exp(−1.48 × 10 4 / T ). The thermodynamic parameters (Δ H ⧧, Δ G ⧧, and Δ S ⧧ ) were calculated as well.