Nonisothermal Decomposition Kinetics of Abietic Acid in Argon Atmosphere

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 S, 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(alpha) = 2/3 alpha(-1/2) and G(alpha) = alpha(3/2). The apparent activation energy E(a) and the pre-exponential factor A were 123.44 kJ/mol and 1.78 x 10(11) s(-1), respectively. The kinetic equation can be expressed as da/dt = 1.19 x 10(11) alpha(-1/2) exp(-1.48 x 10(4)/T). The thermodynamic parameters (Delta H double dagger, Delta G double dagger, and Delta S double dagger) were calculated as well.