Thermal oxidation process and characteristic of abietic acid and gum rosin by accelerating rate calorimeter (ARC)

Oxidative characteristic of abietic acid and rosin was investigated using an accelerating rate calorimeter, and initial oxidation temperature was calculated by temperature-time (T-t) and pressure-time (P-t) plot. The result showed that the exothermic reaction does not occur when heating to 523.15 K under nitrogen atmosphere. Under oxygen atmosphere, characteristic of oxidation reaction process was found: first abietic acid or rosin absorbed oxygen, and then an exothermic oxidation reaction has occurred. The initial exothermic temperature (T-0) of abietic acid and rosin oxidation reaction are 308.9 K and 308.92 K, respectively. The kinetics of abietic acid (or rosin) is a second-order reaction in initial oxidation reaction. The linear equation of abietic acid is Y=-43169(1/T)+11.83, and activation energy (E-a) is 35.88 kJ mol(-1) at T=309.50-339.44 K. The linear equation of rosin is Y=-7111.79(1/T)+21.43, and activation energy (E-a) is 59.13 kJ mol(-1) at T=309.52-331.31 K. The peroxides of primary oxidation product were analyzed by iodimetry, abietic acid and rosin peroxide concentration are 78.79 mg kg(-1) and 56.96 mg kg(-1), respectively, when oxidation reaction time is 8 h at 313.15 K. Therefore, oxidation reaction is easy to occur at lower temperature even at 303.15 K by iodimetry.