A comparative study on the gas-phase and liquid-phase thermal isomerization reaction of α-pinene

In this paper, a method of preparation of ocimene is investigated, which is obtained from isomerization reaction of a-pinene. Two kinds of experimental apparatus are established for the investigation of the thermal isomerization reaction of a-pinene. The behavior of thermal isomerization reaction of a-pinene is respectively discussed in the gas phase and in the liquid phase. Under gas phase conditions, the conversion of a-pinene is 80% and the selectivity of ocimene is 30%33%. Under liquid phase conditions, the conversion of a-pinene is 60% and the selectivity of ocimene is 50%54%. According to the kinetic-molecular theory of ideal gases, two kinds of reaction models are proposed to visualize the reaction process. In addition, the mechanism and kinetics of thermal isomerization reaction of a-pinene are respectively discussed. The conclusion is that the gas phase reaction temperature is calculated to be 390-450 degrees C and the liquid phase reaction temperature is calculated to be 450-550 degrees C. From a bond dissociation energy point of view, results support the hypothesis that the reaction involves biradical intermediates. Copyright (C) 2012 John Wiley & Sons, Ltd.