Kinetic analysis of formation of boron trioxide from thermal decomposition of boric acid under non-isothermal conditions

This study investigated the kinetic analysis of the dehydration process of boric acid (H3BO3) and its transformation into boron trioxide (B2O3) under non-isothermal conditions at three different heating rates (3, 5 and 10 A degrees C min(-1)) by using thermogravimetry (TG) technique in argon flow. The results obtained from the TG curves showed that this process had three different steps; hence, continuing with this study, each of these steps underwent a kinetic analysis separately. The results of these analyses showed that: In step (I), H3BO3 transformed into HBO2, and by using model-free methods and IKP methods, kinetic triplets including the activation energy, E = 55 kJ mol(-1), lnA = 5.7 min(-1), and the kinetic model g(alpha) = [- ln(1 - alpha)](1/2), Avrami-Erofe'ev, were obtained. In addition, in step (II), HBO2 transformed into H2B4O7, and also, in step (III), H2B4O7 transformed into B2O3. According to obtained results, the kinetic analysis by model-free and model-fitting methods was not separately possible because of the interstep overlap and complexity of the reactions in the last two dehydration steps.