Dehydration reactions and kinetic parameters of gibbsite

Dehydration reactions and the corresponding kinetics of gibbsite [gamma-Al(OH)(3)] were analyzed using non-isothermal thermoanalysis and the Kissinger equation. It is concluded that the starting temperature of the dehydration reaction of gamma-Al(OH)(3) rises with increasing heating rate of the system. At a heating rate of 10 degrees C min(-1), gamma-Al(OH)(3) has lost part of its crystalline water, and was completely transformed into boehmite (gamma-AlOOH)) at about 317 degrees C. However, gamma-AlOOH did not lose the residual crystalline water entirely, and did not change into amorphous Al2O3 until the system was above 700 degrees C. The kinetic energy needed to convert gamma-Al(OH)(3) to gamma-AlOOH, and gamma-AlOOH to amorphous Al2O3, was calculated by differential scanning calorimetry (DSC) with activation energies of 108.50 and 217.24 kJ mol(-1), pre-exponential factors of 2.93 x 10(9) and 8.30 x 10(13), and reaction orders of 0.96 and 1.06, respectively. The kinetic parameters of dehydration reactions for gamma-Al(OH)(3) obtained using the derivative thermogravimetric method (DTG) are very similar to that of obtained by DSC. (C) 2010 Published by Elsevier Ltd and Techna Group S.r.l.