Dehydration reactions and kinetic parameters of gibbsite

摘要

Dehydration reactions and the corresponding kinetics of gibbsite [γ-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 γ-Al(OH)_3 rises with increasing heating rate of the system. At a heating rate of 10 ℃ min~(-1), γ-Al(OH)_3 has lost part of its crystalline water, and was completely transformed into boehmite (γ-AlOOH)) at about 317 ℃. However, g-AlOOH did not lose the residual crystalline water entirely, and did not change into amorphous Al_2O_3 until the system was above 700 ℃. The kinetic energy needed to convert γ-Al(OH)_3 to γ-AlOOH, and γ-AlOOH to amorphous Al_2O_3, 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 × 10~9 and 8.30 × 10~(13), and reaction orders of 0.96 and 1.06, respectively. The kinetic parameters of dehydration reactions for γ-Al(OH)_3 obtained using the derivative thermogravimetric method (DTG) are very similar to that of obtained by DSC.