Kinetics of the dehydration of boehmites prepared under different hydrothermal conditions

The kinetics of the dehydration of five boehmites, which were prepared under different hydrothermal conditions (300°C, 85 atm, 20 h — 150°C, 4.5 atm, 5 h), were studied by means of isothermal TG at an air pressure of 150 mm Hg and at a constant flow rate of nitrogen (30 ml min^?1) containing water vapor of partial pressures between 10^?4 and 23.8 mm Hg. It was found that the dehydration temperature of boehmites was lowered as the preparation conditions became more mild. Moreover, the rate-controlling step of the dehydration of boehmites varied with their preparation conditions. The water vapor pressure led to decreases in the rate of dehydration.