MORPHOLOGICAL AND PHASE-CHANGES OF TRANSITION ALUMINAS DURING THEIR REHYDRATION

Transition aluminas (TA), obtained by fast (0.5-1 s) calcination of gi bbsite in the temperature range 375-600-degrees-C, were rehydrated at 20, 70 and 90-degrees-C. The rehydration process was investigated usin g transmission electron microscopy, X-ray, and thermogravimetric-diffe rential thermal analysis. During rehydration, the TAs react yielding a luminium hydroxides: pseudoboehmite, boehmite, and bayerite. The phase -composition changes are accompanied by changes in particle morphology . Using transmission electron microscopy, six stages of rehydration we re found, with characteristic morphological changes occurring. The cha nges are responsible for connecting the particles into stable grains d uring the process of obtaining catalyst carriers or adsorbents from TA .