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The sorption and crystallographic characteristics of alumina activated in a reactor for pneumatic transport

Rožić Ljiljana (IHTM-Centar za katalizu i hemijsko inženjerstvo, Beograd)
Novaković Tatjana (IHTM-Centar za katalizu i hemijsko inženjerstvo, Beograd)
Petrović Srđan (IHTM-Centar za katalizu i hemijsko inženjerstvo, Beograd)
Čupić Željko (IHTM-Centar za katalizu i hemijsko inženjerstvo, Beograd)
Grbavčić Željko (Tehnološko-metalurški fakultet, Beograd)
Rosić Aleksandar (Rudarsko-geološki fakultet, Beograd)

Active transition alumina powders were obtained by flash calcination of gibbsite in a reactor for pneumatic transport in the dilute, two-phase flow regime in the temperature interval from 883 to 943 K with a residence time between 0.4 and 0.9 s. The results of X-ray diffraction analysis confirmed that the activated alumina samples were either microcrystalline or amorphous. From nitrogen adsorption-desorption isotherms, the specific surface areas of all samples were calculated by the BET method. Using the sorption data, the fractal dimension of the surface of the alumina samples was calculated according to a modified FHH method. By application of fractal geometry, using the values of the fractal dimension of the surface and of the specific surface area, the effective surface areas of the active aluminas were calculated for the adsorption of molecules having a cross-section area greater than that of the nitrogen molecule.

Keywords: pneumatic transport, transition amorphous aluminas, X-ray diffraction, fractal dimension