The influence of preparation methods on the pore structure of alumina

Abstract

Structural characterization of eleven kinds of aluminas prepared by different methods was carried out by measurement of the adsorption of nitrogen, X-ray diffraction and scanning electron microscopy. Aluminas prepared using aqueous ammonia as precipitation reagent exhibited a single pore size distribution, the maximum being at a radius of about 20Å, whereas aluminas prepared with urea exhibited a twin peaked pore size distribution, with maxima at radii of about 20Åand 50Å. The pore structures of aluminas prepared from aluminium nitrate by pyrolysis and from sodium aluminate with carbon dioxide were similar to the former, while aluminas prepared by pyrolyses of aluminium isopropoxide and of aluminium trichloride had a pore structure similar to the latter. Based on scanning electron microscopy and nitrogen adsorption-desorption hysteresis loop observations, the crystallite structures of aluminas and pore structures were discussed in connection with the preparation methods employed.