Porosity of alumina gels prepared from solutions of aluminium nitrate in various alcohols

Abstract

AbstractMercury porosimetry and nitrogen adsorption measurements have been made on a series of alumina gels prepared by the passage of gaseous ammonia into solutions of aluminium nitrate nonohydrate in various alcohols. The values of surface area calculated from mercury intrusion curves and nitrogen isotherms (BET method) are in reasonable agreement with the macroporous gels, but the restricted penetration of mercury into the mesopore structures results in larger values of areas when calculated by nitrogen adsorption. Marked differences have been obtained in the pore size distribution of gels prepared in various alcohols, including the isomers of propanol and butanol. The alcohol appears to play a double role: (a) by replacing water at the solid‐liquid interface (it promotes aggregation‐cementation); (b) by decreasing the solubility (it reduces the rate of Ostwald ripening). Propan‐1‐ol and propan‐2‐ol tend to promote aggregation‐cementation and hence the formation of a well‐defined mesopore structure, whereas butan‐1‐ol and heptan‐1‐ol appear to favour particle growth and the development of larger pores.