Effect of p-aminobenzoic acid on synthesizing ordered mesoporous alumina via the sol–gel method

Abstract

Ordered mesoporous alumina (OMA) samples were prepared via the sol–gel method. The triblock copolymer P123 and aluminum isopropoxide were chose as the template and aluminum source, respectively. The p-aminobenzoic acid (PABA) worked as both the interfacial protector and the assisted template. Different techniques, including X-ray diffractions, N2 physisorption measurement and transmission electron microscope, were employed to study the structural properties of the prepared samples. The results showed that the mesostructure ordering and specific surface area of the samples highly depend on the quantity of the added PABA. The samples after calcinated at 800 °C with the n(PABA)/n(Al3+) molar ratio lying in 0.30 exhibited high specific surface areas (301 m2 g−1) and retained an ordered mesostructures. It was indicated that the carboxyl groups of PABA have multiple functions in the formation of OMA with a long-range ordering and high specific surface area. The carboxyl groups of PABA can slow down the hydrolysis-condensation reaction of aluminum isopropoxide, reduce the influence of chloride ions on self-assembly process. The amino groups of PABA can also react with the hydrogen ions to form quaternary ammonium salt, which can neutralize the charges of the chloride ions, protect the balance of inorganic–organic interface, further to improve the mesostructure ordering and specific surface area of the prepared OMA.