Synthesis and characterization of hierarchically structured aluminosilicates

Abstract

Catalytically active aluminosilicate materials with hierarchical porous structures are produced. A spontaneous self-assembly in aqueous solution starting from component alkoxides resulted in patterned powders without the aid of any templating agent. SEM and N2 adsorption–desorption studies demonstrated regular array of macrochannels connected with micro-mesoporous walls. FTIR of adsorbed pyridine revealed the presence of both Brønsted and Lewis acid sites. Although the synthesis procedure is markedly distinct from sol–gel phenomena, the structure and acidity in the final materials could be manipulated in terms of sol–gel parameters such as composition, pH, temperature, and addition order. Not one parameter set could be identified to provide both best structure and maximum acidity; a compromise between the two was essential. The synthesized aluminosilicate catalysts were active in the esterification reaction of palmitic acid.