Hierarchical aluminosilicate macrochannels with structured mesoporous walls: Towards a single catalyst for multistep reactions

Two novel and simple synthesis pathways, one surfactant-assisted and one template-free, have recently been developed for the formation of aluminosilicate macrochannels with mesoporous walls. These thermally stable materials are made of straight tubular macrochannels separated by wormhole-like mesopores. This paper gives a comparative study of the materials obtained by both ways in order to determine the role played by the surfactant. High specific surface area materials with homogeneous tubular macrochannels are spontaneously formed without needing any templating procedure. The use of a non-ionic surfactant favors the incorporation of Al atoms in tetrahedral sites and also controls the homogeneity of the mesopores. The formation of the macrochannels is believed to result from the spontaneous and strong release of alcohol molecules due to high hydrolysis and condensation rates of the inorganic sources, which creates a hydrodynamic flow, thus channels of the solvent. The mesopores are generated by interparticular voids.