Preparation of mullite monoliths with well-defined macropores and mesostructured skeletons via the sol-gel process accompanied by phase separation

Mullite monoliths with well-defined macropores and mesostructured skeletons have been prepared via the sol gel process accompanied by phase separation in the presence of poly(ethylene oxide) (PEO). Gelation of Al2O3-SiO2 binary system with chloride salts as an additional precursor has been mediated by propylene oxide (PO) as an acid scavenger, while PEO worked as a phase-separation inducer. The dried gel and that heat-treated at 800 degrees C are amorphous, and gamma-Al2O3 or Si-Al spinel phase nanocrystals are crystallind at 900-1000 degrees C. After heat-treated at and above 1100 degrees C for 5 h, the complete crystalline mullite is generated, and the macroporous monoliths in large dimensions of more than 15 mm x 15 mm x 10 mm are obtained. Heat-treatment at 200-1400 degrees C does not basically spoil the macroporous structure of monoliths, while decreases the macropore size and significantly alters the phase compositions and micro-mesoporous structure. (C) 2013 Elsevier Ltd. All rights reserved.