Preparation of macroporous cordierite monoliths via the sol-gel process accompanied by phase separation

Monolithic cordierite with a cocontinuous macroporous structure has been successfully prepared by the sol-gel process accompanied by phase separation in the presence of poly(acrylamide) (PAAm). Propylene oxide (PO) acts as an acid scavenger to mediate the gelation of MgO-Al2O3-SiO2 ternary system, while PAAm works as a phase-separation inducer as well as a network former. The dried gel and that heat-treated at 800 °C are amorphous, and the sapphirine begins to precipitate at 900 °C, then transforming to orthorhombic β-cordierite at 1100 °C. After heat-treated at and above 1200 °C, the resultant β-cordierite further transforms to stable hexagonal α-cordierite. Heat-treatment changes the macroporous structure of cordierite monoliths such as macropore size and its distribution. The macroporous cordierite monolith after heat-treated at 1200 °C is found to possess a total porosity of 54%, interconnected macropores and dense solid skeletons.