Preparation and Characterization of Macroporous Mayenite Monoliths

Macroporous mayenite monoliths were successfully prepared via Sol-Gel process accompanied by phase separation using calcium chloride dihydrate and aluminum chloride hexahydrate as raw materials, propylene oxide (PO) as a gelation agent, and poly (ethylene oxide) with average molecular weight of 100,000 as a phase separation inducer. In addition, glycol was used as a chelating agent and formamide as a drying control chemical additive. Macroporous monoliths were characterized by scanning electron microscope(SEM), mercury porosimetry, and X-ray diffraction (XRD). The result shows that the addition of PEO induces phase separation; the amount of PEO and the ratio of ethanol to water have an important effect on porous structure, and monolithic mayenite with co-continuous marcoporous structure is obtained at appropriate addition of PEO and solvent as well as gelation temperature. The dried gels are amorphous, and transform to Ca12Al14O32Cl2 after heat-treatment at 1000 degrees C in air, while the co-continuous macropores are retained. The monolith after heat-treatment has narrow pore size distribution of 1-2 mu m and porosity of 73.0%. The monoliths before and after heat-treatment possess smooth and dense skeletons.