Preparation and Thermal Stability of Porous Silica-based Monoliths

Porous monoliths with high porosity and improved high temperature stability are required in heat insula- tion. Mesoporous SiO2 powder was synthesized from tetraethyl orthosilicate using oil-in-water microemulsions composed of non-ionic surfactant P123 and 1,3,5-trimethylbenzene as template. Porous SiO2 monoliths were pre- pared from the mesoporous SiO2 powder by dry pressing followed by sintering. Porous SiO2/Al2O3 monoliths and SiO2/TiO2 monoliths were prepared from mesoporous SiO2 powders coated with boehmite Sol and titania Sol re- spectively. XRD, SEM, TEM, N2 adsorption and Archimedes method were employed to characterize the powders and the monoliths. The thermal stability of the monoliths was studied. The porosity of the silica-based monoliths sintered at 600−700℃ is about 74%−76%. Compared with SiO2 monolith, porous SiO2/Al2O3 monolith has much better thermal stability at 800−1000℃ and porous SiO2/TiO2 monolith has an improved thermal stability at 800−900℃. It is indicated that alumina coating on porous silica particle surface can improve the high temperature stability of SiO2/Al2O3 monolith.