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.