About the thermal stability and pore elimination in the ordered hexagonal mesoporous silica SBA-15

• Published in: Microporous and mesoporous materials Vol. 190; pp. 227 - 233
• Main Authors: da Silveira, T., Awano, C.M., Donatti, D.A., de Vicente, F.S., Vollet, D.R.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15-05-2014; Elsevier
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Nitrogen adsorption; Ordered mesoporous silica; Pore elimination; Porous materials; SAXS; Surface physical chemistry; Thermal stability; Nitrogen adsorption; Pore elimination; Ordered mesoporous silica; Thermal stability; SAXS; Binary compound; Nitrogen; Small angle X ray scattering; Porous material; Silica; Mesoporosity; Adsorption; Pore
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2014.02.023

•Ethanol-washed and vacuum dried SBA-15 was heat treated at several temperatures.•The volume of the ordered hexagonal pores diminishes with temperature.•The porosity elimination can be described by a geometric model of contracting area.•An activation energy of 92kJ/mol was estimated for the process.
Ordered hexagonal mesoporous silica was prepared using Pluronic P123 template and removal of the polymer by washing in ethanol. The thermal stability and the pore elimination was studied under heat treatment by a fixed time at 500, 600, 750, 825, 900, and 1050°C. The most part of the porosity is built up by cylindrical pores belonging to the ordered hexagonal 2D pore structure. The lattice parameter and the pore volume of the hexagonal 2D structure diminish regularly with the temperature up to 900°C. All porosity is eliminated at 1050°C. The porosity elimination occurs in a mechanism described by a geometric model of contracting area, in which the diameter of the cylindrical pore diminishes while its length is kept constant. An activation energy of (92±2) kJ/mol was estimated for the process. The ordered porosity of an ethanol-washed and vacuum dried sample was found to be even larger with a narrower pore size distribution in comparison to a sample directly calcined at 500°C without previous washing in ethanol.