Synthesis, characterization and material evaluation of mesoporous silicas templated by a polyglycols triblock copolymer for catalytic applications

Mesoporous silicas (MS-1 to MS-9) were synthesized using a polyglycols triblock copolymer (TCP) as the surfactant. The effects of acidity, tetraethyl orthosilicate (TEOS) and TCP contents, gelling temperature and stabilities of the materials were investigated. Increasing acidity favored mesopores formation. A material with a total surface area of 760 m2 g−1, mostly in mesoporous size range was obtained at a gel composition of 1.0(TEOS):0.017(TCP):7.3HCl:115.7H2O. The controlling mechanisms for mesopores formation were mainly influenced by the TEOS:TCP ratio. Increasing the ratio from 1.56:1 to 2.09:1 promoted the mesoporosity while further increase to 2.61:1 was detrimental. An increase in TCP content to 3.5% (w/w) improved micellization. Silanols caused weak acidity of mesoporous silica, especially in highly mesoporous silicas. Thermal and hydrothermal treatments reduced mesoporosity by 19.2 and 32.6%, respectively, with the formation of secondary nanopores. At 75 MPa, MS-3 retained more than 80% of its surface area.