A New Templated Ordered Structure with Combined Micro- and Mesopores and Internal Silica Nanocapsules

Abstract

The increasing awareness of the need to create green and sustainable production processes in all fields of chemistry has stimulated materials scientists to search for innovative catalysts supports. These new catalytic supports should allow the heterogenization of most catalytic processes, increasing the efficiency and selectivity of the synthesis and reducing waste and byproducts. Following the development of several micellar templated structures, such as M41S 1 , FSM-16, 2,3 HMS, 4,5 MSU-x, 6 and SBA-x, 7,8 it is a crucial next step to create support materials, consisting of a composite matrix with combined micro-and mesoporosities and a sufficient stability to withstand most industrial treatments. We describe in this paper the very first development of a hexagonal material with large pore diameters and thick walls (4 nm), containing internal microporous silica nanocapsules. These plugged hexagonal templated silicas (PHTS) have two types of micropores (originating from the walls and the nanocapsules respectively) and a tunable amount of both open and encapsulated mesopores. The micropore volumes have a high value (up to 0.3 cm 3 /g) and the total pore volume exceeds 1 cm 3 /g. The obtained materials are much more stable than the conventional micellar templated structures known so far, and can easily withstand severe hydrothermal treatments and mechanical pressures.

Effects of CO2 activation of carbon aerogels leading to ultrahigh micro-meso porosity

“…Similar adsorption features with a characteristic curvature in the adsorption/desorption isotherm have been described for other materials (chemically modified Vycor glass [22], porous silicon layers [23] and mesoporous silica [24]), and interpreted as pore blocking and cavitation effects occurring in pore networks where pores are connected through narrow openings.…”

Controlling Reaction Pathways for Alcohol Dehydration and Dehydrogenation over FeSBA-15 Catalysts

“…The one-step capillary condensation indicates that these materials have uniform mesopores. A two-step desorption branch has been reported before by Voort et al [27] for SBA-15. These authors proposed that cylindrical mesopores are plugged by amorphous silica particles that are created by a large excess of the silica source used in the synthesis and by rapid hydrolysis of the silicon alkoxide at very low pH.…”

The modification of MoO3 nanoparticles supported on mesoporous SBA-15: characterization using X-ray scattering, N2 physisorption, transmission electron microscopy, high-angle annular darkfield technique, Raman and XAFS spectroscopy

“…The important decrease in pore volume (mesopores and micropores) and the reduced mean pore sizes (see Table 1) indicates the filling of both the mesopores and the micropores by MoO 3 particles. The two-step desorption branch [43] and the decrease in pore volume might be attributed to the presence of a pore-blocking effect by MoO 3 , because the formation of MoO 3 particles inside the pores of SBA-15 would not significantly affect the pore volume due to the high density of MoO 3 (4,700 kg cm -3 ). This blocking effect becomes more pronounced with increasing Mo loadings.…”