Vapor assisted “in situ” transformation of mesoporous carbon–silica composite for hierarchically porous zeolites

Ordered mesoporous carbon–silica composite was “in situ” transformed into hierarchically porous zeolites ZSM-5 (H-ZSM-5) under water vapor, which synthesized from evaporation induced “tri-constituent” co-assembly of resin, silica and surfactant. The vapor assisted transformation was realized within 2-D hexagonally mesochannels of carbon–silica composite infused with tetrapropylammonium hydroxide at 130 °C for 72 h. The calcined H-ZSM-5-570 possesses a mesostructure with mean pore sizes of 0.6 and 9.0 nm, BET surface area of 409 cm2/g, and pore volume of 0.54 cm3/g. High-resolution TEM images of H-ZSM-5-570 display that mesoporous walls consisted of zeolite nanocrystals of about 6 nm in the same domain. Weak acidity of H-ZSM-5-570 has also been concluded from ammonia desorption measurements.

Ordered mesoporous carbon–silica composite was used as a digestible template for “in situ” transforming into hierarchically porous zeolites (H-ZSM-5) under vapor. After calcination in air, H-ZSM-5 still possesses a mesostructure with uniform pores of 0.6 and 9.0 nm. High-resolution TEM images of H-ZSM-5 displays that mesoporous walls consisted of zeolite nanocrystals of about 6 nm in the same domain.Figure optionsDownload as PowerPoint slideHighlights
► Hierarchically porous zeolites are prepared from mesoporous carbon–silica composite.
► The experiment was confined in mesochannels containing tetrapropylammonium hydroxide.
► The final samples inherit mesostructure from template and have pore size of 9.0 nm.
► HRTEM images confirm that mesoporous walls are composed of nano-zeolites of 6 nm.
► The vapor assisted zeolitization from composite can be extended to other zeolites.