Investigating the Role of Zeolite Nanocrystal Seeds in the Synthesis of Mesoporous Catalysts with Zeolite Wall Structure

Abstract

Mesoporous titania-silica catalysts were prepared by hydrothermal conversion from synthesis solutions containing a zeolite structure directing agent (TPA+) and a porogen (CTA+). Syntheses were carried out with and without addition of zeolite seeds (i.e., TS-1 and Sil-1 nanocrystals). Catalysts prepared in the presence of zeolite nanocrystal seeds have greater proportions of tetrahedrally coordinated titanium, which correlate well with the detection of zeolite SBU fragments and ring-structure by TOF-SIMS and FTIR. The incorporation of titano-silicates and zeolite structural units in the mesopore walls could explain the better activity and stability of these catalysts (Ti-MT1 and Ti-MS1) compared to the catalyst prepared by the conventional method (Ti-MCM-41). The similarity in the reactivity of catalysts prepared from TS-1 and Sil-1 nanocrystal seeds dispels the idea that the seeds are merely a source of the zeolite fragments incorporated in the pore walls but instead suggests that the seeds play an active...