Tailoring the Al-distribution and performance of mesoporous silica SBA-15 through one-pot synthesis

A series of Al-containing mesoporous SBA-15 was prepared in one-pot synthesis without adding mineral acid in order to tailor the pore structure and Al-distribution in the composites, and the impact of initial Al-content in the synthetic mixture, filtering or evaporation of the aged sample was studied in detail with XRD, N2 adsorption and 27Al MAS NMR and NH3-TPD techniques. The amount of Al embodied in SBA-15 was proportional to the initial Al-content of synthetic mixture, but less than 10%; as the Al-content increased in the initial mixture, the resulting composite had the tardily declined surface area and pore volume, while the octahedrally coordinated Al emerged apart from the tetrahedrally coordinated one. Evaporation of the aged sample made all the Al-species remain in the composite, especially suitable for preparing the sample with the initial Si/Al ratio equal to or higher than 4. Both the Al-content and the channel surface curvature of the one-pot synthesized SBA-15 determined its actual performance in adsorbing N-nitrosopyrrolidine, which could be tailored through adjusting the composition of initial mixture and the treatment of the aged sample. Moreover, a simple method, varying the flow rate of carrier gas in the instantaneous adsorption of volatile nitrosamines at 453 K, was reported to distinguish the adsorptive contribution of micropores in the mesoporous silica materials.

Adjusting the composition of initial mixture and the treatment of the aged sample can tailor the Al-content and aluminum distribution of SBA-15.Figure optionsDownload as PowerPoint slideResearch highlights
► Al-SBA-15 was one-pot synthesized without adding mineral acid.
► Al-distribution and pore structure were tailored by treatment of the aged samples.
► Evaporation is suitable for preparing sample with the initial Si/Al ratio higher than 4.
► Varying the flow rate can distinguish the adsorptive contribution of micropores.