Importance of the Order of Addition of the Alumina Precursor and its Type Into Al-SBA-15 Mesoporous Materials for Use as Water Adsorbents

In the present report, Al-SBA mesoporous materials were investigated for use as water adsorbents. Different precursors for aluminum were investigated: aluminum sulfate and nitrate, boehmite, and aluminum tri-sec-butoxide. Furthermore, three different procedures for addition of the silica and alumina sources were tested. Samples were characterized by nitrogen adsorption to observe their textural characteristics and by thermogravimetric desorption of water to address their performance. The sample synthesized with aluminum tri-sec-butoxide as aluminum precursor and a pre-hydrolysis step of the silica source presented the highest adsorption capacity: 1057 g.kg(-1). It was also observed that water attaches more strongly to Al-containing samples than to pure silica, and that water adsorption capacity is more related to the pore volume of samples than to their surface area. This work has shown that functionalizing SBA-15 materials with aluminum is a promising strategy for producing water adsorbents with improved performance and potential for many applications.