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

Abstract

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.

Room temperature and ambient pressure deposition of Cu-BTC MOF on SBA-15 functionalized silica supports by simple spray layer-by-layer method

“…Copper acetate anhydride (Cu(OAc) 2 ), 1,3,5-benzene tricarboxylic acid (H 3 BTC), ethanol (99.5 %) and The methylcellulose (Methocel A4M) were obtained from Sigma-Aldrich and used as received unless otherwise stated. The SBA-15 mesoporous silica powder was previously obtained employing the established synthesis [13,28] and calcined at 500 • C.…”

Influence of functionalization method on isomorphic substitution and formation of extra-framework oxides in silica for water vapor adsorption

“…It is believed that this can be attributed to the smaller pore volume observed for these samples, as seen in Table 1. The relationship between pore volume and water adsorption at high partial pressures is discussed in detail in a previous work [83].…”

“…Therefore, many new materials are being studied for water adsorption: aluminophosphates [4], titanium and zirconium silicates [5,6], mesoporous silicas [7][8][9], metal-organic frameworks [10], composite desiccants formed by hygroscopic salts in inorganic host matrices [11] and ionogels [12,13]. Among these, mesoporous silica with metallic heteroatom functionalization has been considered an interesting option for water adsorption [14]. In these materials, the water adsorption capacity is enhanced by heteroatom functionalization due to the creation of additional acidic sites on the surface of silica, which attract water more strongly [9,[15][16][17][18].…”

Impact of heteroatom addition into mesoporous silica for water adsorption in the low partial pressure range

“…The presence of a large volume of mesopores enables these materials to present adsorption capacities up to 1000 g kg −1 when exposed to high relative humidities [ 24 ]. For a low partial pressure range, SBA-15 materials were so far found to present a small adsorption capacity [ 25 ] due to their limited attractiveness towards water molecules.…”