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

Abstract

Mesoporous silicas are known to be high-performing water adsorbents in high humidity levels due to their large pore volumes. However, for low humidity conditions, these materials typically present a less expressive performance, which is a drawback for many applications. In the present report, mesoporous silica SBA-15 was functionalized with Al, Ti, Zr and Li in order to improve their performance in this condition. The influence of functionalization in porosity, morphology and acidic sites was investigated. Samples with an increased number of acidic sites and with higher microporosity when compared to pure silica were produced. This was responsible for their enhanced performance for water adsorption in low moisture conditions. Sample functionalized with zirconium in SBA-15 synthesis improved the water adsorption capacity of pure silica by three times, reaching up to 127 g kg −1 at a relative pressure of 0.2 and 570 g kg −1 close to saturation pressure. This sample was found to be a promising material to be applied in processes which require high adsorption capacities in both low and high water partial pressure ranges. Moreover, the understanding of the mechanisms behind the heteroatom functionalization can be applied to any silica material in order to enhance its attractiveness towards any polar molecule. Supplementary Information The online version contains supplementary material available at 10.1007/s10450-021-00336-6.

Water Vapor Adsorption by Porous Materials: From Chemistry to Practical Applications

“…In addition to the above-mentioned factors, heteroatoms were also shown to influence the water sorption behavior of mesoporous silicas. In this regard, Ribeiro et al investigated the impact of inserting heteroatoms (Al, Zr, Ti, Li) into SBA-15 on the water sorption behavior of the adsorbent. All the samples were shown to generally possess higher water uptake than the pristine SBA-15, with a more pronounced impact in the low-pressure region.…”