Optimization of surface silanol groups in mesoporous SBA-15 and KIT-6 materials: Effects on APTES functionalization and CO2 adsorption

Abstract

Hybridmesoporous silicas are potentially reusable promising adsorbents for CO2capture. Here SBA-15 and KIT-6 mesoporous silicas were synthetized by the sol-geltechnique using a lower calcination temperature than the conventional one: 300ºC vs. 550 ºC. This strategy aimed tomaximize the surface hydroxyl group density and consequently, to improve functionalizingagent-loading performed by the post-synthesis grafting method. The as-obtainedsilica-based samples were then characterized and applied to CO2capture. A correlation between chemical-textural properties and adsorptioncapacities of pure and modified materials was discussed. The calcined at 300 ºCsilica supports, SBA-15-300-1 and KIT-6-300-1, with high silanol group densitiesshowed better adsorption capacities overall pressure range. It is worthhighlighting that the KIT-6-300-1: APTES adsorbent had a good stabilityperformance, showing a drop of around 8 % over the aging time of a year. While,the SBA-15-300-1: APTES solid presented an excellent recycled performance after10 adsorption-desorption cycles, maintaining about 95 % of its initial capacity.