Synthesis Optimization of MCM-41 for CO2 Adsorption Using Simplex-centroid Design

Abstract

There is a growing concern on the relationship between anthropogenic carbon dioxide and climate changes. A promising approach is the adsorption technology using mesoporous MCM-41 materials that can be easily synthesized to depict structures adequate to the flow of gas. The aim of this study was to improve the synthesis of MCM-41 using cationic surfactant mixtures and apply the resulting materials to CO2 adsorption. To that end, the simplex-centroid design was applied to optimize CO2 adsorption from seven mesoporous MCM-41 materials synthesized by the hydrothermal method using surfactants from hydrophobic chains of different sizes. The cationic surfactants used were tetradecyltrimetylammonium bromide, cetyltrimethylammonium bromide, trimethyloctadecylammonium bromide and their mixture at ratios of 1:1 and 1:1:1. The CO2 adsorption was investigated using thegravimetric method at 298 K and pressures up to 40 bar. The resulting materials, labelled C17, C19, C21, C17C19, C19C21, C17C21 and C17C19C21, were characterized by XRD, FTIR, TG and SEM and showed significant differences in structure as well as in the mass of CO2 adsorption. The response models showed that the best combination of the surfactants resulted from C17C19 sample, which presented synergistic interactions reaching the highest value of CO2 adsorption (0.62 g CO2/g adsorbent), compared to other samples.

Keywords

• MCM-41
• CO2 adsorption
• simplex-centroid
• cetyltrimethylammonium bromide
• trimethyloctadecylammonium bromide
• tetradecyltrimetylammonium bromide