High temperature CO₂ adsorption by mesoporous silica supported magnesium aluminum mixed oxide

Magnesium aluminum mixed oxide (Mg-Al-O) was deposited in various weight percentages into SBA-15 mesoporous silica through excess solution impregnation of magnesium and aluminum nitrate salts and subsequent high temperature calcination. In all the syntheses the Mg:Al mole ratio was fixed at 2. High temperature CO₂ uptake capacity of these composites were measured in the temperature range 300-400°C and were compared with the capacity of the unsupported mixed oxide phase with same Mg:Al mole ratio of 2. An improvement in the specific equilibrium capacity as well as uptake kinetics for CO₂ was observed in the composite adsorbent after an optimum loading of the mixed oxide. The result could be explained on the basis of better accessibility of the active sites for CO₂ adsorption following dispersion of the mixed oxide on to the high surface area SBA-15 support. The CO₂ adsorption capacity is higher than recent reports of Mg-Al-O supported on graphene oxide and CNT where there is additional complication of support degradation during thermal decomposition of Mg/Al salt precursors to corresponding metal oxides during adsorbent preparation.