Development of mesoporous magnesium oxide–alumina composites for CO2 capture

• High surface area MgO–Al2O3 was obtained by Pluronic P123-assisted self-assembly.
• Preparation of MgO–Al2O3 sorbents is simple and feasible.
• Almost 3 mmol/g of CO2 was captured by mesoporous MgO–Al2O3 at 120 °C.

Mesoporous magnesium oxide–alumina composites were synthesized by evaporation induced self assembly (EISA) in the presence of triblock copolymer Pluronic P123 in absolute ethanol solution. These mesostructures were prepared using Al(NO3)3∙9H2O and Mg(NO3)2·6H2O as alumina and MgO precursors, respectively. Block copolymer was completely removed by thermal treatment of as-synthesized samples at 350 °C in flowing nitrogen. Thermally treated composites displayed relatively high specific surface area and large pore volume. Temperature programmed desorption (TPD) was used to investigate the active sites available on the surface of the aforementioned samples for CO2 sorption at 120 °C. Magnesium oxide-alumina composite samples showed an enhanced CO2 uptake under flue gas conditions (100–150 °C). The sample synthesized from Al(NO3)3∙9H2O) only showed adsorption capacity of about 1.30 mmol/g. Incorporation of 10 molar% of MgO did not significantly increase the CO2 uptake of the alumina-based composite; however, incorporation of 30 molar% of MgO increased CO2 uptake up to 2.08 mmol/g. An increase of the MgO content in the composite caused a gradual enhancement in the CO2 uptake; namely, the composite with 70% of MgO loading showed 2.87 mmol/g CO2 uptake. High thermal and mechanical stability of the composites studied as well as their low cost, good resistance to the corrosion and oxidizing environment make these materials, especially MgO-rich composites, attractive candidates for CO2 capture at flue gas conditions.

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