Mesoporous alumina–zirconia–organosilica composites for CO2 capture at ambient and elevated temperatures

Abstract

New ternary and binary composite mesostructures consisting of alumina, zirconia and organosilica with isocyanurate bridging groups were synthesized via co-condensation of suitable precursors in the presence of a triblock copolymer, Pluronic P123. The resulting binary and ternary composite mesostructures were used for CO₂ capture at low (0 °C), ambient (25 °C), and elevated (60 and 120 °C) temperatures. The CO₂ adsorption capacities measured at 1 atm for alumina–organosilica mesostructures are: 1.43 mmol g⁻¹ at 0 °C and 1 mmol g⁻¹ at 25 °C. Much higher CO₂ adsorption capacities were recorded at 1 atm for zirconia–organosilica mesostructures: 2.53 mmol g⁻¹ at 0 °C and 1.93 mmol g⁻¹ at 25 °C. This significant increase in the CO₂ uptake for zirconia–organosilica was achieved due to the development of microporosity, which was shown to be beneficial for CO₂ physisorption at low pressures. Temperature programmed desorption (TPD) was used to measure the CO₂ sorption capacities for the mesostructures studied at 60 and 120 °C. The TPD studies revealed the superior sorption capacities of zirconia–organosilica mesostructures at 60 °C (3.02 mmol g⁻¹) and 120 °C (2.76 mmol g⁻¹). Various surface hydroxyls present in alumina and zirconia are primarily responsible for CO₂ capture. These hydroxyls were shown to be essential for interactions with CO₂ by forming hydrogen carbonate and bidentate carbonate complexes. The thermal stability, corrosion resistivity, and chemical stability of the mesostructures studied make them attractive sorbents for CO₂ capture in the fossil fuel-based power plants, which generate large volumetric flow rates of flue gas at 1 atm with low partial pressure of CO₂ in the temperature range of 100–150 °C.