An efficient amine-modified silica aerogel sorbent for CO2 capture enhancement: Facile synthesis, adsorption mechanism and kinetics

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At present, how to develop an economical and efficient solid adsorbent for CO2 capture at low temperature still remains a challenge. In this work, amine-modified silica (SiO2) aerogels were achieved by grafting with 3-(Aminopropyl) triethoxysilane (APTES) through a simple ambient pressure drying process, and verified as efficient adsorbents for CO2 capture. The effects of sol pH value and APTES concentration on the microstructure and CO2 adsorption property of as-prepared amine-modified silica aerogels (AMSAs) were investigated in detail. A double exponential model was proposed to reveal the kinetics adsorption mechanism of the AMSAs for the first time. It demonstrated that the as-prepared AMSAs were amorphous with a three-dimensional network structure composed of nanoparticles. And the AMSAs presented a high CO2 adsorption capacity of 3.37 mmol·g−1 at 70 °C. After 10 adsorption-desorption cycles, the AMSAs still kept 87.6% of the original capacity, exhibiting long cycle stability. Moreover, the kinetic adsorption behavior could be well simulated by the double exponential model, and the CO2 diffusion process was the speed-controlling step in the whole CO2 adsorption process. The diffusion active energy of AMSAs on CO2 capture was also calculated. This synthesis method is facile and environmental-friendly, which is of great significance to the large-scale production of SiO2 aerogel, and may provide a novel reference for the preparation of CO2 low-temperature adsorbents with high adsorption performance and good cycle stability.