Hydrophobic interface-assisted synthesis of K2CO3/Al2O3 adsorbent pellets for CO2 capture

[Display omitted] •K2CO3/Al2O3 adsorbent pellets were prepared via the hydrophobic interface-assisted method.•High temperatures make hydrophobic powders lose their hydrophobicity.•Residual hydrophobic powders inhibits the diffusion of water molecules due to hydrophobicity.•The detrimental effect of the hydrophobicity exceeds that of high temperature. Suitable molding and granulation methods are crucial, and an outstanding sphere structure can play a better role in the future scale-up industrial application of K2CO3-based CO2 adsorbent. Water will form a large contact angle on the surface of hydrophobic solution and become sphericity water. In this work, hydrophobic powders (polyethylene (PE), TiO2, and SiO2) were selected in the hydrophobic interface-assisted method. The CO2 adsorption capacity of TiO2 pellets is 0.50 mmol/g, while that of PE pellets is 0.24 mmol/g, and finally that of SiO2 pellets is 0.36 mmol/g. Then, experiment proved that high temperature (>500 ℃) makes the hydrophobic powders (i.e, TiO2 and SiO2) lose hydrophobicity which make water molecules diffuse faster, while PE is completely decomposed at high temperature. Compared with the pellets calcined at 300 ℃, the TiO2 pellets calcinated at 500 ℃ have an adsorption capacity of 0.70 mmol/g, which is over 1.72 times that of the original pellets, and the other two hydrophobic surfaces are also improved to some extent. Additionally, the appropriate ratio of low-temperature pore forming agent (i.e., urea) can help improve the adsorption performance, while excessive addition will lead to poor CO2 adsorption performance. In addition, the K2CO3/Al2O3 pellets also exhibited desirable mechanical properties, with an optimal compressive strength of 41 Mpa. Therefore, the loss of hydrophobicity leads to more active diffusion of water molecules, which may provide a new idea for the future development of CO2 adsorbents and other areas.