No abstract

Hollow microspheres of silica were synthesized and functionalized with amino groups to enhance carbon dioxide adsorption. Functionalization was intended to provide acid–base interaction between CO2 and amine groups. Samples were characterized by N2 adsorption/desorption isotherms at 77 K, X-ray diffraction, scanning electronic microscopy, and Fourier transform infrared spectroscopy. For adsorption experiments, both volumetric and gravimetric devices were used to quantify adsorbed CO2 as a function of pressure and temperature. CO2 adsorption isotherms obtained for the amine grafted silica confirmed the coexistence of chemical and physical adsorption sites within the material, which means that CO2 binding occurs not only by physical mechanisms on micropores but also due to interactions with amino groups. The saturation of the adsorbent with H2S to simulate the purification of natural gas or biogas slightly diminishes CO2 adsorption capacity due to competition between CO2 and H2S for amine sites. Preadsorption of H2O on the H2S saturated adsorbent did not lead to improvements in CO2 uptake. On the contrary, preloaded H2O combined with H2S seems to block some of the chemical sites involved in CO2 adsorption.