关键词: 淀粉, 多孔碳材料, 二氧化碳, 吸附热, 选择性, 分离

Abstract:

In this work, porous carbon materials were prepared by using starch as carbon source. The starch first went through polymerization under hydrothermal condition and followed by a KOH activation. Their structures and adsorption performances for CO₂ and CH₄ were characterized and tested. The isosteric heat of adsorption and the selectivity toward CO₂/CH₄ were estimated based on the adsorption isotherms, and the effect of carbon material structure on its adsorption properties was also discussed. The results showed that the specific surface area and pore volume of the prepared materials increased as more KOH was used, and the pore size distribution also became wider. The derived carbon material had a high specific surface area of 2972 m²·g^-1, the H₂O adsorption isotherms of the materials showed an IV-typed isotherm. It was found that the CO₂ adsorption capacity of the materials mainly depended on the cumulative pore volume with pore size less than 0.8 nm. That is, the larger the ultramicro pore volume(Vd < 0.8 nm) of the material, the greater the CO₂ adsorption capacity at 298 K and 101325 Pa. The CO₂ adsorption amount on the C-KOH-1 was 4.2 mmol·g^-1 in our work, and the isosteric heat of CO₂ adsorption was higher than that of CH₄, the selectivity toward CO₂/CH₄ is in the range of 3.7-4.26. At the same time, the water adsorption isotherms of the materials were also examined and the results showed that the materials were mainly hydrophobic, which can be a potential adsorbent being used in the reality.

Key words: starch, porous carbon materials, carbon dioxide, isosteric heat of adsorption, selectivity, separation