高温热处理对活性炭纤维微孔及表面性能的影响

Pore size and surface properties of activated carbon fibres modified by high temperature treatment

研究了1173K高温改性处理对沥青基活性炭纤维吸附性能、孔径分布、微孔结构和表面化学的影响。低温(77K)N2吸附结果表明热处理后活性炭纤维比表面积略有下降,通过密度函数理论解析活性炭纤维全孔范围的孔分布得出活性炭纤维表面孔径大于1.0nm的微孔明显减少,微孔孔径更加集中于0.5nm～1.0nm,从而提高了活性炭纤维的碘吸附值。X射线衍射分析表明活性炭纤维是乱层石墨结构,热处理使活性炭纤维类石墨微晶碳层面的层间距下降,X光电子能谱分析表明热处理后活性炭纤维表面的含氧官能团C=O和COOH的含量变化不大,而呈碱性酚羟基C OH含量的明显下降使活性炭纤维表面碱性降低。

The micropore structure of activated carbon fibres (ACFs) can be modified by heat treatment. Pitch-based ACFs were heat treated at 1173 K and the effects of heat treatment on adsorption properties, pore size distribution, micropore structure and surface chemistry were studied, using (77 K) N-2 adsorption, density functional theory (DFT), X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS). Results show that although high temperature treatment decreases the BET surface area, the micropore size is much more uniform and narrow down to the range 0.5 to 1.0 nm and therefore the iodine adsorption capacity is obviously enhanced. XRD shows that the carbon layers in the resultant ACF are still turbostratic but d(002) decreased due to the high temperature treatment. XPS analyses indicate that surface alkalescence of ACF decreases with the reduction of the surface oxygen-containing group C-OH.