Structure and Sorption Dynamics of Activated Carbons from Wooden Precursors: Further Possibilities to Reveal Anisotropic Behaviors in the Carbon Skeleton

Wacha, András and Onyestyák, György and Bóta, Attila (2013) Structure and Sorption Dynamics of Activated Carbons from Wooden Precursors: Further Possibilities to Reveal Anisotropic Behaviors in the Carbon Skeleton. In: New Research on Carbon Materials. Materials Science and Technologies . Nova Science Publishers, Hauppage, NY, pp. 83-112. ISBN 9781624171871

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Abstract

The anisotropic structure of activated carbons prepared from the trunks of different woods (Norwegian spruce, European beech, Pedunculate oak) was studied by small-angle X-ray scattering recorded by a two-dimensional detector. It was found that the type of the precursor has strong influence onto the structure of the end-product for low conversion rates. Higher (cca. 50 %) burn-off results in similar features of the micropore system. The decrease of the inherent anisotropy of the precursors during activation was also observed. Specific surface and pore size distribution were characterized by the well-established methods of static adsorption measurements (N2 adsorption, iodine number, methylene-blue adsorption). A novel, dynamic technique, such as frequency-response (FR) has also been applied taken advantage of its unique potentials. The obtained three-dimensional carbonized frames exhibit very low transport diffusional resistance due to the wide one-dimensional straight transport channels of micron size in tangential direction. The evolution of propane mass transport dynamics in the three series of the activated carbon preparations provides evidence for the complex diffusion processes in the pore system of the carbonized cell walls and for the significant differences in the mass transport dynamic occuring in micropores and the lowest range of mesopores depending on evolution of pore structure determined by the history of the activation.

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