| dc.description.abstract | The objective of this research is to achieve a high specific surface area (>3000 m2/g) that was observed in some commercial activated carbons, and at the same time able to modify the distribution of micropores and super-micropores.
The biomass-sucrose was chosen as the raw material for activated carbon in this research. The precursor was made by the hydrothermal carbonization of sucrose into sub-micron to tens of micron carbonaceous particles or their aggregates. The precursor was then directly chemically activated with KOH at high temperature in tubular furnace, or activated after further carbonization in dry nitrogen. Activated carbon powders with very high specific surface area were obtained.
The following operation variables were also studied; (1) the benefit of adding ammonium bicarbonates during the hydrothermal carbonization step. (2) The necessity of dry carbonization after the hydrothermal step and the proper temperature for such step. (3) The activation temperature, the soaking method and the amount of KOH activator used. The products were analyzed with FTIR, SEM, XRD, ASAP, ICP-AES and iodine adsorption.
We conclude that the proper process steps for producing high specific surface area activated carbon at high yield were (1) hydrothermal carbonization with the addition of ammonium bicarbonates, (2) dry carbonization at 450 °C, and (3) Chemical activation at 800 °C with KOH/C ratio of 4. The yield of our best activated carbon was 10.3 wt%, based on the amount of sucrose employed. The total pore volume was 1.517 cm3/g, and the specific surface area reached 3280 m2/g. 88.4% of the pore volume was contributed by micropores and the average pore size was 1.84 nm. The only problem was the incomplete removal of KOH, which amounted to 3.8 wt% of potassium in the final product. Therefore, although our product had a higher specific surface area than the commercial AX-21 sample, the iodine number was lower. We believe that by increasing the activation time or holding the activation temperature at 400 °C for 2 hours, such problems may be resolved.
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