2-05　Influence of Ammonia Treatment on the CO₂ Adsorption of Activated Carbon Prepared from Biomass

Abstract

The objectives of this investigation were to prepare an adsorbent with high CO₂ adsorption capacity and to clarify the effect of N-doping on the CO₂ adsorption of activated carbon (AC). First, N-doped AC (NH₃-AC) was prepared by NH₃ treatment of AC prepared from biomass, and its CO₂ adsorption amount was evaluated. Next, chemical and pore property analyses of the NH₃-AC were performed to clarify the effect of N-species on the CO₂ adsorption ability. CO₂ adsorption ability of AC improved by NH₃ treatment until 400°C. In contrast, the ability of NH₃-AC prepared at 500°C or higher decreased with increasing NH₃ treatment temperature. When the NH₃ treatment temperature was <200 and 700-800°C, N% in NH₃-AC increased. N1s XPS analysis showed that N in NH₃ was mainly incorporated into the AC as pyridinic-N. Pore analysis showed that micropores of 0.55-0.85nm decreased when the NH₃ treatment temperature was >500°C. It was concluded that the decrease in CO₂ adsorption ability was due to the reduction in micropores. However, no significant change was observed in the pore properties of NH₃-AC prepared at NH₃ treatment temperature of 200-400°C, suggesting that the increase in CO₂ adsorption ability was due to the formation of basic sites by the pyridinic-N introduced during NH₃ treatment.