Closed-Loop K<sub>2</sub>CO<sub>3</sub> Activation of Biochar for Coproduction of Microporous Carbon and Syngas
Yafei Shen, Cyrus Foo Jit Loong, Wenqian Chen, Liya Ge, Wei Ping Chan, Andrei Veksha, Grzegorz Lisak
Abstract
The current work systematically studied the technical feasibility of potassium-looping activation of biochar using K 2 CO 3 for the coproduction of highly microporous carbon and syngas. Compared with the solid mixing method, the impregnation method showed a higher biochar activation efficiency and produced a higher quality of activated carbon. By the impregnation method, a high yield of activated carbon (60 wt %, per biochar mass) was achieved under the optimal conditions, such as an activation temperature of 800 °C, a mass ratio of biochar to K 2 CO 3 (1:1), and a retention time of 3 h. The activated carbon with a high specific surface area (1091 m 2 /g) and a high microporosity (98%) was obtained. Besides, during the biochar activation process, syngas (CO/H 2 molar ratio of 1.0–1.5 and yield of ∼23 wt %) was generated. The yield and surface area of activated carbon were not obviously reduced after water leaching within three cycles. The potassium-looping system was evaluated to recover and reuse biochar activation agent within subsequent cycles.