Production of biochars by intermediate pyrolysis and activated carbons from oak by three activation methods using CO₂

Biochars were produced by intermediate pyrolysis in a fixed-bed reactor, and their physicochemical properties were investigated. In addition, activated carbons were prepared by three different methods (N₂/CO₂ without cooling, N₂/CO₂ with cooling and direct CO ₂), and their properties were compared to evaluate the efficiency of the three methods. Surface areas of biochars obtained by intermediate pyrolysis at 500 and 800 °C were 107 and 249 m²/g. The maximum surface area of activated carbon (1126 m²/g) was obtained by the N ₂/CO₂ without cooling method at a final activation temperature of 900 °C and with a 1-h final activation time. Comparison between the N₂/CO₂ methods with and without cooling showed no significant difference in terms of the surface area of activated carbon. The activated carbons produced by the direct CO₂ method had a specific surface area of approximately 800 m²/g which appeared to be sufficiently high for commercial uses. The activated carbons produced had predominantly microporous structures (≤ 1 nm).