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

• Biochars were successfully prepared by intermediate pyrolysis in a fixed bed.
• Microporous activated carbons were produced by different activating methods.
• The maximum surface area (1126 m2/g) was obtained via N2/CO2 without cooling.
• Direct CO2 method seemed to be very economical for producing activated carbons.

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 CO2), 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 N2/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).