The effect of the carbonization/activation procedure on the microporous texture of the subsequent chars and active carbons

Chars obtained by carbonizing coconut shells at different intermediate heat treatment temperatures (IHTT) between 400 and 800 °C were activated at 800 °C in a stream of N₂+H₂O, following two distinct procedures. In the first procedure, activation follows directly the carbonization, whereas in the second procedure, the sample was first brought back to 25 °C and subsequently heated again to the activation temperature of 800 °C. The data for CO₂ adsorption at 25 °C and N₂ at −196 °C with immersion calorimetry confirms that the activated carbons derived from chars obtained at low IHTT and in two steps, present a “gate effect” for burn-offs <20% or 25%, otherwise, the final carbons present similar structural characteristics for higher burn-offs. It also appears that the evolution of the average pore width <i>L</i>₀ with the micropore volume <i>W</i>₀ follows a general pattern outlined early.