Experimental and kinetic studies on pore development during CO2 activation of oil-palm-shell char

The results of experimental and kinetic studies on pore development during CO2 activation of char derived from oil-palm shell, an abundant solid waste in some tropical countries, were presented in this paper. CO2 was used as an activating agent instead of air because the 21% oxygen content in air would cause severe burn-off of carbon contents, resulting in detrimental effects on pore development. In preparing the activated carbon from oil-palm shell by CO2 activation, size of the starting material and CO2 gas flow rate were identified to minimize the effects of gas diffusion. Under a kinetic-controlled condition, the effects of char characteristics and activation temperature on BET and micropore surface areas, porosity and pore size distribution were investigated. For the char prepared from oil-palm shell at a low carbonization temperature of 873 K, the activated carbon with a reasonably high pore surface area and predominant microporosity was obtained. Its applications are in gas-adsorbing processes such as air pollutant removal and gas separation. A random pore model was developed to describe pore development during the carbon-CO2 reaction process. Model predictions were compared with data from thermogravimetric analyses. Kinetic study showed that the activation reaction rate was dependent on both the initial pore structure of the char and the transient pore structure which was developed progressively during the activation process.