Studies On The Preparation And Characterization Of Microporous Activated Carbon From Coconut Shell

Coconut shell is suitable for preparing microporous activated carbons due to its excellent natural structure and low ash content. Various methods have been used to produce microporous activated carbon from it.A new method of preparing microporous activated carbon from coconut shell without using any activating agent was presented. In this method, the produced activated carbon has a very narrow pore size distribution, and the surface area is larger than 500m2/g.In another process of producing microporous activated carbon, coconut shell was oxygenated at 350~850℃ for several hours, then heated in inert environment to 850℃. By this procedure, activated carbons with surface area above 700m2/g are manufactured, and the average pore size of the carbon is smaller than 1nm. The effect of process variables such as oxygenation temperature, oxygenation time and oxygen concentration was studied in order to optimize those preparation parameters. A series of activated carbons were prepared from coconut shell by the activation with steam, KOH and a mixture of activating agents. It is difficult to get the carbon of high surface area with steam as an activation agent. Activated carbons with high surface area can be obtained with KOH as activation agent. Activation time, activation temperature and impregnation ratio are three important parameters that have significant effect on pore volume evolution. Under experimental circumstances, the optimum conditions in preparation carbons with high surface area are identified. Comparing with the activation by CO2, the activation time has been decreased effectively during the process activated by a mixture of activating agents, which also has been verified in a bench scale equipment.Adsorption of N2 at 77K and CO2 at 273.15K and pore size distribution have been studied for activated carbons made of different methods. The BET and DRK methods are used to calculate the surface area of carbon samples. A simple new method of calculating pore size distribution has been developed. In this method, local isotherms were calculated from the SLD theory, which can reasonably describe the adsorption mechanism in pores of different sizes. Comparing to the D. Cazorla-Amoros' method, the method gives more reasonable result.Adsorption of CH4 and H2 at 298.15K has been measured in activated carbons of high surface area. It shows that the adsorption capacity of carbon is determined basically by its pore volume and pore size distribution.