Nanoporous Carbon Prepared from Palm Kernel Shell for CO2/CH4 Separation

The presence of impurity in biogas like CO2, H2S and H2O reduce the efficiency and heating value of this renewable energy. While removal of H2S and H2O is relatively simple, effective purification is needed to remove CO2 which presence in biogas up to 45%. The separation of CO2 from CO2/CH4 mixture can be performed by carbon-based molecular sieves. Separation by molecular sieves is based on differences in the diffusivity of CO2 and CH4 passing through the pore of the carbon. This paper discusses a preparation of porous carbon from palm kernel shell as molecular sieves and its adsorption properties (equilibrium and kinetics) and separation performance for biogas purification. Porous carbon was synthesized by carbonization under steam activation at various temperature. The properties of porous carbon were characterized by N2-sorption analysis, scanning electron microscopy and proper adsorption study (equilibrium and kinetics). The results showed that the surface area of porous carbon increased with the increasing temperature of carbonization then decreased when the temperature raised to 1000 °C. The highest surface area of 803 m2 g−1 was obtained at a temperature of 800 °C and mesoporous structures increase with increasing temperatures but dropped at temperatures above 1000 °C. In the adsorption study at 1 atm and 30 °C, the results showed that the uptake capacities of CO2 (2.0 mmol g−1) was higher than that of CH4 (1.1 mmol g−1). based on ideal adsorption solution theory, adsorption of mixed CO2–CH4 showed an adsorption capacity of 1.3 mmol g−1. The adsorption kinetics test as well as breakthrough experiment showed that CO2 can be separated from mixture of CO2/CH4 using the carbon-based molecular sieve producing high purity of CH4 (> 95%).