Adsorption of methane and carbon dioxide on activated carbon and metal organic frameworks

Abstract

Natural gas has gain popularity for transportation among other fuels since it is the cleanest burning fossil fuel. However, the important challenge for utilizing natural gas is its comparatively low volumetric energy storage density. Consequently, a suitable natural gas storage is needed. Adsorbed natural gas (ANG) is an interesting alternative because it could be expected to reduce the cost and potential damage from compressed natural gas (CNG) and liquefied natural gas (LNG) technology. Comparative adsorption of methane and carbon dioxide on activated carbon ZIF-8, UiO-66, and MIL-53 (Al) was investigated at 35 °C and up to 100 psi. The addition of PVDF in ZIF-8 and activated carbon were also studied including 75 wt% ZIF-8, 50 wt% ZIF-8, 25 wt% ZIF-8, 50 wt% ZIF-8, and 25 wt% ZIF-8. The result shows that the methane and carbon dioxide adsorption increase with the pressure. MIL-53 shows the highest methane and carbon dioxide adsorption. The high surface area and micropore volume corresponds to the high methane and carbon dioxide adsorption. However, the high micropore volume to total pore volume ratio also contributes to higher methane adsorption in the case of ZIF-8 and UiO-66. ZIF-8 has higher methane adsorption than UiO-66 although they have about the same surface area and micropore volume. On the contrary, UiO-66 has higher carbon dioxide adsorption than ZIF-8 affecting from chemical properties such as an open metal site and an organic ligand. Moreover, ZIF-8 has the highest CH4/CO2 selectively because it has high surface area, high micropore volume, high micropore volume to total pore volume ratio, and proper open metal site and organic ligand.