Effect of silica removal and steam activation on extra-porous activated carbons from rice husks for methane storage

Porosity is a key factor for achieving superior methane (CH4) uptakes in adsorbed natural gas (ANG) applications. For preparation of carbonaceous adsorbents, physical activation is adopted on commercial production due to the simplicity of process and well-developed microporosity. However, significant challenges remained in physical activation process with low porosity. In this study, extra-porous activated carbon was prepared by additional simple silica removal process. This simple strategy provides not only extra-porosity, but also expansion of existing micropores. It should be highlighted, because of there are only few works regarding the pore expansion, whereas there have been many studies on micropore generation. Moreover, a synergetic increase in specific surface area occurs according to the proposed strategy. The synthesized materials show a high specific surface area (1343 m2/g) and CH4 uptakes of 4.25 mmol/g at 25 °C and 35 bar. This simple and prospective strategy for enhancing the textural properties provides great potential for various applications of rice husks-derived activated carbon as a porous material.