Microwave-Assisted hydrothermal carbonization and characterization of Amazonian biomass as an activated carbon for methane adsorption

Abstract

Activated carbons were prepared from Amazonian biomass by means of microwave-assisted hydrothermal carbonization and activated with CO2. These materials were investigated as methane adsorption sorbents. The prepared samples were submitted to textural investigations and comprehensive characterizations using scanning electron microscopy, Transmission electron microscopy, energy dispersive X-ray diffraction, Raman and FTIR spectroscopy. Values of specific surface areas and pore volume ranged from 0.35 cm3/g to 0.50 cm3/g and from 840 to 1096 m2/g respectively, this value is likely attributed to the high selectivity of CO2/CH4 and methane adsorption by combining large surface area, narrow micropores. The results of the stability tests attested to the robustness of activated carbon as an adsorbent under the specified operating conditions The assessment, which included measurements after the first cycle as well as the fifth, tenth, and fifteenth cycles, revealed a remarkable consistency in its adsorption behavior, with a maximum recorded standard deviation of 0.05. Isosteric heat showed a decline in Qst from 21 to 20 as surface coverage increases from 0.1 to 0.5, indicating the energetic transformation occurring during the adsorption process. Activated carbon AC C shows the highest methane capture capacity of 150 V/V at 40 bar pressures and CH4/CO2 0.49 selectivity up to 1 bar.