ABSTRACT
In this study, activated carbons (AC) were produced by the activation of H3PO4 (with and without sonication) under N2 and N2+ H2O vapor at various temperatures (700–900°C). These ACs have been investigated for the effect of surface and pore property on methane adsorption at low pressure (1 atm) and 298 K. The textural, surface and porosity properties of activated carbons were determined by N2 (77 K), CO2 (273 K), and SEM-EDAX, XRD. The CH4 adsorption-desorption behavior at 298 K under low pressure was calculated using the volumetric method. According to the results obtained from N2 adsorption at 77 K, it was determined that the increase of temperature, N2+ H2O vapor and sonication increased BET surface area and pore volume of the ACs. The highest BET surface area and total pore volume were found in the H900N2+ H2O-S sample as 1881 m2/g and 1.12 cm3/g, respectively. It has been shown that narrow micropores (<10 Å) and surface oxygen groups are effective in increasing the CH4 adsorption capacity at 298 K at low pressures. Although ACs produced by N2+ H2O vapor have similar micropore volume to ACs generated by N2 activation, ACs produced with N2+ H2O vapor are found to have higher CH4 adsorption due to the lower oxygen content. The highest CH4 adsorption capacity at 298 K was found at H800N2+ H2O sample and it is 19.45 cm3/g.
Acknowledgments
This study was supported by Bülent Ecevit University Scientific Research Projects (project no: 2014-52349806-01). In addition, I would like to thank Prof. Dr. Türkan KOPAÇ who provide us the opportunity to use her laboratory.