Preparation of activated carbons with large specific surface areas from biomass corncob and their adsorption equilibrium for methane, carbon dioxide, nitrogen, and hydrogen

Yong Sun, Paul A. Webley

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Abstract

Activated carbons were produced from agricultural waste corncob using K2CO3 and H3PO4 as activators. The optimal activation temperature for producing the largest BET specific surface area and pore volume of the carbon was 800 °C for K2CO 3 activation (sample CK-800) and 500 °C for H3PO 4 activation (sample CP-500). The maximum BET specific surface area and pore volume of the resultant carbons were 1450 m2/g and 1.1 cm3/g for K2CO3 activation and 1069 m 2/g and 1.0 cm3/g for H3PO4 activation, respectively. The two produced carbons for high pressure carbon dioxide, methane, and nitrogen separation and hydrogen storage were closely investigated. The adsorption isotherm model based on the Toth equation together with the Benedict-Webb-Rubin (BWR) equation of state for determination of the gas phase fugacity provides a satisfactory representation of the high pressure carbon dioxide, methane, and nitrogen equilibrium adsorption. The adsorption isotherm model based on the Langmuir-Freundlich equation together with the Benedict-Webb-Rubin (BWR) equation of state for determination of the gas phase fugacity provides a satisfactory representation of the high pressure hydrogen adsorption. The preferential adsorption of CO2 on the two carbons indicates its selectivity in separation of CO2/CH4 and CO2/N2 mixtures. The hydrogen adsorption capacity of the CK-800 attained 0.34 wt % at 298 K and 60 bar, while CP-500 attained 0.29 wt % at room temperature when the full coverage of the solid surface by hydrogen is reached. The isosteric enthalpies of CK-800 for CO2, CH4, N2, and H2 are around 17, 18, 8, and 9 kJ/mol, respectively; those for CP-500 for CO2, CH4, N 2, and H2 are around 13, 12, 9, and 6.5 kJ/mol, respectively.

Original languageEnglish
Pages (from-to)9286-9294
Number of pages9
JournalIndustrial and Engineering Chemistry Research
Volume50
Issue number15
DOIs
Publication statusPublished - 3 Aug 2011

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