Diethanolamine impregnated palm shell activated carbon for CO2 adsorption at elevated temperatures

• Adsorption of CO2 by amine impregnated AC was effective at 50–70 °C.
• DEA impregnated AC had higher CO2 adsorption capacity than MEA impregnated AC.
• Separation of CO2 from CO2/CH4 on DEA impregnated AC at 70 °C yielded >98% CH4.
• Regeneration of DEA impregnated AC was fast and efficient at 170 °C.

The CO2 adsorption characteristics of palm shell activated carbon (AC) impregnated with monoethanolamine (MEA) and with diethanolamine (DEA) were compared. The impregnation of the AC with 3% MEA and 3% DEA yielded loadings of 2.46 mol MEA/kg AC and 1.33 mol DEA/kg AC, respectively. The impregnation with MEA and DEA caused reductions of micropore surface areas by 52% and 11%, respectively. The saturation adsorption capacities of the AC-DEA were found to be above those of the AC-MEA at 40–70 °C. A maximum CO2 adsorption capacity of 5.3 mol/kg was obtained for the AC-DEA at 400 kPa and 70 °C. Under atmospheric pressure, the breakthrough capacities of the AC-MEA samples were lower than those of the AC-DEA samples at all temperatures investigated. The saturation capacities of the AC-MEA were also lower than for the AC-DEA by approximately the same percentages as for the breakthrough capacities. At the regeneration temperature of 160 °C, the regeneration times for the AC-MEA were found to be at least 20 min longer than the times for the AC-DEA. This difference was possibly due to higher intraparticle mass transfer resistance in the AC-MEA than in the AC-DEA. Based on both adsorption and desorption characteristics, DEA was suggested to be a more suitable impregnating agent for palm shell activated carbon.