In order to reduce the sorbent preparation cost and improve its volume-based sorption capacity, the use of an inexpensive and commercially available silica gel was explored as a support to prepare a solid polyethylenimine sorbent (PEI/SG) for CO2 capture from flue gas. The effects of the pore volume and particle size of the silica gels, molecular weight of polyethylenimine and amount of polyethylenimine loaded, sorption temperature and moisture in the flue gas on the CO2 sorption capacity of PEI/SG were examined. The sorption performance of the developed PEI/SG was evaluated by using a thermogravimetric analyzer and a fixed-bed flow sorption system in comparison with the SBA-15-supported polyethylenimine sorbent (PEI/SBA-15). The best PEI/SG sorbent showed a mass-based CO2 sorption capacity of 138 mg-CO2/g-sorbent, which is almost the same as that of PEI/SBA-15. In addition, the PEI/SG gave a high volume-based sorption capacity of 83 mg-CO2/cm3-sorbent, which is higher than that of PEI/SBA-15 by a factor of 2.6. (C) 2011 American Institute of Chemical Engineers AIChE J, 58: 24952502, 2012