CO2 removal from flue gas with amine-impregnated titanate nanotubes

•Protonated titanate nanotube (PTNT) with high pore volume and large pore size was synthesized.•TETA modified PTNT exhibited 4.33 mmol/g CO2 uptake under the simulated flue gas condition.•Amine modified PTNT showed excellent stability and reusability in the cyclic operations.

The purpose of this work was to develop a new high-capacity CO2 sorbent. Protoned titanate nanotube (PTNT) with different porous textures were synthesized by a hydrothermal method and further modified with different types and amounts of amines including triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and polyethyleneimine (PEI) for CO2 adsorption. Scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, Fourier transform infrared spectroscopy and thermogravimetric analysis were used to characterize PTNT supports or amine composite sorbents. The CO2 adsorption performances of sorbents were evaluated in a fixed-bed reactor coupled with an on-line gas chromatograph using a gaseous mixture that resembled realistic flue gas. Experimental results revealed that pore volume rather than surface area of the supports is the dominant factor that determines the CO2 sorption capacities of the composite sorbents. Furthermore, the CO2 uptake capacities of the PTNT composite decreased as the size of the impregnated amines increased. The highest CO2 sorption performance attained with the sorbents is 4.33 mmol/g for a PTNT with 60 wt% TETA loading under simulated flue gas condition. It is also found that enhanced contact between CO2 and the impregnated amine was obtained when there was a small space left within the pores of the composite sorbent after amine impregnation. Besides high capacity for CO2 adsorption, the amine-impregnated PTNTs also display positive effect of moisture, good stability and reusability indicating their great potential in CO2 removal from flue gas.

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