Pelletization of Immobilized Amine Carbon Dioxide Sorbents with Fly Ash and Poly(vinyl chloride)

A combination of coal fly ash (FA) and a polymer binder, namely, poly(vinyl chloride) (PVC), was used to pelletize immobilized amine CO2 sorbents. The pelletization of mixtures of FA and 50 wt % tetraethylenepentamine (TEPA) or ethylenimine oligomer mixture (Mw=423)/silica (EI423-S) with PVC created a rigid PVC/FA/sorbent network. The strength of the network was attributed, in part, to the hydrogen bonding of PVC with the hydroxy and amine groups of the FA and sorbent (infrared spectroscopy). Increasing the PVC molecular weight or FA content enhanced the pellet strength and reduced CO2 capture. The optimum pellet, FA/EI423-S (20/80)_PVC62 [10 wt % PVC62 (Mw=62 000), 17 wt % FA], captured 1.33 mmolCO2  g−1 and exhibited a crush strength of 1.42 MPa. The reaction between PVC and amines produced ammonium ions (−NH3+/−NH2+), which reduced the CO2 captured by the pellet during stability testing. This issue was partially resolved by replacing PVC62 with p-phenylenediamine-modified PVC62, which also enhanced the pellet CO2 capture to 1.5 mmolCO2  g−1.