Polyethylenimine covalently grafted on mesostructured porous silica for CO2 capture

Polyethylenimine (PEI) has been grafted on a 2D hexagonal mesostructured porous silica of MCM-41 type (LUS silica) using 3-glycidoxypropyltrimethoxysilane (GTMS) as a grafting agent to develop sorbents for CO2 capture. The advantage of this tether is to create ethanolamine units upon reaction of the epoxy group with the amine functions of PEI. Two synthetic routes have been explored: (1) reaction of GTMS and PEI and then grafting on a calcined MCM-41 silica (M-1), and (2) grafting of GTMS on the silica and then reaction with PEI (M-2). In both cases, the grafted solids are well structured according to the XRD patterns. The amounts of glycidoxypropylsilane (GS) and PEI are 14 and 9 wt%, and 21 and 16 wt%, respectively, for samples M-1 and M-2. The CO2 adsorption capacity of both materials has been tested at 303 K and 101 kPa and compared to a bare LUS silica sample impregnated with 25 wt% PEI (M-3-25). Samples M-1 and M-2 containing ethanolamine groups show higher CO2 adsorption capacities, with loading of about 150 and 134 mgCO(2)/gPEI (36 and 43 mgCO(2)/g-sorbent), respectively, while the CO2 adsorption capacity was about 55 mgCO(2)/gPEI (14 mgCO(2)/g-sorbent) for the impregnated solid M-3-25.