Carbon dioxide capture with amino-functionalised zeolite-β: A temperature programmed desorption study under dry and humid conditions

Novel functionalised adsorbents have been synthesised by the immobilization of aminopropyltriethoxysilane (APTES) on zeolite β. APTES modified β-25 zeolite was shown to have excellent CO₂ adsorption/desorption properties, with a CO₂ adsorption capacity of up to 207 mg CO₂ g^-1 and desorption occurring from 60°C. The APTES modified zeolite-β most likely adsorbs CO₂ via both carbamate and bicarbonate mechanisms with desorption of CO₂ from the bicarbonate species occurring at a lower regeneration temperature compared to CO₂ release from anhydrous carbamates. The silicon anchoring group in APTES was found to be an important characteristic in support modification with APTES molecules forming stable covalent bonds on the surface of the support which was not always observed in non-silane molecules such as tetraethylenepentamine (TEPA) particularly regarding stable bond formation on the external surface. The use of zeolite β was found to be a good support for functional amines as well as being an inexpensive starting material for the synthesis of CO₂ adsorbents. The APTES modified zeolite β was found to be highly adsorbent compared with amine modified zeolites reported in literature. The adsorption capacity was maintained over a wide range of adsorption conditions and was found to be stable with repeated CO₂ adsorption/desorption cycles for the APTES modified β-25 zeolite materials. The addition of moisture to the gas adsorption stream was found to further improve the CO₂ adsorption capacity of the APTES modified zeolite β.