Enhancing CO2 Adsorption and Separation Properties of Aluminophosphate Zeolites by Isomorphous Heteroatom Substitutions
Abstract
Mg, Co-substituted aluminophosphate zeolites with ERI framework topology (denoted as MgAPO-ERI and CoAPO-ERI) have been synthesized under hydrothermal conditions by using N,N,N',N'-tetramethyl-1,6-hexanediamine as organic template. Their CO2 adsorption properties are investigated in comparison to those of the pure aluminophosphate counterpart AlPO-ERI.
CoAPO-ERI shows the highest CO2 uptake of 57.3 cm(3) g(-1) (273 K and 1 bar) and the highest isosteric heat of 39.0 kJ mol(-1) among the three samples. Importantly, the incorporation of Mg(2+) and Co(2+) ions in the framework of AlPO-ERI can greatly improve the adsorption selectivities of CO2 over CH4 and N-2.
Whereafter, transient breakthrough simulations were investigated and further proved the advantages of heteroatoms for separations. These results demonstrate that isomorphous heteroatom substitutions in aluminophosphate zeolites play a key role in enhancing CO2 adsorption and separation abilities.