Aluminophosphates for CO2 Separation

Aluminophosphates (AlPO4:s) with 8-ring windows, AlPO4-17, AlPO4-18, AlPO4-53, AlPO4-21, and AlPO4-25, have been synthesized by hydrothermal crystallization methods and tested for their CO2 and N2 adsorbivity. . The morphologies and structure of the as-synthesized crystals were characterized by SEM and X-ray diffraction. Pure component CO2 and N2 adsorption experiments were conduct on all the AlPO4:s up to a pressure of 760 Torr at 273 and 293 K. Both Langmuir and Toth adsorption model were used to describe the adsorption isotherms. The results showed that 8-ring AlPO4:s can sieve CO2-over-N2 for squeezed 8-ring windows, e.g. both AlPO4-53 and AlPO4-25 exhibited high CO2-over-N2 selectivity (39.5 and 30, 293k). Repeated cyclic measurements indicated that the somewhat hydrophobic nature of AlPO4:s render the material less water sensitive and could be used for long time. The CO2-over-N2 selectivity appears to be kinetically enhanced by the narrow 8-ring window apertures, and high CO2 selectivity and capacity are advantageous for potential CO2 sorbents.