title: Aluminophosphates for CO₂ separation.
abstract: The pressure-swing adsorption method for carbon dioxide capture would ideally be facilitated by adsorbents with a high capacity and a high selectivity for CO₂. Several aluminophosphates with 8-ring window apertures (AlPO₄-17, AlPO₄-18, AlPO₄-53, and AlPO₄-25) were synthesized by hydrothermal crystallization, calcined, and their CO₂ uptake and CO₂/N₂ selectivity were studied. CO₂ and N₂ uptake was determined for pressures up to 101 kPa at 273 and 293 K. Langmuir and Toth adsorption models were used to describe the adsorption isotherms. The CO₂ and N₂ uptakes strongly indicated that the squeezed 8-ring windows of certain aluminophosphates can sieve CO₂ from a CO₂ and N₂ gas mixture. Both AlPO₄-53 and AlPO₄-25 exhibited a remarkably higher uptake of CO₂ compared to N₂. The hydrophilicity of the AlPO₄ materials was investigated by means of water adsorption, and the results showed that all of the tested aluminophosphates were less water sensitive than a benchmark zeolite (13X). In particular, AlPO₄-53 and AlPO₄-25 showed a very low degree of water uptake with up to 20-30 % relative humidity. Determination of cyclic adsorption and desorption confirmed the relatively hydrophobic nature of the aluminophosphates, which render them less energy costly for the regeneration of adsorbents.
authors.affiliation: Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University, Sweden.
authors.forename: Qingling
authors.initials: Q
authors.lastname: Liu
authors.forename: Ngo Chuen Ocean
authors.initials: NC
authors.lastname: Cheung
authors.forename: Alfonso E
authors.initials: AE
authors.lastname: Garcia-Bennett
authors.forename: Niklas
authors.initials: N
authors.lastname: Hedin
mesh_terms: D000327:Adsorption; D017607:Aluminum Compounds / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry / Q000302:isolation & purification*; D007700:Kinetics; D009584:Nitrogen / Q000737:chemistry / Q000302:isolation & purification; D010710:Phosphates / Q000737:chemistry*; D016062:Porosity
chemical_list: D017607:Aluminum Compounds; D010710:Phosphates; D002245:Carbon Dioxide; C012714:aluminum phosphate; D009584:Nitrogen