Adsorption Behavior of Carbon Dioxide and Methane on AlPO4-14: A Neutral Molecular Sieve

AlPO4-14 molecular sieve was prepared by hydrothermal crystallization of saturated gels. The synthesized molecular sieve was characterized by X-ray diffraction and scanning electron microscopy. For the first time, the adsorption behavior of CO2 and CH4 was investigated on AlPO4-14, a neutral molecular sieve with no extra-framework cations. Adsorption isotherms of CO2 and CH4 on AlPO4-14 were examined at 273 and 300 K. Henry's law constants and isosteric heats of adsorption of all adsorbates were determined from adsorption isotherms. It was found that CO2 was strongly adsorbed on the molecular sieve, and the selectivity of CO2/CH4 can reach as high as 21.77 at 273 K. The adsorbate-adsorbent interaction and the steric effect should be responsible for the preferential adsorption of CO2 on AlPO4-14.