Temperature-regulated gas adsorption on LTA zeolites: Observation of sorption isotherms for methane, hydrogen, nitrogen and carbon dioxide

• Adsorption of H 2 , CO 2 , N 2 , and CH 4 were investigated with zeolites LTAs. • Zeolite 5A provides the highest uptake H 2 , N 2 , and CH 4 capacity. • Zeolite 3A exhibits a temperature-dependent behaviour with H 2. • Zeolite 4A shows similar temperature-dependent adsorption with N 2. • With 3A and 4A, a temperature swing method can be used separate H 2 /CO 2 gas mixtures. Temperature-regulated gas adsorption of various zeolite LTAs with different cations of Cs 2+ , K + , Na + , and Ca 2+ (namely, Cs-A, 3A, 4A, and 5A) was analysed in the presence of different gas molecules of H 2 , CO 2 , N 2 , and CH 4 for pressures up to 800 kPa and temperatures ranging from 77.15 to 363.15 K. Over the range of test conditions, zeolite 5A (containing Ca 2+ cations) exhibited the highest uptake at 800 kPa for CO 2 , H 2 , CH 4 , and N 2 , with capacity values of 5.69 mmol.g −1 , 1.14 mmol.g −1 , 6.60 mmol.g −1 , and 6.10 mmol.g −1 , at 298.15 K and 201.15 K respectively. Zeolite 4A (containing Na + cations) exhibited 0.74 mmol.g −1 for H 2 adsorption at 201.15 K, and 800 kPa. In contrast, pores were inaccessible to H 2 on ion-exchange Cs-A zeolite at a temperature range of 77.15–343.15 K, due to larger cation Cs 2+ (CsA) comparison with Na + (4A). Interestingly, zeolite 3A (containing K + cations) showed a negligible capacity for the larger gas molecules, CH 4 and N 2 , ascribed to the pore space blocked by the larger K + cations (relative to the smaller Na + and Ca 2+ cations). Zeolite 3A exhibited a temperature-dependent behaviour (i.e., presumably a “trapdoor” effect) with H 2 wherein adsorption was negligible at 77.15 K, but was significant above approximately 200 K. For N 2 , zeolite 4A exhibits similar temperature-regulated adsorption characteristics (i.e., presumably a “trapdoor” mechanism as well). These zeolite materials used in various temperature swing processes could be particularly beneficial in natural hydrogen production (with H 2 /N 2 separation with 3A), the production of synthetic fuels from CO 2 /H 2 mixtures (with both 3A and 4A), CO 2 capture from waste streams, and applications for H 2 /N 2 separation.