Adsorption and Separation of CO₂on KFI Zeolites: Effect of Cation Type and Si/Al Ratio on Equilibrium and Kinetic Properties

Abstract

Selective separation of CO2 is becoming one of the key technologies in the (petro-) chemical industry. This study focuses on the adsorption and separation of CO2 from CH4 on a new low-silica (LS) type of the eight-membered ring KFI zeolite. A series of alkali (Li, Na, K) and alkaline-earth (Mg, Ca, Sr) exchanged samples of the new LS KFI were synthesized and characterized. LS Li-KFI showed the largest pore volume, whereas LS Na-KFI and LS K-KFI were inaccessible for Argon at 87 K. Adsorption of CO2 at 303 K demonstrated the dominant quadrupolar interaction on alkali-exchanged LS KFI samples. LS Li-KFI showed the largest capacities upon high pressure isotherm measurements of CO2 (4.8 mmol/g), CH4 (2.6 mmol/g), and N2 (2.2 mmol/g) up to 40 bar at 303 K. The performance of the new LS KFI was compared to a KFI sample (ZK-5) with a higher Si/Al ratio. Isotherm measurements and dynamic breakthrough experiments demonstrated that ZK-5 samples show larger working capacities for CO2/CH4 separations at low pressure. Li-ZK-5 and Na-ZK-5 show the highest capacities and high selectivities (similar to benchmark 13X).

Deblocking effect of carbonates and hydrogen carbonates in the alkali form zeolites with narrow pores

“…For CH 4 respective activation barriers at 100 kPa in r2KCHA and r2CsCHA forms are overcome at 279 and 343 K, respectively [3]. The relevant results of the CO 2 /CH 4 breakthrough experiments with low silica (LS) MKFI-5, M = Li, Na, K, Mg, Ca, Sr, have not shown a drastic fall of the barriers for such CH 4 passing in the presence of CO 2 [10]. But in three cases of the LS LiKFI-5, LS CaKFI-5 ( Fig.…”

“…Growing interest to the alkali exchanged form zeolites with narrow pores and 8R windows, which control molecular passing, can be explained by a possibility to develop a superior adsorbent for gas mixture separation [1][2][3][4][5][6][7][8][9][10][11]. For example, high CO 2 /N 2 separation coefficients have been predicted in KCHA [1] and have been evaluated from individual isotherms of CO 2 and N 2 in NaKA [2].…”

“…For example, high CO 2 /N 2 separation coefficients have been predicted in KCHA [1] and have been evaluated from individual isotherms of CO 2 and N 2 in NaKA [2]. Later, other KFI, ZK-5 [10,12] and RHO [4][5] zeotypes with the narrow pores have been involved into consideration of the effects which are important for adsorption: (a) the 8R flexibility in RHO [4,5] and (b) the cationic positions in CHA [1,3,6,13], KFI, ZK-5 [10,12], or RHO [4]. While the separation of CO 2 mixtures remains one of the central directions for future zeolite applications, where both the (a, b) effects are important, we would like to pay attention to the aspect of the formation of the carbonates whose influence has not been yet accurately estimated and whose relevance can be questioned.…”

The impact of surface chemistry and texture on the CO2 uptake capacity of graphene oxide

“…For this reason, we initiated the present study by evaluating two materials that are accessible to the community and of relevance to the analysis of CO 2 uptake by nanostructured carbon materials. The first, zeolite 13X, is a well-known molecular sieve with outstanding capability to adsorb CO 2 [31,32]. The second, is a metrology-grade, certified reference material (for chemical analysis) of single-walled carbon nanotubes [33].…”

Carbon dioxide adsorption using amine-functionalized mesocellular siliceous foams

“…In the past decade, development of processes based on solid adsorbents has been considered as alternative separation technologies for postcombustion CO 2 capture. Porous solids such as zeolites [2][3][4][5], activated carbons [6][7][8][9], hydrotalcites [10][11][12][13][14], metal-organic frameworks [15][16][17] and mesoporous silicas [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] are good candidates for capturing CO 2 .…”