Mixed‐cation LiCa‐LSX zeolite with minimum lithium for air separation

Abstract

The aim of this work was to reduce/minimize Li in Li-LSX by replacing the 70% Li 1 cations in Li-LSX that are bonded to the interior or inaccessible sites which are not used for adsorption. Thus, mixed-cation LiCa-LSX containing minimum lithium were prepared by exchanging small fractions of Li 1 into Ca-LSX, followed by dehydration under mild conditions to avoid migration/equilibration of Li cations. Comparisons of adsorption isotherms of N 2 /O 2 and heats of adsorption for the LiCa-LSX samples with that for pure-cation Li-LSX and Ca-LSX provided strong evidence that significant amounts of these Li cations indeed remained on the exposed sites (SIII). The mixed-cation LiCa-LSX samples were compared against the pure-cation Ca-LSX and Li-LSX based on their performance for oxygen production by PSA, via model simulation. The results showed that the mixed-cation LiCa-LSX samples yielded significantly higher O 2 product productivities at the same product purity and recovery than their pure-cation precursor (Ca-LSX).

Construction of a Porous Metal–Organic Framework with a High Density of Open Cr Sites for Record N2/O2 Separation

“…As a typical X type of FAU, 13X (Na‐X) exhibits a good N 2 /O 2 separation performance because of the interaction between the quadrupole moment of N 2 and the Na + that is attached to the zeolite framework, and also the suitable cages. [ 5 ] Compared to 13X, Li‐LSX (Lithium type low silicon X type zeolite molecular sieve) exhibits better air separation yields, [ 6 ] the higher N 2 adsorption and N 2 /O 2 selectivity of this material is due to the stronger interactions benefit from the larger quadrupole moment of N 2 compared to that of O 2 (−1.4 D Å for N 2 vs −0.4 D Å for O 2 ) within lithium‐containing molecular sieve channels. [ 7 ] However, the O 2 production efficiency of Li‐LSX has been already reached the limit because of the fixed structure of the X‐type molecular sieve constructed with Si, O, and Al, as the main framework, and the inaccurately controlled loading and distribution of Li.…”

Cation Ordering and Exsolution in Copper‐Containing Forms of the Flexible Zeolite Rho (Cu,M‐Rho; M=H, Na) and Their Consequences for CO2 Adsorption

“…Zeolites find widespread use as adsorbents in a range of commercially-important gas separations involving small molecules, including air separation (where N 2 /O 2 selectivity is required) and hydrogen purification (CO 2 /H 2 ). [1][2][3] Furthermore, advanced materials and chemical engineering research continues to drive improved performance in these and similar applications, [4] and also in CO 2 adsorption in natural gas and biogas upgrading (CO 2 /CH 4 ) [5,6] and carbon capture from power plant and industrial emissions (CO 2 /N 2 and CO 2 /CO,H 2 ). [7,8] The performance of zeolites in gas separation relates directly to their high chemical and thermal stability and also to their structural features: high internal surface area accessible via well-defined pores and the presence of extra-framework cations.…”

“…These cations affect their adsorption properties in a number of ways. First, the direct cation‐adsorbate interaction enables molecules to be differentiated based on their dipole moment or polarizability – cationic zeolites can separate N 2 from O 2 due to its higher polarizability, for example [1,2] . Extra‐framework cations can also control the effective pore size, if they are located close to windows, as shown by the increasing pore size of K‐, Na‐ and Ca‐forms of zeolite Linde A (known as 3A, 4A, and 5A respectively).…”

3-D Modeling of Gas–Solid Two-Phase Flow in a π-Shaped Centripetal Radial Flow Adsorber

“…It is very effective to study gas separation by numerical simulation [22][23][24][25][26]. However, most of the studies are based on the 1-D or 2-D RFA [27], and few studies have been reported in research of PSA oxygen production based on 3-D RFA.…”