Influence of the Compensating Cation Nature on the Water Adsorption Properties of Zeolites

Abstract

The influence of the compensating cation (Na+, Li+, Mg2+) nature on the water adsorption properties of LTA and FAU-type zeolites was investigated. Cation exchanges were performed at 80 °C for 2 h using 1 M aqueous solutions of lithium chloride (LiCl) or magnesium chloride (MgCl2). XRF and ICP-OES analyses indicate that the cation exchange yields reach values between 59 to 89% depending on the number of exchange cycles and the nature of the zeolite and cation, while both zeolites structures are preserved during the process, as shown by XRD and solid state NMR analyses. Nitrogen adsorption-desorption experiments indicate a higher available microporous volume when sodium cations are replaced by smaller monovalent lithium cations or by divalent magnesium cations because twice less cations are needed compared to monovalent cations. Up to 15% of gain in the available microporous volume is obtained for FAU-type zeolites exchanged with magnesium cation. This improvement facilitates the adsorption of water with an increase in the water uptake up to 30% for the LTA and FAU type zeolites exchanged with magnesium. These exchanged zeolites are promising for uses in water decontamination because a smaller amount is needed to trap the same amount of water compared to their sodium counterparts.

Synthesis of FAU-Type Zeolite Membranes with Antimicrobial Activity

“…Changes in peaks intensities and slight shifts are observed when sodium cations are replaced by other silver or zinc cations. These results were already observed in the literature [ 33 , 44 , 45 , 46 , 47 , 48 ] and were explained as a consequence of the difference of the scattering power which is specific to each cation and also by a slightly different sites occupation in the pores [ 33 , 48 , 49 ].…”

“…The influence of the synthesis time on the growth of the film has been studied. The synthesis time varied from 12 to 24 h. Zeolitic membrane growth and their crystallization state were investigated using X-ray diffraction (XRD) technique, which shows characteristic patterns of pure FAU-type zeolite in agreement with the corresponding pattern available (Pattern 01-070-4281 from International Center of Diffraction Data (ICDD)) [ 32 , 33 , 34 ] ( Figure 1 ) with additional peaks at high 2θ angles attributed to α-Al 2 O 3 composing the support [ 24 , 35 ]. The crystallinity of the synthesized FAU-type zeolite membranes increases progressively with the crystallization time as shown by the increase of the intensity of the XRD diffraction peaks in Figure 1 .…”

Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

“…The negative charges of zeolite frameworks are usually compensated by extra-framework mono or divalent cations. These specific characters allow zeolite exchanged by other cations [91]. In addition, the spatial confinement of zeolite pores joined with catalytically active sites in their structure endows zeolites with extraordinary shape-selective catalysis toward the formation of certain products.…”

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

“…They exhibit attractive features that are superior to those of silica, such as their unique pores and their various framework compositions accessible by changing the Si/Al ratio or by substituting silicon atoms with atoms other than aluminum such as germanium or phosphorus. Zeolites also allow incorporating various metal cations in their micropores or external surface by cationic exchange or impregnation, allowing their use in different catalytic applications [ 5 , 6 , 7 , 8 ]. Unfortunately, when used in some catalytic reaction, conventional zeolites with micron-size particles have shown diffusion limitations (high diffusion path length) that can generate a deactivation of acid sites due to the retention of carbonaceous compounds [ 9 , 10 , 11 , 12 ].…”