Vapor Phase Ion Exchange Research Articles

On the impact of copper local environment on hydrogen sulfide adsorption within microporous AlPO4-5

This work aims at elucidating the most active modes of copper incorporation towards H2S adsorption. Various synthesis methodologies were followed, notably, incorporation via isomorphic substitution, liquid ion exchange (LIE), vapor phase ion exchange (VIE), and nanoparticles inclusion during hydrothermal synthesis, for the introduction of copper into AlPO4-5 and SAPO-5. Techniques such as XRD and SEM/EDX, TEM, FT-IR and N2 adsorption-desorption were employed to characterize the synthesized materials. The Cu- containing materials were examined as sorbents for H2S removal via breakthrough experiments at 150 °C. The highest sulfur removal capacity was attained over the CuO nanoparticles supported in AlPO4-5 (10 % CuO/AlPO4-5), followed by a copper-based material prepared by VIE (Cu-VIE-0.2), accounting for H2S breakthrough capacities of 0.31 and 0.17 mmol ∙ g−1, respectively. The superior performance of these two materials could be ascribed to the relatively higher copper loading in the form of CuO as confirmed by XRD. Comparing the capacity per gram of active site, it was revealed that positioning Cu ions in extra-framework sites leads to an order of magnitude enhancement. This can be attributed to the possibility of a Cu ion to interact with more than one H2S molecule simultaneously unlike the other incorporation modes examined. Furthermore, copper ions incorporated into the crystal framework were found to be inactive towards H2S adsorption.

Copper-exchanged Y zeolites for gasoline deep-desulfurization

Adsorptive desulfurization is one of the most efficient methods to remove recalcitrant sulfur compounds from transportation fuels. Two π-complexation-based sorbents were studied for desulfurization of synthetic gasoline. The sorbents were obtained by ion exchanging Y zeolites with copper cations using different techniques, which includes liquid phase ion exchange (CuY1) and vapor phase ion exchange (CuY2). Preliminary kinetic and equilibrium experiments for sulfur adsorption in batch system showed that CuY1 has the greatest desulfurization capacity and selectivity. The best adsorbent, CuY1 pellet, had a dynamic adsorption and equilibrium capacity of 2.97 and 4.14 mg S/g for fixed bed column assays, respectively. Experimental data obtained to batch reactor and packed bed column have been interpreted by means of a pore diffusion model in which the mass balance to the pellets are emphasized. The model proposed was able to fit well to the experimental data. After the first thermal regeneration, the copper ion-exchanged zeolite presented a maximum recovery of 91.5%. The copper-exchanged zeolite (in pellet form) has shown good uptake rate and regenerability for desulfurization of synthetic gasoline.

The Pentatin Cation in Zeolite Y: Thallous Ion Exchange and Crystal Structure of |Sn36Cl11|[Si128Al64O384]-FAU Containing Sn512+, Sn2Cl3+, and Sn3Cl5+

Sn512+, Sn2Cl3+, and Sn3Cl5+ have replaced all of the Tl+ ions in the zeolite Tl71–Y (|Tl71|[Si121Al71O384]-FAU) by thallous ion exchange (TIE), a vapor phase ion exchange method. SnCl2(g) was allowed to react with Tl71–Y under anhydrous conditions at 673 K for 48 h. The crystal structure of the product, |(Sn512+)1.70Sn2+27.4Cl–10.8|[Si127.6Al64.4O384]-FAU per unit cell, was determined by single-crystal crystallography at 294 K using synchrotron X-radiation (Fd3m, a = 24.758(1) A). It was refined with all 1465 unique data to the final error indices R1 = 0.061 and R2 = 0.208. Its composition was confirmed by scanning electron microscopy energy-dispersive X-ray analysis. Centered tetrahedral Sn512+ clusters center 21% of the sodalite cavities. About 10 Sn2+ ions per unit cell near 12-rings are bridged by Cl– ions to form five Sn2Cl3+ clusters. Similarly, six Sn3Cl5+ clusters have formed, each containing one 6-ring and two 12-ring Sn2+ ions.

Using the Thallous Ion Exchange Method to Exchange Tin into High Alumina Zeolites. 1. Crystal Structure of |Sn2+5.3Sn4+0.8Cl–1.8|[Si12Al12O48]-LTA

Sn2+ and Sn4+ ions have replaced all of the Tl+ ions in the zeolite Tl12-A (|Tl12|[Si12Al12O48]-LTA) by thallous ion exchange (TIE), a vapor phase ion exchange method: SnCl2(g) was allowed to react with Tl12-A under anhydrous conditions at 723 K for 48 h. The tin content of the product, |Sn2+5.3Sn4+0.8Cl–1.8|[Si12Al12O48]-LTA, is 32.6 wt %, much higher than previously reported for any zeolite. Its structure was determined by single-crystal crystallography at 294 K using synchrotron X-radiation (Pm3m, a = 12.075(1) A, R1 = 0.069, R2 = 0.224), and its composition was confirmed by scanning electron microscopy energy-dispersive X-ray analysis. Sn2+ is found at four crystallographic positions, Sn4+ at two, and Cl– at two. Among the 5.3 Sn2+ ions per unit cell, 2.7 (3-coordinate) lie opposite 6-rings in large cavities, 0.3 (4-coordinate) are opposite 6-rings in sodalite cavities, 1.5 are in 8-rings, and 0.7 approach a framework oxygen atom and two chloride ions in a trigonal planar manner. Among the 0.8 Sn4+ i...

First Successful Application of the Thallous Ion Exchange (TIE) Method. Preparation of Fully Indium-Exchanged Zeolite Y (FAU, Si/Al = 1.69)

Fully indium-exchanged zeolite Y, |In+62.6(In57+)1.2|[Si121Al71O384], was prepared by thallous ion exchange (TIE), a vapor phase ion exchange method. InCl(g, 510 Pa) was allowed to react with a single crystal of Tl71–Y under anhydrous conditions at 623 K. A second crystal prepared as above was washed with deionized water and redehydrated to give |In+39.7 (In57+)4.5|[Si121Al71O384]. The structures of fully dehydrated Tl71–Y and these two forms of In–Y were determined by single-crystal crystallography using synchrotron X-radiation. Then the two In–Y crystals were subjected to scanning electron microscopy energy-dispersive X-ray (SEM-EDX) analysis. Both methods indicated that no Tl remained in the In–Y crystals. The additional steps of washing and redehydration caused some of the In+ ions in the first In–Y crystal to disproportionate to give additional In57+ clusters in the sodalite cavities and In0 atoms on the crystal surface. Most of the In+ ions in both forms of In–Y are easily accessible to guest molecu...

Using InCl vapor to ion exchange indium into zeolite Na–X. II: A single crystal structure containing (In8Cl8)16+, In57+–Cl−–In57+, and In+

Anhydrous vapor phase ion exchange (VPIE) using InCl(g) had been used to introduce indium ions into zeolite Na92–X (FAU, Si/Al=1.09); the product was In14+(In57+)4Na50+–X. Treatment of Na92–X with a lower vapor pressure of InCl(g) at lower temperatures has now yielded In6.4+(In8Cl8)1.7316+(In10Cl)1.013+Na45.6+–X; Cl− ions were retained and cationic InnClmp+ clusters have formed. Its structure was determined using single-crystal crystallography with synchrotron X-radiation and was refined in the space group Fd3¯ (a=24.890(1)Å) to the final error index R1=0.066. In8Cl816+ clusters center and extend out of 22% of the sodalite cavities. Each consists of a tetrahedrally distorted In4Cl4 cube (In–Cl=2.323(23)Å) with –In–Cl extending radially from each of its Cl− ions (the Cl–In–Cl distances are 2.302(17) and 2.406(14)Å, respectively). With Cl− ions and oxygen atoms of the zeolite framework, these indium ions, all In3+, have octahedral and trigonal bipyramidal coordination, respectively. In57+ cationic clusters center another 25% of the sodalite cavities. In57+ is a centered tetrahedron with In–In=2.745(8)Å; each terminal atom bonds to three framework oxygen atoms of a double 6-ring with In–O=2.150(5)Å and O–In–O=105.1(3)°. One terminal atom of each In57+ cluster also bonds to a Cl− ion at site I, which in turn bonds linearly to a terminal atom of another In57+ cluster. In this way the In57+ units link together in pairs to give In10Cl13+. The remaining indium cations, 6.4 In+ per unit cell, are in the sodalite cavities. Most of the Na+ ions, 25.1 per unit cell, complete the filling of the single 6-rings; the remainder are at 12-ring sites.

Using InCl Vapor to Ion Exchange Indium into Zeolite Na–X. Single Crystal Structure of |In34Na50|[Si100Al92O384]–FAU Containing In57+ and In+

Indium ions were introduced into zeolite X (FAU, Si/Al = 1.09) by anhydrous vapor-phase ion exchange (VPIE). In14+(In57+)4Na50+–X (approximate formula) was prepared by the reaction of fully dehydrated Na92+–X with 13 Torr of InCl(g) at T = 673 K. Its structure was determined using single-crystal crystallography with synchrotron X-radiation and was refined in the space group Fd3 (a = 24.996(1) A) with all 1566 unique data; the final error index R1 is 0.076. InCl(g) reacted with about 46% of the Na+ ions in the zeolite, to give In57+ (centered tetrahedral, In–In = 2.684(7) A) and In+ cations. In57+ centers exactly half of the sodalite cavities, strongly suggesting alternating occupancy; each terminal atom (at site I′) bonds to three framework oxygen atoms of a double 6-ring (In–O = 2.248(6) A and O–In–O = 102.2(2)°). The In+ ions occupy four crystallographically distinct cationic sites: 5.8(3) per unit cell are in the sodalite cavities (site I′), 2.7(7) are near single 6-rings in the supercage (site II), 2...

Using InCl Vapor to Ion Exchange Indium into Zeolite Na–Y. Single-Crystal Structure of |In25.8Cl0.8Na37.0|[Si121Al71O384]–FAU Containing In+, In3+, and In57+–Cl––In57+

Indium ions have been introduced into zeolite Y (FAU, Si/Al = 1.69) by an anhydrous vapor phase ion exchange (VPIE) method. In+16.7In3+1.1(In57+–Cl––In57+)0.8Na+37.0–Y was prepared by the reaction of fully dehydrated Na71–Y with a very low pressure of InCl(g) at T ≤ 623 K. Its structure at 294 K was determined using single-crystal crystallography with synchrotron X-radiation and was refined in the space group Fd3m̅ (a = 24.927(1) Å) to the final error index R1 = 0.038. In57+ cationic clusters center 1.6 of the 8 sodalite cavities per unit cell. In57+ is a centered tetrahedron with In–In = 2.763(7) Å; each terminal atom bonds to three framework oxygen atoms of a double 6-ring with In–O = 2.329(4) Å and O–In–O = 104.9(2)°. One terminal atom of each In57+ cluster also bonds to a chloride ion at site I, which in turn bonds linearly to a terminal atom of another In57+ cluster. In this way, the 1.6 In57+ units are linked together in pairs by 0.8 chloride ions to give 0.8 In57+–Cl––In57+ clusters per unit cell. The remaining indium cations occupy five nonframework crystallographic sites: 1.1 In3+ at site I′, 4.1 In+ at a second I′ site, 1.0 In+ at site II, 7.6 In+ at site III′, and 4.0 In+ at a second III′ site. Most of the Na+ ions, 31.0, complete the filling of site II; the remaining 6.0 are at site III.

Desulfurization of Commercial Jet Fuels by Adsorption via π-Complexation with Vapor Phase Ion Exchanged Cu(I)−Y Zeolites

Desulfurization of a commercial jet fuel by vapor phase ion exchange (VPIE) Cu(I)−Y adsorbents were studied in a fixed-bed adsorber operated at ambient temperature and pressure. When used with an activated alumina guard bed, Cu(I)−Y(VPIE) provides by far the best adsorption capacities. In general, the adsorbents tested for total sulfur adsorption capacity at breakthrough follow the order Selexsorb CDX < Cu(I)−Y(VPIE) < Selexsorb CDX/Cu(I)−Y(VPIE). The best adsorbent, Selexsorb CDX/Cu(I)−Y(VPIE) (layered bed of 25 wt % activated alumina followed by Cu(I)−Y), is capable of producing 38 cm3 of jet fuel per gram of adsorbent with a weighted average content of 0.071 ppmw-S. The sorbent is also capable of producing about 50 cm3 of jet fuel with a sulfur content of less than 1 ppmw-S. These low-sulfur fuels are suitable for fuel cell applications. Regeneration tests have shown the sorbent capacity can be fully recovered using calcination/reduction methods. Gas chromatography−flame photometric detection results s...

Desulfurization of diesel fuels by adsorption via pi-complexation with vapor-phase exchanged Cu(I)-Y zeolites.

Desulfurization of a commercial diesel fuel by vapor-phase ion exchange (VPIE) copper(I) faujasite zeolites was studied in a fixed-bed adsorber operated at ambient temperature and pressure. The zeolite adsorbed approximately five thiophenic molecules per unit cell. After treating 18 cm3 of fuel, the cumulative average sulfur concentration detected was 0.032 ppmw-S. GC-FPD results showed that the pi-complexation sorbents selectively adsorbed highly substituted thiophenes, benzothiophenes, and dibenzothiophenes from diesel, which is not possible by using conventional hydrodesulfurization (HDS) reactors. The high sulfur selectivity and high sulfur capacity of the VPIE Cu(II)-zeolites were due to pi-complexation.

Adsorption-energetic and IR spectroscopic studies of NH4 natrolite

The ammonium form of natural zeolite, natrolite, obtained by vapor phase ion exchange is similar to calcium-containing zeolites of the natrolite group in its de- and rehydration characteristics and the heats of immersion in water. The adsorption capacity and the heat of immersion in water are maximum after evacuation of the zeolite at 200 °C. The irreversible sintering of NH4 natrolite occurs above 200 °C (up to 45% at 500 °C), accompanied by the formation of hydroxyl groups.