A PROCESS FOR PREPARING AN IRON CONTAINING ZEOLITIC MATERIAL HAVING AN AEI FRAMEWORK STRUCTURE USING A QUATERNARY PHOSPHONIUM CATION

Abstract

Provided are a process for the preparation of an iron containing zeolitic material having an AEI framework structure using a quaternary phosphonium cation, as well as an iron containing zeolitic material per se as obtainable or obtained according to the process. Furthermore, an exhaust gas treatment system comprising the iron containing zeolitic material and the use of the iron containing zeolitic material as a catalyst are provided.

Claims

1. A process for the preparation of an iron-containing zeolitic material having an AEI framework structure comprising YO.sub.2 and X.sub.2O.sub.3, the process comprising: (1) preparing a mixture comprising one or more sources for YO.sub.2, one or more sources for X.sub.2O.sub.3, and one or more quaternary phosphonium (QP) cation-containing compounds as structure directing agent; (2) heating the mixture obtained in (1) and obtaining a zeolitic material having an AEI framework structure; (3) calcining the zeolitic material obtained in (2) under a hydrogen gas containing gas-containing atmosphere; and (4) subjecting the zeolitic material obtained in (3) to an ion-exchange procedure with one or more Fe.sup.2+ and/or Fe.sup.3+ containing salts, for obtaining an iron-containing zeolitic material having an AEI framework structure, wherein Y is a tetravalent element, and X is a trivalent element.

2. The process of claim 1, wherein in (3) the hydrogen gas-containing atmosphere contains comprises hydrogen gas in the range of from 20 to 100 vol.-%.

3. The process of claim 1, wherein in (3) the hydrogen gas-containing atmosphere contains comprises 1 vol-% or less of oxygen gas.

4. The process of claim 1, wherein calcination in (3) is conducted at a temperature in the range of from 400 to 850 C.

5. The process of claim 1, wherein calcination in (3) is conducted for a duration in the range of from 2 to 48 h.

6. The process of claim 1, wherein in (1) the one or more quaternary phosphonium cation-containing compounds comprise one or more R.sup.1R.sup.2R.sup.3R.sup.4+-containing compounds, wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 independently from one another stand for optionally substituted and/or optionally branched (C.sub.1-C.sub.6)alkyl.

7. The process of claim 1, wherein Y is at least one selected from the group consisting of Si, Sn, Ti, Zr, Ge, and mixtures thereof.

8. The process of claim 1, wherein X is at least one selected from the group consisting of Al, B, In, Ga, and mixtures thereof.

9. The process of claim 1, wherein the heating in (2) is conducted under autogenous pressure.

10. An iron-containing zeolitic material having an AEI framework structure obtainable and/or obtained according to the process of claim 1.

11. The iron-containing zeolitic material of claim 10, wherein the zeolitic material comprises non-framework phosphorous, wherein the molar ratio P:X.sub.2O.sub.3 of non-framework phosphorous to X.sub.2O.sub.3 of the zeolitic material is less than 1.

12. The iron-containing zeolitic material of claim 10, wherein Y is at least one selected from the group consisting of Si, Sn, Ti, Zr, Ge, and mixtures thereof

13. The iron-containing zeolitic material of claim 10, wherein X is at least one selected from the group consisting of Al, B, In, Ga, and mixtures thereof.

14. A method for the selective catalytic reduction of NO.sub.x, the method comprising: (A) providing a gas stream comprising NO.sub.x; and (B) contacting the gas stream provided in (A) with an iron-containing zeolitic material according to claim 10.

15. A process, comprising employing iron-containing zeolitic material having an AEI framework structure according to claim 10 as a catalyst and/or as a catalyst support.

Description

DESCRIPTION OF THE FIGURES

[0119] FIG. 1: shows a comparison of the XRD patterns of the H-SSZ-39(N), H-SSZ-39(P)-A and H-SSZ-39(P)-H as prepared in the examples. The X-ray diffraction pattern shown in the figure was measured using Cu K alpha-1 radiation. In the respective diffractogram, the diffraction angle 2 theta in is shown along the abscissa and the intensities are plotted along the ordinate.

EXAMPLES

Comparative Example 1: Synthesis of SSZ-39(N) Using Quaternary Ammonium Containing Structure Directing Agent

[0120] The following synthesis of SSZ-39(N) is based on the synthetic methodologies described in U.S. Pat. No. 5,958,370 and M. Moliner et al. in Chem. Commun. 2012, 48, pages 8264-8266.

Synthesis of N,N-dimethyl-3,5-dimethylpiperidinium Hydroxide (Nitrogen Containing Compound Structure Directing Agent)

[0121] N,N-dimethyl-3,5-dimethylpiperidinium hydroxide was prepared as described in M. Molner et al., Chem. Comm., 2012, 48, 8264-6266 as detailed in the Electronic Supplementary Information (ESI) thereof, under heading 1.1.2.1SSZ-39-OSDA Synthesis.

Synthesis of SSZ-39(N)

[0122] 4 g of a solution of the above obtained N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (0.56 mmol OH.sup./g) is mixed with 6.1 g of water and 0.20 g of aqeuous 1.0 M NaOH solution. 0.25 g of Ammonium exchanged Y zeolite (JRC-HY-5.3; Si/Al.sub.2O.sub.3=5.3; JGC Catalysts and Chemicals Ltd.) is added to this solution and, finally, 2.5 g of Fumed Silica (Cab-O-Sil M5D) is added. The thus obtained mixture has the molar composition: 1 Si:0.05 Al:0.15 OSDA:0.45 Na:30 H.sub.2O.

[0123] The resulting mixture is then sealed in an autoclave and heated at 150 C. and stirred at 30 rpm for 3 days. After pressure release and cooling to room temperature the SSZ-39(N) product was obtained having a SiO.sub.2 /Al.sub.2O.sub.3 mole ratio of 40.

[0124] The thus obtained SSZ-39(N) product was then calcined in air in a muffle furnace at 600 C. for 6 hours which provided the Na-SSZ-39(N).

[0125] Subsequently, the Na-SSZ-39(N) was then NH.sub.4.sup.+ ion exchanged using NH.sub.4NO.sub.3 by treating a 1:1 mixture of the Na-SSZ-39(N):NH.sub.4NO.sub.3 by slurrying in water in a weight ratio of water: Na-SSZ-39 of 25-50:1 at 95 C. for 2 hours, followed by filtration to provide NH.sub.4.sup.+ SSZ-39(N).

[0126] The thus obtained NH.sub.4.sup.+ SSZ-39(N) was then calcined in air in a muffle furnace at 600 C. for 3 hours which provided the H-form, H-SSZ-39(N).

[0127] The XRD for the H-SSZ-39(N) is provided in FIG. 1.

Comparative Example 2: Synthesis of SSZ-39(P)-A Using Quaternary Phosphonium Containing Structure Directing Agent (Calcination in Air)

[0128] The following synthesis of SSZ-39(N) is based on the synthetic methodology described in T. Sano et al., Chem. Lett. 2014, 43, page 302.

Synthesis of SSZ-39(P)

[0129] A solution of tetraethylphosphonium hydroxide is mixed with an aqueous NaOH solution and Zeolite Y (CBV-720, Zeolite, Si/Al.sub.2O.sub.3=30) for obtaining a mixture having the molar composition: 1 Si:0.067 Al:0.2 OSDA:0.1 Na: 5 H.sub.2O

[0130] The resulting mixture is then sealed in an autoclave and heated at 170 C. and stirred at 40 rpm for 5 days. After pressure release and cooling to room temperature SSZ-39(P) was obtained.

SSZ-39(P)-A

[0131] The thus obtained SSZ-39(P) product was then calcined in air in a muffle furnace at 600 C. for 6 hours which provided the sodium form, Na-SSZ-39(P)-A.

[0132] Subsequently, the Na-SSZ-39(P)-A was then NH.sub.4.sup.+ ion exchanged using NH.sub.4NO.sub.3 in accordance with the treatment described in Comparative Example 1.

[0133] The thus obtained NH.sub.4.sup.+SSZ-39(P)-A was then calcined in air in a muffle furnace at 600 C. for 3 hours which provided the H-form, H-SSZ-39(P)-A.

[0134] The XRD for H-SSZ-39(P)-A is provided in FIG. 1.

[0135] Reference Example 1: Synthesis of SSZ-39(P)-H using quaternary phosphonium containing structure directing agent (calcination under hydrogen atmosphere)

[0136] The Protocol for the synthesis of SSZ-39(P) as detailed in Comparative Example 2 herein above was repeated, except that the intermediate SSZ-39(P) was calcined in a hydrogen atmosphere for providing the sodium form, Na-SSZ-39(P)-H.

[0137] Subsequently, the Na-SSZ-39(P)-H was then NH.sub.4.sup.+ ion exchanged and calcined as described in Comparative Example 2 for obtaining the H-form, H-SSZ-39(P)-H.

[0138] The XRD for H-SSZ-39(P)-H is provided in FIG. 1.

Example 1: Iron Ion Exchange

[0139] Comparative Example 1 (H-SSZ-39(N)), Comparative Example 2 (H-SSZ-39(P)-A) and Reference Example 1 (H-SSZ-39(P)-H) samples were respectively treated with an aqueous 0.2 M iron (II) nitrate solution at room temperature for 24 hours. Subsequently, each of the samples were then heated at 500 C. for 5 hours under air, which provided Fe-SSZ-39(N), Fe-SSZ-39(P)-A and Fe-SSZ-39(P)-H samples, respectively.

[0140] It has surprisingly been found that the use of a quaternary phosphonium cation containing compound and its removal via calcination in a hydrogen atmosphere leads to an AEI type framework structure with different properties compared to the corresponding zeolitic material obtained using quaternary ammonium containing compounds as structure directing agents, in particular when subsequently subject to identical procedures for ion exchange with iron. In particular, it has unexpectedly been found that upon comparison of the zeolitic materials as obtained from Comparative Example 1 (H-SSZ-39(N)) and Reference Example 1 (H-SSZ-39(P)-H) which were subject to the same ion exchange procedure with iron, the zeolitic material obtained according to Reference Example 1 displayed a higher tendency to Fe ion cluster formation than the zeolitic material obtained according to Comparative Example 1. Furthermore, under identical conditions of ion exchange using a solution with the same iron concentration, the zeolitic material obtained according to Reference Example 1 displayed higher loadings of iron compared to the zeolitic material obtained according to both Comparative Example 1 and Reference Example 2 (H-SSZ-39(P)-A).

LIST OF THE CITED PRIOR ART REFERENCES

[0141] U.S. Pat. No. 5,958,370 [0142] Moliner, M. et al. in Chem. Commun. 2012, 48, pages 8264-8266 [0143] Maruo, T. et al. in Chem. Lett. 2014, 43, page 302-304 [0144] Martin, N. et al. in Chem. Commun. 2015, 51, 11030-11033 [0145] US 2011/0250127 A1 [0146] Martin, N. et al. in Chem Cat Chem 2017, 9, pages 1754-1757.