SSZ-13 Zeolite - Molecular Sieves

SSZ-13 molecular sieve is prepared by the hydrothermal method with silica sol, aluminium sulphate, sodium hydroxide and deionized water as raw materials, and N, N, N-trimethyl-l-adamant ammonium hydroxide as a template. Due to its specific surface area and distinctive eight-membered ring structure, SSZ-13 shows good applicability in separating N₂ from CO₂ in flue gas streams. Cation exchanged SSZ-13 can yield higher separation efficiency and it can also be used as a good catalyst in NH₃ selective catalytic reduction (NH₃-SCR), propylene production from ethylene, and methanol-to-olefins (MTO) reactions.

Introduction

The different types of molecular sieves are defined by the International Zeolite Association (IZA) by different structure codes, such as FAU, MFI, BEA and CHA. SSZ-13 is a type of zeolite with CHA topology, which was first disclosed in the 1980s by Stacey I Zones (1985, US 4544538). The structure of SSZ-13 consists of a 3D elliptic network of orderly arranged eight-membered rings with strictly alternating AlO₄ and SiO₄ tetrahedrons interconnected with oxygen bridges (Figure 1).¹ The channel size of SSZ-13 is 0.38 nm,² and its specific surface area is about 550 m²/g~700 m²/g. It is classified as a member of micropore zeolites based on the channel size.

Figure 1. The structure of SSZ-13 zeolites¹

SSZ-13 may be used as an adsorbent (an air-purifying agent, for example) or catalyst (automobile exhaust catalyst, for example) due to the excellent thermal stability resulting from its large specific surface area and distinctive eight-membered ring structure.³ The presence of AlO₄ and SiO₄ tetrahedrons in the framework results in cation exchange and acidity adjustability, which in turn makes SSZ-13 exhibit good catalytic behaviour.⁴ SSZ-13 has been applied in the catalytic cracking and hydrocracking of hydrocarbon compounds, as well as reactions of olefins and aromatics. By altering the Si/Al ratio, the nature of extra-framework cations as well as particle size, adsorption and catalytic properties of SSZ-13 can be improved and modified.

Synthesis

SSZ-13 molecular sieve is prepared by the popular hydrothermal method with silica sol, aluminium sulphate, sodium hydroxide and deionized water as raw materials, and N, N, N-trimethyl-l-adamant (TMMA⁺) ammonium hydroxide as a template. SiO₂, A1₂O₃, Na₂O and H₂O are first mixed with different molar ratios, the mixture is stirred at room temperature for 0.5 h then poured into a PTFE-lined high-pressure reactor, and crystallized at 155 ℃ for 2~5 days. The SSZ-13 molecular sieve is then prepared by pouring the obtained crystal into a beaker, heating it to 70~80℃, drying the separated crystal at 120℃ after three cycles of ion exchange with a certain amount of ammonium chloride for 2 hours followed by vacuum filtration. The final step is to remove the template and water from the crystal by temperature-programmed calcinations. SSZ-13 molecular sieves with different SiO₂/Al₂O₃ molar ratios can be obtained on our ACS Material online store.

Furthermore, other raw materials for the synthesis of SSZ-13 molecular sieves are also feasible. For example, silicon-containing compounds can be used from silica sol, silica gel, tetraethyl orthosilicate. Aluminium-containing compounds can be used from aluminium oxide, pseudo-boehmite, aluminium hydroxide, aluminium sulphate and etc. The template can be used from N, N, N-trimethyl-l-adamant ammonium hydroxide, benzyl trimethyl ammonium hydroxide and their mixture⁵. Figure 2 exhibits the standard XRD patterns of the SSZ-13 molecular sieve reported by International Zeolite Association (IZA). It indicates that the prepared crystal is a SSZ-13 molecular sieve without any mixed crystal.

Figure 2. XRD spectra of SSZ-13 molecular sieve

Applications

SSZ-13 (CHA) zeolites have gained a greater reputation over other zeolites for their high affinity toward carbon dioxide over other gases due to its unique pore structure and arrangement of cations in the framework. Increasing the electrostatic interaction between the framework and the CO₂ guest molecules by altering the Si/Al ratio, the nature of extra-framework cations, as well as the particle size, can improve adsorption properties. Such alterations make these zeolites excellent molecular sieves capable of separating CO₂ (3.3Å) from N₂ (3.6Å) in flue gas streams⁶. Additional modifications involving the use of larger cations, such as potassium and cesium in low silica CHA, were found to yield even higher selectivity of CO₂ over N₂. Specifically, the location and quantity of cations in the pores of SSZ-13 will be correlated to differences in adsorption of CO2 vs N2 via breakthrough experiments.

In addition, SSZ-13 has also received significant attention due to its excellent catalytic performance in the NH₃ selective catalytic reduction (NH₃-SCR), propylene production from ethylene, methanol-to-olefins (MTO) catalysis^7,8.

Conclusion

SSZ-13 zeolites have received significant attention due to their excellent capacity for CO₂ adsorption and separation. Furthermore, the properties of its catalytic performance in the NH₃-SCR and MTO reaction are crucial for guiding the design of better and more advanced SSZ-13 catalysts in the future.

ACS Material Products:

Molecular Sieves

• SSZ-13 Zeolite

FAQ’s:

Q. What is SSZ-13?

A. SSZ-13 is a type of microporous zeolite with a crystal structure, and it has small pores that can hold and extrude specific gas molecules. 

Q. What is zeolite 13X used for?

A. SSZ-13 is widely used in air purification, catalysis, and carbon dioxide capture because of its thermal stability and selectivity. 

Q. What is the pore size of SSZ-13 zeolite?

A. The pore size of SSZ-13 zeolite is approximately  0.38nm X 0.38nm. It’s a show because SSZ-13 has an 8-membered ring structure, which forms a 3D network of tinny channels that work very well for filtration and gas separations. 

Q. How to zeolite 13X?

A. Researchers and professionals can regenerate Zeolite 13X by heating it to remove trapped water and gases. For this process, they pass hot air or inert gas (like nitrogen) through the material at controlled temperatures until moisture is released. 

Q. What is the regeneration temperature of zeolite 13X?

A. The typical regeneration temperature for zeolite 13X is by heating, which ranges from 200°C to 315°C (392°F–599°F) to remove the absorbed gases and water from its pores for reuse. 

Q. What type of zeolite is 13X?

A. Zeolite 13X is a synthetic sodium type of faujasite (FAU) structural family, and it’s part of the aluminosilicate family and features pores about 10 angstroms. Additionally, it’s ideal for purifying gas and drying it, removing carbon dioxide and water from the natural gas and air. 

Q. Should zeolite be refrigerated?

A. No, zeolouite doesn’t refrigerate; instead, it should be stored in a dry and airtight container at room temperature. 

Q. Can plants grow in zeolite?

A. Zeolite helps the soil to improve water retention and nutrient exchange. It plays a key role in saving the plants against drought and temperature stresses.   

Q. What is the pore size of zeolite 13X?

A. The pore size of zeolite 13X is approximately 10 angstroms, which makes it perfect for adsorbing water and other organic molecules. 

Q. What is the chemical formula for zeolite 13X?

A. The chemical formula of zeolite 13 is Na₂O·Al₂O₃·(2.8 ± 0.2) SiO₂·(6–7) H₂O.

References

1. Luis, J. S., Anne, D., Anthony, K. C. “A neutron diffraction and infrared spectroscopy study of the acid form of the aluminosilicate zeolite.”Catalysis Letters, vol. 49, no. 3-4, 7 Oct. 1997, pp. 143-146., doi: 1019097019846.

2. Song, Y., Niu, X. L., Zhai, Y. C., Xu, L. Y. “Recent advance in synthesis of microporous molecular sieve.” Petrochemical Technology, vol. 34, no 9, Sep. 2005, pp. 807-812.

3. Alexis, M. W., Hillock, S. J., Miller, B., William, J. K. “Cross-linked mixed matrix membranes for the purification of natural gas: effects of sieve surface modification.”Journal of Membrane Science, vol. 314, no. 1-2, Apri. 2008, pp.193-199.,doi: 10.1016/j.memsci.2008.01.046

4. Zhu, Q. J., Kondo, J. N., Tatsumi, T., Inagaki, S., Ohnuma, R., Kubota, Y., Shimodaira, Y., Kobayashi, H., Domen, K. “A comparative study of methanol to olefin over CHA and MTF zeolites.” The Journal of Physical Chemistry C, vol. 111, no. 14, 2007, pp. 5409-5415.

5. Stephen, J. M., 2008, US 2008/0159950

6. Pham, T. D., Liu, Q. L., Lobo, R. F. “Carbon Dioxide and Nitrogen Adsorption on Cation-Exchanged SSZ-13 Zeolites.” Langmuir, vol. 29, no. 2,2013, pp.832-839.

7. Zhu, X. C., Nikolay, K., Alexey, V., Kubarev, A. B., Brahim, M., Ivan, V., Jan, P. H., Maarten, B. J. R., Eva, S., and Emiel, J. M. H. “Probing the influence of SSZ-13 zeolite pore hierarchy in
methanol-to-olefins catalysis by using nanometer accuracy by stochastic chemical reactions fluorescence microscopy and positron emission profiling.” ChemCatChem, vol. 9, no. 2, 2017, pp. 3470-3477, DOI: 10.1002/cctc.201700567

8. Bleken, F., Bjørgen, M., Palumbo, L., Bordiga, S., Svelle, S., Lillerud, K. P., and Olsbye, U., “The Effect of Acid Strength on the Conversion of Methanol to Olefins Over Acidic Microporous Catalysts with the CHA Topology.” Top. Catal. Vol .52, no. 3, 2009, pp. 218-228.