Iron-containing aluminosilicate zeolites and methods of making and using same
View Patent ↗There is disclosed iron-containing aluminosilicate zeolites having both framework iron and iron cations on the ion-exchange sites. There is also disclosed a direct synthesis method of making an iron-containing aluminosilicate zeolite, which does not require the use of an intermediate step, such as ion-exchange or impregnation. In addition, there is disclosed a method of using the iron-containing aluminosilicate zeolite disclosed herein in a selective catalytic reduction reaction, typically in the presence of ammonia, to reduce or remove nitric oxides from exhaust emissions.
1. An iron-containing aluminosilicate zeolite, wherein the structure of said zeolite has both framework iron and iron cations on the ion-exchange sites, wherein said zeolite exhibits a selective catalytic reduction of nitrogen oxides with NH 3 or urea of greater than 40% conversion at 250-300°C. in exhaust gases prior to aging or exposure to steam, and wherein said zeolite has a silica-to-alumina ratio (SAR) of less than 60, and is chosen from Beta and chabazite type zeolites.
2. The iron-containing aluminosilicate zeolite of claim 1 , wherein said iron comprises at least 1% by weight of said zeolite.
3. The iron-containing aluminosilicate zeolite of claim 2 , wherein said iron is present in an amount ranging from 1 to 5% by weight of said zeolite.
4. The iron-containing aluminosilicate zeolite of claim 1 , wherein said SAR ranges from 5 to 50.
5. The iron-containing aluminosilicate zeolite of claim 1 , further comprises at least one additional metal cation on the ion-exchange sites.
6. The iron-containing aluminosilicate zeolite of claim 5 , wherein said at least additional metal is chosen from copper, manganese, cobalt, and silver.
7. The iron-containing aluminosilicate zeolite of claim 1 , wherein said zeolite has both framework iron and iron cations on the ion-exchange sites, wherein said zeolite exhibits a selective catalytic reduction of nitrogen oxides with NH 3 or urea of greater than 80% conversion at temperatures ranging from 300° C. to 500° C. in exhaust gases after hydrothermal aging or exposure to steam.
8. A direct synthesis method of making an iron-containing aluminosilicate zeolite, said method comprising:
mixing a source of alumina, a source of silica, optionally a structural directing agent, (SDA) and with an iron constituent to form an iron containing synthesis mixture; and
performing at least one heating step on said iron containing synthesis mixture to form an iron-containing aluminosilicate zeolite wherein the structure of said zeolite has both framework iron and iron cations on the ion-exchange sites, wherein said zeolite exhibits a selective catalytic reduction of nitrogen oxides with NH 3 or greater than 40% conversion at 250-300°C. in exhaust gases prior to aging or exposer to steam, wherein said iron-containing aluminosilicate zeolite has a silia to alumina ratio (SAR) of less than 60, and is chosen from Beta and chabazite type zeolites.
9. The method of claim 8 , wherein said iron comprises at least 1% by weight of said zeolite.
10. The method of claim 9 , wherein said iron is present in an amount ranging from 1 to 5% by weight of said zeolite.
11. The method of claim 8 , wherein said SAR ranges from 5 to 50.
12. The method of claim 8 , further comprising adding zeolite crystallization seeds to said iron containing synthesis mixture prior to said heating step.
13. The method of claim 8 , wherein said source of silica is chosen from silica sol, sodium silicate, sodium metalsilicate, precipitated silica, silica gel, and silica-alumina.
14. The method of claim 8 , wherein said source of alumina is chosen from sodium aluminate, aluminum nitrate, aluminum hydroxide, alumina, and aluminum sulfate.
15. The method of claim 8 , wherein said source of iron is an iron salt.
16. The method of claim 15 , wherein said iron salt is chosen from ferric nitrate, ferric chloride, ferrous chloride, and ferrous sulfate.
17. The method of claim 8 , wherein said at least one heating step is performed in an autoclave at a temperature ranging from 90° C. to 250° C.
18. The method of claim 8 , further comprising hydrothermal aging said product by exposing it to steam above 500° C.
19. The method of claim 8 , further comprising calcining said product up to 600° C. to produce a calcined product.
20. The method of claim 19 , wherein said calcined product is further subject to an ion-exchange and/or impregnation step to add more iron and/or at least one additional metal.
21. The method of claim 20 , wherein said at least additional metal is chosen from copper, manganese, cobalt, and silver.
22. A monolith comprising an iron-containing aluminosilicate zeolite of claim 1 .
23. A diesel particulate filter comprising an iron-containing aluminosilicate zeolite of claim 1 .