Direct synthesis of metal-containing CHA zeolites
A metal-containing chabazite zeolite, which has an FTIR peak area ratio between the peak at 900-1300 cm −1 (Si—O—Si asymmetric stretch) and the peak at 765-845 cm −1 (˜805 cm −1 is Si—O—Si symmetric stretch) of at least 55. A method for preparing metal-containing CHA zeolites with high SCR activity at low reaction temperatures from alkali cation-free reaction mixtures that contain the three OSDA structures: metal-polyamine, N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) and TMAOH. The metal-containing CHA zeolites produced by the disclosed method can be identified by XRD, FTIR spectroscopy, FT-VIS spectroscopy, and scanning electron microscopy. A method of selective catalytic reduction of NOx in exhaust gas using the material described herein is also disclosed.
1. A metal-containing chabazite zeolite, wherein said zeolite has an FTIR peak area ratio between the peak at 900-1300 cm-1 and the peak at 765-845 cm-1 (˜805 cm-1 is Si—O—Si symmetric stretch) of at least 55.
2. The zeolite of claim 1 , wherein said zeolite has a silica-to-alumina ratio (SAR) ranging from 5 to 60.
3. The zeolite of claim 1 , wherein the metal is copper.
4. The zeolite of claim 3 , wherein the copper is present in an amount of at least 0.5 weight percent of the total weight of the material.
5. The zeolite of claim 4 , wherein the copper comprises an amount ranging from 0.5 to 10 weight percent of the total weight of the material.
6. The zeolite of claim 1 , wherein the metal is iron.
7. The zeolite of claim 6 , wherein the iron is present in an amount of at least 0.5 weight percent of the total weight of the material.
8. The zeolite of claim 7 , wherein the iron comprises an amount ranging from 0.5 to 10 weight percent of the total weight of the material.
9. The zeolite of claim 1 , wherein the zeolite has a total alkali oxide amount of less than 0.3 weight percent.
10. The zeolite of claim 1 , wherein the peak area ratio between the FT-VIS peak between 500-1100 nm and the FT-VIS peak area of Cu(OH)2 between 500-1100 nm is lower than 2.5.
11. A method of selective catalytic reduction (SCR) of NOx in exhaust gas, said method comprising contacting exhaust gas with a zeolitic material comprising a copper containing CHA-type zeolite, wherein said material has an FTIR peak area ratio between the peak at 900-1300 cm-1 and the peak at 765-845 cm-1 (˜805 cm-1 is Si—O—Si symmetric stretch) of at least 55.
12. The method of claim 11 , wherein said contacting step is performed in the presence of ammonia or urea.
13. A method of making a microporous crystalline material from reaction mixtures that are essentially void of alkali metal cations and comprise organic structure directing agents (OSDA) selected from the group consisting of (1) metal-polyamine as the first OSDA, (2) N,N,N-trimethyl-1-adamantyl ammonium (TMAda+), or trimethylbenzylammonium (TMBA+) or N,N,N-dimethylethylcyclohexylammonium (DMECHA+) organic or mixtures thereof as the second OSDA, and (3) TMA+ or TEA+ or mixtures thereof as the third OSDA, the method comprising:
a) mixing sources of alumina, silica, water, a first OSDA, a second OSDA and optionally a third OSDA and optionally a seed material to form a gel;
b) heating the gel in a vessel at a temperature ranging from 80° C. to 250° C. to form a crystalline chabazite product that exhibits an XRD peak area ratio between the [3,1,0] peak and the peak doublet (sum of [3,−1,−1] peak and [3,1,0] peak) of at least 0.15; and
c) calcining the product to produce an aluminosilicate zeolite having a CHA structure, and a silica-to-alumina ratio (SAR) ranging from 5 to 60.
14. The method of claim 13 , wherein the reaction mixture has a molar composition of 1 SiO2:m Al2O3:n metal-polyamine:x TMAdaOH:y TMAOH:z H2O, where m=0.016-0.2, n=0.01-0.12, x=0.01-0.50, y=0.01-0.50, z=1-50.
15. The method of claim 13 , wherein the metals used for forming metal-polyamine of the first OSDA are selected from Cu, Fe, Mn, Co, Ni, Pd, Pt and Zn.
16. The method of claim 13 , wherein the polyamine of the first OSDA is selected from diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N, N-(2-hydroxyethyl) ethylenediamine, N,N-bis(2-aminoethyl)-1,3-propanediamine, 1,2-bis(3-aminopropylamino), 1,4,8,11-tetraazacyclotetradecane, 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, and combinations thereof.
17. The method of claim 16 , wherein the polyamine is tetraethylenepentamine (TEPA).
18. The method of claim 13 , wherein the source of alumina is chosen from aluminum trihydroxide, alumina, pseudoboehmite alumina, silica-alumina and Al isopropoxide.
19. The method of claim 13 , wherein the source of silica is chosen from silica sol, silica gel, precipitated silica, silica-alumina and fumed silica.