Catalytic washcoat with added alumina for NOx abatement
The present disclosure provides catalyst compositions for NOx conversion and catalytic articles incorporating such catalyst compositions. Certain catalyst compositions include a zeolite with a silica-to-alumina ratio from 5 to 20 and sufficient Cu exchanged into cation sites of the zeolite such that the zeolite has a Cu/Al ratio of 0.1 to 0.5 and a CuO loading of 1 to 15 wt. %; and a copper trapping component in a concentration in the range of 1 to 20 wt. %, the copper trapping component including a plurality of particles having a particle size of about 0.5 to 20 microns. Certain catalyst compositions include, as the copper trapping component, alumina present as a plurality of alumina particles with a D 90 particle size distribution in the range of 0.5 microns to 20 microns.
1. A catalyst article comprising:
a flow-through honeycomb substrate; and
a catalyst composition coated on the substrate,
wherein the catalyst composition comprises:
a zeolite with a silica-to-alumina ratio (SAR) ranging from 5 to 20 and sufficient copper (Cu) exchanged into cation sites of the zeolite such that the zeolite has a Cu/Al ratio of 0.1 to 0.5 and a CuO loading ranging from 1 wt. % to 15 wt. %; and
a copper trapping component present in the catalyst composition in a concentration ranging from 1 wt. % to 20 wt. %, and
wherein the copper trapping component comprises a plurality of particles having a particle size of about 0.5 microns to about 20 microns, wherein the copper trapping component comprises non-dispersible alumina having an agglomerate size of D 10 >0.1 microns.
2. The catalyst article of claim 1 , wherein the copper trapping component comprises a material chosen from alumina, silica, zirconia, niobia, molybdenia, and combinations thereof.
3. The catalyst article of claim 2 , wherein the zeolite and the non-dispersible alumina are contained within a first washcoat.
4. The catalyst article of claim 3 , further comprising one or more additional washcoats, and wherein the one or more additional washcoats comprise different catalyst compositions.
5. The catalyst article of claim 1 , wherein the zeolite has a particle size ranging from about 0.01 microns to about 5 microns.
6. The catalyst article of claim 1 , wherein the zeolite has a surface area ranging from about 200 m 2 /g to about 800 m 2 /g.
7. The catalyst article of claim 1 , wherein the zeolite has an “8-ring” framework structure chosen from AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC, UFI, and combinations and intergrowths thereof.
8. The catalyst article of claim 1 , wherein the zeolite has a “10-ring” framework structure chosen from AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR, SZR, TER, TON, TUN, UOS, VSV, WEI, WEN, and combinations and intergrowths thereof.
9. The catalyst article of claim 1 , wherein the zeolite has a “12-ring” framework structure chosen from AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, VET, and combinations and intergrowths thereof.
10. The catalyst article of claim 1 , wherein the zeolite further comprises a transition metal chosen from iron (Fe) and manganese (Mn), and combinations thereof.
11. The catalyst article of claim 1 , wherein the zeolite is Cu-CHA.
12. The catalyst article of claim 1 , wherein the non-dispersible alumina is chosen from boehmite, gamma-alumina, silica-alumina, stabilized alumina, and combinations thereof.
13. The catalyst article of claim 1 , wherein the non-dispersible alumina has a D90 agglomerate particle size ranging from about 0.5 microns to about 20 microns.
14. The catalyst article of claim 1 , wherein the non-dispersible alumina is present in an amount of about 2 wt. % to about 20 wt. % based on the total amount of zeolite.
15. The catalyst article of claim 1 , wherein the zeolite is present in an amount ranging from about 1.0 g/in 3 to about 5.0 g/in 3 .
16. The catalyst article of claim 1 , wherein the catalyst composition further comprises zirconium oxide in an amount ranging from about 2 wt. % to about 20 wt. % based on the total amount of zeolite.
17. The catalyst article of claim 1 , wherein the catalyst composition comprises a first washcoat comprising the zeolite and a second washcoat comprising the non-dispersible alumina.
18. The catalyst article of claim 17 , wherein the second washcoat is disposed directly on the substrate and the first washcoat is disposed on the second washcoat.
19. The catalyst article of claim 18 , wherein a first portion of the second washcoat is located within walls of the substrate and a second portion of the second washcoat is located on the walls of the substrate, or wherein the second washcoat is located within the walls of the substrate.
20. The catalyst article of claim 19 , wherein the first washcoat is located on the walls of the substrate.
21. The catalyst article of claim 19 , wherein the second washcoat is located on walls of the substrate.
22. The catalyst article of claim 17 , wherein the first washcoat is disposed on the substrate and the second washcoat is disposed on the first washcoat.
23. The catalyst article of claim 22 , wherein a first portion of the first washcoat is located within walls of the substrate and a second portion of the first washcoat is located on the walls of the substrate, or wherein the first washcoat is located within the walls of the substrate.
24. The catalyst article of claim 23 , wherein the second washcoat is located on the walls of the substrate.
25. The catalyst article of claim 22 , wherein the first washcoat is located on the walls of the substrate.
26. The catalyst article of claim 17 , wherein the first and second washcoat layers are in a laterally zoned configuration with respect to one another.
27. The catalyst article of claim 26 , wherein the first washcoat layer extends from one end of the substrate to a length up to about 90% of the substrate length and the second washcoat layer extends from an opposing end of the substrate to a length up to about 90% of the substrate length.
28. An exhaust gas treatment system, comprising the catalyst article of claim 1 downstream of a urea injector and in fluid communication with an internal combustion engine.
29. The exhaust gas treatment system of claim 28 , further comprising a component chosen from a diesel oxidation catalyst, a soot filter, an ammonia oxidation catalyst, a lean NOx trap, and any combination thereof.
30. A catalyst article comprising:
a flow-through honeycomb substrate; and
a catalyst composition coated on the substrate,
wherein the catalyst composition comprises:
a zeolite with a silica-to-alumina ratio (SAR) from 5 to 20 and sufficient copper (Cu) exchanged into cation sites of the zeolite such that the zeolite has a Cu/Al ratio of 0.1 to 0.5 and a CuO loading ranging from 1 wt. % to 15 wt. %; and
alumina present as a plurality of non-dispersible alumina particles with a D90 particle size distribution ranging from 0.5 microns to 20 microns and with an agglomerate size of D 10 >0.1 microns, and
wherein the alumina is present in an effective amount to obtain a NOx conversion by the catalyst article, after aging at 800° C. for 16 hours under 10% H 2 O, of at least 90% at a space velocity of 80,000 h −1 over a temperature range of at least 200° C.
31. The catalyst article of claim 30 , wherein the catalyst article has a zeolite surface area (ZSA) that decreases by less than 35% after the aging.
32. The catalyst article of claim 30 , wherein after aging the catalyst article at 800° C. for 16 hours under 10% H2O, the catalyst article has a NOx conversion rate in the temperature range of about 150° C. to about 650° C. that is about 5% to about 30% higher than the NOx conversion rate of a catalyst article that is aged under the same conditions and that has an otherwise identical composition except that it does not comprise the alumina particles.
33. The catalyst article of claim 32 , wherein the about 5% to about 30% higher NOx conversion rate occurs in the temperature range of about 350° C. to about 650° C.