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EP-4735153-A1 - SCR CATALYSTS FOR IMPROVED NOx REDUCTION

EP4735153A1EP 4735153 A1EP4735153 A1EP 4735153A1EP-4735153-A1

Abstract

The present invention discloses catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines, comprising a carrier substrate of length L, a bottom layer comprising a zone D extending from a second side over a length L Z and comprising a first SCR composition consisting of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites; and a zone C' extending from a first side over a length L Y = L - L Z and comprising a third SCR composition consisting of a V/TiO 2 SCR catalyst composition which comprises at least one oxide of vanadium, and a top layer comprising a material zone C extending over the carrier substrate and comprising a second SCR composition consisting of a V/TiO 2 SCR catalyst composition which comprises at least one oxide of vanadium.

Inventors

  • WEN, Fei
  • HOYER, RUEDIGER
  • SIST, Mattia
  • VAN TENDELOO, Leen

Assignees

  • Umicore AG & Co. KG

Dates

Publication Date
20260506
Application Date
20240619

Claims (20)

  1. 1. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines, comprising a) a carrier substrate of length L, said length L extending from a face side A to a face side B, and b) a bottom layer comprising - a material zone D affixed to the carrier substrate; said material zone D comprising a first SCR catalytically active composition and extending from face side B over a length L z which is 20 to 100% of the length L of the carrier substrate; wherein - the first SCR catalytically active composition in said material zone D consist of one or more manganese-containing mixed oxides, or a mixture of one or more manganese-containing mixed oxides and one or more metal-promoted small-pore zeolites - a material zone C’ affixed to the carrier substrate; said material zone C’ comprising a third SCR catalytically active composition and extending from face side A over a length L y = L - L z which is 80 to 0% of the total length of the carrier substrate; wherein the third SCR catalytically active composition in said material zone C’ consists of a V/TiC>2 SCR catalyst composition which comprises at least one oxide of vanadium supported on titanium dioxide; - wherein L y + L z = L, and c) a top layer affixed to the bottom layer, said top layer comprising a material zone C comprising a second SCR catalytically active composition and extending from face side A to face side B of the carrier substrate; wherein the second SCR catalytically active composition in said material zone C consists of a V/TiC>2 SCR catalyst composition which comprises at least one oxide of vanadium supported on titanium dioxide, and wherein the second and the third SCR catalytically active composition are identical or different from one another.
  2. 2. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 1 , wherein the carrier substrate is a honeycomb flow-through substrate, a wall-flow filter or a corrugated substrate.
  3. 3. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 1 or 2, wherein Lz is 30 to 100% of length L.
  4. 4. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 3, wherein the first SCR catalytically active composition consists of one or more manganese- containing mixed oxides, wherein the one or more manganese-containing mixed oxides are selected from a) Mn a CebTi c Ox, wherein a, b and c are, independently from one another, larger than zero and smaller than 1 , and wherein a , b and c add up to 1 , and wherein x is the molar amount of oxygen, a ranges from 0.05 to 0.50; b ranges from 0.05 to 0.50; c ranges from 0.30 to 0.90 and x ranges from 1.5 to 2.0; and b) MndMei-dOw, wherein d, 1-d and w represent the molar fractions of manganese, a metal Me and oxygen, and wherein Me is selected from the group consisting of Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti, Al, Si and Y, and wherein d ranges from 0.02 to 0.98 and w ranges from 1.0 to 2.5; and c) Mn e CefMei- e .fO v , wherein e, f, 1-e-f and v represent the molar fractions of manganese, cerium, a metal Me and oxygen, and wherein Me is selected from the group consisting of Fe, Co, Ni, Cu, Zr, Nb, Mo, W, Ag, Sn, Ce, Pr, La, Nd, Ti, Al, Si and Y, and wherein e ranges from 0.02 to 0.98, f ranges from 0.02 to 0.98, and v ranges from 1.0 to 2.5; and d) spinels having the general formula MnS2C>4 or SM^CL, wherein S is selected from Fe, Al, Cr, Co and Cu.
  5. 5. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 3, wherein the first SCR catalytically active composition in material zone D consists of a mixture of one or more manganese-containing mixed oxides according to claim 4 and one or more metal-promoted small-pore zeolites.
  6. 6. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 5, wherein the one or more small-pore zeolites are selected from ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, BIK, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, ESV, ETL, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG, ZON and mixtures and intergrowths thereof.
  7. 7. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 5 or 6, wherein the at least one small-pore zeolite has a molar ratio of silica-to-alumina (SAR) value of 5 to 50.
  8. 8. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claim 5 to claim 7, wherein the small-pore zeolite is promoted with copper and optionally with one or two additional metals M1 and M2, and wherein the copper to aluminum atomic ratio is between 0.12 and 0.55, and the copper content is between 2.0 and 6.5wt.- %, calculated as CuO and based on the total weight of the zeolite, and wherein the promoter metals M1 and M2 are, independently from one another, selected from magnesium, calcium, barium, strontium, yttrium, titanium, zirconium, niobium, manganese, iron, zinc, silver, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, provided that, if both M1 and M2 are present, they are different from one another.
  9. 9. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 8, wherein copper is the only promoter metal, and the Cu:AI atomic ratio is between 0.12 and 0.55.
  10. 10. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 8, wherein only one promoter metal M1 is present in addition to copper, the M1 :Cu atomic ratio is in the range of 0.05 to 0.95, and the (Cu + M1) : Al atomic ratio is in the range of 0.11 to 0.96.
  11. 11. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to claim 8, wherein two promoter metals M1 and M2 are present in addition to copper, the M1 :Cu ratio and the M2:Cu atomic ratio are both in the range of 0.05 to 0.95, and the (Cu + M1 + M2) : Al atomic ratio is in the range of 0.2 to 0.80, under the proviso that M1 and M2 are different from one another.
  12. 12. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 5, wherein the weight ratio of at least one manganese-containing mixed oxide to the at least one metal-promoted small-pore zeolite is in the range of 0.1 to 99 wt.%.
  13. 13. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 10, wherein the V/TiCh catalyst compositions in material zones C and C’ comprise, independently from one another, - at least one oxide of vanadium in an amount of 1 to 10 wt.-%, and - at least one oxide of tungsten in an amount of 0 to 15 wt.-%, and, - at least one oxide of silicon in an amount of 0 to 18 wt.-%, and - at least one oxide of molybdenum, antimony, niobium, zirconium, tantalum, hafnium, cerium in a total amount of these oxides of 0 to 20 wt.-%, and - at least one oxide of titanium in an amount that is measured so as to result in a total of 100 wt.-%, in each case based on the total weight of the V/TiCh catalyst and calculated as V2O5, WO3, SiC>2, MO2O3, Sb2Os, Nb2Os, ZrC>2, Ta 2 C>5, HfC>2, CeC>2 or TiC>2.
  14. 14. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 7, wherein material zone C is affixed to the bottom layer and, if present, material zone C’ is affixed to the carrier in the form of washcoats, wherein the washcoat loadings are, independently from one another, in the range of from 25 to 400 g/L.
  15. 15. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 8, wherein material zone D is affixed to the bottom layer in the form of a washcoat, wherein the washcoat loading is in the range of from 50 to 300 g/L.
  16. 16. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 1 to 9, wherein the total washcoat loading of material zones C, D and optionally C’ is in the range of from 75 to 450 g/L.
  17. 17. Catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to any one of claims 8 to 10, wherein the washcoats, independently from one another, contain binders selected from TiC>2, SiC>2, AI2O3, ZrC>2, CeC>2 and combinations thereof in an amount of 0 to 20 wt.-%, based on the total weight of the SCR catalytically active composition and the binder.
  18. 18. An emissions treatment system for the removal of NO X emissions from exhaust gases of internal combustion engines, and optionally also for the removal of particulate matter, the system comprising, in the following order, from upstream to downstream: a) means for injecting ammonia or an ammonia precursor solution into the exhaust gas stream, b) a catalytic device for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines according to anyone of claims 1 to 17 the present invention, wherein the carrier substrate is selected from honeycomb flow-through substrates, honeycomb wall-flow filters, corrugated substrates, wound or packed fiber filters, open cell foams, sintered metal filters and extruded catalysed carrier substrates.
  19. 19. The emissions treatment system according to claim 18, wherein said emissions treatment system is arranged in a close-coupled position.
  20. 20. The emissions treatment system according to claim 18, wherein said emissions treatment system is arranged in an underfloor position.

Description

SCR catalysts for improved NOX reduction Description The present invention relates to catalytic devices for the selective catalytic reduction of nitrogen oxides from the exhaust gas of combustion engines. The catalytic devices comprise a carrier substrate, a bottom layer and a top layer. The bottom layer comprises a material zone comprising an SCR catalytically active composition consisting of one or more manganese-containing mixed oxides or a mixture of one or more manganese-con- taining mixed oxides and one or more metal-promoted small-pore zeolites. The material zone in the bottom layer, which comprises said SCR catalytically active composition, extends from the downstream end over 20 to 100% of the length of the carrier substrate. Optionally, the bottom layer additionally comprises a material zone which extends from the upstream end over 80 to 0% of the carrier substrate; said additional material zone comprising a vanadia-titania based SCR catalyst composition. The bottom layer is directly affixed to the carrier substrate. The top layer is affixed to the bottom layer and extends over the total length of the carrier substrate. It comprises a vanadia-titania based SCR catalyst composition. Methods for making the catalytic devices as well as uses thereof are also envisaged. Modern internal combustion engines require the use of catalytic aftertreatment systems to reduce harmful emissions and respect the new legislation standards. The exhaust gas of combustion processes, in particular that of diesel engines, but also that of direct-injection lean-mixture-operated gasoline engines, contains carbon monoxide (CO) and hydrocarbons (HC) resulting from incomplete combustion of the fuel. In addition, the exhaust gas also contains particulate matter (PM) and nitrogen oxides (NOX). Furthermore, the exhaust gas of diesel engines contains, for example, up to 15 vol.-% oxygen. It is known that the oxidizable harmful gases CO and HC can be converted to harmless carbon dioxide (CO2) and water (H2O) by passing them over suitable oxidation catalytic converters and that particulates can be removed by passing the exhaust gas through a suitable particulate filter. Nitrogen oxides may be converted on an SCR catalyst in the presence of oxygen to nitrogen and water by means of ammonia. “SCR” stands for “selective catalytic reduction”. A major driver for the recent and future development of catalysts are the increasingly stringent world-wide legislative emission levels for road (e.g. passenger cars, trucks) and non-road (e.g. ships, trains) applications. In the specific case of removing nitrogen oxides from the exhaust gas of lean burn engines, there is a global need for more active, more selective and more stable catalysts, due to tightened legislative emission levels and the increased need of catalysts which show a good denitration performance even at low exhaust gas temperatures. One effective method to remove nitrogen oxides (NOX) from the exhaust gas of these lean burn engines is selective catalytic reduction (SCR) with ammonia (NH3). In NH3-SCR, the NOX molecules are catalytically reduced to N2 using NH3 as reducing agent. The ammonia used as reducing agent may be made available by feeding an ammonia precursor compound into the exhaust gas which is thermolyzed and hydrolyzed to form ammonia. Alternatively, the ammonia may be formed from an ammonia precursor compound by catalytic reactions within the exhaust gas. Examples of such precursor compounds are ammonium carbamate, ammonium formate and preferably urea. In most cases, ammonia is fed as a less hazardous urea solution, which is decomposed to ammonia in the catalytic unit, and can be filled and stored in the vehicle in a dedicated reservoir. The catalytic reduction of NOX with NH3 can be represented by different reaction equations. Nitric oxide (NO) is the main NOX compound produced in an engine. The reduction of NO is referred to as the “standard” NH3-SCR reaction: NO2 is more reactive than NO. In presence of mixtures of NO and NO2, the NH3-SCR reaction is easier, and the so-called “fast” NH3-SCR reaction can occur: To take profit of the fast NH3-SCR reaction, an additional catalyst is needed to oxidize part of the NO into NO2. Also, side reactions may occur and result in unwanted products or the unproductive consumption of ammonia: 4NH3 + 3O2 N2 + 6 H20 (3) In official driving cycles, exhaust gas temperatures of latest generation engines and hybrid vehicles with reduced fuel consumption and low CO2 emission are significantly lower than with previous engine generations. Therefore, it is necessary to obtain a NH3-SCR catalyst which shows a high low-temperature NOX conversion. Furthermore, NH3-SCR catalyst should release as little N2O as possible. SCR catalysts are described extensively in literature as well. They are generally either so-called mixed oxide catalysts, or so-called zeolite catalysts. Mixed oxide catalysts either comprise oxides of vanadium and titanium and