RU2790665C2 - Ammonia slip catalytic neutralizer with pt in situ attachment - Google Patents

Abstract

FIELD: catalytic neutralizer.

SUBSTANCE: invention relates to a catalytic product for exhaust gas purification, an exhaust system, methods for improving the conversion of NH₃ in exhaust gas at a temperature of about 300°C or lower and the exhaust gas purification method. The catalytic product contains a substrate having an inlet end and an outlet end; a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalytic neutralizer; and a second coating comprising a second SCR catalytic neutralizer; moreover, the carrier contains at least one of zeolite or mixed oxide SiO₂-Al₂O₃; moreover, SiO₂ is present in an amount of from about 1 wt. % to about 70 wt. % mixed oxide, while the platinum is fixed on the carrier in a solution containing the first SCR catalytic neutralizer. The exhaust system comprises a catalytic product and means for introducing a reducing agent upstream of the catalytic product. Methods for improving the conversion of NH₃ in the exhaust gas at a temperature of about 300° C or lower, which includes contacting an exhaust gas containing ammonia with a catalyst product. A method for purification of an exhaust gas containing ammonia and NOx, the method comprising contacting an exhaust gas containing ammonia with a catalyst product.

EFFECT: catalytic products of the present invention provide improved catalytic activity and selectivity.

43 cl, 9 dwg, 1 tbl, 1 ex

Description

Prerequisites for the creation of the invention

The combustion of hydrocarbons in diesel engines, stationary gas turbines and other systems generates exhaust gases that must be treated to remove oxides of nitrogen (NOx), which contain NO (nitrogen oxide) and NO2 (nitrogen dioxide), NO being the majority of the NOx generated. NOx is known to cause a number of health problems in humans, as well as a number of environmental impacts, including the formation of smog and acid rain. To reduce the impact of NOx in the exhaust gas on human health and the environment, it is desirable to eliminate these undesirable components, preferably by a process that does not lead to the formation of other harmful or toxic substances.

The exhaust gases generated in lean-burn and diesel engines are predominantly oxidative. The NOx content must be selectively reduced using a catalytic converter and a reducing agent in a process known as selective catalytic reduction (SCR), which converts NOx to elemental nitrogen (N ₂ ) and water. In the SCR process, a gaseous reducing agent, typically anhydrous ammonia, aqueous ammonia, or urea, is added to the exhaust gas stream before the exhaust gas is brought into contact with the catalyst. The reducing agent is taken up by the catalytic converter and NO _x is reduced as the gases pass through or over the catalyzed carrier. To maximize NOx conversion, it is often necessary to add more than a stoichiometric amount of ammonia to the gas stream. However, the release of excess ammonia into the atmosphere is harmful to human health and the environment. In addition, ammonia is corrosive, especially in its aqueous form. Condensation of ammonia and water in areas of the exhaust line downstream of the catalytic converters can create a corrosive mixture that can damage the exhaust system. Therefore, the emission of ammonia from the exhaust gas must be avoided. In many conventional exhaust systems, an ammonia oxidation catalyst (also known as an ammonia slip catalyst; ASC) is placed downstream of the SCR catalyst to remove ammonia from the exhaust gas by converting it to nitrogen. The use of ammonia slip catalytic converters provides over 90% NO _x conversions compared to a typical diesel fuel test cycle.

It would be desirable to have a catalytic converter that provides both SCR NOx removal and selective conversion of ammonia to nitrogen, whereby ammonia conversion occurs over a wide range of temperatures during the vehicle test cycle and minimal by-products of nitrogen oxides and oxides of nitrogen are generated. .

Statement of the Invention

According to some embodiments of the present invention, the catalytic article may comprise: a support having an inlet end and an outlet end; a first coating containing a mixture of: (1) supported platinum and (2) a first SCR catalyst; and a second coating comprising a second SCR catalyst; and the carrier contains at least one of zeolite or mixed oxide SiO ₂ -AlO ₃ . In some embodiments, the implementation of the platinum is fixed on the media in solution. In some embodiments, the first SCR catalyst is a Cu-SCR catalyst or a Fe-SCR catalyst.

In some embodiments, the carrier comprises a mixed oxide of SiO ₂ -AlO ₃ . In some embodiments, the implementation of SiO ₂ is present in an amount of from about 1 wt.% to about 70 wt.% or from about 40 wt.% to about 70 wt.% mixed oxide.

In some embodiments, the carrier comprises a zeolite. The outer surface area of a suitable zeolite may be at least 50 m ² /g; at least 70 m ² /g; or at least 100 m ² /g. In some embodiments, the average crystal size of a suitable zeolite is less than about 1 micron; less than about 0.5 microns; or less than about 0.3 µm. In some embodiments, the ratio of silica to alumina in a suitable zeolite is greater than 100; more than 300; or greater than 1000. In some embodiments, the zeolite is selected from the group of frame structure types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, 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, BEA, MFI and FER, as well as mixtures and/or splices thereof. In some embodiments, the zeolite is selected from the group of frame structure types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, BEA, MFI, and FER.

In some embodiments, the implementation of the second coating completely overlaps the first coating. In some embodiments, the implementation of the second coating partially overlaps the first coating. In some embodiments, the second coating extends from the inlet end to the outlet end, covering less than the entire length of the substrate. In some embodiments, the first coating extends from the outlet end to the inlet end, covering less than the entire length of the substrate. In some embodiments, the implementation of the second SCR catalyst is located on the inlet side of the coating containing a mixture of platinum on the media with the first SCR catalyst. In some embodiments, a second SCR catalyst is located on the downstream side of a coating containing a mixture of supported platinum with a first SCR catalyst.

In some embodiments, the platinum is present in an amount of at least one of the following: (a) 0.01-0.3% by weight; (b) 0.03–0.2 wt%; (c) 0.05–0.17 wt%; and (d) 0.07 to 0.15 wt% inclusive, based on the weight of the platinum support + the weight of platinum + the weight of the first SCR catalyst in the mixture. The mass ratio of the first SCR catalyst to supported platinum may be in the range of at least one of the following values: (a) 0:1 to 300:1, (b) 3:1 to 300:1, (c) from 7:1 to 100:1; and (d) from 10:1 to 50:1 inclusive, based on the weight of these components.

In some embodiments, the mixture further comprises at least one of palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), or rhodium (Rh).

In some embodiments, the second SCR catalyst is a base metal, a base metal oxide, a molecular sieve, a metal-substituted molecular sieve, a mixed oxide, or a mixture thereof. The base metal may be selected from the group consisting of vanadium (V), molybdenum (Mo) and tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu), as well as their mixtures. Such a second SCR catalyst may further comprise at least one base metal promoter.

In the case where the second SCR catalyst is a molecular sieve or metal substituted molecular sieve, the molecular sieve or metal substituted molecular sieve may be narrow pore, medium pore, large pore, or a mixture thereof. In some embodiments, the second SCR catalyst comprises a molecular sieve selected from the group consisting of aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminophosphate (MeAlPO) molecular sieves, silicoaluminophosphate (SAPO) molecular sieves, and metal-substituted silicoaluminophosphate (MeAPSO) molecular sieves, as well as mixtures thereof. In some embodiments, the second SCR catalyst comprises a narrow pore molecular sieve selected from the group of framework structure types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON, as well as mixtures and/or splices thereof. In some embodiments, the second SCR catalyst comprises a narrow pore molecular sieve selected from the group of framework structure types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, and ITE. In some embodiments, the second SCR catalyst comprises a medium pore molecular sieve selected from the group of framework structure types consisting of 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 and WEN, as well as mixtures and/or splices thereof. In some embodiments, the second SCR catalyst comprises a coarse molecular sieve selected from the group of frame structure types consisting of 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 and VET, and mixtures thereof and/or splices. In some embodiments, the implementation of the second catalyst SCR contains promoted Ce-Zr or promoted MnO ₂ .

A suitable substrate may comprise cordierite, high porosity cordierite, a metal substrate, extruded SCR, filter or SCRF.

In accordance with some embodiments of the present invention, the exhaust system comprises the catalyst article described herein and means for introducing a reductant upstream of the catalyst article. The exhaust system may further comprise a third SCR catalyst providing ≤100% NOx conversion, wherein the third SCR catalyst is a Cu-zeolite SCR catalyst and is located in the exhaust stream upstream of the catalyst article described herein.

In accordance with some embodiments of the present invention, a method for improving the conversion of NH ₃ in exhaust gas at a temperature of about 300 °C or below includes contacting an exhaust gas containing ammonia with the catalyst article described herein.

In accordance with some embodiments of the present invention, a method for improving the conversion of NH ₃ in an exhaust gas at a temperature of about 300 °C or below includes contacting an exhaust gas containing ammonia with a catalyst article described herein that contains platinum supported on a carrier in solution. In some embodiments, the NH ₃ conversion is greater, in the range of about 30% to about 100%, as compared to a comparable composition catalyst in which the platinum is pre-mounted on a support.

In accordance with some embodiments of the present invention, a method for treating an exhaust gas containing ammonia and NOx comprises contacting an exhaust gas containing ammonia with a catalyst article described herein. In some embodiments, the mass ratio of ammonia to NOx in the exhaust gas is >1.0 for at least part of the time the system is running.

Brief description of graphic materials

In FIG. 1-8 are schematic representations of configurations of catalysts containing a mixture of (1) supported platinum and (2) a first SCR catalyst. the portion of the catalyst containing the mixture of (1) supported platinum and (2) the first SCR catalyst is referred to as "mixture" in these figures.

In FIG. 1 shows a configuration in which a second SCR catalyst is located in the exhaust gas stream on top of the mixture, with the second SCR catalyst covering the entire mixture.

In FIG. 2 shows a configuration in which a second SCR catalyst is located in the exhaust gas stream ahead of the mixture, with the second SCR catalyst covering the entire mixture.

In FIG. 3 shows a configuration in which a second SCR catalyst is located in the exhaust gas stream ahead of the mixture, with the second SCR catalyst covering a portion of the mixture rather than the entire mixture.

In FIG. 4 shows a configuration in which the second SCR is located in the exhaust gas stream before the mixture and does not cover the mixture.

In FIG. 5 shows a configuration in which the second SCR catalytic converter covers the entire mixture, with a portion of the second SCR catalyst located in the exhaust gas stream behind the mixture.

In FIG. 6 shows a configuration in which the second SCR catalytic converter covers a portion of the mixture rather than the entire mixture, with a portion of the second SCR catalyst located in the exhaust gas stream behind the mixture.

In FIG. 7 shows a configuration in which the third SCR catalyst is the bottom layer on the substrate, the second layer contains the mixture partially covering the third SCR catalyst, and the third layer contains the second SCR catalyst located on top of and covering the entire mixture layer.

In FIG. 8 shows a configuration in which a third SCR catalyst is a bottom layer on a substrate, where the second layer contains a mixture partially but not completely covering the third SCR catalyst, where the third layer contains a second SCR catalyst located on top of the mixture layer and partially , but not completely covering the layer of the mixture.

In FIG. 9 shows the generation of NH ₃ , N ₂ O and NOx breakthrough when various ASCs are exposed to a one minute 1000 ppm NH ₃ pulse.

Detailed description of the invention

The catalysts of the present invention relate to ammonia slip catalysts which can provide improved NH ₃ conversion at lower temperatures and which can be produced in a more economical manner. Catalyst articles in accordance with embodiments of the present invention comprise a substrate with a first coating containing a mixture of: (1) platinum on a carrier and (2) a first SCR catalyst, wherein the carrier comprises zeolite and/or mixed oxide SiO ₂ -Al ₂ O ₃ . The catalytic articles also contain a second coating containing an SCR catalyst. In some embodiments, the platinum is mounted on the carrier in solution, i.e. in situ. Catalytic converters and specific configurations are described in more detail below.

Supported Platinum/Ammonia Oxidation Catalysts

Embodiments of the present invention include supported platinum, which can be included as an ammonia oxidation catalyst in the catalyst articles described herein. Preferably, the support contains a zeolite and/or a mixed oxide of SiO ₂ -Al ₂ O ₃ . In some embodiments, the platinum may be fixed to the support in solution, i. e. by pinning Pt in situ.

The catalytic articles of the present invention contain platinum on a carrier, the carrier containing a zeolite and/or a mixed oxide of SiO ₂ -Al ₂ O ₃ . In some embodiments, the platinum is present on the support in an amount of from about 0.5% to about 10% by weight based on the total weight of the platinum and the support; from about 1 wt.% to about 6 wt.% of the total weight of platinum and support; from about 1.5 wt.% to about 4 wt.% of the total mass of platinum and support; about 10 wt.% of the total mass of platinum and support; about 0.5 wt.% of the total mass of platinum and support; about 1 wt.% of the total mass of platinum and support; about 2 wt.% of the total mass of platinum and support; about 3 wt.% of the total mass of platinum and support; about 4 wt.% of the total mass of platinum and support; about 5 wt.% of the total mass of platinum and support; about 6 wt.% of the total mass of platinum and support; about 7 wt.% of the total mass of platinum and support; about 8 wt.% of the total mass of platinum and support; about 9 wt.% of the total mass of platinum and support; or about 10 wt.% of the total mass of platinum and support.

In those embodiments in which platinum is supported on the SiO ₂ -Al ₂ O ₃ mixed oxide, SiO ₂ may be present in an amount of from about 1% to about 80% by weight of the mixed oxide; from about 1 wt.% to about 75 wt.% mixed oxide; from about 1 wt.% to about 70 wt.% mixed oxide; from about 5 wt.% to about 70 wt.% mixed oxide; from about 10 wt.% to about 70 wt.% mixed oxide; from about 20 wt.% to about 70 wt.% mixed oxide; from about 30 wt.% to about 70 wt.% mixed oxide; from about 40 wt.% to about 70 wt.% mixed oxide; from about 50 wt.% to about 60 wt.% mixed oxide; about 1 wt.% mixed oxide; about 5 wt.% mixed oxide; about 10 wt.% mixed oxide; about 20 wt.% mixed oxide; about 30 wt.% mixed oxide; about 40 wt.% mixed oxide; about 50 wt.% mixed oxide; about 60 wt.% mixed oxide; about 70 wt.% mixed oxide; about 75 wt.% mixed oxide; or about 80 wt.% mixed oxide.

In embodiments in which platinum is supported on a zeolite, the outer surface area of a suitable zeolite may be at least about 30 m ² /g; at least about 40 m ² /g; at least about 50 m ² /g; at least about 60 m ² /g; at least about 70 m ² /g; at least about 80 m ² /g; at least about 90 m ² /g; or at least about 100 m ² /g. In some embodiments, the implementation of the average crystal size of a suitable zeolite may be about 2 microns or less; about 1.5 µm or less; about 1 µm or less; about 0.5 µm or less; about 0.3 µm or less; less than about 2 µm; less than about 1.5 microns; less than about 1 micron; less than about 0.5 microns; less than about 0.3 microns; about 0.1 µm to about 2 µm; about 0.3 µm to about 1.5 µm; or from about 0.5 µm to about 1 µm. In particular, the particle size may differ significantly from the size of the zeolite crystals, since the particle may be composed of accumulations of many smaller crystals. In some embodiments, the ratio of silica to alumina of a suitable zeolite is at least 100; at least 200; at least 250; at least 300; at least 400; at least 500; at least 600; at least 750; at least 800; or at least 1000. Zeolites are described in more detail below in the SCR catalyst section. In some embodiments, a suitable zeolite for supporting platinum on a support is selected from the group of framework types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, 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, BEA, MFI and FER, as well as mixtures and/or splices thereof. In some embodiments, a suitable platinum selection zeolite is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, BEA, MFI, and FER.

The catalyst articles of the present invention may contain one or more ammonia oxidation catalysts, also referred to as an ammonia slip catalyst (ASC). The preferred ammonia oxidation catalyst comprises supported platinum as described above, however, other or additional ammonia oxidation catalysts may be included in embodiments of the present invention. One or more ammonia oxidation catalysts may be included with or downstream of the SCR catalyst to oxidize excess ammonia and prevent its release to the atmosphere. In some embodiments, the ammonia oxidation catalyst may be incorporated on the same support as the SCR catalyst or blended with the SCR catalyst. In some embodiments, the ammonia oxidation catalyst material may be selected and formulated to promote ammonia oxidation instead of NO _x or N ₂ O production. In general, preferred catalyst materials comprise platinum, palladium, or a combination thereof. The ammonia oxidation catalytic converter contains platinum and/or palladium deposited on a metal oxide. In some embodiments, the implementation of the catalyst is located on the media with a high surface area, including, without limitation, alumina.

In some embodiments, the ammonia oxidation catalyst comprises a platinum group metal on a silica-containing support. The silica-containing material may be the following material: (1) silica; (2) a zeolite with a silica to alumina ratio of at least 200; and (3) amorphous silica doped alumina with SiO ₂ ≥40%. In some embodiments, the silica-containing material may be a material such as a zeolite with a silica to alumina ratio of at least 200; at least 250; at least 300; at least 400; at least 500; at least 600; at least 750; at least 800; or at least 1000. In some embodiments, the platinum group metal is present on the support in an amount of from about 0.5 wt.% to about 10 wt.% of the total weight of the platinum group metal and support; from about 1 wt.% to about 6 wt.% of the total weight of the platinum group metal and support; from about 1.5 wt.% to about 4 wt.% of the total weight of the platinum group metal and support; about 10 wt.% of the total weight of the platinum group metal and support; about 0.5 wt.% of the total weight of the platinum group metal and support; about 1 wt.% of the total weight of the platinum group metal and support; about 2 wt.% of the total weight of the platinum group metal and support; about 3 wt.% of the total weight of the platinum group metal and support; about 4 wt.% of the total weight of the platinum group metal and support; about 5 wt.% of the total weight of the platinum group metal and support; about 6 wt.% of the total weight of the platinum group metal and support; about 7 wt.% of the total weight of the platinum group metal and support; about 8 wt.% of the total weight of the platinum group metal and support; about 9 wt.% of the total weight of the platinum group metal and support; or about 10% by weight based on the total weight of the platinum group metal and support.

In some embodiments, the silica-containing carrier may comprise a molecular sieve having the structure type BEA, CDO, CON, FAU, MEL, MFI, or MWW.

SCR catalytic converter

The systems of the present invention may contain one or more SCR catalysts. In some embodiments, the catalyst article may comprise a first SCR catalyst and a second SCR catalyst. In some embodiments, the first SCR catalyst and the second SCR catalyst may have the same composition. In some embodiments, the first SCR catalyst and the second SCR catalyst may have different compositions.

An exhaust system in accordance with embodiments of the present invention may include an SCR catalyst that is located downstream of an injector for introducing ammonia or a compound that decomposes into ammonia to form exhaust gas. The SCR catalyst may be located directly downstream of the injector for injecting ammonia or an ammonia decomposable compound (eg, there is no intermediate catalyst between the injector and the SCR catalyst).

The SCR catalytic converter contains a support and a catalytic composition. The support may be a flow support or a filter support. In the case where the SCR catalyst comprises a flow-through support, the support may contain the SCR catalyst composition (i.e., the SCR catalyst composition is obtained by extrusion) or the SCR catalyst composition may be positioned or deposited on the support (i.e., the catalyst composition The SCR is applied to the substrate by a porous oxide coating method).

In the case where the SCR catalyst comprises a filter substrate, it is a selective catalytic reduction filter catalyst, which is herein abbreviated "SCRF" (selective catalytic reduction filter). The SCRF contains a filter substrate and a selective catalytic reduction (SCR) composition. References to the use of SCR catalysts in this application are also known to include the use of SCRF catalysts when applicable.

The selective catalytic reduction composition may be composed or consist essentially of a metal oxide SCR catalyst, base metal SCR catalyst, molecular sieve SCR catalyst, substituted metal molecular sieve, or mixtures thereof. Such SCR catalyst compositions are known in the art. Representative compositions are described in US Pat. Nos. 4,010,238 and 4,085,193, the contents of which are incorporated herein by reference in their entirety.

The selective catalytic reduction composition may be composed or consist essentially of a metal oxide based SCR catalyst. The SCR metal oxide catalyst composition contains vanadium or tungsten or a mixture thereof supported on a refractory oxide. The refractory oxide may be selected from the group consisting of alumina, silicon dioxide, titanium dioxide, zirconium oxide, cerium oxide, and combinations thereof.

The metal oxide SCR catalyst composition may contain or essentially consist of vanadium oxide (eg V ₂ O ₅ ) and/or tungsten oxide (eg WO ₃ ) supported on a refractory oxide selected from the group consisting of titanium dioxide (for example, TiO ₂ ), cerium dioxide (for example, CeO ₂ ) and mixed or complex oxide of cerium and zirconium (for example, C _x Zr _(1-x) O ₂ where x = from 0.1 to 0.9, preferably x = 0.2 to 0.5).

In the case where the refractory oxide is titanium dioxide (for example, TiO ₂ ), preferably the concentration of vanadium oxide is from 0.5 wt.% to 6 wt.% (for example, the SCR composition based on metal oxide) and/or the concentration of tungsten oxide (for example, WO ₃ ) is from 5 wt.% to 20 wt.%. More preferably, vanadium oxide (eg V ₂ O ₅ ) and tungsten oxide (eg WO ₃ ) are supported on titanium dioxide (eg TiO ₂ ). These catalytic converters may contain other inorganic materials such as SiO ₂ and ZrO ₂ acting as binders and promoters.

In the case where the refractory oxide is cerium dioxide (for example, CeO ₂ ), preferably the concentration of vanadium oxide is from 0.1 wt.% to 9 wt.% (for example, the SCR composition based on metal oxide) and/or the concentration of tungsten oxide (for example, WO ₃ ) is from 0.1 wt.% to 9 wt.%.

The metal oxide SCR catalyst composition may contain or consist essentially of vanadium oxide (eg V ₂ O ₅ ) and optionally tungsten oxide (eg WO ₃ ) supported on titanium dioxide (eg TiO ₂ ).

The selective catalytic reduction composition may be composed or consist essentially of a base metal SCR catalyst. Suitable base metals may include vanadium (V), molybdenum (Mo) and tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni ) and copper (Cu), as well as their mixtures.

If the SCR catalyst is a base metal or base metal mixed oxide, the catalyst article may further comprise at least one base metal promoter. As used herein, "promoter" refers to a substance which, when added to a catalytic converter, increases the activity of the catalytic converter. The base metal promoter may be in the form of a metal, a metal oxide, or mixtures thereof. The at least one base metal catalyst promoter may be selected from neodymium (Nd), barium (Ba), cerium (Ce), lanthanum (La), praseodymium (Pr), magnesium (Mg), calcium (Ca), manganese ( Mn), zinc (Zn), niobium (Nb), zirconium (Zr), molybdenum (Mo), tin (Sn), tantalum (Ta), strontium (Sr) and their oxides. The at least one base metal catalyst promoter may preferably be MnO ₂ , Mn ₂ O ₃ , Fe ₂ O ₃ , SnO ₂ , CuO, CoO, CeO ₂ and mixtures thereof. At least one base metal catalyst promoter may be added to the catalyst as a salt in aqueous solution, such as nitrate or acetate. At least one base metal catalyst promoter and at least one base metal catalyst, such as copper, may be impregnated with an aqueous solution on the oxide carrier material(s), may be added to the porous oxide coating containing the material(s). ) oxide carrier, or they may be impregnated with a carrier previously coated with a porous oxide.

The selective catalytic reduction composition may be composed or consist essentially of a molecular sieve SCR catalyst. The molecular sieve SCR catalyst composition contains a molecular sieve, which is optionally a transition metal substituted molecular sieve. Preferably, the SCR catalyst composition contains a substituted transition metal molecular sieve.

In general, a molecular sieve SCR catalyst composition may comprise a molecular sieve having an aluminosilicate structure (e.g., zeolite), an aluminophosphate structure (e.g., AlPO), a silicoaluminophosphate structure (e.g., SAPO), a heteroatom-containing aluminosilicate structure, a heteroatom-containing aluminophosphate structure ( eg MeAlPO where Me is a metal) or a heteroatom-containing silicoaluminophosphate structure (eg MeAPSO where Me is a metal) or mixtures thereof. The heteroatom (i.e., heteroatom-containing structure) may be selected from the group consisting of boron (B), gallium (Ga), titanium (Ti), zirconium (Zr), zinc (Zn), iron (Fe), vanadium (V ) and combinations of any two or more of them. Preferably, the heteroatom is a metal (eg, each of the above heteroatom-containing structures may be a metal-containing structure).

Preferably, the molecular sieve SCR catalyst composition contains or consists essentially of a molecular sieve having an aluminosilicate structure (eg, zeolite) or a silicoaluminophosphate structure (eg, SAPO). A zeolite molecular sieve is a microporous aluminosilicate having any of the framework structures listed in the zeolite structure database published by the International Zeolite Association (IZA; International Zeolite Association). Frameworks include, without limitation, frameworks of the CHA, FAU, BEA, MFI, MOR types. Non-limiting examples of zeolites having such structures include habasite, faujasite, zeolite Y, ultrastable zeolite Y, beta zeolite, mordenite, silicalite, zeolite X, and ZSM-5.

In the case where the molecular sieve has an aluminosilicate structure (for example, the molecular sieve is a zeolite), then, as a rule, the molar ratio of silica to alumina molar ratio (SAR) of the molecular sieve is from 5 to 200 (for example, 10 to 200), 10 to 100 (eg 10 to 30 or 20 to 80), eg 12 to 40 or 15 to 30. In some embodiments, the SAR of a suitable molecular sieve is >200; > 600; or > 1200. In some embodiments, the SAR of the molecular sieve is from about 1500 to about 2100.

Typically, the molecular sieve is microporous. The microporous molecular sieve has pores less than 2 nm in diameter (eg, in accordance with the IUPAC definition of "microporous" [see Pure & Appl. Chem., 66(8), (1994), 1739-1758)]).

The molecular sieve SCR catalyst composition may comprise a narrow pore molecular sieve (e.g., a molecular sieve with a maximum ring size of eight tetrahedral atoms), a medium pore molecular sieve (e.g., a molecular sieve with a maximum ring size of ten tetrahedral atoms), or a large pore molecular sieve. a sieve (eg, a molecular sieve whose maximum ring size is twelve tetrahedral atoms) or a combination of two or more of these.

In the case where the molecular sieve is a narrow pore molecular sieve, the narrow pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from the group consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, LTA, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON, or a mixture and/or splice of two or more of them. Preferably, the narrow pore molecular sieve has a framework structure represented by an FTC selected from the group consisting of CHA, LEV, AEI, AFX, EM, ERI, LTA, SFW, KFI, DDR and ITE. More preferably, the narrow pore molecular sieve has a framework structure represented by an FTC selected from the group consisting of CHA and AEI. The narrow pore molecular sieve may have a framework structure as represented by FTC CHA. The narrow pore molecular sieve may have a framework structure as represented by FTC AEI. In the case where the narrow pore molecular sieve is a zeolite and has a framework structure represented by FTC CHA, the zeolite may be a habasite.

In the case where the molecular sieve is a medium pore molecular sieve, the medium pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from the group consisting of 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 and WEN or a mixture and/or splice of two or more of them. Preferably, the medium pore molecular sieve has a framework structure represented by an FTC selected from the group consisting of FER, MEL, MFI and STT. More preferably, the medium pore molecular sieve has a framework structure represented by an FTC selected from the group consisting of FER and MFI, in particular MFI. In the case where the medium pore molecular sieve is a zeolite and has a framework structure represented by FTC, FER or MFI, the zeolite may be ferrierite, silicalite or ZSM-5.

In the case where the molecular sieve is a large pore molecular sieve, the large pore molecular sieve may have a framework structure represented by a Framework Type Code (FTC) selected from the group consisting of 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 and VET, or a mixture and/or splice of two or more of them. Preferably, the large pore molecular sieve has a framework structure represented by an FTC selected from the group consisting of AFI, BEA, MAZ, MOR and OFF. More preferably, the large pore molecular sieve has a framework structure represented by an FTC selected from the group consisting of BEA, MOR and MFI. In the case where the large pore molecular sieve is a zeolite and has a framework structure represented by FTC, BEA, FAU or MOR, the zeolite may be beta zeolite, faujasite, zeolite Y, zeolite X or mordenite.

The molecular sieve SCR catalyst composition preferably contains a transition metal substituted molecular sieve. The metal-substituted molecular sieve may contain at least one metal from one of Periodic Table Groups VB, VIB, VIIB, VIIIB, IB, or IIB applied to additional areas of the framework structure on the outer surface or within the channels, cavities, or frameworks of the molecular sieves. The metals may be present in one of several forms, including, without limitation, zero valence metal atoms or clusters, isolated cations, mononuclear or polynuclear oxycations, or extended metal oxides. The transition metal may be selected from the group consisting of cobalt, copper, iron, manganese, nickel, palladium, platinum, ruthenium and rhenium.

The transition metal may be present in an additional portion of the framework structure on the outer surface of the molecular sieve or within the channel, cavity or framework of the molecular sieve.

Typically, the transition metal substituted molecular sieve contains 0.10 wt% to 10 wt% substituted transition metal molecular sieve, preferably 0.2 wt% to 5 wt%.

The metal-substituted molecular sieve may be a copper (Cu) supported narrow pore molecular sieve having a copper content of from about 0.1% to about 20.0% by weight based on the total weight of the catalyst. More preferably, the copper content is from about 0.5% to about 15% by weight based on the total weight of the catalyst. Most preferably, the copper content is from about 1% to about 9% by weight, based on the total weight of the catalyst.

In general, the selective catalytic converter contains a selective catalytic reduction composition with a total concentration of 30.51 kg/m (0.5 g/in ³ ) to 244.09 kg/m ³ (4.0 g/in ³ ), preferably from 61.02 kg/m ³ (1.0 g/in ³ ) to 183.07 kg/m ³ (3.0 g/in ³ ) and 244.09 kg/m ³ (4.0 g/in ³ ).

The SCR catalyst composition may comprise a mixture of a metal oxide based SCR catalyst composition and a molecular sieve SCR catalyst composition. (a) The metal oxide SCR catalyst composition may contain or consist essentially of vanadium oxide (eg V ₂ O ₅ ) and optionally tungsten oxide (eg WO ₃ ) supported on titanium dioxide (eg TiO ₂ ) and (b) the molecular sieve SCR catalyst composition may contain a transition metal substituted molecular sieve.

In the case where the SCR catalyst is a SCRF, the filter substrate may preferably be a continuous flow wall filter substrate. The cell density of a continuous flow wall filter substrate (eg, SCR-DPF) is typically between 60 cells per square inch and 400 cells per square inch (cells per square inch; cpsi). Preferably, the cell density of the continuous flow wall filter substrate is from 100 cpsi to 350 cpsi, more preferably from 200 cpsi to 300 cpsi.

The wall thickness of the continuous flow wall filter substrate (eg average inner wall thickness) may be 0.20 mm to 0.50 mm, preferably 0.25 mm to 0.35 mm (eg about 0.30 mm).

In general, the porosity of an uncoated continuous flow wall filter substrate is 50% to 80%, preferably 55% to 75%, and more preferably 60% to 70%.

The average pore size of an uncoated solid flow wall filter substrate is typically at least 5 µm. Preferably, the average pore size is 10 µm to 40 µm, such as 15 µm to 35 µm, more preferably 20 µm to 30 µm.

The flow wall filter substrate may have a symmetrical cell design or an asymmetric cell design.

In general, in the case of SCRF, the selective catalytic reduction composition is located within the wall of a continuous flow wall filter substrate. In addition, the selective catalytic reduction composition may be located on the walls of the inlet channels and/or on the walls of the outlet channels.

Mixture

Embodiments of the present invention may include a mixture of (1) supported platinum and (2) SCR catalyst. In some embodiments, the weight ratio of SCR catalyst to supported platinum in the mixture is from about 3:1 to about 300:1; about 3:1 to about 250:1; about 3:1 to about 200:1; about 4:1 to about 150:1; about 5:1 to about 100:1; about 6:1 to about 90:1; about 7:1 to about 80:1; about 7:1 to about 100:1; about 8:1 to about 70:1; about 9:1 to about 60:1; from about 10:1 to about 50:1; about 3:1; about 4:1; about 5:1; about 6:1; about 7:1; about 8:1; about 9:1; about 10:1; about 15:1; about 20:1; about 25:1; about 30:1; about 40:1; about 50:1; about 75:1; about 100:1; about 125:1; about 150:1; about 175:1; about 200:1; about 225:1; about 250:1; about 275:1; or about 300:1.

The term "active component load" refers to the mass of the platinum support + the mass of platinum + the mass of the first SCR catalyst in the mixture. In some embodiments, the platinum content of the active component load is from about 0.01% to about 0.25% by weight, inclusive; from about 0.04 wt.% to about 0.2 wt.% inclusive; from about 0.07 wt.% to about 0.17 wt.% inclusive; from about 0.05 wt.% to about 0.15 wt.% inclusive; about 0.01% by weight; about 0.02% by weight; about 0.03% by weight; about 0.04% by weight; about 0.05% by weight; about 0.06% by weight; about 0.07% by weight; about 0.08% by weight; about 0.1% by weight; about 0.12% by weight; about 0.15% by weight; about 0.17% by weight; about 0.2 wt.%; about 0.22% by weight; or about 0.25 wt.%.

In some embodiments, the mixture comprising supported platinum and SCR catalyst further comprises at least one of palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), or rhodium (Rh).

Substrate

Each of the catalysts of the present invention may further comprise a flow bed or a filter bed. In one embodiment, the catalyst may be applied to the flow or filter substrate, and is preferably applied to the flow or filter substrate by a porous oxide coating method.

The combination of an SCR catalyst and a filter is known as a selective catalytic reduction filter (SCRF catalyst). The SCRF catalytic converter is a single-substrate device that combines the functionality of an SCR and a diesel particulate filter and is suitable for embodiments of the present invention as needed. It should be understood that the description and references to the SCR catalyst in this application also refer to the SCRF catalyst, where applicable.

A flow or filter substrate is a substrate that is capable of containing catalytic/adsorbent components. The substrate is preferably a ceramic substrate or a metal substrate. The ceramic substrate can be made from any suitable refractory material, such as alumina, silica, titanium oxide, cerium oxide, zirconium oxide, magnesium oxide, zeolites, silicon nitride, silicon carbide, zirconium silicates, magnesium silicates, aluminosilicates and metal aluminosilicates (such as cordierite and spodumene), or mixtures or mixtures of oxides of any two or more of these. Most preferred are cordierite, magnesium aluminum silicate and silicon carbide.

The metal substrates can be made from any suitable metal, and in particular from heat resistant metals and metal alloys such as titanium and stainless steel, as well as from ferritic alloys containing iron, nickel, chromium and/or aluminum in addition to other metal impurities.

The flow substrate is preferably a flow-through solid substrate having a porous structure with a plurality of fine parallel thin-walled channels extending axially through the substrate and extending through from the inlet end or outlet end of the substrate. The cross section of the substrate channel may be of any shape, but is preferably square, sinusoidal, triangular, rectangular, hexagonal, trapezoidal, round or oval. The flow substrate may also have high porosity, which allows the catalyst to penetrate the walls of the substrate.

The filter substrate is preferably a solid substrate filter with flow walls. The channels of the filter with flow walls are alternately blocked, which allows the flow of exhaust gases to enter the channel from the inlet end and then flow through the walls of the channel and exit the filter through another channel leading to the outlet end. In this way, particles in the exhaust stream are captured by the filter.

The catalyst/adsorber may be added to the flow or filter substrate by any known means such as porous oxide coating techniques.

Configurations

Embodiments of the present invention relate to catalyst articles comprising a first coating and a second coating, wherein the first coating comprises a mixture of (1) supported platinum and (2) a first SCR catalyst, while the second coating comprises a second SCR catalyst. Catalytic products can be obtained in various configurations. In some embodiments, the coatings are arranged such that the exhaust gas comes into contact with the second coating prior to contact with the first coating. In some embodiments, the implementation of the second catalytic converter SCR is located on the inlet side of the mixture. In some embodiments, the SCR catalyst is located on the downstream side of the mixture.

In the first configuration, the catalyst may comprise a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst, and a second coating containing a second SCR catalyst, wherein the second coating is located in a layer on top of the first coating, wherein the second the coating covers the entire first coating. In FIG. 1 shows an example of such a configuration in which a second SCR catalyst is located in the exhaust gas stream on top of the mixture, with the second SCR catalyst covering the entire mixture.

In a second configuration, the catalyst may comprise a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst and a second coating containing a second SCR catalyst, the first coating extending from the outlet end to the inlet end, covering less than the entire length of the substrate, with the second coating extending along the entire length of the substrate, completely overlapping the first coating. In FIG. 2 shows an example of such a configuration in which a second SCR catalyst is positioned in the exhaust gas stream ahead of the mixture, with the second SCR catalyst completely shutting off the mixture.

In a third configuration, the catalyst may comprise a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst and a second coating containing a second SCR catalyst, the first coating extending from the outlet end to the inlet end, covering less than the entire length of the substrate, with the second coating extending from the inlet end to the outlet end, partially overlapping the first coating. The second SCR catalyst may overlap the first coating in an amount of from about 10% to about 95% inclusive, preferably from about 50% to about 95% inclusive. In FIG. 3 shows an example of such a configuration in which a second SCR catalyst is located in the exhaust gas stream before the mixture, with the second SCR catalyst covering a portion of the mixture rather than the entire mixture. In FIG. 3 the second SCR catalytic converter covers about 40% of the mixture.

In a fourth configuration, the catalyst may comprise a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst and a second coating containing a second SCR catalyst, the first coating extending from the outlet end to the inlet end, covering less than the entire length of the substrate, with the second coating extending from the inlet end to the outlet end without overlapping the first coating. There may be a space between the first coating and the second coating, wherein the first coating and the second coating may touch but not overlap, or the first coating and the second coating may overlap slightly or slightly. In FIG. 4 shows an example of such a configuration in which a second SCR catalyst is located in the exhaust gas stream ahead of the mixture and the second SCR catalyst is in contact with, but not overlapping with, the mixture.

In a fifth configuration, the catalyst may comprise a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst and a second coating containing a second SCR catalyst, the first coating extending from the inlet end to the outlet end, covering less than the entire length of the substrate, and the second coating extends along the entire length of the substrate, completely overlapping the first coating. In FIG. 5 shows an example of such a configuration in which the second SCR catalytic converter covers the entire mixture, with part of the second SCR catalyst located in the exhaust gas stream behind the mixture.

In a sixth configuration, the catalyst may comprise a first coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst and a second coating containing a second SCR catalyst, the first coating extending from the inlet end to the outlet end, covering less than the entire length of the substrate, with the second coating extending from the outlet end to the inlet end, covering less than the entire length of the substrate and partially overlapping the first coating. The second SCR catalyst may overlap the mixture in an amount of from about 10% to about 95% inclusive, preferably from about 50% to about 95% inclusive. In FIG. 6 shows an example of such a configuration in which the second SCR catalytic converter covers part of the mixture rather than the whole mixture, with part of the second SCR catalyst located in the exhaust gas stream behind the mixture. In FIG. 6 the second SCR catalytic converter covers about 95% of the mixture.

In the seventh configuration, the catalyst may include a first layer containing a third SCR catalyst. The first layer may be partially but not completely coated with a coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst. The mixture may coat the third SCR catalyst in an amount of from about 10% to about 95% inclusive, preferably from about 50% to about 95% inclusive. The mixture may be coated with a second SCR catalyst, with the coating of the second SCR catalyst covering the entire coating of the mixture. In FIG. 7 shows an example of such a configuration in which the third SCR catalyst is the bottom layer on the substrate, with the second layer containing the mixture partially covering the third SCR catalyst, and the third layer containing the second SCR catalyst located on top of the second layer and covering the entire mixture layer. .

In an eighth embodiment, the catalyst may comprise a first layer containing a third SCR catalyst. The first layer may be partially but not completely coated with a coating containing a mixture of (1) supported platinum and (2) a first SCR catalyst. The mixture may coat the third SCR catalyst in an amount of from about 10% to about 95%, inclusive, preferably from about 50% to about 95%. The mixture may be coated comprising a second SCR catalyst, wherein the second SCR catalyst partially but not completely covers the coating of the mixture, and a portion of the coating of the second SCR catalyst is also located downstream of the mixture, and also coats a portion of the third SCR catalyst downstream of the mixture layer. The second SCR catalyst may coat the third SCR catalyst in an amount of from about 10% to about 95% inclusive, preferably from about 50% to about 95% inclusive. In FIG. 8 shows an example of such a configuration in which the third SCR catalyst is the bottom layer on the substrate, the second layer contains a mixture that partially but not completely covers the third SCR catalyst, and the third layer contains the second SCR catalyst located on top of the second layer and partially, but not completely covering the layer of the mixture. In FIG. 8, the mixture layer covers about 60% of the first layer, and the layer with the second SCR catalyst covers about 20% of the first layer. The term "cover" means the part of the layer that is in direct contact with another layer.

Reductant/urea injector

Systems in accordance with some embodiments of the present invention may include means for introducing a nitrogenous reductant into the exhaust system upstream of the ammonia slip catalyst. It may be preferred that the means for introducing the nitrous reductant into the exhaust system is directly upstream of the ammonia slip catalyst (eg, there is no intermediate catalyst between the means for introducing the nitrous reductant and the ammonia slip catalyst).

The reducing agent is added to the flowing exhaust gas by any suitable means for introducing the reducing agent into the exhaust gas. Suitable means include an injector, nebulizer or feeder. Such means are well known in the art.

The nitrogenous reducing agent for use in the system may be ammonia per se, hydrazine, or an ammonia precursor selected from the group consisting of urea, ammonium carbonate, ammonium carbamate, ammonium hydrogen carbonate, and ammonium formate. Urea is particularly preferred.

The exhaust system may also include means for controlling the introduction of a reductant into the exhaust gas to reduce its NOx content. Preferred controls may include an electronic control unit, optionally an engine control unit, and may further include a NOx sensor located downstream of the NO recovery catalyst.

Preparation method

Catalyst products in accordance with some embodiments of the present invention can be obtained by any suitable method known in the art. In the case of catalytic articles containing supported platinum, such platinum can be supported in solution, i. in situ, so that a separate prefixing process is not required. To obtain a coating that contains a mixture of (1) supported platinum and (2) SCR catalyst, the following steps can be performed:

• combining the carrier material with water in a portion and mixing;

• addition of an organic acid which acts as a reducing agent for platinum and/or creates a reducing environment in a later calcination step. Examples of a suitable organic acid may include citric acid, succinic acid, oxalic acid, ascorbic acid, acetic acid, formic acid, and combinations thereof;

• adding platinum nitrate per batch in such an amount that the molar ratio of organic acid to platinum is between 20:1 and 1:1; from 10:1 to 1:1; or from 5:1 to 1:1;

• association of a portion of platinum with a portion of SCR;

• regulation of rheology and percentage of solids in the combined portion, coating and firing at a temperature of 500°C ‒ 550°C in air.

Mode of application

The method for reducing emissions from an exhaust gas stream may include bringing the exhaust gas stream into contact with the catalytic article described herein. In some embodiments, a method for improving NH ₃ conversion in an exhaust gas at a temperature of about 300° C. or below may include contacting an exhaust gas containing ammonia with a catalyst article described herein. In some embodiments, a method for treating an exhaust gas containing ammonia and NOx may include contacting an exhaust gas containing ammonia with a catalyst article described herein. In some embodiments, the mass ratio of ammonia to NOx (ANR; ratio of ammonia to NOx) in the exhaust gas is >1.0 for at least part of the time the system is running.

Advantages

The catalytic articles of the present invention may provide improved catalytic activity and selectivity. Ammonia slip catalysts that contain a layer with a mixture of (1) a platinum group metal on a support and (2) an SCR catalyst provide improvements in both N ₂ O generation and NOx reduction, however, some of these catalytic converters may have drawbacks and / or restrictions. In particular, if such catalysts require pre-fixation of the platinum group metal on the carrier, the use of such catalysts involves additional costs associated with the pre-fixation step and they may have a lower NH ₃ conversion at low temperatures (for example, below 300°C ) and under difficult conditions (such as high NH ₃ slip and/or high space velocity).

Surprisingly, it has been found that the catalyst articles of the present invention can minimize or reduce the aforementioned disadvantages and limitations. For example, when fixing a platinum group metal on a support in solution, i.e. in situ, there are no additional costs associated with the pre-fixation step. In addition, such catalyst articles exhibit improved NH ₃ conversion at low temperatures (eg, below 300° C.) and under difficult conditions (such as high NH ₃ slip and/or high space velocity).

In some embodiments, the catalytic articles of the present invention containing a platinum group metal that is supported in solution may have an equivalent or increased activity in converting NH ₃ at temperatures of about 300°C or lower compared to a catalyst article that is equivalent, except that a platinum group metal is pre-fixed on the support. In some embodiments, catalyst articles of the present invention containing a platinum group metal that is supported in solution may have improved NH ₃ conversion activity at temperatures of about 300° C. or lower compared to a catalyst article that is equivalent, except having a platinum group metal pre-mounted on the carrier, wherein the catalytic article of the invention exhibits an improvement in NH ₃ conversion at temperatures of about 300° C. or lower in the range of about 30% to about 100%; about 35% to about 95%; about 40% to about 90%; about 45% to about 85%; about 50% to about 80%; about 55% to about 75%; about 30% to about 50%; about 35% to about 55%; about 40% to about 60%; about 50% to about 70%; about 60% to about 80%; about 70% to about 90%; about 80% to about 100%; over 30%; more than 40%; more than 50%; more than 60%; more than 70%; more than 80%; or more than 90%.

In some embodiments, catalytic articles of the present invention containing platinum on a support containing high surface area zeolite (>50 m ² /g) or mixed oxide SiO ₂ -Al ₂ O ₃ can have equivalent or increased activity in converting NH ₃ at temperatures of about 300° C. or lower compared to a catalyst article that is equivalent, except that it contains a platinum group metal supported on a support other than high surface area zeolite (>50 m ² /g) or mixed oxide SiO ₂ -Al ₂ O ₃ . In some embodiments, catalytic articles of the present invention containing platinum on a support containing high surface area zeolite (>50 m ² /g) or mixed oxide SiO ₂ -Al ₂ O ₃ can have equivalent or increased activity in converting NH ₃ at temperatures of about 300° C. or lower compared to a catalyst article that is equivalent, except that it contains a platinum group metal supported on a support other than high surface area zeolite (>50 m ² /g) or mixed oxide SiO ₂ -Al ₂ O ₃ and the catalytic product of the present invention shows an improvement in the conversion of NH ₃ at temperatures of about 300°C or below in the range from about 30% to about 100%; about 35% to about 95%; about 40% to about 90%; about 45% to about 85%; about 50% to about 80%; about 55% to about 75%; about 30% to about 50%; about 35% to about 55%; about 40% to about 60%; about 50% to about 70%; about 60% to about 80%; about 70% to about 90%; about 80% to about 100%; over 30%; more than 40%; more than 50%; more than 60%; more than 70%; more than 80%; or more than 90%.

In the present description and the appended claims, the singular forms include references to the plural, unless the context clearly requires otherwise. Thus, for example, reference to "catalyst" includes a mixture of two or more catalysts, and the like.

The term "ammonia slip" refers to the amount of unreacted ammonia that passes through the SCR catalyst.

The term "carrier" means the material to which the catalytic converter is attached.

The term "calcination" or "calcination" means heating a material in air or oxygen. This definition is consistent with the IUPAC definition of calcination. (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by: A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Revised XML online: http://goldbook.iupac. org (2006-), prepared by: M. Nic, J. Jirat, B. Kosata, updated by A. Jenkins, ISBN 0-9678550-9-8, doi:10.1351/goldbook.) exchange of metal ions in the catalytic converter; and for attaching the catalytic converter to the substrate. The temperature used in the calcination depends on the components in the calcined material and is preferably from about 400°C to about 900°C for about 1-8 hours. In some cases, the calcination can be carried out up to a temperature of about 1200°C. In applications involving the processes described herein, calcination is advantageously performed at temperatures from about 400°C to about 700°C for about 1-8 hours, preferably at temperatures from about 400°C to about 650°C for about 1-4 hours.

Where a range or ranges are specified for various numeric elements, the specified range or ranges may include values unless otherwise specified.

The term "selectivity N ₂ "means the percentage conversion of ammonia to nitrogen.

The terms "diesel oxidation catalyst" (DOC; diesel oxidation catalyst), "diesel exothermic catalytic converter" (DEC; diesel exotherm catalyst), "NOx scavenger", "SCR/PNA" adsorber), "cold-start catalyst" (CSC) and "three-way catalyst" (TWC; three-way catalyst) are well known in the art and are used to describe the various types of catalytic converters used to treat exhaust gases. gases in combustion processes.

The term "platinum group metal" or PGM (platinum group metal) refers to platinum, palladium, ruthenium, rhodium, osmium and iridium. The platinum group metals are preferably platinum, palladium, ruthenium or rhodium.

The terms "downstream" and "upstream" describe the orientation of the catalyst or substrate, in which the flow of exhaust gas flows from the inlet end to the outlet end of the substrate or article.

The following examples are merely illustrative of the invention; many variations will be apparent to those skilled in the art that are within the spirit of the invention and the scope of the claims.

Examples

In situ blended catalysts have been prepared containing platinum on a carrier blended with an SCR catalyst. Various catalytic converters were prepared using various carriers, as indicated in Table 1 below.

In situ fixing of platinum was used to prepare in situ mixture catalysts; The platinum precursor was solution-mounted on the support and therefore no separate pre-fixing process was required, as described below:

• combining the carrier material with water in a portion and mixing;

• addition of an organic acid which acts as a reducing agent for platinum and/or creates a reducing environment in a later calcination step. Examples of a suitable organic acid may include citric acid, succinic acid, oxalic acid, ascorbic acid, acetic acid, formic acid, and combinations thereof;

• adding platinum nitrate per batch in such an amount that the molar ratio of organic acid to platinum is between 20:1 and 1:1; from 10:1 to 1:1; or from 5:1 to 1:1;

• association of a portion of platinum with a portion of SCR;

• regulation of rheology and percentage of solids in the combined portion, coating and firing at a temperature of 500°C ‒ 550°C in air.

Table 1. Properties of support materials used to fix Pt in situ

Name Compound Available surface area of platinum ( ^m2 /g)* Aluminium oxide _{Al2O3 _} 140 Aluminum oxide nanoparticles _{Al2O3 _} 220 Highly dispersed silicon dioxide _SiO2 200 silica gel _SiO2 500 Silicon dioxide–titanium dioxide 10% _SiO2 , 90% _TiO2 110 Silicon dioxide–aluminum oxide 40% SiO ₂ , 60% Al ₂ O ₃ 500 Zeolite MFI, SiO ₂ to Al ₂ O ₃ ratio = 2000 5 Zeolite nanoparticles MFI, SiO ₂ to Al ₂ O ₃ ratio = 400 80

*Note: for oxides, total BET surface area is used; for zeolites, the outer surface area is used according to the schedule t

The following catalytic converters have been produced:

Reference ASC:

As a reference example, a two-layer composition was used containing Pt on the bottom layer of alumina and the top layer of SCR.

The bottom layer was applied to the ceramic substrate using a porous oxide coating containing 0.17 wt.% Pt on a mixture of alumina and unmodified zeolite. The porous oxide coating was then deposited on the ceramic substrate, and then the porous oxide coating was drawn into the substrate using vacuum. The product was dried and calcined at a temperature of about 500°C for about 1 hour. The load Pt on the product was 0.11 kg/m ³ (3 g/ft ³ ).

The top layer was deposited on the substrate coated with the bottom layer using a second porous oxide coating containing Cu–CHA, then the porous oxide coating was drawn into the substrate using vacuum. The product was dried and calcined at a temperature of about 500°C for about 1 hour. The loading of Cu-CHA in the top layer was 109.84 kg/m ³ (1.8 g/in ³ ).

ASC mixture of prefixed Pt-zeolite.

The lower layer was deposited on a ceramic substrate using a porous oxide coating containing a mixture of 4 wt % Pt on ZSM–5 (MFI frame structure with SAR = 2000) and Cu–CHA. The porous oxide coating was then deposited on the ceramic substrate, and then the porous oxide coating was drawn into the substrate using vacuum. The product was dried and calcined at a temperature of about 500°C for about 1 hour. The load of Pt, zeolite and Cu-CHA on the product was respectively 0.11 kg/m ³ (3g/ft ³ ), 2.75 kg/m ³ (0.045 g/in ³ ) and 54.92 kg/m ³ (0 .9 g/in ³ ).

The top layer was deposited on the substrate coated with the bottom layer using a second porous oxide coating containing Cu–CHA, then the porous oxide coating was drawn into the substrate to a distance of about 50% of the substrate length using vacuum. The product was dried and calcined at a temperature of about 500°C for about 1 hour. The loading of Cu-CHA in the top layer was 109.84 kg/m ³ (1.8 g/in ³ ).

ASC mixtures in situ.

In accordance with the previously described procedure, two-layer compositions were obtained containing a mixture of support with fixed Pt in situ with a lower layer of Cu–CHA and an upper layer of SCR with various support materials for Pt.

The lower layers contained 3.5 wt.% Pt on the supports shown in Table 1. The load of Pt, support material and Cu-CHA on the product was respectively 0.11 kg/m ³ (3 g/ft ³ ), 3.05 kg / m ³ (0.05 g/in ³ ) and 54.92 kg/m ³ (0.9 g/in ³ ).

The top layer was deposited on the substrate coated with the bottom layer using a second porous oxide coating containing Cu–CHA, then the porous oxide coating was drawn into the substrate using vacuum. The product was dried and calcined at a temperature of about 500°C for about 1 hour. The loading of Cu-CHA in the top layer was 109.84 kg/m ³ (1.8 g/in ³ ).

The resulting catalytic converters were tested under the following conditions:

- Holding conditions: 650°C at 10% H ₂ O in air for 50 hours

- Test conditions: 1 min., 1000 ppm NH ₃ pulse in 10% O ₂ , 4.5% H ₂ O, 4.5% CO ₂ , N ₂ balance; at SV = 120000 h ^–1

In FIG. 9 shows the outcome of NH ₃ , N ₂ O and NOx breakthrough when various ASCs were exposed to a one minute NH ₃ pulse of 1000 ppm. All catalytic converters have an equivalent load of Pt at the same load at 0.11 kg/m ³ (3 g/ft ³ ) and Cu-CHA top layer. Compared to the reference ASC, all ASC blends (both prefixed Pt-zeolite formulations and in situ Pt carrier formulations) had clear advantages in reducing N ₂ O and NOx generation. However, the efficiency of NH ₃ conversion is highly dependent on the choice of Pt carrier material. Compared to ASC mixtures with pre-fixed Pt-zeolite, all in situ ASC mixtures with alumina, silica-alumina, or silica-titania as Pt support showed similar or improved NH ₃ conversion. Samples with pure silica-containing materials (fine silica, silica gel, and silica-containing zeolite) as Pt support generally have the lowest NH ₃ conversion; the only exception being the nano zeolite, which exhibited the highest NH ₃ conversion activity of any mixture tested by ASC.

Claims (49)

1. A catalytic product for exhaust gas treatment, comprising: a substrate having an inlet end and an outlet end; a first coating containing a mixture of: (1) supported platinum and (2) a first SCR catalyst; And a second coating comprising a second SCR catalyst; moreover, the carrier contains at least one of zeolite or mixed oxide SiO ₂ -Al ₂ O ₃ ; moreover, SiO ₂ is present in an amount of from about 1 wt. % to about 70 wt. % mixed oxide, while the platinum is fixed on the carrier in a solution containing the first SCR catalyst. 2. The catalytic product according to claim 1, characterized in that the carrier contains a mixed oxide SiO ₂ -Al ₂ O ₃ . 3. Catalytic product under item 2, characterized in that SiO ₂ is present in an amount of from about 40 wt. % to about 70 wt. % mixed oxide. 4. Catalytic product according to claim 1, characterized in that the carrier contains zeolite. 5. Catalyst article according to claim 4, characterized in that the outer surface area of the zeolite is at least 50 m ² /g. 6. Catalyst article according to claim 4, characterized in that the outer surface area of the zeolite is at least 70 m ² /g. 7. Catalyst article according to claim 4, characterized in that the outer surface area of the zeolite is at least 100 m ² /g. 8. Catalyst article according to claim. 4, characterized in that the average size of the zeolite crystals is less than about 1 micron. 9. The catalytic article of claim. 4, characterized in that the average crystal size of the zeolite is less than about 0.5 microns. 10. Catalyst article according to claim 4, characterized in that the average size of the zeolite crystals is less than about 0.3 microns. 11. The catalytic product according to claim 4, characterized in that the ratio of silicon dioxide to alumina in the zeolite is more than 100. 12. The catalytic product according to claim 4, characterized in that the ratio of silicon dioxide to alumina in the zeolite is more than 300. 13. The catalytic product according to claim 4, characterized in that the ratio of silicon dioxide to alumina in the zeolite is more than 1000. 14. The catalytic product according to claim 4, characterized in that the zeolite is selected from the group of frame structure types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT , EAB, EDI, EPI, ERI, 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, BEA, MFI and FER, as well as mixtures and/or splices thereof. 15. Catalyst article according to claim 4, characterized in that the zeolite is selected from the group of frame structure types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR, ITE, BEA, MFI and FER. 16. Catalytic product according to claim 1, characterized in that the second coating completely overlaps the first coating. 17. The catalytic product according to claim 1, characterized in that the second coating partially overlaps the first coating. 18. Catalyst article according to claim. 1, characterized in that the second coating extends from the inlet end to the outlet end, covering less than the entire length of the substrate. 19. Catalyst article according to claim. 1, characterized in that the first coating extends from the outlet end to the inlet end, covering less than the entire length of the substrate. 20. Catalyst article according to claim 1, characterized in that the second SCR catalyst is located on the inlet side of the coating containing the platinum-supported mixture with the first SCR catalyst. 21. Catalyst article according to claim 1, characterized in that the second SCR catalyst is located on the downstream side of the coating containing the platinum-supported mixture with the first SCR catalyst. 22. Catalytic product under item 1, characterized in that platinum is present in an amount constituting at least one of the following values: (a) 0.01-0.3 wt. %; (b) 0.03-0.2 wt. %; (c) 0.05-0.17 wt. % and (d) 0.07-0.15 wt. % inclusive relative to the weight of the platinum support + the weight of platinum + the weight of the first SCR catalyst in the mixture. 23. Catalytic article according to claim 1, characterized in that the mass ratio of the first SCR catalyst to supported platinum is in the range of at least one of the following values: (a) 0:1 to 300:1, (b) 3:1 to 300:1, (c) 7:1 to 100:1, and (d) 10:1 to 50:1 inclusive in the calculation to the mass of these components. 24. Catalyst article according to claim 1, characterized in that the mixture additionally contains at least one of palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru) or rhodium (Rh). 25. Catalyst article according to claim 1, wherein the second SCR catalyst is a base metal, a base metal oxide, a molecular sieve, a substituted metal molecular sieve, a mixed oxide, or a mixture thereof. 26. The catalytic product according to claim 25, characterized in that the base metal is selected from the group consisting of vanadium (V), molybdenum (Mo) and tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn) , iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu), as well as their mixtures. 27. The catalyst article of claim 25, further comprising at least one base metal promoter. 28. Catalyst article according to claim 25, characterized in that the molecular sieve or metal-substituted molecular sieve is narrow-pore, medium-pore, large-pore, or a mixture thereof. 29. The catalytic product according to claim 25, characterized in that the second SCR catalyst contains a molecular sieve selected from the group consisting of: aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminophosphate (MeAlPO) molecular sieves sieves, silicoaluminophosphate (SAPO) molecular sieves and metal-substituted silicoaluminophosphate (MeAPSO) molecular sieves, as well as mixtures thereof. 30. The catalytic product according to claim 25, characterized in that the second SCR catalyst contains a narrow-pore molecular sieve selected from the group of types of framework structure consisting of: ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON, as well as mixtures and/or splices thereof. 31. Catalyst article according to claim 25, characterized in that the second SCR catalyst contains a narrow-pore molecular sieve selected from the group of frame structure types consisting of: CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. 32. The catalytic product according to claim 25, characterized in that the second SCR catalyst contains a medium pore molecular sieve selected from the group of types of framework structure consisting of: AEL, AFO, ANT, 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 and WEN, as well as mixtures and/or splices thereof. 33. The catalytic product according to claim 25, characterized in that the second SCR catalyst contains a large-pore molecular sieve selected from the group of frame structure types consisting of 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 and VET, as well as their mixtures and/or splices. 34. Catalytic article according to claim 1, characterized in that the second SCR catalyst contains promoted Ce-Zr or promoted MnO ₂ . 35. Catalyst article according to claim 1, characterized in that the first SCR catalyst is a Cu-SCR catalyst or a Fe-SCR catalyst. 36. Catalyst article according to claim 1, characterized in that the support is cordierite, high porosity cordierite, metal support, extruded SCR, filter or SCRF. 37. An exhaust system comprising the catalyst article of claim 1 and a means for introducing a reductant upstream of the catalyst article. 38. The exhaust system of claim 37, further comprising a third SCR catalyst providing ≤100% NOx conversion, wherein the third SCR catalyst is a Cu-zeolite SCR catalyst and is located in the exhaust gas stream upstream of the catalyst article according to item 1. 39. A method for improving the conversion of NH ₃ in the exhaust gas at a temperature of about 300°C or lower, and this method includes contacting the exhaust gas containing ammonia with the catalytic product according to claim 1. 40. A method for improving the conversion of NH ₃ in an exhaust gas at a temperature of about 300° C. or lower, said method comprising contacting an exhaust gas containing ammonia with a catalyst article according to claim 2. 41. The method of claim. 40, characterized in that the conversion of NH ₃ is greater in the range from about 30% to about 100% compared to a catalytic converter having a comparable composition, in which platinum is pre-fixed on the carrier. 42. A method for purifying an exhaust gas containing ammonia and NOx, the method comprising contacting an exhaust gas containing ammonia with a catalyst article according to claim 1. 43. The method of claim. 42, characterized in that the mass ratio of ammonia to NOx in the exhaust gas is >1.0 during at least part of the time the system is running.

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