JP2021090961A - Exhaust system for diesel engine - Google Patents

Abstract

To provide a diesel engine exhaust system capable of obtaining a high NOx conversion rate at a low temperature.SOLUTION: A diesel engine exhaust system includes: (a) an emission control device for oxidizing carbon monoxide and/or hydrocarbon (HC), which contains a platinum group metal selected from combinations of platinum and palladium, and a base material; (b) an injector for introducing an ammonia precursor into an exhaust gas, which is downstream of the emission control device; (c) a first selective catalytic reduction catalyst which contains a base material and a first selective catalytic reduction composition and is downstream of the injector, the base material being a flow-through base material or a filtering base material; and (d) a second selective catalytic reduction catalyst which is downstream of the first selective catalytic reduction catalyst and contains a flow-through base material and a second selective catalytic reduction composition. At least one of the emission control device and the first selective catalytic reduction catalyst has the filtering base material.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust system for a diesel engine. The present invention also relates to a vehicle equipped with an exhaust system and a method of treating exhaust gas generated by a diesel engine.

Diesel engines are subject to regulatory legislation by intergovernmental agencies around the world: at least four pollutants: carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NO _x ) and patties. It produces an exhaust that generally contains curated matter (PM). There are various emission controls for treating one or more of the various pollutants. These emission controls are often combined as part of an exhaust system to ensure that all four pollutants are treated prior to the emission of the emissions into the environment.

Diesel engines, especially large (HD) diesel engines, are designed to improve fuel economy. As a result of such a design, diesel engines _{output higher levels of nitrogen oxides (NO x} ) and the engine's exhaust system provides ever-higher NO _x conversion rates to meet emission regulations. Is required.

Selective catalytic reduction (SCR) is a diesel engine, has been demonstrated to be an effective solution to particularly satisfy NO _x emissions requirements and regulations HD diesel engines. Progression of NOx emission reduction SCR system with the fuel efficiency increasing demand will allow more of the NO _x emissions of the engine. However, such requirements are difficult for current exhaust system designs, typically consisting of a diesel oxidation catalyst (DOC), a catalyzed suit filter (CSF) and an SCR catalyst.

One approach is to replace the CSF with a diesel particulate filter (DPF) coated with the SCR catalyst composition while keeping the flow-through SCR catalyst downstream. An example of such an exhaust system is described in SAE2014-01-1525. Selective catalytic reduction catalysts on the filter substrate _{have been shown to have high NO x} conversion capacity (see AE2008-01-0072, SAE2011-01-1312 and SAE2012-01-0843).

Further, it is desirable to minimize the amount of nitrous oxide in the exhaust gas (N 2 _O). US Environmental Protection Agency, pound of nitrous oxide (N 2 _O) is the effect of warming the air is stated that pound of carbon dioxide (CO ₂₎ that of 300 times or more. Nitrous oxide _(N 2 O) is also ozone-depleting substances (ODS). Nitrous oxide (N 2 _O) molecules are estimated to remain in about 120 years in the atmosphere before being removed or destroyed. The current laws regulating engine exhaust material, because it is regulated separately as greenhouse gas (GHG), no restriction on the nitrous oxide (N 2 _O).

The present invention, especially at low temperatures - in (for example, "cold start" if the diesel engine is started from cold), an exhaust system capable of providing a very high NO _x conversion. Exhaust system also the amount of the resulting N _{2 O} as a by-product in _the NO _x reduction reaction can be minimized.

The present invention is an exhaust system for treating exhaust gas generated by a diesel engine.
(A) An emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) containing a platinum group metal (PGM) and a base material, wherein the platinum group metal (PGM) is platinum (Platinum (PGM). With an emission control device selected from Pt), palladium (Pd) and combinations thereof;
(B) With an injector for introducing an ammonia precursor into the exhaust gas and downstream of an emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC);
(C) A first selective catalytic reduction catalyst containing a substrate and a first selective catalytic reduction composition downstream of an injector for introducing an ammonia precursor into the exhaust gas, wherein the substrate flows. With a first selective catalytic reduction catalyst that is either a through substrate or a filtering substrate;
(D) Downstream of the first selective catalytic reduction catalyst, with a flow-through substrate and a second selective catalytic reduction catalyst containing a second selective catalytic reduction (SCR) composition, and
Provided is an exhaust system in which at least one of the emission control device and the first selective catalytic reduction catalyst has a filtering substrate.

The present inventors have found that an excellent NO _x conversion rate can be obtained by using the exhaust system of the present invention. NO _x conversion provided by the exhaust system of the present invention the (a) NH ₃ gas, in particular at low temperatures, supplying immediately upstream of the first selective catalytic reduction catalyst, and / or (b) in particular exhaust It has been found that when the gas temperature is relatively low, further improvement can be achieved by heating the exhaust gas from the exhaust control device for oxidizing carbon monoxide (CO) and / or hydrocarbons (HC). Exhaust system of the present invention can provide a transient FTP test cycle (transient FTP test cycle) under> 95% No _x conversion, which is a diesel engine meets emission standards and fuel economy targets for future Will make it possible.

The present invention further provides a vehicle. The vehicle of the present invention comprises a diesel engine and an exhaust system according to the present invention.

The present invention also relates to a method of treating exhaust gas generated by a diesel engine. The method comprises passing the exhaust gas produced by the diesel engine through an exhaust system, particularly the exhaust system according to the invention.

1 to 5 are schematic views of an aspect of the exhaust system according to the present invention.
Exhaust gas (1) from a turbocharger of a diesel engine shows an exhaust system in which an outlet flows into an oxidation catalyst (10) which can be a diesel oxidation catalyst (DOC) or a cold start concept (dCSC ^{TM) catalyst.} The exhaust gas (2) outlet from the oxidation catalyst flows through a conduit to the first selective catalytic reduction catalyst, which is the selective catalytic reduction filter catalyst (40). The sideflow NH ₃ feeder (20) _{can introduce the gaseous NH 3} into the conduit. The normal urea feeder (25) is also located in the conduit. Both the sideflow NH ₃ feeder (20) and the urea feeder (25) are upstream of the mixer (30). The mixer is adjacent to the inlet surface of the selective catalytic reduction filter catalyst (SCR-DPF) (40). A second selective catalytic reduction (SCR) catalyst (50). The SCR-DPF (40) and SCR catalyst (50) are tightly coupled and can be placed in the same container (60). After that, the exhaust gas from the outlet of the SCR catalyst (50) may be sent to an optional ammonia slip catalyst (70). The same exhaust system as the exhaust system shown in FIG. 1 is shown, except that the oxidation catalyst (10) of FIG. 1 is replaced by a catalyzed suit filter (80). The first SCR catalyst has a flow-through substrate. An exhaust system similar to the exhaust system of FIG. 2 is shown except that an oxidation catalyst (10) is present in addition to the catalyzed soot filter (80). The oxidation catalyst can be a diesel oxidation catalyst (DOC) or a cold start concept (dCSC ^TM ) catalyst. Is a schematic diagram showing a side flow NH ₃ supply body unit. Exhaust gas from the diesel engine flows from the exhaust manifold (5) to the turbocharger (15) in the exhaust system. Bypass (35) allows the part of the exhaust gas (3) enters the device for side flow NH ₃ supply. The device may optionally include a catalyzed soot filter (45). The sideflow NH ₃ feeder (20) is a normal urea feeder (55) and a urea hydrolysis catalyst (65) for producing _{NH 3} introduced from the turbocharger (15) into the main exhaust gas stream (1). ) Is included. An exhaust system similar to the exhaust system shown in FIG. 1 is shown. The oxidation catalyst (10) is a diesel oxidation catalyst (DOC), a catalyzed suit filter (CSF), a cold start concept (dCSC ^TM ) catalyst, or a combination of a diesel oxidation catalyst (DOC) and a catalyzed suit filter (CSF). There may be. The exhaust system may _{include an electric heater (75) in addition to or as an alternative to the sideflow NH 3} feeder (20), which heats the exhaust gas emitted from the oxidation catalyst (10). Can be used to 6 is a histogram showing the percentage of Nox conversion in the heavy duty transient FTP cycle of Examples 1 and 2.

Hereinafter, the present invention will be further described. The following sections relate to the various parts of the exhaust system, each part is defined in more detail, and also relates to the vehicles and methods of the present invention. Each part or aspect of the invention so defined may be combined with other parts or aspects of the invention unless the opposite is explicitly stated. In particular, any feature that is shown to be preferred or advantageous may be combined with other features that are shown to be preferred or advantageous.

Emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) This emission control device oxidizes carbon monoxide (CO) and / or hydrocarbon (HC), preferably CO and HC. Suitable for The emission control device is also suitable for oxidizing nitric oxide (NO) to nitrogen dioxide (NO _2).

Emission control devices for oxidizing carbon monoxide (CO) and / or hydrocarbons (HC)
(I) Diesel oxidation catalyst (DOC);
(Ii) Catalyzed suit filter (CSF);
(Iii) Cold start concept (dCSC ^TM ) catalyst;
(Iv) Diesel Oxidation Catalyst (DOC) and Catalyzed Suit Filter (CSF); and (v) Cold Start Concept (dCSC ^TM ) Catalyst and Catalyzed Suit Filter (CSF)
Can be selected from the group consisting of.

When the emission control device is a diesel oxidation catalyst (DOC) and a catalyzed soot filter (CSF), the DOC is preferably upstream of the CSF, preferably immediately upstream. Therefore, the outlet of the DOC is connected to the inlet of the CSF (eg, fluid connection by an exhaust gas conduit).

When the emission controller is a cold start concept (dCSC ^TM ) catalyst and a catalyzed suit filter (CSF), the cold start concept catalyst is preferably upstream, preferably immediately upstream of the CSF. Therefore, the outlet of the cold start concept catalyst is connected to the inlet of the CSF (eg, fluid connection by an exhaust gas conduit).

It is preferable when the emission control device is either (i) a diesel oxidation catalyst (DOC) and a catalyzed suit filter (CSF), or (ii) a cold start concept (dCSC ^TM ) catalyst and a catalyzed suit filter (CSF). DOC and CSF or cold start concept catalyst and CSF are tightly coupled. This is because the distance between the outlet end of the diesel oxidation catalyst or cold start concept catalyst and the inlet end of the catalyzed soot filter is 1.0 mm to 300 mm, preferably 3 mm to 200 mm, more preferably 5 mm to 150 mm (eg 8 mm to 100 mm). ), For example, 10 mm to 80 mm (for example, 12 mm to 70 mm), and even more preferably 15 mm to 50 mm. Means that This is advantageous for heat conduction and space saving.

Emission control devices are (i) a catalyzed soot filter (CSF), (ii) a cold start concept (dCSC ^TM ) catalyst having a filtering substrate, (iii) a diesel oxidation catalyst (DOC) and a catalyzed soot filter (CSF), (Iv) When either a cold start concept (dCSC ^TM ) catalyst or a catalyzed soot filter (CSF), the first selective catalytic reduction catalyst preferably has a flow-through substrate.

When the emission control device is either (i) a diesel oxidation catalyst (DOC) or (ii) a cold start concept (dCSC ^TM ) catalyst having a flow-through substrate, the first selective catalytic reduction catalyst is a filtering group. It preferably has a material (ie, the first SCR catalyst is SCR-DPF).

The exhaust system of the present invention usually preferably comprises a single filtering substrate.

The inlet of the exhaust controller is usually connected to a turbocharger (eg, fluid connection), preferably directly fluid connection. Therefore, the main exhaust gas flow moves from the diesel engine through the turbocharger to the emission control device.

Typically, the diesel oxidation catalyst (DOC) and / or the catalyzed suit filter (CSF) each comprises a catalytic composition disposed or supported on a substrate. The catalyst composition comprises platinum (Pt), palladium (Pd) and a platinum group metal (PGM) selected from combinations thereof.

When the emission control device is a diesel oxidation catalyst and / or a catalyzed suit filter, the (each) catalyst composition independently further comprises at least one carrier material. The carrier material (each) may independently contain or consist essentially of a refractory oxide.

The (each) refractory oxide typically consists of alumina, silica, titania, zirconia, ceria and a mixture or composite oxide of these (eg, a mixture or composite oxide of two or more of these). Selected more independently. For example, fire resistant oxides include alumina, silica, titania, zirconia, ceria, silica-alumina, titania-alumina, zirconia-alumina, ceria-alumina, titania-silica, zirconia-silica, zirconia-titania, ceria-zirconia and It can be selected from the group consisting of alumina-magnesium oxide. Each refractory oxide is preferably selected independently from the group consisting of alumina, silica, silica-alumina, ceria-alumina and ceria-zirconia. More preferably, the (each) refractory oxide is independently selected from the group consisting of alumina and silica-alumina.

Each platinum group metal (PGM) is typically placed or carried on a carrier material. The PGM may be placed directly on top of the carrier material or may be supported directly by the carrier material. For example, platinum and / or palladium can be dispersed on the carrier material.

When the emission control device is a diesel oxidation catalyst and / or a catalyzed soot filter, the platinum group metal (PGM) of each catalyst composition is preferably platinum (Pt) and a combination of platinum (Pt) and palladium (Pd). Is selected. The platinum group metal (PGM) of each catalyst composition is preferably a combination of platinum (Pt) and palladium (Pd).

When the platinum group metal (PGM) is a combination of platinum (Pt) and palladium (Pd), individual particles of platinum and palladium may be present, which may be separated or mixed. , Or platinum and palladium are in the form of alloys, preferably binary metal alloys.

Diesel oxidation catalysts can usually have a total charge of 20 to 200 g ft- ³ , preferably 25 to 175 g ft- ^{3 and} more preferably 30 to 160 g ft- ³ platinum group metals.

The catalyzed soot filter can have a total packing of 0.5 to 10 g ft ^-3 , preferably 1 to 7.5 g ft ^-3 , more preferably 4 to 6 g ft ^-3 platinum group metals.

The diesel oxidation catalyst and / or the catalyzed suit filter each independently have a ratio of total mass of platinum to total mass of palladium of 5: 1 to 1: 5 (eg 3: 1 to 1: 3), eg 2: 1. It may contain platinum in a ratio of 1: 2. The total mass of platinum is preferably greater than the total mass of palladium. The ratio of total mass of platinum to total mass of palladium is preferably 5: 1 to 1.1: 1 (eg 4: 1 to 7: 6), for example 3: 1 to 1.25: 1 (eg 2.5). 1 to 1.25: 1).

The diesel oxidation catalyst and / or the catalyzed soot filter each independently have a total amount of 0.1 to 4.5 g in ^-3 (eg, 0.25 to 4.0 g in ^-3 ), preferably 0.5 to 3.0 g. It ^{contains in -3} , more preferably 0.6 to 2.5 g in ^-3 (eg 0.75 to 1.5 g in ^-3 ) of carrier material.

If the emission control device is a diesel oxidation catalyst, the diesel oxidation catalyst may include a downstream area. The downstream area is located at the outlet edge of the substrate. The downstream area may be configured to perform certain functions, such as capturing and / or collecting volatile platinum, or oxidizing nitric oxide (NO) to nitrogen dioxide (NO _2).

The downstream area may have a composition for supplementing and / or collecting volatile platinum. Such areas reduce or prevent volatilized platinum from condensing on the downstream selective catalytic reduction catalyst. Compositions for supplementing and / or collecting volatile platinum include International Publication No. 2013/088313, International Publication No. 2013/088132, International Publication No. 2013/088128, International Publication No. 2013/050784, and PCT International. It is disclosed in Patent Application GB 2016/050285.

The downstream area may contain carrier materials including platinum, manganese or oxides thereof, and alumina. Platinum and manganese or oxides thereof are preferably placed or carried on a carrier material. It has been found that excellent NO oxidation activity can be obtained when manganese or an oxide thereof is contained downstream.

If the downstream area contains manganese, the carrier material preferably comprises or consists essentially of silica alumina or silica-doped alumina.

If the downstream area contains manganese, the downstream area may further contain palladium, eg, palladium placed or carried on a carrier material. Downstream, the weight ratio of platinum to palladium is ≧ 2: 1 (eg Pt: Pd 1: 0 to 2: 1), more preferably ≧ 4: 1 (eg Pt: Pd 1: 0 to 4: 1). Can be.

The diesel oxidation catalyst may further comprise a hydrocarbon adsorbent. The hydrocarbon adsorbent can be a zeolite. Zeolites are preferably not transition metal exchange zeolites.

The zeolite is preferably a medium-pore zeolite (for example, a zeolite having a maximum ring size of 10 tetrahedral atoms) or a large-pore zeolite (for example, a zeolite having a maximum ring size of 12 tetrahedral atoms). It may be preferable that the zeolite is not a small pore zeolite (eg, a zeolite having a maximum ring size of 8 tetrahedral atoms).

Examples of suitable zeolites or types of zeolites are fujasite, clinoptilolite, mordenite, silicalite, ferrierite, X-type zeolite, Y-type zeolite, ultra-stable Y-type zeolite, AEI-type zeolite, ZSM-5 type. Zeolites, ZSM-12 type zeolite, ZSM-20 type zeolite, ZSM-34 type zeolite, CHA type zeolite, SSZ-3 type zeolite, SAPO-5 type zeolite, offletite, beta zeolite or CHA type copper zeolite can be mentioned. Zeolites are preferably ZSM-5 type, beta zeolite or Y type zeolite.

When the diesel oxidation catalyst contains a hydrocarbon adsorbent, the total amount of the hydrocarbon adsorbent is generally 0.05 to 3.00 g in ^-3 , especially 0.10 to 2.00 g in ^-3 , more specifically. Is 0.2 to 1.0 g in ^-3 . For example, the total amount of hydrocarbon adsorbent can be 0.8 to 1.75 g in ^-3 , for example 1.0 to 1.5 g in ^-3 .

The advantage of including a diesel oxidation catalyst (DOC) in the exhaust system is that the amount of N _{2 O} produced by DOC is minimal.

The advantage of including a catalyzed soot filter (CSF) in the exhaust system is that the CSF removes the soot (ie, particulate matter). The CSF can be involved in soot removal alone (eg, if the first SCR catalyst has a flow-through substrate), or can be involved in the overall soot removal of the exhaust system (eg, first SCR). When the catalyst is SCR-DPF).

The emission control device may include a cold start concept (dCSC ^TM ) catalyst (alone or with a catalyzed suit filter (CSF)). A cold start concept catalyst (hereinafter referred to as "cold start catalyst") can store _{NO x at a relatively low temperature and a high storage efficiency as compared with DOC and CSF.} Cold start catalyst, the (unlike lean NO _x trap that releases the composition of the exhaust gas becomes "rich" NO _x (LNT), or NO _x storage catalyst (NSC)) reaches a specific temperature NO _x discharge.

The advantage of the cold start catalyst is when the temperature of the exhaust system is relatively low so that the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst _{do not reach the effective operating temperature for reducing NO x.} The _{point is that NO x} can be stored in. _{The NO x} release temperature of the cold start catalyst may be equal to or higher than the effective operating temperature of the first selective catalytic reduction catalyst and / or the second selective catalytic reduction catalyst. This means that If a first selective catalytic reduction catalyst and / or the second selective catalytic reduction catalyst effectively exhaust system to a temperature capable of reducing the NO _x is reached, cold start catalyst capable of releasing NO _x To do.

Typically, the cold start catalyst comprises a catalytic material placed or carried on a substrate. The catalytic material may include or consist essentially of a molecular sieve catalyst. Molecular receive catalysts include or consist essentially of precious metals and molecular sieves. Molecular sieve catalysts can be prepared according to the methods described in WO 2012/166868.

Molecular receive catalysts generally include or consist essentially of precious metal exchange molecular sieves.

The noble metal is usually selected from the group consisting of palladium (Pd), platinum (Pt), rhodium (Rh) and mixtures of two or more of these. The noble metal is more preferably selected from palladium (Pd), platinum (Pt) and mixtures thereof.

The noble metal generally comprises or preferably comprises palladium (Pd) and a second metal optionally selected from the group consisting of platinum (Pt) and rhodium (Rh). Even more preferably, the noble metal comprises or consists of palladium (Pd) and optionally platinum (Pt). More preferably, the molecular sieve catalyst contains palladium as the only noble metal.

If the noble metal contains or consists of palladium (Pd) and a second metal, the mass ratio of palladium (Pd) to the second metal is> 1: 1. More preferably, the mass ratio of palladium (Pd) to the second metal is> 1: 1 and the molar ratio of palladium (Pd) to the second metal is also> 1: 1.

The molecular sieve catalyst may further contain a base metal. Thus, the molecular sieve catalyst may or may optionally contain a noble metal, a molecular sieve, and optionally a base metal, or may consist essentially of these. The molecular sieve catalyst may include or consist essentially of precious metal exchange molecular sieves and base metal exchange molecular sieves.

Base metals include iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni), zinc (Zn) and tin (Sn), and two or more of these. It can be selected from the group consisting of mixtures. The base metal is preferably selected from the group consisting of iron, copper and cobalt, more preferably iron and copper. Even more preferably, the base metal is iron.

Alternatively, the molecular sieve catalyst may be a base metal such as iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni), zinc (Zn) and tin (Sn). In addition, it may be substantially free of base metals selected from the group consisting of a mixture of two or more of these. Therefore, the zeolite catalyst may not contain base metals.

In general, it is preferable that the molecular sieve catalyst does not contain a base metal.

Molecular sieves are usually composed of aluminum, silicon, and / or phosphorus. Molecular sieves generally have a three-dimensional structure (eg, skeleton) of _{SiO 4} , AlO ₄ and / or PO ₄ that are bonded by sharing oxygen atoms. Molecular sieves can have an anionic skeleton. The charge of the anionic skeleton can be offset by cations such as alkali and / or alkaline earth elements (eg Na, K, Mg, Ca, Sr and Ba) cations, ammonium cations and / or protons.

Typically, the molecular sieve has an aluminosilicate scaffold, an aluminophosphate scaffold or a silico-aluminophosphate scaffold. The molecular sieve may have an aluminosilicate backbone or an aluminophosphate backbone. The molecular sieve preferably has an aluminosilicate skeleton or an aluminophosphate skeleton. More preferably, the molecular sieve has an aluminosilicate skeleton.

If the molecular sieve has an aluminosilicate backbone, it is preferably a zeolite.

In general, a molecular sieve is a precious metal exchange molecular sieve (eg, a precious metal exchange molecular sieve having an aluminosilicate or aluminophosphate skeleton). The noble metal may be present on the outer surface of the molecular sieve or at an extra skeletal site within the channel, cavity or cage of the molecular sieve.

Molecular sieve catalysts are generally at least 1% by weight (eg, by replacement such as located inside the pores of the molecular sieve), preferably at least 5% by weight, more preferably. Has at least 10% by weight, for example at least 25% by weight, even more preferably at least 50% by weight.

Molecular sheaves include small pore molecular sieves (ie, molecular sieves with a maximum ring size of 8 tetrahedral atoms), medium pore molecular sieves (ie, molecular sieves with a maximum ring size of 10 tetrahedral atoms), and large. It can be selected from pore molecular sieves (ie, molecular sieves having tetrahedral atoms with a maximum ring size of 12). The molecular sieve is more preferably selected from the small pore molecular sieve and the medium pore molecular sieve.

In an embodiment of the first molecular sieve catalyst, the molecular sieve is a small pore molecular sieve. The small pore molecular sieves are preferably 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, and any of these. It has a skeletal structure represented by a skeletal type code (FTC) selected from the group consisting of two or more kinds of mixtures or intergrowths. The intergrowth is preferably selected from KFI-SIV, ITE-RTH, AEW-UEI, AEI-CHA, and AEI-SAV. The small pore molecular sieve more preferably has a skeletal structure with an AEI, CHA or AEI-CHA intergrowth FTC. The small pore molecular sieves even more preferably have a skeletal structure with an AEI or CHA, especially an AEI FTC.

The small pore molecular sieve preferably has an aluminosilicate skeleton or a silico-aluminophosphate skeleton. The small pore molecular sieve more preferably has an aluminosilicate skeleton, especially if the small pore molecular sieve has a skeletal structure represented by an AEI, CHA or AEI-CHA intergrowth FTC, particularly an AEI or CHA FTC. ..

In a second molecular sheave catalyst embodiment, the molecular sieve is from AEI, MFI, EMT, ERI, MOR, FER, BEA, FAU, CHA, LEV, MWW, CON and EUO, and a mixture of two or more of these. It has a skeletal structure represented by FTC selected from the group consisting of.

In the third molecular sheave catalyst embodiment, the molecularity is a medium pore molecular sieve. The medium pore molecular sieve has a skeletal structure represented by FTC, preferably selected from the group consisting of MFI, FER, MWW and EUO, more preferably MFI.

In a fourth molecular sieve catalyst embodiment, the molecular sieve is a large pore molecular sieve. The large pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of CON, BEA, FAU, MOR and EMT, more preferably FTC which is BEA.

In each of the first to fourth molecular sheave catalyst embodiments, the molecular sieve preferably has an aluminosilicate skeleton (eg, the molecular sieve is a zeolite). Each of the above three-letter codes represents a skeletal type according to the "IUPAC Committee on Zeolite Naming" and / or the "Structural Committee of the International Zeolite Society".

Molecular sieves typically have a silica to alumina molar ratio (SAR) of 10 to 200 (eg, 10 to 40), such as 10 to 100, more preferably 15 to 80 (eg, 15 to 30). SAR generally relates to molecules having an aluminosilicate backbone (eg, zeolite) or a silico-aluminophosphate backbone, preferably an aluminosilicate backbone (eg, zeolite).

Molecular sieve catalysts in embodiments of the first, third and fourth molecular sieve catalysts (and some skeletal types of embodiments of the second molecular sieve catalyst) range ^{from 750 cm -1} to 1050 cm ^-1. It may have an infrared spectrum with a characteristic absorption peak (in addition to the absorption peak of the molecular sieve itself). Preferably, characteristic absorption peaks in the range of 1000 cm ^-1 from 800 cm ^-1, more preferably in the range of 975cm ^-1 from 850 cm ^-1.

In general, cold start catalysts have a total charge of noble metal (ie, especially the molecular sieve catalyst in the first region) of ≧ 1 g ft ^-3 , preferably> 1 g ft ^-3 , more preferably> 2 g ft ^-3 . is there.

Cold start catalysts typically have a total charge of noble metal (ie, molecular sieve catalyst) of 1 to 250 g ft ^-3 , preferably 5 to 150 g ft ^-3 , more preferably 10 to 100 g ft ^-3 . ..

In general, the (each) substrate (ie, the substrate of the emission control device) is a monolith (also referred to herein as a substrate monolith). Such monoliths are well known in the art.

The substrate, especially the substrate monolith, preferably has a diameter of ≧ 7 inches (eg ≧ 17.8 cm). Such substrate monoliths tend to be used in large diesel applications.

Typically, the diesel oxidation catalyst comprises a substrate that is a flow-through substrate (eg, a flow-through monolith). Catalytic soot filters include substrates that are filtering substrates (eg, filtering monoliths). Cold start catalysts include substrates that are flow-through substrates (eg, flow-through monoliths) or filtering substrates (eg, filtering monoliths). The cold start catalyst preferably contains a base material which is a flow-through base material.

Flow-through monoliths typically include honeycomb monoliths (eg, metal or ceramic honeycomb monoliths) that have multiple channels that are open at both ends and extend through them.

The filtering monolith may be a wall flow type filter base material monolith. Wall-flow filter substrate monoliths typically include multiple inlet channels and multiple outlet channels, with the inlet channel opening at the upstream end (ie, the exhaust gas inlet side) and the downstream end (ie, the exhaust gas outlet side). ), The outlet channels are embolized or sealed at the upstream end, open at the downstream end, and each inlet channel is exited by a wall (eg, a wall with a porous structure). Separated from the channel.

In a wall-flow filter substrate monolith, each inlet channel is alternately separated from the outlet channel by a wall (eg, of porous structure) and vice versa. The inlet and outlet channels are preferably arranged in a honeycomb structure. In the presence of a honeycomb structure, channels perpendicular and laterally adjacent to the inlet channel are embolized at the upstream end and vice versa (ie, channels perpendicular and laterally adjacent to the exit channel are downstream ends. (Imbolized with) is preferable. From either end, the ends of the channels that are alternately embolized and opened give the appearance of a chess board.

In general, the substrate can have a tubular, fibrous or granular form. Examples of suitable supporting substrates are monolith honeycomb cordierite type substrate, monolith honeycomb SiC type substrate, layered fiber or knitted fabric type substrate, foam type substrate, cross flow type substrate. Examples include materials, metal wire mesh type base materials, metal porous type base materials, and ceramic particle type base materials.

Typically, diesel oxidation catalysts and / or catalyzed soot filters and / or cold start catalysts are substantially free of rhodium and / or oxides of alkali metals, alkaline earth metals and / or rare earth metals, substantially free of either or essentially nO _x storage component consisting including carbonates or hydroxides. More preferably, the diesel oxidation catalyst and / or the catalyzed soot filter and / or the cold start catalyst is rhodium-free and / or an oxide, carbonate or water of an alkali metal, alkaline earth metal and / or rare earth metal. It contains oxides or does not contain _{NO x storage components consisting essentially of these.}

It may be preferable that the molecular sieve catalyst is substantially free of platinum. The molecular sieve catalyst is more preferably platinum free.

Injector for Introducing Ammonia Precursor into Exhaust Gas The exhaust system of the present invention includes an injector for introducing an ammonia precursor into an exhaust gas. To avoid doubt, the injector for introducing an ammonia precursor into the exhaust gas is not a means for introducing ammonia gas into the exhaust gas, as described below (eg, it contains components different from this means). ).

The injector is typically a liquid injector suitable for introducing a solution containing an ammonia precursor into the exhaust gas.

The ammonia precursor is preferably urea or ammonium formate, more preferably urea. Urea supply systems for SCR catalysts are known in the art.

The injector generally sprays the ammonia precursor or the solution containing the ammonia precursor when injecting into the exhaust gas, for example by spraying the ammonia precursor or a solution containing the ammonia precursor. The injector can be an airless injector or an air assist injector.

The injector is configured to introduce an ammonia precursor into the exhaust gas upstream of the selective catalytic reduction filter catalyst. The injector is preferably configured to controlfully introduce a constant amount of ammonia precursor into the exhaust gas upstream of the selective catalytic reduction filter catalyst. _{More preferably, the injector has an ammonia to NO x} molar ratio (ANR) of 0.7 to 1.3 (eg 0.9 to 1.2), eg 1.0 to 1.2 (eg about 1: 1). A constant amount of ammonia precursor is controlledly introduced into the exhaust gas upstream of the selective catalytic reduction filter catalyst.

The injector for introducing the ammonia precursor into the exhaust gas is downstream of the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC), preferably downstream of the outlet of the device ( For example located). If the emission controller is (i) a diesel oxidation catalyst (DOC) and a catalyzed suit filter (CSF) or (ii) a cold start concept (dCSC ^TM ) catalyst and a catalyzed suit filter (CSF), the injector is preferred. , Downstream of the CSF exit (eg located).

The emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) is typically connected to the inlet of the selective catalytic reduction filter catalyst by an exhaust gas conduit, preferably a fluid connection. Has an exit that has been. The injector for introducing the ammonia precursor into the exhaust gas is preferably located between the outlet of the emission control device and the inlet of the first selective catalytic reduction catalyst. The injector is preferably connected to the exhaust gas conduit between the outlet of the emission control device and the inlet of the first selective catalytic reduction catalyst.

Generally, the injector for introducing the ammonia precursor into the exhaust gas is connected to the ammonia precursor storage tank, preferably fluid-connected. Therefore, the exhaust system of the present invention may further include an ammonia precursor storage tank.

The injector for introducing the ammonia precursor into the exhaust gas may be electrically connected to the engine management system. The engine management system causes the injector to inject the ammonia precursor into the exhaust gas when the temperature of the exhaust gas is ≧ T ₁ (where T ₁ is 200 ° C., preferably 215 ° C., more preferably 230 ° C.). It may be configured. The engine management system causes the injector to inject an ammonia precursor into the exhaust gas when the exhaust gas temperature is ≧ T ₁ and the exhaust gas molar ANR is 0.7, preferably <0.9. It is particularly preferable to be configured in.

The engine management system and / or the injector for introducing the ammonia precursor into the exhaust gas is electrically connected to a temperature sensor located upstream, preferably immediately upstream of the selective catalytic reduction filter catalyst (eg thermocouple). It may have been done. This temperature sensor is located downstream of the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbons (HC). Temperature sensors are suitable for determining T _1.

Additional or alternative, the injector for introducing the engine management system and / or the ammonia precursor into the exhaust gas is a NO _x sensor located upstream, preferably immediately upstream of the first selective catalytic reduction catalyst. It may be electrically connected. The Nox _x sensor is preferably located downstream of the injector for introducing the ammonia precursor into the exhaust gas.

The exhaust system may further include a mixer, which is located upstream of the first selective catalytic reduction catalyst and downstream of the injector for introducing the ammonia precursor into the exhaust (eg, in the exhaust conduit). To do).

First Selective Catalytic Reduction (SCR) Catalyst The exhaust system of the present invention comprises a first selective catalytic reduction catalyst. The first SCR catalyst is downstream (eg, located) of the injector for introducing the ammonia precursor into the exhaust gas. The first SCR catalyst is upstream of the second selective catalytic reduction (SCR) catalyst.

The first SCR catalyst comprises a substrate and a first SCR catalyst composition. The base material is a flow-through base material or a filtering base material. The term "first" in the expression "first selective catalytic reduction composition" is used to describe a composition from another selective catalytic reduction composition present in the exhaust system.

If the first SCR catalyst has a flow-through substrate, the substrate can contain a first SCR catalyst composition (ie, the first SCR catalyst is obtained by extrusion) or a first SCR catalyst. The composition can be placed or carried on the substrate (ie, the first SCR catalyst composition is applied onto the substrate by the washcoat method). The first SCR catalyst composition is preferably placed or supported on a substrate.

In general, the first SCR catalyst is preferably a filtering substrate. When the first SCR catalyst has a filtering substrate, it is a selective catalytic reduction filter catalyst, abbreviated herein as "SCR-DPF". The SCR-DPF comprises a filtering substrate and a first selective catalytic reduction (SCR) composition.

The first selective catalytic reduction composition may include, or may consist essentially of, a metal oxide-based SCR catalyst formulation, a molecular sieve-based SCR catalyst formulation, or a mixture thereof. Such SCR catalyst formulations are known in the art.

The first selective catalytic reduction composition may include, or may consist essentially of, a metal oxide-based SCR catalyst formulation. The metal oxide-based SCR catalyst formulation contains vanadium or tungsten supported on a refractory oxide or a mixture thereof. The refractory oxide can be selected from the group consisting of alumina, silica, titania, zirconia, ceria and combinations thereof.

The metal oxide-based SCR catalyst formulation includes titania (eg TiO ₂ ), ceria (eg CeO ₂ ) and a mixture of cerium and zirconium or a composite oxide (eg Ce _x Zr _(1-x) O ₂ , in the formula, x. = 0.1 to 0.9, preferably an oxide of vanadium supported on a refractory oxide selected from the group consisting of x = 0.2 to 0.5) (e.g. _V 2 _{O 5)} and / or It may be preferable that it contains or consists essentially of an oxide of tungsten (eg WO _3).

When the fire resistant oxide is titania (eg, TiO ₂ ), the concentration of vanadium oxide is preferably 0.5 to 6% by weight (eg, a metal oxide-based SCR formulation) and / or tungsten. The concentration of oxides (eg WO ₃ ) is 5 to 20% by weight. More preferably, an oxide of vanadium (e.g. _V 2 _{O 5)} and oxides of tungsten (eg WO ₃₎ is supported on titania (e.g. TiO _2).

When the refractory oxide is ceria (eg CeO ₂ ), the concentration of vanadium oxide is preferably 0.1 to 9% by weight (eg, metal oxide-based SCR formulations) and / or tungsten. The concentration of oxides (eg WO ₃ ) of is 0.1 to 9% by weight.

Generally, metal oxide-based SCR catalyst formulations, titania (e.g., TiO ₂₎ oxides of vanadium carried on (e.g. _V 2 _{O 5)} and, optionally, oxides of tungsten (eg WO ₃ ) Includes or consists essentially of these. Metal oxide-based SCR catalyst formulations, particularly when the metal oxide-based SCR catalyst formulation is disposed upstream of the copper-containing molecular sieve based SCR catalyst formulations, may result in significantly less N _{2 O} as a by-product Found.

The first selective catalytic reduction composition may include or may consist essentially of a molecular sieve SCR catalyst formulation. The molecular sieve-based SCR catalyst formulation optionally comprises a molecular sieve, which is a transition metal exchange molecular sieve. The SCR catalyst formulation preferably comprises a transition metal exchange molecular sieve.

In general, molecular sieve SCR catalyst formulations include aluminosilicate backbone (eg zeolite), aluminophosphate backbone (eg AlPO), silicoaluminophosphate backbone (eg SAPO), heteroatom-containing aluminosilicate backbone, heteroatom-containing aluminophosphate. It may include a molecular sieve having a backbone (eg, MeAlPO, where Me is a metal) or a heteroatom-containing silicoaluminosilicate backbone (eg, MeASPO, where Me is a metal). Heteroatoms (eg, in a heteroatom-containing backbone) include, for example, boron (B), gallium (Ga), titanium (Ti), zirconium (Zr), zinc (Zn), iron (Fe), vanadium (V), and It can be selected from the group consisting of any two or more combinations thereof. The heteroatom is preferably a metal (eg, each of the above heteroatom-containing skeletons may be a metal-containing skeleton).

The molecular sieve-based SCR catalyst formulation preferably comprises or consists essentially of a molecular sieve having an aluminosilicate backbone (eg, zeolite) or a silicoaluminophosphate backbone (eg, SAPO). More preferably, the molecular sieve has an aluminosilicate backbone (eg, zeolite).

If the molecular sieve has an aluminosilicate backbone (eg, the molecular sieve is a zeolite), the molecular sieve is typically 5 to 200 (eg, 10 to 200), preferably 10 to 100 (eg, 10 to 30 or 20). It has an 80), eg, 12 to 40, more preferably 15 to 30, silica to alumina molar ratio (SAR).

Molecular sieves are usually microporous. Microporous molecular sieves have pores with a diameter of less than 2 nm (eg according to the IUPAC definition of "microporous") [Pure & Appl. Chem., 66 (8), (1994), 1739-1758. )]reference).

Molecular receive SCR catalyst formulations include small pore molecular sieves (eg, molecular sieves having a maximum ring size of 8 tetrahedral atoms) and medium pore molecular sieves (eg, molecular sieves having a maximum ring size of 10 tetrahedral atoms). Sheaves) or large pore molecular sheaves (eg, molecular sheaves having tetrahedral atoms with a maximum ring size of 12) or a combination of two or more thereof may be included.

When the molecular sieve is a small pore molecular sieve, the small pore molecular sieve is 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, and a skeletal structure represented by a skeletal type code (FTC) selected from the group consisting of two or more kinds of mixtures or intergrowths thereof. The small pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. The small pore molecular sieve more preferably has a skeletal structure represented by FTC selected from the group consisting of CHA and AEI. The small pore molecular sieve may have a skeletal structure represented by FTC CHA. Small pore molecular sieves are available from FTC AEI. It may have a skeletal structure represented by. When the small pore molecular sieve is a zeolite, the small pore molecular sieve has a skeletal structure represented by FTC CHA and the zeolite can be a chabazite.

When the molecular sieve is a medium pore molecular sieve, the medium pore molecular sieve is 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 of two or more of these and / or a skeletal type code selected from the group of skeletal types consisting of intergrowths ( It may have a skeletal structure represented by FTC). The medium pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of FER, MEL, MFI and STT. The medium pore molecular sieve is more preferably selected from the group consisting of FER and MFI, and has a skeletal structure represented by FTC, which is MFI in particular. Zeolites can be ferrierite, silicalite or ZSM-5 if the medium pore molecular sieve is zeolite and has a backbone represented by FTC, FER or MFI.

When the molecular sieve is a large pore molecular sieve, the large pore molecular sieve is AFI, AFR, AFS, AHY, 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 two or more of these. It may have a skeletal structure represented by an Independent Code (FTC) selected from the group consisting of mixtures and / or intergrowths. The large pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of AFI, BEA, MAZ, MOR and OFF. Large pore molecular sieves have a skeletal structure represented by FTC, more preferably selected from the group consisting of BEA, MOR and MFI. If the large pore molecular sieve is a zeolite and has a backbone represented by FTC BEA, FAU or MOR, the zeolite can be beta zeolite, fujasite, zeolite Y, zeolite X or mordenite.

In general, the molecular sieve is preferably a small pore molecular sieve.

The molecular sieve-based SCR catalyst formulation preferably comprises a transition metal exchange molecular sieve. The transition metal can be selected from the group consisting of cobalt, copper, iron, manganese, nickel, palladium, platinum, ruthenium and rhenium. The transition metal is preferably selected from the group consisting of copper and iron.

The transition metal may be iron. The advantage of SCR catalyst formulations containing iron exchange molecular sieves is that such formulations have superior NO _x reduction activity at temperatures higher than, for example, copper exchange molecular sieves. Iron-exchanged molecular sieve may also generate N _{2 O} of (compared to other types of SCR catalyst formulation) minimum amount.

The transition metal may be copper. An advantage of the SCR catalyst formulations containing copper-exchanged molecular sieve (sometimes be superior low temperature iNO _x reduction activity of example, iron-exchanged molecular sieve) in which to have excellent low temperature iNO _x reduction activity.

The transition metal may be present on the outer surface of the molecular sieve or at an extra skeletal site within the channel, cavity or cage of the molecular sieve.

Typically, the transition metal exchange molecular sieve comprises an amount of 0.10 to 10% by weight, preferably 0.2 to 5% by weight, of the transition metal exchange molecule.

The first selective catalytic reduction catalyst generally comprises a first selective catalytic reduction composition of 0.5 to 4.0 g in ^-3 , preferably 1.0 to 3.0 4.0 g in ^-3 . Included in full concentration.

The first SCR catalyst composition may preferably contain a mixture of a metal oxide-based SCR catalyst formulation and a molecular sieve-based SCR catalyst formulation. (A) The metal oxide-based SCR catalyst formulation comprises vanadium oxide (for example, V ₂ O _{5 ) supported on titania (for example, TiO 2} ) and optionally tungsten oxide (for example, WO ₃ ). (B) The molecular sieve-based SCR catalyst formulation preferably comprises a transition metal exchange molecular sieve. More preferably, the transition metal of the transition metal exchange molecular sieve is iron. Zeolites preferably have a skeletal structure represented by MFI.

When the first SCR catalyst is an SCR-DPF, the filtering substrate is preferably a wall flow filter substrate monolith as described above in connection with, for example, a catalytic soot filter.

Wall flow filter substrate monoliths (eg, SCR-DPF) typically have cell densities of 60 to 400 cells / square inch (cpsi). The cell density of the wall flow filter base material monolith is preferably 100 to 350 cpsi, more preferably 200 to 300 cpsi.

The wall flow filter substrate monolith can have a wall thickness (eg, average inner wall thickness) of 0.20 to 0.50 mm, preferably 0.25 to 0.35 mm (eg, about 0.30 mm).

In general, an uncoated wall flow filter substrate monolith has a porosity of 50-80%, preferably 55-75%, more preferably 60-70%.

The uncoated wall flow filter substrate monolith typically has an average pore diameter of at least 5 μm. The average pore diameter is preferably 10 to 40 μm, for example 15 to 35 μm, more preferably 20 to 30 μm.

The wall flow filter substrate can have a symmetric cell design or an asymmetric cell design.

Generally, in the case of SCR-DPF, the first selective catalytic reduction composition is placed within the wall of the wall flow filter substrate monolith. In addition, the first selective catalytic reduction composition may be placed on the wall of the inlet channel and / or the wall of the exit channel.

Second Selective Catalytic Reduction (SCR) Catalyst The exhaust system of the present invention comprises a second selective catalytic reduction (SCR) catalyst. The second SCR catalyst is downstream, preferably immediately downstream of the first SCR catalyst. Therefore, the outlet of the first SCR catalyst is usually connected (eg, fluid connection) to the inlet of the second SCR catalyst.

The first SCR catalyst and the second SCR catalyst may be tightly coupled. The distance between the outlet of the first SCR catalyst and the second SCR catalyst is 1.0 mm to 300 mm, preferably 3 mm to 200 mm, more preferably 5 mm to 150 mm (for example, 8 mm to 100 mm), for example, 10 mm to 80 mm (for example, 12 mm). From 70 mm), even more preferably from 15 mm to 50 mm. This is advantageous for heat conduction and space saving.

The second SCR catalyst comprises a flow-through substrate and a second selective catalytic reduction (SCR) composition. The term "second" in the expression "second selective catalytic reduction composition" is used to describe a composition from another selective catalytic reduction composition present in the exhaust system. The second SCR catalyst does not need to have more than one selective catalytic reduction composition.

The second selective catalytic reduction composition may include, or may consist essentially of, a metal oxide-based SCR catalyst formulation, a molecular sieve-based SCR catalyst formulation, or a mixture thereof. The second selective catalytic reduction composition may be the same as or different from the first selective catalytic reduction composition.

The second selective catalytic reduction composition may include, or may consist essentially of, a metal oxide-based SCR catalyst formulation. The metal oxide-based SCR catalyst formulation contains vanadium or tungsten supported on a refractory oxide or a mixture thereof. The refractory oxide can be selected from the group consisting of alumina, silica, titania, zirconia, ceria and combinations thereof.

The metal oxide-based SCR catalyst formulation includes titania (eg TiO ₂ ), ceria (eg CeO ₂ ) and a mixture of cerium and zirconium or a composite oxide (eg Ce _x Zr _(1-x) O ₂ , in the formula, x. = 0.1 to 0.9, preferably an oxide of vanadium supported on a refractory oxide selected from the group consisting of x = 0.2 to 0.5) (e.g. _V 2 _{O 5)} and / or It may be preferable that it contains or consists essentially of an oxide of tungsten (eg WO _3).

When the fire resistant oxide is titania (eg, TiO ₂ ), the concentration of vanadium oxide is preferably 0.5 to 6% by weight (eg, a metal oxide-based SCR formulation) and / or tungsten. The concentration of oxides (eg WO ₃ ) is 5 to 20% by weight. More preferably, an oxide of vanadium (e.g. _V 2 _{O 5)} and oxides of tungsten (eg WO ₃₎ is supported on titania (e.g. TiO _2).

When the refractory oxide is ceria (eg CeO ₂ ), the concentration of vanadium oxide is preferably 0.1 to 9% by weight (eg, metal oxide-based SCR formulations) and / or tungsten. The concentration of oxides (eg WO ₃ ) of is 0.1 to 9% by weight.

Generally, metal oxide-based SCR catalyst formulations, titania (e.g., TiO ₂₎ oxides of vanadium carried on (e.g. _V 2 _{O 5)} and, optionally, oxides of tungsten (eg WO ₃ ) Includes or consists essentially of these. Metal oxide-based SCR catalyst formulation was found to produce significantly less N _{2 O} as a by-product.

The second selective catalytic reduction composition may include or may consist essentially of a molecular sieve SCR catalyst formulation. The molecular sieve-based SCR catalyst formulation optionally comprises a molecular sieve, which is a transition metal exchange molecular sieve. The SCR catalyst formulation preferably comprises a transition metal exchange molecular sieve.

In general, molecular sieve SCR catalyst formulations include aluminosilicate backbone (eg zeolite), aluminophosphate backbone (eg AlPO), silicoaluminophosphate backbone (eg SAPO), heteroatom-containing aluminosilicate backbone, heteroatom-containing aluminophosphate. It may include a molecular sieve having a backbone (eg, MeAlPO, where Me is a metal) or a heteroatom-containing silicoaluminosilicate backbone (eg, MeASPO, where Me is a metal). Heteroatoms (eg, in a heteroatom-containing backbone) include, for example, boron (B), gallium (Ga), titanium (Ti), zirconium (Zr), zinc (Zn), iron (Fe), vanadium (V), and It can be selected from the group consisting of any two or more combinations of these. The heteroatom is preferably a metal (eg, each of the above heteroatom-containing skeletons may be a metal-containing skeleton).

The molecular sieve-based SCR catalyst formulation preferably comprises or consists essentially of a molecular sieve having an aluminosilicate backbone (eg, zeolite) or a silicoaluminophosphate backbone (eg, SAPO). More preferably, the molecular sieve has an aluminosilicate backbone (eg, zeolite).

If the molecular sieve has an aluminosilicate backbone (eg, the molecular sieve is a zeolite), the molecular sieve is typically 5 to 200 (eg, 10 to 200), preferably 10 to 100 (eg, 10 to 30 or 20). It has an 80), eg, 12 to 40, more preferably 15 to 30, silica to alumina molar ratio (SAR).

Molecular sieves are usually microporous. Microporous molecular sieves have pores with a diameter of less than 2 nm (eg according to the IUPAC definition of "microporous") [Pure & Appl. Chem., 66 (8), (1994), 1739-1758. )]reference).

Molecular receive SCR catalyst formulations include small pore molecular sieves (eg, molecular sieves having a maximum ring size of 8 tetrahedral atoms) and medium pore molecular sieves (eg, molecular sieves having a maximum ring size of 10 tetrahedral atoms). Sheaves) or large pore molecular sheaves (eg, molecular sheaves having tetrahedral atoms with a maximum ring size of 12) or a combination of two or more thereof may be included.

When the molecular sieve is a small pore molecular sieve, the small pore molecular sieve is 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, and a skeletal structure represented by a skeletal type code (FTC) selected from the group consisting of two or more kinds of mixtures or intergrowths thereof. The small pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE. The small pore molecular sieve more preferably has a skeletal structure represented by FTC selected from the group consisting of CHA and AEI. The small pore molecular sieve may have a skeletal structure represented by FTC CHA. The small pore molecular sieve may have a skeletal structure represented by FTC AEI. When the small pore molecular sieve is a zeolite, the small pore molecular sieve has a skeletal structure represented by FTC CHA and the zeolite can be a chabazite.

When the molecular sieve is a medium pore molecular sieve, the medium pore molecular sieve is 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 of two or more of these and / or a skeletal type code selected from the group of skeletal types consisting of intergrowths ( It may have a skeletal structure represented by FTC). The medium pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of FER, MEL, MFI and STT. The medium pore molecular sieve has a skeletal structure represented by FTC, which is more preferably selected from the group consisting of FER and MFI. Zeolites can be ferrierite, silicalite or ZSM-5 if the medium pore molecular sieve is zeolite and has a backbone represented by FTC, FER or MFI.

When the molecular sieve is a large pore molecular sieve, the large pore molecular sieve is AFI, AFR, AFS, AHY, 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 two or more of these. It may have a skeletal structure represented by a skeletal type code (FTC) selected from the group consisting of mixtures and / or intergrowths. The large pore molecular sieve preferably has a skeletal structure represented by FTC selected from the group consisting of AFI, BEA, MAZ, MOR and OFF. Large pore molecular sieves have a skeletal structure represented by FTC, more preferably selected from the group consisting of BEA, MOR and MFI. If the large pore molecular sieve is a zeolite and has a backbone represented by FTC BEA, FAU or MOR, the zeolite can be beta zeolite, fujasite, zeolite Y, zeolite X or mordenite.

In general, the molecular sieve is preferably a small pore molecular sieve.

The molecular sieve-based SCR catalyst formulation preferably comprises a transition metal exchange molecular sieve. The transition metal can be selected from the group consisting of cobalt, copper, iron, manganese, nickel, palladium, platinum, ruthenium and rhenium. The transition metal is preferably selected from the group consisting of copper and iron.

The transition metal may be iron. The advantage of SCR catalyst formulations containing iron exchange molecular sieves is that such formulations have superior NO _x reduction activity at temperatures higher than, for example, copper exchange molecular sieves. Iron-exchanged molecular sieve may also generate N _{2 O} of (compared to other types of SCR catalyst formulation) minimum amount.

The transition metal may be copper. An advantage of the SCR catalyst formulations containing copper-exchanged molecular sieve (sometimes be superior low temperature iNO _x reduction activity of example, iron-exchanged molecular sieve) in which to have excellent low temperature iNO _x reduction activity.

The transition metal may be present on the outer surface of the molecular sieve or at an extra skeletal site within the channel, cavity or cage of the molecular sieve.

Typically, the transition metal exchange molecular sieve comprises an amount of 0.10 to 10% by weight, preferably 0.2 to 5% by weight, of the transition metal exchange molecule.

The second SCR catalyst composition may preferably contain a mixture of a metal oxide-based SCR catalyst formulation and a molecular sieve-based SCR catalyst formulation. (A) The metal oxide-based SCR catalyst formulation comprises vanadium oxide (for example, V ₂ O _{5 ) supported on titania (for example, TiO 2} ) and optionally tungsten oxide (for example, WO ₃ ). (B) The molecular sieve-based SCR catalyst formulation preferably comprises a transition metal exchange molecular sieve. More preferably, the transition of the transition metal exchange molecular sieve is iron.

The second SCR catalyst generally comprises a second selective catalytic reduction composition at a total concentration of ^{0.5 to 4.0 g in -3} , eg 1.0 to 3.5 g in ^-3.

The second SCR catalyst contains a flow-through substrate. The flow-through substrate is preferably a flow-through monolith as described above in connection with, for example, a diesel oxidation catalyst.

The flow-through monolith (eg, of the second SCR catalyst) typically has a cell density of 200 to 1000 cells / square inch (cpsi). The cell density of the flow-through monolith is preferably 400 to 1000 cpsi, more preferably 500 to 900 cpsi (eg 600 to 800 cpsi).

The flow-through monolith has a wall thickness (eg, average of 0.05 to 0.35 mm, preferably 0.06 to 0.25 mm, more preferably 0.07 to 0.15 mm (eg, about 0.07 to 0.12 mm)). Inner wall thickness).

The substrate of the second SCR catalyst can contain a second SCR catalyst composition (ie, the second SCR catalyst is obtained by extrusion), or the second SCR catalyst composition is placed on the substrate or It can be carried (ie, the second SCR catalyst composition is applied onto the substrate by the washcoat method). The second SCR catalyst composition is preferably placed or supported on a substrate.

In general, uncoated flow-through monoliths have a porosity of 20-80%, preferably 40-70%, more preferably 45-60%. It is advantageous for the uncoated flow-through monolith to have a high porosity because a relatively high concentration of the second SCR catalyst composition can be placed on the substrate.

The second SCR catalyst may preferably include a downstream area at the outlet end of the substrate. The downstream area typically contains an ammonia slip catalyst (ASC) formulation. Ammonia slip catalyst (ASC) formulations are suitable for oxidizing ammonia (eg, ammonia that has not been oxidized by the second selective catalytic reduction composition). Ammonia slip catalyst (ASC) formulations are known in the art.

Electric Heatable Conduit The exhaust system of the present invention may further include an electrically heatable conduit. The electroheatable conduit is located between the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) and the first selective catalytic reduction catalyst (ie, downstream of the emission control device). It is (eg, located) upstream of the SCR catalyst of 1. The electrically heatable conduit is for heating the exhaust gas discharged from the exhaust control device at a relatively low temperature. By electrically heating the exhaust gas at this position, the temperature of the exhaust gas can be rapidly brought to the effective operating temperature for _{NO x treatment of the first SCR catalyst and the second SCR catalyst downstream.} it can.

The electroheatable conduit is usually part (ie, only part) of the exhaust gas conduit between the outlet of the emission controller and the inlet of the selective catalytic reduction filter catalyst. If the emission control device is (i) diesel oxidation catalyst (DOC) and catalyzed suit filter (CSF) or (ii) cold start concept (dCSC ^TM ) catalyst and catalyzed suit filter (CSF), it can be electrically heated. The conduit is preferably downstream (eg, located) of the outlet of the CSF.

The electrically heatable conduit is connected (eg, fluid connection) to the outlet of the discharge control device, and is preferably directly connected.

The electroheatable conduit is typically upstream of the injector for introducing the ammonia precursor into the exhaust gas. If the exhaust system is equipped with a temperature sensor (eg _{for determining T 1} ) and / or NO _x sensor, the electrically heatable conduit is preferably a temperature sensor (eg _{for determining T 1} ) and /. Or _{upstream of the NO x} sensor (eg, located).

An electrically heatable conduit typically has a power connection, preferably at least two power connections, more preferably only two power connections. Each power connection may be electrically connected to an electrically heatable substrate and power source. The electrically heatable conduit can be heated by Joule heating, where the current through the resistor converts electrical energy into thermal energy.

The electrically heated conduit is an electrically heated conduit in use.

The electrically heated conduit may be electrically connected to the engine management system. The engine management system is configured to activate an electrically heatable conduit when the exhaust gas temperature is <T ₁ (where T ₁ is 230 ° C, preferably 215 ° C, more preferably 200 ° C). May be good.

Additional or alternative, an electroheatable conduit can be connected (eg, a thermocouple) to a temperature sensor located upstream, preferably immediately upstream of the selective catalytic reduction filter catalyst. This temperature sensor is located downstream of the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbons (HC). Temperature sensors are suitable for determining T _1.

Gaseous Ammonia Feeder The exhaust system of the present invention may further include means for introducing gaseous ammonia into the exhaust gas. Means for introducing gaseous ammonia into the exhaust gas are preferred, especially when the temperature of the exhaust gas is <T ₁ (where T ₁ is 230 ° C., preferably 215 ° C., more preferably 200 ° C.). It is a means for introducing directly into the exhaust gas. To avoid doubt, the means for introducing gaseous ammonia into the exhaust gas is to introduce gaseous ammonia directly into the exhaust gas stream. Gaseous ammonia is not produced in situ in the main exhaust stream, for example from ammonia precursors.

Means for introducing gaseous ammonia into the exhaust gas are downstream of the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC), and upstream of the first selective catalytic reduction catalyst. Be placed. Means for introducing gaseous ammonia into the exhaust gas are 0.7 to 1.3 (eg 0.9 to 1.2), eg 1.0 to 1.2 (eg about 1: 1) ammonia vs. NO. A constant amount of gaseous ammonia is controlledly introduced into the exhaust gas upstream of the first selective catalytic reduction filter catalyst to provide the _{x-molar ratio (ANR).}

It has been found that the introduction of gaseous ammonia into the exhaust gas, especially at relatively low temperatures, _{can facilitate the conversion of NO x on the first SCR catalyst and / or the second SCR catalyst.} Injecting an ammonia precursor, such as urea, into the exhaust gas at a relatively low temperature is not possible because ammonia is not formed in situ at such temperatures. In fact, urea can crystallize in the exhaust system at low temperatures.

The means for introducing gaseous ammonia into the exhaust gas may include an ammonia feeder (eg, a gaseous ammonia feeder). The ammonia feeder is usually the first between the emission controller for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) and the selective catalytic reduction filter catalyst (ie, downstream of the outlet of the emission controller). It is connected to the conduit (eg, fluid connection) at (upstream of the inlet of the SCR catalyst). If the emission controller is (i) diesel oxidation catalyst (DOC) and catalyzed suit filter (CSF) or (ii) cold start concept (dCSC ^TM ) catalyst and catalyzed suit filter (CSF), the ammonia feeder is Preferably, it is downstream (eg, located) of the exit of the CSF.

If the exhaust system comprises a mixer, the ammonia feeder is preferably located upstream of the mixer.

The ammonia feeder may be located upstream or downstream of the injector for introducing the ammonia precursor into the exhaust gas. The ammonia feeder is preferably located upstream of the injector for introducing the ammonia precursor into the exhaust gas.

If the exhaust system comprises an electroheatable conduit, the ammonia feeder may be located upstream or downstream of the electroheatable conduit. The ammonia feeder is preferably located downstream of the electrically heated conduit.

Means for introducing gaseous ammonia into the exhaust gas may further include means for producing gaseous ammonia from the ammonia precursor. Means for producing gaseous ammonia from the ammonia precursor are connected to the ammonia feeder (eg, fluid connection). Means for producing gaseous ammonia from the ammonia precursor are located in the secondary exhaust conduit. The ammonia feeder is located within the main exhaust system.

Means for producing gaseous ammonia from ammonia precursors are typically
(I) An injector for introducing the ammonia precursor into the secondary exhaust gas conduit; and (ii) a hydrolysis catalyst for converting the ammonia precursor into gaseous ammonia.
The injector for introducing the ammonia precursor into the secondary exhaust gas conduit is upstream (eg, located) of the hydrolysis catalyst.

To avoid doubt, the injector for introducing the ammonia precursor into the secondary exhaust conduit is an additional injector to the above injector for introducing the ammonia precursor into the main exhaust stream. The injector for introducing the ammonia precursor into the secondary exhaust gas conduit is referred to herein as the "second injector".

The second injector is typically a liquid injector suitable for introducing a solution containing an ammonia precursor into the secondary exhaust conduit. The ammonia precursor is preferably urea or ammonium formate, more preferably urea.

The secondary injector sprays the solution containing the ammonia precursor or the ammonia precursor when injecting into the secondary exhaust conduit upstream of the hydrolysis catalyst, for example by spraying the solution containing the ammonia precursor or the ammonia precursor. .. The secondary injector can be an airless injector or an air assist injector.

The secondary injector is configured to introduce an ammonia precursor into the secondary exhaust gas conduit upstream of the hydrolysis catalyst. The secondary injector is preferably configured to controlfully introduce a certain amount of ammonia precursor into the secondary exhaust gas conduit upstream of the hydrolysis catalyst.

The secondary injector is typically connected to an ammonia precursor storage tank (eg, fluid connection), and the ammonia precursor storage tank is preferably the injector for introducing the ammonia precursor into the exhaust gas (ie, the main injector). It is connected to the injector).

A hydrolysis catalyst for converting an ammonia precursor to gaseous ammonia comprises a substrate and a hydrolysis catalyst composition arranged or supported on the substrate. The base material is preferably a flow-through base material, more preferably a cordierite flow-through base material. Catalytic compositions for hydrolyzing urea are known in the art.

The hydrolysis catalyst composition may include, or may consist essentially of, titanium dioxide (TiO ₂ ), such as Au-doped TiO _2.

The outlet of the hydrolysis catalyst composition is typically connected to an ammonia feeder (eg, a fluid connection).

Generally, the secondary exhaust conduit is connected (eg, fluid connection) to the exhaust manifold of a diesel engine. The second exhaust gas conduit is preferably connected to the exhaust manifold upstream of the turbocharger. The secondary exhaust conduit bypasses the turbocharger. In this configuration, a small amount of hot exhaust (about 1.5 to 7.0%) is drawn from the engine into the secondary exhaust conduit (ie, the sideflow system). When the exhaust gas is diverted from the turbocharger to the secondary exhaust gas conduit, the temperature inside the secondary exhaust gas conduit is significantly higher than the temperature of the main exhaust gas stream.

Means for producing gaseous ammonia from the ammonia precursor may further include a particulate filter, preferably a catalyzed soot filter (CSF).

The particulate filter or CSF is placed in the second flue, upstream of the injector for introducing the ammonia precursor into the secondary flue. The particulate filter or CSF is also upstream of the hydrolysis catalyst for converting the ammonia precursor to gaseous ammonia.

The secondary exhaust gas conduit is (for example, when the temperature (T ₁ ) of the exhaust gas between the emission control device and the first SCR catalyst is ≥200 ° C, preferably 215 ° C, more preferably 230 ° C). It may include a valve to close the exhaust conduit. The valve may be electrically connected to the engine management system.

The valve is typically located upstream of the secondary injector, preferably upstream of the particulate filter or CSF.

Ammonia slip catalyst (ASC)
In addition to or as an alternative to the ammonia slip catalyst (ASC) formulation present in the downstream area of the SCR catalyst, the exhaust system may further include an ammonia slip catalyst (ASC) (ie, a separate ASC). The ASC comprises an ammonia slip catalyst formulation placed on a substrate (ie, a substrate separate from the substrate of the second SCR catalyst).

The ammonia slip catalyst is typically downstream, preferably immediately downstream of the second SCR catalyst. Therefore, the outlet of the second SCR catalyst is typically connected (eg, fluid connection) to the inlet of the ammonia slip catalyst.

The substrate for the ammonia slip catalyst is preferably a flow-through monolith.

Vehicles The present invention further provides vehicles. The vehicle of the present invention comprises the diesel engine and exhaust system of the present invention. Typically, the diesel engine is a regular (ie, conventional) diesel engine.

The diesel engine may be equipped with an engine management system.

The vehicle is a lightweight diesel vehicle (LDV) as required by US or European law. Lightweight diesel vehicles typically weigh <2840 kg, more preferably <2610 kg.

In the United States, a lightweight diesel vehicle (LDV) refers to a diesel vehicle with a gross vehicle weight of ≤8500 lbs (US lbs). In Europe, the term lightweight diesel vehicle (LDV) refers to (i) a passenger vehicle with eight or less seats in addition to the driver's seat and a maximum mass of 5 tons or less, and (ii) a maximum mass of 12 tons or less. Refers to a freight transport vehicle with.

The vehicle is preferably a large diesel vehicle (HDV), such as a diesel vehicle having a gross vehicle weight of> 8500 lbs (US lbs) as required by US law.

Diesel engines run on diesel fuel containing ≦ 50 ppm sulfur, more preferably ≦ 15 ppm sulfur, for example ≦ 10 ppm sulfur, even more preferably ≦ 5 ppm sulfur. Such diesel fuel is often referred to as "ultra-low sulfur diesel" (ULSD).

Definitions As used herein, the term "mixed oxide" generally refers to a mixture of single-phase oxides as conventionally known in the art. As used herein, the term "composite oxide" usually refers to a composition of oxides having two or more phases, as conventionally known in the art.

For the avoidance of doubt, the term "combination of platinum (Pt) and palladium (Pd)" used herein in relation to a region, area or layer refers to the presence of both platinum and palladium. The term "combination" does not require platinum and palladium to be present as a mixture or alloy, but such mixtures or alloys are included in this term.

As used herein, the expression "consisting essentially" includes certain materials and any other material or process that do not substantially affect the basic properties of the technical feature, such as small amounts of impurities. Limit the scope of its technical features to. The expression "essentially consists of" includes the expression "consists of".

With respect to the material, typically in the context of the content of the washcoat region, washcoat layer or washcoat area, the expression "substantially free" as used herein is, for example, ≤5% by weight, preferably ≤≤ It means a small amount of material, such as 2% by weight, more preferably ≦ 1% by weight. The expression "substantially free of" includes the expression "does not contain".

The expression "about" as used herein with respect to the end point of a numerical range includes the exact end point of the specified numerical range. Therefore, for example, an expression that defines a parameter up to "about 0.2" includes a parameter up to 0.2 including 0.2.

The present invention will then be illustrated by the following non-limiting examples.

Example 1
An exhaust system containing a combination of a diesel oxidation catalyst (DOC), a selective catalytic reduction filter catalyst and an SCR catalyst with a high porosity substrate was tested as follows.

Diesel oxidation catalysts and SCR catalysts were produced using, for example, the conventional methods described in WO 9/47260, WO 2011/080525, and WO 2014/195685. The selective catalyst reduction filter catalyst was produced using the method described in WO 2015/145122.

The substrate of the diesel oxidation catalyst (DOC) had a size of 10.5 "x4". The substrate had a cell density of 400 cpsi and a wall thickness of 7 mils. The filling amount of the catalyst composition was 40 g ft- ³ . The catalyst composition contained Pt, Pd and Al ₂ O ₃ .

The base material of the selective catalyst reduction filter catalyst was 10.5 "x12" in size. The wall flow substrate had a cell density of 300 cpsi and a wall thickness of 12 mils. The wash coat filling amount was 1.7 g in ^-3 . The catalyst composition contained Cu zeolite having a CHA skeleton. The copper filling amount was 3.33% by weight.

The substrate for the selective catalytic reduction (SCR) catalyst was 10.5 "x 6" in size. The substrate had a cell density of 600 cpsi and a wall thickness of 4 mils. The wash coat filling amount was 4 g in ^-3 . The catalyst composition contained Cu zeolite having a CHA skeleton. The copper filling amount was 3.33% by weight.

Prior to testing the exhaust system, the DOC, SCR-DPF and SCR catalysts were hydrothermally aged (using 10% water) at 650 ° C. for 100 hours, respectively.

Example 2
The exhaust system of Example 1 was tested as follows, except that the diesel oxidation catalyst (DOC) was ^{replaced with a cold start concept (dCSC TM) catalyst.}

The substrate for the cold start concept (dCSC ^TM ) catalyst was 10.5 "x 6" in size. The substrate had a cell density of 400 cpsi and a wall thickness of 4 mils. The cold start concept catalyst had two layers, namely the bottom layer and the top layer. The bottom layer (ie, directly coated on the substrate) had a washcoat filling of the catalyst composition of 3 g in ^-3 . The catalyst composition was a zeolite containing Pd, which had a CHA skeleton. The filling amount of Pt was 100 g ft- ³ . The top layer (coated on the bottom layer) contained ^{Pt (50 g ft -3} ) and alumina (1.12 ^{g in -3).} The total weight ratio of Pt to Pd in the catalyst was 1: 2.

The cold start concept (dCSC ^TM ) catalyst, SCR-DPF and SCR catalyst were each hydrothermally aged in the same manner as in Example 1.

Test Conditions The 2007 model Cummins ISL diesel engine was used to test the exhaust systems of Examples 1 to 3, respectively. The details of the engine are shown in Table 1. During this test, it was adjusted EGR so as to have a 4.0 g / hp-hr engine-out NO _x. Urea was delivered and injected into the exhaust by an air-assisted Grundfos pump. A 6-inch static mixer was placed in front of the SCR-DPF of each exhaust system and behind the injection nozzle to ensure good mixing and uniform urea distribution.

The power meter used in this test was a Horiba 800HP AC motoring dynamo. The intake flow rate was measured with a Sierra air flow meter with a measurement range of 0-2400 kg / hr with a full-scale +/- 1% accuracy. Engine out emissions were measured using a Horiba MEXA 7500D dual bench (CO, HC and NO _x ) analyzer with full-scale +/- 1% accuracy. System out emissions were also measured using FTIR (MKS model 2030 HS). A pressure transducer, Setra Model 206, was used to monitor the SCR-DPF SCR-DPF back pressure. The temperature inside the system was measured using a K-type thermocouple.

A heavy load transient cycle (FTP) test was performed to measure the performance of this system. Cold and hot cycles were used in different parts of the test. The average ammonia-to-NOx ratio (ANR) of the urea supply during the transient cycle was 1.2 to 1.3.

Results NO _{x reduction under cold FTP cycle Total NO x} conversion during HDD cold FTP cycle with ammonia to NO x ratio (ANR) of 1.2 to 1.3 for each of the exhaust systems of Examples 1 and 2 Was measured. Prior to the start of the test, the system was actively regenerated to remove the suit, after which the system was cooled for 3 hours before the start of the FTP cycle. Standard urea injection was used during these tests.

_{During cold FTP, the NO x} conversion achieved with the DOC system (Example 1) was 75%. When a system with a cold start concept (dCSC ^TM ) catalyst (Example 2) was tested, the NO _x conversion rate increased to 80%. This increase was due to the storage and release of the NO _x by cold start concept (DCSC ^TM) catalyst. The cold start concept (dCSC ^TM ) catalyst stored _{NO x} in the first 200 seconds of the system's cold cycle. The stored NO _x was released as the system temperature rose approximately 300 seconds after entering the cycle. At this point, the SCR-DPF was warm and capable of reducing _{NO x.} Even if there was no urea supply during the cold section of the cycle, _{storage of NO x} and subsequent release during the warm period allowed _{NO x conversion when the urea supply was made.} When DOC was used in the system (Example 1), reduction was not achieved in the first 200 seconds. As with the system described above (Example 2), unstored NOx was not converted in this section because the temperature was too low to supply urea.

Results during the cold FTP test show ^{that a system designed with a cold start concept (dCSC TM} ) catalyst (Example 2) has a higher NOx conversion rate due to the storage and release capacity of ^{the cold start concept (dCSC TM) catalyst.} It was shown to have. A comparison of these two systems is shown in FIG. The results demonstrated the benefits of an exhaust system comprising a cold start concept (DCSC ^TM) catalyst for the future high NO _x conversion system.

Effect of Gas NH ₃ on Cold FTP Cycle The effect of NH ₃ gas supply on cold FTP cycle under low temperature conditions was evaluated.

_{A side-flow NH 3} feeder was designed to _{generate NH 3} gas and inject it into the main exhaust when urea cannot be supplied due to very low temperatures. A small amount of high temperature exhaust flow (about 1.5 to 7.0% (eg 15-25 kg / hr)) was drawn from the engine into the side flow system by connecting the side flow NH _{3 feeder to the engine pre-turbo.} The exhaust flow temperature was significantly higher than the main exhaust temperature as the flow was diverted from the preturbo to the sideflow feeder. Injecting urea into the side-flow reactor, it was converted to NH ₃ gas on the hydrolysis catalyst. The generated NH ₃ was returned to the main exhaust upstream of the mixer and SCR-DPF.

_{NH 3} was injected into the main exhaust stream from the start of the cold FTP cycle (ie, a temperature too low for urea supply) until the SCR-DPF inlet temperature reached 215 ° C. _{using sideflow NH 3 feeder control.} .. When the temperature exceeded 215 ° C., the NH ₃ supply was stopped and the main (standard) urea supply system was activated for the rest of the cycle to inject urea into the exhaust gas. Both strategies for system injection control were _{set to maintain an ammonia to NO x} overall ratio (ANR) of approximately 1.2. The outline of this device is shown in FIG.

In the case of an exhaust system with DOC (Example 1), NO _x reduction was observed after 50 seconds. This was due to the early availability of NH ₃ gas in the exhaust stream.

The experiment was repeated using an exhaust system (Example 2) equipped with a cold start concept (dCSC ^{TM) catalyst.} The cold start concept (dCSC ^TM _{) catalyst stored NO x} in the first 200 seconds. NOv was released as the catalyst temperature increased. Since there was _{NH 3} available at the start of the _{cycle, NO x} reduction was performed under a cold NTP cycle using a sideflow _{NH 3 feeder without the addition of NH 3} with the exhaust system of Example 2. By comparison, more NO _x was converted with SCR-DPF.

The addition of NH ₃ with a side-flow NH ₃ supply body during the cold FTP cycle, NO _x conversion rate of the exhaust system containing DOC (Example 1) was increased to 80% from baseline. In the case of an exhaust system (Example 2) equipped with a cold start concept (dCSC ^TM _{) catalyst, the NO x} conversion rate increased to 83%. This test showed that the presence _{of NH 3} in the early stages of the cycle further increased the _{NO x conversion rate.}

Effect under cold FTP cycle of the NH ₃ which is previously stored in the cold FTP cycle, to evaluate the effect of the NH ₃ stored in advance in conjunction with standard urea donor. To simulate the early and full availability of gaseous NH ₃ , the system was pre-saturated with ammonia prior to the FTP test. The presaturation test was performed during the preparatory cycle prior to the start of cold FTP.
Presaturation until considered SCR-DPF and SCR catalyst is saturated with NH _3, from about 1.2 1.3 ANR, was carried out by performing a plurality of hot FTP cycle. After the system was saturated, the engine was stopped and the system was cooled for 3 hours. After cooling, a single cold FTP test was performed on the system in conjunction with normal urea supply. During this time, NH ₃ supplied from the side reactor was not available.

As before, the exhaust temperature was low and urea was not injected for most of the first half of the cycle. In the case of the exhaust system of Example 1 (DOC), the average temperature was about 245 ° C. However, when the temperature rose, NO _x reduction started in 100 seconds. Most of the Nox _x conversions started about 230 seconds after entering the cycle. This was _{due to the presence of presaturated NH 3} (SCR-DPF and SCR catalyst) in the system.

In the case of the exhaust system of Example 2 (cold start concept (dCSC ^TM ) catalyst), the SCR-DPF is for the first 150 seconds because _{NO x} is stored at the beginning of the cycle and the pre-stored NH _{3 is available. NO x} can be further reduced during the period. _{Since NO x} is released approximately 250 seconds after entering the cycle, the SCR-DPF can reduce all NO _{x with pre-stored NH 3.}

During the cold FTP, NO _x conversion rate, increases the DOC-containing system (Example 1) In 88%, the cold start concept (DCSC ^TM) catalyst-containing systems using presaturation NH ₃ Strategy (Example 2) It rose to at least 91%. _{This test showed that much higher NO x} conversion rates are possible during the cold FTP cycle if _{sufficient NH 3} is present from the early stages of the cycle.

Effect of pre-stored NH ₃ and temperature control on cold FTP cycle After either DOC (Example 1) or Cold Start Concept (dCSC ^TM ) catalyst (Example 2), before urea injection and SCR-DPF. , An electric heater was installed (see FIG. 5).

Five consecutive FTP cycles with urea injection of ANR 1.2-1.3 were performed to pre-store NH _{3 and each system was pretreated.} The system was cooled for 3 hours before running the cold FTP cycle. The same ANR of 1.2-1.3 was used during this cycle _{to determine the NO x} reduction capacity of the system.

An electric heater was used to warm the exhaust in the first 400 seconds (ie, cold section) of the cold FTP cycle. The maximum output of the heater was 20 kW. The electric heater was turned off in 400 seconds after entering the cycle. This test was to simulate the presence of a temperature control that allowed _{an early NH 3-} NO _x reaction and conditions with presaturation of _{NH 3.} The presence of temperature control also enabled an early supply of urea.

By turning on the electric heater, the exhaust temperature rose rapidly, reaching 200 ° C. in 200 seconds after entering the cycle. The average temperature was about 270 ° C. Since NH ₃ was pre-stored in the SCR-DPF and SCR catalyst, sufficient reducing agent was available from the beginning of the cycle. There was no supply of urea while the temperature was below 200 ° C. When the temperature of the SCR catalyst reached 200 ° C., urea supply was possible 200 seconds after entering the cycle.

In the case of an exhaust system containing DOC (Example 1), this allowed 94% NO _x reduction. The reduction of NO _x began 80 seconds after entering the cycle due to the higher temperature. There was almost no peak _{NO x} emission 100 seconds after entering this cycle.

For an exhaust system that includes a cold start concept (dCSC ^TM ) catalyst (Example 2), the cold start concept (dCSC ^TM ) catalyst should store a _{significant amount of NO x} in the first 100 seconds at the start of the cycle. Was done. After 100 seconds, the temperature rises, cold start concept (DCSC ^TM) catalysts started to some of the NO _x release was almost released after 250 seconds. On the other hand, when a heater was used, the inlet temperature of the SCR-DPF reached 200 ° C. about 100 seconds after entering the cycle, and NO _x could be reduced from the SCR-DPF to the SCR catalyst. This was also supported by the NH ₃ stored available. As a result, there was no leakage _{of NO x} in the exhaust pipe after the first 100 seconds _{and all NO x} was converted. _{This resulted in a NO x} conversion of 98% for Example 2, which is an exhaust system containing a cold start concept (dCSC ^{TM) feel.}

The results of the above test are shown in Table 2. _{This table shows the NO x} ^{conversion of an exhaust system containing a cold start concept (dCSC TM} ) catalyst (Example 2) for all options tested under cold FTP and an exhaust containing DOC (Example 1). Compared to the system. Cold start Concept (DCSC ^TM) results on the catalyst, as compared to DOC containing system always showed higher system _the NO _x reduction, demonstrates the advantages of cold start concept (DCSC ^TM) catalyst.

Example 3
The exhaust system of Example 2 was improved by changing the catalyst composition of the SCR-DPF from Cu zeolite to a vanadium-containing catalyst. The wall flow substrate used was the same as the wall flow substrate used in the selective catalytic reduction filter catalyst of Example 1.

The catalyst composition of SCR-DPF has a vanadium filling amount of 24 g ft ^-3 , a tungsten ^{filling amount of 303 g ft -3} , and a titania filling amount of 1.12 g in ^-3. It contained a titania catalyst. The catalyst composition also contained an iron exchange zeolite, which had an MFI skeleton. The filling amount of Fe was 10 g ft ^-3 , and the filling amount of zeolite was 0.16 g in ^-3 .

The cold start concept (dCSC ^TM ) catalyst was the same as the cold start concept catalyst used in Example 2. The SCR catalyst was the same as the SCR catalyst used in Example 1.

The cold start concept (dCSC ^TM ) catalyst, SCR-DPF and SCR catalyst were each hydrothermally aged in the same manner as in Example 1.

The exhaust system of Example 3 was tested using the same methods and conditions as used in Examples 1 and 2, and the effect of pre-stored _{NH 3 on the cold FTP cycle and the pre-stored NH 3} and temperature. The effect of management was evaluated. The exhaust system of Example 2 was retested for comparison. The amount of N _{2 O} which is discharged by the exhaust system of Example 2 and 3 were also determined. The results are shown in Table 3.

Exhaust system of example 3 shows a No _x conversion comparable to the exhaust system of the second embodiment. _{However, the amount of N 2} O discharged by the exhaust system of Example 3 was significantly lower than the amount of _{N 2} O discharged by the exhaust system of Example 2.

Experiments also exudates Cu- zeolite CR catalyst of Example 3 was obtained from the exhaust system of which is replaced by an extrusion vanadium SCR catalyst, as compared to the exhaust system of Example 3, equivalent of the NO _x conversion while providing rate, it shows that it is possible discharge of a small N _{2 O.}

For the avoidance of doubt, the entire contents of all documents cited herein are incorporated herein by reference.

Claims (33)

An exhaust system for treating the exhaust gas generated by a diesel engine.
(A) An emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) containing a platinum group metal (PGM) and a base material, wherein the platinum group metal (PGM) is platinum (Platinum (PGM). With an emission control device selected from Pt), palladium (Pd) and combinations thereof;
(B) With an injector for introducing an ammonia precursor into the exhaust gas and downstream of an emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC);
(C) A first selective catalytic reduction catalyst containing a substrate and a first selective catalytic reduction composition downstream of an injector for introducing an ammonia precursor into the exhaust gas, wherein the substrate flows. With a first selective catalytic reduction catalyst that is either a through substrate or a filtering substrate;
(D) Downstream of the first selective catalytic reduction catalyst, with a flow-through substrate and a second selective catalytic reduction catalyst containing a second selective catalytic reduction (SCR) composition, and
An exhaust system in which at least one of the emission controller and the first selective catalytic reduction catalyst has a filtering substrate. A means for introducing gaseous ammonia into the exhaust gas, downstream of the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC), upstream of the first selective catalytic reduction catalyst. The exhaust system according to claim 1, further comprising an arranged means. Means for producing gaseous ammonia from ammonia precursors are (i) injectors for introducing ammonia precursors into secondary exhaust gas conduits; and (ii) hydrolysis catalysts for converting ammonia precursors to gaseous ammonia. Prepare,
An injector for introducing the ammonia precursor into the secondary exhaust gas conduit is upstream of the hydrolysis catalyst,
The exhaust system according to claim 2. The exhaust system of claim 3, wherein the secondary exhaust conduit is connected to the exhaust manifold of the diesel engine upstream of the turbocharger. Claims 1 to 4, further comprising an electrically heatable conduit between an exhaust control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) and a first selective catalytic reduction catalyst. The exhaust system according to any one item. An electrically heatable conduit is an exhaust gas conduit between the outlet of the emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) and the inlet of the first selective catalytic reduction catalyst. The exhaust system according to claim 5, which is a part. Emission control devices for oxidizing carbon monoxide (CO) and / or hydrocarbons (HC) are: (i) diesel oxidation catalyst (DOC), (ii) catalyzed soot filter (CSF), (iii) cold start. Claims 1-6, which may be selected from the group consisting of (iv) diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF); and (v) cold start concept catalyst and catalyzed soot filter (CSF). The exhaust system according to any one of the above. The emission control device is (i) Catalyzed Soot Filter (CSF);
(Ii) Cold start concept catalyst with filtering substrate;
(Iii) Diesel Oxidation Catalyst (DOC) and Catalyzed Suit Filter (CSF); or (iv) Cold Start Concept Catalyst and Catalyzed Suit Filter (CSF)
Is one of
The exhaust system according to claim 7, wherein the first selective catalytic reduction catalyst has a flow-through substrate. The emission controller is (i) a diesel oxidation catalyst (DOC); or (ii) a cold start concept catalyst with a flow-through substrate;
Is one of
The first selective catalytic reduction catalyst has a filtering substrate,
The exhaust system according to claim 7. The emission control device for oxidizing carbon monoxide (CO) and / or hydrocarbon (HC) is provided with a cold start concept catalyst, and the cold start concept catalyst contains a catalytic material supported on a substrate, and the catalytic material. The exhaust system according to any one of claims 1 to 9, wherein the exhaust system comprises a molecular sieve catalyst containing a precious metal and a molecular sieve. The exhaust system according to claim 10, wherein the noble metal contains palladium. The exhaust system according to claim 10 or 11, wherein the molecular sieve is selected from a small pore molecular sieve, a medium pore molecular sieve, and a large pore molecular sieve. Molecular sieves are 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, and any mixture of two or more of these. The exhaust system according to any one of claims 10 to 12, which is a small pore molecular sieve having a skeletal structure represented by a skeletal type code (FTC) selected from the group consisting of intergrowth crystals. The exhaust system according to claim 13, wherein the small pore molecular sieve has a skeletal structure having an FTC represented by AEI or CHA. The exhaust system according to any one of claims 1 to 14, wherein the injector (b) is a liquid injector for introducing a solution containing an ammonia precursor into an exhaust gas. The exhaust system according to any one of claims 1 to 15, wherein the first selective catalytic reduction composition comprises a metal oxide-based SCR catalyst formulation, a molecular sieve-based SCR catalyst formulation, or a mixture thereof. The exhaust system according to claim 16, wherein the first selective catalytic reduction composition comprises a metal oxide-based SCR catalyst formulation containing vanadium or tungsten or a mixture thereof supported on a fire resistant oxide. The exhaust system according to claim 16 or 17, wherein the first selective catalytic reduction composition comprises a molecular sieve-based SCR catalyst formulation comprising a transition metal exchange molecular sieve. The exhaust system according to claim 18, wherein the transition metal of the transition metal exchange molecular sieve is selected from the group consisting of copper and iron. The exhaust system according to claim 18 or 19, wherein the transition metal exchange molecular sieve is a small pore molecular sieve having a skeletal structure represented by FTC selected from the group consisting of CHA and AEI. The exhaust system according to any one of claims 16 to 20, wherein the first SCR catalyst composition comprises a mixture of a metal oxide-based SCR catalyst formulation and a molecular sieve-based SCR catalyst formulation. The metal oxide-based SCR catalyst formulation contains a vanadium oxide supported on titania and optionally a tungsten oxide, and the molecular sieve-based SCR catalyst formulation of (b) is a transition metal exchange. 21. The exhaust system of claim 21, wherein the transition metal of the transition metal exchange molecular sheave, including the molecular sheave, is iron. Claims 1-22, wherein the selective catalytic reduction (SCR) catalyst of (d) has a flow-through substrate that is a flow-through monolith, and the uncoated flow-through monolith has a porosity of 45-60%. The exhaust system according to any one of the above. The exhaust system according to any one of claims 1 to 23, wherein the second selective catalytic reduction composition comprises a metal oxide-based SCR catalyst formulation, a molecular sieve-based SCR catalyst formulation, or a mixture thereof. 24. The exhaust system of claim 24, wherein the second selective catalytic reduction composition comprises a metal oxide-based SCR catalyst formulation comprising vanadium or tungsten or a mixture thereof supported on a fire resistant oxide. The exhaust system according to claim 24 or 25, wherein the second selective catalytic reduction composition comprises a molecular sieve-based SCR catalyst formulation comprising a transition metal exchange molecular sieve. 28. The exhaust system of claim 26, wherein the transition metal of the transition metal exchange molecular sieve is selected from the group consisting of copper and iron. The exhaust system according to claim 26 or 27, wherein the transition metal exchange molecular sieve is a small pore molecular sieve having a skeletal structure represented by a skeletal type code selected from the group consisting of CHA and AEI. The exhaust system according to any one of claims 24 to 28, wherein the second SCR catalyst composition comprises a mixture of a metal oxide-based SCR catalyst formulation and a molecular sieve-based SCR catalyst formulation. The metal oxide-based SCR catalyst formulation contains a vanadium oxide supported on titania and optionally a tungsten oxide, and the molecular sieve-based SCR catalyst formulation of (b) is a transition metal exchange. 29. The exhaust system of claim 29, wherein the transition metal of the transition metal exchange molecular sheave, including the molecular sieve, is iron. The exhaust system according to any one of claims 1 to 30, wherein the second selective catalytic reduction (SCR) of (d) comprises a downstream area and the downstream area comprises an ammonia slip catalyst (ASC) formulation. A second selective catalytic reduction (SCR) catalyst further comprising an ammonia slip catalyst (ASC) downstream of the catalyst, wherein the ammonia slip catalyst (ASC) comprises an ammonia slip catalyst formulation disposed on a substrate. The exhaust system according to any one of 1 to 31. A vehicle comprising a diesel engine and the exhaust system according to any one of claims 1 to 32.

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