EXHAUST SYSTEM FOR A DIESEL ENGINE

• US 20170298796A1
• Filed: 04/13/2016
• Published: 10/19/2017
• Est. Priority Date: 04/13/2016
• Status: Active Grant

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Johnson Matthey PLC
• Inventors: NASERI, Mojghan, AYDIN, Ceren, MULLA, Shadab, CONWAY, Raymond
• Granted Patent: US 10,125,646 B2
• Time in Patent Office: Days
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 13/16 Selection of particular materials
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/1453 Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
• CPC Class Codes: F01N 3/035 with catalytic reactors , e.g. catalysed diesel particulate filters
• CPC Class Codes: F01N 3/103 Oxidation catalysts for HC and CO only
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

An exhaust system for treating an exhaust gas produced by a diesel engine comprises: (a) an emissions control device (ECD) for oxidising carbon monoxide (CO) and/or hydrocarbons (HCs), wherein the emissions control device comprises a platinum group metal (PGM) and a substrate, wherein the PGM is platinum, palladium or a combination thereof; (b) an injector for introducing an ammonia precursor into the exhaust gas, which is downstream of the ECD; (c) a first selective catalytic reduction (SCR) catalyst downstream of the injector, wherein the first SCR catalyst comprises a substrate and a first SCR composition, wherein the substrate is either a flow-through substrate or a filtering substrate; (d) a second SCR catalyst downstream of the first SCR catalyst, wherein the second SCR catalyst comprises a flow-through substrate and a second SCR composition; and wherein at least one of the ECD and the first SCR reduction catalyst has a filtering substrate.

Claims

1. An exhaust system for treating an exhaust gas produced by a diesel engine comprising:

(a) an emissions control device for oxidising at least one of carbon monoxide (CO) and hydrocarbons (HCs), wherein the emissions control device comprises a platinum group metal (PGM) and a substrate, wherein the platinum group metal (PGM) is selected from platinum (Pt), palladium (Pd) and a combination thereof;

(b) an injector for introducing an ammonia precursor into the exhaust gas, which is downstream of the emissions control device for oxidising at least one of carbon monoxide (CO) and hydrocarbons (HCs);

(c) a first selective catalytic reduction catalyst downstream of the injector for introducing an ammonia precursor into the exhaust gas, wherein the first selective catalytic reduction catalyst comprises a substrate and a first selective catalytic reduction composition, wherein the substrate is either a flow-through substrate or a filtering substrate;

(d) a second selective catalytic reduction catalyst downstream of the first selective catalytic reduction catalyst, wherein the second selective catalytic reduction catalyst comprises a flow-through substrate and a second selective catalytic reduction (SCR) composition; and

wherein at least one of the emissions control device and the first selective catalytic reduction catalyst has a filtering substrate.

2. An exhaust system according to claim 1 further comprising a gaseous ammonia doser for introducing gaseous ammonia into the exhaust gas, wherein the gaseous ammonia doser is disposed downstream of the emissions control device for oxidising at least one of carbon monoxide (CO) and hydrocarbons (HCs) and upstream of the first selective catalytic reduction catalyst.

3. An exhaust system according to claim 2, wherein the gaseous ammonia doser comprises:

(i) an injector for introducing an ammonia precursor into a secondary exhaust gas conduit; and

(ii) a hydrolysis catalyst for converting the ammonia precursor into gaseous ammonia;

wherein the injector for introducing an ammonia precursor into a secondary exhaust gas conduit is upstream of the hydrolysis catalyst.

4. An exhaust system according to claim 3, wherein the secondary exhaust gas conduit is coupled to an exhaust manifold of the diesel engine upstream of a turbocharger.

5. An exhaust system according to claim 1 further comprising an electrically heatable conduit between the emissions control device for oxidising at least one of carbon monoxide (CO) and hydrocarbons (HCs), and the first selective catalytic reduction catalyst.

6. An exhaust system according to claim 5, wherein the electrically heatable conduit is part of an exhaust gas conduit between an outlet of the emissions control device for oxidising at least one of carbon monoxide (CO) and hydrocarbons (HCs) and an inlet of the first selective catalytic reduction catalyst.

7. An exhaust system according to claim 1, where the emissions control device for oxidising carbon monoxide (CO) and/or hydrocarbons (HCs) may be selected from the group consisting of (i) a diesel oxidation catalyst (DOC), (ii) a catalysed soot filter (CSF), (iii) a cold start concept catalyst;

(iv) a diesel oxidation catalyst (DOC) and a catalysed soot filter (CSF); and

(v) a cold start concept catalyst and a catalysed soot filter (CSF).

8. An exhaust system according to claim 1, wherein the emissions control device for oxidising at least one of carbon monoxide (CO) and hydrocarbons (HCs) comprises a cold start concept catalyst, wherein the cold start concept catalyst comprises a catalytic material supported on a substrate, wherein the catalytic material comprises a molecular sieve catalyst comprising a noble metal and a molecular sieve.

9. An exhaust system according to claim 8, wherein the noble metal comprises palladium.

10. An exhaust system according to claim 8, wherein the molecular sieve is selected from a small pore molecular sieve, a medium pore molecular sieve and a large pore molecular sieve.

11. An exhaust system according to claim 10, wherein the molecular sieve is a small pore molecular sieve having a framework structure with an FTC represented by AEI or CHA.

12. An exhaust system according to claim 1, wherein (b) the injector is a liquid injector for introducing a solution comprising an ammonia precursor into the exhaust gas.

13. An exhaust system according to claim 1, 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.

14. An exhaust system according to claim 13, wherein the first selective catalytic reduction composition comprises a metal oxide based SCR catalyst formulation, which comprises vanadium or tungsten or a mixture thereof supported on a refractory oxide.

15. An exhaust system according to claim 13, wherein the first selective catalytic reduction composition comprises a molecular sieve based SCR catalyst formulation, which comprises a transition metal exchanged molecular sieve.

16. An exhaust system according to claim 13, wherein the metal oxide based SCR catalyst formulation comprises an oxide of vanadium and optionally an oxide of tungsten, supported on titania, and (b) the molecular sieve based SCR catalyst formulation comprises a transition metal exchanged molecular sieve, wherein the transition metal of the transition metal exchanged molecular sieve is iron.

17. An exhaust system according to claim 1, wherein the (d) selective catalytic reduction (SCR) catalyst has a flow-through substrate, which is a flow-through monolith, wherein the uncoated flow-through monolith has a porosity of 45 to 60%.

18. An exhaust system according to claim 1, 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.

19. An exhaust system according to claim 18, wherein the second selective catalytic reduction composition comprises a metal oxide based SCR catalyst formulation, which comprises vanadium or tungsten or a mixture thereof supported on a refractory oxide.

20. An exhaust system according to claim 18, wherein the second selective catalytic reduction composition comprises a molecular sieve based SCR catalyst formulation, which comprises a transition metal exchanged molecular sieve.