Diesel engine and a catalysed filter therefor

Patent metadata

Field	Value
Publication number	US-9169753-B2
Application number	US-54783404-A
Country	US
Kind code	B2
Filing date	Mar 5, 2004
Priority date	Mar 5, 2003
Publication date	Oct 27, 2015
Grant date	Oct 27, 2015

Abstract

A diesel engine includes an exhaust system having a particulate filter made from a porous material having a mean pore diameter of from 5 μm to 40 μm, a porosity of at least 40% and a bulk volumetric heat capacity of at least 0.50 J cm −3 K −1 at 500° C. The filter includes a diesel oxidation catalyst (DOC) located in a first catalyst zone on the front end of the filter and at least one catalyst zone located downstream thereof, for oxidizing carbon monoxide, hydrocarbons and nitrogen monoxide. The engine includes engine management means, in use, to provide continuously or intermittently an exhaust gas having sufficient nitrogen oxides or hydrocarbon and/or an exhaust gas of sufficiently high temperature to combust particulate matter. The platinum group metal (PGM) loading in the first catalyst zone is greater than the total PGM loading in the at least one downstream catalyst zone.

First claim

The invention claimed is:

1. A diesel engine system comprising:
an exhaust system comprising: a particulate filter made from a porous material having a mean pore diameter of from 5 μm to 40 μm, a porosity of at least 40% and a bulk volumetric heat capacity of at least 0.50 J cm −3 K −1 at 500° C., which filter comprising a plurality of catalyst zones having a total quantity of at least one platinum group metal (PGM) comprising a first catalyst zone located on the front end of the filter and at least one catalyst zone located downstream thereof, wherein the first catalyst zone comprises a diesel oxidation catalyst (DOC) comprising a first quantity of the total quantity of the at least one PGM located in a zone on the front end of the filter for oxidising carbon monoxide (CO), hydrocarbons (HC) and nitrogen monoxide (NO), and wherein the at least one downstream catalyst zone comprises a second quantity of the total quantity of the at least one PGM and the at least one downstream catalyst zone is located throughout the remainder of the particulate filter following the first catalyst zone, wherein the first quantity is greater than the second quantity; and
an engine management means, in use, to provide continuously or intermittently:
(a) an exhaust gas comprising sufficient nitrogen oxides (NO x ) or HC and an exhaust gas of sufficiently high temperature to combust particulate matter (PM) in the filter; or
(b) an exhaust gas comprising sufficient NO x or HC to combust particulate matter (PM) in the filter; or
(c) an exhaust gas of sufficiently high temperature to combust particulate matter (PM) in the filter; and
wherein the first catalyst zone and the at least one downstream catalyst zone are arranged such that the exhaust gas flows through the first catalyst zone having the first quantity and then through the at least one downstream zone having the second quantity.

2. The diesel engine system according to claim 1 , wherein the upstream end of the filter is disposed up to 1 meter from the exhaust manifold or turbo.

3. The diesel engine system according to claim 1 , wherein the filter has a shape of a honeycomb, the honeycomb having an inlet end and an outlet end, and a plurality of cells extending from the inlet end to the outlet end, the cells having porous walls wherein part of the total number of cells at the inlet end are plugged along a portion of their lengths, and the remaining part of the cells that are open at the inlet end are plugged at the outlet end along a portion of their lengths, so that a flowing exhaust gas stream passing through the cells of the honeycomb from the inlet end flows into the open cells, through the cell walls, and out of the filter through the open cells at the outlet end.

4. The diesel engine system according to claim 1 , wherein the filter material comprises a ceramic material.

5. The diesel engine system according to claim 1 , wherein the filter material is selected from the group consisting of silicon carbide, aluminium nitride, silicon nitride, aluminium titanate, alumina, sintered metal, cordierite, mullite, pollucite, a thermet, a mixture of silicon carbide and silicon nitride, and mixtures and composites of any two or more thereof.

6. The diesel engine system according to claim 1 , wherein first catalyst zone and the at least one downstream catalyst zone comprise the same or a different catalyst.

7. The diesel engine system according to claim 1 , wherein the at least one downstream catalyst zone comprises a longitudinal gradient of catalyst loading.

8. The diesel engine system according to claim 1 , wherein the at least one downstream catalyst zone comprises a lateral gradient of catalyst loading.

9. The diesel engine system according to claim 1 , wherein the PGM in the at least one downstream catalyst zone is supported by the filter material per se.

10. The diesel engine system according to claim 1 , wherein the engine management means provide intermittent provision of sufficient NO x in the exhaust gas to combust PM in the filter by adjusting the rate of exhaust gas recirculation (EGR).

11. A diesel engine system according to claim 1 , wherein the first catalyst zone and the at least one downstream catalyst zone comprise a plurality of zones collectively arranged in a longitudinal stepwise gradient of catalyst loading.

12. The diesel engine system according to claim 1 , wherein the filter comprises at least one washcoat zone comprising a particulate refractory oxide along at least a part of a length of the filter, wherein each zone comprises the same or a different washcoat from any other zone.

13. The diesel engine system according to claim 12 , wherein the at least one washcoat zone comprises a longitudinal gradient of washcoat thickness.

14. The diesel engine system according to claim 12 , wherein the at least one washcoat zone comprises a lateral gradient of washcoat thickness.

15. The diesel engine system according to claim 12 , wherein the at least one downstream catalyst zone covers the same part of the filter as the washcoat zone.

16. The diesel engine system according to claim 15 , wherein the PGM in the at least one downstream catalyst zone is carried on the particulate refractory oxide in the washcoat.

17. The diesel engine system according claim 12 , wherein the particulate refractory oxide is selected from the group consisting of bulk ceria, silica, alumina, titania, zirconia, a mixed oxide or oxides, and a composite oxide of any two or more thereof.

18. The diesel engine system according to claim 1 , wherein the first catalyst zone DOC PGM metal and the PGM metal in the at least one downstream catalyst zone is selected from the group consisting of platinum, palladium, rhodium, ruthenium, and mixtures of any two or more thereof.

19. The diesel engine system according to claim 18 , wherein a total PGM loading of the PGM metal in the first catalyst zone DOC is from 25 to 200 g/ft 3 .

20. The diesel engine system according to claim 18 , wherein a PGM loading in the at least one downstream catalyst zone is from 0.25 to 120 g/ft 3 .

21. The diesel engine system according to claim 1 , wherein the filter further comprises a catalyst for absorbing NO 2 when the exhaust gas is lean.

22. The diesel engine system according to claim 21 , wherein the engine management means, in use, intermittently provides a reduced oxygen concentration in the exhaust gas and provides higher temperature exhaust gas relative to normal running conditions for regenerating the NO 2 absorbent.

Assignees

• Twigg Martyn Vincent
• Phillips Paul Richard
• Johnson Matthey Plc

Inventors

• Twigg Martyn Vincent
• Phillips Paul Richard

Classifications

• F02D41/029

  the exhaust gas treating apparatus being a particulate filter · CPC title

• F01N3/0222

  the structure being monolithic, e.g. honeycombs · CPC title

• F01N3/035 Primary

  with catalytic reactors · CPC title

• B01D53/9495

  Controlling the catalytic process · CPC title

• B01D53/9472

  in different zones · CPC title