WO2024161111A1

WO2024161111A1 - System comprising h2-internal combustion engine and exhaust system therefor

Info

Publication number: WO2024161111A1
Application number: PCT/GB2024/050228
Authority: WO
Inventors: Kaneshalingam ARULRAJ; David Bergeal; Guy Richard Chandler; Claus Friedrich Goersmann; David Jonsson; Lukasz KUBIAK; Paul Millington; Paul Richard Phillips
Original assignee: Johnson Matthey Public Limited Company
Priority date: 2023-01-30
Filing date: 2024-01-29
Publication date: 2024-08-08

Abstract

A system comprises a hydrogen-combusting internal combustion engine (ICE) and an exhaust system for the engine comprising a H2- SCR catalyst and a urea-SCR catalyst, wherein the H2-SCR catalyst is located upstream of the urea-SCR catalyst, and further wherein a urea injection system is located downstream of the H2-SCR catalyst and upstream of the urea-SCR catalyst, wherein the H2-SCR catalyst comprises Pt and Rd loaded onto a mesoporous support..

Description

SYSTEM COMPRISING H2-INTERNAL COMBUSTION ENGINE AND EXHAUST SYSTEM THEREFOR

FIELD OF THE INVENTION

The present disclosure relates to a system comprising a hydrogen-combusting internal combustion engine (ICE) and an exhaust system for the engine.

BACKGROUND OF THE INVENTION

Hydrogen and ammonia have been proposed as alternative fuels for internal combustion engines due to potential use as renewable carbon-free energy carriers.

Pollutant emissions from H2- and NH3- ICEs are mainly nitrogen-based (i.e., NOx as the main raw emission), with potential secondary emissions being ammonia (NH3) and nitrous oxide (N2O). Carbon-based emissions (i.e., CO and hydrocarbons) can result from lubrication oil consumption but are expected to be at a very low level.

Hydrogen internal combustion engines (H2-ICE) and ammonia internal combustion engines (NH3-ICE) therefore need exhaust aftertreatment for NOx and particulate emissions (e.g., from oil ash and urea derived particulates).

Aftertreatment systems include NOx storage catalysts or SCR catalysts. Conventional SCR catalysts use ammonia/urea as the reducing agent. Urea/ammonia loading SCR systems have problems resulting from the fact that additional devices are needed to introduce urea/ammonia into the exhaust system. These problems can be overcome by generating ammonia in situ (e.g., see DE10332047), or using H2-SCR in the exhaust gas purification systems (e g., see US2008041034), but problems still remain and there is a need to provide an improved exhaust emission system for hydrogen and/or ammonia internal combustion engines.

Savva and Costa, (Catalyst Reviews: Science and Engineering 2011, 53, 91) reviews the research conducted on H2-SCR as an alternative technology to NH3- and HC-SCR, demonstrating that H2-SCR has a high NO conversion and selectivity towards N2. Deutschmann et al (Ind. Eng. Chem. Res. 2021, 60, 6613) investigates a Pd-based EE-SCR catalyst and identifies that there are a variety of challenges associated with the application of H2-SCR for NOx removal from EE-fueled internal combustion engines, which may be related to the increased amounts of water generated in a IE-fueled internal combustion engine.

Sterlepper et al (Energies, 2021, 14, 8166) describes two concepts of hydrogen-ICEs, one based on gasoline passenger car engines and the other on heavy duty diesel engines. Various options have been suggested for the concepts, but none of them have been developed. This paper describes how H2-SCR technology is still in development and therefore it is not obvious whether this technology will be viable for use with a H2-ICE engine.

Accordingly, it is an object of the present invention to provide a system comprising a hydrogen and/or ammonia-combusting engine with improved exhaust emissions, or at least to tackle problems associated therewith in the prior art, or provide a commercially viable alternative thereto.

The present inventors have surprisingly found that a system which contains both an ammonia/urea SCR catalyst and a hydrogen SCR catalyst, the overall temperature window can be widened to cover the full operational range of the engine, allowing more efficient and improved de-NOx properties.

SUMMARY OF THE INVENTION

In a first aspect, the invention relates to an exhaust system for a hydrogen and/or ammonia internal combustion engine (ICE), said exhaust system comprising a H2-SCR catalyst and a urea-SCR catalyst.

The invention also relates to a system for ammonia and/or hydrogen combustion and exhaust gas treatment, the system comprising: an internal combustion engine for combusting ammonia and/or hydrogen; and an exhaust system (e.g., an exhaust system as herein described), said exhaust system further comprising an intake for receiving an exhaust gas from the combustion engine.

In a further aspect, the invention relates to a hydrogen and/or ammonia internal combustion engine comprising an exhaust system as herein described. In a further aspect, the invention relates to a vehicle comprising an engine as herein described

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows an embodiment of the invention. Figure 2 shows an embodiment of the invention. Figure 3 shows an embodiment of the invention. Figure 4 shows an embodiment of the invention. Figure 5 shows the NOx conversion over a broad temperature window. Figure 6 shows the NOx conversion over a broad temperature window.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to an exhaust system for a hydrogen and/or ammonia internal combustion engine (ICE), said exhaust system comprising a H2-SCR catalyst and a urea-SCR catalyst.

Without wanting to be bound by theory, it is thought that the combination of using a H2-SCR catalyst and a urea-SCR catalyst results in a system that covers a wide temperature range for NOx emission control. Hydrogen can be used as a reductant in the low temperature area (e.g., from about 80°C to 180-200 °C), and urea can be used as a reductant for higher temperatures (e.g., those above 180-200 °C). The combination of the two different reductants can therefore cover a wide temperature range, allowing NOx emission control even during the cold start.

The present disclosure will now be described further. In the following passages different aspects/embodiments of the disclosure are defined in more detail. Each aspect/embodiment so defined may be combined with any other aspect/embodiment or aspects/embodiments unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. It is intended that the features disclosed in relation to the product may be combined with those disclosed in relation to the method and vice versa. As used herein, the terms “upstream” and “downstream” refer to the position of a component relative to the direction of flow of exhaust gas through the exhaust system in use.

Internal Combustion Engines

The invention relates to an exhaust system for a hydrogen and/or ammonia internal combustion engine.

In a preferred embodiment, the internal combustion engine is a hydrogen internal combustion engine.

In an alternative embodiment, the internal combustion engine is an ammonia internal combustion engine.

In a further alternative embodiment, the internal combustion engine is one where hydrogen and ammonia are both used as co-fuels.

In any of the above embodiments, alternative fuels can be used as further co-fuels, e.g., cofuels can include hydrogen, ammonia, natural gas, gasoline, diesel, ethanol, biodiesel, bioethanol or ethyl tert-butyl ether.

Urea-SCR catalyst

The urea-SCR catalyst may comprise any known urea-SCR catalysts, which are well-known in the art. As would be appreciated by a person skilled in the art, the use of aqueous urea solution as an ammonia precursor has been adopted by the automotive industry as a safe and operation adaptation of the NH3-SCR technology. Ammonia is generated in situ from ammonia decomposition. Urea-SCR and ammonia-SCR are often used interchangeably, and any reference to one of these given herein is intended to also cover the other.

Preferably, the urea-SCR catalyst is comprised of a vanadia catalyst, vanadia-titania catalyst, a vanadia-tungsta-titania catalyst, or a metal/zeolite.

The vanadia, vanadia-titania or vanada-tungsta-titania catalysts can be doped with various metals. Examples of metals used as dopants include transition metals and rare earth metals. In one embodiment, the urea-SCR catalyst can be doped with one or more of the group comprising: tungsten, antimony, molybdenum, barium, manganese, neodymium, zirconium and cerium. In a preferred embodiment, the urea-SCR catalyst can be doped with tungsten, antimony and/or molybdenum Without being bound by theory, it is thought that tungsten can extend the working temperature of the catalysts, manganese can provide high NOx removal characteristics even at low temperatures, and molybdenum can provide arsenic poisoning resistance. Cerium can also be used because of its high oxygen storage capacity and easy oxygen storage release. Zirconium can also expand the catalyst operating temperature range by inhibiting particle aggregation and improving acid site dispersibility. Antimony and neodymium can prevent catalyst poisoning by SO2 and water, and promote the decomposition of ammonium bisulfate. Barium can be used to adsorb NOx at low temperatures.

The metal/zeolite catalyst comprises a metal and a zeolite. Preferred metals include iron and copper, i.e. the urea-SCR catalyst can preferably by a Cu-SCR catalyst or a Fe-SCR catalyst. The zeolite is preferably a beta zeolite, a faujasite (such as an X-zeolite or a Y-zeolite, including NaY and USY), an L-zeolite, a ZSM zeolite (e.g., ZSM-5, ZSM-48), an SSZ- zeolite (e.g., SSZ-13, SSZ-41, SSZ-33), a ferrierite, a mordenite, a chabazite, an offretite, an erionite, a clinoptilolite, a silicalite, an aluminum phosphate zeolite (including metalloaluminophosphates such as SAPO-34), a mesoporous zeolite (e.g., MCM-41, MCM- 49, SBA-15), or mixtures thereof; more preferably, the zeolite is a beta zeolite, a ferrierite, or a chabazite. The metal (e.g. the copper or iron) can be located within the framework of the zeolite and/or in extra-framework (exchangeable) sites within the zeolite.

Alternatively, the urea-SCR catalyst can be a base metal, an oxide of a base metal, a noble metal, a molecular sieve, a metal exchanged molecular sieve or a mixture thereof. The base metal can be selected from the group consisting of vanadium (V), molybdenum (Mo), tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu), and mixtures thereof. Urea-SCR compositions comprising (e.g., consisting of) vanadium supported on a refractory metal oxide such as alumina, silica, zirconia, titania, ceria and combinations thereof are well known and widely used commercially in mobile applications. Typical compositions are described in U.S. Pat. Nos. 4,010,238 and 4,085,193. Compositions used commercially, especially in mobile applications, comprise UO2 on to which WO3 and V2O5 have been dispersed at concentrations ranging from 5 to 20 wt. % and 0.5 to 6 wt. %, respectively. The urea-SCR catalyst can comprise a promoted Ce — Zr or a promoted MnCh. Preferably, the promoter comprises Nb. The noble metal can be platinum (Pt), palladium (Pd), gold (Au) silver (Ag), ruthenium (Ru) or rhodium (Rh), or a mixture thereof. These catalysts may contain other inorganic materials such as SiC>2 and Z1O2 acting as binders and promoters.

The urea-SCR catalyst is preferably coated on a ceramic or a metallic substrate. The substrate is typically designed to provide a number of channels through which vehicle exhaust passes, and the surface of the channels will be preferably coated with the urea-SCR catalyst.

A ceramic substrate may be made of any suitable refractory material, e.g., alumina, silica, titania, ceria, zirconia, magnesia, zeolites, silicon nitride, silicon carbide, zirconium silicates, magnesium silicates, aluminosilicates and metallo-aluminosilicates (such as cordierite and spodumene), or a mixture or mixed oxide of any two or more thereof. Cordierite, a magnesium aluminosilicate, and silicon carbide are particularly preferred. A metallic substrate may be made of any suitable metal, and in particular heat-resistant metals and metal alloys such as titanium and stainless steel as well as ferritic alloys containing iron, nickel, chromium, and/or aluminum in addition to other trace metals.

The substrate for the SCR catalyst may be a filter substrate or a flow-through substrate. Preferably, the urea-SCR catalyst is coated onto a filter, which is known as a selective catalytic reduction filter (SCRF). SCRFs are single-substrate devices that combine the functionality of an SCR and particulate filter. They are used to reduce NO_X and particulate emissions from internal combustion engines.

H2-SCR catalyst

The H2-SCR catalyst may comprise any known H2-SCR catalyst, which are well-known in the art. Preferably, the H2-SCR catalyst is comprised of a precious metal loaded onto a mesoporous support, such as alumina or a zeolite.

The precious metals of the H2-SCR catalyst may be selected from one or more of the list comprising Pt, Pd, Rh, Ir, Ru, Os, Au, V or Ag. In a preferred embodiment, the precious metals of the H2-SCR catalyst are selected from Pt and/or Pd. The loading (e.g., total loading) of the precious metals in the H2-SCR catalyst can preferably be in the range of 1-50 g/ft³, e.g. from 1.5- 30 g/ft³, from 2-28 g/ft³, from 3-25 g/ft³, or from 5-20 g/ft³ The inventors have surprisingly found that using a loading (e.g., total loading) of precious metals in the H2-SCR catalyst in the range of 1-50 g/ft³ can increase the selectivity of the H2-SCR catalyst.

The average particle size of the precious metals in the H2-SCR catalyst can preferably be less than 30 nm, e.g., less than 20 nm, less than 15 nm or less than 10 nm. In a preferred embodiment, the average particle size of the of the precious metals in the H2-SCR catalyst is from 1-15 nm, from 2-12 nm, or from 5-10 nm.

Each precious metal component can be supported on the same or different mesoporous support. Each supported precious metal catalyst can be prepared separately, or multiple precious metal components can be impregnated in the same process on the same support.

The mesoporous support of the H2-SCR catalyst can be zeolitic or non-zeolitic, e.g., can be selected from alumina or zeolites.

Examples of non-zeolitic supports include, but are not limited to, high surface area refractory metal oxides. High surface area refractory metal oxide supports can comprise an activated compound selected from the group comprising (e.g., consisting of) alumina, zirconia, silica, titania, magnesia, ceria, lanthana, baria, tungsten oxide, and combinations thereof. Exemplary combinations include titania-zirconia, zirconia-tungsten oxide, titania-tungsten oxide, silica- alumina, and magnesia-ceria. In a preferred embodiment, the mesoporous support is selected from alumina, zirconia or silica, preferably alumina.

Zeolites are structures formed from alumina and silica and the SAR determines the reactive sites within the zeolite structure. Zeolites useful for the H2-SCR catalyst of the present invention may comprise a small pore zeolite (e.g., a zeolite having a maximum ring size of eight tetrahedral atoms), a medium pore zeolite (e.g. a zeolite having a maximum ring size of ten tetrahedral atoms), a large pore zeolite (e.g. a zeolite having a maximum ring size of twelve tetrahedral atoms), or a combination of two or more thereof. When the H2-SCR catalyst comprises a small pore zeolite, then the small pore zeolite may have a framework structure represented by a Framework Type Code (FTC) selected from the group comprising (e.g. consisting of) ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, LTA, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON, or a mixture and/or combination and/or an intergrowth of two or more thereof. In some embodiments, the small pore zeolite has a framework structure selected from the group comprising (e.g. consisting of) CHA, LEV, AEI, AFX, ERI, LTA, SFW, KFI, DDR and ITE. In some embodiments, the small pore zeolite has a framework structure selected from the group comprising (e.g. consisting of) CHA and AEI. The small pore zeolite may have a CHA framework structure.

When the H2-SCR catalyst comprises a medium pore zeolite, then the medium pore zeolite may have a framework structure represented by a Framework Type Code (FTC) selected from the group comprising (e g. consisting of) AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR, SZR, TER, TON, TUN, UOS, VSV, WEI and WEN, or a mixture and/or an intergrowth of two or more thereof. In some embodiments, the medium pore zeolite has a framework structure selected from the group comprising (e g. consisting of) FER, MEL, MFI, and STT. In some embodiments, the medium pore zeolite has a framework structure selected from the group comprising (e.g. consisting of) FER and MFI, particularly MFI. When the medium pore zeolite has a FER or MFI framework, then the zeolite may be ferrierite, silicalite or ZSM-5.

When the H2-SCR catalyst comprises a large pore zeolite, then the large pore zeolite may have a framework structure represented by a Framework Type Code (FTC) selected from the group comprising (e.g. consisting of) AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, or a mixture and/or an intergrowth of two or more thereof. In some embodiments, the large pore zeolite has a framework structure selected from the group comprising (e.g. consisting of) AFI, BEA, MAZ, MOR, and OFF. In some embodiments, the large pore zeolite has a framework structure selected from the group comprising (e.g. consisting of) BEA, MOR and FAU. When the large pore zeolite has a framework structure of FTC BEA, FAU or MOR, then the zeolite may be a beta zeolite, faujasite, zeolite Y, zeolite X or mordenite.

In one embodiment, the FE-SCR catalyst of the invention comprises a zeolite selected from CHA, AEI, FER, MFI, STW, BEA, FAU, Al, MAZ, MOR and OFF, preferably CHA or AEI, more preferably CHA.

The hydrogen form of the zeolite is advantageous in certain embodiments, which can be prepared by ion exchange with hydrogen according to techniques known in the art. Examples of hydrogen form zeolites include H-Y, H-Beta, H-ZSM, H-Chabazite, H-Ferri erite, H- Mordenite, and the like.

Other forms of zeolite can also be used. For example, the zeolite can be in the sodium form, calcium form, lithium form, potassium form, ammonium form or an organic counterion form.

The H2-SCR catalyst is preferably coated on a ceramic or a metallic substrate. The substrate is typically designed to provide a number of channels through which vehicle exhaust passes, and the surface of the channels will be preferably coated with the H2-SCR catalyst.

The substrate for the H2-SCR catalyst may be a fdter substrate or a flow-through substrate.

Preferably, the H2-SCR catalyst is coated onto a filter, which is known as a selective catalytic reduction filter (SCRF). SCRFs are single-substrate devices that combine the functionality of an SCR and particulate filter. They are used to reduce NO_X and particulate emissions from internal combustion engines.

In some embodiments, the H2-SCR catalyst is suitable for burning hydrogen to generate an exotherm. In order to generate an exotherm, additional hydrogen can be injected into the H2- SCR catalyst. For example, hydrogen can be injected in an amount of from 8,000 ppm- 30,000 ppm, e.g. from 10,000-20,000 ppm to generate an exotherm. The H2-SCR catalyst can bum excess hydrogen and generate an exotherm. In some embodiments, such exotherm can be utilized to allow particle regeneration of a particle filter located downstream of the H2- SCR catalyst.

In some embodiments, hydrogen is introduced into the H2-SCR catalyst in an amount of greater than 1,000 or greater than 1,500 ppm. In a preferred embodiment, hydrogen is introduced in an amount of from 1,000-10,000 ppm, e.g., from 1,500 to 8,000 ppm. In an alternative embodiment, hydrogen is introduced in an amount from 8,000 ppm-30,000 ppm, e.g., from 10,000 to 20,000 ppm.

In some embodiments, the H2-SCR catalyst can be zoned such that there is a front zone optimized for H2-SCR and a rear zone optimised for ammonia slip control. The front zone can comprise a H2-SCR catalyst as herein described and the rear zone can comprise an ASC as herein described. In a further embodiment, the resulting H2-SCR/ASC unit is coated onto a particle filter.

Exhaust System

The exhaust system comprises a H2-SCR catalyst and a urea-SCR catalyst.

In some embodiments, the exhaust system comprises additional H2-SCR catalyst(s). In some embodiments, the exhaust system comprises 2, 3 or 4 H2-SCR catalyst(s). For example, in some embodiments, the exhaust system comprises a Pt-FF SCR catalyst and a (separate) Pd- H2 SCR catalyst.

In some embodiments, the exhaust system comprises additional urea-SCR catalyst(s). In some embodiments, the exhaust system comprises 2, 3 or 4 urea-SCR catalyst(s). For example, in some embodiments, the exhaust system comprises a Cu-urea SCR catalyst and a (separate) V-urea SCR catalyst.

In a preferred embodiment, the exhaust system additionally comprises one or more of the following: a) an ammonia slip catalyst, b) a hydrogen slip catalyst, c) an oxidation catalyst, d) a particle filter, e) a urea injection system, f) a H2 injection system, g) a combined urea/H? injection system, h) a gas mixing device, i) urea and/or hydrogen storage vessel.

In some embodiments, the exhaust system comprises an ammonia slip catalyst and/or a particle filter.

In some embodiments, the exhaust system comprises a H2 and/or urea injection system.

In some embodiments, the exhaust system comprises a urea injection system and H2 injection system, a gas mixing device, a urea-SCR catalyst, a H2-SCR catalyst and optionally an ASC, preferably in the listed order. In a particularly preferred embodiment, the H2-SCR catalyst has a front zone coating for H2-SCR and a rear zone coating ASC.

In some embodiments, the exhaust system does not comprise a H2 injection system (e.g., the exhaust system does not comprise a H2 injection system either in the form of a single H2 injection system or a combined urea/H2 injection system). When the exhaust system does not comprise a H injection system, the H2 source for the H2-SCR can be from slipped H from the internal combustion engine (e.g., the H2 and/or ammonia internal combustion engine). In a preferred embodiment, when the exhaust system does not comprise a H injection system, the source of H2 is from late or post injection of H2 in the internal combustion engine.

In some embodiments, the exhaust system does not comprise a three-way catalyst (TWC). Ammonia Slip Catalyst

The exhaust system may comprise an ammonia slip catalyst (ASC). The ASC can be present in a downstream zone of the H2-SCR catalyst and/or urea-SCR catalyst, or it could alternatively or additionally be present as a separate ASC. The ASC can therefore comprise an ammonia slip catalyst formulation disposed on a substrate (i.e., a substrate that is separate to the substrate of the SCR catalysts).

As would be appreciated, the ammonia slip catalyst can also act as a hydrogen slip catalyst. It is therefore not necessary to add an additional hydrogen slip catalyst to the exhaust system of the invention.

Typically, the ammonia slip catalyst is downstream, preferably directly downstream, of the SCR catalysts. Thus, an outlet of the SCR catalysts is typically coupled (e.g., fluidly coupled) to an inlet of the ammonia slip catalyst.

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

The ASC catalyst may comprise any known ASC catalysts, which are well-known in the art. In one embodiment, the ASC of the invention can comprise a precious metal, such as platinum, palladium, rhodium, or gold on a support of one or more of titania, alumina, silica and zirconia (see, e.g., US 7,393,511). In a further embodiment, the ASC can comprise a first layer of vanadium oxide, tungsten oxide, and/or molybdenum oxide on a titania support, and a second layer of platinum on a titania support (see, e.g., U.S. Pat. Nos. 8,202,481 and 7,410,626).

Hydrogen Slip Catalyst

The exhaust system may comprise a hydrogen slip catalyst. The hydrogen slip catalyst can be present in a downstream zone of the H2-SCR catalyst and/or urea-SCR catalyst, or it could alternatively or additionally be present as a separate hydrogen slip catalyst. The hydrogen slip catalyst can therefore comprise an hydrogen slip catalyst formulation disposed on a substrate (i.e., a substrate that is separate to the substrate of the SCR catalysts). Typically, the hydrogen slip catalyst is downstream, preferably directly downstream, of the SCR catalysts. Thus, an outlet of the SCR catalysts is typically coupled (e.g., fluidly coupled) to an inlet of the hydrogen slip catalyst.

The substrate of the hydrogen slip catalyst is preferably a flow-through monolith.

The hydrogen slip catalyst may comprise any known hydrogen slip catalysts, which are well- known in the art. In one embodiment, the hydrogen slip catalyst of the invention can comprise a precious metal, such as platinum, palladium, rhodium, or gold on a support of one or more of titania, alumina, silica and zirconia.

Oxidation Catalyst

The exhaust system may comprise an oxidation catalyst. The oxidation catalyst can be present in an upstream zone of the H2-SCR catalyst and/or urea-SCR catalyst, or it could alternatively or additionally be present as a separate oxidation catalyst.

Typically, the oxidation catalyst is upstream, preferably directly upstream, of the hydrogen and/or urea injection system(s).

The oxidation catalyst may comprise any known oxidation catalysts, which are well-known in the art (see e.g., WO2014184569). In one embodiment, the oxidation catalyst comprises a precious metal (e.g., Pt, Pd, Rh, Ir, Ru, Os, Au, V or Ag) on a support material (e.g., a zeolite, titania, alumina, silica or zirconia).

Particle Filter

The particle filter can be uncatalysed (for example, no catalyst material is added), or the particle filter can be catalysed (for example, the particle filter can be coated with a SCR catalyst or an ASC, or both). The exhaust system can therefore contain a particle filter which is applied as a SCRF and/or ASCF component.

The substrate for the H2-SCR catalyst and/or urea-SCR catalyst may be a filter substrate or a flow-through substrate. Preferably, the H2-SCR catalyst and/or urea-SCR catalyst is coated onto a filter, which is known as a selective catalytic reduction filter (SCRF). SCRFs are single-substrate devices that combine the functionality of an SCR and particulate filter. They are used to reduce NO_X and particulate emissions from internal combustion engines.

In some embodiments, the urea-SCR and H2-SCR catalyst are located on one filter brick (i.e., a single filter substrate). The filter brick can comprise a front urea-SCR zone, and a rear H2- SCR zone. Alternatively, the filter brick can comprise a front urea-SCR zone, a middle H2- SCR zone and a rear ASC zone.

The particle filters may be comprised of a honeycomb body comprised of intersecting porous ceramic walls. The porous ceramic walls can define axial channels, wherein the honeycomb body further comprises plugs selectively disposed in at least some of the axial channels to further define inlet channels and outlet channels and to provide a plurality of gas flow paths through selected porous ceramic walls.

Urea Injection System

The exhaust system of the invention can comprise an injector for introducing urea into the exhaust gas. Typically, the injector is a liquid injector suitable for introducing a solution comprising urea into the exhaust gas. Urea dosing systems for SCR catalysts are known in the art.

The solution comprising urea can be an aqueous urea solution, e.g., AUS 32 (aqueous urea solution 32%), also known as AdBlue, BlueHDI, BlueTec and FLENDS (final low emission new diesel system).

In general, the injector atomizes the urea, or a solution comprising the urea, upon injection into the exhaust gas, such as by spraying the urea or the solution comprising the urea. The injector may be an airless injector or an air-assisted injector.

The injector can be configured to introduce urea into the exhaust gas upstream of the urea- SCR catalyst. It is preferred that the injector is configured to controllably introduce an amount of urea into the exhaust gas upstream of the urea-SCR catalyst. More preferably, the injector is configured to controllably introduce an amount of urea into the exhaust gas upstream of the urea-SCR catalyst to provide a molar ammonia to NO_X ratio (ANR) of from 0.7 to 1.3 (e.g., 0.9 to 1.2), such as 1.0 to 1.2 (e.g. about 1 :1). The injector can also include a mixer (e.g. a mixing device). The mixer can enable sufficient mixing of the urea before injection.

The injector for introducing urea into the exhaust gas is typically coupled, preferably fluidly coupled, to a urea storage tank. Thus, the exhaust system of the invention may further comprise urea storage tank.

H2 injection system

The exhaust system of the invention can comprise an injector for introducing hydrogen into the exhaust gas. Typically, the injector is a gaseous injector suitable for introducing hydrogen into the exhaust gas. Hydrogen dosing systems for SCR catalysts are known in the art.

The injector can be configured to introduce hydrogen into the exhaust gas upstream of the H2-SCR catalyst. It is preferred that the injector is configured to controllably introduce an amount of hydrogen into the exhaust gas upstream of the H2-SCR catalyst. More preferably, the injector is configured to controllably introduce an amount of hydrogen into the exhaust gas upstream of the H2-SCR catalyst to provide a hydrogen in an amount of greater than 1,000 or greater than 1,500 ppm. In a preferred embodiment, the injector provides hydrogen in an amount of from 1,000-10,000 ppm, e.g., from 1,500 to 8,000 ppm. In an alternative embodiment, the injector is configured to introduce hydrogen in an amount from 8,000 ppm- 30,000 ppm, e.g., from 10,000 to 20,000 ppm.

The injector can also include a mixer (e.g. a gas mixing device). The mixer can enable sufficient mixing of the hydrogen before injection.

The injector for introducing hydrogen into the exhaust gas is typically coupled, preferably fluidly coupled, to a hydrogen storage tank. Thus, the exhaust system of the invention may further comprise hydrogen storage tank.

Combined urea/H 2 injection system The exhaust system of the invention can comprise an injector for introducing a mixture of urea and H into the exhaust gas. Combined urea/hydrogen dosing systems are known in the art.

The injector can be configured to introduce urea and hydrogen into the exhaust gas upstream of the SCR catalysts. It is preferred that the injector is configured to controllably introduce an amount of urea and hydrogen into the exhaust gas upstream of the SCR catalysts.

The exhaust system may further comprise a mixer (e g. a gas mixing device), wherein the mixer is (e.g. located, such as in the exhaust gas conduit) upstream of the SCR catalysts.

The injector for introducing hydrogen and urea into the exhaust gas is typically coupled, preferably fluidly coupled, to hydrogen and urea storage tanks. Thus, the exhaust system of the invention may further comprise hydrogen storage tank and a urea storage tank.

Urea and/or storage vessels

Preferably the system further comprises a urea storage vessel and/or a hydrogen storage vessel. The urea may be provided in a number of different forms and the type of storage required will depend on the form of urea provided. For example, it may be provided as a solid or a solution. In these instances, the storage requirements may differ. Suitable urea storage systems are well known in the art.

The hydrogen may similarly be provided in a number of different forms. For example, it may be provided as a compressed gas, or may be adsorbed onto a material. Alternatively, the hydrogen may be stored as part of a solid, such as a lithium metal halide. Heat treatment of the solid can be used to liberate hydrogen as required.

Exhaust System Configurations

As would be appreciated by a person skilled in the art, the following configurations are not limiting on the invention. The following configurations can comprise additional features which are not specifically mentioned or depicted in their corresponding figures. For example, Hz and/or urea injection systems can be included in any of the following configurations. Alternatively or additionally, a filter can be included in any of the following configurations. In a preferred embodiment, the exhaust system comprises a combined H2 and urea injection system upstream of a urea-SCR catalyst and H2-SCR catalyst (see Figure 1).

The urea-SCR catalyst and H2-SCR catalyst can be in any order, but in a particularly preferred embodiment, the urea-SCR catalyst is upstream of the H2-SCR catalyst (as depicted in Figure 1).

In a preferred embodiment, the urea injection system and hydrogen injection system are located upstream of a urea-SCR catalyst and a H2-SCR catalyst, wherein the urea-SCR catalyst is additionally located upstream of the H2-SCR catalyst.

In a particularly preferred embodiment, the urea injection system is located upstream of the urea-SCR catalyst in such a way that the H2-SCR catalyst is not located between the urea injection system and the urea-SCR catalyst.

In another preferred embodiment, the ASC and/or filter units are located downstream of the urea-SCR catalyst and H2-SCR catalyst. Figure 2 depicts the embodiment where the ASC and filter units are located downstream of the urea-SCR catalyst and H2-SCR catalyst (see Figure 2). In this embodiment, the urea-SCR catalyst and H2-SCR catalyst can be in any order, i.e., the urea-SCR catalyst can be upstream or downstream of the H2-SCR catalyst.

In a particularly preferred embodiment, the urea injection system and H2 injection system are located downstream of a gas mixing device, a urea-SCR catalyst and a H2-SCR catalyst. An optional ASC is located downstream of the SCR catalysts (see Figure 3).

In an alternative embodiment, the H2-SCR catalyst is located upstream of the urea-SCR catalyst. The urea injection system is located upstream of the urea-SCR catalyst, and downstream of the H2-SCR catalyst (see Figure 4).

The invention also relates to a system for ammonia and/or hydrogen combustion and exhaust gas treatment, the system comprising: an internal combustion engine for combusting ammonia and/or hydrogen; and an exhaust system (e.g. an exhaust system as herein described), said exhaust system further comprising an intake for receiving an exhaust gas from the combustion engine.

ICE/Vehicle

In a further aspect, the invention relates to a hydrogen and/or ammonia internal combustion engine comprising an exhaust system as herein described

The invention further provides a vehicle. The vehicle comprises a hydrogen and/or ammonia internal combustion engine and an exhaust system of the invention.

In some embodiments, the invention is related to a passenger vehicle and/or a heavy duty vehicle. In a preferred embodiment, the invention is related to passenger vehicles.

The following examples merely illustrate the invention. Those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims.

The invention can also be defined according to one or more of the following statements of invention:

1. An exhaust system for a hydrogen and/or ammonia internal combustion engine (ICE), said exhaust system comprising a H2-SCR catalyst and a urea-SCR catalyst.

2. The exhaust system of 1, further comprising an ammonia slip catalyst and/or a particle filter, preferably wherein the ammonia slip catalyst and/or particle filter are located downstream of the H2-SCR and urea-SCR catalysts.

3. The exhaust system of 1 or 2, wherein the H2-SCR catalyst is zoned such that there is a front zone optimised for H2-SCR and a rear zone optimised for ammonia slip control, preferably wherein the resulting H2-SCR/ASC unit is coated onto a particle filter.

4. The exhaust system of 1, 2 or 3, wherein the urea-SCR catalyst is located upstream of the H2-SCR catalyst. 5. The exhaust system of 1, 2, 3 or 4 further comprising a H?/urea injection system, preferably wherein said fb/urea injection system is located upstream of the H -SCR and urea- SCR catalysts.

6. The exhaust system of any one of 1 to 5, wherein the H2-SCR catalyst burns hydrogen and generates an exotherm, preferably wherein said exotherm allows particle regeneration of a particle filter unit located downstream of the H2-SCR catalyst.

7. The exhaust system of any of 1 to 6, wherein the exhaust system comprises a urea injection system and H2 injection system, a gas mixing device, a urea-SCR catalyst, a H2- SCR catalyst and optionally an ASC, preferably in the listed order.

8. The exhaust system of 7, wherein the H2-SCR catalyst has a front zone coating for H2- SCR and a rear zone coating ASC.

9. The exhaust system of 1 to 8, wherein the urea-SCR and H2-SCR catalyst are located on one filter brick, which comprises a front urea-SCR zone, a middle H2-SCR zone and a rear ASC zone.

10. The exhaust system of any one of 1-3 and 5-8, wherein the H2-SCR catalyst is located upstream of the urea-SCR catalyst, and further wherein a urea injection system is located downstream of the H2-SCR catalyst and upstream of the urea-SCR catalyst.

11. The exhaust system of any one of 1 to 10, wherein the exhaust system does not comprise a separate H2 injection system, preferably wherein the H2 source for the H2-SCR is from slipped H2 from the fb-internal combustion engine, more preferably wherein the source of H2 is from late or post injection of H2 in the internal combustion engine.

12. The exhaust system of any one of 1 to 11, wherein the exhaust system contains a particle filter which is applied as a SCRF or ASCF component.

13. The exhaust system of any one of 1 to 12, wherein the exhaust system is for a hydrogen internal combustion engine. 14. A hydrogen and/or ammonia internal combustion engine comprising an exhaust system as described in any one of 1 to 13.

15. A vehicle comprising a hydrogen and/or ammonia internal combustion engine and an exhaust system as described in any one of 1 to 13.

EXAMPLES

In order that the invention may be more fully understood, the following Examples are provided by way of illustration only and with reference to the accompanying Figures.

Example 1

The NOx conversion was measured at different temperatures for a Pd/EE-SCR catalyst, a Pt/FE-SCR catalyst, and a Cu-zeolite NEE SCR catalyst. The results from the NOx conversion test were measured at a series of steady state points, i.e., NOx conversion was measured at first temperature point and the measurement repeated at each temperature point, as shown in Figure 5. The results show that the combination of using the two F -SCR catalysts and a NEE SCR catalyst provides a much broader temperature window for NOx conversion, compared to only using one of these catalysts.

Example 2

The NOx conversion was measured at different temperatures for a Pd-Pt/FE-SCR catalyst and a Cu-zeolite NEE SCR catalyst. The results from the NOx conversion test were measured at a series of steady state points, i.e., NOx conversion was measured at first temperature point and the measurement repeated at each temperature point, as shown in Figure 6. The results show that the combination of using the FE-SCR catalyst and a NEE SCR catalyst provides a much broader temperature window for NOx conversion, compared to only using one of these catalysts.

For the avoidance of any doubt, the entire content of any and all documents cited herein is incorporated by reference into the present application.

Claims

CLAIMS:

1. A system comprising a hydrogen-combusting internal combustion engine (ICE) and an exhaust system for the engine, said exhaust system comprising a H2-SCR catalyst and a urea-SCR catalyst, wherein the H2-SCR catalyst is located upstream of the urea-SCR catalyst, and further wherein a urea injection system is located downstream of the H2-SCR catalyst and upstream of the urea-SCR catalyst, wherein the H2-SCR catalyst comprises Pt and Pd loaded onto a mesoporous support.

2. The system according to claim 1, wherein a total loading of Pt and Pd in the H2-SCR catalyst is in the range of 1-50 g/ft³.

3. The system according to claim 1 or 2, wherein the mesoporous support is a non- zeolitic support selected from the group consisting of alumina, zirconia, silica, titania, magnesia, ceria, lanthana, baria, tungsten oxide, and combinations thereof, preferably alumina.

4. The system according to claim 1 or 2, wherein the mesoporous support is a zeolitic support comprising a small pore zeolite having a maximum ring size of eight tetrahedral atoms, a medium pore zeolite having a maximum ring size of ten tetrahedral atoms, a large pore zeolite having a maximum ring size of twelve tetrahedral atoms, or a combination of two or more thereof.

5. The system according to any one of the preceding claims, wherein the exhaust system further comprises an ammonia slip catalyst and/or a particle fdter, wherein the ammonia slip catalyst and/or particle filter are located downstream of the H2-SCR and urea-SCR catalysts.

6. The system according to any one of the preceding claims, wherein the H2-SCR catalyst is zoned such that there is a front zone optimised for H2-SCR and a rear zone optimised for ammonia slip control, preferably wherein the resulting H2-SCR/ASC unit is coated onto a particle filter.

7. The system according to any one of the preceding claims, wherein the exhaust system further comprises a H /urea injection system, preferably wherein said fb/urea injection system is located upstream of the H2-SCR and urea-SCR catalysts

8. The system according to any one of the preceding claims, wherein the H2-SCR catalyst burns hydrogen and generates an exotherm, preferably wherein said exotherm allows particle regeneration of a particle filter unit located downstream of the H2-SCR catalyst.

9. The system according to any one of the preceding claims, wherein the exhaust system comprises in the listed order a urea injection system and H2 injection system, a gas mixing device, a urea-SCR catalyst, a H2-SCR catalyst and optionally an ASC.

10. The system according to claim 9, wherein the H2-SCR catalyst has a front zone coating for H2-SCR and a rear zone coating ASC.

11. The system according to any one of the preceding claims, wherein the urea-SCR and H2-SCR catalyst are located on one filter brick, which comprises a front urea-SCR zone, a middle H2-SCR zone and a rear ASC zone.

12. The system according to any one of the preceding claims, wherein the exhaust system does not comprise a separate H2 injection system, wherein the H2 source for the H2-SCR is from slipped H2 from the H?-internal combustion engine, preferably wherein the source of H2 is from late or post injection of H2 in the internal combustion engine.

13. The system according to any one of the preceding claims, wherein the exhaust system contains a particle filter which is applied as a SCRF or ASCF component.

14. A vehicle comprising the system according to any one of the preceding claims.