EP1688608A1 - EGR system - Google Patents

Abstract

The system has a gaseous flux connection (105) extended between exhaust and air inlet manifolds (12, 11) of a combustion chamber of an internal combustion engine. A hydrogen reformer (200) is disposed on the connection and has a catalytic module (250) adapted to create a fuel steam reforming reaction. The module has a catalytic block maintained at a temperature ranging of 800-850[deg]C. An independent claim is also included for a motor vehicle comprising an internal combustion engine having an exhaust gas recirculation system.

Description

The present invention relates to an exhaust gas recirculation circuit. Such a circuit can be used in an internal combustion engine, such as a motor vehicle engine.

In an internal combustion engine, the four stages of the thermodynamic cycle - admission of fuel gas and air, compression of the gas mixture, expansion due to the explosion of the mixture, exhaust - take place successively in one and the same enclosure, so-called combustion chamber. The gases introduced into this combustion chamber consist on the one hand of air and on the other hand of gasoline or gas oil, in proportions proportionally dosed according to the engines and ignition systems used. The gas mixture is then ignited in the combustion chamber.

It is known for spark ignition and compression ignition engines to recirculate the exhaust gases to the combustion chamber air inlet to reduce nitrogen oxide (NO) emissions. _x ). Such a system is known by the Anglo-Saxon acronym EGR for "Exhaust Gas Recirculation".

Figure 1 schematically illustrates the principle of an EGR system. An internal combustion engine comprises one or more combustion chambers 10 located between an intake manifold 11 and an exhaust manifold 12. The intake manifold 11 receives air A to be introduced into the combustion chamber 10. A fuel injection is also introduced into the combustion chamber, generally by an injection nozzle (not shown). The exhaust manifold 12 receives the emissions of gas produced by the combustion and directs them to an exhaust catalyst 13 adapted to treat the fumes before their expulsion to the outside atmosphere, in a manner known per se.

FIG. 1 also shows an exhaust gas recirculation circuit 100. This EGR circuit constitutes a connection 105 between the exhaust manifold 12 and the intake manifold 11 and comprises a regulation valve 101 at the input of the circuit 100. It is indeed necessary to precisely control the flow rate of the exhaust gases reintroduced into the combustion chamber 10. A too high flow rate causes a loss of engine power and causes acceleration blows, while a flow too much. low leads to over-emission of nitrogen oxides.

The recirculation circuit 100 also comprises a cooler 102, such as a tube heat exchanger exchanging with the coolant of the motor, so as not to introduce too hot gases in the combustion chamber 10, which would result in a loss of volumetric efficiency.

EGR systems were introduced in the 1970s to reduce the nitrogen oxide emissions formed when the temperature in the combustion chamber becomes too high. Above 1300 ° C, the nitrogen and oxygen atoms can combine with each other in the combustion chamber to form nitrogen oxide (NO _x ) molecules which, combined with hydrocarbon molecules ( HC _x ) in the presence of sun, produce a polluting fog, known as "smog".

The amount of nitrogen oxide can be reduced by reducing the combustion temperature, in particular by recirculating exhaust gases into the combustion chamber. Indeed, the exhaust gases have already burned and are rich in di-nitrogen (N ₂ ) and carbon dioxide (CO ₂ ). The recirculated exhaust gas thus dilutes the fuel charge, resulting in slowing and cooling of the combustion.

However, the recirculation of exhaust gases produces an increase in emissions of carbonaceous products, such as unburned hydrocarbons (HC) and carbon monoxide (CO), or particulates (PM, for Particle Matter in English).

To overcome this drawback, it has been shown that an addition of hydrogen-rich gas (H ₂ ) in the intake manifold of the combustion chamber, during a recirculation of the exhaust gas, reduces emissions unburned hydrocarbons (HC), carbon monoxide (CO) and soot.

US-A-4 175 523 proposes an internal combustion engine with an EGR system and a catalytic reforming system of the fuel. When the engine is running at low speed, the combustion chamber receives only the air / fuel mixture and the exhaust gas recirculation. During low speed operation, the EGR system is flanged, i.e. it can only provide a recirculated exhaust gas flow rate limited to a predetermined value. When the engine is running at high speed the reformed fuel, rich in free hydrogen, is added to the air / fuel mixture and to the recirculation of the exhaust gas. During high speed operation, the EGR system provides a recirculated exhaust gas flow rate greater than said predetermined value.

The power output of the engine is thus improved while limiting the emissions of carbon products.

• reformage par oxydation partielle du carburant (composition C_xH_y) avec de l'air (O₂ + 3,76N₂), le carburant étant introduit sous forme de vapeur :
  
           C_xHy + x/2 (O₂ + 3,76N₂) → x CO + y/2 H₂ + 1,88xN₂     (1)
  
  
• vapo-reformage du carburant (C_xH_y) avec de la vapeur d'eau (H₂O) :
  
           C_xH_y + x H₂O → x CO + (y/2 + x) H₂     (2)
  
  
• réaction de gaz à l'eau, dite « Water Gas Shift reaction » :
  
           CO + H₂O → CO₂ + H₂     (3)
  
  

In a manner known in itself, reforming the fuel is obtained by reacting fuel molecules with water and / or air to produce hydrogen, according to the following chemical reactions:

• reforming by partial oxidation of the fuel (composition C _x H _y ) with air (O ₂ + 3.76N ₂ ), the fuel being introduced in the form of steam:
  
  C _x Hy + x / 2 (O ₂ + 3.76N ₂ ) → x CO + y / 2H ₂ + 1.88xN ₂ (1)
  
  
• vapo-reforming the fuel (C _x H _y ) with water vapor (H ₂ O):
  
  C _x H _y + x H ₂ O → x CO + (y / 2 + x) H ₂ (2)
  
  
• gas reaction to water, called "Water Gas Shift reaction":
  
  CO + H ₂ O → CO ₂ + H ₂ (3)
  
  

Avoiding the methanation reaction, hydrogen-consuming

CO + 2H ₂ → CH ₄ + 1/2 O ₂

This methanation reaction can be avoided by promoting the reaction of gas with water which removes CO, for example by placing in excess of water.

The most efficient reforming reaction for producing hydrogen is the steam reforming reaction which has the highest efficiency. This vapo-reforming reaction is favored by high temperatures and an excess of water vapor.

Thus, document FR-A-2 839 583 describes a fuel cell installation for a motor vehicle comprising, in addition to the internal combustion engine, a fuel cell operating with a fluid containing hydrogen. The hydrogen necessary for the proper functioning of the fuel cell is generated on board the vehicle, using a reformer. The reformer is adapted to provide a hydrogen enriched fluid from a mixture containing hydrocarbons.

The document FR-A-2 839 583 proposes placing a heat exchanger on the exhaust gas duct of the internal combustion engine to heat a heat transfer fluid intended to heat the reformer. The thermal energy required for an optimal reforming reaction is therefore provided by the heat of the exhaust gas.

However, this document FR-A-2 839 583 does not describe any EGR system associated with the internal combustion engine.

Moreover, the dual system of EGR and fuel reforming described in US-A-4 175 523 cited above is complex and cumbersome. Indeed, the two systems comprise separate gas flow circuits from one another. In particular, the reformed gas rich in hydrogen is stored in a tank and introduced into the intake manifold of the combustion chamber only when the engine exceeds a certain speed, while the exhaust gas is recirculated in the combustion chamber. regardless of the operating speed of the engine.

There is therefore a need for a recirculation circuit associated with a fuel reforming circuit which is of simplified design and more compact.

• une liaison de flux gazeux adaptée à s'étendre entre un collecteur d'échappement et un collecteur d'admission d'air d'une chambre de combustion du moteur ;
• un reformeur d'hydrogène disposé sur la liaison de flux gazeux.

For this purpose, the invention proposes an exhaust gas recirculation circuit of an internal combustion engine, comprising:

• a gas flow connection adapted to extend between an exhaust manifold and an air intake manifold of a combustion chamber of the engine;
• a hydrogen reformer disposed on the gas flow connection.

• la liaison de flux gazeux présente une entrée constituée par une dérivation du collecteur d'échappement ;
• la liaison de flux gazeux présente une sortie comprenant une vanne de régulation du flux ;
• le circuit comprend un refroidisseur disposé en aval du reformeur ;
• le reformeur comprend un mélangeur adapté à recevoir le flux gazeux, une injection de carburant et une injection d'eau ; et au moins un premier module catalytique adapté à provoquer une réaction de reformage du carburant ;
• le reformeur comprend en outre un évaporateur adapté à recevoir une injection de carburant et une injection d'eau et adapté à fournir au mélangeur le carburant et l'eau sous forme de vapeurs ;
• le circuit comprend un échangeur de chaleur adapté à chauffer l'évaporateur, ledit échangeur comprenant des conduites de circulation d'un fluide caloporteur constitué au moins en partie par le flux gazeux ;
• le circuit présente un obstacle disposé sur la liaison de flux gazeux en amont du premier module catalytique ;
• le mélangeur est adapté à recevoir en outre une injection d'air ;
• le reformeur comprend en outre un second module catalytique adapté à provoquer une réaction de gaz à l'eau ;
• la liaison de flux gazeux présente une entrée de vapeur d'eau située entre le premier et le second module catalytique ;
• le premier module catalytique comprend au moins un parmi les catalyseurs du groupe : Ru, W, Rh, Ir, Ni, Co, Os, Pt, Fe, Mo, Pd, Ag ;
• le second module catalytique comprend un premier pain catalytique comprenant au moins un parmi les catalyseurs du groupe : Pt, Fe203, FeCr ; et un second pain catalytique comprenant au moins un parmi les catalyseurs du groupe : Pt, CuO/ZnO ;

According to the embodiments, the recirculation circuit according to the invention also has one or more of the following characteristics:

• the gas flow connection has an inlet constituted by a bypass of the exhaust manifold;
• the gas flow connection has an output comprising a flow control valve;
• the circuit comprises a cooler disposed downstream of the reformer;
• the reformer comprises a mixer adapted to receive the gas flow, a fuel injection and a water injection; and at least a first catalytic module adapted to cause a reforming reaction of the fuel;
• the reformer further comprises an evaporator adapted to receive a fuel injection and a water injection and adapted to supply the mixer with fuel and water in the form of vapors;
• the circuit comprises a heat exchanger adapted to heat the evaporator, said exchanger comprising circulation pipes for a coolant constituted at least in part by the gas stream;
• the circuit has an obstacle disposed on the gas flow connection upstream of the first catalytic module;
• the mixer is adapted to further receive an air injection;
• the reformer further comprises a second catalytic module adapted to cause a gas reaction to water;
• the gas flow connection has a water vapor inlet located between the first and the second catalytic module;
• the first catalytic module comprises at least one of the group: Ru, W, Rh, Ir, Ni, Co, Os, Pt, Fe, Mo, Pd, Ag;
• the second catalytic module comprises a first catalytic bread comprising at least one of the catalysts of the group: Pt, Fe 2 O 3, FeCr; and a second catalytic bread comprising at least one of the catalysts of the group: Pt, CuO / ZnO;

• une chambre de combustion ;
• un collecteur d'admission d'air ;
• un collecteur d'échappement ;
• un circuit de recirculation selon l'invention.

The invention also relates to an internal combustion engine comprising:

• a combustion chamber;
• an air intake manifold;
• an exhaust manifold;
• a recirculation circuit according to the invention.

• des moyens adaptés à prélever une partie de l'hydrogène produit par le reformeur du circuit de recirculation ;
• une pile à combustible alimentée au moins en partie par de l'hydrogène prélevé du circuit de recirculation ;
• un module de post-combustion à l'échappement adapté à être chauffé par une alimentation en hydrogène prélevé du circuit de recirculation ;
• des pièges à oxyde d'azote (NOx) à l'échappement, lesdits pièges étant adaptés à être régénérés au moins en partie par de l'hydrogène prélevé du circuit de recirculation ;
• une unité de contrôle adaptée à commander une vanne de régulation du flux gazeux dans le circuit de recirculation ;
• l'unité de contrôle est adaptée à réguler une injection de carburant et une injection d'eau dans le reformeur du circuit de recirculation ;
• l'unité de contrôle est adaptée à réguler une injection d'air dans le reformeur du circuit de recirculation ;

According to the embodiments, the engine according to the invention also has one or more of the following characteristics:

• means adapted to withdraw a portion of the hydrogen produced by the reformer of the recirculation circuit;
• a fuel cell powered at least in part by hydrogen taken from the recirculation circuit;
• an exhaust afterburner module adapted to be heated by a hydrogen supply taken from the recirculation circuit;
• nitrogen oxide (NOx) traps at the exhaust, said traps being adapted to be regenerated at least in part by hydrogen taken from the recirculation circuit;
• a control unit adapted to control a gas flow control valve in the recirculation circuit;
• the control unit is adapted to regulate a fuel injection and a water injection into the reformer of the recirculation circuit;
• the control unit is adapted to regulate an injection of air into the reformer of the recirculation circuit;

The invention applies to motor vehicles comprising an engine according to the invention.

• figure 1, déjà décrite, un schéma d'un circuit de recirculation des gaz d'échappement selon l'art antérieur ;
• figure 2, un schéma d'un circuit de recirculation des gaz d'échappement selon l'invention.

Other features and advantages of the invention will appear on reading the following detailed description of the embodiments of the invention, given by way of example only and with reference to the drawings which show:

• FIG. 1, already described, a diagram of an exhaust gas recirculation circuit according to the prior art;
• FIG. 2 is a diagram of an exhaust gas recirculation circuit according to the invention.

The exhaust gas recirculation circuit according to the invention comprises a gas flow connection adapted to extend between an exhaust manifold and an air intake manifold of a combustion chamber of an engine. The recirculation circuit also comprises a hydrogen reformer disposed on the gas flow connection.

Thus, the EGR circuit provides the air intake manifold of the combustion chamber a recirculating gas enriched in hydrogen. The hydrogen enrichment of the gas mixture supplied to the air intake manifold does not come from a system separate from the EGR circuit, but from the EGR circuit itself. An improved EGR system is thus provided by the present invention.

The recirculation circuit according to the invention is described with reference to FIG.

The elements identical to those illustrated in Figure 1 have the same reference numbers.

In particular, Figure 2 shows a combustion chamber 10 located between an intake manifold 11 and an exhaust manifold 12; an exhaust catalyst 13; an air inlet A.

Figure 2 also shows the exhaust gas recirculation circuit. This EGR circuit comprises a connection 105 of gas flow which extends between the exhaust manifold 12 and the intake manifold 11. The gas flow connection 105 has an inlet 106 consisting of a simple bypass of the exhaust manifold 12 In particular, no control valve is provided at the inlet 106 of the gas flow connection because it is sought to maintain a maximum of heat in the connection. The gas flow link has an output 107 which includes a flow control valve 101. The flow control of the recirculated gases in the combustion chamber 10 is ensured at the end of the connection.

Indeed, the recirculation circuit according to the invention further comprises a hydrogen reformer 200 disposed on the connection 105 of gas flow. However, for optimum efficiency of reforming the fuel in hydrogen, it is necessary to conduct the reforming chemical reactions at high temperature. Thus, the lime exhaust gases taken at the inlet 106 of the gas flow connection must not be cooled before having passed through the reformer 200. Any control valve, which would introduce an adiabatic expansion of the gas flow, is therefore proscribed at the entrance 106 of the link.

The EGR circuit according to the invention may comprise a cooler 102 disposed downstream of the reformer 200. The vapo-reforming reaction is highly endothermic, the gas flow can be considerably cooled at the outlet of the reformer. A cooler may nevertheless be provided, possibly sized for a cooling efficiency less than that of Figure 1 of the prior art.

The reformer 200 comprises a mixer 210 which receives the gas stream flowing in the connection 105, that is to say hot gases from the combustion chamber exhaust, mainly water (H ₂ O) , dioxide carbon (CO ₂ ), traces of pollutants (CO, HC, soot, NO _x ) and air (O ₂ + 3.76N ₂ ) if the combustion was in excess of air.

The reformer 200 also comprises an injection system for introducing into the mixer 210 finely atomized fuel F and water W. It is preferable that the fuel F and the water W are injected into the mixer in the form of vapors. Thus, the fuel and water can be injected in liquid form, which is the form in which they are stored, in an evaporator 220 coupled to the mixer 210 to provide the fuel and water in the form of vapors. For this purpose, a heat exchanger 130 may be provided for heating the evaporator 220. This exchanger 130 may comprise pipes circulating a portion of the gas derived from the inlet exhaust 106 of the connection. At this level of the connection, the gas is very hot, of the order of 400 to 500 ° C, and can be used in all or part of heat transfer fluid to heat the evaporator 220 to vaporize the water and the fuel. inject into the mixer 210.

The reformer 200 also comprises at least a first catalytic module 250 adapted to cause a vapor reforming reaction of the fuel. An obstacle may be disposed on the gas flow connection 105 upstream of the first catalytic module 250 to make the flow of the gaseous flow turbulent and thus promote the mixing of the gases. In particular, the obstacle may be placed upstream of the mixer 210 to render the gaseous flow of the exhaust gas taken into the mixer turbulent, this turbulence being sufficient to mix the gas flow with the injected fuel and water vapors. in the mixer.

The first catalytic module 250 comprises a catalytic bread held at a temperature of between 600 ° C. and 1000 ° C., preferably between 800 ° C. and 850 ° C. and adapted to cause a vapor reforming reaction according to equation (2). previously mentioned. The catalysts promoting the vapo-reforming reaction are, in a decreasing order of effectiveness, Ru, W, Rh, Ir, Ni, Co, Os, Pt, Fe, Mo, Pd, Ag.

The reformer 200 may also comprise a second catalytic module 260 adapted to cause a reaction of gas with water according to the reaction (3) mentioned above. The steam required for this second reforming reaction can come from an excess of water vapor introduced into the mixer or can come from a new injection of water vapor taken from the evaporator 220. gas flow connection 105 may then have a water vapor inlet 108 located between the first and the second catalytic module 250, 260.

• Pt, Fe203, FeCr. Une seconde étape comporte une réaction se déroulant à basse température, de l'ordre de 220°C avec un second pain catalytique comprenant au moins un parmi les catalyseurs du groupe : Pt, CuO/ZnO.

The reaction of the gas with water takes place in two stages. A first step comprises a reaction taking place at high temperature, of the order of 450 ° C with a first catalytic bread comprising at least one of the catalysts of the group:

• Pt, Fe 2 O 3, FeCr. A second step comprises a reaction taking place at low temperature, of the order of 220 ° C with a second catalytic bread comprising at least one of the catalysts of the group: Pt, CuO / ZnO.

The EGR circuit according to the invention operates as follows.

Part of the gases from the exhaust of the combustion chamber 10 are derived in an EGR circuit link 105 allowing the recirculation of the exhaust gas to the intake manifold of the combustion chamber.

A control unit (not shown) of the reformer 200 is provided. This control unit is generally connected to a control unit of the engine speed and in particular to a control unit adapted to control the gas flow control valve in the recirculation circuit. This valve determines the amount of recirculated exhaust gas introduced into the intake manifold of the combustion chamber. However, the amount of recirculated gas will determine the amount of gaseous mixture enriched in hydrogen to be added, that is to say the amount of fuel to reform.

The control unit also controls the injection of water and fuel into the mixer 210 to provide the necessary ingredients for the steam reforming reaction in the first catalytic module 250. The exhaust gases are also introduced into the engine. mixer 210 and then pass through the first catalytic module 250; the thermal energy of the exhaust gas is thus used to allow optimum performance of the fuel reforming reaction.

The control unit also controls the injection of steam upstream of the second catalytic module 260 to complete the hydrogen generation by oxidizing the carbon monoxide from the steam reforming.

The gases taken from the exhaust manifold 12 therefore circulate in the reformer 200. These exhaust gases mix with the fuel and water injections to form the ingredients necessary for the reforming reactions to provide a directly enriched exhaust gas. in hydrogen.

It should be noted that in order to control the composition of the gases at the inlet of the EGR circuit, the engine injection system must have dedicated settings. In particular, the amount of oxygen present in the EGR circuit depends on the combustion in the engine, that is to say if it is in excess or not. A late fuel injection into the cycle can also be used to increase the temperature of the exhaust gases and thus the temperature levels in the EGR circuit. It will also be possible to inject fuel during the exhaust phase of the engine cycle to produce fuel enrichment of the EGR circuit and thus of the mixture introduced into the reformer.

In addition, the exhaust gases provide the thermal energy necessary for the smooth running of the reforming reactions.

Indeed, the vapo-reforming reaction is highly endothermic. It is therefore necessary that the exhaust gases are hot enough to guarantee the reaction. This constraint implies that the reformer placed on the EGR link can only operate when the engine is hot enough, the control unit preventing the injection of fuel and water until the engine has reached a temperature predetermined.

To overcome this drawback, it is possible to promote a partial oxidation reforming reaction in the reformer according to the reaction (1) previously mentioned, this reaction being exothermic. For this purpose, it is then necessary to provide a system for blowing air into the mixer before the injection of fuel and water, for example an electric air pump. A system for initiating the partial oxidation reaction must also be provided upstream of the first catalytic module, for example a spark plug. It is also possible to choose a sufficiently reactive catalyst in the first module, such as platinum (Pt). The air pump and the spark plug can be controlled by the control unit.

Thus, with an air injection into the reformer, it is then possible to produce hydrogen at any time of the engine operation, including when the engine is still cold. The reformer is then thermally autonomous. The thermal energy required for the vapo-reforming reaction is provided by the partial oxidation reaction.

In normal operation of the engine, the air injection can also make it possible to control the temperature levels in the EGR circuit, in particular when the thermal energy of the exhaust gases is not sufficient. The partial oxidation reforming reaction is however less effective than the steam reforming reaction, the latter will be preferred by adjusting the flow of air blown into the mixer at its bare minimum.

It is thus possible to operate engine components powered by this production of hydrogen, such as, for example, the heating of the aftertreatment units of the exhaust gases to bring them to a nominal temperature before starting the engine or the engine. supply of nitrogen oxide (NOx) traps to the exhaust, said traps being adapted to be regenerated at least partly by hydrogen.

For this purpose, a hydrogen collection system provided by the reformer, out of the EGR circuit, can be provided. For example, the sampling can be performed at the control valve 101 which then directs the reformed stream, called reformate, either in the intake manifold of the engine 11, or in a secondary circuit in the vehicle where the reformate will be used by other bodies.

Hydrogen taken from the reformer out of the EGR circuit can be used for other purposes, such as for example a fuel cell power supply providing power to the vehicle accessories.

The introduction of hydrogen-enriched recirculated gases allows in particular engine operation with high levels of EGR while reducing nitrogen oxide emissions and maintaining relatively low levels of carbon product emissions (CO, HC ) and particles.

Of course, the present invention is not limited to the embodiments described by way of example; thus, the fuel injection settings, water, air and amount of recirculated gas are determined by a person skilled in the art according to the intended applications.

Claims (19)

Internal combustion engine comprising: - a combustion chamber (10); an air intake manifold (11); an exhaust manifold (12); a gas flow connection (105) having an inlet (106) constituted by a simple bypass of the exhaust manifold (12) and extending between the exhaust manifold and the intake manifold for the recirculation of the gases exhaust system, said link comprising a mixer (210) adapted to receive the flow of the recycled exhaust gas as well as the water and fuel supplied in the form of vapors, and at least a first catalytic module (250) adapted to to provoke a vapor reforming reaction of the fuel in hydrogen. Engine according to claim 1, characterized in that the gas flow connection (105) has an outlet (107) comprising a flow control valve (101). Engine according to one of claims 1 to 2, characterized in that it comprises a cooler (102) arranged downstream of the catalytic module. Engine according to one of claims 1 to 3, characterized in that it further comprises an evaporator (220) adapted to receive a fuel injection (F) and a water injection (W) and adapted to provide the mixer (210) fuel and water as vapors (V). Engine according to claim 4, characterized in that it comprises a heat exchanger (130) adapted to heat the evaporator (220), said exchanger (130) comprising heat transfer fluid circulation ducts constituted at least in part by the gas flow. Engine according to one of claims 1 to 5, characterized in that it comprises an obstacle disposed on the gas flow connection upstream of the first catalytic module (250). Engine according to one of claims 1 to 6, characterized in that the mixer (210) is adapted to further receive an air injection. Engine according to one of claims 1 to 7, characterized in that the reformer (200) further comprises a second catalytic module (260) adapted to cause a gas reaction to water. An engine according to claim 8, characterized in that the gas flow connection (105) has a steam inlet (108) between the first and second catalytic modules (250, 260). Engine according to any one of the preceding claims, characterized in that the first catalytic module (250) comprises at least one of the catalysts of the group: Ru, W, Rh, Ir, Ni, Co, Os, Pt, Fe, Mo , Pd, Ag. Engine according to one of claims 9 to 10, characterized in that the second catalytic module (260) comprises a first catalytic bread comprising at least one of the catalysts of the group: Pt, Fe ₂ O ₃ , FeCr; and a second catalytic bread comprising at least one of the catalysts of the group: Pt, CuO / ZnO. Engine according to any one of the preceding claims, characterized in that it comprises means adapted to withdraw a portion of the hydrogen produced by the reformer of the exhaust gas recirculation circuit. Engine according to Claim 12, characterized in that it comprises a fuel cell fed at least in part by hydrogen taken from the exhaust gas recirculation circuit. Engine according to Claim 12, characterized in that it comprises an exhaust afterburner module adapted to be heated by a hydrogen supply taken from the exhaust gas recirculation circuit. Engine according to Claim 12, characterized in that it comprises nitrogen oxide (NOx) traps at the exhaust, said traps being adapted to be regenerated at least partly by hydrogen taken from the recirculation circuit of the exhaust gas. Engine according to any one of the preceding claims, characterized in that it comprises a control unit adapted to control a gas flow control valve in the recirculation circuit. Engine according to claim 16, characterized in that the control unit is adapted to regulate a fuel injection and a water injection into the reformer of the recirculation circuit. Engine according to Claim 16 or 17, characterized in that the control unit is adapted to regulate an injection of air into the reformer of the recirculation circuit. Motor vehicle comprising a motor according to one of the preceding claims.

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