WO2020094935A1 - Vehicle equipped with a spark ignition engine and a self-regenerating particulate filter, and associated control method - Google Patents

Abstract

Vehicle comprising an internal combustion engine (2) and an exhaust system (4) connected to the internal combustion engine (2), said system (4) being provided with a particulate filter (6); said filter (6) comprising a filter medium and a catalytic phase, the catalytic phase having an oxygen storage capacity. The vehicle is characterised in that said engine (2) is a spark ignition engine that operates at least under stoichiometric conditions; the engine (2) is configured to cut the injection of fuel or to operate with a lean mixture in order to charge said filter (6) with oxygen, the catalytic phase comprising a cerium oxide which is pure or doped with at least one element from the following list: La, Zr, Y, Gd, Pr, Nd and Sm, and/or another element from the following list: Ag and Pd.

Description

 DESCRIPTION

VEHICLE EQUIPPED WITH A CONTROLLED IGNITION ENGINE AND A SELF-GENERATING PARTICLE FILTER AND METHOD OF MONITORING

ASSOCIATED

Technical area

The invention relates to the field of depollution of internal combustion engines, more particularly to a vehicle provided with a spark-ignition engine connected to a particulate filter and to a method for controlling the latter.

Prior art

The published patent document CN103495418 discloses a diesel engine connected to an exhaust line equipped with a particulate filter comprising a catalytic phase allowing self-regeneration of soot at low temperature. However, the diesel engine has the defect of having a high level of pollution due to the NOx-soot compromise.

Statement of the invention

The object of the invention is to overcome at least one of the drawbacks of the above-mentioned state of the art. More particularly, the invention aims to significantly reduce the soot emissions of a vehicle fitted with an internal combustion engine.

The invention relates to a vehicle comprising an internal combustion engine and an exhaust line connected to the internal combustion engine, the line being provided with a particle filter; the filter comprising a filtering medium and a catalytic phase, the catalytic phase having a remarkable oxygen storage capacity in that the engine is of the spark-ignition type operating at least under stoichiometric conditions and the engine is configured to cut the injecting fuel or operating in a lean mixture in order to charge the oxygen filter, the catalytic phase comprising a pure or doped cerine oxide with at least one element from the following list: La, Zr, Y, Gd, Pr, Nd and Sm , and / or another element from the following list: Ag and Pd. According to an advantageous embodiment of the invention, the catalytic phase is at least based on silver doped zirconium cerine oxide.

According to an advantageous embodiment of the invention, the silver-doped zirconium cerine oxide is of the Ceo, ₄₉ Zro.si O2 type.

According to an advantageous embodiment of the invention, the catalytic phase comprises perovskite of the Lai-x- _y Ag _x Sr _y B O3 type, B being one of the elements on the list: Fe, Mn, Cu Ti, Co and Ni, the element Sr can be replaced by one of the elements in the list: Ca, Ba and K, x is between 0 and 0.5, and y is between 0 and 0.5.

According to an advantageous embodiment of the invention, the perovskite is of the Lao.s Ago, 25 Sro, 25 Mn O3 type.

According to an advantageous embodiment of the invention, the catalytic phase is impregnated directly on the surface of walls of incoming channels of the filter, deposited on a filtration membrane of the particle filter and / or constituting the membrane.

The invention also relates to a method of controlling the vehicle according to the invention, and the method triggers a phase of suspension of the injection or of lean operation if each of the following conditions is met: there is at least one release of the foot driver, zero engine torque demand and / or vehicle drive by an engine / generator; the engine speed is greater than a minimum threshold.

According to an advantageous embodiment of the invention, the method comprises an additional condition: the temperature of the filter is lower than a single predefined,

in particular the predefined threshold being between 300 and 500 ° C.

According to an advantageous embodiment of the invention, the phase of suspension or reduction of the fuel injection ends when at least one of the following conditions is met: the release of the foot is no longer established, the torque demand n is no longer zero and / or the duration of the release of the foot, the demand for zero torque or the drive by a motor / generator exceeds a predetermined threshold.

Preferably, the filtering medium is based on cordierite, aluminum titanate or silicon carbide. Preferably, the internal combustion engine is combined with an engine / generator forming a hybrid powertrain.

The measures of the invention are advantageous in that the self-regeneration process of the particulate filter starts at low temperature, around 300 C instead of 600 ° C for known solutions. In addition, the materials used in the catalytic phase of the particulate filter to ensure the oxidation of the soot are much more economical than those of previous solutions, such as the metals of the platinum group, namely platinum, palladium or rhodium. .

Brief description of the drawings

Other characteristics and advantages of the present invention will be better understood with the aid of the description and the drawing:

[Fig. 1] illustrates an engine connected to an exhaust line.

detailed description

In FIG. 1, an engine 2 of the spark-ignition type operating at least under stoichiometric conditions is connected to an exhaust line 4. The engine 2 and the line 4 are integrated into a vehicle which is not shown. The exhaust gases from engine 2 are successively purified by passing through a first three-way catalyst mounted upstream of a particulate filter 6. Downstream of the exhaust line 4 is a second catalyst, for example.

The particle filter 6 comprises a filter medium and a catalytic phase. The filter medium can be based on cordierite, aluminum titanate or silicon carbide. The catalytic phase can be impregnated directly on the surface of walls of incoming channels of the particle filter 6, deposited on a filtration membrane of the particle filter 6 and / or constituting the membrane.

The oxygen storage and catalytic oxidation properties are well known to those skilled in the art for pure cerine oxide, doped cerine oxide La, Zr, Y, Gd, Pr, Nd, Sm, en presence or absence of precious metals of type Ag, Pd, and their combination as well as perovskites of type La-i - * - _y Agx Sr _y B O3 with x = 0 - 0.5 and y = 0 - 0.5. Sr can be replaced by Ca, Ba, K (alkali and alkaline earth), B being included in the list: Fe, Mn, Cu, Ti, Co and Ni. More particularly, tests have been carried out on two kinds of oxides.

The first type is silver-doped zirconium cerine oxide (2% by mass), named Ag-CZ (Ceo.49Zro.51O2). The silver is deposited on a commercial cerine-zirconia oxide by wet impregnation with Ag nitrate. The catalyst is then dried overnight at study at 100 ° C. and then calcined at 700 ° C. in air for 2 hours.

The second kind of oxide is a perovskite of the Lai-x- _y Ag _x Sr _y B O3 type with x = 0 - 0.5 and y = 0 - 0.5. Sr can be replaced by Ca, Ba, K (alkali and alkaline earth), B is an element from the list Fe, Mn, Cu, Ti, Co, Ni. The perovskite of composition Lao, 5Ago, 25Sro, 25Mn03 (LSAM) can be synthesized in another by the so-called complexation method. The protocol consists in dissolving the metallic nitrates of lanthanum, silver, manganese and strontium in the desired proportions in the minimum of deionized water. A chelating agent, maleic acid 10%, of formula C ₄ H ₄ 0 ₄ is then added to this solution. To promote the complexation of metal precursors with maleic acid, the pH is maintained at 9 by the addition of ammonia. The solution is then evaporated on a hot plate until a gel is obtained and then steamed at 130 ° C for ten hours. The powder thus obtained is calcined at 500 ° C for 2 hours, in order to remove all the carbonaceous residues linked to the synthesis. Calcination at higher temperature (800 ° C) for 4 hours is then necessary to form the perovskite phase and stabilize the microstructure of the powder.

The two kinds of oxide are evaluated on test means reproducing the filling strategy of the material is the supply of air (containing 21% oxygen) via the foot raisers throughout the running of the vehicle.

To reproduce the situation, two mechanical mixtures between, on the one hand, the Ag-CZ powder and the soot, and on the other hand, the LSAM powder and the soot, were produced. The soot used is Printex® U commercial carbon black. Printex® U soot is used as reference soot in numerous studies on pollution control. The measurements of catalytic activities of the two catalysts synthesized for the oxidation of soot were carried out under the following conditions: the soot and the catalyst are mixed in a 1/60 ratio (by mass) and co-ground in a mortar for 15 minutes to obtain intimate contact between the soot and the catalyst. A mass of 200 mg of this mixture is taken and placed in a conventional U-shaped quartz reactor. The experimental conditions for programmed temperature oxidation are: a flow of 250 ppm of Ü2 and 10% of hBO in the He at 10 l / h and an introduction for example of wells (term "Anglo-Saxon", puffs of air) of 2 seconds every 7 minutes containing 20% of oxygen in the He, wells representative of the foot raisers . The reactor is heated from 100 ° C to 680 ° C at ut® speed of 10 ° C / min with an intermediate plate at 400 ° C and 350 ° C according to the requirements of the experiment. The concentration of products resulting (CO and CO2) from the combustion of soot is measured using a gas phase micro-chromatograph (SRA 3000, SRA INSTRUMENTS®) and a mass spectrometer (QMS aspec: Quadrupole Mass Spectrometer, Aspec Technology Inc). The soot conversion is calculated from the CO and CO2 concentrations and is expressed as a function of the temperature.

Oxidation performance at 400 ° C is provided for the material: - in new condition:

 • calcined at 700 ° C for 2 hours, called "fresh_Ag-CZ" ("fresh" term "Anglo-Saxon"; in the context of the tests, it means new)

• calcined at 800 ° C for 4 hours, called "fresh_LS¾M"

- in the aged state:

 · 4 hours at 980 ° C under ISh and 10% water, called "Ag-CZ aged" and

"Old LSAM"

[Table 1]

 [Table 2]

[Table 3]

 [Table 4]

The results on the catalytic performance of soot oxidation show an oxidation of the soot which still exists at 350 ° C. The injection of oxygen via the introduction of air at 400 ° C or even 350 ° C, makes it possible to charge the catalyst with oxide ions resulting from the dissociation of oxygen and at the same time to initiate the phase d oxidation of soot from highly reactive oxide ions. In the driving phase, the engine 2 is configured to produce air wells by cutting the fuel injection on at least one of the engine cylinders 2. The engine control can be configured to recharge the particle filter 6 by triggering a injection suspension phase or lean operation if each of the following conditions is met: there is at least one release of the driver's foot, a zero torque request from engine 2 and / or a vehicle drive by an engine / generator ; the speed of rotation of the motor 2 is greater than a minimum threshold; the temperature of the filter 6 is less than a single predefined, the predefined threshold being between 300 and 500 ° C, for example 400Ό, 375 ° C, 350 ° C, or 300 ° C.

The fuel injection suspension or reduction phase ends when at least one of the following conditions is met: the release of the foot is no longer established, the torque demand is no longer zero and / or the duration of the letting go of the zero torque demand or the drive by a motor / generator exceeds a predetermined threshold.

Claims

1. Vehicle comprising an internal combustion engine (2) and a line  exhaust (4) connected to the internal combustion engine (2), said line (4) being provided with a particle filter (6);  said filter (6) comprising a filtering medium and a catalytic phase, the catalytic phase having an oxygen storage capacity  characterized in that  said engine (2) is of the spark-ignition type operating at least under stoichiometric conditions;  said engine (2) is configured to cut the fuel injection or operate in a lean mixture in order to charge said filter (6) with oxygen, said catalytic phase comprising a pure or doped cerine oxide with at least one element from the following list : La, Zr, Y, Gd, Pr, Nd and Sm, and / or another element from the following list: Ag and Pd. 2. Vehicle according to claim 1, characterized in that said catalytic phase is at least based on zirconium cerine oxide doped with silver. 3. Vehicle according to claim 2, characterized in that the silver doped zirconium cerine oxide is of the Ceo.49 Zro.51 O2 type. 4. Vehicle according to one of claims 1 to 3, characterized in that said catalytic phase comprises perovskite of the Lai-x- _y Ag _x Sr _y B O3 type, B being one of the elements in the list: Fe, Mn , Cu Ti, Co and Ni, the element Sr can be replaced by one of the elements in the list: Ca, Ba and K, x is between 0 and 0.5, and y is between 0 and 0.5. 5. Vehicle according to claim 4, characterized in that said perovskite is of the Lao.s Ago type, 25 Sro, 25 Mn O3 6. Vehicle according to one of claims 1 to 5, characterized in that said catalytic phase is impregnated directly on the surface of walls of incoming channels of said filter (6), deposited on a filtration membrane of the particle filter (6) and / or constituting the membrane. 7. Method for controlling a vehicle comprising an internal combustion engine (2) and an exhaust line (4) connected to the internal combustion engine (2), said line (4) being provided with a particle filter (6), characterized in that said vehicle is according to one of claims 1 to 6 and said method triggers a phase of suspension of the injection or  lean operation if each of the following conditions is met:  (a) there is at least one release of the driver's foot, a torque request from said motor (2) zero and / or a drive of said vehicle by a  engine / generator;  (b) the speed of rotation of the motor (2) is greater than a minimum threshold. 8. Method for controlling a vehicle according to claim 7, characterized in that the method comprises an additional condition:  (c) the temperature of said filter (6) is less than a single predefined, in particular the predefined threshold being between 300 and 500 ° C. 9. A method of controlling a vehicle according to claim 7 or 8, characterized in that said phase of suspension or reduction of fuel injection ends when at least one of the following conditions is met: said release is no longer established, said torque demand is no longer zero and / or the duration of said release from the foot, of said demand in zero torque or of the drive by a motor / generator exceeds a predetermined threshold.