MOTOR VEHICLE WITH A HEAT ENGINE COMPRISING A HYDROCARBON TRAP ALLOWING EVAPORATION OF THE CONDENSABLE PHASE OF THE HYDROCARBONS AND ASSOCIATED METHOD

Abstract

The invention relates to a motor vehicle with a gasoline thermal engine comprising a chassis and an exhaust line, said thermal engine emitting exhaust gases comprising hydrocarbons and nitrogen oxides, said exhaust line comprising a first catalyst and a particulate filter, characterized in that said exhaust line comprises a hydrocarbon trap configured to capture by adsorption the hydrocarbons having a condensable phase, said hydrocarbon trap being arranged under said chassis. Furthermore, the invention relates to a method for removing the condensable phase from the hydrocarbons emitted by said vehicle. Figure 1

Description

Title of the invention: MOTOR VEHICLE WITH A HEAT ENGINE COMPRISING A HYDROCARBON TRAP ALLOWING EVAPORATION OF THE CONDENSABLE PHASE OF THE HYDROCARBONS AND METHOD PARTNER

[0001] The invention relates to motor vehicles with a thermal engine running on gasoline, and more particularly to the treatment of polluting emissions from these vehicles.

[0002] Known from the prior art is a patent application US 10781735 which describes a system for reducing exhaust gas emissions for a heat engine running on gasoline. The system comprises an exhaust gas treatment apparatus comprising a nitrogen oxide trap and a hydrocarbon trap. The engine has a lean exhaust state during which emissions are reduced and a rich exhaust state during which emissions are significant. In addition, the system comprises a control unit configured to extend the lean exhaust state during a period of desorption of the hydrocarbons trapped in said hydrocarbon trap so that the reduction of hydrocarbon emissions during said desorption period is favored. Desorption is the transition from a state adsorbed by the surface of a solid to a gaseous state. However, a drawback remains.When said vehicle is started, the hydrocarbons have a condensable phase. The condensable phase cannot be eliminated by a conventional pollution control system. The invention described in the patent application does not allow the desorption of the condensable phase, but only the management of the desorption of the hydrocarbons before their elimination.

[0003] The objective of the present invention is to remedy these drawbacks by proposing a means allowing the desorption of the condensable phase of hydrocarbons.

[0004] To achieve this objective, the invention proposes a motor vehicle with a gasoline thermal engine comprising a chassis and an exhaust line, said thermal engine being capable of emitting exhaust gases comprising hydrocarbons and nitrogen oxides, said exhaust line comprising a first catalyst and a particulate filter, remarkable in that said exhaust line comprises a hydrocarbon trap configured to capture by adsorption the hydrocarbons having a condensable phase, said hydrocarbon trap being arranged under said chassis.

[0005] Thanks to the invention, the efficiency of the treatment of the condensable phase of hydrocarbons is improved without having to integrate a new catalyst into the vehicle. The vehicle thus releases fewer harmful particles into the environment.

[0006] Preferably, said first catalyst is a three-way catalyst.

[0007] The three-way catalyst allows the treatment of carbon monoxide, nitrogen oxides and unburned hydrocarbons.

[0008] Advantageously, said vehicle comprises a second catalyst arranged under said chassis, said second catalyst being arranged upstream or downstream of said hydrocarbon trap.

[0009] The presence of the second catalyst improves the exhaust gas treatment capabilities.

[0010] Preferably, said hydrocarbon trap comprises an impregnation solution having at least one rare natural metallic chemical element.

[0011] Advantageously, said at least one rare natural metallic chemical element is an element making it possible to reduce hydrocarbon emissions, preferably platinum or palladium.

[0012] Platinum and palladium are able to treat hydrocarbons with better efficiency.

[0013] Preferably, said at least one rare natural metallic chemical element is an element making it possible to reduce nitrogen oxide emissions, preferably rhodium.

[0014] The addition of rhodium to the impregnation solution allows the treatment of nitrogen oxides.

[0015] Advantageously, said hydrocarbon trap comprises at least one zeolite.

[0016] Zeolite allows the storage of hydrocarbons in the hydrocarbon trap. MFI type zeolites have the advantages of being thermally stable and hydrophobic. Thus, they are particularly absorbent.

[0017] Furthermore, the invention relates to a method for eliminating the condensable phase of hydrocarbons emitted by said motor vehicle with a thermal engine previously described, remarkable in that said method comprises the following steps: - a step of storing hydrocarbons in said hydrocarbon trap; - a step of heating the hydrocarbons causing desorption of the condensable phase of the hydrocarbons which is converted into carbon dioxide and water vapor.

[0018] The method also makes it possible to limit the formation of secondary particles, otherwise known as secondary organic aerosols, thanks to the elimination of the condensable phase of hydrocarbons, which are precursors of these secondary organic aerosols.

[0019] Preferably, during said heating step, the hydrocarbons are heated to a temperature between 170°C and 200°C.

[0020] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.l] schematically illustrates, in the form of a flowchart, a method for eliminating the condensable phase of hydrocarbons emitted by a motor vehicle with a gasoline thermal engine according to one embodiment of the invention; - [Fig.2] illustrates graphs showing the results of re-cycle tests producing the vehicle driving conditions outdoors to demonstrate the effectiveness of the invention in reducing secondary particle emissions.

[0021] [Fig.l] schematically illustrates, in the form of a flowchart, a method for eliminating the condensable phase of hydrocarbons emitted by a motor vehicle with a gasoline thermal engine according to one embodiment of the invention. The thermal engine emits exhaust gases comprising carbon monoxide, unburned hydrocarbons and nitrogen oxides due to the combustion of gasoline by said thermal engine. Hydrocarbons are organic molecules composed of hydrogen and carbon atoms. Hydrocarbons are found naturally in fossil fuels and are used as a source of energy, i.e. as fuel. The vehicle comprises a chassis and an exhaust line. The exhaust line is a set of elements whose role is to conduct the exhaust gases emitted by the engine during the combustion of the fuel, in this case gasoline, to the outside of said vehicle.The exhaust system includes a first catalyst and a particulate filter. A catalyst is a component in which the gases emitted during the combustion of gasoline are converted into other gases whose harmfulness is reduced. Preferably, the first catalyst is a three-way catalyst. The three-way catalyst acts in three phases to reduce harmful emissions. The catalyst converts both carbon monoxide and hydrocarbons into carbon dioxide and water vapor. In addition, the catalyst causes the conversion of nitrogen oxides into nitrogen. This process effectively reduces the emissions of harmful exhaust gases contributing to air pollution. The particulate filter is a device designed to reduce the emissions of harmful particles from the combustion engine.The role of the particulate filter is to permanently capture the primary soot particles from the thermal engine before eliminating them during a phase called regeneration where a temperature above 550°C allows the combustion of the stored soot particles. In addition, the exhaust line includes a hydrocarbon trap located under the chassis of the said . vehicle. The role of said hydrocarbon trap is to capture hydrocarbons by adsorption, including hydrocarbons with a condensable phase. Preferably, the hydrocarbon trap comprises an impregnation solution that promotes the elimination of harmful components. The impregnation solution comprises at least one rare natural metallic chemical element. In other words, said rare natural metallic chemical element is a precious metal. Advantageously, the rare natural metallic chemical element is chosen from platinum or palladium. Platinum and palladium are very effective in reducing hydrocarbon emissions by oxidation. In addition, platinum and palladium are very resistant to thermal aging. This is why it is advantageous to impregnate said hydrocarbon trap with such rare natural metallic chemical elements. Preferably, the impregnation solution comprises rhodium.Rhodium is particularly effective in reducing nitrogen oxide emissions from the combustion of air by the heat engine. The nitrogen oxides are reduced to nitrogen and oxygen. In another embodiment, the impregnation solution comprises platinum or palladium, and rhodium. Thus, the hydrocarbons and nitrogen oxides are treated simultaneously. Advantageously, said vehicle comprises a second catalyst, preferably a three-way catalyst. The second catalyst is arranged upstream or downstream of said hydrocarbon trap. When the second three-way catalyst is placed downstream of the hydrocarbon trap, it is not necessary for said hydrocarbon trap to contain said rare natural metallic chemical element because the hydrocarbons are converted in the three-way catalyst.Preferably, the hydrocarbon trap comprises at least one zeolite, preferably an MFI type zeolite (acronym meaning Mobil type Five). Zeolite is a natural hydrated silicate comprising aluminum and calcium. The MFI type zeolite has the property of being particularly thermally stable. Indeed, the MFI type zeolite can withstand a temperature of up to 1300 K, or 1026.85°C. In addition, the MFI type zeolite is hydrophobic, it is therefore particularly absorbent: it has cavities in which the water molecules are stored. In the context of the invention, the MFI type zeolite absorbs the condensable part of the hydrocarbons in order to subsequently desorb it. During a storage step E1, the hydrocarbons are trapped in said hydrocarbon trap. Storage is carried out at cold, without first heating the hydrocarbons.Thus, the invention is effective from the start of said vehicle. During a heating step E2, the hydrocarbons undergo an increase in temperature which will cause their desorption and conversion into carbon dioxide and water vapor. Preferably, the hydrocarbons are heated to a temperature between 170°C and 200°C. This is the ideal temperature to allow a . efficient desorption of the condensable phase of hydrocarbons.

[0022] Incomplete combustion of fuels generates volatile organic compounds in the exhaust gases which undergo chemical oxidation reactions inducing, by nucleation, the formation of secondary particles, also called secondary organic aerosols. The volatile organic compounds are condensed and aggregate, thus forming solid particles suspended in the air. Secondary particles can be counted in number, in which case they are referred to as particles by number. In addition, secondary particles can also be counted by mass, in which case they are referred to as particles by mass. Secondary particles have a size of less than 20 nm. For the finest secondary particles, for example when the particles have a size of 10 nm, they represent a significant value in number, but not in mass.Controlling secondary particle emissions is essential because they have a harmful effect on human health and the environment. The objective of the present invention is to limit the formation of secondary particles by eliminating the condensable phase of hydrocarbons. Cycle tests reproducing outdoor vehicle driving conditions have demonstrated the effectiveness of the invention in reducing secondary particle emissions in number. In [Fig.2], a graph A and a graph B are shown. Graph A and graph B present the number of particles emitted in absolute value as a function of vehicle speed, in km / h, over time in seconds. The particles studied have a size greater than 10 nm. The tests were carried out at a temperature of -10°C. The broken line curve corresponds to the vehicle speed.The solid line curve corresponds to the cumulative number of emitted particles. In graph A and graph B, the exhaust line includes the three-way catalyst associated with the non-impregnated particulate filter. In graph B, the exhaust line also includes the hydrocarbon trap. In graph A, a peak in primary and secondary particle emissions is noticeable at 50 s, when the vehicle goes from a speed of 5 km / h to 55 km / h. The emissions peak is characterized by an increase in the cumulative quantity of particles in number from 60.1011 particles to 180.1011 particles. Following this emissions peak, the cumulative particle number is approximately constant throughout the duration of the test at a value of 180.1011 particles despite variations in vehicle speed. In graph B, an emissions peak is also observed at 50 s, when the vehicle goes from a speed of 5 km / h to 55 km / h.The peak emissions in graph B are characterized by an increase in the cumulative particle count from 60.1011 particles to 80.1011 particles. The cumulative particle count is then substantially constant at 80.1011 particles until the end of the test despite variations in vehicle speed. The cumulative particle count in the presence of the trap. hydrocarbons, either on graph B, is therefore reduced by 100.1011 particles compared to the cumulative quantity of particles emitted in the absence of the hydrocarbon trap, or on graph A. The test results therefore demonstrate the effectiveness of the hydrocarbon trap in limiting secondary particle emissions, and therefore consequently in avoiding deterioration of air quality. During the tests, 1400.10 11 particles were emitted over a distance of 8 km when the hydrocarbon trap was not present, compared to 80.1011 particles for the vehicle which had the exhaust line including the hydrocarbon trap. In other words, the hydrocarbon trap made it possible to divide the number of particles emitted by a factor of 17.

Claims

Claims

1. Motor vehicle with a gasoline thermal engine comprising a chassis and an exhaust line, said thermal engine being capable of emitting exhaust gases comprising hydrocarbons and nitrogen oxides, said exhaust line comprising a first catalyst and a particulate filter, characterized in that said exhaust line comprises a hydrocarbon trap configured to capture by adsorption the hydrocarbons having a condensable phase, said hydrocarbon trap being arranged under said chassis.

2. Vehicle according to claim 1 characterized in that said first catalyst is a three-way catalyst.

3. Vehicle according to claim 1 or 2 characterized in that said vehicle comprises a second catalyst arranged under said chassis, said second catalyst being arranged upstream or downstream of said hydrocarbon trap.

4. Vehicle according to any one of claims 1 to 3, characterized in that said hydrocarbon trap comprises an impregnation solution having at least one rare natural metallic chemical element.

5. Vehicle according to claim 4 characterized in that said at least one rare natural metallic chemical element is an element making it possible to reduce hydrocarbon emissions, preferably platinum or palladium.

6. Vehicle according to claim 4 or 5 characterized in that said at least one rare natural metallic chemical element is an element making it possible to reduce nitrogen oxide emissions, preferably rhodium.

7. Vehicle according to any one of claims 1 to 6, characterized in that said hydrocarbon trap comprises at least one zeolite.

8. Method for eliminating the condensable phase of hydrocarbons emitted by said motor vehicle with a thermal engine according to any one of claims 1 to 7, characterized in that said method comprises the following steps: - a step of storing (El) the hydrocarbons in said hydrocarbon trap; - a step of heating (E2) the hydrocarbons generating a de- sorption of the condensable phase of hydrocarbons which is converted into carbon dioxide and water vapor.

9. Method according to claim 8 characterized in that, during said heating step (E2), the hydrocarbons are heated to a temperature between 170°C and 200°C.

Images