Method for reducing emissions from an internal combustion engine comprising injecting an aqueous composition comprising at least one compound capable of releasing formaldehyde

Abstract

The present invention relates to a method for reducing emissions from an internal combustion engine, in particular a spark-ignition engine running on gasoline, hydrogen, natural gas or biogas or a compression-ignition engine, comprising injecting, into the combustion chamber of the engine or upstream thereof, an aqueous composition comprising at least one compound capable of releasing formaldehyde. The present invention further relates to the use of said aqueous composition for reducing pollutant emissions, such as particulate emissions.

Description

Title of the invention: Method for reducing emissions from an internal combustion engine comprising the injection of an aqueous composition comprising at least one compound capable of releasing formaldehyde

[0001] The present invention relates to a method for reducing emissions from an internal combustion engine, in particular a spark-ignition engine, in particular a gasoline, hydrogen, natural gas or biogas engine, or a compression-ignition engine, comprising injecting, into the combustion chamber of the engine or upstream thereof, an aqueous composition comprising at least one compound capable of releasing formaldehyde.

[0002] The present invention further relates to the use of said aqueous composition for reducing polluting emissions, such as in particular particle emissions.

[0003] European and global pollution standards applicable to both light and heavy goods vehicles have imposed increasingly strict constraints on the emission levels of vehicles equipped with internal combustion engines, such as spark-ignition engines, for example gasoline, hydrogen, natural gas or biogas or compression-ignition engines.

[0004] Particle emissions can be cited among the most regulated polluting emissions.

[0005] As is known per se, all internal combustion engines emit particles at more or less high levels, including engines powered by hydrogen. These particles come from the combustion of the fuel and / or the combustion of part of the lubricant composition used to lubricate the engine system.

[0006] Currently, existing solutions for reducing emissions of polluting particles consist of post-treatment of exhaust gases. In addition, few fuel pre-treatment solutions using additives aim to reduce polluting emissions. The use of these additives is rather aimed at improving engine performance.

[0007] Application WO2020159392 proposes adding to the air an aqueous composition comprising transition metal salts in a high oxidation state in order to reduce pollutant emissions. The presence of metal compounds in the combustion chamber is not desirable because it promotes the formation of deposits which can cause hot spots, sources of pre-ignition phenomena. Furthermore, the injection of metallic compounds into the combustion chamber is likely to lead to emissions of metallic substances in the exhaust, the harmfulness of which to living organisms is raised.

[0008] There is a real need to develop a simple solution to effectively reduce pollutant emissions, particularly particles.

[0009] The present invention relates to internal combustion engines, in particular spark-ignition engines running on gasoline, hydrogen, natural gas or biogas and compression-ignition engines.

[0010] The Applicant has discovered that the use of an aqueous composition comprising at least one compound capable of releasing formaldehyde in an internal combustion engine makes it possible to achieve the aforementioned objectives.

[0011] In particular, it has discovered that injecting into the engine at least one compound capable of releasing formaldehyde in solution in water makes it possible to reduce polluting emissions, in particular particle emissions.

[0012] The present invention therefore relates to a method for reducing emissions from an internal combustion engine comprising the injection, into the combustion chamber of the engine or upstream thereof, of an aqueous composition comprising at least one compound capable of releasing formaldehyde.

[0013] The method according to the present invention makes it possible to reduce polluting emissions, in particular particle emissions, in a simple and effective manner.

[0014] Furthermore, the aqueous composition used in the method according to the invention is simple to formulate and to use.

[0015] The present invention further relates to the use of an aqueous composition comprising at least one compound capable of releasing formaldehyde, for reducing pollutant emissions, in particular particle emissions.

[0016] Furthermore, the Applicant has found that the method according to the present invention also makes it possible to prevent and / or reduce pre-ignition phenomena in internal combustion engines, in particular spark-ignition engines. The method according to the present invention thus makes it possible to improve the operation of the engine, to extend its service life and to obtain an increase in engine efficiency.

[0017] This pre-ignition phenomenon is well known in gasoline, gas and biogas spark ignition engines. It is also very present in hydrogen spark ignition engines, as hydrogen burns very quickly and does not require much energy to self-ignite. Reducing this phenomenon has a positive impact on engine efficiency and performance by reducing an increase in temperature and pressure in the combustion chamber at an early point in the engine cycle.

[0018] Other objects, characteristics, aspects and advantages of the invention will become apparent even more clearly when reading the description and examples that follow.

[0019] In the remainder of the text, the term "compounds capable of releasing formaldehyde" or "formaldehyde precursor compounds" will be used more simply to designate compounds, other than formaldehyde, capable of generating formaldehyde. Preferably, this release of formaldehyde is carried out under the temperature and pressure conditions encountered in the combustion chamber of the engine. These compounds are described more specifically in the remainder of the text.

[0020] In what follows, and unless otherwise indicated, the limits of a domain of values are included in this domain, in particular in the expressions “between” and “ranging from ... to ...”.

[0021] Furthermore, the expressions “at least one” and “at least” used in the present description are respectively equivalent to the expressions “one or more” and “greater than or equal”.

[0022] Water The composition used according to the method of the invention is aqueous, that is to say it comprises water. Preferably, demineralized water is used.

[0023] Preferably, the water content is between 60 and 98% by mass, more preferably between 70 and 95% by mass, and better still between 75 and 90% by mass, relative to the total mass of the aqueous composition.

[0024] Compounds capable of releasing formaldehyde The aqueous composition used in the process of the invention comprises at least one compound capable of releasing formaldehyde (CH2O).

[0025] Preferably, the chosen compound(s) are capable of releasing formaldehyde under the temperature and pressure conditions of the combustion chamber or the compression chamber of the internal combustion engine.

[0026] A person skilled in the art is able to choose one or more formaldehyde precursor compounds according to the invention, making it possible to generate formaldehyde under the conditions of the combustion chamber of the engine, in which the aqueous composition is intended to be used.

[0027] More particularly, the temperature in the combustion chamber of an engine may be greater than or equal to 200°C, in particular between 250°C and 800°C and in particular between 300°C and 600°C.

[0028] The pressure within the combustion chamber can vary from 5.104 Pa to 200.105 Pa, in particular from 2.105 Pa to 180.105 Pa.

[0029] The formaldehyde precursor compound(s) according to the invention may thus be more particularly capable of generating / releasing, by thermal decomposition, formaldehyde under conditions of temperature greater than or equal to 200°C and pressure greater than or equal to 5.104 Pa.

[0030] As examples, the compound(s) capable of releasing formaldehyde may in particular be chosen from N-methylol compounds such as dimethylol urea, trimethylol urea, dimethylol guanidine, trimethylol melamine, hexamethylol melamine; 1,3,5,5-tetramethylimidazolidine-2,4-dione; sodium bisulfite formaldehyde; methenamine; polymerized forms of formaldehyde such as paraformaldehyde; trioxanes and trioxane derivatives; and mixtures of these compounds.

[0031] According to a particular embodiment, the compound capable of releasing formaldehyde used according to the invention is chosen from methenamine, paraformaldehyde and trioxanes, in particular 1,3,5-trioxane.

[0032] Preferably, the compound capable of releasing formaldehyde according to the invention is a trioxane, in particular 1,3,5-trioxane.

[0033] The formaldehyde precursor compounds required according to the invention may be commercially available, or prepared according to synthesis methods known to those skilled in the art, in particular from formaldehyde.

[0034] For example, trioxane can be produced by trimerization of formaldehyde using acid catalysts.

[0035] It is understood that, within the framework of the present invention, a formaldehyde precursor may be in the form of a mixture of different formaldehyde precursors, in particular as defined above.

[0036] Preferably, the compound(s) capable of releasing formaldehyde are present in a content ranging from 0.5 to 25% by mass, more preferably from 0.75 to 20% by mass, more preferably still from 1 to 10% by mass, relative to the total mass of the aqueous composition.

[0037] In a particular embodiment, the 1,3,5-trioxane is present in a content preferably ranging from 0.5 to 25% by mass, more preferably from 0.75 to 20% by mass, more preferably still from 1 to 10% by mass, relative to the total mass of the aqueous composition.

[0038] Other additives The aqueous composition used in the process of the invention may optionally also comprise one or more additional additives, different from the compounds capable of releasing formaldehyde described above.

[0039] This or these additional additives may be chosen, for example, in a non-limiting manner, from detergent additives, anti-corrosion additives, biocides, anti-freeze additives, anti-oxidant additives, anti-wear additives, friction modifying additives, and mixtures thereof.

[0040] These additional additives may be present in quantities ranging, for each, from 0.01 to 3% by mass (each), preferably 0.05 to 1% by mass (each), relative to the total mass of the aqueous composition according to the invention.

[0041] According to one embodiment, the aqueous composition used in the method of the invention does not comprise additional additives, other than the compounds capable of releasing formaldehyde. In this embodiment, the aqueous composition is therefore just made up of water and the compound(s) capable of releasing formaldehyde.

[0042] The process The method according to the invention applies to any internal combustion engine.

[0043] In a first embodiment, the internal combustion engine is a spark-ignition engine, preferably selected from a gasoline spark-ignition engine, a hydrogen spark-ignition engine, a natural gas spark-ignition engine and a biogas spark-ignition engine. In this embodiment, the composition as defined above is injected into the engine powered by a fuel composition selected from a gasoline composition, hydrogen, natural gas or biogas.

[0044] In the case of a hydrogen fuel composition, the hydrogen is preferably produced by electrolysis of water from low CO2 impact electricity, by reforming natural gas with capture of the emitted CO2, or by decomposition of natural gas into solid carbon and hydrogen. Hydrogen can also come from fossil sources without capture of CO2 such as natural gas or coal. Hydrogen can also come from biogenic sources produced by biological organisms or by decomposition of organic matter. Finally, hydrogen can also come from natural geological sources and produced in the Earth's subsoil.

[0045] In a second embodiment, the internal combustion engine is a compression ignition engine, or Diesel engine. In this embodiment, the composition as defined above is injected into the engine powered by a fuel composition which may in particular be chosen from diesel fuels (or so-called “Diesel” fuel) and biodiesel fuels (or so-called “bio-Diesel” fuel) and their mixtures.

[0046] In a variant of this embodiment, the compression ignition engine is a mixed fuel engine (also commonly referred to as a “dual fuel” engine). In this variant, the aqueous composition as defined above is injected into the engine powered by a combination of at least two different fuel compositions, in particular of the diesel / gasoline, diesel / LPG, diesel / CNG, diesel / ethanol, diesel / ammonia type. In the case of a marine engine, the engine is powered by a combination of the heavy fuel oil / natural gas, heavy fuel oil / methanol, heavy fuel oil / ammonia type.

[0047] In a third embodiment, the internal combustion engine, in particular the spark-ignition engine, is associated with an electric motor, it is then a so-called hybrid engine.

[0048] According to the method of the invention, the injection of the aqueous composition comprising at least one compound capable of releasing formaldehyde can be carried out either upstream of the combustion chamber of the engine, in particular in the intake circuit of the air and fuel mixture of the internal combustion engine (indirect injection), or directly into the combustion chamber of the engine (direct injection).

[0049] In the case of an indirect injection mode, the aqueous composition is preferably sprayed into the air and fuel intake circuit and mixes with the air present before being admitted into the combustion chamber or the compression chamber of the engine.

[0050] In the case of a direct injection mode, the aqueous composition is sprayed directly into the combustion chamber or the compression chamber of the engine and mixes with the air present in said chamber.

[0051] This injection can be carried out using means known per se such as an injection nozzle which makes it possible to spray the composition upstream of the combustion chamber of the engine, in particular in the air intake circuit, or directly into the combustion chamber.

[0052] The quantity of composition injected is determined by controlling the opening time of the injector, taking into account the volume flow rate of the injector and the density of the injected fluid.

[0053] The present invention further relates to the use of the aqueous composition comprising at least one compound capable of releasing formaldehyde, as defined above, for reducing the polluting emissions of an internal combustion engine.

[0054] In particular, the present invention relates to the use of the aqueous composition comprising at least one compound capable of releasing formaldehyde, as defined above, for reducing particle emissions.

[0055] Particle emission levels can be measured in particular in accordance with the methods defined in European regulation ECE-R83.05. This regulation defines a harmonized test procedure for vehicle approval in Europe and the measurement of different types of emissions. This regulation is defined with reference to a standardized test called WLTP (World Harmonized Light Duty Test Procedure), which is a globally harmonized test procedure. In this procedure, emissions are measured using high-precision emissions analyzers during defined test cycles called WLTC (World Harmonized Light Duty Test Cycle), WHTC (World Harmonized Transient Cycle) or NEDC (New European Driving Cycle) depending on the vehicle type and standard (Euro 6 or Euro VI).

[0056] The use of the aqueous composition comprising at least one compound capable of releasing formaldehyde, as defined above, also makes it possible to prevent and / or reduce pre-ignition in an internal combustion engine, preferably in a spark-ignition engine.

[0057] The following examples are given by way of illustration of the invention, and should not be interpreted in such a way as to limit its scope. Examples Example 1: Particle emission

[0058] Compositions A1 to A3 according to the invention and comparative C1 were prepared from the ingredients whose contents are indicated in the table below (% by mass):

[0059] [Tables 1] Al A2 A3 Cl water 99 95 90 100 1,3,5-trioxane 1 5 10 -

[0060] The test procedure uses a single-cylinder engine with a displacement of 1.3L (stroke: 135 mm, bore: 110 mm), 4 valves, equipped with air supercharging by compressor and provided with a spark plug ignition system. Hydrogen in gaseous form and with a purity greater than 99.995% is used as fuel and injected indirectly into the combustion chamber using a gas injector placed on the air intake circuit of the engine. An aqueous solution injector is also installed on the air circuit of the engine in order to inject each tested composition (Al, A2, A3 and Cl) at a flow rate controlled by a gear pump and a mass flow meter under a pressure of 10 bar. A mass particle counter is installed on the engine exhaust line to characterize the mass quantity of particles emitted by the operation of the engine for the different tested compositions.The operating point chosen in this example targets the following values: 900 rpm, indicated average pressure of 11.5 bar, intake air pressure of 2.5 bar, intake air temperature of 42°C, air / fuel ratio lambda of 2.4. The tests are carried out for a ratio of the mass flow rate of the tested composition to the mass flow rate of hydrogen (H2) of 0.2. The particle emission values for the different compositions tested are grouped in Table 2 below.

[0061] [Tables2] Al A2 A3 Cl Particle concentration (pg / m3) 11.5 14 11 20.4

[0062] Compositions A1, A2 and A3, comprising 1,3,5-trioxane, make it possible to reduce particle emissions, and therefore to improve environmental performance, compared to a comparative composition C1 comprising only water. Example 2: Pre-ignition

[0063] Compositions A4 according to the invention and comparative compositions C2 and C3 were prepared from the ingredients whose contents are indicated in the table below (% by mass):

[0064] [Tables3] A4 C2 C3 water 99 100 67.5 1,3,5-trioxane 1 - - urea - - 32.5

[0065] The impact on pre-ignition was then measured. A single-cylinder engine with a displacement of 0.5L (stroke: 108 mm, bore: 75 mm), 4 valves, equipped with a turbocharger and a spark-ignition system is used. Hydrogen in gaseous form and with a purity greater than 99.995% is used as fuel and injected directly into the combustion chamber using a gas injector. The operating point used is set at 2000 rpm of rotation speed, an engine load of 8 bar (8. 105 Pa) of Effective Mean Pressure (PME) and with a richness of the air / hydrogen fuel mixture of 0.4. A liquid-phase injection system is installed on the intake circuit and connected to an adjustable flow pump and a tank. The compositions described in Table 3 are introduced into this liquid tank with a flow rate of 1 kg / h. The occurrence of pre-ignition in the combustion chamber is identified using a cylinder pressure sensor measuring the pressure during the combustion cycle. The pre-ignition frequency is defined by the number of pre-ignition cycles per 100 engine cycles. For each composition tested, a characterization of the pre-ignition frequency is carried out on an engine configuration without injection of said composition into the engine air intake circuit, then another pre-ignition characterization in the same engine configuration is carried out with an injection flow rate of 1 kg / h of said composition into the engine air intake circuit. The impact on pre-ignition of the tested composition is defined by the difference in pre-ignition frequency between the configuration with injection and without injection reported to the pre-ignition frequency without injection: - a negative value indicates a reduction in the pre-ignition frequency due to the tested composition, - a positive value indicates an increase in the pre-ignition frequency and therefore a deterioration in combustion conditions.

[0066] The results are shown in Table 4 below:

[0067] [Tables4] A4 C2 C3 Impact on pre-ignition -100% -10% > +800%

[0068] Comparative composition C2 (comprising only demineralized water) generates a reduction in the engine pre-ignition frequency of 10%. This composition C3 corresponds to a composition already implemented by those skilled in the art in various industrial applications.

[0069] The comparative composition C3, based on urea, is a well-known composition for SCR pollution control systems and widely used in the transport industry. This composition results in an increase in the pre-ignition frequency of more than 800%, therefore a clear deterioration in combustion conditions.

[0070] Composition A4 according to the invention makes it possible to reduce the pre-ignition frequency by 100%.

Claims

Claims

1. A method of reducing emissions from an internal combustion engine comprising injecting, into the combustion chamber of the engine or upstream thereof, an aqueous composition comprising at least one compound capable of releasing formaldehyde.

2. Method according to claim 1, characterized in that the compound(s) capable of releasing formaldehyde are chosen from N-methylol compounds such as dimethylol urea, trimethylol urea, dimethylol guanidine, trimethylol melamine, hexamethylol melamine; 1,3,5,5-tetramethylimidazolidine-2,4-dione; sodium bisulfite formaldehyde; methenamine; polymerized forms of formaldehyde such as paraformaldehyde; trioxanes and trioxane derivatives; and mixtures of these compounds.

3. Method according to any one of the preceding claims, characterized in that the compound capable of releasing formaldehyde is a trioxane.

4. Method according to any one of the preceding claims, characterized in that the compound capable of releasing formaldehyde is 1,3,5-trioxane.

5. Method according to any one of the preceding claims, characterized in that the compound(s) capable of releasing formaldehyde are present in a content ranging from 0.5 to 25% by mass, preferably from 0.75 to 20% by mass, more preferably from 1 to 10% by mass, relative to the total mass of the aqueous composition.

6. Method according to any one of the preceding claims, characterized in that the composition further comprises one or more additional additives chosen from detergent additives, anti-corrosion additives, biocides, anti-freeze additives, antioxidant additives, anti-wear additives, friction modifying additives, and mixtures thereof.

7. Method according to any one of the preceding claims, characterized in that the injection of the aqueous composition is carried out directly into the combustion chamber of the engine.

8. Method according to any one of claims 1 to 6, characterized in that the injection of the aqueous composition is carried out upstream of the combustion chamber of the engine, in particular in the intake circuit of the air and fuel mixture of the combustion engine. internal.

9. A method according to any one of the preceding claims, characterized in that the internal combustion engine is a spark-ignition engine, preferably chosen from a gasoline spark-ignition engine, a hydrogen spark-ignition engine, a natural gas spark-ignition engine or a biogas spark-ignition engine.

10. A method according to any one of claims 1 to 8, characterized in that the internal combustion engine is a compression ignition engine.

11. Use of an aqueous composition comprising at least one compound capable of releasing formaldehyde, as defined in any one of claims 1 to 6, for reducing the polluting emissions of an internal combustion engine.

12. Use according to claim 11, for reducing particulate emissions.