EP2686410A1

EP2686410A1 - Process for operating an engine supplied with a fuel containing a catalyst for regenerating a particulate filter

Info

Publication number: EP2686410A1
Application number: EP12708549.6A
Authority: EP
Inventors: Virginie Harle; Michael Lallemand; Thierry Seguelong
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2011-03-17
Filing date: 2012-03-15
Publication date: 2014-01-22
Also published as: US20140048029A1; FR2972766B1; KR20130133867A; FR2972766A1; JP2016200149A; CN103502402B; JP2014511960A; WO2012123540A1; BR112013023746A2; KR101605597B1; CN103502402A

Abstract

The invention relates to a process for operating an internal combustion engine of a vehicle equipped with an exhaust system comprising a catalysed particulate filter in which the engine is supplied with a fuel containing a catalyst for regenerating the particulate filter. The process is characterized in that the concentration of catalyst in the fuel varies discontinuously.

Description

METHOD FOR OPERATING A FUEL-FEED ENGINE CONTAINING A REGENERATION CATALYST OF A

PARTICLE FILTER

The present invention relates to a method of operating an internal combustion engine, in particular diesel, fueled by a fuel containing a regeneration catalyst of a particulate filter. This process applies to motor vehicles equipped with a catalyzed particulate filter to suppress black fumes from the engine exhaust.

To meet the new emission control standards for vehicles, especially diesel, they are gradually equipped with particulate filters (DPF). This is already the case in Europe since the advent of the Euro 5 standard. In most cases, a catalyst is used to help periodically burn the soot retained on the filter and thus regenerate the FAP.

The regeneration of the FAP is done by periodically increasing the temperature upstream of the FAP, at a temperature sufficient to cause the combustion of soot and thus regenerate the FAP.

This temperature is typically higher than 650 ° C and fuel is therefore usually burned in the engine (post injection) or on an oxidation catalyst upstream of the FAP to achieve this thermal level. In fact, the temperature of the diesel engine exhaust gases is generally much lower, typically below 400 ° C. The temperature of the exhaust gas tends to fall further with new combustion technologies such as HCCI type homogeneous combustion. It is also very low, often less than 250 ° C when the vehicle is used in certain conditions as in urban use.

A second important parameter is the duration of the regeneration of the FAP, that is to say the time during which the temperature upstream of the FAP must be maintained at a high level. In addition to the economic and environmental aspects of higher fuel consumption, in some cases, such as for often short-duration urban journeys, it is not possible to maintain these conditions long enough to regenerate the DPF.

We understand that it is interesting to be able to reduce the periodicity and duration of these regenerations and also to be able to make them at a lower temperature. This in fact leads to a reduction in the vehicle's consumption as a result of the lower amount of fuel consumed for the post-injection. As a result, greenhouse gas (CO2) emissions are reduced by the vehicle.

This also makes it possible to use for the FAP materials that do not need to have a thermal resistance as high as for example silicon carbide and therefore less expensive materials. Moreover, reducing the duration of post-injection is also beneficial on other criteria such as the longevity of the engine and certain components such as high-pressure fuel injectors or the spacing of the engine oil change intervals.

To achieve these objectives, a catalyst that promotes this regeneration is generally used according to two main principles:

the introduction of an oxidation catalyst into the porosity of the walls of the FAP: the FAP is then called catalyzed or called Catalyst Soot Filter (CSF). The catalyst is generally composed of a noble metal, such as platinum and transition metal oxides such as alumina or reducible oxides such as oxides based on cerium, cerium and zirconium or more generally rare earths. This technology is currently widely implemented on recent vehicles meeting the Euro 5 standard in Europe;

- the use of a FAP regeneration additive, vectorized by the fuel supplying the engine or Fuel Borne Catalyst (FBC). Various BCF additives are known, in particular those based on cerium and / or iron. This technology is currently also installed on diesel vehicles.

The second principle is generally more efficient and can regenerate the FAP in all driving conditions, especially urban, and more economical and more environmentally friendly.

However, the major disadvantage of the FBC technology lies in the complexity of its implementation, in particular to ensure a concentration of additive as constant as possible in the fuel as is currently implemented on vehicles equipped with this technology. Typically, it will be sought to maintain a concentration of additive that does not significantly evolve in the fuel, that is to say typically with concentration differences of less than 20% or even less than 10%.

Systems for introducing catalytic FBC catalytic additives into the fuel for FAP regeneration generally rely on a large tank of 2 to 3 liters minimum volume containing the additive and must be located in areas close to the fuel tank.

Current additive dosing processes also use high precision dosing pumps which must be controlled via an additional dedicated electronic unit. This electronic unit is generally servocontrolled to the central electronic unit of the vehicle or ECU. This metering device must be managed in a fine way in order to ensure a sufficient fuel additive content to allow a good regeneration of the FAP, but not too excessive to avoid premature fouling of the FAP due to the mineral regeneration residues of the FAP. FAP that remain collected within it. Generally, when the fuel level increases in the tank, following the addition of fuel, the ECU communicates to the computer the information and the computer indicates to the pump the quantity of additive to be injected into the tank so as to maintain a constant additive concentration in the fuel and this at any time.

These dosing pumps are extremely precise and their cost is important. The use of such methods also involves enslaving the dosing system and well check its operating status. So we have complex systems and, therefore, expensive.

The object of the invention is to propose a process whose implementation is less complex and therefore less expensive than for known methods.

For this purpose, the method of the invention is a method of operating an internal combustion engine of a vehicle equipped with an exhaust system comprising a catalyzed particle filter (CSF) in which the engine is powered with a fuel containing a regeneration catalyst of the particulate filter and characterized in that the catalyst concentration in the fuel varies in a discontinuous manner.

The process of the invention makes it possible to regenerate CSF efficiently, especially at low temperature, without requiring the complex systems of the prior art to maintain the concentration in the fuel at a constant value.

Other characteristics, details and advantages of the invention will emerge even more completely on reading the following description given with reference to the appended drawing and in which:

- Figure 1 single gives the catalyst concentration of a fuel over time and depending on the filling of the fuel tank.

The essential feature of the process of the invention is that the catalyst concentration in the fuel varies in a discontinuous manner. By this is meant that, contrary to the known methods, this concentration is not constant but it is variable in time and it varies more in a non-continuous manner. So it can take in a very short time or instantly different values. It can be zero and vary in ranges which can for example vary by a factor of 0 to 30, more particularly from 0 to 20. Even more particularly these ranges can range from 0 to 15 and in particular from 0 to 5. This concentration can also stay constant at a certain value for a certain period of time and then go in a very short time or instantly at another value to remain constant for another period of time.

The method of the invention can be implemented according to different variants.

According to a first variant, the process is carried out under conditions such that during the CSF loading period, the concentration of catalyst in the fuel varies one more time in an increasing manner. It thus passes from a value V ₀ which can be zero to a value V _n such that V _n > Vo.

By filter loading period is meant the period during which the exhaust gas circulates inside the CSF and where it is gradually loaded into soot. This is all periods of engine operation outside the filter regeneration period.

According to a second variant of the process of the invention and still during the CSF loading period, the concentration of catalyst in the fuel varies several times more and more. It thus passes from a value V ₀ which can be zero to a value V _n and then to another value V _n + i, these values being such that V _n + i> V _n > Vo.

According to another variant, the method is implemented in such a way that during the loading period of the particulate filter, the catalyst concentration in the fuel varies one or more times in a decreasing manner. It can thus go from a value V ₀ which is not zero to a value V _n and possibly to another value V _n + i, these values being such that V _{n +} i <V _n <Vo.

In the case of the second or third variant, the number of times the variation occurs may not be limited.

Finally, according to yet another alternative, the catalyst concentration in the fuel can be varied several times increasing or decreasing during the CSF loading period, which concentration can be zero over a period of time. The invention can be used with any type of CSF regeneration catalyst. These catalysts are well known. More particularly and by way of example only, this catalyst may be in the form of a colloidal dispersion. The colloids of this colloidal dispersion may be based on a compound of a rare earth and / or a metal selected from groups MA, IVA, VIIA, VIII, IB, MB, IIIB and IVB of the periodic table.

They may be more particularly based on cerium and / or iron compounds.

Colloidal dispersions that include detergent compositions can also be used.

The periodic table of elements to which reference is made is that published in the Supplement to the Bulletin of the Chemical Society of France No. 1 (January 1966).

Examples of colloidal dispersions that may be mentioned are those described in patent applications EP 671205, WO 97/19022, WO 01/10545 and WO 03/053560, the latter two notably describing dispersions based on cerium and iron compounds respectively. these dispersions additionally containing an amphiphilic agent.

It is also possible to mention WO 2010/150040 which describes a colloidal dispersion based on an iron compound, an amphiphilic agent and a detergent composition comprising a quaternary ammonium salt.

The quaternary ammonium salt may be the reaction product:

(i) at least one compound that can include:

(a) the condensation product of a hydrocarbon-substituted acylating agent and a compound having an oxygen or nitrogen atom capable of condensing the acylating agent, the condensation product having at least one tertiary amine function;

(b) a polyalkene-substituted amine having at least one tertiary amine function; and

(c) a Mannich reaction product having at least one tertiary amine function, the Mannich reaction product being derived from a hydrocarbon-substituted phenol, an aldehyde and an amine; and

(ii) a quaternizing agent suitable for converting the tertiary amine function of the compound (i) to quaternary nitrogen.

The quaternizing agent may comprise dialkyl sulfates, benzyl halides, hydrocarbon-substituted carbonates; hydrocarbon-substituted epoxides in combination with an acid or mixtures thereof. Catalyzed PAFs are also well known. They generally comprise a catalyst based on at least one metal selected from platinum or platinum group metals, such as palladium. Combinations of platinum with these metals or these metals between them are of course possible.

The catalyst metal may be incorporated in the filter or deposited thereon in a known manner. It can be for example included in a coating (washcoat) itself disposed on the filter. This coating may be chosen from alumina, titanium oxide, silica, spinels, zeolites, silicates, crystalline aluminum phosphates or their mixtures. Alumina can be particularly used. The washcoat may also contain reducible materials capable of directly or indirectly assisting the combustion of soot. Mention may be made, for example, of materials based on cerium oxide such as ceria, mixed oxides based on cerium and zirconium, optionally doped, or even oxides of manganese.

Since the FAP catalyst is a catalyst for assisting in the combustion of soot, it is therefore present on the filter in a relatively small amount, that is to say generally in an amount of plus 70 g / ft ³ (2.5 g / dm ³ ). This quantity is expressed in mass of metal element, for example in weight of platinum, with respect to the volume of the FAP. This amount may more particularly be at most 60 g / ft ³ (2.1 g / dm ³ ) and even more particularly at most 50 g / ft ³ (1.8 g / dm ³ ).

The concentration of regeneration catalyst mass in the fuel, especially when it is in the form of a colloidal dispersion will advantageously be between 0 and 30 ppm, this content being expressed in metal element such as iron in the case of a colloidal dispersion based on iron. The catalyst content of the soot emitted by the engine, expressed as a mass of metal element, may be between 0 and 8%, depending on the content of regeneration catalyst of the fuel, the fuel consumption of the vehicle and its production of soot.

During the implementation of the method of the invention, the vehicle will operate with a fuel containing a variable content of regeneration catalyst, this content may be zero over certain periods. The soot produced by the engine will be more or less rich in active elements for the regeneration of CSF depending on the rate of additive fuel.

Thus the soot loading of the CSF will be done alternately by soot that is not additive or additive in a variable concentration of catalyst. regeneration. The fuel used during the periodic regeneration of the CSF may be additive or non-additive.

Regeneration is then classically controlled by the ECU of the vehicle according to the technology chosen by the manufacturer.

The advantage of the invention is that the additive can be introduced into the fuel by simple systems, less expensive than those known and whose dosing strategy is simpler and faster to implement on the vehicle. Particularly preferred are systems that do not require interfacing with the ECU electronic central system of the vehicle so as to simplify its implementation on the vehicle.

Simple embodiments allowing the introduction of additive in different quantity and variable in time will be given below.

A first embodiment is to manually add a dose of additive, usually liquid, which is poured into the fuel tank of the vehicle. The additive dose is calculated so that the content of active ingredient for the regeneration of the CSF is sufficient to promote the combustion of the soot entrapped in the CSF. By way of example, for an additive based on a colloidal suspension of iron particles such as dispersion C of Example 3 of the patent application WO 2010/150040, the iron element content of the fuel just after manual additivation may advantageously be between 2 and 30 ppm by weight of iron metal, more particularly between 5 and 20 ppm by weight of iron metal.

This simple way makes it possible to add the fuel when it is necessary: in particular at regular frequency when the vehicle is used mainly in town - for example by adding it every 1000 to 3000 km. This means can also be used when the indicator light of the dashboard of the vehicle signals a defect of the means of depollution.

FIG. 1 illustrates an example of a regeneration catalyst concentration profile in the fuel that can be obtained when a dose of additive is added regularly to the tank here every 2200 km (or 44 hours of taxiing). ). In this example a fixed fuel consumption of 6 1/100 km was considered, a fixed speed of 50 km / h or a fixed fuel consumption of 3 l / h. Typically as soon as a dose of additive is added (event 1, denoted Ev1 in the figure: a volume of regeneration catalyst making it possible to reach a metal iron content of 15 ppm in the 40 liters of fuel present in the tank ), the iron content increases sharply from 0 to 15 ppm. This iron content is constant over time until fuel is added to the reservoir which leads to a dilution of the iron concentration in the respective proportions of the residual additive fuel volume and the fuel volume (thus not additive) added (event 2, denoted Ev2: 40 L of fuel (not additive) added to the 20 L of residual fuel in the tank). This event is repeated 4 times in this example. With each addition, the iron concentration decreases proportionally.

The figure also mentions the regeneration periods of the CSF (stars in the figure) - the regenerations being done at regular intervals of 700 km or every 14 hours of operation. It can be noted, for example, that the soot loading of the CSF corresponding to the first regeneration was done with a vehicle operating 50% of the time with a non-additive fuel and 50% of the time with an additive fuel at 15 ppm iron weight. Example 1 below illustrates the benefit obtained by means of a regeneration engine test of a CSF carried out under these loading conditions.

It can be seen that the soot loading of the CSF is done with a fuel whose concentration of additive is variable and that the benefit is obtained by implementing a very simple system of pouring every 2200 km here (44 hours here) a additive dose manually into the tank.

Another embodiment can be used by equipping the vehicle with means for introducing the simple and autonomous regeneration catalyst, that is to say without connection with the central ECU of the vehicle. This means may consist in the introduction of a small FBC catalyst tank, typically 1 L or less, of a metering pump for injecting at regular intervals a given amount of additive into the fuel tank. Compared to the existing system, the pump can be less complicated and therefore less expensive since the quantity injected will be fixed. No interfacing with the ECU is necessary since the pump can be programmed to inject for example at regular intervals (time interval as every 5 to 10 hours and / or kilometer interval as every 1000 to 3000 km). Local devices on the pump such as a power-up or GPS chip may indicate to the pump that the vehicle is driving or giving the distance covered by the vehicle.

Examples will now be given.

EXAMPLE 1

A diesel engine supplied by the Volkswagen Group (4 cylinders, 2 liters, turbocharger with air cooling, 81 kW) was used on a bench engine test. The downstream exhaust line is a commercial line consisting of an oxidation catalyst containing a platinum-alumina washcoat followed by a commercial CSF containing a platinum-alumina washcoat (volume total of filter 3 L).

The fuel used is a commercial fuel meeting the standard

EN590 DIN 51628 containing less than 10 ppm sulfur and containing 7% by volume of EMAG or Fatty Acid Methyl Ester. In the case where an FBC regeneration catalyst is used, the fuel is additive by the amount of FBC additive making it possible to achieve different iron metal content expressed as ppm mass relative to the mass of the fuel. The FBC additive used is an additive based on a colloidal dispersion of iron particles such as dispersion C of Example 3 of the patent application WO 2010/150040, the iron element content of this additive being 4. , 3% mass of iron metal.

The iron content of the additive fuel is controlled by the

X-ray fluorescence directly on the organic liquid.

The test is carried out in two successive steps: a CSF soot loading step, followed by a regeneration step thereof. The conditions of these two stages are strictly identical for the different tests, apart from the fuel used (additive or not).

The loading phase is carried out by operating the engine at a speed of 3000 rpm and using a torque of 45 Nm for approximately 6 hours. This loading phase is stopped when 12 g of particles (or soot) are loaded into the CSF. During this phase the temperature of the gases upstream of the CSF is 230-235 ° C. Under these conditions the particle emissions are about 2 g / h.

After this loading phase, the CSF is disassembled and weighed to control the mass of charged particles during this phase.

The CSF is then reassembled on the bench and warmed by the engine which is reset for 30 minutes in the operating conditions of the load (3000 rpm / 45 Nm). The engine conditions are then modified (torque 80 Nm / 2200 rpm) and a post-injection is controlled by the central electronic engine unit (ECU), which allows the temperature upstream of the CSF to be raised to 500 ° C and to start its regeneration. These conditions are maintained for 60 minutes, this time being counted from the start of the post-injection.

In all cases, the fuel used during the regeneration is the last fuel used for the CSF loading phase. The regeneration efficiency of CSF is measured by two parameters:

the mass of soot burned during the regeneration, calculated from the CSF weighings before loading (Mo), after loading (Me) and at the end of regeneration (Mr). The% of soot burned after 60 minutes of regeneration is expressed as follows:

% total burnt soot = (Mc-Mr) / (Mc-Mo) ^* 100

the mass of soot burned at each instant t of the regeneration calculated from the evolution of the pressure drop of the CSF at each time DPt whereas the pressure drop at the beginning of regeneration (DPc) corresponds to that of the loaded CSF by the soot mass (Mc-Mo) and the pressure drop after 60 minutes (DPr) corresponds to that of the CSF loaded by the non-burned soot (Mr-Mo).

% burned soot (t) = ((DPc-DPt) / (Dpc-Dpr)) ^* % total burnt soot In general, the higher these parameters, the better the regeneration.

Different tests were performed using different fuels during the loading of CSF.

Three reference tests (not in accordance with the invention) were carried out either with a non-additive fuel (test 1) or using an additive fuel throughout the loading of the CSF and its regeneration (test 10 with a rate of additive fuel at 15 ppm iron and test 1 1 with a fuel additivation rate at 3 ppm iron).

8 tests (in accordance with the invention) were carried out using a non-additive fuel at the start of charging the CSF (Fuel No. 1) and an additive fuel (Fuel No. 2) at the end of charging (tests 2 to 5 and 8 to 9) or in the reverse order ie fuel additive at the beginning of loading and not additive (tests 6 to 7).

Each of the tests represents either a respective loading time without and with added fuel or a change in the amount of FBC additive in the fuel.

Table 1 compares the results obtained during the regeneration of the CSF by expressing the% of soot burned in total, ie at the end of the regeneration period (1 hour) or at the beginning of the regeneration (20 minutes).

At each time a comparison is made with the theoretical efficiency obtained by calculating the average between the efficiency of the CSF with a non-additive fuel (test 1) and that of the CSF loaded with an additive fuel (test Table 1: Results of CSF regeneration engine tests

using different fuels

^* comparative tests not in accordance with the invention

* ^* E = experimental Th = theoretical

^*** % expressed in relation to the total filter loading time

First of all, it can be seen that the addition of a BCF to the fuel during the entire CSF loading period (tests 10 and 1 1) greatly increases the efficiency of the regeneration since it is practically complete (88 to 90% burned soot) after 20 minutes at 500 ° C, the iron concentration (3 to 15 ppm) has little impact on regeneration.

In contrast, when a non-additive fuel is used (test 1), the regeneration is not total (60% after 1 hour) and it is also much slower (39% regeneration after 20 minutes). minutes).

The loading of the CSF using an alternation of non-additive fuel then additive (or reverse) can greatly increase the regenerative efficiency of the CSF.

Loading 50% of the time with a 15 ppm iron additive fuel (test 2 or 6) achieves almost total regeneration (85 to 87%) at the end of the test and greatly advanced after 20 minutes. regeneration (72 to 80%).

It is unexpectedly observed that the experimentally observed values are significantly higher than the theoretical values considering the input of the introduced BCF and the non-additive fuel.

The test 2 represents the loading conditions of the CSF described for the loading of the CSF during its first regeneration in FIG.

These conclusions are valid regardless of the proportion of loading times of the CSF with an additive fuel (15% to 50%) and whatever the order of use of the additive fuel (at the beginning or at the end of loading).

It is furthermore observed that the synergistic beneficial effect can be observed with very small amounts of BCF in the fuel as shown in tests 8 and 9. EXAMPLE 2

Another series of CSF regeneration engine test was conducted according to the same protocol and the same equipment as those described in Example 1.

Here the loading of the CSF was conducted by varying more frequently the concentration of BCF (the same as that of Example 1) in the fuel.

The CSF loadings were therefore conducted using the fuel sequence as described in Table 2. Table 2

^* Comparative tests not conforming to the invention Table 3 compares the results obtained during the regeneration

CSF by expressing the total% burned soot, ie at the end of the regeneration period (1 hour) or at the beginning of the regeneration (20 minutes).

Table 3

It is found that the addition of FBC additive to the fuel (tests 10, 12 and 13) makes it possible to increase the efficiency (almost complete regeneration and kinetics of increased regeneration) in comparison with that of the CSF loaded with a non-additive fuel ( test 1). The addition at different doses over time, including the incorporation of periods during which the fuel is not additive (tests 12 and 13) leads to the same result as the use of a fuel whose additive content is perfectly controlled over time (test 10).

Claims

1 - A method of operating an internal combustion engine of a vehicle equipped with an exhaust system comprising a catalyzed particulate filter in which the engine is supplied with a fuel containing a regeneration catalyst of the particulate filter, characterized in that the catalyst concentration in the fuel varies in a discontinuous manner. 2- Method according to claim 1, characterized in that during the loading period of the particulate filter, the catalyst concentration in the fuel varies one time more and more.

3. Process according to claim 1, characterized in that during the loading period of the particulate filter, the concentration of catalyst in the fuel varies several times in an increasing manner.

4- Method according to claim 1, characterized in that during the loading period of the particulate filter, the catalyst concentration in the fuel varies one or more times in a decreasing manner.

5. Method according to claim 1, characterized in that during the loading period of the particulate filter, the catalyst concentration in the fuel varies several times increasing or decreasing.

6. Process according to one of the preceding claims, characterized in that the regeneration catalyst of the particulate filter is in the form of a colloidal dispersion. 7- Method according to claim 6, characterized in that the colloids of the colloidal dispersion are based on a compound of a rare earth and / or a metal selected from groups MA, IVA, VIIA, VIII, IB , MB, IIIB and IVB of the Periodic Table. 8- Process according to claim 7, characterized in that the colloids of the colloidal dispersion are based on a cerium and / or iron compound.

9- Method according to one of claims 6 to 8, characterized in that the Colloidal dispersion comprises a detergent composition.

10- Method according to claim 8 or 9, characterized in that the colloidal dispersion is based on an iron compound, an amphiphilic agent and a detergent composition comprising a quaternary ammonium salt.