EP4103823A1

EP4103823A1 - Use of a paraffinic gasoil

Info

Publication number: EP4103823A1
Application number: EP21703484.2A
Authority: EP
Inventors: Huw Lloyd JONES; Alastair Graham SMITH; Richard Hugh Clark; Daniel Michael MASON
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2020-02-12
Filing date: 2021-02-10
Publication date: 2022-12-21
Also published as: CA3170647A1; WO2021160694A1; JP2023513352A

Abstract

Use of a paraffinic gasoil in a diesel fuel composition for reducing the amount of SCR reagent required by an SCR system fitted to a compression ignition internal combustion engine. The present invention has the advantage that the number of SCR reagent vehicle fills per year is reduced, hence minimising the user's exposure to a corrosive liquid.

Description

USE OF A PARAFFINIC GASOIL

Field of the Invention

The present invention relates to the use of a paraffinic gasoil for providing certain benefits in a Selective Catalytic Reduction (SCR) system fitted to a compression ignition engine. In particular, the present invention relates to the use of a paraffinic gasoil for reducing the amount of SCR reagent required in a Selective Catalytic Reduction system fitted to a compression ignition engine.

Background of the Invention

Selective Catalytic Reduction (SCR) is a NOx emission control technique applicable to a wide range of diesel engines from light-, medium- and heavy-duty diesel engines systems right up to two-stroke low-speed marine engines. In essence, within an SCR system, an SCR reagent (for example, urea) is injected into the stream of engine exhaust gases. Once mixed with the exhaust gases the SCR reagent undergoes decomposition to produce ammonia. The mixture of ammonia and exhaust gases enters the SCR catalyst where the ammonia reduces the NOx to nitrogen.

Whilst SCR systems are renowned for their efficient removal of NOx emissions, they do require an "on-board" supply of the SCR reagent. The consumption of this SCR reagent will vary according to the engine operating conditions, but over average driving conditions it is typically in the range of 3% to 8% of the parallel fuel consumption. This can be a cost and/or health and safety burden to a vehicle owner, especially a vehicle fleet operator. AdBlue (RTM) can corrode some metals and needs to be rinsed off immediately if spilt on the skin, and there are recommendations to wear protective gloves during the filling procedure.

It would therefore be desirable to provide a fuel based solution that reduces the amount of SCR reagent required, and is applicable to all SCR systems, irrespective of the equipment that the manufacturer has employed.

It would also be desirable to provide a fuel based solution for reducing the number of SCR reagent vehicle fills per year, thus minimising a user's exposure to a corrosive liquid.

It has now been surprisingly found that by using a paraffinic gasoil in a diesel fuel composition, a surprising and hitherto unrecognised reduction in the amount of SCR reagent required to achieve the necessary reduction of NOx emissions by the SCR system can be obtained.

Summary of the Invention

According to the present invention there is provided the use of a paraffinic gasoil in a diesel fuel composition for reducing the amount of SCR reagent required by an SCR (Selective Catalytic Reduction) System fitted to a compression ignition internal combustion engine.

According to another aspect of the present invention there is provided a method for reducing the amount of SCR reagent required by an SCR (Selective Catalytic Reduction) System fitted to a compression ignition internal combustion engine, which method comprises a step of introducing into said engine a diesel fuel composition which comprises a paraffinic gasoil.

According to another aspect of the present invention there is provided the use of a paraffinic gasoil in a diesel fuel composition for reducing the number of SCR reagent vehicle fills per year.

It has been found that use of a paraffinic gasoil in a diesel fuel composition can lead to a reduced amount of SCR reagent required by the SCR (Selective Catalytic Reduction) System fitted to a compression ignition internal combustion engine.

Brief Description of the Drawings

Figure 1 is a graphical representation of the results shown in Table 3 below.

Detailed Description of the Invention

As used herein there is provided the use of a paraffinic gasoil in a diesel fuel composition for the purpose of reducing the amount of SCR reagent required by an SCR (Selective Catalytic Reduction) System fitted to a compression ignition engine. In the context of this aspect of the invention, the term "reducing the amount of SCR reagent required" embraces any degree of reduction in the amount of SCR reagent required by the SCR system.

The reduction in the amount of SCR reagent required may be of the order of 5% or more, preferably 10% or more, more preferably 20% or more, and especially 40% or more compared to the amount of SCR reagent required by an analogous SCR system when an analogous fuel formulation is used to fuel the compression ignition engine but which does not contain a paraffinic gasoil (for example, wherein the analogous fuel formulation contains or consists of an EN590 refinery diesel base fuel instead of a paraffinic gasoil).

As used herein, the term 'SCR reagent' means a substance or solution of a substance which is stored on board the vehicle and in accordance with the engine- exhaust system demand is introduced (e.g. sprayed) into the exhaust gas stream for reaction with exhaust NOx over an SCR catalyst. The SCR reagent for use herein is any reagent suitable for use in an SCR system which of itself or through its breakdown products is capable of reacting with (i.e. reducing) the NOx within the exhaust gases (NOx) to produce nitrogen. Essentially, the SCR reagent can be ammonia itself or any substance whose breakdown products include ammonia.

Preferably, the SCR reagent is selected from urea, ammonia, ammonium salts such as ammonium formate and ammonium carbamate, and mixtures thereof. The SCR reagent can be present in anhydrous form or as an aqueous solution. In a preferred embodiment, the SCR reagent is urea, preferably an aqueous solution of urea.

A commercially available SCR reagent for use herein is AdBlue (RTM) commercially available from fuel and other suppliers, defined by the specification ISO 22241.

A first essential component of the diesel fuel composition herein is a paraffinic gasoil. The paraffinic gasoil fuel is preferably present in the diesel fuel composition herein at a level in the range from 20% v/v to 100% m/m, preferably from 50% v/v to 100% v/v, more preferably from 80% v/v to 100 %v/v, even more preferably from 90% v/v to 100% v/v, based on the total diesel fuel composition.

In another embodiment herein, the paraffinic gasoil fuel is present in the diesel fuel composition as a blend together with a diesel base fuel, such as an EN590 refinery diesel base fuel. In this embodiment, the paraffinic gasoil oil fuel is preferably present in the diesel fuel composition at a level in the range from 10% v/v to 99% v/v, more preferably from 20% v/v to 70% v/v, even more preferably from 20% v/v to 50% v/v, and especially from 20% v/v to 30% v/v, based on the total diesel fuel composition.

The paraffinic gasoil for use in the present invention can be derived from any suitable source as long as it is suitable for use in a diesel fuel composition.

Suitable paraffinic gasoils include, for example, Fischer-Tropsch derived gasoils, and gasoils derived from hydrogenated vegetable oil (HVO), and mixtures thereof.

From the viewpoint of reducing the amount of SCR reagent required by an SCR (Selective Catalytic Reduction) System, while ensuring other properties such as viscosity, density and distillation properties stay within the requirements of diesel specifications, the paraffinic gasoil used herein is preferably a Fischer-Tropsch derived gasoil fuel. The paraffinic nature of Fischer-Tropsch derived gasoil means that diesel fuel compositions containing it will have high cetane numbers compared to conventional diesel.

While Fischer-Tropsch derived gasoil is the preferred paraffinic gasoil for use herein, the term "paraffinic gasoil" as used herein also includes those paraffinic gasoils derived from the hydrotreating of vegetable oils (HVO). The HVO process is based on an oil refining technology. In the process, hydrogen is used to remove oxygen from the triglyceride vegetable oil molecules and to split the triglyceride into three separate chains thus creating paraffinic hydrocarbons.

In accordance with the present invention, the paraffinic gasoil for use herein, (i.e. the Fischer- Tropsch derived gasoil, the hydrogenated vegetable oil derived gasoil, and the like) will preferably consist of at least 95% w/w, more preferably at least 98% w/w, even more preferably at least 99.5% w/w, and most preferably up to 100% w/w of paraffinic components, preferably iso- and normal paraffins.

By "Fischer-Tropsch derived" is meant that a fuel or base oil is, or derives from, a synthesis product of a Fischer-Tropsch condensation process. The term "non- Fischer-Tropsch derived" may be interpreted accordingly.

A Fischer-Tropsch derived fuel may also be referred to as a GTL (gas-to-liquid) fuel.

The Fischer-Tropsch reaction converts carbon monoxide and hydrogen into longer chain, usually paraffinic, hydrocarbons: n(CO + 2¾ ) = (—CH₂—)_n + h¾0 + heat, in the presence of an appropriate catalyst and typically at elevated temperatures (e.g. 125 to 300°C, preferably 175 to 250°C) and/or pressures (e.g. 5 to 100 bar, preferably 12 to 50 bar). Hydrogen: carbon monoxide ratios other than 2:1 may be employed if desired.

The carbon monoxide and hydrogen may themselves be derived from organic or inorganic, natural or synthetic sources, typically either from natural gas or from organically derived methane.

More recently, techniques to derive carbon monoxide and hydrogen from other sources, including more sustainable ones, are being explored and used. For example, starting with carbon dioxide and water, the water can be electrolysed to give free hydrogen, typically using electricity from a sustainable source. This hydrogen can react with the carbon dioxide in the "reverse water shift reaction" to give a source of carbon monoxide. Alternatively, in place of the "reverse water shift reaction", electrolysis can be used for the electrochemical conversion of carbon dioxide into the required carbon monoxide. This carbon monoxide (from the sources described) can then be reacted with the remaining hydrogen in the typical Fischer Tropsch synthesis process. Because of the use of electrolysis, some of these production processes are referred to as "Power-to- liquids".

Gas oil, kerosene fuel and base oil products may be obtained directly from the Fischer-Tropsch reaction, or indirectly for instance by fractionation of Fischer- Tropsch synthesis products or from hydrotreated Fischer- Tropsch synthesis products. Hydrotreatment can involve hydrocracking to adjust the boiling range (see, e. g. GB2077289 and EP0147873) and/or hydroisomerisation which can improve cold flow properties by increasing the proportion of branched paraffins. EP0583836 describes a two-step hydrotreatment process in which a Fischer- Tropsch synthesis product is firstly subjected to hydroconversion under conditions such that it undergoes substantially no isomerisation or hydrocracking (this hydrogenates the olefinic and oxygen-containing components), and then at least part of the resultant product is hydroconverted under conditions such that hydrocracking and isomerisation occur to yield a substantially paraffinic hydrocarbon fuel or oil.

Desired diesel fuel fraction (s) may subsequently be isolated for instance by distillation.

Other post-synthesis treatments, such as polymerisation, alkylation, distillation, cracking- decarboxylation, isomerisation and hydroreforming, may be employed to modify the properties of Fischer-Tropsch condensation products, as described for instance in US-A- 4125566 and US-A-4478955.

Typical catalysts for the Fischer-Tropsch synthesis of paraffinic hydrocarbons comprise, as the catalytically active component, a metal from Group VIII of the periodic table, in particular ruthenium, iron, cobalt or nickel. Suitable such catalysts are described for instance in EP0583836.

An example of a Fischer-Tropsch based process is the SMDS (Shell Middle Distillate Synthesis) described in "The Shell Middle Distillate Synthesis Process", van der Burgt et al (vide supra). This process (also sometimes referred to as the Shell "Gas-to-Liquids" or "GTL" technology) produces diesel range products by conversion of a natural gas (primarily methane) derived synthesis gas into a heavy long-chain hydrocarbon (paraffin) wax which can then be hydroconverted and fractionated to produce liquid transport fuels such as gasoils and kerosene. Versions of the SMDS process, utilising fixed- bed reactors for the catalytic conversion step, are currently in use in Bintulu, Malaysia, and in Pearl GTL, Ras Laffan, Qatar. Kerosenes and (gas)oils prepared by the SMDS process are commercially available for instance from the Royal Dutch/Shell Group of Companies.

By virtue of the Fischer-Tropsch process, a Fischer- Tropsch derived gasoil has essentially no, or undetectable levels of, sulphur and nitrogen. Compounds containing these heteroatoms tend to act as poisons for Fischer-Tropsch catalysts and are therefore removed from the synthesis gas feed. Further, the process as usually operated produces no or virtually no aromatic components.

For example, the aromatics content of a Fischer- Tropsch gasoil, as determined for instance by ASTM D4629, will typically be below 1% w/w, preferably below 0.5% w/w and more preferably below 0.1% w/w.

Generally speaking, Fischer-Tropsch derived fuels have relatively low levels of polar components, in particular polar surfactants, for instance compared to petroleum derived fuels. It is believed that this can contribute to improved antifoaming and dehazing performance. Such polar components may include for example oxygenates, and sulphur and nitrogen containing compounds. A low level of sulphur in a Fischer-Tropsch derived fuel is generally indicative of low levels of both oxygenates and nitrogen-containing compounds, since all are removed by the same treatment processes.

The Fischer-Tropsch derived gasoil fuel used in the present invention is a liquid hydrocarbon middle distillate fuel with a distillation range similar to that of a petroleum derived diesel, that is typically within the 160°C to 400°C range, preferably with a T95 of 360°C or less. Again, Fischer-Tropsch derived fuels tend to be low in undesirable fuel components such as sulphur, nitrogen and aromatics.

The Fischer-Tropsch derived gasoil fuel used in the present invention will typically have a density (as measured by EN ISO 12185) of from 0.76 to 0.80, preferably from 0.77 to 0.79, more preferably from 0.775 to 0.785 g/cm³ at 15°C.

The Fischer-Tropsch derived gasoil fuel used in the present invention preferably has a cetane number (ASTM D613) of greater than 70, suitably from 70 to 85, most suitably from 70 to 77.

The Fischer-Tropsch derived gasoil fuel used in the present invention preferably has a kinematic viscosity at 40°C (as measured according to ASTM D445) in the range from 2.0 mm²/s to 5.0 mm²/s, preferably from 2.5 mm²/s to 4.0 mm²/s.

The Fischer-Tropsch derived gasoil used in the present invention preferably has a sulphur content (ASTM D2622) of 5 ppmw (parts per million by weight) or less, preferably of 2 ppmw or less.

The Fischer-Tropsch derived gasoil fuel as used in the present invention is that produced as a distinct finished product, that is suitable for sale and used in applications that require the particular characteristics of a gasoil fuel. In particular, it exhibits a distillation range falling within the range normally relating to Fischer-Tropsch derived gasoil fuels, as set out above.

A fuel composition according to the present invention may include a mixture of two or more Fisher- Tropsch derived gasoil fuels.

In accordance with the present invention, the Fischer-Tropsch derived components used herein (i.e. the Fischer-Tropsch derived gasoil) will preferably comprise no more than 3% w/w, more preferably no more than 2% w/w, even more preferably no more than 1% w/w of cycloparaffins (naphthenes), by weight of the Fischer-Tropsch derived component.

The Fischer-Tropsch derived components used herein (i.e. the Fischer-Tropsch derived gasoil) preferably comprise no more than 1% w/w, more preferably no more than 0.5% w/w, of olefins, by weight of the Fischer-Tropsch derived component.

The diesel fuel compositions described herein are particularly suitable for use as a diesel fuel, and can be used for arctic applications, as winter grade diesel fuel due to the excellent cold flow properties.

For example, a cloud point of -10^°C or lower (EN 23015) or a cold filter plugging point (CFPP) of -20^°C or lower (as measured by EN 116) may be possible with fuel compositions herein.

The diesel fuel compositions described herein may comprise a diesel base fuel in addition to a paraffinic gasoil.

The diesel base fuel may be any petroleum derived diesel suitable for use in an internal combustion engine, such as a petroleum derived low sulphur diesel comprising <50 ppm of sulphur, for example, an ultra-low sulphur diesel (ULSD) or a zero sulphur diesel (ZSD).

Preferably, the low sulphur diesel comprises <10 ppm of sulphur.

The petroleum derived low sulphur diesel preferred for use in the present invention will typically have a density from 0.81 to 0.865, preferably 0.82 to 0.85, more preferably 0.825 to 0.845 g/cm³ at 15^°C; a cetane number (ASTM D613) of at least 51; and a kinematic viscosity (ASTM D445) from 1.5 to 4.5, preferably 2.0 to 4.0, more preferably from 2.2 to 3.7 mm²/s at 40^°C.

In one embodiment, the diesel base fuel is a conventional petroleum-derived diesel.

Generally speaking, in the context of the present invention the fuel composition may be additivated with fuel additives. Unless otherwise stated, the (active matter) concentration of each such additive in a fuel composition is preferably up to 10000 ppmw, more preferably in the range from 5 to 1000 ppmw, advantageously from 75 to 300 ppmw, such as from 95 to 150 ppmw. Such additives may be added at various stages during the production of a fuel composition; those added to a base fuel at the refinery for example might be selected from anti-static agents, pipeline drag reducers, middle distillate flow improvers (MDFI) (e.g., ethylene/vinyl acetate copolymers or acrylate/maleic anhydride copolymers), lubricity enhancers, anti-oxidants and wax anti-settling agents.

The fuel composition may include a detergent, by which is meant an agent (suitably a surfactant) which can act to remove, and/or to prevent the build-up of, combustion related deposits within an engine, in particular in the fuel injection system such as in the injector nozzles. Such materials are sometimes referred to as dispersant additives. Where the fuel composition includes a detergent, preferred concentrations are in the range 20 to 500 ppmw active matter detergent based on the overall fuel composition, more preferably 40 to 500 ppmw, most preferably 40 to 300 ppmw or 100 to 300 ppmw or 150 to 300 ppmw. Detergent-containing diesel fuel additives are known and commercially available. Examples of suitable detergent additives include polyolefin substituted succinimides or succinamides of polyamines, for instance polyisobutylene succinimides or polyisobutylene amine succinamides, aliphatic amines, Mannich bases or amines and polyolefin (e.g. polyisobutylene) maleic anhydrides. Particularly preferred are polyolefin substituted succinimides such as polyisobutylene succinimides.

Other components which may be incorporated as fuel additives, for instance in combination with a detergent, include lubricity enhancers; dehazers, e.g. alkoxylated phenol formaldehyde polymers; anti-foaming agents (e.g. commercially available polyether-modified polysiloxanes); ignition improvers (cetane improvers) (e.g. 2-ethylhexyl nitrate (EHN), cyclohexyl nitrate, di-tert-butyl peroxide and those disclosed in US4208190 at column 2, line 27 to column 3, line 21); anti-rust agents (e.g. a propane-1,2- diol semi-ester of tetrapropenyl succinic acid, or polyhydric alcohol esters of a succinic acid derivative, the succinic acid derivative having on at least one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group containing from 20 to 500 carbon atoms, e.g. the pentaerythritol diester of polyisobutylene-substituted succinic acid); corrosion inhibitors; reodorants; anti-wear additives; anti oxidants (e.g. phenolics such as 2,6-di-tert-butylphenol, or phenylenediamines such as N,N'-di-sec-butyl-p- phenylenediamine); metal deactivators; static dissipator additives; and mixtures thereof.

It is preferred that the additive contains an anti foaming agent, more preferably in combination with an anti-rust agent and/or a corrosion inhibitor and/or a lubricity additive.

It is particularly preferred that a lubricity enhancer be included in the fuel composition, especially when it has a low (e.g. 500 ppmw or less) sulfur content. The lubricity enhancer is conveniently present at a concentration from 50 to 1000 ppmw, preferably from 100 to 1000 ppmw, based on the overall fuel composition.

The (active matter) concentration of any dehazer in the fuel composition will preferably be in the range from 1 to 20 ppmw, more preferably from 1 to 15 ppmw, still more preferably from 1 to 10 ppmw and advantageously from 1 to 5 ppmw. The (active matter) concentration of any ignition improver present will preferably be 600 ppmw or less, more preferably 500 ppmw or less, conveniently from 300 to 500 ppmw.

The present invention may in particular be applicable where the fuel composition is used or intended to be used in a direct injection diesel engine, for example of the rotary pump, in-line pump, unit pump, electronic unit injector or common rail type, or in an indirect injection diesel engine. The fuel composition herein may be suitable for use in heavy-and/or light-duty diesel engines, and in engines designed for on-road use or off-road use.

In order to be suitable for at least the above uses, the diesel fuel composition herein preferably has one or more of the following characteristics:

-a kinematic viscosity at 40°C of 1.9 mm²/s or greater, more preferably in the range from 1.9 to 4.5 mm²/s;

-a density of 800 kg/m³ or greater, more preferably in the range from 800 to 860, even more preferably 800 to 845 kg/m³;

-a T95 of 360°C or less;

-a cloud point in the range from 0°C to -13°C, more preferably from -5°C to -8°C;

-a CFPP in the range of from -8°C to -30°C, more preferably from -15°C to -20°C.

The invention is illustrated by the following non limiting examples.

Examples Example 1

Two different fuels were used in Example 1. Fuel 1 was a GTL gasoil containing 10 ppm of a hindered phenol antioxidant (2,6-di-tert-butyl-4-methylphenol otherwise known as BHT). Table 1 shows the physical and compositional characteristics of the GTL gasoil (Fuel 1) used in Example 1. The GTL gasoil (Fuel 1) was obtained from Pearl GTL, Ras Laffan and is commercially available from the Shell/Royal Dutch Group of Companies.

Fuel 2 was a conventional diesel fuel (Diesel B7). The physical characteristics of the conventional diesel fuel (Diesel B7) used in the examples (Fuel 2) is shown in Table 2. As used herein "Diesel B7" means diesel base fuel containing 7% biofuel components.

Table 1: Physical and compositional characteristics of

Fuel 1 (GTL gasoil) (EN15940)

Table 2 (Physical and Compositional Characteristics of Fuel 2 (Diesel B7) (EN590)

Test Method

The vehicle used in Example 1 was a modern technology (Euro VI) Mercedes Actros HGV truck which has an SCR system fitted to it. AdBlue (RTM) (defined by the specification ISO 22241), readily available on the European market, was used as the SCR reagent for the SCR system.

Prior to each test run there was a forced regeneration of the DPF (Diesel Particulate Filter) to ensure that the aftertreatment was in the same state at the start of each test. For each test run the truck was run around an oval test track for 3 hours at 89 kph. During each test run, there was the ability to monitor and record various output parameters from the ECU (Engine Control Unit) which gave the instantaneous state of the engine, DPF and SCR aftertreatment systems. Such ECU parameters included SCR status, SCR reagent metering amount, SCR reagent tank level, NOx pre-catalyst and NOx post-catalyst .

The average amount of SCR reagent used in Example 1 versus fuel type is shown in Table 3 below.

Table 3

From the results in Table 3, it can be seen that the GTL fuel is conferring a 0.08 (8%) benefit over and above the

B7 diesel fuel. Figure 1 is a graph of the results set out in Table 3.

Example 2

Model calculations were prepared to illustrate the the benefits of GTL fuel in reducing the number of fills of SCR reagent in one year. Knowing various parameters of a vehicle allows the number of SCR reagent fills per year to be calculated, and thus the reduction in the number of fills when GTL fuel is used. For the purposes of these calculations, the SCR reagent is AdBlue (RTM).

In the following calculations the following abbreviations are used:

AFC = Annual Fuel Consumption in litres ATV = AdBlue Tank Volume = AdBlue consumption as a fraction of fuel consumption, taken as 0.05 (i.e. 5%) b= AdBlue consumption benefit from GTL, expressed as a fraction

AAF = AdBlue fills in one year

RAF = Reduction in AdBlue fills in one year

AAF and RAF can be expressed by the following equations: aAFC

AAF =

ATV

These equations can now be applied to typical Medium Haul and Long Haul vehicles to calculate the expected benefits in reducing the number of AdBlue fills in one year through the use of GTL fuel.

The following assumptions were made in the calculations :

For these classes of vehicles, AdBlue consumption is typically 4% to 6% of fuel consumption so a figure of 5% has been used, i.e. is taken to be 0.05.

144,000 miles is typical for the annual distance covered per truck (Long haul), yielding an annual fuel consumption of 100716L, yielding an annual AdBlue consumption of 5036L. 72,000 miles is typical for the annual distance covered per truck (Medium haul), yielding an annual fuel consumption of 28968L, yielding an annual AdBlue consumption of 1448L. - The Fleet size was taken as 30 vehicles.

The value of b (AdBlue consumption benefit from GTL fuel, which was experimentally determined as 0.08 from Example 1 (i.e. 8%)). The various benefits of GTL usage will vary according to the sensitivity of the engine to the chemistry of GTL. For example, regulated emissions

(PM, NOx, HC, CO) measurements (in the open literature) show a wide range of benefits according to a number of factors, including test conditions and engine type. It can be reasonably supposed that a large level of variation will also be seen in the AdBlue requirement percentage benefits seen in different Engine-SCR combination systems. For that reason the value of b has taken into account a reasonable level of variation. Thus b takes values in the range from 2% to 30%, with intermediate values of 8% and 20%.

The results of these model calculations are shown in

Table 4 below.

Table 4: Reduction in Annual Adblue Filling Events for Long Haul and Medium Haul Lorries

Example 3

Two different fuels were used in Example 3. Fuel 3 was a GTL gasoil containing 10 ppm of a hindered phenol antioxidant (2,6-di-tert-butyl-4-methylphenol otherwise known as BHT). Table 5 shows the physical and compositional characteristics of the GTL gasoil (Fuel 3) used in Example 3. The GTL gasoil (Fuel 3) was obtained from Pearl GTL, Ras Laffan and is commercially available from the Shell/Royal Dutch Group of Companies. Fuel 4 was a conventional diesel fuel (Diesel B7).

The physical characteristics of the conventional diesel fuel (Diesel B7) used in the example (Fuel 4) are also shown in Table 5. As used herein "Diesel B7" means diesel base fuel containing 7% biofuel components. Table 5: Physical and compositional characteristics of

Fuel 3 (GTL gasoil) (EN15940) and of Fuel 4 (Diesel B7) (EN590)

Test Method

The objective of Example 3 was to generate further experimental data to support the results obtained in Example 1, in particular by expanding the test to a larger number of vehicles, specifically a fleet of four.

Four vehicles were used in Example 3. These were modern technology (three of Euro VI-C, one of Euro Vl-D) Mercedes Actros HGV trucks which have an SCR system fitted to them. AdBlue (RTM) (defined by the specification ISO 22241), readily available on the European market, was used as the SCR reagent for the SCR system of each vehicle.

Prior to each test run there was a forced regeneration of the DPF (Diesel Particulate Filter) to ensure that the aftertreatment was in the same state at the start of each test. Test runs of the four trucks were of an extended duration in comparison to the 3 hour test runs of Example 1. For a test run each of the four trucks was run around an oval test track at 70 kph using 2 driver shifts per day until the DPF (Diesel Particulate Filter) soot loading had reached the DPF regeneration point. For some of the truck/fuel combinations this meant a test run in excess of 40 hours at 70kph. (Breaks occurred at approximately every 2-2.5 hours to accommodate driver breaks or shift changeover periods, during these the engines were left at idle. Overnight the vehicles were stationary for an 8-hour period and the engines were switched off). During each test run, there was the ability to monitor and record various output parameters from the ECU (Engine Control Unit) which gave the instantaneous state of the engine, DPF and SCR aftertreatment systems. Such ECU parameters included SCR status, SCR reagent metering amount, SCR reagent tank level, NOx pre-catalyst and NOx post-catalyst .

The average amount of SCR reagent used in Example 3 versus fuel type for each of the four vehicles is shown in Table 6 below.

Table 6

From the results in Table 6, it can be seen that the GTL fuel is conferring benefit in the range of 1.1% to 15.2% over and above the B7 diesel fuel.

Discussion

As can be seen from the results in Table 3, the graph in Figure 1 and Table 6, there is a significant reduction in the amount of SCR reagent required in the case of the paraffinic GTL fuel compared with the conventional diesel B7 fuel.

As is demonstrated in the model calculations in Table 4, there is a large range in the reduction of required AdBlue fills in a fleet per year when using paraffinic GTL fuel compared to B7 diesel fuel. The model values cover a range of tank sizes and AdBlue consumption rate benefits. The reduction in the number of SCR reagent vehicle fills per year provides the advantage of minimising a user's exposure to a corrosive liquid.

Claims

C LA IM S

1. Use of a paraffinic gasoil in a diesel fuel composition for reducing the amount of SCR reagent required by an SCR system fitted to a compression ignition internal combustion engine.

2. Use according to Claim 1 wherein the SCR reagent is selected from urea, ammonia and ammonium salts, and mixtures thereof.

3. Use according to Claim 1 or 2 wherein the SCR reagent is urea.

4. Use according to any of Claims 1 to 3 wherein the paraffinic gasoil comprises greater than 95 wt.% paraffins, preferably greater than 98 wt.% paraffins, based on the total weight of the paraffinic gasoil.

5. Use according to any of Claims 1 to 4 wherein the paraffinic gasoil is selected from a Fischer-Tropsch derived gas oil and a hydrotreated vegetable oil (HVO) derived gasoil, and mixtures thereof.

6. Use according to any of Claims 1 to 5 wherein the paraffinic gasoil is a Fischer-Tropsch derived gasoil.

7. Use according to Claim 5 or 6 wherein the Fischer- Tropsch derived gas oil is present at a level of from 50 %v/v to 100 %v/v, based on the total diesel fuel composition .

8. Use according to any of Claims 5 to 7 wherein the Fischer-Tropsch derived gas oil has a kinematic viscosity at 40°C of in the range from 2.0 to 5.0 mm²/s and a density in the range from 0.76 to 0.80 g/cm³.

9. Use according to any of Claims 1 to 8 wherein the diesel fuel composition additionally comprises a diesel base fuel.

10. Method for reducing the amount of SCR reagent required by an SCR system fitted to a compression ignition internal combustion engine, which method comprises a step of introducing into said engine a diesel fuel composition which comprises a paraffinic gasoil.

11. Use of a paraffinic gasoil in a diesel fuel composition for reducing the number of SCR reagent vehicle fills per year.