FUEL COMPOSITIONS

Abstract

A diesel fuel composition including (a) a quaternary ammonium salt additive; and (b) one or more nitrogen-free detergents; wherein the quaternary ammonium salt additive includes the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

Claims

1. A diesel fuel composition comprising (a) a quaternary ammonium salt additive; and (b) one or more nitrogen-free detergents; wherein the quaternary ammonium salt additive comprises the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group: wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

2. A method of Improving the performance of a diesel engine, the method comprising combusting in the engine a diesel fuel composition comprising (a) a quaternary ammonium salt additive; and (b) one or more nitrogen-free detergents; wherein the quaternary ammonium salt additive comprises the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which Includes a tertiary amine group; wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

3. A use of a combination of (a) a quaternary ammonium salt additive and (b) one or more nitrogen-free detergents to improve the performance of a diesel engine; wherein the quaternary ammonium salt additive comprises the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1.2 succinic acid moieties.

4. The composition of claim 1, wherein the hydrocarbyl substituted succinic acid derived acylating agent is a polyisobutene-substituted succinic acid or succinic anhydride wherein the polyisobutene substituent has a number average molecular weight of between 450 to 2300.

5. The composition of claim 1, wherein the compound able to react with the hydrocarbyl substituted succinic acid derived acylating agent and which includes a tertiary amine group comprises one or more compounds formed by the reaction of a hydrocarbyl-substituted acylating agent and an amine of formula (I) or (II): ##STR00011## wherein R.sup.2 and R.sup.3 are the same or different alkyl, alkenyl, aryl, alkaryl or aralkyl groups having from 1 to 22 carbon atoms; X is an optionally substituted alkylene group having from 1 to 20 carbon atoms; n is from 0 to 20; m is from 1 to 5; and R.sup.4 is hydrogen or a C1 to Cri alkyl group.

6. The composition of claim 5, wherein X is a propylene group.

7. The composition of claim 1, wherein the quaternising agent used to prepare the quaternary ammonium salt addive (a) is selected from the group consisting of an ester of a carboxylic acid, dialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates, hydrocarbyl substituted epoxides optionally in combination with an acid, alkyl halides, alkyl sulfonates, sultones, hydrocarbyl substituted phosphates, hydrocarbyl substituted borates, alkyl nitrites, alkyl nitrates, hydroxides, N-oxides, chloroacetic acid or salts thereof, or mixtures thereof.

8. The composition of claim 1, wherein the quaternising agent used to prepare the quaternary ammonium salt addive (a) is selected from the group consisting of dialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates, hydrocarbyl substituted epoxides in combination with an acid, alkyl halides, alkyl sulfonates, sultones, hydrocarbyl substituted phosphates, hydrocarbyl substituted borates, N-oxides, chloroacetic acid or salts thereof, or mixtures thereof

9. The composition of claim 1, wherein the quaternising agent used to prepare the quaternary ammonium salt addive (a) is a compound of formula (III): ##STR00012## wherein R is an optionally substituted alkyl, alkenyl, aryl or alkylaryl group and R.sup.1 is a C.sub.1 to C.sub.2 alkyl, aryl or alkylaryl group.

10. The composition of claim 9, wherein the quaternizing agent is selected from dimethyl oxalate, methyl 2-nitrobenzoate and methyl salicylate.

11. The composition of claim 9, wherein the quaternizing agent is an ester of a polycarboxylic acid.

12. The composition of claim 1, wherein component (b) comprises a copolymeric nitrogen-free detergent comprising -olefin derived units and maleic anhydride derived units.

13. The composition of claim 1, wherein component (b) comprises the reaction product of an alcohol having at least 5 carbon atoms and a polycarboxylic acid having no more than 5 carbon atoms per carboxylic acid group, or an anhydride thereof selected from citric acid, itaconic acid, citraconic acid, 2-methylene glutaric acid, 2-methylene adipic acid, isocitric acid, 2-hydroxycitric acid, malic acid, tartaric acid, 2-hydroxyadipic acid, 2-hydroxyglutaric acid, aconitic acid, and anhydrides and/or Isomers thereof.

14. The composition of claim 1, wherein component (b) comprises the reaction product of an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol or formula H(OR).sub.nOR.sup.1, wherein R is an optionally substituted alkylene group; R.sup.1 is hydrogen or an optionally substituted hydrocarbyl group, and n is 0 or a positive integer; wherein n is not 0 when R.sup.1 is hydrogen.

15. The composition of claim 1, wherein component (b) comprises a hydrocarbyl substituted succinic acid.

16. The composition of claim 1, wherein component (b) comprises a polymer of formula (IV): ##STR00013## wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

17. The method of claim 2, wherein the engine is a diesel engine having a fuel injection system which comprises a high pressure fuel injection (HPFI) system with fuel pressures greater than 1350 bar.

18. The method of claim 2, wherein improvement in performance Is achieved by combating deposits in the engine.

19. The method of claim 18, which combats internal diesel injector deposits.

20. The method of claim 18, which combats external diesel Injector deposits, including injector nozzle deposits and injector tip deposits.

21. The method of claim 18, which combats fuel filter deposits.

22. The method of claim 2, wherein the improvement In performance Is a power gain compared to when combusting an unadditised base fuel and with clean injectors.

23. The method of claim 2, which achieves keep clean performance.

24. The method of claim 2, which achieves dean up performance.

Description

EXAMPLE 1PREPARATION OF POIYISOBUTYIENESUCCINIC ANHYDRIDE (PIBSA)INVENTIVE

[0337] 700 g (0.7 mol) of polyisobutylene (Mn 1000) was charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer. The starting material was heated to 120 C. with stirring and nitrogen inerting was repeated. The reaction temperature was increased to 190 C. and maleic anhydride (82.4 g, 0.84 mol, 1.2 eq) was charged over 1 hour. After maintaining a temperature of 190 C. for a further 1 hour, the temperature was increased to 200-208 C. and held in this range for 8 hours. Vacuum (<30 mbar) was then applied for 2.5 hrs, whilst maintaining the reaction temperature, which reduced the level of residual maleic anhydride to 0.05 wt %. The reaction mass was cooled to 80 C. then discharged from the reactor.

EXAMPLE 2PREPARATION OF PIBSACOMPARATIVE

[0338] The synthesis procedure was substantially identical to Example 1 and used the same grade of polyisobutylene (Mn 1000). The charge of maleic anhydride was reduced (1 eq relative to polyisobutylene) and the reaction was held between 190-210 C. during the 8 hour heating period. Residual maleic anhydride was also measured as 0.05 wt %.

[0339] The properties of the reaction products of Examples 1 and 2 are summarised in Table 1.

TABLE-US-00001 TABLE 1 Molecular weight of PIB Acid value Unreacted PIB starting Example (mmolH+/g) (wt %) material (Mn) P value 1 1.89 18.5 1000 1.31 2 1.68 20.2 1000 1.17

EXAMPLE 3ADDITIVE Q1INVENTIVE

[0340] PIBSA prepared according to Example 1 was charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer and heated to 120 C. 3-(dimethylamino)propylamine (DMAPA) (1 eq relative to anhydride groups) was charged slowly, maintaining the reaction temperature between 120-130 C. After stirring at 120 C. for a further 1 hr, the reaction temperature was increased to 140 C. and held for 3 hrs with concurrent distillation of water. Methyl salicylate (2.1 eq relative to anhydride groups) was added in a single portion and heating was continued at 140 C. for 10 hours. The reaction mass was diluted with Aromatic 150 solvent to provide an overall solids content of 60 wt % prior to discharging from the reactor.

EXAMPLE 4ADDITIVE Q2COMPARATIVE

[0341] PIBSA prepared according to Example 2 was charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer and heated to 90 C. 3-(dimethylamino)propylamine (DMAPA) (1 eq relative to anhydride groups) was charged slowly, maintaining the reaction temperature between 90-100 C. After stirring at 90-100 C. for a further 1 hr, the reaction temperature was increased to 140 C. and held for 4 hrs with concurrent distillation of water. 2-ethylhexanol was added to adjust the solids content to 60 wt % then methyl salicylate (1 eq relative to anhydride groups) was added in a single portion and heating was continued at 140 C. for 15 hours. The reaction mass was cooled to 60 C. prior to discharging from the reactor.

EXAMPLE 5ADDITIVE Q3INVENTIVE

[0342] PIBSA according to Example 1 was charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer and heated to 120 C. 3-(dimethylamino)propylamine (DMAPA) (1 eq relative to anhydride groups) was charged slowly, maintaining the reaction temperature between 120-130 C. After stirring at 120 C. for a further 1 hr, the reaction temperature was increased to 140 C. and held for 3 hrs with concurrent distillation of water. The reaction mass was cooled to room temperature, then acetic acid (0.71 eq relative to anhydride groups), 2-ethylhexanol (1.34 eq relative to anhydride groups) and water (0.81 eq relative to anhydride groups) were added. The reaction mass was heated to 75 C. and propylene oxide (2.39 eq relative to anhydride groups) was added over 3 hrs via a dropping funnel. Heating was continued for 4 hrs. The reaction mass was diluted with Aromatic 150 solvent to provide an overall solids content of 60 wt % prior to discharging from the reactor.

EXAMPLE 6ADDITIVE Q4

[0343] PIBSA according to Example 2 was used. Formation of the DMAPA succinimide and subsequent quaternization using propylene oxide/AcOH was carried out in identical manner to Example 5. Reactant charges were calculated relative to anhydride groups in the PIBSA starting material.

EXAMPLE 7ADDITIVE Q5INVENTIVE

[0344] PIBSA according to Example 1 (1 part) and Caromax 20 (1 part) were charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer and heated to 80 C. to ensure proper mixing, then cooled to room temperature. 3-(dimethylamino)propylamine (DMAPA) (1 eq relative to anhydride groups in the PIBSA starting material) was added over 3 hrs, maintaining the reaction temperature below 40 C. The reaction mass was stirred for a further 4 hrs, then propylene oxide (2 eq relative to anhydride groups) was added over 3 hrs, then the reaction mass stirred at room temperature for 4 hrs. After nitrogen sparging to remove residual propylene oxide, the reaction mass was discharged from the reactor.

EXAMPLE 8ADDITIVE Q6COMPARATIVE

[0345] PIBSA according to Example 2 was used. Formation of the DMAPA succinamide and subsequent quaternization using propylene oxide was carried out in identical manner to Example 7. Reactant charges were calculated relative to anhydride groups.

EXAMPLE 9ADDITIVE A1

[0346] Additive A1 was prepared as follows:

[0347] A mixture of alkenes having 20 to 24 carbon atoms was heated with 1.2 molar equivalents of maleic anhydride. On completion of the reaction excess maleic anhydride was removed by distillation. The anhydride value of the substituted succinic anhydride product was measured as 2.591 mmolg.sup.1.

[0348] This product was then heated with one molar equivalent of 2-ethyl hexanol, and the reaction was monitored by FTIR.

EXAMPLE 10ADDITIVE A2

[0349] Additive A2 was prepared by hydrolysing the compound prepared according to example 2. Hydrolysis was carried out by heating the material obtained in example 2 with a slight molar excess of water at 90 to 95 C. The acid value of the product was determined to be 1.50 mmol/g by titration against 0.1N lithium methoxide in toluene.

EXAMPLE 11ADDITIVE A3

[0350] A 500 mL, 3-neck round bottom flask was fitted with a magnetic stirrer, condenser, DeanStark apparatus, gas inlet/outlet, stirrer hotplate and oil bath. Oleyl alcohol (206.19 g, 0.768 mol), itaconic acid (100 g, 0.768 mol) and p-toluenesulfonic acid (0.439 g, 2.30 mmol) were combined and heated to 165 C. (internal temperature). The reaction mass was held at 165 C. for 6 hours and water was removed. The reaction mass became homogenous and a colour change to orange was observed. After cooling to room temperature, the reaction mass was transferred to a 2 L separating funnel and toluene (270 mL) was added. The toluenediluted reaction mass was washed with 1:1 watermethanol (1540 mL), the organic phase separated and volatiles removed on the rotary evaporator, providing a viscous orange liquid (257.6 g).

[0351] The acid value of Additive A3 was 2.0 mmolH+/g.

EXAMPLE 12ADDITIVE A4

[0352] Additive A4 was prepared by following the procedure set out in synthesis example 1 of US2017/0130153.

EXAMPLE 13

[0353] Additive formulations F1 to F10 were prepared by mixing 50:50 ratios by weight of the crude products from examples 3-12 as identified table 2.

TABLE-US-00002 TABLE 2 A1 A2 A3 A4 Q1 F7 F1 F8 F9 Q2 F10 F2 Q3 F3 Q4 F4 Q5 F5 Q6 F6

EXAMPLE 14

[0354] Fuel compositions were prepared by adding additives formulations F1 to F10 to diesel fuel.

[0355] The diesel fuel complied with the RF06 base fuel, the details of which are given in table 3 below.

TABLE-US-00003 TABLE 3 Limits Property Units Min Max Method Cetane Number 52.0 54.0 EN ISO 5165 Density at 15 C. kg/m.sup.3 833 837 EN ISO 3675 Distillation 50% v/v Point C. 245 95% v/v Point C. 345 350 FBP C. 370 Flash Point C. 55 EN 22719 Cold Filter Plugging C. 5 EN 116 Point Viscosity at 40 C. mm.sup.2/sec 2.3 3.3 EN ISO 3104 Polycyclic Aromatic % m/m 3.0 6.0 IP 391 Hydrocarbons Sulphur Content mg/kg 10 ASTM D 5453 Copper Corrosion 1 EN ISO 2160 Conradson Carbon Residue on % m/m 0.2 EN ISO 10370 10% Dist. Residue Ash Content % m/m 0.01 EN ISO 6245 Water Content % m/m 0.02 EN ISO 12937 Neutralisation (Strong Acid) mg KOH/g 0.02 ASTM D 974 Number Oxidation Stability mg/mL 0.025 EN ISO 12205 HFRR (WSD1, 4) m 400 CEC F-06-A-96 Fatty Acid Methyl Ester prohibited

EXAMPLE 15

[0356] The ability of additives of the invention to remove Internal Diesel Injector Deposits (IDIDs) may be measured according to the test method CEC F-110-16, available from the Co-ordinating European Council. The test uses the PSA DW10C engine.

[0357] The engine characteristics as follows:

TABLE-US-00004 Design: Four cylinders in line, overhead camshaft, variable geometry turbocharger with EGR Capacity: 1997 cm.sup.3 Combustion chamber: Four valves, bowl in piston, direct injection Power: 120 kW @ 3750 rpm Torque: 340 Nm @ 2000 rpm Injection system: Common rail with solenoid type injectors Delphi Injection System Emissions control: Conforms to Euro V limit values when combined with exhaust gas post-treatment system.

[0358] The test fuel (RF06) is dosed with 0.5 mg/kg Na in the form of Sodium Naphthenate+10 mg/kg Dodecyl Succinic Acid (DDSA).

[0359] The test procedure consists of main run cycles followed by soak periods, before cold starts are carried out.

[0360] The main running cycle consist of two speed and load set points, repeated for 6 hrs, as seen below.

TABLE-US-00005 Step Speed (rpm) Torque (N .Math. m) Duration (s) 1 3750 280 1470 1 - Ramp .fwdarw.2 30 2 1000 10 270 2 - Ramp .fwdarw.1 30 The ramp times of 30 seconds are included in the duration of each step.

[0361] During the main run, parameters including, Throttle pedal position, ECU fault codes, Injector balance coefficient and Engine stalls are observed and recorded.

[0362] The engine is then left to soak at ambient temperature for 8 hrs.

[0363] After the soak period the engine is re-started. The starter is operated for 5 seconds; if the engine fails to start the engine is left for 60 seconds before a further attempt. A maximum of 5 attempts are allowed.

[0364] If the engine starts the engine is allowed to ide for 5 minutes. Individual exhaust temperatures are monitored and the maximum Temperature Delta is recorded. An increased variation in Cylinder-to-Cylinder exhaust temperatures is a good indication that injectors are suffering from IDID. Causing them to either open slowly or stay open to long.

[0365] An example below of all exhaust temperatures with <30 C. deviation, indicating no sticking caused by IDID.

The complete test comprises of 6 Cold Starts, although the Zero hour Cold Start does not form part of the Merit Rating and 5 6 hr Main run cycles, giving a total of 30 hrs engine running time. The recorded data is inputted into the Merit Rating Chart. This allows a Rating to be produced for the test. Maximum rating of 10 shows no issues with the running or operability of the engine for the duration of the test.
An example below:

TABLE-US-00006 Cold start Main run 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 25 25 25 indicates data missing or illegible when filed

[0366] The propensity of the test fuel to cause injector deposits (IDID) is evaluated through the following criteria: [0367] Cold start parameters: [0368] 1. Number of failed starts. [0369] 2. Exhaust temperature deviation from standard value for cylinders 1 to 4 [0370] Main run parameters [0371] 1. Number of engine stalls [0372] 2. Number of IDID related ECU faults generated during main run [0373] 3. Pedal position drift on low speed phases [0374] 4. Injector balancing [0375] Note: 1st Cold start (#0) is run with Flush fuel and is not rated

[0376] The rating can be summarized as follows: [0377] 1/Cold Start (for start #1 to #5): [0378] Startability rating: [0379] 1st start: merit5/each fail brings a 1 merit discount.

[0380] Maximum Exhaust Ports Temperature deviation rating: [0381] merit5 if T<30 C./2 if 30 C.<T<50 C./0 if T>50 C.

[0382] Cold Start Rating range: 0.fwdarw.10 for each Cold Start (5 Cold Starts rated in total) [0383] 2/Main Run (for run #1 to #5):

[0384] Operability rating: [0385] merit5 if no stall and no IDID related ECU Fault, each IDID related ECU fault brings a 1 merit discount (after 5th ECU Fault Reset.fwdarw.Next cold start). [0386] merit0 if stall (Then.fwdarw.Next Cold Start).

[0387] Maximum Pedal Position: [0388] merit5 if P<25%/2 if 25%<P<40%/%/0 if P>40%

[0389] Maximum Injector Balancing Factror deduction: [0390] merit5 if IB<20 rpm/2 if 30 rpm<IB<20 rpm/0 if IB>30 rpm [0391] Main Run Rating range: 0.fwdarw.5 for each Main Run (5 in total) [0392] Maximum global rating value: 75 (ie: 5 10+55). [0393] Global rating=10(Cold Start+Main Run Rating values)/75 [0394] Resulting in 0 to 10 merIt scale

EXAMPLE 16

[0395] The ability of additives of the invention to clean up IDIDs may be assessed according to a modification of the DW10C test described in example 12.

[0396] The In-House Clean-Up Method developed starts by running the engine using reference diesel (RF06) dosed with 0.5 mg/kg Na+10 mg/Kg DDSA until an exhaust temperature Delta of >50 C. is observed on the Cold Start. This has repeatedly been seen on the 3.sup.rd Cold Start which follows the second main run, 12 hrs total engine run time.

[0397] Once the increased Exhaust temperature Delta is observed, the engine fuel supply is swapped to reference diesel, dosed with 0.5 mg/kg Na (as sodium naphthenate)+10 mg/kg DDSA+ the Candidate sample. The fuel is flushed through to the engine and allowed to commence with the next Main run.

[0398] The ability of the Candidate additive to prevent any further increase in deposits or to remove the deposits can then be determined as the test continues.

EXAMPLE 17

[0399] The performance of fuel compositions of example 14 in modern diesel engines having a high pressure fuel system may be tested according to the CECF-98-08 DW 10 method. This is referred to herein as the DW10B test.

[0400] The engine of the injector fouling test is the PSA DW10BTED4. In summary, the engine characteristics are: [0401] Design: Four cylinders in line, overhead camshaft, turbocharged with EGR [0402] Capacity: 1998 cm.sup.3 [0403] Combustion chamber: Four valves, bowl in piston, wall guided direct injection [0404] Power: 100 kW at 4000 rpm [0405] Torque: 320 Nm at 2000 rpm [0406] Injection system: Common rail with piezo electronically controlled 6-hole injectors. Max. pressure: 1600 bar (1.610.sup.8 Pa). Proprietary design by SIEMENS VDO [0407] Emissions control: Conforms with Euro IV limit values when combined with exhaust gas post-treatment system (DPF)

[0408] This engine was chosen as a design representative of the modern European high-speed direct injection diesel engine capable of conforming to present and future European emissions requirements. The common rail injection system uses a highly efficient nozzle design with rounded inlet edges and conical spray holes for optimal hydraulic flow. This type of nozzle, when combined with high fuel pressure has allowed advances to be achieved in combustion efficiency, reduced noise and reduced fuel consumption, but are sensitive to influences that can disturb the fuel flow, such as deposit formation in the spray holes. The presence of these deposits causes a significant loss of engine power and increased raw emissions.

[0409] The test is run with a future injector design representative of anticipated Euro V injector technology.

[0410] It is considered necessary to establish a reliable baseline of injector condition before beginning fouling tests, so a sixteen hour running-in schedule for the test injectors is specified, using non-fouling reference fuel.

[0411] Full details of the CEC F-98-08 test method can be obtained from the CEC. The coking cycle is summarised below. [0412] 1. A warm up cycle (12 minutes) according to the following regime:

TABLE-US-00007 Duration Engine Speed Step (minutes) (rpm) Torque (Nm) 1 2 idle <5 2 3 2000 50 3 4 3500 75 4 3 4000 100 [0413] 2. 8 hrs of engine operation consisting of 8 repeats of the following cycle

TABLE-US-00008 Duration Engine Speed Load Torque Boost Air After Step (minutes) (rpm) (%) (Nm) IC ( C.) 1 2 1750 (20) 62 45 2 7 3000 (60) 173 50 3 2 1750 (20) 62 45 4 7 3500 (80) 212 50 5 2 1750 (20) 62 45 6 10 4000 100 * 50 7 2 1250 (10) 20 43 8 7 3000 100 * 50 9 2 1250 (10) 20 43 10 10 2000 100 * 50 11 2 1250 (10) 20 43 12 7 4000 100 * 50 * for expected range see CEC method CEC-F-98-08 [0414] 3. Cool down to idle in 60 seconds and idle for 10 seconds [0415] 4. 4 hrs soak period

[0416] The standard CEC F-98-08 test method consists of 32 hours engine operation corresponding to 4 repeats of steps 1-3 above, and 3 repeats of step 4. ie 56 hours total test time excluding warm ups and cool downs.

EXAMPLE 18

[0417] The effectiveness of the additives of the invention in older traditional diesel engine types may be assessed using a standard industry testCEC test method No. CEC F-23-A-01.

[0418] This test measures injector nozzle coking using a Peugeot XUD9 A/L Engine and provides a means of discriminating between fuels of different injector nozzle coking propensity. Nozzle coking is the result of carbon deposits forming between the injector needle and the needle seat. Deposition of the carbon deposit is due to exposure of the injector needle and seat to combustion gases, potentially causing undesirable variations in engine performance.

[0419] The Peugeot XUD9 A/L engine is a 4 cylinder indirect injection Diesel engine of 1.9 litre swept volume, obtained from Peugeot Citroen Motors specifically for the CEC PF023 method.

[0420] The test engine is fitted with cleaned injectors utilising unflatted injector needles. The airflow at various needle lift positions have been measured on a flow rig prior to test. The engine is operated for a period of 10 hours under cyclic conditions.

TABLE-US-00009 Stage Time (secs) Speed (rpm) Torque (Nm) 1 30 1200 30 10 2 2 60 3000 30 50 2 3 60 1300 30 35 2 4 120 1850 30 50 2

[0421] The propensity of the fuel to promote deposit formation on the fuel injectors is determined by measuring the injector nozzle airflow again at the end of test, and comparing these values to those before test. The results are expressed in terms of percentage airflow reduction at various needle lift positions for all nozzles. The average value of the airflow reduction at 0.1 mm needle lift of all four nozzles is deemed the level of injector coking for a given fuel.

EXAMPLE 19

[0422] A diesel fuel composition F11 was prepared by dosing 36 ppm active additive Q1 and 20 ppm active additive A2 into an RF06 base fuel meeting the specification of example 14.

[0423] The ability of this fuel to clean up deposits on from a fouled traditional engine was demonstrated following the procedure set out in example 18.

[0424] The test method of example 18 was carried out on the base fuel to provide dirty up of the engine. The test method was then repeated but starting with the dirty injectors and using the diesel fuel composition F11 comprising 36 ppm Q1 and 20 ppm A2.

[0425] The results are shown in table 4:

TABLE-US-00010 Fuel Q1 A2 Flow reduction composition (ppm active) (ppm active) Test stage (%) Base 0 0 Dirty up 68 F11 36 20 Clean up 10.9

EXAMPLE 20

[0426] Additive A5 was prepared as follows:

[0427] To a 1L reactor charged with 2-ethylhexanol (250 g, 1.918 moles) was added toluene (215.7 g) and heated to 90 C. To the stirred liquid was added itaconic acid (250 g, 1.921 moles) and p-toluenesulfonic acid (3.31 g). The reaction was heated towards 120 C., whilst removing water by distillation over 7 hours. The products where cooled to room temperature and unreacted itaconic and p-toluenesulfonic acid removed by filtration and washing with water. The toluene was removed on a rotary evaporator to leave a yellow/orange liquid (2-ethylhexyl itaconate, 412.9 g)

[0428] To a 250 ml reactor was charged 2-ethylhexyl itaconate (120 g) was added cyclohexane (51.43 g) and the reactor contents sparged with Nitrogen for 1 hour whilst heating to 80 C. Trigonox 25-C75 (0.685 g, 0.5 wt, %, tert-Butyl peroxypivalate) was added and the reaction was mixed at 80 C. for 1 hour before adding further Trigonox 25-C75 (0.685 g) and heating for a further 3 hours at 80 C. The cyclohexane was removed on a rotary evaporator and Aromatic 150 (69.7 g) added to leave a clear amber viscous liquid (184.4 g, Mw 10932, acid value of 2.4 mmolH+/g).

EXAMPLE 21

[0429] A diesel fuel composition F12 was prepared by dosing 30 ppm active additive Q1 and 14 ppm active additive A4 into an RF06 base fuel meeting the specification of example 14.

[0430] Diesel fuel composition F12 was tested according to the CEC F-98-08 DW10B test method described in example 17, modified to measure clean up performance as outlined below.

[0431] A first 32 hour cycle was run using new injectors and RF-06 base fuel having added thereto 1 ppm Zn (as neodecanoate). This resulted in a level of power loss of 4.04% due to fouling of the injectors.

[0432] A second 32 hour cycle was then run as a clean up phase. The dirty injectors from the first phase were kept in the engine and the fuel changed to RF-06 base fuel having added thereto 1 ppm Zn (as neodecanoate) and the test additive. This restored the power to a loss of 1.78% compared to the power obtained when using clean injectors.