METHOD AND USE

Abstract

A diesel fuel composition comprising as an additive an ester compound which is the reaction product of a polyhydric alcohol of formula H(OR).sub.nOH and at least 1.5 molar equivalents of an optionally substituted polycarboxylic acid or an anhydride thereof, wherein R is an optionally substituted alkylene group and n is at least 1.

Claims

1. A diesel fuel composition comprising as an additive an ester compound which is the reaction product of a polyhydric alcohol of formula H(OR).sub.nOH and at least 1.5 molar equivalents of an optionally substituted polycarboxylic acid or an anhydride thereof, wherein R is an optionally substituted alkylene group and n is at least 1.

2. A method of combatting deposits in a diesel engine, the method comprising combusting in the engine a diesel fuel composition comprising as an additive the reaction product of a polyhydric alcohol of formula H(OR).sub.nOH and at least 1.5 molar equivalents of an optionally substituted polycarboxylic acid or an anhydride thereof, wherein R is an optionally substituted alkylene group and n is at least 1.

3. (canceled)

4. The composition, according to claim 1 wherein the optionally substituted polycarboxylic acid or anhydride thereof is a hydrocarbyl substituted succinic acid or a hydrocarbyl substituted succinic anhydride.

5. The composition according to claim 1 wherein each R is ethylene or propylene and n is from 1 to 20.

6. The composition according to claim 1 wherein the polycarboxylic acid or anhydride thereof includes an optionally substituted alkyl or alkenyl group having 6 to 100 carbon atoms.

7. The composition according to claim 1 wherein the optionally substituted polycarboxylic acid or hydrocarbyl substituted anhydride and alcohol of formula H(OR)nOH are reacted in a ratio of from 2.5:1 to 1.8:1.

8. The composition according to claim 1 wherein the additive comprises compounds of formula (C1), (C2) or (C3): ##STR00009## or isomers or mixtures thereof.

9. The composition according to claim 1 wherein the additive comprises the reaction product of an alcohol of formula H(OR).sub.nOH selected from the group consisting of: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, trehalose, sorbitol, glycerol, pentaerythritol, trimethylolpropane, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and a polyethylene or polypropylene glycol having a number average molecular weight of 300 to 1200; and at least 1.5 molar equivalents of one or more optionally substituted succinic acids or anhydrides of formula (A3) or (A4): ##STR00010## wherein each R.sup.1 is an alkyl or alkenyl group having 6 to 36 carbon atoms or a polyisobutenyl group having a number average molecular weight of from 200 to 1300.

10. The composition according to claim 1 wherein the additive comprises the reaction product an alcohol selected from the group consisting of: 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, tripropylene glycol and polypropylene glycols having a number average molecular weight of from 300 to 600; and at least 1.5 molar equivalents of a succinic acid or anhydride having a C.sub.20 to C.sub.24 alkyl or alkenyl substituent.

11. The composition according to claim 1 wherein the additive comprises a compound of formula (D): ##STR00011##

12. The composition according to claim 1 wherein the diesel engine is a modern diesel engine having a high pressure fuel system.

13. The method according to claim 2 which achieves keep clean performance.

14. The method according to claim 2 which achieves clean up performance.

15. The method according to claim 2 wherein the deposits are injector deposits.

16. The method according to claim 15 wherein the deposits are internal diesel injector deposits.

17. The composition according to claim 1 wherein the diesel fuel composition comprises less than 50 ppm sulphur by weight.

18. The composition according to claim 1 wherein the diesel fuel composition comprises biodiesel.

19. The composition according to claim 1 wherein the diesel fuel composition comprises one or more further detergents selected from the group consisting of: (i) a quaternary ammonium salt additive; (ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol; (iii) the reaction product of a carboxylic acid-derived acylating agent and an amine; (iv) the reaction product of a carboxylic acid-derived acylating agent and hydrazine; (v) a salt formed by the reaction of a carboxylic acid with di-n-butylamine or tri-n-butylamine; (vi) the reaction product of a hydrocarbyl-substituted dicarboxylic acid or anhydride and an amine compound or salt which product comprises at least one amino triazole group; and (vii) a substituted polyaromatic detergent additive.

20. The composition according to claim 1 wherein the diesel fuel composition comprises a mixture of two or more ester additives.

21. The method according to claim 2 which achieves an improvement in performance of one or more of: a reduction in power loss of the engine; a reduction in external diesel injector deposits; a reduction in internal diesel injector deposits; an improvement in fuel economy; a reduction in fuel filter deposits; a reduction in emissions; or an increase in maintenance intervals.

22. The method according to claim 21 which provides an improvement in performance in modern diesel engines having a high pressure fuel system and provides an improvement in performance in traditional diesel engines.

23. (canceled)

24. The composition according to claim 1 which further comprises one or more further additives selected from the group consisting of: lubricity improvers, corrosion inhibitors and cold flow improvers.

25. (canceled)

Description

EXAMPLE 1

[0324] Additive A1, an ester additive of the invention was prepared as follows:

[0325] 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.

[0326] This product was then heated with 0.5 molar equivalent of polypropylene glycol having a number average molecular weight of 425, and the reaction was monitored by FTIR.

[0327] Compounds A2 to A17 detailed in table 1 were prepared by an analogous method. Compound A18 was prepared from sebacic acid rather than a substituted succinic acid.

[0328] Additives A1 to A17 are believed to comprise the following compounds:

##STR00006##

For additive A20, one of the groups R.sup.1 in the above structures is C20-24 and the other is a PIB having an Mn of 1000.

[0329] Additive A18 is believed to comprise the compound:

##STR00007##

[0330] Additive A21 is believed to comprise the compound:

##STR00008##

TABLE-US-00001 TABLE 1 Compound R.sup.1 H-(OR)n-OH A1 C20-24 polypropylene glycol Mn425 A2 C20-24 polypropylene glycol Mn725 A3 C20-24 Propylene glycol A4 C20-24 polyethylene glycol Mn400 A5 C20-24 tetraethyleneglycol A6 C20-24 tripropylene glycol A7 C20-24 triethylene glycol A8 C20-24 1,2-butanediol A9 C20-24 1,3-butanediol A10 C20-24 1,4-butanediol A11 C20-24 neopentyl glycol A12 C20-24 1,6-hexanediol A13 C20-24 trimethylene glycol (1,3-propanediol) A14 C12 trimethylene glycol A15 C26-28 polypropylene glycol Mn425 A16 C20-24 dipropylene glycol A17 C20-24 Diethylene glycol A18 Sebacic acid polypropylene glycol Mn425 A19 C20-24 ethylene Glycol A20 C20-24 + 1000PIB poly(propylene glycol) Mn425 A21 Malonic acid poly(propylene glycol) Mn425

EXAMPLE 2

[0331] Diesel fuel compositions were prepared by dosing additives to aliquots all drawn from a common batch of RF06 base fuel.

[0332] The compositions were tested in a screening test which correlates with performance at combatting IDIDs as measured in the DW10C test.

[0333] In this test a fuel composition is tested using a Jet Fuel Thermal Oxidation Test equipment. In this modified test 800 ml of fuel is flowed over a heated tube at pressures of approximately 540 psi. The test duration is 2.5 hours. At the end of the test the amount of deposit obtained on the tube is compared to a reference value.

[0334] The value shown in table 1 is the percentage reduction in deposit thickness compared to base fuel.

TABLE-US-00002 TABLE 2 Average ppm thickness Compound active (% reduction) A1 (inventive) 120 97 A2 (inventive) 120 92 A3 (inventive) 120 100 A4 (inventive) 120 91 A5 (inventive) 120 99 A6 (inventive) 120 95 A7 (inventive) 120 99 A8 (inventive) 120 93 A9 (inventive) 120 89 A10 (inventive) 120 98 A11 (inventive) 120 100 A12 (inventive) 120 100 A13 (inventive) 120 99 A14 (inventive) 120 99 A15 (inventive) 120 91 A16 (inventive) 120 94 A18 (inventive) 120 87 A19 (inventive) 120 99 C1 (comparative) 120 0 C2 (comparative) 120 2

[0335] Comparative additive C1 is dodecenyl substituted succinic acid. Comparative additive C2 is a polyisobutenyl (PIB) substituted succinic acid wherein the PIB has a number average molecular weight of 1000.

[0336] Table 3 below shows the specification for RF06 base fuel.

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 D5453 Copper Corrosion 1 EN ISO 2160 Conradson Carbon % m/m 0.2 EN ISO 10370 Residue on 10% Dist. Residue Ash Content % m/m 0.01 EN ISO 6245 Water Content % m/m 0.02 EN ISO 12937 Neutralisation mg KOH/g 0.02 ASTM D 974 (Strong Acid) 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 3

[0337] The performance of fuel compositions of the invention 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.

[0338] The engine of the injector fouling test is the PSA DW10BTED4. In summary, the engine characteristics are: [0339] Design: Four cylinders in line, overhead camshaft, turbocharged with EGR [0340] Capacity: 1998 cm.sup.3 [0341] Combustion chamber: Four valves, bowl in piston, wall guided direct injection [0342] Power: 100 kW at 4000 rpm [0343] Torque: 320 Nm at 2000 rpm [0344] Injection system: Common rail with piezo electronically controlled 6-hole injectors. [0345] Max. pressure: 1600 bar (1.610.sup.8 Pa). Proprietary design by SIEMENS VDO [0346] Emissions control: Conforms with Euro IV limit values when combined with exhaust gas post-treatment system (DPF)

[0347] 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.

[0348] The test is run with a future injector design representative of anticipated Euro V injector technology.

[0349] 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.

[0350] Full details of the CEC F-98-08 test method can be obtained from the CEC. The coking cycle is summarised below.

[0351] 1. A warm up cycle (12 minutes) according to the following regime:

TABLE-US-00004 Duration Engine Speed Torque Step (minutes) (rpm) (Nm) 1 2 idle <5 2 3 2000 50 3 4 3500 75 4 3 4000 100

[0352] 2. 8 hrs of engine operation consisting of 8 repeats of the following cycle

TABLE-US-00005 Engine Boost Duration Speed Load Torque 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

[0353] 3. Cool down to idle in 60 seconds and idle for 10 seconds

[0354] 4. 4 hrs soak period

[0355] 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 4

[0356] A diesel fuel composition comprising additive A1 (50 ppm active) was tested according to the CECF-98-08 test method described in example 3, modified to measure clean up performance as outlined below.

[0357] 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 due to fouling of the injectors.

[0358] 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.

[0359] FIG. 1 shows the power output of the engine when running the fuel composition comprising additive A1 over the test period.

EXAMPLE 5

[0360] The ability of additives of the invention to remove Internal Diesel Injector Deposits (IDIDs) may be measured according to he test method CEC F-110-16, available from the Co-ordinating European Council. The test uses the PSA DW10C engine.

[0361] The engine characteristics as follows:

TABLE-US-00006 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.

[0362] 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).

[0363] The test procedure consists of main run cycles followed by soak periods, before cold starts are carried out.

[0364] The main running cycle consist of two speed and load set points, repeated for 6 hrs, as seen below.

TABLE-US-00007 Step Speed (rpm) Torque (N.m) Duration (s) 1 3750 250 1470 1-Ramp .fwdarw.2 30 2 1000 10 270 2-Ramp .fwdarw.1 30

[0365] The ramp times of 30 seconds are included in the duration of each step.

[0366] During the main run, parameters including, Throttle pedal position, ECU fault codes, Injector balance coefficient and Engine stalls are observed and recorded.

[0367] The engine is then left to soak at ambient temperature for 8 hrs.

[0368] 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.

[0369] If the engine starts the engine is allowed to idle 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.

[0370] An example below of all exhaust temperatures with <30 C. deviation, indicating no sticking caused by IDID.

[0371] The complete test comprises of 6 Cold Starts, although the Zero hour Cold Start does not form part of the Merit Rating and 56 hr Main run cycles, giving a total of 30 hrs engine running time.

[0372] The recorded data is inputted into the Merit Rating Chart. This allows a Rating to be produced for the test.

[0373] Maximum rating of 10 shows no issues with the running or operability of the engine for the duration of the test.

[0374] An example below:

TABLE-US-00008 TABLE 4 Cold start Starting Exhaust temperature consistency Number of Exhaust Attempts Temperature (1 = Max Cyl. Cold Start Maximum first Maximum Deviation Start Y/N Merits start) Deduction Merits Merits ( C.) Deduction Merits #0 not rated #1 Y 5 1 0 5 5 21.8 0 5 #2 Y 5 1 0 5 5 18.1 0 5 #3 Y 5 1 0 5 5 15.5 0 5 #4 Y 5 1 0 5 5 20.2 0 5 #5 Y 5 1 0 5 5 22.6 0 5 Total 25 25 merits Main run Operability Max Pedal Max Number Position Inject. of ECU at 1000 Balancing Main Maximum Fault Stall rpm/10 Coeff. run Merits resets Deduction (Y/N) Deduction N.Math.m (%) Deduction (rpm) Deduction Merits #1 5 0 0 N 0 15.4 0 15 0 5 #2 5 0 0 N 0 13.5 0 15 0 5 #3 5 0 0 N 0 13.6 0 16 0 5 #4 5 0 0 N 0 13.8 0 15 0 5 #5 5 0 0 N 0 14.5 0 15 0 5 25 Global Rating - Summary (Merit/10) 10

EXAMPLE 6

[0375] The ability of additives of the invention to clean up IDIDs was assessed according to a modification of the DW10C test described in example 6.

[0376] 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.

[0377] 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.

[0378] 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.

[0379] A diesel fuel composition comprising additive A1 (50 ppm active) was tested according to the test method outlined above. A final De-Merit rating of 8.9 was achieved. The full results are provided in table 4.

TABLE-US-00009 TABLE 4 Cold start Starting Exhaust temperature consistency Number of Exhaust Attempts Temperature (1 = Max Cyl. Cold Start Maximum first Maximum Deviation Start Y/N Merits start) Deduction Merits Merits ( C.) Deduction Merits #0 not rated #1 Y 5 1 0 5 5 19.4 0 5 #2 Y 5 1 0 5 5 151.2 5 0 #3 Y 5 1 0 5 5 29.6 0 5 #4 Y 5 1 0 5 5 28.0 0 5 #5 Y 5 1 0 5 5 31.2 3 2 Total 25 17 merits Main run Operability Max Pedal Max Number Position Inject. of ECU at 1000 Balancing Main Maximum Fault Stall rpm/10 Coeff. run Merits resets Deduction (Y/N) Deduction N.Math.m (%) Deduction (rpm) Deduction Merits #1 5 0 0 N 0 16.7 0 9.4 0 5 #2 5 0 0 N 0 15.6 0 9.4 0 5 #3 5 0 0 N 0 19.0 0 9.3 0 5 #4 5 0 0 N 0 19.0 0 9.0 0 5 #5 5 0 0 N 0 18.8 0 9.0 0 5 25 Global Rating - Summary (Merit/10) 8.933333

[0380] EXAMPLE 7

[0381] 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.

[0382] 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.

[0383] 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.

[0384] 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-00010 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

[0385] 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.