Diesel fuel compositions and methods of use thereof

Abstract

A method of combating internal diesel injector deposits caused by carboxylate residues and/or lacquers in the injectors of a diesel engine, the method comprising combusting in the engine a diesel fuel composition comprising (a) the reaction product of a carboxylic acid-derived acylating agent and an amine and (b) a quaternary ammonium salt additive.

Claims

1. A method of combating internal diesel injector deposits caused by sodium carboxylate residues in the injectors of a diesel engine, the method comprising combusting in the engine a diesel fuel composition comprising (a) the reaction product of a carboxylic acid-derived acylating agent and an amine and (b) a quaternary ammonium salt additive; wherein the diesel engine has a fuel injection system which comprises a high pressure fuel injection (HPFI) system with fuel pressures greater than 1350 bar.

2. The method according to claim 1 wherein the acylated nitrogen-containing additive (a) comprises the reaction product of a polyisobutene-substituted succinic acid or succinic anhydride and a polyethylene polyamine.

3. The method according to claim 2 wherein the polyisobutene substituent of the polyisobutene-substituted succinic acid or succinic anhydride has a number average molecular weight of between 250 and 2300.

4. The method according to claim 2 wherein at least 90% of the succinimide molecules have a molecular weight of more than 400.

5. The method according to claim 3 wherein at least 90% of the succinimide molecules have a molecular weight of more than 400.

6. The method according to claim 1 wherein the quaternary ammonium salt additive (b) for use herein is the reaction product of a quaternising agent and a nitrogen-containing species having at least one tertiary amine group selected from: (i) the reaction product of a hydrocarbyl-substituted acylating agent and a compound comprising at least one tertiary amine group and a primary amine, secondary amine or alcohol group; (ii) a Mannich reaction product comprising a tertiary amine group; and (iii) a polyalkylene substituted amine having at least one tertiary amine group.

7. The method according to claim 6 wherein component (i) comprises one or more compounds formed by the reaction of a hydrocarbyl-substituted acylating agent and an amine of formula (I) or (II): ##STR00006## wherein R.sup.2 and R.sup.3 are the same or different alkyl groups having from 1 to 22 carbon atoms; X is an 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 C.sub.1 to C.sub.22 alkyl group.

8. The method according to claim 7 wherein X is a propylene group.

9. The method according to claim 1 wherein the quaternising agent used to prepare the quaternary ammonium salt additive (b) is selected from the group consisting of dialkyl sulphates; an ester of a carboxylic acid; alkyl halides; benzyl halides; hydrocarbyl substituted carbonates; and hydrocarbyl epoxides in combination with an acid or mixtures thereof.

10. The method according to claim 1 wherein the quaternising agent used to prepare the quaternary ammonium salt additive (b) is a compound of formula (III): ##STR00007## wherein R is an optionally substituted alkyl, alkenyl, aryl or alkylaryl group and R.sup.1 is a C.sub.1 to C.sub.22 alkyl, aryl or alkylaryl group.

11. The method according to claim 10 wherein the quaternizing agent is selected from dimethyl oxalate, methyl 2-nitrobenzoate and methyl salicylate.

12. The method according to claim 1 which provides “keep clean” performance.

13. The method according to claim 1 which provides “clean up” performance.

14. The method according to claim 1 which further combats external injector deposits including those at the injector nozzle and at the injector tip and/or fuel filter deposits.

15. The method according to claim 14 which provides “keep clean” and/or “clean up” performance in relation to external injector deposits and/or fuel filter deposits.

16. The method according to claim 3 wherein the polyisobutene substituent of the polyisobutene-substituted succinic acid or succinic anhydride has a number average molecular weight of between 450 and 1500.

Description

EXAMPLE 1—ADDITIVE Q1

(1) Additive Q1, a quaternary ammonium salt additive of the present invention was prepared as follows:

(2) A mixture of succinic anhydride prepared from 1000 Mn polyisobutylene (21425 g) and diluent oil—pilot 900 (3781 g) were heated with stirring to 110° C. under a nitrogen atmosphere. Dimethylaminopropylamine (DMAPA, 2314 g) was added slowly over 45 minutes maintaining batch temperature below 115° C. The reaction temperature was increased to 150° C. and held for a further 3 hours. The resulting compound is a DMAPA succinimide.

(3) This DMAPA succinimide was heated with styrene oxide (12.5 g), acetic acid (6.25 g) and methanol (43.4 g) under reflux (approx 80° C.) with stirring for 5 hours under a nitrogen atmosphere. The mixture was purified by distillation (30° C., −1 bar) to give the styrene oxide quaternary ammonium salt as a water white distillate.

EXAMPLE 2—ADDITIVE Q2

(4) A reactor was charged with 33.2 kg (26.5 mol) PIBSA (made from 1000 MW PIB and maleic anhydride) and heated to 90° C. DMAPA (2.71 kg, 26.5 mol) was charged and the mixture stirred for 1 hour at 90-100° C. The temperature was increased to 140° C. for 3 hours and water removed. Methyl salicylate (4.04 kg, 26.5 mol) was charged and the mixture held at 140° C. for 8 hours. Caromax 20 (26.6 kg) was added.

EXAMPLE 3—ADDITIVE Q3

(5) A reactor was charged with 8058 kg (6.69 kmol) PIBSA (made from 1000 MW PIB and maleic anhydride) and heated to 120° C. DMAPA (649 kg, 6.35 kmol) was added at 120-130° C. followed by 200 kg aromatic solvent. The mixture was held at 120-130° C. for one hour whilst removing water. The temperature was increased to 140° C. and the mixture held for a further three hours.

(6) The reaction mixture was cooled to 110° C. and dimethyl oxalate (800 kg, 6.77 kmol) added, followed by 200 kg aromatic solvent. The batch was held at 110° C. for 2-3 hours. The batch was further diluted with 5742 kg of aromatic solvent before being cooled and discharged.

EXAMPLE 4—ADDITIVE A1

(7) Additive A1 is a 60% active ingredient solution (in aromatic solvent) of a polyisobutenyl succinimide obtained from the condensation reaction of a polyisobutenyl succinic anhydride (PIBSA) derived from polyisobutene of Mn approximately 1000 with a polyethylene polyamine mixture of average composition approximating to triethylene tetramine. The product was obtained by mixing the PIBSA and polyethylene polyamine at 50° C. under nitrogen and heating at 160° C. for 5 hours with removal of water.

EXAMPLE 5—ADDITIVE A2

(8) Additive A2 is a 60% active ingredient solution (in aromatic solvent) of a polyisobutenyl succinimide obtained from the condensation reaction of a polyisobutenyl succinic anhydride derived from polyisobutene of Mn approximately 750 with a polyethylene polyamine mixture of average composition approximating to tetraethylene pentamine. The product was obtained by mixing the PIBSA and polyethylene polyamine at 50° C. under nitrogen and heating at 160° C. for 5 hours with removal of water.

EXAMPLE 6

(9) Fuel compositions were prepared by adding additives Q3 and A2 to diesel fuel.

(10) The diesel fuel complied with the RF06 base fuel, the details of which are given in table 1 below.

(11) TABLE-US-00001 TABLE 1 Limits Units Min Max Method Property 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 % 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) μm — 400 CEC F-06-A-96 Fatty Acid Methyl prohibited Ester

EXAMPLE 7

(12) Fuel compositions were tested according to the CECF-98-08 DW 10B method, modified as appropriate.

(13) The engine used in the test is the PSA DW10BTED4. In summary, the engine characteristics are:

(14) Design: Four cylinders in line, overhead camshaft, turbocharged with EGR

(15) Capacity: 1998 cm.sup.3

(16) Combustion chamber: Four valves, bowl in piston, wall guided direct injection

(17) Power: 100 kW at 4000 rpm

(18) Torque: 320 Nm at 2000 rpm

(19) Injection system: Common rail with piezo electronically controlled 6-hole injectors.

(20) Max. pressure: 1600 bar (1.6×10.sup.8 Pa). Proprietary design by SIEMENS VDO

(21) Emissions control: Conforms with Euro 4 limit values when combined with exhaust gas post-treatment system (DPF)

(22) 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.

(23) The test is run with a future injector design representative of anticipated Euro 5 injector technology.

(24) 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.

(25) Full details of the CEC F-98-08 test method can be obtained from the CEC. The coking cycle is summarised below.

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

(27) TABLE-US-00002 Duration Engine Speed Torque Step (minutes) (rpm) (Nm) 1 2 idle <5 2 3 2000 50 3 4 3500 75 4 3 4000 100
2. 8 hrs of engine operation consisting of 8 repeats of the following cycle

(28) TABLE-US-00003 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
3. Cool down to idle in 60 seconds and idle for 10 seconds
4. 4 hrs soak period

(29) 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 44 hours total test time excluding warm ups and cool downs.

EXAMPLE 8

(30) The diesel fuel compositions of table 2 below were prepared by adding additives Q3 and A2 to RF06 base fuel comprising 1 ppm zinc (as zinc neodecanoate).

(31) The compositions were tested according to the CECF-98-08 DW10B test method described in example 7, modified as outlined below.

(32) In the case of fuel compositions 1 and 2 listed in table 2, 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.

(33) 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 additives specified.

(34) FIG. 1 shows the power output of the engine when running the fuel compositions over the test period.

(35) The results are also given in table 2.

(36) TABLE-US-00004 TABLE 2 Observed Power Loss, % Treat Rate, ppm active Clean Up Clean Up Compo- Additive Additive Dirty Up Phase after Phase after sition Q3 A2 Phase 10 hr 32 hr 1 240 4.7 1.6 1.4 2 120 120 5.4 −0.3 −0.7

EXAMPLE 9

(37) The diesel fuel compositions of table 3 were prepared by dosing additives Q3 and A2 into a diesel fuel composition containing 1 ppm sodium as sodium 2-ethylhexanoate and 100 ppm of a mixture of carboxylic acids and organic solvents. The diesel fuel complied with the RF06 specification given above.

(38) The compositions were tested according to the CECF-98-08 DW10B test method of example 7, modified by the addition of thermocouples to the engine. These were positioned to enable the exhaust temperature of each cylinder to be measured. This allows injector sticking to be tested.

(39) The following results were obtained:

(40) TABLE-US-00005 Na Level, Treat Rate, ppm active ppm Additive Q3 Additive A2 Result 1 — — 3 injectors stuck after 16 hours engine operation 1 240 — 1 injector stuck after 32 hours operation 1 120 120 No injectors stuck after 32 hours engine operation