USE OF ORGANIC NITRATE AND/OR PEROXIDE ADDITIVES AND METHOD BASED THEREON FOR DEPOSIT REDUCTION IN POST DIESEL-COMBUSTION SYSTEMS

Abstract

The use of a nitrate compound and/or a peroxide compound as an additive in a diesel fuel composition to reduce the impact of deposits in the post combustion system of a diesel engine when combusting said diesel fuel composition.

Claims

1. (canceled)

2. A method of reducing the impact of deposits in the post combustion system of a diesel engine, the method comprising combusting in the engine a diesel fuel composition comprising as an additive a nitrate compound and/or a peroxide compound.

3. The method according to claim 2, further comprising reducing the formation of deposits in the post combustion system of a diesel engine.

4. The method according to claim 2, wherein the additive is selected from alkyl nitrates and/or dialkyl peroxides.

5. The method according to claim 2, wherein the additive comprises a nitrate compound of formula (I): ##STR00008## wherein R.sup.1 is an optionally substituted straight chain, branched or cyclic alkyl group.

6. The method according to claim 2, wherein the additive comprises a nitrate compound of formula (I): ##STR00009## wherein R.sup.1 is an optionally substituted alkyl, aryl or aralkyl group.

7. The method according to claim 2, wherein the additive comprises a nitrate compound of formula (I): ##STR00010## wherein R.sup.1 is an unsubstituted alkyl group having 2 to 20 carbon atoms.

8. The method according to claim 2, wherein the additive comprises a compound of formula (II): ##STR00011## wherein R.sup.2 is an optionally substituted alkyl, aryl, alkaryl, aralkyl or acyl group; and R.sup.3 is hydrogen or an optionally substituted alkyl, aryl, alkaryl, aralkyl or acyl group.

9. The method according to claim 2, wherein the additive comprises a compound of formula (II): ##STR00012## wherein R.sup.2 and R.sup.3 are the same and each is an unsubstituted alkyl or acyl group having 1 to 12 carbon atoms.

10. The method according to claim 2, wherein the additive is selected from 2-ethylhexyl nitrate, a decyl nitrate and di-tert-butyl peroxide.

11. The method according to claim 7, wherein R.sup.1 is a branched decyl group having an average degree of branding of from 1 to 2.5.

12. The method according to claim 2, wherein the diesel fuel composition comprises from 50 to 2000 ppm of alkyl nitrate and/or dialkyl peroxide compounds.

13. The method according to claim 2, wherein the diesel fuel composition comprises from 50 to 350 ppm alkyl nitrate and/or dialkyl peroxide compounds.

14. The method according to claim 2, further comprising reducing deposits in the post combustion system of a diesel engine having a pressure in excess of 1350 bar.

15. The method according to claim 2, further comprising reducing the formation of deposits on the turbocharger of the post combustion system.

16. The method according to claim 2, further comprising reducing the formation of deposits on the diesel oxidation catalyst of the post combustion system.

17. The method according to claim 2, further comprising reducing the formation of deposits on the diesel particulate filter of the post combustion system.

18. The method according to claim 2, further comprising reducing the formation of deposits on the selective catalytic reduction unit of the post combustion system.

19. The method according to claim 2, further comprising reducing the formation of deposits on the ammonia oxidation catalyst of the post combustion system.

20. The method according to claim 2, further comprising reducing the formation deposits on sensors within the post combustion system.

21. The method according to claim 2, further comprising reducing the formation of deposits in one more components of the post combustion system by at least 5%.

22. The method according to claim 2, wherein the diesel fuel composition comprises one or more nitrogen containing detergents.

23. The method according to claim 22 wherein the one or more nitrogen containing detergents are selected from: (i) a quaternary ammonium salt additive; (ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol; and (iii) the reaction product of a carboxylic acid-derived acylating agent and an amine.

24. The method according to claim 2, wherein the diesel engine is an off road engine, for example a marine, rail or stationary engine.

25. The method according to claim 2, further comprising providing one or more benefits selected from: an increase in power generation; an increase in torque; an increase in fuel economy; a reduction in emissions; a reduction in combustion chamber deposits; an acceleration improvement; driveability improvements; a reduction in cold start issues; lower soot formation; mitigation of lubricant degradation and/or performance loss; a reduction in diesel exhaust fluid and consumption e.g. urea consumption; reduction in wear on all post combustion components (including but not limited to the turbo charger, oxidation catalyst, DPF, SCR CAT, sensors, and injectors within the post combustion system); increased longevity of exhaust components; and the protection of intake components downstream of the EGR, for example swirl flaps, throttles and the intake manifold (due to a reduction in the likelihood of blocking etc.).

Description

EXAMPLE 1

[0235] The ability of the claimed additives to reduce the formation of deposits on a diesel particulate filter was assessed according to the following procedure.

[0236] The test vehicle was light goods vehicle (LGV) based on a Euro 6 compliant, 2.1 litre HSDI engine. The vehicle mileage prior to the test was approximately 100,000 miles.

[0237] The following modifications were made to the vehicle:

[0238] The vehicle fuel supply was modified to facilitate switch-over between different test fuels and to enable thermal conditioning of the fuel and measurement of fuel consumption.

[0239] The vehicle air intake system was modified to provide controlled combustion air at a known pressure and temperature.

Engine Operating Conditions

[0240] After engine start, the engine is driven to the following operating conditions where it is held for the duration of the test: [0241] 43% load @ 1500 RPM [0242] Translated vehicle speed of 47.5-48.0 km/h

Dynamometer & Test Cell Equipment

[0243] The testing was carried out using a commercially available Hub Dynamometer and test cell. The vehicle controls were operated by a robot driver.

Method of Soot Deposition Measurement (DPF Loading)

[0244] The calculated quantity of soot in the DPF was extracted in real time from the vehicles Connected Area Network (CAN) using industry standard diagnostic tools.

[0245] Prior to each measured DPF loading cycle, a conditioning DPF loading cycle (approx. 3-hours duration) was carried out under identical operating conditions. The loading cycle was allowed to run until a 100% DPF load was reported by the ECU, at which point an automatic regeneration was allowed to happen. Immediately following the completion of the automatic regeneration the measured DPF loading cycle commenced. The time taken from the initiation of the measurement cycle to reaching 100% DPF load was recorded.

[0246] The purpose of the conditioning DPF loading cycle was to achieve a repeatable starting condition prior to each measured DPF loading cycle. The fuel to be tested was used to perform the conditioning cycle in each instance. The basic premise of the procedure is shown below: [0247] Engine Start [0248] Soot Load [1]-Conditioning [0249] Automatic Regeneration [0250] Soot Load [2]-Measurement [0251] Automatic Regeneration [0252] Engine Stop [0253] Change to next test fuel

[0254] The base fuel was an RF-06-03 diesel fuel (Haltermann Carless, UK) having the following specification:

TABLE-US-00001 Feature Units Results Minimum Maximum Method Density 15? C. kg/m.sup.3 836.0 833.0 837.0 ASTM D4052 Marker (Red) Pass VISUAL Cetane Number 53.9 52.0 54.0 ASTM D613 I.B.Pt. ? C. 214.3 ASTM D86 10% v/v Recovered at ? C. 232.0 ASTM D86 50% v/v Recovered at ? C. 275.5 245.0 ASTM D86 90% v/v Recovered at ? C. 330.2 ASTM D86 95% v/v Recovered at ? C. 348.0 345.0 350.0 ASTM D86 F.B.Pt. ? C. 356.2 370.0 ASTM D86 Aromatics by FIA %(V/V) 19.8 Corrected for ASTM D1319 Olefins by FIA %(V/V) 5.5 Flash Point, Pensky Closed ? C. 92.0 55.0 ASTM D93 Sulphur Content mg/kg <3.0 10.0 ASTM D5453 Viscosity at 40? C. mm2/s 3.062 2.300 3.300 ASTM D445 Cloud Point ? C. ?18 ASTM D2500 CFPP ? C. ?20 ?15 EN 116 Lubricity (WSD 1,4) at 60? C. ?m 180 400 ISO 12156-1 Carbon Residue (on 10% Dist. Res) %(m/m) <0.10 0.20 ASTM D4530 Ash %(m/m) <0.001 0.010 ASTM D482 FAME Content: None Detected Pass EN 14078 Polycyclic Aromatic Hydrocarbons %(m/m) 5.8 3.0 6.0 EN 12916 Total Aromatic Hydrocarbons %(m/m) 22.2 EN 12916 Water Content mg/kg 50 200 IP 438 Water & Sediment %(V/V) <0.010 ASTM D2709 Strong Acid Number mg 0 KOH/g 0.02 ASTM D974 Oxidation Stability mg <0.1 per 2.5 ASTM D2274 100 ml Copper Corrosion, 3 hrs 1 B ASTM D130 at 100? C. Oxygen Content %(m/m) <0.04 ELEMENTAL Elemental Analysis Carbon Content %(m/m) 86.89 ASTM D5291 ASTM D5291 Hydrogen Content %(m/m) 13.11 ASTM D5291 ASTM D5291 Carbon Weight Fraction 0.8689 CALCULATION Calculation C/H Mass Ratio 6.63 CALCULATION Calculation Atomic H/C Ratio 1.7979 CALCULATION Calculation Atomic O/C Ratio <0.0003 CALCULATION Calculation Gross Heat of Combustion MJ/kg 45.72 IP 12 IP 12 Net Heat of Combustion MJ/kg 42.94 IP 12 IP 12 Net Heat of Combustion btu/lb 18460 CALCULATION Calculation

[0255] The additives used and the test results achieved are detailed in Table 1. The results are also represented in FIG. 1.

TABLE-US-00002 TABLE 1 Time until DPF Treat rate regeneration Additive (ppm active) (hours:minutes) None 02:16 2-Ethylhexyl Nitrate (2-EHN) 700 02:48 Di-Tert Butyl Peroxide 700 02:50

[0256] This showed that the inventive additives were effective in increasing the time until DPF regeneration, therefore they were effective in reducing the formation of deposits on a diesel particulate filter.

EXAMPLE 2

[0257] The ability of the claimed additives to reduce the formation of deposits on a diesel particulate filter was assessed according to the following procedure.

[0258] A Euro 6 compliant 2.0 litre HSDI engine was connected to a test automation system and test bed fitted with an engine dynamometer. The engine was controlled by an ECU supplied by the engine manufacturer. The engine configuration did not include any further exhaust aftertreatment.

[0259] For each cycle, the engine operating conditions consisted of two different speed and load points. [0260] Stage #1 [DPF Loading] [0261] 19% load @ 1200 RPM [0262] Stage #2 [DPF Regeneration] [0263] 37% load @ 1500 RPM

[0264] The base fuel was as for Example 1.

Method of Soot Deposition Measurement (DPF Loading)

[0265] The relative quantity of soot in the DPF was determined from external measurement of the differential pressure across the DPF via the test automation system. DPF regeneration commenced when a predetermined maximum differential pressure was obtained (corresponding to 100% DPF loading).

[0266] The engine oil was changed prior to performing the base fuel DPF loading cycles. Prior to each measured DPF loading cycle, the engine conducted a conditioning DPF loading cycle (approx. 7-hours duration) under identical operating conditions.

[0267] The basic premise of the procedure is shown below: [0268] Engine Start [0269] Soot Load [1]-Conditioning [0270] Manual Regeneration [0271] Soot Load [2]-Conditioning [0272] Manual Regeneration [0273] Soot Load [3]-Measurement [0274] Manual Regeneration [0275] Engine Stop [0276] Change to next test fuel

[0277] The time taken from the initiation of the cycle to reaching the predetermined maximum differential pressure (corresponding to 100% DPF loading) was recorded for the two measurement cycles, and an average of the two results is shown in Table 2 below.

TABLE-US-00003 TABLE 2 Time until DPF Treat rate regeneration Additive (ppm active) (hours:minutes) None 06:11 C10 alkyl nitrate 700 06:53

[0278] The C10 alkyl nitrate was a commercially available alkyl nitrate derived from a branched C10 alcohol having an average of 2.0 branches per molecule.