Diesel fuel compositions

Abstract

A diesel fuel composition made up of a major amount of a diesel fuel, a minor amount of at least one metallic species and a minor amount of a detergent additive is disclosed. The detergent additive includes a compound of formula:

Description

EXAMPLE 1

A mixture of monomers was used containing the following species:

The mono-ethoxylated species (2-(2-naphtholoxy)-ethanol) comprised around 60% of the mixture with the remainder being made up of the di- and tri-ethoxylated species. Oligomerisation of the monomer mixture with para-formaldehyde was carried out in toluene in the presence of an oil soluble acid catalyst. After removal of the solvent, the oligomer was reacted with iso-octadecylsuccinic anhydride to produce the following species:

where Q-iso-octadecyl,

EXAMPLE 2

Example 1 was repeated except that polyisobutylene succinic anhydride (molecular weight of PIB ˜450) was used in place of iso-octadecyl succinic anhydride. Also, around half of the residual acid functionality of the oligomer was converted to lactone functionality by extending the reaction time.

EXAMPLE 3

Example 2 was repeated except that the majority of the residual acid functionality of the oligomer was converted to lactone functionality by extending the reaction time.

EXAMPLE 4

The following reaction scheme was employed. This example used a single monomer species containing a methyl branch in the ethoxy group (as shown below). After oligomerisation, the material was post-reacted with the same polyisobutylene succinic anhydride used in Example 2. Also, common with Example 2, half of the residual acid functionality was converted to lactone functionality.

Test Protocol

The protocol used is described by Graupner et al. “Injector deposit test for modern diesel engines”, Technische Akademnie Esslingen, 5th International Colloquium, 12- 3 Jan 2005, 3.10, p157, Edited by Wifried J Bartz. Briefly, the protocol aims to replicate the operating conditions in a modern diesel engine with an emphasis on the fuel injector tip. The test is split into five stages:

• • a) an iso-speed measurement of engine power output
  • b) an 8 hour endurance run
  • c) an extended soaking period (3 to 8 hours) during which the engine is stopped and allowed to cool
  • d) a second 8 hour endurance run
  • e) an iso-speed measurement of engine power output.

Results are reported as the difference between the average torque at the start of the test during stage a) and the average torque at the end of the test during stage e). Alternatively, the measured difference between starting torque at full load/full speed and final load/speed can be used. Differences in smoke production are also noted. The formation of injector deposits will have a negative influence on the final power output and will increase the amount of smoke observed. The injectors used had the physical characteristics (i)-(v) described above.

To replicate the conditions expected in a modern diesel engine, a small amount of metal contamination in the form of zinc neodecanoate was added to the fuel used to run the engine.

The fuel used was a low-sulphur content diesel fuel with the characteristics shown in Table 1 below.

	TABLE 1
	Test description	Value	Units
	sulphur content	0.0005	mass %
	cetane number	55.4	—
	density @ 15° C.	844.9	kgm−3
	distillation characteristics
	D5%	204.8	° C.
	D10%	211.6	° C.
	D20%	222.2	° C.
	D30%	232.2	° C.
	D40%	242.1	° C.
	D50%	252.3	° C.
	D60%	262.8	° C.
	D70%	275.1	° C.
	D80%	290.5	° C.
	D90%	315.1	° C.
	D95%	337.1	° C.
	FBP	353.6	° C.
	IBP	179.7	° C.
	kinematic viscosity @ 20° C.	3.935	cSt
	kinematic viscosity @ 40° C. - D445
	cloud point	−14.0	° C.
	CFPP	−33.0	° C.

The detergent species were tested using the protocol described above. Results are given in Table 2 below. 3 ppm of Zn in the form of zinc neodecanoate was added to the fuel for all tests (except for the untreated fuel alone).

	TABLE 2
		Treat rate wppm
	Species	(active ingredient)	Torque loss
	Untreated fuel	—	4.3%
	Untreated fuel + 3 ppm Zn	—	17.2%
	PIBSA-PAM	60	13.7%
	Example 1	60	6.6%
	Example 2	60	8.2%
	Example 3	60	12.1%
	Example 4	60	7.9%

The results show that the addition of zinc to the untreated fuel gives rise to a large increase in torque loss. The commercial PIBSA-PAM detergent gave a marginal improvement. All Example species provided a greater improvement than the commercial detergent. Particularly good performance was obtained for the species of Examples 1, 2 and 4.

For comparative purposes, the species of the invention were tested in the industry standard XUD9 detergency test. A commercial PIBSA-PAM detergent was tested also. The results are given in Table 3 below.

	TABLE 3
		Treat rate wppm	Needle lift in
	Species	(active ingredient)	XUD9
	Untreated fuel	—	92
	PIBSA-PAM	60	64
	Example 3	60	91

These results show that the commercial PIBSA-PAM detergent gave the expected excellent performance in the XUD9 test. Contrastingly, the species of the invention gave no improvement over the untreated fuel.

Claims

1. A diesel fuel composition comprising a major amount of a diesel fuel, a minor amount of at least one metallic species and a minor amount of a detergent additive; wherein the detergent additive comprises at least one compound of formula (I) and&or formula (II);

2. A diesel fuel composition according to claim 1 wherein said compound is a compound of formula (II) wherein Y′ is Z(O(CR22)2)y′O—, Z is an acyl group and y′ is 1 to 6.

3. A diesel fuel composition according to claim 1 wherein Ar′is naphthalene, Y′is ZOCHCH2O—, Z is an acyl group and L′ is CH2.

4. A diesel fuel composition according to claim 1 wherein Ar′ is derived from 2-(2-naphthyloxy)-ethanol and m′ is 2 to 25.

5. A diesel fuel composition according to claim 1 wherein said Z is derived from either (i) a polyalkyl or polyalkenyl succinic acylating agent having Mn of from about 100 to about 5000 or (ii) from hydrocarbyl isocyanate.

6. A diesel fuel composition according to claim 1 wherein the detergent additive is present in an amount such that the fuel contains between 50 and 300 ppm by weight of a compound of formula (I) and/or a compound of formula (II), based on the weight of the fuel.

7. A diesel fuel composition according to claim 1 wherein said compound is a compound of Formula (III):

8. A diesel fuel composition according to claim 7, wherein said compound is a compound of Formula (III) wherein from 2% to 98% of the Y′ units are Z(O(CR22)2)y′O—, wherein Z is an acyl group and y′ is 1 to 6, and from 98% to 2% of Y′ units are —OR2″.

9. A diesel fuel composition according to claim 8, wherein said compound is a compound of Formula (III) wherein Ar′ is naphthalene; from 2% to 98% of Y′ units are ZOCH2CH2O—, from 98% to 2% of Y′ units are —OCH3; and L′ is CH2.

10. A diesel fuel composition according to claim 9, wherein said compound is a compound of Formula (III) wherein Ar′ is naphthalene; from 40% to 60% of Y′ units are ZOCH2CH2O—, and from 60% to 40% of Y′ units are —OCH3; m′ is from 2 to 25; p is from 1 to 10; andsis from 1 to 10.

11. A method of substantially removing, or reducing the occurrence of, injector deposits in a diesel engine operated using a diesel fuel containing a minor amount of a metal-containing species, the method comprising adding to the diesel fuel a detergent additive comprising a compound of formula (I) and/or a compound of formula (II) as defined in claim 1, wherein the diesel engine is equipped with fuel injectors having a plurality of spray-holes, each spray-hole having an inlet and an outlet and wherein the fuel injectors have one or more of the following characteristics: (i) spray-holes which are tapered such that the inlet diameter of the spray-holes is greater than the outlet diameter;(ii) spray-holes having an outlet diameter of 0.10 mm or less;(iii) spray-holes where an inner edge of the inlet is rounded;(iv) 6 or more spray-holes;(v) an operating tip temperature in excess of 250° C.

12. The method of claim 11 wherein the fuel injectors have two or more of characteristics (i) to (v).