EP1088880A1

EP1088880A1 - Fuel composition

Info

Publication number: EP1088880A1
Application number: EP99117853A
Authority: EP
Inventors: Dirk Packet
Original assignee: Fina Research SA
Current assignee: TotalEnergies Onetech Belgium SA
Priority date: 1999-09-10
Filing date: 1999-09-10
Publication date: 2001-04-04
Also published as: ATE237665T1; WO2001019941A1; DE60002224T2; EP1216288A1; EP1216288B1; AU7286400A; KR20020051918A; DE60002224D1; JP2003509569A

Abstract

Use of a composition comprising an ester of a monocarboxylic acid and a polyhydric alcohol as a diesel fuel oil lubricity improver, wherein the monocarboxylic acid comprises a C₈-C₂₄ linear or branched chain, saturated or unsaturated acid or a mixture thereof, and the polyhydric alcohol comprises an alcohol of the general formula:

CR¹R²R³R⁴, or a dimer, trimer or tetramer of the alcohol which is obtainable by condensation thereof, wherein

R¹, R² and R³ are each independently a C₁-C₁₂ linear or branched chain alkylol and R⁴ is a linear or branched chain C₁-C₁₂ alkyl or a linear or branched chain C₁-C₁₂ alkylol.

Description

The present invention relates to a fuel oil composition comprising a diesel fuel oil and a fuel oil lubricity improver. The invention further relates to the use of a composition as a diesel fuel oil lubricity improver.
Various ester additives are known for addition to hydrocarbon compositions for various purposes. For example, US 2993773 describes esters of alkenyl succinnic acid with a large variety of different alcohols. These esters are used to inhibit or prevent deposit-forming in hydrocarbon fuels. GB 1065398 describes how the lubricity of aviation turbojet fuels might be improved using partial esters of a number of different polyhydric alcohols, especially an ester of a C36 dimer acid and sorbitan monooleate. GB 1047493 is concerned with the addition of a lubricity additive to a lubricating oil in which the lubricity additive is a partial or mono ester of a dicarboxylic acid and an oil insoluble glycol such as the monoester of the C36 linoleic dimer acid and glycol.
Diesel fuel oils generally comprise petroleum middle distillate fuel oils which boil within the range of about 100°C to about 400°C. There has recently been a drive to reduce the sulphur content of such diesel fuels so as to reduce sulphur dioxide emissions for environmental reasons. As of October 1996, the EU imposed a maximum sulphur content for diesel fuel oil of 0.05% by weight. As a result of this, a problem has arisen in that preparation of low sulphur content fuel oils also reduces the content in the fuels of other components such as polyaromatics. The problem is that the lubricity of the fuel is reduced and this can lead to engine failure. In order to overcome this problem, it has been proposed in WO 94/17160 to provide diesel fuel oil compositions with a lubricity improver additive. Particular examples of such an additive disclosed in WO 94/17160 are glycerol monooleate esters and di-isodecyl adipate esters. Glycerol monooleate esters are in commercial use as diesel fuel oil additives to enhance the lubricity of the diesel fuel oils. EP-A-0773278 also addresses this problem, providing as a lubricity improver additive a hydroxy-substituted carboxylic acid or acid derivative such as ricinoleic acid or glycerol monoricinoleate.
The present invention is concerned with a new problem which arises with diesel fuel oil lubricity improvers such as glycerol monooleate. When lubricity improvers of this type are sold, manufacturers recommend that the product be stored above 10°C. This is necessary because, at lower temperatures, the known diesel fuel oil lubricity improvers become unstable with a tendency to cloud or even freeze. The requirement to store at above 10°C to prevent these drawbacks is inconvenient and costly for customers who have to provide specialised storage facilities.
The present invention aims to overcome the drawbacks of the prior art.
In a first aspect, the present invention provides use of a composition comprising an ester of a monocarboxylic acid and a polyhydric alcohol as a diesel fuel oil lubricity improver, wherein the monocarboxylic acid comprises a C₈-C₂₄ linear or branched chain, saturated or unsaturated acid or a mixture thereof, and the polyhydric alcohol comprises an alcohol of the general formula: CR¹R²R³R⁴, or a dimer, trimer or tetramer of the alcohol which is obtainable by condensation thereof, wherein
R¹, R² and R³ are each independently a C₁-C₁₂ linear or branched chain alkylol and R⁴ is a linear or branched chain C₁-C₁₂ alkyl or a linear or branched chain C₁-C₁₂ alkylol.
In a second aspect, the present invention provides a fuel oil composition comprising a diesel fuel oil having a sulphur content of no more than 0.05% by weight and a fuel oil lubricity improver comprising an ester of a monocarboxylic acid and a polyhydric alcohol as a diesel fuel oil lubricity improver, wherein the monocarboxylic acid comprises a C₈-C₂₄ linear or branched chain, saturated or unsaturated acid or a mixture thereof, and the polyhydric alcohol comprises an alcohol of the general formula: CR¹R²R³R⁴, or a dimer, trimer or tetramer of the alcohol which is obtainable by condensation thereof wherein
R¹, R² and R³ are each independently a C₁-C₁₂ linear or branched chain alkylol and R⁴ is a linear or branched chain C₁-C₁₂ alkyl or a linear or branched chain C₁-C₁₂ alkylol.
It is surprisingly found that, using the esters of the present invention as a diesel fuel oil lubricity improver enables the product to be storable as a liquid at a temperature below 20°C, even at a temperature below -10°C. In addition to these cold stability properties, the esters of the present invention possess ability comparable to the products currently on the market to improve the lubricity of diesel fuel oils. Accordingly, the need to use specialist storage facilities for the lubricity improvers is obviated.
The ester of the present invention preferably comprises a diester, which may be part of a mixture comprising a monoester and a diester, and optionally including higher esters such as a triester and a tetraester. R¹, R² and R³ are preferably each independently a C₁-C₄ linear or branched chain alkylol, more preferably CH₂OH. R⁴ is preferably a C₁-C₄ linear or branched chain alkyl or alkylol, such as CH₃, CH₂OH or CH₂CH₃. More preferably R⁴ is an alkylol so as to increase the number of free -OH groups in the ester. A particularly preferred alcohol component of the ester is pentaerythritol, although other alcohols such as trimethylolpropane (TMP) and trimethylolethane (TME)may be used. It is preferred that the ester has at least two free -OH groups.
The carboxylic acid component of the ester may be a linear or branched chain carboxylic acid which may be saturated or unsaturated and is preferably a C₁₂-C₂₂ monocarboxylic acid. Typically, the carboxylic acid has an iodine value of 40 to 180, preferably an iodine value above 60, more preferably above 70, as measured in accordance with the AOCS (American Oil Chemists Society) Official Method cd-1-25. It is preferred to use an unsaturated carboxylic acid, particularly as these are readily available and are often naturally-occurring. Particularly useful unsaturated carboxylic acids include oleic acid, linoleic acid, linolenic acid, palmoleic acid, gadoleic acid, erucic acid and other unsaturated acids with 22 carbon atoms, and mixtures thereof. The unsaturated carboxylic acid component may be selected from tall oil fatty acids, soybean fatty acids, rape seed fatty acids, sunflower seed fatty acids, fish oil and fatty acids, and cold fractionated tallow and palm oil fatty acids. The monocarboxylic acid may be substituted, for example, by at least one hydroxyl group. A suitable substituted monocarboxylic acid is ricinoleic acid.
In contrast with monoglycerides, the esters of the present invention such as the pentaerythritol esters, have a cold stability which is independent of the molar ratio of fatty acid to alcohol. Thus, lubricity efficiency increases with a decrease in ratio of fatty acid to alcohol in both pentaerythritol and monoglycerides; in the monoglycerides the cold stability decreases whereas in the pentaerythritol esters it does not.
Typically, in accordance with the present invention, the amount of fuel oil lubricity improver used in the fuel oil is in the range 1 to 1000ppm, preferably in the range 10 to 500ppm, most preferably in the range 10 to 200ppm.
The ester of the present invention may be used as the diesel fuel oil lubricity improver in pure form or in mixture with other components such as the conventional diesel fuel oil lubricity improvers, such as glycerol monooleate. Typically, the amount of ester of the present invention in such a mixture is in the range 60 to 100%wt, preferably in the range 80 to 100%wt, most preferably in the range 90 to 95%wt, especialy around 92%. The properties of these mixtures are also improved over known lubricity improvers.
The present invention will now be described in further detail, by way of example only, with reference to the following Examples.

Example 1

Lubricity Performance

All tests were done with the unadditized reference diesel fuel RF73-T-93, with a sulphur content of 0.05%.
The fuel oil incorporated an amount of lubricity improver as set out in Table 1 below so as to compare the effectiveness of lubricity improvers according to the present invention with those of the prior art. A High Frequency Reciprocating Rig (HFRR) test was carried out as described in D. Wei and H. Spikes, Wear, Vol. 111, No. 2, p. 217, 1986; and R. Caprotti, C. Bovington, W. Fowler and M. Taylor SAE paper 922183; SAE fuels and lubes. Meeting Oct. 1992; San Francisco, USA. The present applicants are aiming for a wear scar diameter of less than 400 microns at a dosage level of 100ppm.

wear scar diameter in micron for additized RF73-T-93

Dosage level Glycerolmonooleate (comparative) A B

0 ppm 552 552 552

100 ppm 305 328 381

200 ppm 315 328 n.a.
Lubricity improver A is a mixture of pentaerytritolmonooleate, pentaerytritoldioleate and pentaerytritoltrioleate including 39% diester. The olein fraction used for the synthesis of this pentaerytritol ester and for the glycerolmonooleate was obtained by a cold fractionation of tallow fatty acids and has cloud point between 0°C and 6°C. Lubricity improver B is a mixture of 92% of A and 8% of the glycerolmonooleate.

Example 2

Cold Stability

The cold stability of both esters of example 1 was compared by measuring the cloud point accoding to ASTM method D5950 and the pour point according to ASTM method D5771. The results are presented in Table 2.

cloud point and pour pont of glycerolmonooleate and lubricity improvers A and B
	Glycerolmonooleate (comparative)	A	B
Cloud point (°C)	10°C	-15°C	-14°C
Pour point (°C)	3°C	-27°C	-30°C

The results show that both cloud point and pour point values are significantly lower in the pentaerythritol esters than in the prior art glycerolmonooleate.

Example 3

Lubricity performance

As example 1, but the monoglyceride and the lubricity improver A were synthesized with tall oil fatty acids. Tall oil fatty acids as such are also included as comparative example.

Dosage level monoglyceride of tall oil fatty acids (comparative) Tall oil fatty acids A

0 ppm 552 552 552

50 ppm 507 n.a. 493

100 ppm 336 339 318

200 ppm n.a. n.a. 310

Example 4

Cold stability

The pour point of the different compounds mentioned in example 3 are compared.

monoglyceride of tall oil fatty acids (comparative) Tall oil fatty acids A

pour point (°C) -27 -12 -51
Taken together, these results confirm that the esters of the present invention have good lubricity improvement properties for diesel fuel oils and superior cold storage properties as compared with the lubricity improvers of the prior art.

Claims

Use of a composition comprising an ester of a monocarboxylic acid and a polyhydric alcohol as a diesel fuel oil lubricity improver, wherein the monocarboxylic acid comprises a C₈-C₂₄ linear or branched chain, saturated or unsaturated acid or a mixture thereof, and the polyhydric alcohol comprises an alcohol of the general formula: CR¹R²R³R⁴, or a dimer, trimer or tetramer of the alcohol which is obtainable by condensation thereof, wherein
R¹, R² and R³ are each independently a C₁-C₁₂ linear or branched chain alkylol and R⁴ is a linear or branched chain C₁-C₁₂ alkyl or a linear or branched chain C₁-C₁₂ alkylol.
Use according to claim 1, wherein the ester comprises a diester.
Use according to claim 1 or claim 2, wherein the ester comprises a mixture comprising a monoester and a diester.
Use acording to any one of claims 1 to 3, wherein R¹, R² and R³ are each independently a C₁-C₄ linear or branched chain alkylol.
Use according to claim 4, wherein R¹ and R² and R³ are each CH₂OH.
Use according to any one of the preceding claims, wherein R⁴ is a C₁-C₄ linear or branched chain alkyl or alkylol.
Use according to any one of the preceding claims, wherein R⁴ is CH₃, CH₂OH or CH₂CH₃.
Use according to any one of the preceding claims, wherein R⁴ is an alkylol.
Use according to any one of the preceding claims, wherein the alcohol comprises pentaerythritol.
Use according to any one of the preceding claims, wherein the ester has at least two free -OH groups.
Use according to any one of the preceding claims, wherein the monocarboxylic acid is substituted with at least one hydroxyl group.
Use according to any one of the preceding claims, wherein the monocarboxylic acid is a C₁₂-C₂₂ monocarboxylic acid.
Use according to any one of the preceding claims, wherein the carboxylic acid has an iodine value of 40-180, as measured in accordance with AOCS Official Method Cd-1-25.
Use according to claim 13, wherein the carboxylic acid comprises an unsaturated carboxylic acid.
Use according to claim 14, wherein the unsaturated carboxylic acid comprises a natural fatty acid.
Use according to claim 14, wherein the unsaturated carboxylic acid comprises oleic acid, linoleic acid, linolenic acid, palmiloleic, arachidic or mixtures thereof.
A fuel oil composition comprising a diesel fuel oil having a sulphur content of no more than 0.05% by weight and a fuel oil lubricity improver comprising an ester of a monocarboxylic acid and a polyhydric alcohol as a diesel fuel oil lubricity improver, wherein the monocarboxylic acid comprises a C₈-C₂₄ linear or branched chain, saturated or unsaturated acid or a mixture thereof, and the polyhydric alcohol comprises an alcohol of the general formula: CR1R2R3R4, or a dimer, trimer or tetramer of the alcohol which is obtainable by condensation thereof wherein
R¹, R² and R³ are each independently a C₁-C₁₂ linear or branched chain alkylol and R⁴ is a linear or branched chain C₁-C₁₂ alkyl or a linear or branched chain C₁-C₁₂ alkylol.
A fuel oil composition according to claim 17, wherein the ester is as defined in any one of claims 2 to 16.
A fuel oil composition according to claim 18, wherein the amount of the fuel oil lubricity improver in the fuel oil is in the range 10 to 500 ppm.