Fuel oil compositions

Details Fuel oil compositions Fuel oil compositions

1996-08-01

2000-01-04

Medley, Margaret

Fuel and related compositions

Liquid fuels

Containing organic -c

44400, 44401, C10L 118

Patent

active

060105453

DESCRIPTION:

BRIEF SUMMARY
This invention relates to fuel oils, and to the use of additives to improve the characteristics of fuel oils, more especially of diesel fuel and kerosene.
Environmental concerns have led to a need for fuels with reduced sulphur content, especially diesel fuel and kerosene. However, the refining processes that produce fuels with low sulphur contents also result in a product of lower viscosity and a lower content of other components in the fuel that contribute to its lubricity, for example, polycyclic aromatics and polar compounds. Furthermore, sulphur-containing compounds in general are regarded as providing some anti-wear properties and a result of the reduction in their proportions, together with the reduction in proportions of other components providing lubricity, has been an increase in the number of reported problems in fuel pumps in diesel engines. The problems are caused by wear in, for example, cam plates, rollers, spindles and drive shafts, and include sudden pump failures relatively early in the life of the engine.
The problems may be expected to become worse in future because, in order to meet stricter requirements on exhaust emissions generally, higher pressure fuel systems, including in-line, rotary pumps and unit injector systems, are being introduced, these being expected to have more stringent lubricity requirements than present equipment, at the same time as lower sulphur levels in fuels become more widely required.
Historically, the typical sulphur content in a diesel fuel was below 0.5% by weight. In Europe maximum sulphur levels are being reduced to 0.20%, and are expected to be reduced to 0.05% in 1996; in Sweden grades of fuel with levels below 0.005% (Class 2) and 0.001% (Class 1) have already been introduced. A fuel oil composition with a sulphur level below 0.20% by weight is referred to herein as a low-sulphur fuel.
Such low-sulphur fuels may contain an additive to enhance their lubricity. These additives are of several types. In WO 94/17160, there is disclosed a low sulphur fuel comprising a carboxylic acid ester to enhance lubricity, more especially an ester in which the acid moiety contains from 2 to 50 carbon atoms and the alcohol moiety contains one or more carbon atoms. In U.S. Pat. No. 3,273,981, a mixture of a dimer acid, for example, the dimer of linoleic acid, and a partially esterified polyhydric alcohol is described for the same purpose. In U.S. Pat. No. 3,287,273, the use of an optionally hydrogenated dimer acid glycol ester is described. Other materials used as lubricity enhancers, or anti-wear agents as they are also termed, include a sulphurized dioleyl norbornene ester (EP-A-99595), castor oil (U.S. Pat. No. 4,375,360 and EP-A-605857) and, in methanol-containing fuels, a variety of alcohols and acids having from 6 to 30 carbon atoms, acid and alcohol ethoxylates, mono- and di-esters, polyol esters, and olefin-carboxylic acid copolymers and vinyl alcohol polymers (also U.S. Pat. No. 4,375,360). GB-A-650118 describes solubilizing partial esters by amine salts. The disclosures of the above identified documents are incorporated by reference herein.
The present invention is based on the observation that the presence of at least one polyoxyalkylene compound further enhances the lubricity of a low-sulphur fuel oil containing a lubricity enhancer. The combination of conventional lubricity enhancer and at least one such copolymer can provide excellent lubricity enhancement, allowing a higher level of lubricity to be obtained for a fixed amount of conventional lubricity enhancer. Alternatively, an equivalent level of lubricity can be provided whilst allowing a lower amount of the conventional lubricity enhancer to be used.
According to the first aspect of the invention, there is provided a composition comprising a major proportion of a fuel oil and minor proportions of a lubricity enhancer and at least one polyoxyalkylene compound, the sulphur content of the composition being at most 0.2% by weight.
Advantageously, the sulphur content of the composition is at most 0.05% by w

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