Fuel and related compositions – Liquid fuels – Containing organic -c
Patent
1997-11-24
1999-03-16
Johnson, Jerry D.
Fuel and related compositions
Liquid fuels
Containing organic -c
44389, C10L 118
Patent
active
058823646
DESCRIPTION:
BRIEF SUMMARY
This application is a Rule 371 of PCT/EP96/03105 file 11 Jul. 1996.
This invention relates to additives for improving the lubricity of fuel oils such as diesel fuel oil. Diesel fuel oil compositions including the additives exhibit improved lubricity and reduced engine wear.
Concern for the environment has resulted in moves to significantly reduce the noxious components in emissions when fuel oils are burnt, particularly in engines such as diesel engines. Attempts are being made, for example, to minimise sulphur dioxide emissions. As a consequence attempts are being made to minimise the sulphur content of fuel oils. For example, although typical diesel fuel oils have in the past contained 1% by weight or more of sulphur (expressed as elemental sulphur) it is now considered desirable to reduce the level, preferably to 0.05% by weight and, advantageously, to less than 0.01% by weight, particularly less than 0.001% by weight.
Additional refining of fuel oils, necessary to achieve these low sulphur levels, often results in reductions in the level of polar components. In addition, refinery processes can reduce the level of polynuclear aromatic compounds present in such fuel oils.
Reducing the level of one or more of the sulphur, polynuclear aromatic or polar components of diesel fuel oil can reduce the ability of the oil to lubricate the injection system of the engine so that, for example, the fuel injection pump of the engine fails relatively early in the life of an engine. Failure may occur in fuel injection systems such as high pressure rotary distributors, in-line pumps and injectors. The problem of poor lubricity in diesel fuel oils is likely to be exacerbated by the future engine developments aimed at further reducing emissions, which will have more exacting lubricity requirements than present engines. For example, the advent of high pressure unit injectors is anticipated to increase the fuel oil lubricity requirement.
Similarly, poor lubricity can lead to wear problems in other mechanical devices dependent for lubrication on the natural lubricity of fuel oil.
Lubricity additives for fuel oils have been described in the art. WO 94/17160 describes an additive which comprises an ester of a carboxylic acid and an alcohol wherein the acid has from 2 to 50 carbon atoms and the alcohol has one or more carbon atoms. Glycerol monooleate is specifically disclosed as an example. Although general mixtures are contemplated, no specific mixtures of esters are disclosed.
U.S. Pat. No. 3,273,981 discloses a lubricity additive being a mixture of A+B wherein A is a polybasic acid, or a polybasic acid ester made by reacting the acid with C.sub.1 -C.sub.5 monohydric alcohols; while B is a partial ester of a polyhydric alcohol and a fatty acid, for example glyceryl monooleate, sorbitan monooleate or pentaerythitol monooleate. The mixture finds application in jet fuels.
However, in certain circumstances such prior art esters have unexpectedly been found to promote the blocking of fuel filters, particularly the fine-mesh filters typically present in diesel vehicle fuel lines. This filter-blocking problem can result in insufficient fuel flow and impaired engine operation, and is especially apparent at low temperatures.
Furthermore, it has unexpectedly been found that fuels containing the preferred ester (Additive D) described in WO 94/17160 shows a loss of lubricity performance following a period of cold storage and filtration. The loss of performance can be apparent even in the absence of severe filter blocking problems. This loss in performance itself represents a significant problem, because under field conditions a stored fuel oil is typically subjected to temperature cycles and must still be able to impart effective lubrication to mechanical devices downstream of the fuel-line filters. In a diesel vehicle fuel system, for example, diesel fuel must first flow through a fine-grade filter before reaching the fuel injection system, including the injection pump. Decreased lubricity performance after this filtration point therefo
REFERENCES:
patent: 2527889 (1950-10-01), Moore et al.
patent: 2548347 (1951-04-01), Caron et al.
patent: 3713792 (1973-01-01), Wiley
patent: 5730029 (1998-03-01), Stoldt et al.
Exxon Chemical Patents Inc.
Johnson Jerry D.
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