Diesel Fuel Compositions Having Anti-Wear Properties

It has recently been disclosed in Brazilian Patent Application No. PI7700392 that alcohols, such as methanol and ethanol, can be substituted for conventional petroleum derived diesel fuels for burning in diesel engines, when used in combination with an ignition accelerator, such as ethyl nitrate or nitrite. Reportedly, the addition of alkyl nitrate or nitrite accelerators to the alcohol achieves a level of auto-ignition sufficient to operate in diesel engines. Unfortunately, these fuel compositions, devoid of any petroleum derived products, are notably deficient in lubricity or lubricating properties with the result that engine wear from the use of these fuels in internal combustion reciprocating diesel engines is a serious problem. Of particular concern are wear problems associated with the fuel injector mechanisms used in such engines. Wear problems have also been encountered in diesel engines operating on light diesel fuel oils as disclosed in U.S. Pat. No. 4,002,437.

Fatty acid dimers and the amine salts thereof have been used in hydrocarbon fluid compositions for many years. Their principle function appears to have been as hydrocarbon fluid rust or corrosion inhibitors. Typical background patents showing such use are U.S. Pat. No. 3,696,048, U.S. Pat. No. 2,822,330, U.S. Pat. No. 2,631,979, U.S. Pat. No. 2,632,695, and U.S. Pat. No. 3,017,354.

It has now been found that the addition of certain dimerized unsaturated fatty acids to compression ignition fuels adapted for use in diesel engines which comprise (1) a monohydroxy alkanol having from 1 to 5 carbon atoms and (2) an ignition accelerator can significantly improve the wear characteristics of said fuels.

A preferred embodiment of the present invention is an anti-wear compression ignition fuel for use in diesel engines comprising (1) a monohydroxy alkanol having from 1 to 5 carbon atoms, (2) an ignition accelerator, and (3) a wear inhibiting amount of a dimerized unsaturated fatty acid.

A further embodiment of the present invention is a method for inhibiting engine wear in an internal combustion reciprocating diesel engine operating on a compression ignition fuel comprising (1) a monohydroxy alkanol having from 1 to 5 carbon atoms, (2) an ignition accelerator, and (3) a wear inhibiting amount of a dimerized unsaturated fatty acid, said method comprising (a) supplying to the fuel induction system of said engine said compression ignition fuel, (b) inducting air into the combustion chambers of said engine, (c) compressing said air, (d) injecting said compression ignition fuel into said combustion chambers containing said compressed air, (e) igniting said compressed mixture, and (f) exhausting the resultant combustion products resulting in reduced engine wear in said engine.

A still further embodiment of the present invention is a method for preparing a compression ignition fuel adapted for use in diesel engines having anti-wear properties which comprises blending (1) a wear inhibiting amount of a dimerized unsaturated fatty acid with (2) a monohydroxy alkanol having from 1 to 5 carbon atoms, and (3) an ignition accelerator.

Monohydroxy alcohols which can be used in the present invention include those containing from 1 to 5 carbon atoms. Preferred alcohols are saturated aliphatic monohydric alcohols having from 1 to 5 carbon atoms. Methanol, ethanol, propanol, n-butanol, isobutanol, amyl alcohol and isoamyl alcohol are preferred alcohols for use in the present invention. Of these, ethanol is the most preferred.

The dimerized unsaturated fatty acid component of the fuel composition of the present invention is preferably a dimer of a comparatively long chain fatty acid, e.g. containing from 8 to 30 carbon atoms, and may be pure, or substantially pure, dimer. Alternatively, and preferably, the material sold commercially and known as "dimer acid" may be used. This latter material is prepared by dimerizing unsaturated fatty acid and consists of a mixture of monomer, dimer and trimer of the acid. A particularly preferred dimer acid is the dimer of linoleic acid.

The ignition accelerator component of the anti-wear compression ignition fuel composition of the present invention is an organic nitrate. Preferred organic nitrates are substituted or unsubstituted alkyl or cycloalkyl nitrates having up to about 10 carbon atoms, preferably from 2 to 10 carbon atoms. The alkyl group may be either linear or branched. Specific examples of nitrate compounds suitable for use in the present invention include, but are not limited to the following:

methyl nitrate

ethyl nitrate

n-propyl nitrate

isopropyl nitrate

allyl nitrate

n-butyl nitrate

isobutyl nitrate

sec-butyl nitrate

tert-butyl nitrate

n-amyl nitrate

isoamyl nitrate

2-amyl nitrate

3-amyl nitrate

tert-amyl nitrate

n-hexyl nitrate

2-ethylhexyl nitrate

n-heptyl nitrate

sec-heptyl nitrate

n-octyl nitrate

sec-octyl nitrate

n-nonyl nitrate

n-decyl nitrate

n-dodecyl nitrate

cyclopentylnitrate

cyclohexylnitrate

methylcyclohexyl nitrate

isopropylcyclohexyl nitrate

and the esters of alkoxy substituted aliphatic alcohols, such as 1-methoxypropyl-2-nitrate, 1-ethoxypropyl-2-nitrate, 1-isopropoxy-butyl nitrate, 1-ethoxybutyl nitrate and the like. Preferred alkyl nitrates are ethyl nitrate, propyl nitrate, amyl nitrates and hexyl nitrates. Other preferred alkyl nitrates are mixtures of primary amyl nitrates or primary hexyl nitrates. By primary is meant that the nitrate functional group is attached to a carbon atom which is attached to two hydrogen atoms. Examples of primary hexyl nitrates would be n-hexyl nitrate, 2 ethylhexyl nitrate, 4-methyl-n-pentyl nitrate and the like. Preparation of the nitrate esters may be accomplished by any of the commonly used methods; such as, for example, esterification of the appropriate alcohol, or reaction of a suitable alkyl halide with silver nitrate.

Other convention ignition accelerators may also be used in the present invention, such as hydrogen peroxide, benzoyl peroxide, etc. Further certain inorganic and organic chlorides and bromides, such as, for example, aluminum chloride, ethyl chloride or bromide may find use in the present invention as primers when used in combination with the alkyl nitrate accelerators of the present invention.

The amount of dimerized unsaturated fatty acid used in the compression ignition fuel compositions of the present invention should be enough to provide the desired wear protection. This concentration is conveniently expressed in terms of weight percent of dimerized unsaturated fatty acid based on the total weight of the compression ignition fuel composition. A preferred range is from about 0.001 to about 2.0 weight percent dimerized unsaturated fatty acid. A more preferred range is from about 0.05 to about 1.5 weight percent dimerized unsaturated fatty acid. A most preferred range is from about 0.1 to about 1.0 weight percent dimerized unsaturated fatty acid.

The amount of alkyl nitrate or nitrite ignition accelerator used should be an amount which will achieve the level of auto-ignition sufficient to allow the operation of diesel engines on the fuel composition of the present invention. A useful range is from about 0.1 weight percent to about 5.0 weight percent based on the total compression ignition fuel composition. Preferred amounts are between 0.5 weight percent and 3.0 weight percent.

Other additives may be used in formulating the compression ignition fuel compositions of the present inventions. These compounds include demulsifying agents, corrosion inhibitors, antioxidants, dyes, and the like, provided they do not adversely effect the anti-wear effectiveness of the dimerized unsaturated fatty acid additives.

Conventional blending equipment and techniques may be used in preparing the fuel composition of the present invention. In general, a homogeneous blend of the foregoing active components is achieved by merely blending the dimerized unsaturated fatty acid component of the present invention with the monohydroxy alkanol and ignition accelerator components of the present invention in a determined proportion sufficient to reduce the wear tendencies of the fuel. This is normally carried out at ambient temperature. The following examples illustrate the preparation of some typical fuel compositions of the present invention.

To a blending vessel is added 1000 parts of 190 proof ethanol, 50 parts n-propyl nitrate and 10 parts of a blend of 40 weight percent of the dimer acid derived from linoleic acid and 60 weight percent kerosene. The mixture is stirred at room temperature until homogenous forming a fuel composition useful for reducing and/or inhibiting the amount of engine wear in internal combustion reciprocating diesel engines operating on said fuel composition.

To a blending vessel is added 1000 parts of 190 proof ethanol, 5 parts n-propyl nitrate and 1 part of a blend of 40 weight percent of the dimer acid derived from linoleic acid and 60 weight percent kerosene. The mixture is stirred at room temperature until homogenous forming a fuel composition useful for reducing and/or inhibiting the amount of engine wear in internal combustion reciprocating diesel engines operating on said fuel composition.

The amounts of each ingredient in the foregoing compositions can be varied within the limits aforediscussed to provide the optimum degree of each property.

The lubricity or wear properties of the fuel compositions were determined in the 4-Ball Wear Test. This test is conducted in a device comprising four steel balls, three of which are in contact with each other in one plane in a fixed triangular position in a reservoir containing the test sample. The fourth ball is above and in contact with the other three. In conducting the test, the upper ball is rotated while it is pressed against the other three balls while pressure is applied by weight and lever arms. The diameter of the scar on the three lower balls are measured by means of a low power microscope, and the average diameter measured in two directions on each of the three lower balls is taken as a measure of the anti-wear characteristics of the fuel. A larger scar diameter means more wear. The balls were immersed in base fuel containing the test additives. Applied load was 5 kg and rotation was at 1,800 rpm for 30 minutes at ambient temperature. Tests were conducted both with base fuel* alone and base fuel containing the test additives. Results are as follows:

The test fuel without any additive gave a scar diameter of 1.1 mm. A mixture of 40 weight percent dimer acid of linoleic acid and 60 weight percent kerosene at a concentration of 1.0 weight percent significantly reduced the wear index to 0.35 mm. A mixture of 0.5 weight percent of the additive also reduced the wear index to 0.35 mm. Lower concentration of the additive showed less anti-wear effect. Concentrations of 0.1 weight percent and 0.05 weight percent reduced the wear index to 0.41 mm and 0.48 mm, respectively.