US2481859A - Diesel fuel - Google Patents

Description

Patented Sept. 13, 1949 I DIESEL FUEL Pharis Miller, Mountainside, N. J., assignor to pment Company, a cor- Standard Oil Develo poration of Delaware No Drawing. Application August 31,1946,

Serial No. 694,438

. 2 Claims. Y i

This invention relates to improved Diesel fuels and methods for preparing the same. More particularly, this invention relates to the incorporation of a novel type of ignition-promoting agent into a hydrocarbon Diesel fuel stock, such as a gas oil fraction of petroleum origin.

In consideration of increasing the power and fuel economy in the operation of compressionignition engines, principally when the hydrocarbon fuel contains insufficient amounts of hydrocarbon compounds recognizable as serving these ends by virtue of their suitable ignition qualities, the additions of various oxygenand nitrogencontaining organic compounds have been proposed.

Hydrocarbon compounds characterized by aromatic hydrocarbons have poor ignition qualities which give rise to the vibrations manifested by knocking and result in a loss of power. A poor ignition quality in a fuel is most frequently exhibited by an excessiv ignition lag, in other words, an excessive delay between the beginning of fuel injection into the combustion chamber of an engine and the point at which ignition of the injected fuel sets in. On the other hand, normal aliphatic hydrocarbons have good ignition qualities. Normal cetane, in'particular, which serves as a standard of high ignition quality in Diesel fuel rating by recommendation of the S. A. E. Volunteer Group forcompression-ignition fuel research, has a very short ignition lag. The ignition lag of a fuel consisting of cetane and alphamethyl-naphthalene is shortened very nearly in proportion to the increase in the percentage of cetane by volume in such a blend, and when small amounts of addition agents improve the performance of a fuel in the same respect comparable to the improvement made by an increase of about 5% or more of cetane in a blend with alphamethylmaphthalene, such addition agents have been considered as having commercial significance.

The novel addition agentsof the present invention are peresters characterized by the following typical structure:

0 R-gOO-R' where R may be hydrogen, alkyl, aryl or alkaryl and R may be alkyl, aryl or alkaryl. Peroxides are well known as ignition promoters but all peroxides heretofore used have the disadvantage t that they are unstable and tend to deteriorate on storage so that Diesel fuels containing these compounds decrease in cetane number upon standing.

The above class of compounds, however, have been found to be remarkably stable in storage and to increase the cetane number of Diesel fuels to which they are added to a point where they can be used in high speed engines.

The peroxide esters of this invention may be prepared by reacting an acid chloride with an alkyl hydroperoxide in the presence of aqueous alkali in the cold. For example, tertiary butyl perbenzoate may be preparedby reacting t-butyl hydroperoxide with benzyl chloride in a 30% potassium hydroxide solution at a temperature of 10-20 C.- Similarly other alkyl peresters may be prepared, such as alkyl perfuroate, aikyl perstearate, alkyl perundecylenate, alkyl percrotonate, alkyl dipersuccinate, alkyl diperadipate, allryl diperphthalate and others.

The manner of employing and testing the pere'sters for their ignition promoting properties is illustrated in the following description.

A number of samples were prepared by dissolving from a fraction of 0.5 to 2% by volume of the compound to be tested in a portion of a 37 octane number Colombian gas oil. Each sample was tested in a C. F. R. type Diesel engine according to the method disclosed in the S. A. E. Journal of June 1936,.page 225. By this test the ignition quality improvement imparted by the addition compound is noted in terms of cetane numbers obtained.

The cetane number of a fuel is the per cent by volume of normal cetane in a blend consisting of normal cetane and alphamethyl naphthalene which gives comparable performance in the test engine and since the ignition lag of such a blend is shortened nearly in proportion to the increase in the volume percentage of the cetane, the cetane number change of a fuel is a measure of its ignition quality improvement when the cetane number change is positive.

The proportion of the ignition quality improving agent to be added to the hydrocarbon fuel may range from a fraction of one per cent to the limit of solubility in the fuel but preferably from about .025 to 5%. A gas oil boiling from about 200 F. to 700 F'., or 750 F. or in general having a suitable boiling range for use as a fuel in Diesel type engines may be used as the hydrocarbon fuel under some circumstances, a more narrowly cut fraction such as one distilling from about 400 F. to 600 F. or from 500 F. to 700 F. may be used. Ordinarily, the hydrocarbon fuel may be said to have aboiling range above that of gasoline.

The e 'lectiveness of the peresters in raising the cetane number of'the fuel and in storage stability is illustrated comparing tests on an unmodified hydrocarbon Diesel oil with tests on samples of the same fuel modified by small amounts of a perester. Comparative tests are also shown of the effect of other types of peroxide ignition promoters. The storage stability was obtained by allowing the fuel containing the promoter to stand over water in rusty iron pets at 125 F. for five weeks and ten weeks and then testing for cetane number and peroxide number.

1 Gram mol. equivalents of active oxygen per 1000 liters of oil.

From the above data it is clear that 1% of the t-butyl perbenzoate is more effective in increasing the cetane number than either t-butyl hydroperoxide or l-hydroxy cyclohexyl-l-hydroperoxide and that furthermore it does not deteriorate in storage as do the other two peroxides.

This invention makes commercially feasible the preparation of Diesel fuels giving satisfactory engine performance from crude oils, gas oils and residual fuels having low pour points, low A. P. I. gravities and high heat Values, such as those procured from naphthene base, asphalt base or mixed base stocks by the addition of active perester compounds described in small quantities. The burning qualities of gas oils from parafiln crudes are also enhanced by these novel addition agents.

Small quantities of the novel addition agents of this invention may be used for adapting various mixtures of hydrocarbons for use as Diesel fuels, including recycle stock from a cracking operation, non-parafllnic extracts, oils from destructive distillations of pyrobituminous and as phaltic materials, mixtures of these with one another or with crude petroleum fractions. Other agents for enhancing various other qualities without detracting substantially from the ignition qualities of the fuel may be admixed, such as, oiliness agents, sludge dispersers, dyes, corrosion inhibitors, anti-oxidants, viscosity improvers, pour depressants and gum solvents. Also other promoters of ignition qualities may be admixed.

The nature and objects of the present invention having been thus described and illustrated, what is claimed as new and useful and is desired to be secured by Letters Patent is:

1. A fuel for compression ignition engines of the Diesel type consisting essentially of a hydrocarbon fuel which contains from about 025% to 5% of tertiary butyl perbenzoate.

2. Composition as defined by claim 1 wherein said hydrocarbon fuel boils in the range from about 200 F. to 750 F.

' PHARIS MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS ical Society, vol. 68, pages 642-644, April 1, 1946.