US2331386A - Modified fuel - Google Patents

Description

Patented a. "i2, 1943 UNITED STATES PATENT OFFICE- zr-srsse MODIFIED FUEL Peter J. Gaylor, Union, N. 1., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application November3, *1939.

. Serial No. 302,689

7 Claims.

This invention relates to liquid fuels of the type employed in oil furnaces and those used in internal combustion automotive engines, particularly to high flash point spark-ignition engine fuels adapted .for injection type engines. It involves the addition to liquid fuels of certain modifying agents which favorably alter the lubricating actionfwhile on the other hand increased VlSOOSitYj'Of a fuel interferes with em ciency of the delivery device anddispersion of the fuel into the combustion chamber. Further difiiculty in the injection 'of fuels arises from their tendency to form deposits in spray nozzles, thereby clogging extremely small fuel channels and orifices in the atomizing spray nozzles.

An object of this invention is to .confenon hydrocarbon fuels properties which permit them to pass readily through the injection device and become'e'iiiciently atomized thereby, while they act satisfactorily as lubricants and keep the iniection in a satisfactory condition. more specific object is to improve spark-ignition en- "gine fuels in these respects by addition agents which are of substantial benefit to the anti-- knock value of the fuels. advantages will become apparent from the fol- Further objects and lowing description.

Broadly, the objects of this invention are obtained by blending with a liquid hydrocarbon fuel base minor amounts of certain substances found to possess a remarkable ability for making the oil blends spread over metal surfaces and for weakening cohesive forces of the oil molecules so that the oil can be more efllcientlyatomized.

is believed to be unstable to exist as such, but

' the radical of this acid is present ina series of ester derivatives in which at least one of the hydrogen atoms in the carboxyl groupsis replaced by a hydrocarbon group, such as an alkyl group, an arylgroup, or substituted groups of these types which form-esters of carbonic acid. A variety of closely related derivatives include esters in which a halogen, such as chlorine; re-

places. one of the hygiroxy groups and esters in which a nitrogen-containing groupis present.

The carbonate ester blending agents used according to the present invention are preferably The substances which affect fuel compositionsin 7 these respects belong to the class of compounds known as ester derivatives of carbonic acid. Carbonic acid as itself, HaCOa, with the theoretical structural formula:

selected to have boiling points which come within the range of the desired fuel composi- .tion. pared from by-products of petroleum refining, as for example, by known basic methods which involve the reaction of carbon monoiiide. and chlorine, or carbonyl chloride, with an alcohol, also, of carbonic and chloro-carbonic esters with amines. The following examples will serve to illustrate modes of formation-of the carbonate esters used in the practice of this invention:

Example 1 v Equimolar proportions of carbon monoxide and chlorine are made to combine in sunlight to ,form carbonylchloride known by the common name phosgenelf The phosgene reacted with ethyl alcohol produces ethyl chloro-carbonate, with splitting out of. hydrogen chloride. Ethyl chloro-carbonate, which has an ester and an acid chloride, reacts directly with an equimolecular" proportion of ethyl alcohol to form diethyl carbonate. Y

Example-2 In place of reacting the ethyl chloro-carbonate with alcohol, it is reacted with an amine in an equimolecular proportion to form a derivative of carbonic acid which is an ester and an amide.

It is of no consequence, which hydrocarbon radical is present in reactants used in synthesiz ng the carbonate esters.

Of the various carbonic acid derivatives, a type which functions particularly well for the objects of this invention embraces those which behave as true esters. Specific examples of the alkyl esters are the methyl, ethyl, propyl, isopropyl, and butyl carbonates, also, the homologous. alkyl carbonates which contain two different alkyl groups.

' Aryl carbonates, such as creosote carbonate,

They are easily and economically prehalogen substituent, e. g. an alkoxy group may be replaced by a halogen as in chlorocarbonates, or a nitrogen-containing group as in the ester amides of carbonic acid. For the purpose of the present invention, however, the dialkyl carbonates are preferred.

In making an improved motor fuel for high compression spark-ignition engines, a light petroleum distillate, a synthetic fuel or mixtures thereof, obtained by any of the known commercial processes may be used as the hydrocarbon base; for instance, ordinary gasoline having a boiling range within the limits of 100 F. and 450 F. may beused. The present invention, however, is adapted more for the heavy liquid fuels such as those for injection type engines, having the safety advantage of a high flash point, the initial point of the fuel being about 300 F. and the end point approaching even 600 F.; but for aviation motors, the end point should not far exceed 400 F. or 450 F.

To improve high speed compression-ignition engine fuels and heating oils, the hydrocarbon base fuel may have a boiling range within the limits 400 F. and 700 F. or a still higher boiling range.

The esters of carbonic acid used as the improving agents are blended with the hydrocarbon base in any desired proportions up to the limits (if any) of their solubilities in the fuel,-

Although it is true that mechanical features more or less govern the eiliciency of an oil burner, it is possible'to improve the tendency for oils to form fine droplets by adding thereto, substances which will affect the surface tension characteristics of the oil. Oil-soluble carbonates of the type described herein considerably lower the surface tension of liquid fuels causing the oil to spread and break up into small particles readily.

By the addition of a fraction of a percent or more of such a substance, it is possible to improve a fuel to such an extent that it will atomize readily even under adverse mechanical conditions.

The'effectiveness of the carbonic ester derivatives for lowering the surface and interfacialtension of a fuel oil, thereby giving better injection delivery and spray penetration is visibly demonstrated by a spread measurement test. In this test, a minor amount of the agent is blended with a refined mineral oil such as one which may be used as a fuel and precisely measured drops are allowed to spread on a polished metal plate under fixed conditions. The area of spread for each sample tested is measured and expressed in percentage of the spread area for the hydrocarbon base oil containing no addition agent, the hydrocarbon base oil being referred to as the blank. Typical comparative tests are shown in the following table:

Composition Q52 3 Per cent Blank 100 Blank-+30% di-n-butyl carbonate. 180 B lank+3.0% diethyl carbonate 130 The foregoing tests illustrate how the carbonic esters in a very unique manner are valuable aids for delivering the fuel through the injection system and for breaking up the fuel into numerous uniformly small droplets at the nozzle orifice. By the aid of this factor, good distribution can be obtained even in fuels of high viscosity and low volatility to promote eflicient ignition and combustion. Improvement of the injection system condition is also believed accountable to the cium,.and other oil-soluble metal soaps, reverse soaps such as onium soaps, e. g. cetyl pyridinium chloride, alcohols, ketones, etc.

In practice, the proportion of the carbonic ester is preferably used in a concentration of 1% to 10% by volume of the fuel composition. For obtaining increased improvement in the anti-knock or octane blending value of the fuel aswell as in the physical characteristics of the composition preferably in the .proportion of the carbonic ester should be above 3%, say 5% or 10% or even more. However, in compression-ignition engine fuels, the proportion is preferably more limited to less than about 5% and in some instances 3%, since in higher proportions the carbonic acid derivatives are not knock-suppressors in such fuels, althou h they do not adversely affect the cetane number of a Diesel fuel to any appreciable extent when used specifically therein to improve the surface tension characteristics of the fuel.

The present invention is highly suited for improving furnace oils and other heavy liquid fuels.

blending agent to more readily pass through the narrow channels in the nozzle and thereby avoid stationary oil layers which tend to form clogging deposits.

It can be readily appreciated that the blending agent serves more advantageously if it is not detrimental to the combustion qualities of the fuel.

' The preferred blending agents of the present-invention have been found to have excellent antiknock values for spark-ignition or Otto cycle engines as shown by A. S. T. M. determinations of their effects on hydrocarbon fuels. Forexample, diethylcarbonate, (C2H5O)2C:O, which boils at 260 F., has an A. S. T. M. octane blending value of 96 in a 78.7 octane number (A. S. T. M.) gasoline reference fuel when employed therein in a 5% by volume concentration. These results were checked with other reference fuels containing similar proportions of the alkyl carbonate. A 73.9 (A. S. T. M.) octane number fuel was improved to an octane number of by 5% of the alkyl carbonate, indicating that the alkyl carbonate has a blending value of 98. The corresponding amide ester, (C2H5O)CO-NHC:H5, tested in the same manner was found to have an A. S. I. M. blending value of 100. When blended.

in a 6% by volume concentration with a, Diesel fuel, the alkyl carbonate showed no appreciable alteration in the cetane number of the fuel, thus indicating the blending agent can properly be used to such an extent in compression-ignition engine fuels without detriment to their ignition qualities. Moreover, they can be used in larger proportions in a Diesel fuel together with ignition quality promoters if it is considered necessary to compensate for any lowering of the octane number which might be found to arise from the carbonate ester. A number of analogous carbonate esters were tested and similar advantageous results were obtained.

From the foregoing, it will be seen that the carbonate ester blending agents may serve very is not to be limited by the specific examples nor by the theory of the mechanism through which the desired improvements are obtained.

I claim:

1. An improved liquid fuel composition comprising a major proportion of a hydrocarbon li uid fuel base having an initial boiling point at least as high as 300 F. blended with a minor proportion of a soluble dialkyl ester of carbonic acid in suflicient amounts above 1% to substantially lower the surface tension of the fuel.

2. A composition as described in claim 1, in which the liquid fuel base is a heavy petroleum oil. 3. An improved fuel for injection type internal combustion engines comprising a hydrocarbon usefully in very viscous fuel oils or be'used together with thickeners that increase the viscosity of the fuel since the spreading effect of the ester carbonates diminishes-the cohesion tendencies of thickened or. viscous oils. Accordingly, a nonviscous fuel base may be improved in viscosity, lubricity, and other characteristics, by a thickener or V. I. improver such as iso-olefln'polymers, soaps, fatty oils, and the like, and still be made to flow properly and be emciently atomized by the injection system. Likewise, the modification by the carbonate esters adapts ordinarily less desirable heavy fuel oils for use in compression-ignition engines. Other addition agents may also be incorporated into the fuels with improvement by the ester carbonates, for example, lubricants, high boiling gum flux oils, oxidation inhibitors, pour point depressants, etc.

The amide esters of carbonic acid disclosed herein are claimed in copending application Se rial No. 481,557, filed April 2, 1943.

Other variations of the invention will be apparent to those skilled in the art, and theinvention I fuel base stock boiling between about 300 F. and about 700? F. and a minor proportion of a soluble dielkyl carbonate ester in an amount above 1% sufficient to improve spreading characteristics of the fuel.

'4. A fuel composition as described in claim 3, in which said carbonate ester is dibutyi carbonate.

5. An improved spark-ignition engine fuel comprising in a major proportion a naphtha fraction boiling in the range of about 300 F. to

600 F. and from about 3% to 10% by volume of a soluble dialkyl carbonate ester.

6. A liquid motor fuelfor high-compression spark-ignition engines comprising a hydrocarbon fuel containing gasoline hydrocarbons and a minor proportion of a soluble dialkyl carbonate in sumcient amount of at least about 5% to improve the anti-knock value of the fuel.

7. A motor fuel composition as described in claim 6, in which said dialkyl carbonate is dibutyl carbonate.

PETER -J. GAYLOR.