US2933380A - Motor fuels - Google Patents

Description

United States Patent MOTOR FUELS Matthew R. Kegelmau, Claymont, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware N0 Drawing. Application June 22, 1955 Serial No. 517,350

6 Claims. 01. 44-69 This invention relates to motor fuels and more particularly to motor fuels for spark-ignition engines which motor fuels contain tetraethyl lead and an agent for reducing the harmful effects of combustion chamber deposits upon the performance of the fuels in the engines.

. When motor fuels containing tetraethyl lead are employed in spark-ignition engines, they form deposits, chiefly inorganic, in the combustion chambers of the engines, even in the presence of lead scavenging agents. The build up of such deposits, particularly in modern high compression ratio engines, is known to cause occasional premature ignition of the fuel-air charge. The octane value of the motor fuel, required to suppress knock and other forms of combustion noise, must be increased as the accumulation of the deposits in an engine is continued. octane requirement increase continues until a fairly constant value is attained. However, occasional premature ignition will require a still further increase in the octane value to suppress noise.

It is also known that lubricating oils, employed to lubricate the engines, tend to form sludge which separates from the oil around the piston rings and forms deposits of organic materials and carbon. It has been proposed to incorporate various substances, includinggalkaline earth salts of organic acids, in the lubricating oils for inhibiting the formation of the sludge and to modify the carbon and organic deposits so that they are rendered soft and friable and easily removed by the detergent action of the substances in the oils; Such substances do not appreciably affect the deposits formed by the motor "fuels which are chiefly formed on the upper parts of the combustion chamber not reached by the lubricating oils and which are entirely different from the deposits formed by the lubricating oil sludges.

, To be practical, an agent for overcoming the effects of deposits arising from the motor fuel must 'be introduced into the engine in the motor fuel through the induction systems with which the engines are equipped. This requires that the agent must be soluble in the motor fuel and without harmful effect upon its stability, color, clarity, ami-knock properties, etc. Further, most diflicult requirements are that the agent must be carburetable with the motor fuel, must fonn no deposits in the induction systems (particularly where the temperatures are high, as near the intake ports), should be without harmful effects upon such structures as valves, and valve-seats, and should not increase the amount of combustion deposits in the engine. In general, the alkaline earth salts and like materials, which have been proposed for use in lubricating oils, do not meet these requirements, particularly the requirement for carburetability.

It is an object of this invention to provide a group of agents which, when employed in a motor fuel containing tetraethyl lead, will modify the combustion chamber deposits in a spark-ignition engine so as toreduce the octane -requirement of the engine normally caused by such deposits. Another object is to provide motor fuels containing such agents which will reduce the ignition of the lce fuel-air mixture normally caused by hot combustion chamber deposits. A particular object is to provide motor fuels containing agents of the aforesaid character which can be carbureted with the motor fuel and will not form deposits in the induction systems of spark-ignition engines. Further objects are to provide motor fuels containing such agents which are not harmful to the motor fuel or the engine parts and which do not noticeably increase the amount of combustion chamber deposits. Other objects are to provide new compositions of matter and to ad- Vance the art.

The above and other objects are accomplished in accordance with this invention which comprises providing a motor fuel consisting essentially of hydrocarbons in the gasoline boiling range, tetraethyl lead, a lead scavenging agent, and from about 0.003% to about 0.3% by Weight of an oleylsalicylate of at least one alkaline earth metal of an atomic number from 20 to 5 6, inclusive.

The basic motor fuel, ordinarily, will be gasoline, but may be composed primarily of any hydrocarbon or mixture of hydrocarbons in the gasoline boiling range which is suitable for use as a fuel for spark-ignition engines, including paratfinic, naphthenic and aromatic hydrocarbons. Such motor fuels may also contain antioxidants, stabilizers, dyes, metal deactivators, or other compounds which are commonly employed in motor fuels.

The motor fuel contains tetraethyl lead, usually in the proportions normally employed in motor fuels for the particular spark-ignition engine. The proportion of tetraethyl lead usually will be in the range of from about 0.03% to about 0.3% by weight; 0.5 cc. of tetraethyl lead per gallon of motor fuel providing 0.03% by weight.

Also,the motor fuel contains a lead scavenging agent in the proportions ordinarily employed in motor fuels containing tetraethyl lead, i.e. from about 1 to about 5 theoriesbased on the tetraethyl lead. The lead scavenging agents are well known to the art and are compounds which contain chlorine or bromine or both, the most commonly employed scavenging agents being ethylene dichloride, ethylene dibromide and mixtures thereof. One theory of a scavenging agent is that amount which provides 2 atoms of active halogen per atom of lead.

The alkaline earth metal oleylsalicylates of this invention are calcium oleylsalicylate, strontium oleylsalicylate, barium oleylsalicylate, and mixtures of any two or more thereof. They have the alkaline earth metal replacing the hydrogens of the hydroxyl groups of two salicylic acid radicals while the hydrogens of the carboxylic acid groups of the salicylic acid radicals are replaced by oleyl radicals. Thus, they may be represented by the formula CIJOOR (I'JOOR wherein M represents Ca, Sr or Ba and R represents the oleyl radical.

The compounds are prepared in conventional manner by reacting salicylic acid with oleyl alcohol to form the oleyl ester of salicylic acid and then reacting that ester with the alkaline earth metal hydroxide or other suitable alkaline earth metal compound. Suitable methods are those which are known to the art for making long chain alkyl esters of salicylic and like hydroxy acids and the alkaline earth salts of those esters, such as those disclosed by Finley in Patent No. 2,339,692. Illustrating the preparation of the alkaline earth metal oleylsalicylates of this invention:

Salicylic acid (36.4 parts by weight) and oleyl alcohol (68.5 parts) were dissolved in 34 parts of xylene contain- 3 ing 3 parts of paratoluene sulfonic acid as an ester'ification catalyst in a pot surmounted by a reflux condenser provided with a separator for removing water from the condensate. The solution was refluxed viborously for 8 hours, removing the water (formed in the esterification) from the reflux. The acidity of the unchanged salicylic acid and catalyst was then determined by titration with standard 0.1 N sodium hydroxide solution, using methyl purple as the indicator. These acids were then neutralized by adding with agitation a calculated excess of sodium carbonate as a 10% solution in water. After removing the water layer from this neutralization, thus removing unreacted salicylic acid and the para-toluene sulfonic acid as their sodium salts, 9.8 parts of dry calcium hydroxide were added with agitation to the organic layer, followed by reflux to remove water, then by filtration to remove the insoluble solids. The xylene was then removed by vacuum distillation ending by heat- C. at 25 mm. The residue was calcium ing to 150 brownish liquid, soluble in oleylsalicylate, a viscous, gasoline in all proportions.

V The alkaline earth metal oleylsalicylates of this invention are liquids at ordinary temperatures and are quite soluble in gasoline and like motor fuels of this invention. When small amounts thereof are dissolved in the motor fuels containing tetraethyl lead and a lead scavenger and such motor fuels are used in spar-k-ignitionengines, they alter the combustion chamber deposits, normally formed by the motor fuels, so that the undesirable effects ofthose deposits are greatly decreased. That is, theyare 'very effective in reducing the normal increase in octane demand of the engine caused by the deposits and in reducing the tendency of the deposits to cause premature ignition of the fuel-air charges and noise in the engines.

They are carburetable with the motor fuelsand do not form deposits in the induction systems for the engines. This last feature is particularly surprising'and renders the compounds practical. They are not volatile at the temperatures of the induction systems. Other alkaline earth metal compounds such as calcium naphthenate and the salts of alkyl salicylates, e.g. calcium capryl salicylate and a liquid mixture of calcium stearyl salicylate and calcium hexadecyl salicylate, are not carburetable with the motor lfuels but form objectionable deposits in the induction systems for the spark-ignition engines. The oleylsalicylates, being unsaturated, would be expected to be less stable than the alkyl salicylates and hence to decomposeat least to some extent, so that the inorganic portion, being insoluble, would form deposits in the hot parts of ,the induction systems such as the manifolds, more readily than the alkyl salicylate. No explanation can be given for this critical difference in the compounds of this invention.

In addition, the alkaline earth metal oleylsalicylates of this invention do not cause any objectionable change in the properties of the motor fuel, such as its color or stability. Usually, they materially increase the stability of the motor fuel. They do not increase or significantly decrease the amounts of combustion chamber deposits in the engines, and do not have harmful effects. on valves, valve seats or like structures of the engines. They have no harmful effects on the tetraethyl lead or the lead scavengers or interfere with their actions. While they decrease somewhat the octane values of the motor fuels, such effect is very slight and of no practicalsignificance.

Ordinarily, the quantity ofthe alkaline earth metal .oleylsalicylates employed in the motor fuels in accord with this invention will be in the range of from about 0.003% to about 0.3% by weight of the motor fuel, i.e. from about 0.075 gram to about 7.5 grams per gallon of motor fuel; 1 gram per gallon being 0.04% by weight. Quantities smaller than 0.003% do not always give an effect of practical significance. Quantities larger than 0.3%

,do not give correspondingly greater effects which ordinari- 1y would justify their use, and large excessive quantities ferred modes of carrying it into effect, and advantageous results obtained thereby, the following examples are given:

EXAMPLE 1 Tests were conducted in a Waukesha CFR D909 supercharged single-cylinder engine mounted on a test stand, with a 25 HP. electric induction motor to absorb the output of the engine. This overhead-valve engine was equipped with a variable compression ratio head containing four spark plug holes. The displacement of the engine is 37.33 cubic inches and the head was adjusted to give a compression ratio of :1. The engine was equipped with a fuel injection system which injected the fuel into the intake air stream ahead of the intakeport. The engine was operated under cyclic load conditions, with control of the intake air pressure and fuel injection rate being supplied by an electric timer. The cyclic operation consisted of 19.5 minutes of operation at part load followed by 30 seconds of operation at full load.

During the 19.5 minutes of part load, the engine was operated under the following conditions:

Speed, r.p.m. 1800 Spark advance, B.T.C. 10 Intake manifold air pressure, in. Hg abs. l0 Fuel/air ratio 0.075 Coolant temperature, F. 212 Intake air temperature, F ,250 Oil temperature, F. Indicated mean effective pressure, p.s.i. 45

During the 30 seconds of full load, the engine was operated under the following conditions:

Speed, rpm. 1800 Spark advance, B.T.C. 1 10 Intake manifold air pressure, in. Hg abs 30 Fuel/air ratio 7 0.070 Coolant temperature, F. 212 Intake air temperature, F 250 Oil temperature, F. 160 Indicated mean effective pressure, p.s.i. .135

to flow thus providing a signal which indicates the arrival of a flame at the gap. This signal from the ionization gap was electronically amplified and was used to actuate a counter; The amplifier was turned on and off by a set ofdistributor points driven by the engine so that only those flame fronts reaching the ionization gap at least five crankangle degrees before the normal flame would be counted; The counter registered, therefore, the number of abnormal flames which were initiated before the spark throughout each of the 30-second periods when the engine was at full load. As these flame fronts were initiated by the combustion chamber deposits, the test provides a measure of the relative tendency of combustion chamber deposits to cause premature ignition or preignition. i

Use of a fuel, consisting of 90 volume percent catalytically cracked hydrocarbons and 10 volume percent motor alkylate and containing 3.0 ml. of tetraethyl lead per gallon, 1. 0 theory of chlorine as ethylene dichloride, 0.5 theory of bromine as ethylene dib'romideand 1.0 g. per

gallon, 0.04% by weight, of calcium oleylsalicylate, resulted in a total number'of counts of 696 for 40 hours operation. Theuse of 2.0 g. per gallon, 0.08% by weight, of calcium oleylsalicylate in the same fuel resulted in a count of 394 for the test period of 40 hours. Control tests, without the calcium oleylsalicylate, gave counts between 2000 and 3000 for 40-hour runs. In all tests, an SAE 30 weight oil was used as the crankcase lubricant.

Inspection of the engine at the conclusion of the test showed that the induction system of the engine was free of deposits. Both the intake and exhaust valve seats were in good condition and there'was no evidence of valve burning. There was no noticeable additional build up of deposits within the combustion chamber due to the use of calcium oleylsalicylate in the fuel.

When 2.17 g. per gallon, 0.087 by weight, of barium oleylsalicylate was substituted for the calcium salt in the above experiment, the total number of counts were 260 and 233 for duplicate tests of 40 hours operation. When 2.58 g. per gallon, 0.103% by weight, of strontium-oleylsalicylate was substituted in the above test, the counts were between 215 and 330 for tests of 40 hours operation. Neither the barium salt nor the strontium salt resulted in increase in the combustion chamber deposits, damage to the valves, or deposits in the induction system of the engine.

EX M L 2 A 1954 Oldsmobile Super 88 automotive engine, which was equipped with a four-barrel carburetor and had been modified by the use of special high compression heads to operate at a compression ratio of 9.0:1, was coupled to a dynanrometer and operated under low-duty, cyclic conditions for a period of from 200 to 250 hours which was approximately the equivalent of 4000 miles of highway driving in a 1954 Oldsmobile Super 88 passenger car. The fuel for this engine test consisted of a mixture of 90 volume percent catalytically cracked hydrocarbons and volume percent motor alkylate to which was added 3.0 ml. of tetraethyl lead per gallon, 1.0 theory of chlorine as ethylene dichloride and 0.5 theory of bromine as ethylene dibromide. An SAE 20W weight oil was used as the crankcase lubricant. The engine operation was controlled by an electric cycle timer which permitted the engine to be operated for 30 seconds at 500 r.p.m., no load, 2% degrees before top dead center spark-ignition timing and then for 30 seconds at 1500 r.p.m., brake horsepower, and 30 degrees before top dead center sparkignition timing. At the start of the test and at threehour intervals thereafter, the octane quality of the fuel required for the elimination of audible knock and all other forms of noise caused by abnormal combustion was determined while the engine was accelerated under conditions simulating a highway acceleration from to 50 mph. using the fourth gear of the Oldsmobile Hydra matic transmission.

The quality of fuel required for the suppression of noise at the start of the test, when the combustion chambers of the engine were essentially clean and free of de posits, was 78 Army-Navy performance number. After 100 hours of operation in a control test, the quality of fuel required for the suppression of noise had increased to 100 performance number and at 200 hours the fuel requirement had increased to 116 performance number. During the next 50 hours of operation, the fuel quality requirement remained essentially constant at this level and, at the end of 250 hours of operation, was 116 performance number.

In a similar test using the same fuel with 1.0 g. per gallon, 0.04% by weight, of calcium oleylsalicylate, the fuel requirement of the clean engine was 82 performance numbers. After the first 100 hours of operation, the requirement was essentially unchanged and, at the end of 210 hours, was 108 performance number or 8 performance numbers lower than the equilibrium requirement'observed when the engine was operated without calcium oleylsalicylate.

During most of the accelerations conducted on the control tests, a rumbling noise was noticed at the high speed end of the ratings after about 20 hours of operation. This rumbling is believed to be due to surface ignition phenomena caused by the deposits. The noise was virtually eliminated in the test containing the calcium oleylsalicylate in the fuel.

Inspection of the induction system revealed that there was no deposit build up in the intake manifold or in the intake ports after the test using the fuel containing the calcium oleylsalicylate. Both the intake and exhaust valve seats were in good condition and there was no evidence of valve burning.

EXAMPLE 3 The products of the present invention have the additional advantage that they have a beneficial effect on the induction period (stability) of commercial gasoline as determined in accordance with ASTM Designation D525-49. This is illustrated by the following Table I, wherein the induction period, in minutes, was deter-, mined for two representative commercial gasolines, A and B, each of which contained 3.0 ml. of tetraethyl lead per gallon of gasoline, both without a compound (alkaline earth metal oleylsalicylate) of this invention and with each of the compounds in a proportion of 4.0 grams per gallon of gasoline:

A still further advantage of using the agents of this invention is that they have no significant deleterious effect on the antiknock effectiveness of tetraethyl lead. This is shown by a series of tests using fuel blends consisting of volume percent commercial catalytically cracked stock and 10 volume percent of commercial motor alkylate, without tetraethyl lead (unleaded) and with 3.0 ml. of tetraethyl lead per gallon of fuel blend (leaded). The research octane numbers of each fuel blend, without added compound and with varying amounts of barium, calcium, or strontium oleylsalicylate, were determined in accordance with ASTM Designation 39(12-53. The results are shown in the following Taaasasso It will be understood that the foregoing examples are given for illustrative purposes solely, and that this invention is not limited' to the speeificembodiments so illustrated. It willbe apparent that the proportionsof the alkaline earth metal oleylsalieylates, of tetraethyl lead and of the lead scavenging agents employedmay be varied within the ranges set forth in the general description. Likewise, the hydrocarbons constituting the basic motor fuel, the lead scavenging agents, the other additives in the motor fuels, and the like may be varied as indicated in the general description and in the manner known to the art without departing from the spirit and scope of this invention.

'It will be apparent that this invention provides novel motor fuels containing agents which greatly improve the performance of spark-ignition engines in which they are used, which are practical for such use, and which are without harmful efieetson the motor fuelsand on the engines. Accordingly, this invention constitutes a valuable advance in and contribution to the art. 4 I

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: i i

I. A motor fuel consisting essentially of hydrocarbons in'the gasoline boiling range, tetraethyl lead, a halohydrocarbon lead scavenging agent, and from about 0.003% to about 0.3% by weight of at least one ,oleylsalieylate of an alkaline earth metal of'an atomic number from 20 to 56.

2. A motor fuel consisting essentially of hydrocarbons in the gasoline boiling range, tetraethyl lead, a halohydroearbon lead scavenging agent, and from about 0.04% to about 0.16% by weight of at least one oleylsalicylate of an alkaline earth metal of an atomie number from 20 to 56. j y, r

3. A motor fuel consisting essentially'of hydrocarbons in the gasoline boiling range, tetraethyl lead, a halohydrocarbon lead scavenging agent, and from about 0.003% to about, 0.3% by weight of calcium oleylsalicylate 4. A motor fuel consisting essentially of hydrocarbons in the gasoline boiling range, tetraethyl lead, a halohydrocarbon lead scavenging agent, and from about 0.04% to about 0.16% by weight of calcium oleyl salieylate. fl y 5. A motor fuel consisting essentially of hydrocarbons in the gasoline boiling range, tetraethyl lead, a halohydroearbon lead scavengingagent, and from about 0.03% to about 0.3% by weight of barium oleylsalicylate. 1;;

6. A, motorfuel consisting essentiallyflof hydrocarbons in the gasoline boiling range, tetraethyl lead, a halo.- hydroearbon. lead scavenging agent, and .from about 0.003% to about 0.3% by weight of strontium oleylsalicy ate. J 2:

References Cited theof patent Q Irish et a1.. May 13, 1258

Claims (1)

1. A MOTOR FUEL CONSISTING ESSENTIALLY OF HYDROCARBONS IN THE GASOLINE BOILING RANGE, TETRAETHYL LEAD, A HALOHYDROCARBON LEAD SCAVENGING AGENT, AND FROM ABOUT 0.003% TO ABOUT 0.3% BY WEIGHT OF AT LEAST ONE OLEYLSALICYLATE OF AN ALKALINE EARTH METAL OF AN ATOMIC NUMBER FROM 20 TO 56.