US2989386A - Gasolines containing combustion chamber deposit modifiers - Google Patents

Description

June 20, 1961 w. E. LOVETT ET AL 2,989,386

GASOLINES CONTAINING COMBUSTION CHAMBER DEPOSIT MODIFIERS Filed Sept. 24, 1958 2 Sheets-Sheet 1 EFFECT OF LENGTH OF ALKYL GROUPS IN TRIALKYL PHOSPHORUS ESTERS UPON GASOLINE RESEARCH OCTANE NUMBER 5 TERT'BUTYL '5: 4 ol 'ME'PENTYL E lso-p opy l,3'Dl-ME'BUTYL SEC'BUTYL '5' 3 ETHYL O ISOBUTYL Z'ETHYL z-sn-m.

5 JJ g ON'BUTYL O BUTYL O NEXYL WDECYL I N'OCTYLO O I f or N-ALKYL ESTERS 53' N'HEXYL 0 D: o 1 1 1 I v O I 2 3 4 5 6 7 8 9 IO CARBON ATOMS PER ALKYL GROUP William E. Ldvefr Richard F. Neblerr Inventors By W i Attorney June 20, 1961 Filed Sept. 24, 1958 A UNIONTOWN OCTANE NUMBER GASOL w. E. LOVETT ETAL 2,989,386

was CONTAINING COMBUSTION CHAMBER DEPOSIT MODIFIERS 2 Sheets-Sheet 2 EFFECT OF TRI(C 'OXO) PHOSPHATE CONCENTRATION UPON GASOLINE OCTANE QUALITY CONCENTRATION OF TRI c -0x0 PHOSPHATE IN GASOLINE,THEORIES FIG.- 2

William E. Lovert Inventors Richard F. Neblefi B W Q Attorney Unite tates Patent 2 989,386 oAsoLiNEs CONTAINING COMBUSTION CHAMBER DEPOSIT MODIFIERS William E. Lovett, Scotch Plains, and Richard F. Neblett,

Elizabeth, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 24, 1958, Ser. No. 762,964 3 Claims. (Cl. 44--69) The present invention relates to fuels for use in internal combustion engines and more particularly relates to leaded gasolines having incorporated therein additive agents singularly adapted to reduce surface ignition, spark plug misfiring and related phenomena in gasoline engines without lowering fuel octane quality.

It is known that the use of tetramethyl lead, tetraethyl lead and similar alkyl lead compounds as gasoline antiknock agents is accompanied by the formation of combustion chamber deposits. These deposits, consisting primarily of unburned carbon, lead salts and lead oxides, rapidly accumulate upon the pistons, cylinder heads, valves, spark plug insulators and other surfaces within the combustion chambers of engines operated upon leaded fuels. Because they have relatively low ignition temperatures, such deposits become incandescent during engine operation and cause surface ignition, a premature igniting of the fuel-air mixture during the compression stroke of the engine. They also foul the spark plugs, causing them to misfire, and are responsible, over a period of time, for an increase in the fuel octane quality required for satisfactory engine operation. The adverse effects of such combustion chamber deposits are particularly pronounced in modern engines having compression ratios above about 9 to l and include rumble, a vibration within the engine caused by improper fuel combustion, and other phenomena not encountered in low compression ratio engines.

In order to minimize the formation of combustion chamber deposits in gasoline engines operated upon leaded fuels, lead anti-knock agents are used in gasolines in conjunction with scavenger agents designed to react with the lead during combustion and form volatile products which will be readily swept from the engine combustion chamber with the exhaust gases. The compounds generally used as scavenger agents in this manner are alkyl halides, particularly ethylene dichloride, ethylene dibrornide and mixtures of the two. Although such scavenger agents do reduce the amount of deposits formed, they do not eliminate the difiiculties referred to above. Many of the halogen-containing lead compounds formed as a result of reac tions between the lead anti-knock agents and the halohydrocarbon scavengers are solids at temperatures prevailing within the combustion chamber and are included in the deposits formed. These compounds tend to further reduce the ignition temperature of the deposits and hence may actually promote surface ignition and related difliculties.

In addition to the halohydrocarbon scavenger agents, certain phosphorus compounds have been incorporated into leaded gasolines in order to reduce the adverse effects attributable to the formation of combustion chamber deposits. These phosphorus compounds, like the halohydrocarbons, enter into reactions with the lead during combustion. Their action is somewhat different from that of the halohydrocarbons, however, in that they are primarily intended to form solid phosphorus containing compounds rather than gaseous reaction products. Deposits containing phosphorus have very high ignition temperatures and are much less prone to cause surface ignition than are deposits containing no phosphorus. There are indications in the literature that the quantity of deposits may also be reduced when phosphorus additives are used.

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The phosphorus compounds employed as auxiliary scavenger agents in leaded gasolines in the past have been limited to aryl phosphates and phosphites, despite the fact that the corresponding alkyl esters reduce surface ignition and other difiiculties caused by combustion chamber deposits and are better suited for use as gasoline additives than the aryl compounds because of their lower boiling points and greater solubility in gasoline. Alkyl phosphorus esters seriously affect the octane quality of leaded gasolines to which they are added. Studies have shown that the alkoxy groups of such esters react with tetraethyl lead and similar alkyl lead compounds before the gasoline reaches the combustion chamber. Since the products formed do not behave as anti-knock agents, these reactions may result in a decrease in the octane rating of the gasoline equivalent to the increase effected initially by the addition of the lead anti-knock agents. Aryl phosphorus compounds, on the other hand, apparently undergo such reactions to a lesser extent and hence have a less serious effect upon the octane quality of leaded gasolines.

This effect of alkyl phosphorus esters upon the octane quality of leaded gasolines is of paramount importance because of the high fuel octane levels required for satisfactory operation of modern gasoline engines. The cost of raising fuel octane quality by one octane number frequently amounts to a cent or more per gallon and Will undoubtedly rise to an even higher figure as fuels of higher octane number become necessary. Because of this cost, additives which depress octane quality significantly cannot be tolerated and therefore, in spite of the fact that they have superior physical properties, alkyl esters of phosphorus are not used as combustion chamber modifiers in leaded gasolines.

The present invention provides a new and improved class of phosphorus additives for use in gasolines which are effective in reducing octane requirement increase, surface ignition, spark plug fouling and related difficulties attributable to the formation of combustion chamber deposits and. which at the same time do not adversely afiect the octane quality of the gasolines to which they are added. In accordance with the invention, it has now been discovered that certain trialhyl phosphorus esters have surprisingly little effect upon the octane ratings of gasolines to which they are added and, when employed in critical concentrations, actually effect an increase rather than a decrease in octane quality. The invention thus provides phosphorus additives which possess the relatively low boiling point and high gasoline-solubility advantages of alkyl phosphorus esters proposed for use in modifying combustion chamber deposits in the past but which are free of the octane quality degradation disadvantage which has prevented the commercial utilization of alkyl esters of phosphorus as gasoline additives heretofore.

The alkyl phosphorus esters which are employed as auxiliary scavenger agents in gasolines containing tetraethyl lead or a similar alkyl lead compound and halohydrocarbon scavenger agents in accordange with the invention are trialkyl esters of phosphoric and phosphorus acids having alkyl groups derived from mixed octyl alcohols prepared by the 0X0 process. The additive compounds of the invention are thus tri-(C -oxo) phosphates and tri-(C -oxo) phosphites. It has been found that these particular mixed esters have critical properties which permit their use as gasoline scavenger agents Without serious octane degradation of the fuel. Other closely related trialkyl esters of phosphorus, such as the tri-(n-octyl) and the tridecyl phosphates and phosphites, do not possess these unique properties and therefore are unsatisfactory for purposes of the invention.

The tri-(C -oxo) phosphates and phosphites employed as auxiliary scavengers for leaded gasolines in accordzssaass Y ance with the invention may be prepared by the reaction of a phosphorus halide or a phosphorus oxy-halide with C oxo-alcohol. Use of the phosphorus halides results in the production of tri-(C -oxo) phosphites; whereas the reaction of a phosphorus oxy-halide and the alcohol produces a phosphate ester. In carrying out such reactions, the reactants may be mixed at temperatures of from about --l C. to about 150 C., preferably about 0 C. to about 20 C., under conditions to main tain the phosphorus constituent in liquid phase. The reactants are preferably combined in the presence of an inert solvent such as benzene, xylene, pyridine or the like. The reaction period will normally be from about 2 to about 8 hours, at the end of which the reaction mixture is filtered to remove any solids present and the esters formed are recovered. The ester product may be water-washed, distilled, and otherwise purified by methods familiar to those skilled in the art. A more detailed description of the esters and their preparation may be found in US. Patent 2,658,871.

The C -oXo alcohols from which the tri-(C -oxo) esters of phosphorus are prepared as described above are produced by the oxonation and subsequent hydrogenation of C copolymers of propylene and butene. The copolymers are normally derived from a refinery gas stream containing propylene and mixed normal and isobutylenes and hence consist of a mixture of isomers. The alcohol produced from this mixture of isomers similarly consists of a series of isomeric compounds. A typical analysis of C -oxo alcohol is as follows:

Alcohol Constituent Weight Percent CH: CH: CHz-H-CHrHCHr-CHr-OH 29 CH: CH;

CH3CHCHCHz-CHr-CHr-OH 25 CH: CH;

CH:-CH7CHCHCHz-CH:OH 17 CHI CHa-CHrflH-CHz-CHrCHr-CHr-OH CH: 16 CHz-CHz-CHz-ff-H-GHz-CHz-CHg-OH H: CHsCHz-CHCHr-CHiCHaOH 2. 3

CH1 CH;(iJ-CHz-CH:CH2CH2OH 1.4

%) alkanols unidentified for structure g Total 100.0

The oxo process for producing mixed alcohols is well known to those skilled in the art.

The gasolines in which the tri-(C -oxo) esters of acids of phosphorus are employed in accordance with the invention are conventional leaded gasolines such as those marketed commercially for use in internal combustion engines. Such gasolines are broadly classified as either motor gasolines or as aviation gasolines. Motor gasolines are defined by ASTM Specification D-439-5 6T and are classified as Type A, Type B of Type C, depending upon the service for which the fuel is intended. Normally motor gasolines boil between about 80 F. and about 450 F. and have octane numbers ranging from about 83 on the Research scale to about 105 or higher. Aviation gasolines have properties similar to those of motor gasoline but in general have narrower. boiling 4 ranges and somewhat more rigid specifications. Specifications for aviation gasolines are set forth in Military Specification MIL-F-5572.

The concentration of tetraethyl lead, tetramethyl lead, or similar tetraalkyl lead anti-knock agent in the gasolines with which the invention is concerned may range from about 2.0 to about 4.6 cc. per gallon. The gasolines to which the invention relates also contain, in addition to the lead anti-knock agents, halohydrocarbon scavenger agents boiling in the range between about 50 C. and about 250 C. Suitable halohydrocarbon compounds for use as scavenger agents include alkyl halides such as chloro-bromo methane, tetrabromo acetylene, t'richloro ethylene, ethylene dichloride and ethylene dibromide; alicyclic halogenated hydrocarbons such as chlorocyclopentane and trichlorocyclopentane; aromatic halogenated hydrocarbons such as chloro benzene, dibromo benzene, dibromo toluene; and mixtures of such halogenated hydrocarbon compounds. All of the above halohydrocarbons are not equally effective for use as lead scavengers in gasolines. Ethylene dichloride, ethylene dibromide and mixtures thereof are particularly effective because of their volatility properties and chemical stability and are therefore preferred scavenger agents for use in accordance with the invention.

Halohydrocarbon scavengers are employed in the gasolines of the invention in amounts ranging from about 0.8 to about 3.0 theories, based on the lead content of the gasoline. Scavenger concentrations of from about 1.5 to about 2.0 theories are preferred. The expression of scavenger content in terms of theories is conventional practice and will be familiar to those skilled in the art. One theory is the amount of scavenger which is stoichiometrically equivalent to the lead in the gasoline. A theory of hydrocarbon scavenger is thus the amount of scavenger required to react stoichiometrically with a given amount of lead anti-knock agent so that all of the lead and all of the halogen atoms react to form lead halides.

The amount of tri-(C -oxo) phosphate employed in the gasolines of the invention may also be expressed in terms of theories. One theory of the phosphorus ester is the amount of the ester which will react stoichiometrically with all of the lead atoms present to form Pb (PO The tI'i(Cg'0XO) phosphates and phosphites are incorporated into the leaded gasolines of the invention in concentrations ranging from about 0.05 theory to about 1.0 theory, based on the lead content of the fuel. Concentrations between about 0.2 theory and about 0.8 theory are preferred. Concentrations of from about 0.3 to about 0.5 theory result in an actual increase in the octane quality of the gasoline and therefore concentrations in this range are particularly advantageous. The total theories of phosphorus, chlorine, and bromine in the gasoline may range from about 0.85 to about 4.0 theories but will preferably fall between about 1.8 and about 2.6 theories. The theories of halohydrocarbon present in the gasolines of the invention and the theories of tri-(C -oxo) phosphate or phosphite employed should be such that their ratio falls between about 3 to 2 and about 32 to 1. From about 3 to about 10 theories of halohydrocarbon per theory of tri-(C -oxo) phosphate or phosphite are particularly effective.

The tI'l-(Cg-OXO) phosphates and phosphites may be employed in leaded gasolines in accordance with the invention in conjunction with a variety of other additives in addition to the halohydrocarbon scavenger agents employed in such gasolines. Such additives include, for example, solvent oils, corrosion inhibitors, gum inhibitors, anti-icing agents, dyes, dye stabilizers and similar additive materials.

The tri-(C -oxo) phosphates and phosphites are soluble in gasolines and may, therefore, be added directly to leaded fuels in order to achieve the benefits of the invention. In many cases, however, it will be preferred to combine the phosphorus esters with tetraethyl lead,

ditive agents such as those described in the preceding paragraph. A typical concentrate containing tetraethyl lead and the additive materials of the invention may have the following composition:

' Wt. percent Tetraethyl lead 4853 Tri(C -oxo) phosphate 22-14 Ethylene dibrornide 14-16 Ethylene dichloride 14-17 Gum inhibitor, rust inhibitor, dye stabilizer, etc..- 2-0 EXAMPLE 1 In order to demonstrate the elfectiveness of tri-(C oxo) phosphorus esters for reducing the adverse effects of combustion chamber deposits in gasoline engines, tests were carried out in which 2 late model Chevrolet automobiles were operated upon a premium quality gasoline containing 3 cc. of tetraethyl lead per gallon and 1.5 theories of a scavenger agent consisting of 1.0 theory of ethylene dichloride and 0.5 theory of ethylene dibromide. Typical inspections of the gasoline used in these tests were as follows:

A.S.T.M. distillation D-86:

Initial boiling point, F. 104 boiling point, F. 147 50% boiling point, F 223 90% boiling point, F 275 Final boiling point, F. 325 Reid vapor pressure 7.2 A.P.I. gravity 59.2 General Motors Gum 0.6 Research Octane Number 103.5 Motor Octane Number 94.1

The cars employed in the tests were operated upon the above fuel during 5000 miles of driving under average city-suburban conditions. The engines had been cleaned prior to the tests and were initially free of deposits which might give rise to surface ignition. During the tests, the cars were checked at 1000 mile intervals to determine whether surface ignition was taking place. Each check after deposits had accumulated during the initial 1000 miles showed the occurrence of severe surface ignition. At the end of the 5000 mile test, the incidence of spark plug misfiring was determined by means of an electronic misfire counter. It was found that the engines were misfiring an average of 35% of the time.

Similar tests were then carried out using samples of the same gasoline to which had been added 0.4 theory of tri-(C -oxo) phosphate. Clean engines were again used. The occurrence of surface ignition during 5000 miles of driving under conditions similar to those encountered in the tests of the base gasoline and spark plug misfiring at the end of the 5000 mile period were again determined. It was found that surface ignition could be detected in only 37% of the checks after the initial 1000 miles and that the average rate of spark plug misfiring was only 3.4%.

The results of these tests are summarized in Table l below.

Table I EFFECT OF TRI-(OB-OXO) PHOSPHATE UPON SURFACE IGNITION AND SPARK PLUG MISFIRING IN LATE MODEL CHEVROLETS Spark Plug Occurrence Misfiring of Surface Fuel After 5,000 Ignition Miles Driv- During 5,000 mg, Percent Miles Driving, Percent Base Gasoline 35 Base Gasoline-l-O 4 T of Tri-(C -oxo) Phosphate 3. 4 37 1 Average values obtained with 2 different cars.

The above data demonstrate that tri-(C -oxo) phosphate is an eifective additive for reducing surface ignition, spark plug misfiring and related difliculties in engines operated upon gasolines containing lead anti-knock agents and halohydrocarbon scavengers.

EXAMPLE 2 The efiect of tri-(C -oxo) phosphorus esters upon the octane number of gasolines is shown by results obtained in a series of tests wherein gasoline samples containing 1.0 theory of various trialkyl phosphites having alkyl groups of from 1 to 10 carbon atoms were matched against primary reference fuels to determine their octane ratings. The base gasoline employed in these tests was a commercial premium grade gasoline containing 3.0 theories of tetraethyl lead, 1.0 theory of ethylene dichloride and 0.5 theory of ethylene dibromide. The base fuel had a Research Octane Number of 87.1 and a motor octane number of 84.4. The method used to determine octane ratings is described in Coordinating Research Council Method CROF-l-545. The results of these tests are shown in the following table:

Table II EFFECT OF ALKYL SUBSTITUENIS IN TRIALKYL ES TERS OF PHOSPHORUS UPON RESEARCH OOTANE NUMBER OF LEADED GASOLINE A Research Research ctane Additive in Fuel Octane Number Number Due to Additive None 87.1 None 1.0 T. Trimet-hyl Ph0sph1te 85. 6 1. 5 1.0 '1. Triethyl Phosphite 84. 4 2. 7 1.0 T. Tr1(n-propyl) Phosphite 85. 5 1.6 1.0 'I. Tr1(Is0propyl) Phosph1te 83. 6 -3. 5 1.0 T. Tr1(n-Butyl) Phosphrte 85.5 1.6 1.0 T. Tri(Isobutyl) Phosphite 85. 5 -1.6 1.0 T. Tri(Sec.-Butyl) Ph0sphite 84. 2 -2. 9 1.0 T. Tri(Tert.-Butyl) Phosphitem- 78.1 1 9 1.0 T. Tri(n-Hexyl) Ph0sphite 86.4 -0.7 1.0 T. Tri(2-Ethyl Butyl) Phosphite 85.5 l.6 1.0 '1. Tri(l,3-Dimethyl Butyl) Phosphite 83. 5 -3. 6 1.0 T. Tri(l-Methyl Pentyl) Phosphite a 83.1 4.0 1.0 T. Tri(n-0cty1) Phosphite 86. 0 -1. 1 1.0 'I. Tri(2-Ethyl Hexyl) Phosphite- 85. 5 1. 6 1.0 T. Tri(Cr-Oxo) Phosphite 86. 7 0.4 1.0 T. Tri(n-Decyl) Phosphite 85. 8 -1. 3

1 Estimated Tri(Tert.-Butyl) phosphite ause of steric hindrance.

FIGURE I in the drawing sets forth graphically the results obtained in the above tests. As can be seen from the data in the table and from FIGURE I, the Research Octane Number debit which results from the use of tri- (C -oxo) phosphite in gasolines is surprisingly lower than that of any of the other trialkyl phosphites. The normal alkyl esters exhibited octane debits ranging from 0.7 Research Octane Number in the case of tri-(n-hexyl) phosphite to 2.7 Research Octane Numbers in the case of triethyl phosphite. The curve in FIGURE I represents the values obtained for the straight chain esters. The branched esters in general produced considerably cannot be synthesized be higher octane debits than did the straight chain compounds. The tri-(l-methyl pentyl) phosphite, for ex-' ample, showed an octane debit of 4 Research Octane Numbers; whereas the debit of the tri-(n-hexyl) phosphite was 0.7 Research Octane Numbers. The octane debit of tri-(Z-ethyl-hexyl) phosphite was considerably higher than that of the tri-(n-octyl) phosphite. The use of tri-(C -oxo) phosphite, however, resulted in an octane debit which was less than half that of the tri-(n-octyl) phosphite and which was much lower than that obtained with any of the other esters.

The tests reported above were carried out upon the basis of the Research Octane Number debits caused by trialkyl phosphites because the phosphites uniformly give slightly larger debits than do the corresponding phosphates. Similar tests carried out with the phosphates and tests based upon Motor Octane Number have shown results similar to those set forth above and have confirmed the fact that tri-(C -oxo) esters of phosphorus etfect surprisingly lower octane debits in leaded gasolines than do other trialkyl phosphorus esters. As pointed out heretofore, this unexpectedly low octane debit makes the tri-(C -oxo) phosphates and phosphites much more attractive for use as combustion chamber deposit modifiers in leaded gasolines than other closely related compounds.

EXAMPLE 3 Further tests were carried out to determine the effect of variations in tri-(C -xo) phosphate concentrations upon gasoline octane quality. Samples of a commercial leaded gasoline containing 0.2, 0.4 and 1.0 theory of tri-(C -oxo) phosphate were subjected to Uniontown tests to determine their Road Octane Numbers. The base fuel employed contained 3 cc. of tetraethyl lead per gallon, 1.0 theory of ethylene dichloride, and 0.5 theory of ethylene dibromide. It had a Research Octane Number of 97.5 and a Motor Octane Number of 89. The tests were carried out using a 1957 Oldsmobile having a compression ratio of 9.5 to 1. The data obtained in these tests are shown in FIGURE II of the drawing and in the following table.

Table III EFFECT OF TRI'(CEOX0 PHOSPHATE CONCENTRATION Average values based on two separate ratings carried out; on two separate days.

From the above table and FIGURE II in the drawing ing it can be seen that within a critical range extending between about 0.3 theory and about 0.5 theory concentrations, tri-(C -oxo) phosphate produced an octane bonus rather than the expected debit. The existence of such a bonus has been corroborated by tests carried out with base fuels other than that employed in obtaining the data set forth above and with engines other than the 1957 Oldsmobile engine employed in the above tests. This bonus in octane number renders the use of from 0.3 to 0.5 theories of tri-(C -oxo) phosphate and tri-(C -oxo) phosphite as a combination chamber deposit modifier in leaded gasolines particularly attractive. Because the tri-(C -oxo) esters give unexpectedly lower octane debits than other trialkyl esters at concentrations outside the 0.3 to 0.5 theory range, however, they are superior to trialkyl esters suggested by the prior art regardless of the concentration in which they are used.

What is claimed is:

1. A gasoline containing from about 2.0 to about 4.6 cc. of tetraethyl lead per gallon, from about 1.5 to about 2.0 theories of halogen as a halohydrocarbon scavenger agent boiling between about 50 C. and about 250 C. and from about 0.3 to about 0.5 theory of phosphorus as tI'l-(CyOXO) phosphate as a combustion chamber deposit modifier.

2. A gasoline of between about 83 and about Research Octane Number containing from about 2.0 to about 4.6 cc. of tetraethyl lead per gallon, from about 1.5 to about 2.0 theories of halogen as a mixture of ethylene dichloride and ethylene dibromide and between about 0.3 and about 0.5 theory of phosphorus as tri-(C -oxo) phosphate as a combustion chamber deposit modifier.

3. A gasoline of between about 83 and about 105 Research Octane Number containing about 3 cc. of tetraethyl lead per gallon, about 1.5 theories of chlorine as ethylene dichloride, about 0.5 theory of bromine as ethylene dibromide and about 0.4 theory of phosphorus as tI'i-(Cg-OXO) phosphate as a combustion chamber deposit modifier.

References Cited in the file of this patent UNITED STATES PATENTS 2,642,452 Mikeska et al. June 16, 1952 2,860,958 Gilbert Nov. 18, 1958 2,911,431 Orlofi et al. Nov. 3, 1959 OTHER REFERENCES Ind. and Eng. Chem, March 1948, vol. 40, No. 3, Suitability of Gasolines as Fuel, pp. 405 to 411, by James at al.

Ind. and Eng. Chem, March 1951, vol. 43, No. 3, pp. 663 to 670, Antiknock Antagonists, by Livingston.

Claims (1)

1. A GASOLINE CONTAINING FROM ABOUT 2.0 TO ABOUT 4.6 CC. OF TETRAETHYL LEAD PER GALLON, FROM ABOUT 1.5 TO ABOUT 2.0 THEORIES OF HALOGEN AS A HALOHYDROCARBON SCAVENGER AGENT BOILING BETWEEN ABOUT 50*C. AND ABOUT 250*C.

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