US3707362A - Method and composition for optimizing air-fuel ratio distribution in internal combustion engines - Google Patents

Abstract

A TERTIARY AMINE HAVING ONE LONG STRAIGHT CHAIN ALIPHATIC GROUP AND TWO SHORT CHAIN ALKY GROUPS, OR A MIXTURE OF SUCH AN AMINE WITH A LONG STRAIGHT CHAIN PRIMARY AMINE, WHEN ADDED IN MINOR PROPORTION TO A GASOLINE, WILL IMPROVE THE DISTRIBUTION OF THE AIR-FUEL MIXTURE IN THE INTAKE MANIFOLD OF A MULTICYLINDER GASOLINE ENGINE, RUN WITH THE RESULTING BLEND, THEREBY INCREASING OPERATING EFFICIENCY. ADDITION OF THE MIXED AMINES TO A GASOLINE ALSO IMPROVES FUEL ECONOMY AS EVIDENCE BY BETTER GASOLINE MILEAGE. THE TERTIARY AMINE AIDS THE SOLUBILITY OF THE PRIMARY AMINE IN AN ADDITIVE CONCENTRATE USED FOR BLENDING.

Description

United States Patent O Int. Cl. C101 1/22 US. C]. 44-72 14 Claims ABSTRACT OF THE DISCLOSURE A tertiary amine having one long straight chain aliphatic group and two short chain alkyl groups, or a mixture of such an amine with a long straight chain primary amine, when added in minor proportion to a gasoline, will improve the distribution of the air-fuel mixture in the intake manifold of a multicylinder gasoline engine, run with the resulting blend, thereby increasing operating efiiciency. Addition of the mixed amines to a gasoline also improves fuel economy as evidence by better gasoline mileage. The tertiary amine aids the solubility of the primary amine in an additive concentrate used for blending.

BACKGROUND OF THE INVENTION This invention concerns an improved motor fuel composition and an improved method of operating an internal combustion engine. More particularly, the invention concerns incorporating into a motor fuel, such as gasoline, an additive or combination of additives that will improve the geometric and time distribution of the fuel in the induction system of an aspirated multicylinder internal combustion engine.

In operating a gasoline engine, it is necessary to supply to the cylinders a mixture of gasoline and air in proper proportions. In most instances, this is accomplished by the use of a carburetor wherein the fuel is aspirated into a stream of moving air. In an aspirated multicylinder engine'the mixture of air and fuel is distributed to the various cylinders through an intake manifold. One problem that arises in such a system is that the air/fuel ratio tends to vary from cylinder to cylinder, some cylinders receiving a relatively rich mixture and other a relatively lean mixture. Similarly, variations in air/fuel ratio occur in each cylinder with respect to time. Both of these effects result in reduced operating efiiciency, which shows up in at least two ways, one being a loss in fuel economy and another being uneven and reduced power.

Gasolines used as motor fuels comprise a mixture of hydrocarbons of various boiling points. Thus a gasoline can have an initial boiling point in the range of about 70 to 135 F. and a final boiling point in the range of about 250 to 450 F. The mixture of gasoline and air that leaves the carburetor and passes to the various cylinders through the intake manifold tends to deposit some of the higher boiling fractions in the form of a liquid film on the walls of the intake manifold. This liquid film is the main factor in poor fuel distribution in the engine. Accordingly, it is desirable for improved efficiency to have the gasoline as a vapor or spray in the air-fuel mixture.

DESCRIPTION OF THE INVENTION In accordance with the present invention, it has been found that the distribution of the air-fuel mixture to the various cylinders of an aspirated multicylinder internal combustion engine can be improved by incorporating in the fuel fed to that engine a minor amount of one or more aliphatic amines having a long straight chain of from 12 ice to 20 carbon atoms, preferably 16 to 18 carbon atoms. One such amine that is used will be a tertiary amine having one such long straight aliphatic chain and two short alkyl chains of no more than three carbon atoms, i.e. an amine of the formula:

In the above formula R is a straight chain aliphatic hydrocarbon radical of from 12 to 20 carbon atoms, preferably C to C and R and R" are C, to C alkyl, e.g. propyl or isopropyl, methyl, or ethyl, preferably C to C and most preferably methyl.

Particularly advantageous is a mixtuer of a tertiary amine as above described with a primary amine, i.e. one wherein in the above formula R is a straight chain aliphatic group of 12 to 20 carbon atoms, preferably C to C and R and R" are hydrogen.

While the straight chain hydrocarbyl amines of this invention can be either saturated or unsaturated aliphatic tertiary amines or mixed tertiary and primary amines, the saturated amines are preferred.

Representative straight chain aliphatic primary amines useful in this invention include normal octadecyl amine, normal octadecenyl amine, normal dodecyl amine and normal hexadecyl amine. A particularly useful commercial mixture of primary amines is hydrogenated tallow amine wherein the aliphatic groups are principally C and C Tertiary amines used in this invention include, for example, dimethyl octadecyl amine, diethyl dodecyl amine, methyl ethyl .tetradecyl amine, and diisopropyl hexadecyl amine. A particularly useful commercial mixture of tertiary amines is dimethyl hydrogenated tallow amine, wherein the long straight chain hydrocarbon groups of the tallow moiety are principally C and C It is known that other amino compounds have been proposed for addition to gasoline. For example, U.S. Pat. 3,399,982 discloses tertiary alkyl primary amines such as 2- methyl-Z-aminohexadecane and 2-methyl-2-aminooctaeicosane. Amines of this type that were subjected to testing gave little or no improvement in air/fuel ratio distribution and hence were not considered to be useful in the present invention. -It is also known to incorporate various aromatic amines and cycloaliphatic amines into gasoline to be used as antioxidants. Such amines include phenyl alpha-naphthylamine, cyclohexylamine, n-butyl-p-aminophenol, xylidine and alkylated p-phenylene diamines. Amino compounds of this type do not have the proper surface activity to make them useful in the present invention. Straight chain aliphatic amines have been suggested as anti-icing agents for gasolines when added in concentrations of about 0.2 to 0.5 percent by volume (see US. Pat. 2,706,677). Such concentrations of the amines are much greater than the concentrations used in the present invention.

US. Pat. 3,011,879 teaches that straight chain aliphatic primary amines impart carburetor detergency properties to a gasoline when added thereto in concentrations within the range used in the present invention. There is no teaching in that patent, however, that a tertiary amine or a combination of a tertiary amine with a primary amine will improve air-fuel mixture distribution or fuel economy when such amine or amine mixture is added to a gasoline.

It has been demonstrated that the amines added to gasoline in accordance with the present invention act in some way on the walls of the intake manifold of the gasoline engine to render them less subject to wetting by the gasoline and thereby reduce the tendency for deposition of the liquid film referred to above and increase the proportion entrained in the air. This reduces the variation from cylinder to cylinder in the air/ fuel ratio of the mixreduced. In general, the result is improved smoothnessof operaton, reduced tendency for hesitation on acceleration, reduced tendency for surging at constant road speeds, and improved gasoline mileage. There is also generally a reduction in the emission of carbon monoxide and unburned hydrocarbons, thereby reducing air pollution.

The aliphatic amines of this invention will be used in gasoline in a total concentration within the range of from about to about 80 pounds per thousand barrels of gasoline, a barrel containing 42 U.S. gallons. The preferred concentration range is from about to about 40 pounds per thousand barrels. A concentration range of from 10 to 40 pounds per thousand barrels is roughly equal to a weight percent concentration of from about 0.004 to about 0.016 weight percent.

While this invention can be practiced using only one or more of the tertiary amines, it is preferred to employ a mixture of primary and tertiary amines of the types described. In such mixtures the proportions of amines can range from about 75 percent primary and 25 percent tertiary up to substantially all tertiary and no primary amine. Preferably, the amonut of tertiary amine will be at least equal the amount of primary amine in the mixture. Usually there will be from about 1 to about 5 parts per weight of tertiary for each part of primary amine. A particularly useful combination comprises three parts of tertiary for each part of primary amine.

The tertiary amines of this invention improve the solubility of long straight chain aliphatic primary amines, especially hydrogenated tallow amine. This is a decided advantage, since the preferred primary amines have limited solubility in all suitable solvents, particularly at low temperatures. This is especially helpful when preparing an additive concentrate for later blending into gasoline. Thus, a blend of 5 weight percent of hydrogenated tallow amine, weight percent of dimethyl hydrogenated tallow amine and 80 weight percent of a mixture of 3 volumes of xylene and 1 volume of isopropanol has more solubility stability than a blend of 5 weight per cent of hydrogenated tallow amine and 95 weight percent of the 3 to 1 mixture of xylene and isopropanol, particularly at low temperatures.

Thus, an additive concentrate can be prepared containing from 5 to 10 weight percent of primary amine or mixed primary amines and from 10 to 30 percent of tertiary amine or mixed tertiary amines along with a solvent for the amines. The preferred solvent in the concentrate comprises a mixture of an aromatic hydrocarbon and a polar solvent, most usually about 1 to 4 volumes of aromatic hydrocarbon being used per volume of polar solvent. The aromatic solvents include ortho or meta xylene, mixed xylenes, toluene, ethylbenzne, etc. The polar solvents include C to C aliphatic alcohols, glycols of 6 to 8 carbon atoms such as 2-methyl-2,4-pentane diol (known as hexylene glycol), 2-methyl-1,3-pentane diol, 2-ethyl- 1,3-hexane di-ol, etc., and glycol ethers of from 3 to 8 carbon atoms including, Z-methoxyethanol (methyl Cellosolve), 2-butoxy ethanol (butyl Cellosolve), 3-ethoxy propanol, etc. Preferably 1 to 2 volumes of the polar solvent are used for each 3 volumes of aromatic hydrocarbon solvent. The additive concentrate can also contain other additives that are commonly blended into gasoline, e.g. antioxidants, dispersants, rust inhibitors, etc.

It is also useful to include in the concentrate from about 0.1 to 2 weight percent of a wax alkylated aromatic hydrocarbon to overcome any tendency for crystal formation to occur with any components of the concentrate. The preparation of suitable condensation products of chlorinated parafiin wax and aromatic compounds such as naphthalene is described in US. Pats. 1,815,022; 2,015,748; 2,174,246 and 2,297,292.

The gasolines in which the additives of this invention are employed are conventional petroleum distillate fuels boiling in the gasoline range and intended for internal combustion engines, preferably spark ignition engines. Gasoline is defined as a mixture of liquid hydrocarbons having an initial boiling point in the range of about 70 to F. and a final boiling point in the range of about 250 to 450 F. Gasolines are supplied in a number of different grades, depending upon the type of service for which they are intended. The additives of the invention are particularly useful in motor and aviation gasolines. Mot-or gasolines include those defined by ASTM Specification D-439-58T, Types A, B and C. They are composed of a mixture of various types of hydrocarbons, including aromatics, olefins, paraffins, isoparaflins, naphthenes, and' occasionally, diolefins. Not all of these types of hydrocarbons will necessarily be present in a particular gasoline. These fuels are derived from petroleum crude oil by refining processes such as fractional distillation, catalytic cracking, hydroforming, alkylation, isomerization, polymerization and solvent extraction, etc. Motor gasolines normally have boiling ranges between about 70 F. and about 450 F., while aviation gasolines have narrower boiling ranges of between 100 F. and 330 F. The vapor pressures of gasoline as determined by ASTM Method D-323 vary between about 5 and about 18 p.s.i. at 100 F. The properties of aviation gasolines are set forth in US. Military Specification MIL-F-5572 and ASTM Specification D-9 1 0-5 7T.

The additives employed in accordance with this invention may be used in gasolines with other additive agents conventionally used in such fuels. For example, it is common practice to employ from about 0.5 to about 7.0 cc./ gal. of alkyl lead anti-knock agents, such as tetraethyl lead, tetramethyl lead, dimethyl diethyl lead, or a similar alkyl lead antiknock agent or olefinic lead antiknock agent such as tetravinyl lead, triethyl vinyl lead, and the like, or a combination thereof, in motor gasolines and in aviation gasolines, along with the usual scavenging agents such as ethylene dichloride or ethylene dibromide. The effectiveness of the amines of this invention does not require the presence of such antiknock agents, however. Other additives conventionally employed in gasolines may be included, such as corrosion inhibitors, rust inhibitors,

i antioxidants, antistatic agents, solvent oils, lead octane appreciat-ors, e.g., t-butyl acetate, auxiliary scavengers like tri- [i-chloroethyl phosphate, dyes, anti-icing agents, e.g. isopropanol, hexylene glycol, and the like. There may also be included certain oil-soluble dispersants and detergents to provide significant improvement in overall engine cleanliness. This is taught, for example, by Calvino et al. in US. Pat. 3,223,495.

The nature of this invention and the advantages accruing from the practice thereof will be better understood when reference is made to the following examples, which include a preferred embodiment.

EXAMPLE 1 (INCLUDING COMPARATIVE TESTS) Gasoline blends were prepared using as the base a 100 octane rating gasoline that had the inspections shown in Table I:

TABLE I Base gasoline inspections ASTM distillation, Method D-86:

Initial boiling point, F 90 20% overhead, F 144 30% overhead, F 50% overhead, F 214 90% overhead, F 308 Final boiling point, F 380 TABLE IContinued FIA Analysis:

Vol. percent- 1 Fluorescent Indicator Absorption Analysis; ASTM 1319.

The blends were prepared by adding, by simple mixing, normal octadecyl amine at the concentration of 40 pounds per thousand barrels to one portion of the base fuel, and dimethyl normal hexadecyl amine to another portion of the base fuel at the same concentration.

The base fuel and each blend were run separately in a 1967, 6-cylinder, 175 cu. inch Valiant engine equipped with exhaust emission controls meeting the requirements of the State of California for 1967. The Valiant car was operated on a Clayton dynamometer with acceleration weights equivalent to 4,000 pounds. In each test the engine was run at idle speed and at 50 miles an hour and the air/fuel ratio reaching each cylinder was determined. In order to accomplish this, sampling lines were extended into the individual exhaust valve ports of the engine, so as to permit the analysis of the combustion products from each of the six cylinders separately. The exhaust gas was filtered and cooled prior to analysis to remove solid particles and most of the water produced by combustion of the gasoline. The exhaust gas was then analyzed for hydrocarbons, carbon monoxide, carbon dioxide, nitrogen oxide and oxygen. The car was held at a constant engine r.p.m. and dynamometer speed for the period of each of the measurements, approximately 15 minutes at each speed condition. Air/fuel ratios were calculated by a material balance of the exhaust gas, using well-known procedures (see Lamont 'Eltinge, Fuel/Air Ratio and Distribution From Exhaust Gas Compositions, SAE Paper 680114, January 1968; and R. S. Spindt, Air/Fuel Ratios From Exhaust Gas Analysis, SAE Paper 650507, May 1965). The spread between the highest and lowest calculated air/fuel ratio at each of the testing speeds for each of the fuels is given in the follwoing Table II. The air/ fuel ratios were in the range of 13/1 to 15/1 at idle and in the range of 14.5/1 to 16.5/1 at 50 miles per hour.

TABLE II.SPREAD OF AIR/FUEL RATIOS Base iuel Base iuel plus dimethyl Base plus n-oetan-hexadeeyl Velocity iuel decyl amine amine Idle 1. 95 0. 78 1. 09 50 m.p.h 1. 90 1. 33 '1. 32

It will be noted that the amines effectively improved the air-fuel distribution ratio.

EXAMPLE 2 (COMPARATIVE 'I'ESTS) TABLE Ill-PERCENT REDUCTION IN AIR/FUEL RATIO SPREAD Percent reduction at- Amlne Idle 50 m.p.h.

Dicoco 12 Tallo 27 20 Dimethyl n-hexadecyl 36 27 Dimethyl n-oetadeeyl 18 15 Hydrogenated tallow 30 25 Dicoco amine is a mixture of secondary amines derived from coconut oil. The major component is a secondary amine having two aliphatic groups of 12 carbon atoms each. Tallow amine is a mixture of saturated and unsaturated primary aliphatic amines, predominantly C and C amines. Hydrogenation of tallow amine removes substantially all the unsaturation.

EXAMPLE 3 (FUEL ECONOMY TESTS) The effect of tallow amine and of a mixture of hydrogenated tallow amine and dimethyl n-octadecyl amine upon fuel economy was determined in the following manner. Standard commercial automobiles were used and each was run through the same preselected driving sequence on a mileage accumulation dynamometer. The latter is described in US. Pat. 3,050,994. Each car was first run with the base fuel described in Table I for a period of 64 hours and the fuel economy was determined. Each car was then run through the same sequence for the same period of time using the base fuel of Table I to which had been added tallow amine at a concentration level of 40 pounds per thousand barrels and the fuel economy was again observed. At the end of the 64 hour run, which was equivalent to 1900 miles of typical suburban driving, wherein the top speed reached was 50 miles per hour coupled with periods of lower speed driving and idling, it was found that there was either no diiference in fuel economy or that fuel economy was worse with the amine blend than with the base fuel. The results are shown in the following Table IV:

TABLE IV.-FUEL ECONOMY DETERMINATIONS Miles per gallon Fuel plus Base fuel amine 1968 Chevrolet 17. 2 16. 8 1969 Ford 17. 5 17. 0 1968 Plymouth 17. 8 17. 8

Using the same procedure as described above, a second set of automobiles were run with the base fuel and thereafter with the base fuel into which had been blended hydrogenated tallow amine at the rate of 5 pounds per thousand barrels of gasoline plus dimethyl n-octadecyl amine at the rate of 15 pounds per thousand barrels. With this mixture of amines there was an improvement in fuel economy in each case as shown in Table V which follows.

TABLE V.-FUEL ECONOMY IMPROVEMENT WITH MIXED lAZMINElS Miles per gallon Fuel plus Base fuel amines 1970 Chevrolet 16. 2 16. 5 1969 Chrysler-.. 16. 7 17. 6 1969 Ford.. 13. 14. 3 1969 Mercury 15. 0 16. 1 1969 Pontiac. 15. 1 15. 9

EXAMPLE 4 (ADDITIVE CONOENTRATE) EXAMPLE 5 (ADDITIVE CONCENTRATE) To parts by weight of the concentrate of Example 4 there is added as a crystallization inhibitor about 0.5 part of a 50 weight percent concentrate, in mineral lubricating oil, of a condensate of chlorinated paraflin wax and naphthalene, e.g. the commercial product known as Parafiow 149.

EXAMPLE 6 As stated earlier, variations in air/fuel ratio in particular cylinders of a multicylinder engine can vary with respect to time. Such variations cause an engine to accelerate as frequently as once per second, even though an attempt is made to hold the vehicle under steady cruise conditions with a fixed position of the throttle. If the variation in air/fuel ratio with time becomes sufiiciently severe, it feels to the automobile driver as if his car is being buffeted by winds. The present invention reduces this phenomenon and gives a significant improvement in steadiness at fixed cruise conditions, as is demonstrated by the following tests. A 1969 Pontiac automobile having a 400 cubic inch displacement engine and an automatic transmission was driven in two opposite directions over a stretch of highway at 50 miles per hour. An electronic tachometer measured the engine r.p.m. during the run, and by means of a suitable electronic circuit the first derivative of this signal was measured. The recorded output was thus the derivative of r.p.m. with respect to time, i.e. d (r.p.m.)/dt, this being a direct measurement of engine acceleration. The car was first operated with the 100 octane base fuel described in Table I. The car was then operated over the same stretch of highway with the same base fuel into which had been blended hydrogenated tallow amine at the rate of 10 pounds per thousand barrels of gasoline plus dimethyl n-octadecyl amine at the rate of 30 pounds per thousand barrels. It was found that the variations in engine acceleration were reduced by a factor of 3 when using the base fuel to which the mixed amines had been added as compared with the base fuel alone. This reduction in acceleration and deceleration of the engine is directly related to reduction in the magnitude of variation of air/fuel ratio with time.

What is claimed is:

1. A gasoline composition comprising a major proportion of gasoline into which has been incorporated from about to about 80 pounds, per thousand barrels of gasoline, of a mixture of aliphatic amines, one of said amines being an aliphatic primary amine having a long straight chain of from 12 to 20 carbon atoms, the second amine being an aliphatic tertiary amine having one long straight chain of from 12 to 20 carbon atoms and two short chain alkyl groups of from 1 to 3 carbon atoms.

2. Composition as defined by claim 1 wherein said tertiary amine constitutes at least 25 weight percent of said mixture.

3. A composition as defined by claim 1 wherein the quantity of said tertiary amine is from about 1 to 5 times the quantity of said primary amine.

4. Composition as defined by claim 1 wherein the amine concentration is from 10 to 40 pounds per thousand barrels of gasoline.

5. Composition as defined by claim 1' wherein the long straight chain in each of said amines is predominantly 16 to 18 carbon atoms in length.

6. A composition as defined by claim 1 wherein said primary amine is hydrogenated tallow amine.

7. Composition as defined by claim 1 wherein said tertiary amine is dimethyl hydrogenated tallow amine.

8. The method of improving the operation of an internal combustion engine which comprises running said engine with the gasoline composition defined by claim 1.

9. A gasoline composition comprising a major proportion of gasoline into which has been incorporated from about 5 to about pounds per thousand barrels of gasoline, of an aliphatic tertiary amine having one long straight chain of from 12 to 20 carbon atoms and two short chain alkyl groups of from 1 to 3 carbon atoms.

10. Composition as defined by claim 9 wherein said amine has a long straight chain of from 16 to 18 carbon atoms.

11. Composition as defined by claim 9 wherein said amine is predominantly dimethyl n-octadecyl amine.

12. The method of improving the operation of an internal combustion engine which comprises running said engine with the gasoline composition defined by claim 9.

13. An additive concentrate for a gasoline composition which comprises from about 5 to 10 weight percent of an aliphatic primary amine having a straight chain aliphatic group of from 12 to 20 carbon atoms, from about 10 to 30 weight percent of an aliphatic tertiary amine having one long straight chain of from 12 to 20 carbon atoms and two alkyl groups of from 1 to 3 carbon atoms, and from 60 to weight percent of a solvent, said solvent comprising a mixture of a liquid aromatic hydrocarbon and a polar solvent.

14. An additive concentrate as defined by claim 13 to which has been added from about 0.1 to about 2 weight percent of a crystallization inhibitor comprising a waxalkylated aromatic hydrocarbon.

References Cited UNITED STATES PATENTS 3,011,879 12/1961 Buckmann et al. 44-72 3,342,570 9/ 1967 Kautsky 44-72 2,945,749 7/ 1960 Andress 44--72 2,758,086 8/1956 Stuart et al 44-72 X 2,793,943 5/1957 Moore 44-72 1,940,445 12/1933 Calcott et al. 44-72 1,815,022 7/1931 Davis 208-12 2,174,246 9/1939 Lieber et a1 252-59 DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner