ORI-inhibited and Deposit-Resistant Motor Fuel Composition

1. Field of the Invention

This invention relates to an ORI-inhibited and deposit-resistant motor fuel composition. More particularly, this invention relates to a motor fuel composition comprising a reaction product obtained by reacting a dibasic acid anhydride, a polyoxyalkylene diamine, and a heterocyclic azole.

2. Information Disclosure Statement

Co-assigned U.S. patent application Ser. No. 302,494, filed Jan. 27, 1989 discloses a haze, oxidation and corrosion-resistant diesel engine lubricant composition comprising a major amount of a hydrocarbon lubricating oil and a minor amount of the reaction product of a dibasic acid anhydride, a polyoxyalkylene diamine, and a heterocyclic azole.

Co-assigned U.S. patent application Ser. No. 302,492, filed Jan. 27, 1989, discloses an ORI-inhibited and deposit-resistant motor fuel composition comprising a minor amount of the reaction product of a dibasic acid anhydride, a polyoxyalkylene monoamine, and an n-alkyl-alkylene diamine.

Co-assigned U.S. patent application Ser. No. 245,591, filed September 19, 1988 discloses an ORI-in1hibited motor fuel composition comprising the reaction product of one or more aliphatic carboxylic acids and a polyoxyalkylene diamine.

Co-assigned U.S. patent application Ser. No. 211,937, filed June 27, 1988, discloses a motor fuel composition comprising the reaction product of (i) a hydrocarbyl-substituted dibasic acid anhydride and (ii) a polyoxyalkylene diamine and an optional polymeric component which is a polyolefin polymer/copolymer, or mixtures thereof, of a C.sub.2 -C.sub.10 hydrocarbon.

Co-assigned U.S. patent application Ser. No. 84,354, filed Aug. 12, 1987 discloses a motor fuel composition comprising (I) the reaction product of the polyoxyalkylene diamine of co-assigned U.S. Pat. No. 4,747,851, a dibasic acid anhydride, and a hydrocarbyl polyamine, and (II) a mixture comprising polyisobutylene ethylene diamine and polyisobutylene in a hydrocarbon solvent.

Co-assigned U.S. patent application Ser. No. 158,424 filed Feb. 19, 1988 discloses a motor fuel composition comprising the reaction pro duct of the polyoxyalkylene diamine of U.S. 4,747,851, a dibasic acid anhydride, hydocarbyl polyamine. An optional additional polymer/copolymer additive with a molecular weight of 500-3500 may also be employed in conjunction with the reaction product additive.

Co-assigned U.S. Pat. No. 4,747,851 discloses a motor fuel composition comprising a polyoxyalkylene diamine compound of the formula: ##STR1## where c has a value from about 5-150, b+d has a value from about 5-150, and a+e has a value from about 2-12, either alone or in combination with a polymer/copolymer additive.

Co-assigned U.S. 4,659,337 discloses the use of the reaction product of maleic anhydride, a polyether polyamine containing oxyethylene and oxypropylene ether moieties, and a hydrocarbyl polyamine in a gasoline motor fuel to reduce engine ORI and provide carburetor detergency.

Co-assigned U.S. Pat. No. 4,659,336 discloses the use of the mixture of: (i) the reaction product of maleic anhydride, a polyether polyamine containing oxyethylene and oxypropylene ether moieties, and a hydrocarbyl polyamine; and (ii) a polyolefin polymer/copolymer as an additive in motor fuel compositions to reduce engine ORI.

U.S. Pat. No. 4,604,103 discloses a motor fuel deposit control additive for use in internal combustion engines which maintains cleanliness of the engine intake system without contributing to combustion chamber deposits or engine ORI. The additive disclosed is a hydrocarbyl polyoxyalkylene polyamine ethane of molecular weight range 300-2500 having the formula ##STR2## where R is a hydrocarbyl radical of from 1 to about 30 carbon atoms; R' is selected from methyl and ethyl; x is an integer from 5 to 30; and R" and R'" are independently selected from hydrogen and --(CH.sub.2 CH.sub.2 NH-)y-H where y is an integer from 0-5.

U.S. Pat. No. 4,198,306 (Lewis) discloses the use of hydrocarbyl poly (oxyalkylene) aminoesters which are monoesters

of a hydrocarbyl-terminated poly (oxyalkylene) alcohol and a monocarboxylic C.sub.2 -C.sub.20 (amino-substituted) alkanoic acid as an ORI-controlling additive in motor fuel compositions.

According to this invention, an ORI-inhibited and deposit-resistant motor fuel composition comprises a mixture of hydrocarbons boiling in the range from about 90.degree.-450.degree. F. and additionally comprises from about 0.0005-5.0 weight percent of the reaction product obtained by reacting, at a temperature of about 30.degree.-200.degree. C.:

(a) 0.5-2.5 moles of a dibasic acidanhydride;

(b) 0.5-1.5 moles of a polyoxyalkylene diamine of the formula ##STR3## where R.sub.1 and R.sub.2 are C.sub.1 -C.sub.12 alkylene groups, q and r are integers having a value of 0 or 1 , c has a value from 2-150, b+d has a value from 2-150, and a+e has a value from 0-12; and

(c) 0.5-1.5 moles of a heterocyclic azole.

Combustion of a hydrocarbon motor fuel in an internal combustion engine generally results in the formation and accumulation of deposits on various parts of the combustion chamber as well as on the fuel intake and exhaust systems of the engine. The presence of deposits in the combustion chamber seriously reduces the operating efficiency of the engine. First, deposit accumulation within the combustion chamber inhibits heat transfer between the chamber and the engine cooling system. This leads to higher temperatures within the combustion chamber, resulting in increases in the end gas temperature of the incoming charge. Consequently, end gas auto-ignition occurs, which causes engine knock. In addition, the accumulation of deposits within the combustion chamber reduces the volume of the combustion zone, causing a higher than design compression ratio in the engine. This, in turn, also results in serious engine knocking. A knocking engine does not effectively utilize the energy of combustion. Moreover, a prolonged period of engine knocking will cause stress fatigue and wear in vital parts of the engine. The above-described phenomenon is characteristic of gasoline powered internal combustion engines. It is usually overcome by employing a higher octane gasoline for powering the engine, and hence has become known as the engine octane requirement increase (ORI) phenomenon. It would therefore be highly advantageous if engine ORI could be substantially reduced or eliminated by preventing or modifying deposit formation in the combustion chambers of the engine.

Another problem common to internal combustion engines relates to the accumulation of deposits in the carburetor which tend to restrict the flow of air through the carburetor at idle and at low speed, resulting in an overrich fuel mixture. This condition also promotes incomplete fuel combustion and leads to rough engine idling and engine stalling. Excessive hydrocarbon and carbon monoxide exhaust emissions are also produced under these conditions. It would therefore be desirable from the standpoint of engine operability and overall air quality to provide a motor fuel composition which minimizes or overcomes the abovedescribed problems.

It is an object of this invention to provide a motor fuel composition which exhibits deposit-resistance and ORI-inhibition when employed in an internal combustion engine.

It is a feature of motor fuel compositions of the instant invention that combustion chamber deposit formation is minimized, with concomitant reduction of engine ORI.

It is an advantage that motor fuel compositions of the instant invention exhibit reduced deposit formation and engine ORI.

The ORI-inhibited and deposit-resistant motor fuel composition of the instant invention comprises a reaction product additive which is obtained by reacting a dibasic acid anhydride, a polyoxyalkylene diamine, and a heterocyclic azole. The dibasic acid anhydride reactant used to prepare the reaction product is preferably selected from the group consisting of maleic anhydride, alpha-methyl maleic anhydride, alpha-ethyl maleic anhydride, and alpha, beta-dimethyl maleic anhydride. The most preferred dibasic acid anhydride for use is maleic anhydride.

The polyoxyalkylene diamine reactant used to prepare the reaction product is a diamine of the formula ##STR4## where R.sub.2 and R.sub.3 are C.sub.1 -C.sub.12 alkylene groups, preferably C.sub.2 -C.sub.6 alkylene group, most preferably a propylene or butylene group, q and r are integers having a value of 0 or 1, preferably with q=1 and r=0, c has a value from about 2-150, preferably 2-50; b d has a value from about 2-150, preferably 2-50; and a +e has a value from about 0-12, preferably 2-8. In the most preferred embodiment, q=1, r=0, R.sub.2 is a butylene group and the polyoxyalkylene diamine reactant is therefore of the formula ##STR5## where c has a value of from 2-150, preferably 2-50, b+d has a value of from 2-150, preferably 2-50 and a+e has a value of 2-12, preferably 2-8.

In another preferred embodiment, q=1, r=0, R2 is a propylene group, a+e has a value of zero, and the polyoxyalkylene diamine reactant is therefore of the formula ##STR6## where c and b+d, respectively, have a value of from 2-150, preferably 2-50. Polyoxyalkylene diamines of the above structure suitable for use include those available from Texaco Chemical Co. under the JEFFAMINE ED-Series trade name. Specific examples of such compounds are set forth below:

The heterocyclic azole reactant used to prepare the reaction product may be any substituted or unsubstituted heterocyclic azole, but preferably is selected from the group consisting of tolyltriazole (hereinafter referred to as TTZ), benzotriazole (hereinafter referred to as BTZ), aminotriazole (hereinafter referred to as ATZ), aminotetrazole (hereinafter referred to as ATTZ), aminomercaptothiadiazole (hereinafter referred to as AMTZ), and benzomercaptothiazole (hereinafter referred to as BMTZ).

If an aminotriazole reactant is employed, it preferably will be a 3-, 4-, or 5-aminotriazole (hereinafter referred to as 3-ATZ, 4-ATZ, or 5-ATZ, respectively), including those bearing inert substituents, typified by hydrocarbon or alkoxy groups, which do not react in the instant invention. The most preferred aminotriazole reactant is 5-ATZ. If an aminotetrazole reactant is employed, it preferably will be a 4- or 5-aminotetrazole (hereinafter referred to as 4-ATTZ or 5-ATTZ, respectively), again including those bearing inert substituents, typified by hydrocarbon or alkoxy groups which do not react in the instant invention. If an aminomercaptothiadiazole reactant is employed, it preferably will be a 5-aminomercaptothiadiazole. The most preferred hydrocarbyl azole reactant for use in the instant invention is 5-ATZ.

The reaction product additive of the instant invention is prepared by first reacting 0.5-2.5 moles, preferably about 2 moles of the abovedescribed dibasic acid anhydride with 0.5-1.5 moles, preferably about 1 mole of the abovedescribed polyoxyalkylene diamine reactant, at a temperature of 30.degree. C.-200.degree. C., preferably 90.degree. C.-150.degree. C. to produce a maleamic acid amide. The reaction is preferably carried out in the presence of a solvent. Suitable solvents include hydrocarbons boiling in the gasoline boiling range of about 30.degree. C. to about 200.degree. C. Generally, this will include saturated and unsaturated hydrocarbons having from about 5 to about 10 carbon atoms. Specific suitable hydrocarbon solvents include tetrahydrofuran, hexane, cyclohexane, benzene, toluene, and mixtures thereof. Xylene is the preferred solvent. The solvent can be present in an amount of up to about 90% by weight of the total reaction mixture. Once the reaction has been completed, the maleamic acid amide may be separated from the solvent using conventional means, or left in admixture with some or all of the solvent.

The maleamic acid amide, either alone or in solution with the abovedescribed solvent, is thereafter reacted with 0.5-1.5 moles, preferably 1 mole of the prescribed heterocyclic azole reactant at a temperature of 50.degree.-100.degree. C. If tetrahydrofuran is employed as the solvent, the preferred temperature is about 80.degree. C.; if xylene is employed as the solvent, the preferred temperature is about 100.degree. C. Once the reaction has been completed, the reaction product may be separated from the solvent using conventional means, or left in admixture with some or all of the solvent.

The following examples illustrate the preferred method of preparing the reaction product of the instant invention. It will be understood that the following examples are -merely illustrative, and are not meant to limit the invention in any way. In the examples, all parts are parts by weight unless otherwise specified.

19.6 parts of maleic anhydride, 692.8 parts of xylene, and 673.2 parts of a polyoxyalkylene diamine were reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce a maleamic acid amide. The polyoxyalkylene diamine (JEFFAMINE ED-2001) may be represented by the formula ##STR7## where c has an approximate value of 40.5, and b+d has an approximate value of 2.5. The maleamic acid amide was filtered and stripped of remaining solvent under vacuum, and identified by IR and elemental analysis. Thereafter, 346.4 parts of a 50% active solution of xylene and the abovedescribed maleamic acid amide and 4.2 parts of 5-ATZ were reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce the final reaction product additive. The reaction product was filtered and stripped of remaining solvent under vacuum, and identified by IR and elemental analysis.

19.6 parts of maleic anhydride, 692.8 parts of xylene, and 673.2 parts of a polyoxyalkylene diamine were reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce a maleamic acid amide. The polyoxyalkylene diamine (JEFFAMINE ED-2001) may be represented by the formula ##STR8## where c has an approximate value of 40.5, and b+d has an approximate value of 2.5. The maleamic acid amide was filtered and stripped of remaining solvent under vacuum, and identified by IR and elemental analysis. Thereafter, 346.4 parts of a 50% active solution of xylene and the abovedescribed maleamic acid amide, 300 parts of tetrahydrofuran and 6 parts of BTZ were reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce the final reaction product additive. The reaction product was filtered and stripped of remaining solvent under vacuum, and identified by IR and elemental analysis.

19.6 parts of maleic anhydride, 692.8 parts of xylene, and 673.2 parts of a polyoxyalkylene diamine were reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce a maleamic acid amide. The polyoxyalkylene diamine (JEFFAMINE ED-2001) may be represented by the formula ##STR9## where c has an approximate value of 40.5, and b+d has an approximate value of 2.5. The maleamic acid amide was filtered and stripped of remaining solvent under vacuum, and identified by IR and elemental analysis. Thereater, 256.3 parts of a 50% active solution of xylene and the abovedescribed maleamic acid amide and 3.3 parts of 5-ATTZ were reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce the final reaction product additive. The reaction product was filtered and stripped of remaining solvent under vacuum, and identified by IR and elemental analysis.

19.6 parts of maleic arhydride, 692.8 parts of xylene, and 673.2 parts of a polyoxyalkylene diamine are reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce a maleamic acid amide. The polyoxyalkylene diamine is of the formula ##STR10## where c has an approximate value of 40.5, b+d has an approximate value of 40.5, and a+e has an approximate value of 2.5. Thereafter, 341.4 parts of a 50% active solution of xylene and the abovedescribed maleamic acid amide and 4.2 parts of 5-ATZ are reacted at a temperature of about 100.degree. C. for approximately 2 hours to produce the final reaction product additive.

The motor fuel composition of the instant invention comprises a major amount of a base motor fuel and 0.0005-5.0 weight percent, preferably 0.001-1.0 weight percent of the abovedescribed reaction product. Preferred base motor fuel compositions are those intended for use in spark ignition internal combustion engines. Such motor fuel compositions, generally referred to as gasoline base stocks, preferably comprise a mixture of hydrocarbons boiling in the gasoline boiling range, preferably from about 90.degree. F. to about 450.degree. F. This base fuel may consist of straight chains or branched chains or paraffins, cycloparaffins, olefins, aromatic hydrocarbons, or mixtures thereof. The base fuel can be derived from, among others, straight run naphtha, polymer gasoline, natural gasoline, or from catalytically cracked or thermally cracked hydrocarbons and catalytically reformed stock. The composition and octane level of the base fuel are not critical and any conventional motor fuel base can be employed in the practice of this invention. An example of a motor fuel composition of the instant invention is set forth in Example V, below.

100 PTB of the reaction product set forth in Example I (i.e. 100 pounds of reaction product per 1000 barrels of gasoline, equivalent to about 0.01 weight percent of reaction product based on the weight of the fuel composition) is blended with a major amount of a base motor fuel (herein designated as Base Fuel A) which is a premium grade gasoline essentially unleaded (less than 0.05 g of tetraethyl lead per gallon), comprising a mixture of hydrocarbons boiling in the gasoline boiling range consisting of about 22% aromatic hydrocarbons, 11% olefinic carbons, and 67% paraffinic hydrocarbons, boiling in the range from about 90.degree. F. to 450.degree. F.

It has been demonstrated that a motor fuel composition comprising a minor amount of the reaction product composition of the instant invention is effective in minimizing and reducing gasoline internal combustion engine deposits. This is an improvement in the fuel performance which may reduce the incidence of engine knock. Several motor fuel compositions of the instant invention were tested by the Combustion Chamber Deposit Screening Test (CCDST). In this test, the deposit-forming tendencies of a gasoline are measured. The amount of deposit formation correlates well with the ORI performance observed in car tests and engine tests. The amount of deposit is compared to a high reference (a standard gasoline known to have a high deposit formation) and a low reference (an unleaded base fuel which is known to have a low deposit formation).

The CCDST determines whether the additive in question is effective as a deposit control additive to prevent ORI. In this test, the additive samples of the reaction product compositions to be tested were first dissolved in 3.0 wt. % methanol and thereafter dissolved in Base Fuel A in a concentration of 100 PTB (100 pounds of additive per 1000 barrels of fuel, equivalent to about 0.033 weight percent of additive). In a nitrogen/hot air environment the gasoline was then atomized and sprayed onto a heated aluminum tube. After 100 minutes, the deposits which were formed on the tube were weighed. Gasolines which form larger amounts of deposits on the heated aluminum tube cause the greatest ORI when employed in an internal combustion engine. The CCDST was also employed to measure the deposit tendencies of a high reference fuel (Example H), known to yield a large deposit, and a low reference fuel (Example L), a standard unleaded gasoline known to yield a low deposit. The results are summarized below:

The above results illustrate that motor fuel compositions of the instant invention were slightly superior to the low reference unleaded base fuel and greatly superior to the high reference standard fuel in terms of resistance to deposit formation, and consequently in terms of ORI-inhibition.

For convenience in shipping and handling, it is useful to prepare a concentrate of the reaction product of the instant invention. The concentrate may be prepared in a suitable liquid solvent such as toluene or xylene, with xylene being- particularly preferred. In a preferred mode of preparing a concentrate of the instant invention, approximately 0.1-10.0, preferably 5.0-10.0 weight percent of the reaction product of the instant invention is blended with a major amount of liquid solvent, preferably xylene.

Motor fuel and concentrate compositions of the instant invention may additionally comprise any of the additives generally employed in motor fuel compositions. Thus, compositions of the instant invention may additionally contain conventional carburetor detergents, anti-knock compounds such as tetraethyl lead compounds, anti-icing additives, upper cylinder lubricating oils, and the like. In particular, such additional additives may include compounds such as polyolefin polymers, copolymers, or corresponding hydrogenerated polymers or copolymers of C.sub.2 -C.sub.6 unsaturated hydrocarbons, or mixtures thereof. Additional additives may include substituted or unsubstituted monoamine or polyamine compounds such as alkyl amines, ether amines, and alkyl-alkylene amines or combinations thereof.

It will be evident that the terms and expressions employed herein are used as terms of description and not of limitation. There is no intention, in the use of these descriptive terms and expressions, of excluding equivalents of the features described and it is recognized that various modifications are possible within the scope of the invention claimed.