US3706541A - Antiknock liquid hydrocarbon fuel containing organic nitrogen containing compounds - Google Patents

Abstract

LIQUID HYDROCARBON FUELS ARE PROVIDED WHOSE ANTIKNOCK PROPERTIES ARE IMPROVED BY ADDING THERETO A SMALL AMOUNT OF AN AMINOFULVENE.

Description

Int. Cl. C101 1/22 US. Cl. 44-63 13 Claims ABSTRACT OF THE DISCLOSURE Liquid hydrocarbon fuels are provided whose antiknock properties are improved by adding thereto a small amount of an aminofulvene.

BACKGROUND OF THE INVENTION Field of the invention This invention generally relates to improved fuels for internal combustion engines. More particularly, it relates to improving the antiknock properties of such fuels by adding thereto a metal-free additive capable of imparting such properties.

Discussion of the prior art The octane number of a fuel is a measure of the ability to resist detonation caused by auto-ignition. When detonation occurs, it results in a rapid rise in combustion chamber pressure above that for normal combustion and causes high frequency pressure fluctuations and an audible sound that is referred to as knock. When detonation (knock) occurs, heat is released which promotes further detonation, causes a loss of power and, if sustained, can result in engine damage. Antiknock requirements of spark ignition engines increase with increasing compression ratio and are affected by such things as carburation, spark timing, type of transmission and other engine/vehicle design characteristics and changes in ambient conditions such as temperature, humidity and absolute pressure.

Specifically, it is well known that knock in spark-fired engines is due to the relatively slow oxidation of the endgas prior to the arrival of the flame front, the immediate cause being the extremely rapid combustion of the last part of the charge to burn.

It has been determined that the most economical burning of the fuel is obtained at the higher compression ratios, and as has already been stated, such higher compression ratios require higher octane numbers for knockfree operation. Because the design of modern automobile engines has been toward increased compression ratios, the demand has been for fuels of constantly improved antiknock quality. Refiners have met this demand by new and improved refining techniques and by the use of antiknock additives.

Antiknock agents most widely in use are those of the so-called metallic type, the leading example of which is tetraethyl lead. It has long been known, however, that the use of this and other metal-containing antiknock agents contributes to other difiiculties associated with the operation of high compression engines, as for example, spark plug fouling and preignition. Leaded gasolines have also recently been criticized for their alleged role in polluting United States Patent 6 3,706,541 Patented Dec. 19, 1972 the atmosphere. The art has for some time now been searching for non-metallic antiknock agents, and the present campaign to reduce or eliminate leaded agents has added new impetus to the search.

The most widely known non-metallic antiknock agents are aniline and certain alkyl derivatives thereof. This class of materials is represented by the formula where R, R and R are hydrogen or lower alkyl. Probably the best known non-metallic agent defined by this formula is N-methylaniline.

In the series Where R and R" are hydrogen and R' is alkyl, a decrease in antiknock effectiveness with increasing alkyl chain length occurs. This is illustrated in the following table.

Research octane Fuel blend: number (F--1) Base fuel 2 60.0 Base+3% aniline 75.4 Base+3% N-methylaniline 78.0 Base+3% N-ethylaniline 71.7 Base+3% N,Ndimethylaniline 60.0

1 ASTM designation D908-53, ASTM Manual of Engine Test Methods for Rating Fuels, 1953 Supplement.

AS'IM primary reference fuel (60% iso-octane, 40% nheptane).

Other compounds which are known to beefiective as antiknock agents are the phenylenediamines, represented by the formula where R, R, R" and R'" may be hydrogen, lower alkyl or aryl. Also, some of the nitriles, such as .propionitrile and isocyanates such as phenylisocyanate have some slight elfect on antiknock properties of a fuel. These latter two classes are, therefore, the least important of those mentioned.

US. Pat. 2,881,061 discloses as antiknock agents, a group of compounds in which the N-alkyl group is made to form a ring attached to a benzene ring ortho to the amine function. Such compounds have the general formula where n may be zero or 1.

SUMMARY OF THE INVENTION In accordance with the invention, there is provided a liquid hydrocarbon fuel composition comprising liquid hydrocarbon fuel and an amount sufficient to impart antiknock properties thereto of a compound of the formula wherein X is carbon or nitrogen, R is hydrogen or hydrocarbyl, R is selected from the group consisting of RIII \RIIII wherein R'" and R"" are selected from the group consisting of hydrogen, hydrocarbyl, and C -C alkyl-substituted hydrocarbyl;

--R and HN R \J V wherein the ring portions contain from about 3 to about 6 methylene groups, and may contain another heteroatom such as oxygen or nitrogen, R" is a hydrocarbyl, an R CHO group or a condensed --R OHO group, R being a hydrocarbyl, R is a hydrocarbyl and y is zero or 1, y being zero when X is nitrogen.

In the above hydrocarbyl shall means an alkyl or cycloalkyl containing from 1 to about 12 carbon atoms and an aryl or an aralkyl group containing from 6 to about 20 carbon atoms. Condensed --R CHO group shall mean such group condensed with a glycol such as ethylene glycol, hexamethylene glycol and the like, or with a primary amine such as an alkyl amine containing from 1 to about 16 carbon atoms, aniline, substituted aniline and the like, or with mixtures of such glycols and amines.

Preferred in the practice of this invention are those materials wherein R is selected from the group consisting of hydrogen and alkyl of from 1 to about 6 carbon atoms, R is selected from the group consisting of RV l T and N H wherein R' and R"" are selected from the group consisting of hydrogen, alkyl of from 1 to about 8 carbon atoms and aryl of from 6 to about 14 carbon atoms, i.e. phenyl, naphthyl and anthracyl, R is alkyl of from 1 to about 6 carbon atoms, and R" is selected from the group consisting of hydrogen, alkyl of from 1 to about 6 carbon atoms, CH and a condensed CHO.

Compounds active as antiknock agents for hydrocarbon fuels and which come within the above formula include: dimethylarninofulvene; diethylaminofulvene; dibutylaminofulvene; dioctylaminofulvene; ethylmethyl-aminofulvene; methyl-octyl-aminofulvene; methyl-phenyl-aminofulvene; methyl-, ethyl-, butyl-, octyl-, phenyl-, tolyl-, xylyland cresylaminofulvene; cyclopentyl-, cyclohexyl-, and cyclooctylaminofulvene; those 6-fulvenes wherein N is a part of a ring system, such as those made from pyrrole, morpholine and piperazine. Compounds with the above substituents, but where X is nitrogen are useful also, as for example a compound of the formula DESCRIPTION OF SPECIFIC EMBODIMENTS The agents described herein represent a new class of fuel antiknock additives. As is apparent from the formulae set forth above, all members contain at least one nitrogen atom somewhere in the molecule. This nitrogen may be attached to the external carbon or nitrogen atom of the ring, or it may be separated therefrom by another member. There is some evidence tending to establish the necessity for such nitrogen atom. For example, when X in the general formula is carbon and R and R are methyl groups, such compound is ineffective as an antiknock agent.

It is also believed that the effectiveness of the compound is influenced by structural factors other than the presence of a nitrogen or of a member double bonded to the cyclopentadiene ring. Thus, a compound of the for- CHaOOG CO 0 CH3 which has the H-fi-N-N moiety, has no effect whatever on the octane number of a fuel.

It is not known how or why the additive functions as an antiknock agent. While it is not known whether it is the compound per se or its oxidized form which is the effective agent, we believe that the oxidized form is an effective agent. It is known, for example, that the compounds of the invention react readily with oxygen in almost a mole to mole ratio. Very likely, then, the fulvene or fulvene-type derivative, reacted with one mole per mole of oxygen, is an active component.

That the oxidation product is an effective component is bolstered by the fact that the activity is increased and sustained by adding certain materials known to solubilize such oxidation products. One useful solubilizer" is aniline. Others which may be effective for this purpose are n methylaniline, N,N dimethylaniline, N,N-dimethylacetamide and fatty acid esters, such as t-butyl acetate and methyl and ethyl valerate.

Methods for preparing the compounds of this invention are known. In general, they may be prepared by reacting the appropriate methyl sulfate or fluoroborate complex with sodium cyclopentadienylsodium. For example, Organic Synthesis, vol. 47, pp. 52-53 discloses a method for preparing the complex Hi0 HCHzOSOr EXAMPLE 1 Preparation of H-CN(CH:)2

(a) One mole of dimethylformamide and 1 mole of dimethyl sulfate were mixed and allowed to stand at room temperature for 24 hours. One mole of the complex was obtained as a viscous colorless oil.

(b) To a solution of 0.5 mole of cyclopentadienylsodium (prepared in situ from cyclopentadiene and sodium hydroxide) in 250 ml. of tetrahydrofuran was added 0.5

mole of the complex made in .(a) above. After stirring for 2 hours at 20 C., filtration and evaporation of the solvent and recrystallization from cyclohexane gave a 50% yield of dimethylaminofulvene, the product having a melting point of 67-68 C.

EXAMPLE 2 Preparation of (a) The complex was prepared in the manner described for the Example 1 complex from one mole each of dimethylacetamide and dimethyl sulfate.

(b) To 0.5 mole of the complex made in part (a) was added 0.5 mole of cyclopentadienylsodium and the reac tion was carried out as shown in part (b) of Example 1.

In the examples which follow, unless so stated, the procedures, including quantities of reactants, were similar to those described in Example 1.

EXAMPLE 3 Preparation of H-C-N CH3) 1 II Ite The complex of Example 1(a) was reacted with methylcyclopentadienylsodium substantially as described in Example 1(b) EXAMPLE 4 Preparation of HCN Using procedures already described, a complex of the formula OCH;

was prepared from the complex of Example 1(a) and pyrrolidine, and this in turn was reacted with cyclopentadienylsodium to give the product, melting point 105.5-107" C.

EXAMPLE 5 Preparation of The compound was prepared by reacting equimolar amounts of pyrrole 2-carboxaldehyde and cyclopentadiene in methanol, in the presence of a small amount of npropylamine. The product was obtained as copper colored crystals and had a melting point of 120121 C.

EXAMPLE 6 Preparation of The complex omofi-monawmosor was prepared by reacting equimolar amounts of N-nitrosodimethylamine and dimethyl sulfate. Reaction of this complex with cyclopentadienylsodium gave the product, an orange-colored oil boiling at -101" C. at 8 mm. of Hg.

was prepared from n-methylformanilide and triethyloxonium fluoroborate. Reaction of this complex with cyclopentadienylsodium gave the product, melting at 67.5- '68.5 C.

EXAMPLE 8 Preparation of The compound of Example 1 was heated in an excess of aniline for 8 hours at 60 C.

EXAMPLE 9 Preparation of The compound of Example 1 was heated in an excess of dodecylamine for 8 hours at 60 C.

In a similar manner, the compound I OHC CHO was prepared.

EVALUATION OF PRODUCTS Fuel blends of the compounds described in the above examples were prepared and the Research Octane Numbers (RON) thereof were determined. The RON (ASTM D-2699), while determined under mold test engine operation, is a reliable tool for predicting performance of the fuel in actual use. The following table shows the results obtained.

TABLE 1 Research Weight octane percent number Test number Compound added compound (RON) 1 1. 0 93. 6 l 1. 0 93.0 (a) i 0. 5 85. 7 (b) 0. 5 91. 8

8 Example 6 I 0.5 85. 1 9 Example 7.. O. 5 92. 2 10-.-" Example 8.- 1 0.5 91. 5 11 Example 9 l 0. 5 92. 4

12 HCN(CH;) 1 0. 04 92. 8

CH0 i i CHO See footnotes at end of Table 2.

The compounds of this invention seem to have an additional unique characteristic. When they are added to a clean base fuel and this fuel is used in an engine for a time, there is a pm-conditioning" efiFect observed when the CFR engine is run under normal condition, that is to say, if the supply of base fuel plus additive is removed and a clear base fuel substituted, the RON will remain at the level reached prior to substitution, and in some instances will even exceed such RON. In one operation involving the compound of Test 3 in the above table, the fuel plus additive was run for about 68 minutes, at which time this supply was shut off. A clear base fuel was used to run the engine, and it was found that the RON so found was at a higher level from about 77 minutes to about 96 minutes (these times are totals of both runs). The following summarizes the data obtained.

TABLE 2 Cumulative RON, Fuel minutes average B 0 91. 2 Base plus 0.5% additive.-.. 4 9e 1 D0. 68 99. 1

Engine shutdown and clear base fuel substituted:

The fuel used, unless indicated otherwise, in obtaining the data summarized in Tables 1 and 2 had the following characteristics: 10% boiled to 122 F., 50% to 223 F. and 90% to 345 F., with an end point 01403" E; 33% aromatics, 9.4 olefins and 57.6% saturates. It was composed of 40% 100 reformate, 30% heavy T00, 10% light T00, 10% 100 straight run, 6% light alkylate and 4% butane.

9 Referring to Table 1, the fuel used was a synthetic" fuel containing 23.6% aromatics, 10.3% olefins and 66.1% saturates. It had an RON of .2. Contained also 0.5% by weight of aniline.

percent of compound RON 1 Actual automobile test.

It will be understood that the additives of the invention may be advantageously utilized in any hydrocarbon fuel 8 suitable for use in combustion engines, whether automotive or aviation.

The antiknock action of the compounds of the present invention is independent of other antiknock agents of either the metallic or non-metallic type. Hence they will increase the anti'knock ratings of fuels even though other antiknock agents are present. Furthermore, other additives designed to impart various improved properties to the fuel may be used along with the present additives. Thus, antioxidants, metal deactivators, anti-rust, antistalling and ignition control compounds may be used.

The amount of additive which may be used in the fuel will depend upon the particular fuel and the degree of improvement desired. In general, from about 0.1% to about 5% by Weight of additive may be used. Preferably, we use from about 0.1% to about 2% by weight.

Although the present invention has been described with certain specific embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of this invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims.

We claim:

1. A liquid hydrocarbon fuel composition comprising a liquid hydrocarbon fuel for a spark ignition engine and an amount sufficient to impart antiknock properties thereto of a compound of the formula wherein X is selected from the group consisting of nitrogen and carbon, R is selected from the group consisting of hydrogen and alkyl of from 1 to about 6 carbon atoms, R" is selected from the group consisting of hydrogen, alkyl of from 1 to about 6 carbon atoms, -CH0 and condensed --CHO, R is selected from the group consistwherein R' and R"" are selected from the group consisting of hydrogen, alkyl of from 1 to about 8 carbon atoms, and aryl of from 6 to about 14 carbon atoms, R is alkyl of from 1 to about 6 carbon atoms, and y is zero or 1, y being zero when X is nitrogen.

2. The composition of claim 1 wherein said compound is present in an amount of from about 0.1 to about 5% by weight.

3. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula 4. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula 5. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula II l 6. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula 7. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula I I HAN 8. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula 9. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula H-C-N 10. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the for mula C Ha 10 11. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula 12. The composition of claim 1 containing from about 0.1 to about 5% by weight of a compound of the formula l ono lono 13. A method of pre-conditioning an internal combustion engine comprising the step of running said engine with a liquid hydrocarbon fuel composition comprising a liquid hydrocarbon fuel and an antiknock amount of a compound of the formula wherein X is selected from the group consisting of nitrogen and carbon, R is hydrogen and alkyl of from 1 to about 6 carbon atoms, R" is selected from the group consisting of hydrogen, alkyl of from 1 to about 6 carbon atoms, CH0 and condensed -CHO, R is selected from the group consisting of R!!! -N i j and \RIIII N H References Cited UNITED STATES PATENTS 1,786,860 12/1930 Midgley, Jr. et a1. 4474 3,402,201 9/1968 Schmerling 4474 DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner US. Cl. X.R.