US2720449A - Motor fuels - Google Patents

Description

United States Patent Office 2,720,449 Patented Oct. 11, 1955 No Drawing. Application October 27, 1952,

Serial Nil-317,146

so ti c1. 44-69) fThis: innention relatesto motor fuels for spark ignition and to anti-knock compositions for use in su otor fuels. o,

In perating internal combustion engines, particularly the modern engines with high compression ratios, it has been found that the tendency for the fuel mixture to preigniteincreases as the engine is operated. ..Also, the octane value of the fuel required to prevent knock must be increased after the engines have been in operation forsome time and this so-called octane demand increases until a fairly constant value is reached. It is believed that both these effectslare closelyrelate'd to the formation of solid deposits in the engine, although the present invention does not dependon any theory for the causelof the increased o'ctane demand and increased pre-ignitiontendency. It has been reported by Hughes et al. in Industrial and Engineering Chemistry, -43, 2841-2844. (1951) that alkyl boratesof. the. formula .B OR)3, such as triethyl and triisobutyl borates, and alkyl borines of the formula RsB, such as normal and tertiary butyl borines, incorporated iii-the gasolineused, reduce the increase in octane reqnirement Compoundsnof these types, however, cannot be ,usediunder actual practical conditions because of their reactivity. Thus, the. borines are very readily oxidized, evenatthedilutionat which theywould be used in gasoline, ,and some are even; spontaneously inflammable in pure form. The borateestersy show anflequally: serious sensitivity to hydrolysis .andflare rapidly attacked by the small amount of water always present in commercial gasoline. Even when theyare used in dried gasoline in experimentalvengine tests, they are hydrolyzed by atmospheric moisture' in the carburetor and in' a fairly short time clog its passage withsolid hydrolysis products.

It is an object of the present invention to provide improved motor fuels for-"spark ignition engines. Another Object is to provide motor' fuels fo'r spark ignition engines whichminimizethe tendency of deposits to promote preignition during continued engine if operationr A further object is to provide new and improved anti-knock com.- positions foraddition to motor fuels for spark ignition engines. A still further object is to provide anti-knock compositionswhich, when added to motor fuels for spark ignition engines, cause the motor fuels to minimize the tendency of deposits to'promotepre-ignition during continued engine operation. Other objects are, toyprovide new compositions of matter an h J Still otherobjects will appearhereinafter. a

The above and other objects may be accomplished by my invention which comprises hy drocarbon motor fuels for spark ignition engines which contain tetraethyl lead andgror each gallon of motor fuel, fifom 0.1to about 3 ml.

of aboroi fle ester. formula B(Q ch con tains to carbon and'wherein each R is a hydrocarbon radical of 2 as 7 carbon atoms, and antimeek mixturecompiising tetraethyl lead and between 2? and0.021volumes of h boronate esters for each volutheof tetraethyl lead.

advance the: art.

The boron ate estershfjmyinvention arej veryeffective in reducing the tendency of deposits to promote pre ignition of motor fuels, containing tetraethyl lead, in spark ignition engines during continued engine operation. By pre-ignition is meant ignition of the fuel-air mixture in the engine cylinder by hot deposit surfaces. My boronate esters have the unpredictable and unobvious advantage, over other boron compounds previously proposed for this purpose, of being very stable toward oxygen and moisture when dissolved in hydrocarbon motor fuels and in tetraethyl lead anti-knock compositions, so that they are quite satisfactory for use under the conditions encountered in practice; that is, they are highly resistant to oxidation and to hydrolysis in such solutions at atmospheric temperatures over long periods of time and under the conditions prevailing in the carburetors and intake manifolds of spark ignition engines. Also, they are soluble in the hydrocarbon motor fuels and in the antiknock mixtures, at least to the extent required for the purposes of my invention. Such boronate esters do not afiect appreciably the octane numbers of the motor fuels. Neither do they deleteriously affect the stability of the motor fuels but usually improve the stability of the motor fuels, particularly in the absence of substantial amounts of water.

The motor fuels will, preferably, be gasoline, but may be any other combustible liquids of suitable volatility commonly employed as fuels for spark ignition engines, including paraflinic, naphthenic and aromatic hydrocarbons, isooctane and mixtures of isooctane with other suit in the motor fuel will be varied as is usual with the engine and its use.

tration of tetraethyl lead is usually in the range of from about 1.5 ml. to about 3.0 ml. per gallon of motor fuel. In light airplane engines, the concentration of tetraethyl lead is usually in the range of from about 1 ml. to about However, larger high output aircraft engines usually require from about 2.5 ml.

In automotive engines, the concen- 2 ml. per gallon of motor fuel.

to about 5 ml. of tetraethyl lead per gallon of motor fuel.

The motor fuel may contain a halo-hydrocarbon lead scavengingagent in an amount up to about 5 theories, usually from about 1 to about 5 theories, and preferably from about 1 to about 2 theories, based on the tetraethyl lead. One theory of a scavenging agent is that quantity which provides 2 atoms of active halogen per.

atom 'oflead in the tetraethyl lead. The class of halohydrocarbon scavenging agents is well known and a great many of them have been disclosed in prior patents and in the literature. Generally, they are hydrocarbons in which at leastone hydrogen has been replaced by chlorine or bromine or both. The most commonly employed scavenging agents are ethylene: dichloride and ethylene dibromide, and they are preferred scavenging agents in the compositions of my invention. Of the lead compounds found in the engine deposits, the lead halides, such as PbClz and PbBrz, formed by the reaction of lead with the scavenging agents, appear to be the most active in promoting preignition. Hence, it is desirable to use the minimum permissible amount of scavenging agent so as to further reduce the tendency forpreignition.

The boronate esters of my invention have the formula" RB( OR)2fwherein each R is a hydrocarbon radical of 2 to 7 carbon atoms and contain a total of from 10 to 14 carbon atoms. I The total number of carbon atoms in the boronate esters is that required to provide compounds: havinga volatility roughly approximating that of tetraethyl lead. Preferably, the boronate esters will contain from 12 to 14 carbon atoms. The Rs in the formula may be the same or different and may be alkyl, alkylene, aryl, aralkyl, alkaryl or cycloaliphatic radicals. The alkyl radicals may be primary, secondary or tertiary, and straight or branched chain radicals. Ordinarily, each R is a monovalent radical, but two Rs may together represent a divalent radical such as a polymethene radical. Preferably, one R will be an alkyl radical of 4 to 5 carbon atoms and each of the other Rs will be a hydrocarbon radical of the class of alkyl radicals of 3 to 5 carbon'atoms, and aryl radicals of 6 to 8 carbon atoms. More particularly, I prefer the boronate esters which contain 12 to 14 carbon atoms and in which each R is an alkyl radical of 4 to 5 carbon atoms, such as di-nbutyl n-amyl-boronate, di-n-butyl n-butylboronate, di-isobutyl t-butylboronate, di-isobutyl n-butylboronate, di-nbutyl t-butylboronate, and diamyl amylboronates. The most preferred boronate esters are di-n-butyl n-butylboronate and di-isobutyl n-butylboronate. Other boronate esters, within the scope of my invention, are:

Diethyl phenylboronate Di-isobutyl ethylboronate Diallyl n-butylboronate Di-n-butyl propylboronate Di-isobutyl phenylboronate The boronate esters and methods of making them are,

in general, known to the art. Those specifically disclosed herein were made either by esterifying the corresponding free boronic acid, made by the method of Snyder, Kuck and Johnson disclosed in I. A. C. S., 60, 105 (1938), or by reacting equivalent amounts of the required Grignard reagent and the borate ester.

The boronate esters of my invention will be employed in a concentration of from 0.1 ml. to about 3 ml. per gallon of motor fuel, and preferably in a concentration of from about 0.1 ml. to about 1 ml. per gallon.

Ordinarily, tetraethyl lead is sold in the form of an anti-knock mixture for addition to motor fuels. Such anti-knock mixtures usually consist essentially of tetraethyl lead, the desired proportion of halo-hydrocarbon lead scavenging agent, a dye for identifying the composition and the motor fuel containing it, and a small amount of a liquid hydrocarbon diluent. While the boronate esters of my invention may be added to the motor fuel separately from the tetraethyl lead, it is desirable to add them to the anti-knock mixture in a proportion to provide the desired amount in the motor fuel when the mixture is added to the motor fuel.

Thus, an important feature of my invention is an anti-knock mixture consisting essentially of tetraethyl lead and between 2 and 0.02 volumes of a boronate ester of my invention per volume of tetraethyl lead. Usually, such mixtures will contain the desired scavenging agents. The boronate esters are miscible with the tetraethyl lead and with mixtures thereof with the scavenging agents. Preferably, the boronate ester will be in the proportion of from about 0.5 to about 003 volume per volume of tetraethyl lead. Also, preferably, the scavenging agent will be in a proportion of from about 1 to about 2 theories. Usually, it Will be desirable to include in the anti-knock mixture a dye for the purpose of identifying the mixtureand the motor fuel containing it, and the usual liquid hydrocarbon diluent. The resulting com positions are stable, homogeneous liquid compositions which are particularly suitable for addition to motor fuels for the purpose of preventing knocking and of reducing the tendency of the motor fuel to create combustion chamber deposits prone to cause pre-ignition during continued operation of the engine with such motor fuel.

In order to more clearly illustrate my invention, preferred modes of carrying the same into effect and the advantageous results to be obtained thereby, the following examples are given:

Example 1 One gram (about 0.005 mole) of di-n-butyl n-butylboronate was shaken in a flask with 50 ml. isooctane (94 ml. of boronate per gallon of isooctane) and ml. water for 4 hours at room temperature. At the end of this time, no acid was found in the water layer as determined by titration with caustic indicating negligible hydrolysis. When tri-n-butyl borate was treated in a similar manner, 4.6% of the ester was hydrolyzed under these mild conditions.

Example I] About 0.002 mole (0.4 'gr.) of various boronate esters were agitated with ml. of 85 octane number reference fuel consisting of 85 vol. isooctane and 15 vol. n-heptane (75 ml. of boronate per gallon of fuel) and 20 ml. water for minutes at C. The approximate per cent of the boronate ester, which was hydrolyzed to acid, was determined by titration of the water layer with caustic. The results are shown in the following table: I

No.0f Percent P 9 Carbons Hydrolyzed Diethyl phenylboronate .Q Diisobutyl ethylboronate Diallyl-n-butylboronate Di-n-butyl propylboronate. Diisobutyl phenylboronate Diisobutyl tert.-butylboronate Diisobutyl-n-butylb oronate Di-n-butyl-n-butylb oronate Di-n butyl-n-amylboronate.

Similar experiments with tri-n-butylborate showed that hydrolysis takes place faster than the ester can pass from the fuel into the water phase, and appears to be complete inv less than 5 minutes. t

This example shows clearly that rather drastic conditions of concentration and temperature (never expericnced-in gasoline storage) are required to hydrolyze the boronate esters, whereas the borates are hydrolyzed almost immediately. While even the least stable boronate esters are sufiiciently stable for use under practical conditions, those which hydrolyze to the extent of less than under the conditions of this example are preferred.

1 Example II I Diisobutyl n-butylboronate was evaluated as a fuel additive in 60 octane number (0. N.) primary reference fuel (60% isooctane and 40% n-heptane by volume) both with and without tetraethyl lead by the standard knock rating procedures in a Cooperative .Fuel Research engine. With the research method (ASTM D908-47T).

and with the motor method (ASTM D357-47), the following results were obtained: 7 1

Octane Numbers Research Motor Method Method 60 O N. ref. fuel 60.0 60.0 60 O. N. ref. fuel +3 ml. b0 59. 6 59. 5 60 0. N. fuel +3 ml. TEL/gal 84. 5 83.0 60 0. N. fuel +3 ml. TEL/gal. +3 ml. boronate/gal- 84. 6 84. 3

Example -I V Example V Several commercial gasolines were mixed with 1.0 ml. per gallon of diisobutyl n-butylboronate and stored at 110 F. over a layer of water to determine their stability in the presence of the boronate ester. The gasolines stability .was measured by means of induction period (for oxygen absorption) and by ASTM gum determinations, in mg. of gum per 100 ml. of the gasoline. The results are shown below (averages of two determinations each):

Induction ASTM ASTM Gasoline 3, 53 Gum g g min. (Fresh) storage) Gasoline A 359 9. 6 13.0 Gasoline A-l-boronate. 417 7.8 7.9 asoline B 603 6. 6 4. 5 Gasoline B+boronat 497 4. 8 2. asoline O 387 2.2 2. 6 Gasoline C+boronate. 353 3. 8 1111 Gasoline D 285 5.0 5. Gasoline D boronate 303 4. 5 5. 9

This example clearly shows that the boronate ester exerts no deleterious effect on the stability of the commercial gasoline. In fact, in storage tests at room temperature with a typical catalytic cracked gasoline, the boronate appeared to impart superior stability to the gasoline, as is shown in Example VI.

Example VI A typical catalytic cracked gasoline, mixed with diisobutyl n-butylboronate ester and/or tetraethyl lead, containing 1 theory of ethylene dichloride and 0.5 theory of ethylene dibromide, as indicated below, was stored at room temperature for one month both in the presence and in the absence of water. ASTM gum determinations were made on the gasoline. The water layers from the stored samples were titrated with standard sodium hydroxide to determine the liberated acid. The results are indicated below in which the gum is given in mg. per 100 ml. of the gasoline:

ASTM ASTM Gum (no Gum Millequiv. Oat. cracked fuel plus H20 (H20 acid in layer layer H2O layer present) present) (Control) l 26 7. 6 21 X- 3.0 mllgal. TEL 2. 2 3.0 22x10- 0.5 ml. boronate/gal 1.4 1. 8 0. 4X10- 0.5 ml. boronate/gel. plus 3.0 ml./ga1.

TEL 0 4 3 6 2.5 10- In addition to their effect upon pre-ignition, the boronate esters of the present invention have also been observed to have a desirable effect upon the increase in the octane demand which takes place as an engine is operated. In other words, it has been observed that the octane number of the fuel, required to operate an engine without knocking after it has been in operation for some time, is less if the engine has been operated over this period with a fuel containing a boronate ester. However, the effect of the boronate esters on pre-ignition, as shown in Example IV, is of greater practical significance,

particularly in the types of high compression engines now being developed. 1 a The boronate esters of my invention have the formula RB(OR) and hence structurally are somewhat similar to the borines, which have the formula R38. Since the borines are extremely susceptible to oxidation at atmospheric temperatures, tending to catch fire spontaneously; itwould be expected that the boronate esters would also be quite susceptible to oxidation, particularly at the elevated temperature present in the carburetors and the intake manifolds of spark ignition engines, and over long periods of storage. However, di-isobutyl n-butylboronate, for example, has stood in contact with air and inflammablematerial for several days without evidence of combustion. Also, when a motor fuel, containing a boronate ester, was used in the operation of an automobile engine over long periods of time as in Example IV, there was no evidence of any oxidation of the boronate ester, such as the deposition of non-volatile oxidation products in the carburetor and other parts of the intake system of the engine. 1

Since the boronate esters of my invention contain estergroups, and since the borate esters, having the formula B(OR)3, are very susceptible to hydrolysis in the presence of moisture at atmospheric temperatures, it would be expected that the boronate esters "of my invention would also be quite susceptible to hydrolysis in the presence of water or water vapor at atmospheric temperatures and particularly at the elevated temperatures present in the carburetors and. the intake manifolds of spark ignition engines, and overlong periods of storage. However, as shown. in the examples, motor fuels containing the boronate esters could beused or stored over long periods of time without difliculty, whereas a motor fuel containing a borate ester (tributyl borate) could not.

It will be understood that the preceding examples are given for illustrative purposes solely, and that my invention is not limited to the specific embodiments disclosed therein. On the other hand, it will be apparent to those skilled in the art that, within the scope of the general description, variations can be made in the boronateesters, in the proportions thereof employed in the motor fuels and in the anti-knock mixtures, in the composition of the motor fuels, in the composition of the anti-knock mixtures, in the engines, and in the techniques employed, without departing from the spirit or scope of my invention.

It will be apparent that, by my invention, I have provided novel motor fuels for spark ignition engines and novel anti-knock mixtures useful for making such motor fuels, whereby the tendency for pre-ignition during continued operation of the engines therewith is materially reduced by means which are practical. Therefore, it is obvious that my invention constitutes a valuable advance in and contribution to the art.

I claim:

1. A hydrocarbon motor fuel for spark ignition engines containing, for each gallon thereof, from about 0.5 to about 5 ml. of tetraethyl lead and from 0.1 to about 3 ml. of a boronate ester of the formula RB(OR)2 which contains 10 to 14 carbon atoms and wherein each R is a hydrocarbon radical of 2 to 7 carbon atoms at least two of which are aliphatic.

2. A hydrocarbon motor fuel for spark ignition engines containing, for each gallon thereof, from about 0.5 to about 5 ml. of tetraethyl lead and from 0.1 to about 3 ml. of a boronate ester of the formula RB(OR)2 which contains 12 to 14 carbon atoms and wherein each R is an alkyl radical of 4 to 5 carbon atoms.

3. A hydrocarbon motor fuel for spark ignition engines containing, for each gallon thereof, from about 0.5 to about 5 ml. of tetraethyl lead and from 0.1 to about 3 ml. of di-n-butyl n-butylboronate.

4. A hydrocarbon motor fuel for spark ignition engines containing, for each gallon thereof, from about 0.5 to about 5 ml. of tetraethyl lead and from 0.1 to about 3 ml. of di-isobutyl n-butylboronate.

5. An anti-knock mixture consisting essentially of tetraethyl lead and between 2 and 0.02 volumes per volume of tetraethyl lead of a boronate ester of the formula RB(OR)2 which contains 10 to 14 carbon atoms and wherein each R is a hydrocarbon radical of 2 to 7 carbon atoms at least two of which are aliphatic.

6. An anti-knock mixture consisting essentially. of tetraethyl lead and between 2 and 0.02 volumes per volume of tetraethyl lead of a boronate ester of the formula RB(OR)2 which, contains 12 to 14 carbon atoms and wherein each R is an alkyl radical of 4 to 5 carbon atoms.

7. An anti-knock mixture consisting essentially of tetraethyl lead and between 2 and 0.02 volumes per volume of tetraethyl lead of di-n-butyl n-butylboronate.

8. An anti-knock mixture consisting essentially'of tetraethyl lead and between 2 and 0.02 volumes per volume of tetraethyl lead of di-isobutyl n-butylboronate.

9. An anti-knock mixture consisting essentially of tetraethyl lead, from about 1 to about 5 theories of a halohydrocarbon scavenging agent, and from about 0.5 to about 0.03 volume per volume of tetraethyl lead of a boronate ester of the formula RB(OR)2 which contains 10 to 14 carbon atoms and wherein each R is a hydrocarbon radical of 2 to 7 carbon atoms at least two of which are aliphatic.

10. An anti-knock mixture consisting essentially of tetraethyl lead, from about 1 to about 5 theories of a halo--hydrocarbon scavenging agent, and from about 0.5 to about 0.03 volume per volume of tetraethyl lead of a boronate ester of the formula RB(OR)2 which contains 12 to 14 carbon atoms and wherein each R is an alkyl radical of 4 to 5 carbon atoms.

11. An anti-knock mixture consisting essentially o tetraethyl lead, from about 1 to about 5 theories of a halohydrocarbon scavenging agent, and from about 0.5 to about 0.03 volume per volume of tetraethyl lead of di-nbutyl n-butylboronate.

12. An anti-knock mixture consisting essentially of tetraethyl lead, from about 1 to about 5 theories of a halohydrocarbon scavening agent, and from about 0.5 to about 0.03 volume per volume of tetraethyl lead of di-isobutyl n-butylboronate.

13. A hydrocarbon motor fuel for spark ignition engines containing, for each gallon thereof, from about 0.5 to about 5. ml. of tetraethyl lead and from 0.1 to about 3 ml. of a boronate ester of the formula RB(OR)z which contains 10 to 14 carbon atoms and wherein the R attached to the boron atom is a hydrocarbon radical of the class consisting of alkyl radicals of 3 to 5 carbon atoms and a phenyl radical and each of the other Rs is an alkyl radical of 4 to 5 carbon atoms.

14. An anti-knock mixture consisting essentially of tetraethyl lead and between 2 and 0.02 volumes per volume of tetraethyl lead of a boronate ester of the formula RB(OR)2 which contains 10 to 14 carbon atoms and wherein the R attached to the boron atom is a hydrocarbon radical of the class consisting of alkyl radicals of 3 to 5 carbon atoms and a phenyl radical and each of the other Rs is an alkyl radical of 4 to 5 carbon atoms.

15. An anti-knock mixture consisting essentially of tetraethyl lead, from about 1 to about 5 theories of a halo-hydrocarbon scavening agent, and from about 0.5 to about 0.03 volume per volume of tetraethyl lead of a boronate ester of the formula RB(OR)2 which contains 10 to 14 carbon atoms and wherein the R attached to the boron atom is a hydrocarbon radical of the class consisting of alkyl radicals of 3 to 5 carbon atoms and a phenyl radical and each of the other Rs is an alkyl radical of 4 to 5 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,151,432 Lyons et al Mar. 21, 1939 2,257,194 Rosen Sept. 30, 1941 FOREIGN PATENTS 50,459 France Nov. 14, 1940

Claims (1)

1. A HYDROCARBON MOTOR FUEL FOR SPARK IGNITION ENGINES CONTAINING, FOR EACH GALLON THEREOF, FROM ABOUT 0.5 TO ABOUT 5 ML. OF TETRAETHYL LEAD AND FROM 0.1 TO ABOUT 3 ML. OF A NORONATE ESTER OF THE FORMULA RB(OR)2 WHICH CONTAINS 10 TO 14 CARBON ATOMS AND WHEREIN EACH R IS A HYDROCARBON RADICAL OF 2 TO 7 CARBON ATOMS AT LEAST TWO OF WHICH ARE ALIPHATIC.