US3198611A - Tetraalkyl lead antiknock blends - Google Patents

Description

United States. Patent 3,193,611 TETRAALKYL LEAD ANTKNUCK BLENDS Edmund L. Niedzielsisi, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington,

DeL, a corporation of Deiaware No Drawing. Filed Mar. 15, 1952, Ser. No. 180,018

7 Claims. (Cl. 44-69) This invention is directed to tetraalkyl lead antiknock blends for gasoline comprising tetraalkyl lead antiknock agents and organic halogen compounds. More particularly, the present invention is directed to the use in such compositions of organic halogen compounds which under conditions of storage are highly compatible with the alkyl lead antiknock compound, and which under conditions of use in high octane number aromatic blend gasolines significantly enhance the antiknock value of the alkyl lead antiknock compound While at the same time act efficiently as scavenging agents for the lead products of combustion.

Tetraalkyl lead antiknock compositions are widely used to improve octane ratings of fuels for high compression Otto cycle engines. These compositions consist essentially of the organolead antiknock agents and at least one organic halogen compound that is a scavenger for lead in the combustion process. Practically speaking, the scavenger material should be miscible and compatible with the tetraalkyl lead compound, forming therewith 'a homogeneous, normally liquid storage-stable product, and in use it should have no harmful effect on the antiknock properties of the alkyl lead component. However, many such organic halogen compounds lack these properties. They are in general reactive towards tetraalkyl lead, forming haze and insoluble matter under storage conditions, as disclosed, for example, in US. 2,722,477 and in US. 3,005,780. In addition, as a class, these organic halogen compounds tend to be antagonistic to the antiknock property of the alkyl lead, particularly at high concentrations, as disclosed by Livingston, Antiknock Antagonists, Industrial and Engineering Chemistry, vol. 43, pages 663-664 (1951). While the art describes many organic halogen compounds that are lead scavengers, in commercial practice ethylene dichloride and ethylene dibromide are normally used.

The quantity of ethylene dichloride and ethylene dibromide used is dependent upon the theory of halogen atom to lead atom. Thus, 1.0 theory of halogen is defined as the quantity theoretically required for reaction of the halogen with the lead to form the lead halide, which quantity is two atoms of halogen per atom of lead. Thus, for aviation use a quantity of ethylene dibromide is used which would give, per atom of Pb as tetraalkyl lead, two atoms of Br as ethylene dibrornide (1.0 theory). While, for automotive use, as described, for example, in US. 2,398,281, a quantity of ethylene dibrornide and ethylene dichloride is used which would give, per atom of Pb as tetraalkyl lead, one atom of Br as ethylene dibromide (0.5 theory) plus 2 atoms of Cl as ethylene dichloride (1.0 theory).

It is also known that hydrocarbon fuels of the gasoline boiling range that contain relatively large proportions of aromatic hydrocarbons respond rather poorly (relative to parafiinic hydrocarbons) to the knock suppressing potential of tetraalkyl lead antiknock agents, Recently it has been found that certain volatile organic substances (ineludin carboxylic acids, their anhydrides and esters) are appreciators of organolead antiknock activity in the high octane number aromatic type fuels, enhancing the effectiveness of the antiknock agent. However, introduction of halogen substituents into such appreciators has been observed to exert a marked depreciating efiect. For example, Australian paent application 42,139/58 discloses "ice that monochlorotacetic acid and 2-chloropropionic acid among others are without antiknock eflect or are actually harmful in leaded fuel. It should be noted in this connection that antiknock improvements realized by means of alkyl lead antiknock appreciators often are of the order of a fraction of an octane number, unless rather large amounts of material are used. Such increases while appearing numerically small are nevertheless significant, particularly at the 100 octane number and greater level, in view of the technical diih'culty and high cost of achieving increased fuel quality by hydrocarbon refining methods and by use of additional amounts of the conventional organometal antiknock agents. For example, adding a 4th ml. of tetraethyl lead per gallon of aromatic gasoline as herein contemplated and already contain-ing 3 ml. tetraethyl lead per gallon, and which leaded fuel has a Research Method octane rating of about 100, increases.

the knock rating about 1 octane number.

It is, therefore, an object of this invention to provide novel fuel compositions.

It is another object of this invention to provide new and novel homogeneous liquid storage stable tetraalkyl lead antiknock blends comprised essentially of the tetraalkyl lead and one or more organic halogen scavengers for lead.

It is still another object to provide novel blends of gasoline wherein the organic halogen scavenger component provides the property of appreciating the antiknock effect of the tetraalkyl lead in high octane number aromatic type gasolines as Well as the property of scavenging lead in the combustion process.

These and other objects will be apparent in the following description and claims.

More specifically, the present invention is directed to a tetraalkyl lead antiknock-lead scavenger blend comprising essentially a tetraalkyl lead and from about 0.2 to 1.0 theory of chlorine as a trichloromethyl substituted organic ester having the formula Cl CC(R) -*O-Ac, Where R is a C C alkyl and Ac a C -C acyl radical.

The present invention is also directed to a motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range of which at least 15% by volume are aromatic hydrocarbons of the character of those occurring in catalytically cracked and reformed gasolines, and which mixture of hydrocarbons has an octane rating of at least as measured by the ASTM Research Method (D90859), an antiknock quantity of a tetraalkyl lead antiknock agent and from 0.2 to 1.0 theory of a trichloromethyl substituted organic ester having the formula Cl C-C(R) -OAc, where R is a alkyl and Ac a C -C acyl radical.

This invention is based on the discovery that (1) blends of tetraalkyl lead antiknock such as tetr-aethyl lead (TEL) wit-h a trichloromethyl substituted organic ester such as 1,l, l-t-richloro2-methyl 2-propyl acetate, viz. Cl CC(M) OCOl\I6, shows greater storage stability than the comparable commercial blends of TEL with ethylene dichloride and ethylene dibromide and (2) such blends, when used in high octane number aromatic gasolines as herein described, provide greater improvements in the knock resistance of the fuels than obtained with TEL alone or in combination with the conventional ethylene dihalide scavengers. a

Under conditions ordinarily encountered in the hanling, shipping and "storing of commercial blends, the blends of the present invention remain clearer and more free of haze and sediment for significantly-longer periods of time. 11 contrast, the use of an isomeric trichloromethyl substituted ester, namely, tert-butyl trichloroacetate, viz. CCl CO C(Me) results in highly unstable blends with respect to the formation of haze and insoluble matter. The significant improvement in the antiknock per ormance of the blends of this invention is attributed to the appreciating effect of the trichloromethyl substituted ester component. Such results are surprising in view of the fact that they are obtained with relatively small amounts (less than 0.1 volume percent based on the gasoline) of the chloro compound. The prior art on appreciators for alkyl lead compounds, for example the Australian appln. 42,139/58 heretofore referred to, discloses that there is no beneficial effect when the concentration of the appreciator is below 0.1 volume percent of the gasoline.

The organolead antiknock employed in the practice of the present invention may be any of those known to the art for such purpose, but usually will be a lower tetraalkyl lead, e.g., methyl triethyl lead, tetraethyl lead, tetrarnethyl lead, dimethyl diethyl lead, trimethyl ethyl lead, tetraisopropyl lead, and the like, and mixtures of any two or more of such organolead antiknock agents. The organolead antiknock agent will be employed in an antiknock quantity, usually in the proportion of from about 1 to 4 grams of Pb for each gallon of the motor fuel, and preferably at concentrations of from about 2 to 3 grams Pb per gallon of fuel. The chloro-substituted esters are lower alkanoic esters of trichlorornethyl dialkyl carbinols having the formula CCl -C(R) OH, R being methyl or ethyl, exemplified by the formate, acetate and propionate of chloretone, CCl C(Me) OH. They are conveniently made by acylating such carbinol as chloretone with the appropriate acid chloride as .cnown to the art. As starting carbinol, homologs of chloretone may also be used such as those obtained by carbonyl addition of chloroform to methyl ethyl lictone or diethyl ketone, and mixtures of the alcohols and mixtures of the acids may be employed in the acylating reaction to produce mixtures of esters of the formula CCl C(R);OAc, where R methyl or ethyl or both and Ac stands for one or more acyl radicals of the C -C alkanoic acids. 1,1,l-trichloro-Z-methyl-Z-propyl acetate is particularly preferred.

The trichloromethyl-containing esters are normally liquid, miscible with tetraalkyl lead antiknoclc compounds, soluble in hydrocarbon solvents, and insoluble in water. They may be employed alone as the sole scavenger or in combination with other known organic halogen coapounds that are scavengers for lead in combustion processes. In general there may be employed 0.5 to 1.0 theory chlorine as a trichloroniethyl-containing ester and from 0.5 to 1.5 theories of halogen in the form of chloroand bromohydrocarbon scavenging agents, with generally not more than about 0.5 theory of the total halogen being bromine. Preferably, in the practice of this invention, the trichloromethyl-containing esters are used with one or more ethylene dihalide scavenger, e.g., ethylene dichloride, ethylene dibromide, or ethylene chlorobromide. In the formulation of antiknock blends, the trichloromethylcontaining esters may be added to the conventional Motor Mix formulation (0.5 theory bromine as ethylene dibromide and 1 theory chlorine as ethylene dichloride) or they may replace part of the other halogen compounds to the extent of 0.2 to 1 theory halogen (preferably 0.5

to l theory) as defined above. For example, the scavenging formulation may consist of 0.5 theory chlorine as chloro-ester, 0.5 theory chlorine as ethylene dichloride, and 0.5 theory bromine as ethylene dibromide; or it may consist of 0.5 theory chlorine as chloro-ester and 1.0 theory chlorine as ethylene dichloride. Normally the total halogen content (including that provided by the other halogen compounds) will correspond to at least 1.0 and not exceed 2.5 theories. r

In connection with the heretofore described use of alkyl lead appreciators in amounts of at least 0.1 volume percent of the fuel, it should be noted that at the normal antiknock use level of l to 4 grams of Pb/gal. of fuel that 1.0 theory halogen of any of the compounds contemplated' herein corresponds to about 0.07 volume percent or less of the gasoline.

The mixture of hydrocarbons which constitute the principal component of the fuel compositions utilized in the practice of this invention may be a commercial gasoline containing the aromatic hydrocarbons in the herein described amounts or it may be a blend of hydrocarbons of the character of those present in such gasolines. Thus, for example, it may be a catalytic-cracked stock, a catalytic-reformed stock, or blends of one or more of these cracked and reformed stocks, or blends of one or more of the heretofore described stocks with saturated stocks such as the synthetic alkylates and straight run stocks.

Typical aromatic hydrocarbons which are essential components of the motor fuels of this invention, and which are of the character of these aromatic hydrocarbons which r are produced in catalytic cracking and catalytic reforming operations, are the monoand poly-lower alkyl benzenes such as toluene, ethylbenzene, the xylenes, and the like.

Typical catalytic-cracked refining stocks which may be utilized in the practice of the present invention contain from about 6 to about volume percent aromatic hydrocarbons, about 29-44 volume percent olefins, the rest saturated hydrocarbons. Catalytic-reformed stocks run higher in aromatics, usually -70 volume percent, and are lower in olefins. Synthetic alkylates are essentially saturated hydrocarbons, high in isoparatfins. Stocks such as these are blended in various proportions for the production of commercial fuels for spark ignition engines. These fuelsnormally boil within the range of about 80 F. to about 440 F. Blended fuels for commercial use, such as those for automotive use, contain on the average up to about volume percent aromatic, up to about 30 volume percent olefinic-, the rest saturated hydrocarbons.

The motor fuels of the present invention contain at least 15 volume percent, more usually at least 20 volume percent, and not more than about volume percent aromatic hydrocarbons. Olefinic hydrocarbons are not essential and may be present in the normally occurring proportions. Preferably the fuels will contain at least about 25 volume percent aromatics and less than 30 volume percent oler'inics.

Preferably also, the base fuels will be of high quality with respect to knock resistance, having a knock rating at least as measured by the ASTM Research lriethod.

The motor fuels may also contain other additives normally associated with the finished gasolines, such as antioxidants, metal deactivators, dyes, detergents, antiicing agents, ignition control additives such as phosphorus compounds, and the like.

Representative examples tion follow:

illustrating the present inven- EXAMPLE 1 Table I .St0rage-stability of TEL antiknock blends [Scavengerz 1.0 theory ethylene dichloride plus 0.5 theory of halogen as co-scavenger] Blend CoScavenger Observation on Blend (A) 1,1,1-trichloro-2- Essentially unchanged after 3 methyl2-pr0pyl weeks; no haze, no rusting. acetate. (B) t-Butyl trichloroacc- Gclatinous precipitate after tats. one oay. (C) Ethylene-dibromidc Considcrably darkened after 2 weeks; blend hazy and metal rusted.

The comparison shows that Blend A illustrating this invention is significantly more storage-stable than the conventional Motor Mix proportions represented by Blend C. Blend B, containing an isomeric trichloroester not of this invention, is decidedly inferior in storage stability, the t-butyl trichloroacetate evidently being reactive towards tetraethyl lead.

EXAMPLE 2 Table H.E ect of scavenger composition on octane rating 0] leaded high aromatic gasoline [TEL C0ue.=3 mL/gaL] Change in Test Scavenger (Research) (1) 1.0 theory ethylene dichloride plus 0.5 0. 1

theory ethylene dibromide. 1.5 theories ethylene dichloride 0. 0 1.0 theory ethylene dichloride plus 0.5 +0. 2

theory 1,1,1-trichloro-2-methyl-Z propyl acetate.

EXAMPLE 3 An aromatic gasoline consisting of 34 volume percent aromatic hydrocarbons, 23 volume percent oleilns and 43 volume percent saturated hydrocarbons, and having a leaded Research Method octane rating of 99.3 when leaded with 3 ml. TEL/ gal. as Motor Mix, is treated to contain 3 m1. TEL/ gal. together with 1.0 theory chloride as ethylene dichloride and 0.5 theory additional chlorine as 1,1,1-trichloro-2-methyl-2-propyl actate. The leaded Research Method octane number is 99.5 (0.2 octane number increase).

An increase of 0.3 octane number is obtained, on comparing the same scavenger systems in the same gasoline, when instead of tetraalkyl lead there is used a mixture of tetraalkyl lead as follows in an amount providing 3.1 grams of Pb/gal. of the fuel: 6.25 mole percent tetramethyl lead, 25 mole percent trimethylethyl lead, 37.5 mole percent dimethyldiethyl lead, 25 mole percent methyltriethyl lead, and 6.25 mole percent tetraethyl lead.

1,1,1-trichloro-Z-methyl-Z-propyl acetate may be replaced with substantially the same results in any of the preceding representative examples by any one or more of the following trichlorornethyl substituted esters in the practice of this invention: 1,1,l-trichloro-Z-methyl-Z- propyl formate, 1,1,l-trichloro-2-methyl-2-propyl propionate, 1,1,1-trich1oro-Z-methyl-Z-butyl acetate, and 1,1,1- trichloromethyl-2-ethyl-2-butyl acetate.

It is understood that the preceding examples are representative and that they may be varied within the scope of the total specification disclosure, as understood and practiced by one skilled in the art, to achieve essentially the same results.

As many apparently Widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilegeis claimed are defined as fol lows:

1. A tetraalkyl lead antiknock-lead scavenger blend comprising a tetraalkyl lead and from about 0.2 to 1.0 theory of chlorine as a trichloromethyl substituted organic ester having the formula where R is a C -C alkyl and Ac is a' C -C acyl radical.

2. A tetraallryl lead antilcnock-lead scavenger blend comprising a tetraalkyl lead and from about 0.2 to 1.0 theory chlorine as 1,1,1-trichloro-2-methyl-2-propyl acetate.

3. A motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range of which at least 15% by volume are aromatic hydrocarbons and which mixture of hydrocarbons has an octane rating of at least 80, an antiknock quantity of a tetraalkyl lead antiknock agent and from 0.2 to 1.0 theory of chlorine as a trichloromethyl substituted organic ester having the formula Cl CC (R) OAc where R is a C -C alkyl and Ac is a C -C acyl radical.

4. A motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range of which at least 15% by volume are aromatic hydrocarbons and which mixture of hydrocarbons has an octane rating of at least 80, an antiknock quantity of a tetraalkyl lead antiknock agent and from 0.2 to 1.0 theory of chlorine as 1,1,1-trichloro-2-methyl-2-propyl acetate.

5. A tetraalkyl lead anticlznock-lead scavenger blend comprising a tetraalkyl lead, from 0.5 to 1.0 theory of chlorine as a trichloromethyl substituted ester having the formula wherein R is a C -C alkyl and Ac is a C -C acyl radical, and from 0.5 to 1.5 theories of halogen in the form of at least one halogen substituted hydrocarbon, wherein said halogen is taken from the group consisting of chlorine and bromine, with the proviso that not more than about 0.5 theory of said halogen is bromine and that said halogen substituted hydrocarbon acts as a scavenger for lead in combustion processes.

6. Atetraalkyl lead antiknock-lead scavenger blend of claim 5 wherein at least one of said halogen substituted hydrocarbons is an ethylene dihalide.

7. A tetraalkyl lead antiknock-lead scavenger blend of claim 5 wherein all of said halogen substituted hydrocarbons is ethylene dichloride.

Reterences Cited by the Examiner UNITED STATES PATENTS 2,210,942 8/40 Lipkin 44-70 FOREIGN PATENTS 107,863 7/39 Australia. 571,921 10/ 5 8 Belgium. 599,222 3/48 Great Britain. 880,457 10/61 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

Claims (1)

1. 3. A MOTOR FUEL COMPOSITION COMPRISING A MIXTURE OF HYDROCARBONS IN THE GASOLINE BOILING RANGE OF WHICH AT LEAST 15% BY VOLUME ARE AROMATIC HYDROCARBONS AND WHICH MIXTURE OF HYDROCARBON HAS AN OCTANE RATING OF AT LEAST 80, AN ANTIKNOCK QUANTITY OF A TETRAALKYL LEAD ANTIKNOCK AGENT AND FROM 0.2 TO 1.0 THEORY OF CHLORINE AS A TRICHLOROMETHYL SUBSTITUTED ORGANIC ESTER HAVING THE FORMULA