US2897069A - Motor fuel - Google Patents

Description

signors to Standard 'Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Application April 2, 1956 Serial No. 575,336

2 Claims. (Cl. 44-58) This invention relates to improvements in the suppression of surface ignition andreduction of octane requirement increase of leaded g'asolines in the operation of internal combustion engines. More particularly, the invention provides an improved motor fuel and an improved method for preparing such fuel.

Current emphasis on high compression ratios and other high performance design features in gasoline engines of the internal combustion type, has tended to raise not only octane requirement but has created a situation where knock from surface ignition, often referred to as preignition, has become a limiting factor in engine design and operation. Knock induced by surface ignition appears to be a result of the use of organo-lead compounds, and particularly tetraethyl lead, as the anti-knock agent in fuels of high performance value. When motor fuels United States Patent containing lead are burned in internal combustion engines, deposits consisting of carbonaceous material and lead salts are continuously formed in the combustion chambers. These deposits are harmful in that they increase the octane requirement of the engine by inducing knock and causing surface ignition.

Ithas been proposed to provide a leaded motor fuel with a neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon to minimize the tendency of deposits to promote surface ignition and increase octane requirement. This additive has proven very effective but it has been found that when diluting such a product so that it may be readily incorporated in gasoline the diluent seriously interferes with the effectiveness of the additive and in some instances the beneficial effect is completely nullified.

It is an object of this invention to provide an improved method of preparing a motor fuel for spark ignition-internal combustion engines which contains an organo-lead anti-knock compound and a neutralized, alkali-metalcontaining reaction product of a phosphorus sulfide and a hydrocarbon. Another object is to provide a method of incorporating a neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon in a gasoline mixture whereby the beneficial effects of the additive are not impaired. A more specific object is to provide a solvent for incorporating, in a motor fuel, the aforesaid neutralized reaction product, which solvent may be used in any desired amount Without deleterious eflects. A further object is to provide a solvent for the aforesaid neutralized reaction product which will further reduce octane requirement increase over that obtained with the neutralized reaction product itself.

Another problem encountered in high performance design engines using modern fuels is the build-up of deposits in the induction system of the engine. These deposits cause blockage of the passages in the induction system, such as in the carburetor idling bypass, which results in rough operation of the engine. The deposits also collect on the intake valve stem and interfere with its operation. In extreme cases the deposits restrict the flow of the fuel-air mixture which results in ineflicient operation of the engine. It is therefore another object of this invention to provide an additive for motor fuel to improve induction system cleanliness, anti-knock prop erties and surface ignition characteristics.

We have discovered that the above objects can be accomplished by providing a method of preparing a motor fuel for spark ignition-internal combustion engines which comprises the steps of adding to a gasoline mixture a minor amount of an organo-lead anti-knock compound, preferably tetraethyl lead, and a neutralized, alkali-metalcontaining reaction product of a phosphorus sulfide and a hydrocarbon which neutralized reaction product is di-. luted before incorporation with the gasoline mixture with a normally liquid hydrocarbon solvent comprising essentially polycyclic hydrocarbons having an initial boiling point of at least about 450 F. The neutralized reaction product is added to the fuel in an amount suflicient to give a mol ratio of phosphorus to lead in the range of from about 0.01 to about 2.0. The phosphorus sulfide is preferably phosphorus pentasulfide and the hydrocarbon can preferably be a polymer of a mono-olefin of less than 6 carbon atoms, which polymer has a molecular weight in the range of from about to about 50,000. The preferred alkali metal is potassium although other alkali metals such as sodium and lithium can be suitably employed. The polycyclic hydrocarbon solvent can contain any of the normally liquid polycyclics having a boiling point above about 450 F. such as, for instance, polycyclic aromatics, polycyclic naphthenes, polycyclics having both aromatic and naphthenic rings, 'alkyl substituted polycyclics and mixtures of the foregoing. Other hydrocarbons such as .parafiins may also be present in the solvent, however; the polycyclics are the essential component and should predominate.

' The motor fuel can contain tetraethyl lead at a concentration of from about 0.5 ml. to about 5 ml. or more per gallon. The concentration of tetraethyl lead can be varied as is usual with the engine and its use.

The motor fuels will preferably be gasoline but can be any other combustible liquid of suitable volatility commonly employed as fuel for internal combustionspark ignition engines, including parafiinic, naphthenic and aromatic hydrocarbons, isooctane and mixtures of isooctane with other suitable liquid hydrocarbons. The boiling point of such fuels should be in the range of from about 100 F. to about 500 F. and preferably in the range of from about F. to about 400 F. Such motor fuels may also contain anti-oxidants, stabilizers, dyes, anti-icing agents, lead scavenging agents and/or other compounds which are commonly employed in leaded motor fuels.

We can also provide, in accordance with our invention, an additive mixture which comprises essentially a normally liquid hydrocarbon solvent comprising essentially polycyclic hydrocarbons having an initial boiling point of at least about 450 R, an organo-lead antiknock compound and a neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon, the mol ratio of phosphorus to lead in the mixture being from about 0.01 to about 2.0. Suflicient polycyclic hydrocarbon solvent should be employed to obtain desirable fluidity. For example, the solvent can be employed in the range of from about 25% to about 95% or more based on the total weight of mixture. Although the solution of the. neutralized, alkali-metal-containing reaction product of a phosphorus sulfide and a hydrocarbon can be added to the motor fuel'separately from the organolead,it may be desirable to add it simultaneously therewith. The organo-lead compound is preferably tetraethyl lead. The conventional tetraethyl lead fluid contains small amounts of halo-hydrocarbon lead scavenging agents, dyes, hydrocarbon diluents, etc. but the phosphorus to lead ratio is based on the tetraethyl lead content thereof.

In the preparation of the phosphorus sulfide-hydrocarbon reaction product, the hydrocarbon is reacted with a phosphorus sulfide such 1 as P -P S P 8 or other phosphorus sulfides, and preferably phosphorus pentasulfide,,P S

The hydrocarbon constituent of this reaction is preferably a mono-olefin hydrocarbon polymer resulting from the polymerization of low'molecular weight mono-olefinic hydrocarbons or iso-mono-olefinic hydrocarbons, such as propylenes, butylenes and amylenes, or the copolymers obtained by the polymerization of hydrocarbon mixtures containing iso-mono-olefins and mono-olefins of less than 6. carbon atoms. The polymers may beobtained by the polymerization of these olefins or mixtures of olefins in the presence of a catalyst such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride orother similar halide catalysts of the Friedel-Crafts type and preferably have a molecular weight in the range of from about 125 Other preferred olefins'suitable for the preparation of the hereindescribed phosphorus sulfide reaction products are those having at least 8 carbon atoms in the molecule.

Essentially paraflinic hydrocarbons such as bright stock residuums, lubricating oil distillates, petrolatums, or paraflin waxes, can be used. There can also be employed the condensation products of any of the foregoing hydrocarbons, usually through first halogenating the hydrocarbons, with aromatic hydrocarbons in the presence of anhydrous inorganic halides, such as aluminum chloride, zinc chloride, boron fluoride, and the like.

Also contemplated within the scope of the present invention are the reaction products of a phosphorus Sulfide with an aromatic hydrocarbon, such as, for example, benzene, naphthalene, toluene, xylene, diphenyl and the like or with an alkylated aromatic hydrocarbon, such as, for example, benzene having an alkyl substituent having at least four carbon atoms, and preferably at least eight carbon atoms, such as long chain paraffin wax.

While the aforesaid hydrocarbon constituents of the phosphorus sulfide-hydrocarbon reaction product are all effective in accordance with the invention, it is not to be implied that all are necessarily exactly equivalent in their effectiveness. Although the function of the hydrocarbon is not completely understood, its primary purpose is to impart solubility, in gasoline, to the reaction product.

In general, the preparation of the phosphorus sulfidehydrocarbon reaction product in accordance with the present invention is carried out in the following manner:

The hydrocarbon, such as, for example, an olefinic polymer of the desired molecular weight, is reacted with from about 1% to about 50%, and preferably from about 5% to about of a phosphorus sulfide, e.g., P 5 at a temperature of from about 200 F. to about 600 F. in a non-oxidizing atmosphere, such as, for example, an atmosphere of nitrogen. The reaction is carried out for from about one to about ten hours or more, and preferably for about five hours. The phosphorus sulfide-hydrocarbon reaction can, if desired, be carried out in the presence of a sulfurizing agent such as elemental sulfur or a halide of sulfur. The reaction product obtained can, if desired, then be hydrolyzed at a temperature of from about200 F. to about 500 F., and preferably at a temperature of 300 F. to 400 F., by a suitable means, such as, for example, by introducing steam through the reaction mass. The hydrolyzed product containing inorganic phosphorus. acids formed during the hydrolysis can then be contacted with an absorbent material such as Attapulgus clay, fullers earth and the like at a temperature of from about 100 F. to about 500 F. and the treated, hydrolyzed product filtered to obtain a filtrate substantiallyfree of inorganic phosphorus acids and low molecular weight organic phosphorus compounds. I

The reaction product of a phosphorus sulfide; and a hydrocarbon, preferably treated in the above manner with or without hydrolysis and clay treating, is then neutralized with an alkali metal compound. Although it is not essential, the product is preferably diluted with an equal volume of a polycyclic hydrocarbon solvent, described hereinafter, before neutralization to facilitate mixing and handling. The neutralization step with an alkali metal is carried outwith a suitable basic compound such as the metal hydroxide, carbonate, oxide or sulfide, such as potassium hydroxide, sodium hydroxide, lithium oxide or the like. It is preferable, however, to use potassium or lithium hydroxide.

The basic alkali metal compound may be admixed directly with the phosphorus sulfide-hydrocarbon reaction product, dissolved in water or an alcohol-water mixture and then admixed therewith, or a slurry of the alkali metal compound in a polycyclic hydrocarbon solvent, described hereinafter, can be prepared and then admixed therewith. This reaction is carried out preferably in a non-oxidizing atmosphere at an elevated temperature from about F. to about 400 F.

After preparation of the alkali-metal-containing reaction product as described above, the mixture may be diluted with a polycyclic hydrocarbon solvent, described hereinafter, to obtain desirable fluidity. Without dilution the mixture is quite viscous and is not readily soluble in gasoline, thus it is desirable to add hydrocarbon solvent to obtain desirable fluidity. At about 10 volumes of solvent per volume of alkali-metal-containing reaction product, the mixture is readily soluble in gasoline and may be handled easily. Additional quantities of solvent over and above this amount can be used, however, from an economic standpoint this is generally not desirable. Smaller quantities of solvent can also be used, however, at concentrations of less than about 1:1 the mixture is quite viscous and diflicult to handle.

As pointed out hereinbefore, the normally liquid hydrocarbon solvent comprises essentially polycyclic hydrocarbons having an initial boiling point of atleast about 450 F. It is to be understood that the term polycyclic hydrocarbons includes polycyclic aromatics, polycyclic napththenes, polycylics having both aromatic and naphthenic rings, alkyl substituted polycyclics and mixtures of the foregoing. The solvent can consist entirely of such polycylic compounds or it can contain varying amounts of other hydrocarbons such as, for example, parafl'in hydrocarbons. The polycyclic compounds are the essential component of the solvent, however, and they should predominate. Pure polycyclic hydrocarbons having a boiling point above about 450 F. may be employed, however, this is generally not economically feasible.

Preferred polycyclic hydrocarbon solvents are those resulting from the solvent treatment of lubricating oils to remove aromatic compounds. The solvents employed in the treatment of lubricating oils to remove aromatic compounds are well-known to the art; thus, for example, phenol, chlorex, furfural, nitrobenzene, sulfur dioxide and others have been employed for this purpose.

Other preferred polycyclic hydrocarbon solvents are the bottoms fraction of the product resulting from the reforming of a naphtha or catalytic cycle oil or fractions thereof. These mixtures are predominantly polycyclic compounds boiling above about 450. Other mixtures which can be employed in accordance with our invention are those obtained from the product resulting in the hydrogenation of coal or from the coking of coal. Other sources of similar polycyclic compounds are wellk nown to those skilled in the art.

As pointed out hereinbefore, the neutralized, alkalimetal-containing reaction product of a phosphorus sulfide and a hydrocarbon can be dilutedwith a polycyclic hydrocarbon solvent and incorporated directly in a leaded gasoline, or it may be admixed with tetraethyl lead to form an additive mixture which may be incorporated in a motor fuel.

EXAMPLE! Butylene polymer (of about 750 mean molecular weight) was reacted with about 15% P S and 2% sulfur at a temperature of about 400 F. for five hours in an atmosphere of nitrogen. The product was then neutralized with about 9% potassium hydroxide dissolved in an equal amount of water at a temperature of about 400 F. Following neutralization the product was steamed at 400 F. for one hour and then stripped with nitrogen for about one hour at 400 F. to remove any remaining water. This product had a sulfur content of 1.16%, potassium content of 3.16% and a phosphorus content of 2.70%. The product was then diluted with about 10 volumes of a solvent extracted SAE 5 lubricating oil. l

' EXAMPLE H I The steamed and stripped, neutralized reaction product of Example I was diluted with about 10 volumes of a polycyclic hydrocarbon solv .nt obtained by extracting an SAE 5 lubricating oil with phenol. The extract (freed of phenol) had the following inspections:

Distillation range:

Initial B.P. F 650 90% point F 750 Viscosity:

210 F. 41.4 Specific gravity 0.950 Refractive index 1.5304 Total rings per molecule 3.18

Aromatic rings 1.17

Naphthenic rings 2.01 Percent of total carbon in rings r 62 Percent of total carbon in paraffins 38 The diluted, neutralized, alkali-metal-co'ntaining P S butylene polymer reaction products thus obtained were incorporated in a premium gasoline, containing 3 milliliters of tetraethyl lead per gallon, in an amount sufficient to give a mol ratio of phosphorus to lead of 0.13, and the fuels were evaluated for 165 hours in a single cylinder, four cycle, overhead valve, liquid cooled engine having a 2% inch bore and a 3% inch stroke 'with a displacement of 17.6 cubic inches and which is equipped with an integral jacket condenser for coolant temperature control and electric heaters in the base for oil temperature control.

Operating conditions were as follows:

Surface ignition rates were determined and also the octane requirement increase. As shown in Table I, such data were obtained using the base leaded fuel containing 3 cc. TEL/gal., and the same leaded fuel with the additives of Examples I and II at a concentration suflicient to give a mol ratio of phosphorus to lead of 0.13; the solvent concentration in the total fuel mixture was thus about 0.11%. The additive mixture was very fluid and dissolved readily in the leaded fuel at room temperature. Table I also includes data of the additive of Example I diluted with about 40 percent by weight of solvent ex- 6 tracted 5 W oil-used in amount to give approximately the same P/Pb mol ratio; this more concentrated additive mixture was less fluid and dissolved less readily in leaded fuel at room temperature, but when lubricating oil is employed as the solvent,.it is desirable to minimize the amount thereofin the motor fuel.

The test data in Table I show that using the lubricating oil solvent at low concentration provides an effective additive but that further dilution to obtain an additive mixture is more readily handled and easily dissolved in the gasoline results in a fuel which has no beneficial efiect upon surface ignition or octane requirement in crease. However, when employing a polycyclic hydrocarbon solvent in accordance with our invention (Example II) both octane requirement increase and surface ignition characteristics are improved even though large amounts of our solvent are employed.

Although the examples illustrate the effect of our additive mixture at a phosphorus to lead ratio of 0.13, we have observed that the ratio can be varied within rather wide limits and that by so doing the effectiveness with respect to either octane requirement increase or surface ignition maybe varied. Thus at lower ratios of phosphorus to lead in the defined range, surface ignition can be improved relatively while at higher ratios in the defined range greater improvement of octane requirement increase is obtained.

As mentioned before, our composition substantially lowers the amount of deposits formed in the induction system of internal combustion engines. To illustrate this advantage, union induction system deposits were determined. The test apparatus employed consists essentially of a steam-jacketed glass U-tube, one arm of which is indented much like a Vigreux fractionating column. The gasoline sample is sprayed into the upper end of the indented arm, where it flash evaporates in an ascending stream of warm air. Filtered atmospheric air is preheated in the other arm of the U-tube, flows up the indented arm, counter-current to the descending film of evaporating gasoline, and is withdrawn at the top. The gasoline sample is contained in a reservoir and flows by gravity from the reservoir through a flow meter to the fuel inlet nozzle. A 3,000 milliliter sample of the gasoline is evaporated, with close control of the flow rate, during exactly two hours. The air-fuel ratio in the column typically averages about 5.5 to 1. Following the evaporation, the gums are leached with hexane-heptane solvent, then dissolved in acetone. The acet'one is evaporated to dryness and the gum residue is weighed.

Data were obtained (Table II) using a commercially obtainable premium gasoline containing 3 ccs. of tetraethyl lead per gallon having a small amount of gum added thereto and the same fuel containing gum plus a sutficient amount of the additive of Examples I and H to give a mol ratio of phosphorus to lead of .016. For this induction system deposits test the additive was dissolved in 0.4 part by weight of the indicated hydrocarbon solvent rather than 10 volumes as shown in the examples. Thus, 0.01% by weight of an additive mixture containing 40% hydrocarbon solvent and 60% neutralized, alkali-metal-containing reaction product was added to a fuel containing 3 ccs.

of TEL. The gum incorporated with the leaded gasoline in these tests was obtained from unleaded gasoline which had been stored for substantial lengths of time at ambient temperature.

TABLE 11 5 Union induction system deposits As can be seen from Table II, theme of our additive mixture with a polycyclic hydrocarbon solvent in the range hereinbefore specified results in substantially less acetone soluble deposits in the induction system. The Q acetone soluble deposits are indicative of the type of deposits which interfere with normal operation of the engine as pointed out hereinbefore and, in particular, interfere with proper functioning of the intake valve. 7

Although only a potassium containing reaction product has been used in the foregoing examples, we have observed that the same beneficial elfect can be'obtained when employing lithium or other alkali metals.

Percentages given herein and in the appended claims are weight percentages unless otherwise noted; 3

While we have described our invention by reference to specific embodiments thereof, the same are given by way of illustration. Modifications and variations will be apparent from our description to those skilled in the art.

We claim:

1. An additive for gasoline for incorporating into gasoline an amount of tetraethyllead in the range of .5 to 5 ml. per gallon, which additive consists essentially of tetraethyllead, a phosphorus-containing reaction product prepared by reacting 1 to 50 percent of a phosphorus sulfide 40 with a butylene-polymer having a molecular weight in the range of 1 25 to 50,000 at a temperature in the range of 200 to 600 F. in a non-oxidizing atmosphere for at least one hour and thereafter neutralizing with potassium hydroxide, the amount of reaction product in the additive providing at least .01 mole but not more than 2.00 moles of phosphorusper mole of lead present in the additive, and a normally liquid hydrocarbon solvent which boils above 450 F. in which solvent polycyclic hydrocarbons predominate and constitute the essential component and which solvent constitutes on a weight basis about 25 percent to 95 percent of said additive.

2. A gasoline motor fuel for spark ignition internal combustion engines containing from about .5 to 5 ml. of tetraethyllead per gallon of gasoline, a phosphorus-containing reaction product prepared by reacting 1 to 50 percent of a phosphorus sulfide with a butyle'ne polymer having'a molecular weight in therange of 125 to 50,000 at a temperature in the range of 200 to 600 F. ina nonoxidizing atmosphere for at least one hour and thereafter neutralizing with potassium hydroxide, the amount of phosphorus containing reaction product providing at least .01 mole but not more than 2.00 moles of phosphorus per mole of lead of the tetraethyllead,'a-nd a normally liquid hydrocarbon solvent which boils above 450 F. in which solvent polycyclic hydrocarbons predominate and constitute the essential component and which solvent constitutes on 'a weight basis about 25 percent to 95 percent of the total weight of 'tetraethyllead, phosphorus-contain:

0 ing reaction product, and liquid hydrocarbon solvent.

References Cited in the file of this patent UNITED STATES PATENTS 2,066,234 Sloane et al. Dec. 29, 1936 2,534,217 Bartleson .Dec. 19., 1950 2,712,528 Hill 'et al July 5, 1955 2,726,942 Arkis et al. Dec. '13, 1955 2,794,714 Bartleson June 4, 1957 2,794,722 Bartleson June 4, 1957

Claims (1)

1. AN ADDITIVE FOR GASOLINE FOR INCORPORTATING INTO GASOLINE AN AMOUNT OF TETRAETHYLLEAD IN THE RANGE OF .5 TO 5 ML. PER GALLON, WHICH ADDITIVE CONSISTS ESSENTIALLY OF TETRAETHYLLEAD, A PHOSPHORUS-CONTAINING REACTION PRODUCT PREPARED BY REACTING 1 TO 50 PERCENT OF A PHOSPHORUS SULFIDE WITH A BUTYLENE POLYMER HAVING A MOLECULAR WEIGHT IN THE RANGE OF 125 TO 50,000 AT A TEMPERATURE IN THE RANGE OF 200 TO 600* F. IN A NON-OXIDIZING ATMOSPHERE FOR AT LEAST ONE HOUR AND THEREAFTER NEUTRALIZING WITH POTASSIUM HYDROXIDE, THE AMOUNT OF REACTION PRODUCT IN THE ADDITIVE PROVIDING AT LEAST .01 MOLE BUT NOT MORE THAN 2.00 MOLES OF PHOSPHORUS PER MOLE OF LEAD PRESENT IN THE ADDITIVE, AND NORMALLY LIQUID HYDROCARBON SOLVENT WHICH BOILS ABOVE 450* F. IN WHICH SOLVENT POLYCYCLIC HYDROCARBONS PREDOMINATE AND CONSTITUTE THE ESSENTIAL COMPONENT AND WHICH SOLVENT CONSTITUTES ON A WEIGHT BASIS ABOUT 25 PERCENT TO 95 PERCENT OF SAID ADDITIVE.