US2345296A - Liquid fuel composition - Google Patents

Description

Patented Mar. 28, 1944 Lr'omnFUEr. COMPOSITION Walter A. Schulze and Joseph Preston Lyon, Jr.,

Bartlesvllle, kla., a'ssignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application April 4, 1940. Serial No. 327,912

Claims.

This invention relates to a liquid 'hydrocarbon motor fuel composition, and to the method of preparing said composition. Mpre specifically, this invention relates to the preparation of special hydrocarbon motor fuels containing tetraethyl lead in stable solution therein.

There are certain types of motor fuels such as high-octane aviation gasolines which are manufactured and blended accordingito specifications so strict that the selectiongof suitable components for blending is limited to synthetic or naturally occurring substantially pure hydrocarbons. Such blends must have high octane rating, because the tetraethyl lead content is limited, and accordingly, the hydrocarbon constituents of the blend must have an excellent response to addition of antidetonant. Further, the olefinic or other unsaturated hydrocarbon content of the fuels must be almost nil, of the order of less than one per cent in order that the fuels be substantially free of gum and of susceptibility to gum formation. Also the absence of olefinic hydrocarbons is desirable because olefins contribute to excessive engine cylinder temperatures during combustion and are not very responsive to lead-alkyl antidetonant compounds.

Such fuels are satisfactorily blended only from natural or synthetic, high-octane aliphatic or cyclic paraflin hydrocarbons although certain carefully selected aromatic compounds such as toluene may be used in some instances. The resuiting blends of practically pure saturated hydrocarbons are substantially non-gum-forming and have an adequate response to the lead-alkyl antidetonant. From the standpoint of storage stability, the outstanding possibility of deterioration of such a fuel in storage is the loss of octane number caused by loss of antidetonant compound by precipitation from the fuel, and such deterioration is the subject of this invention.

It is an object of this invention to stabilize aviation gasolines which do not contain substantial amounts of highly unsaturated, gum-forming hydrocarbons such as olefins and diolefins and the like, and which contain an antidetonant.

Another object of this invention is to provide a stable solution-of tetraethyl lead in special motor fuels, composed of substantially non-gumforming saturated hydrocarbons with olefinic content of less than one per cent, which have a tendency to deposit the antidetonant as insoluble residues.

A further object of this invention is to we vent the separation or precipitation of leadalkyl antidetonant compounds trom substantially non-gum-forming hydrocarbon motor fuels which have a measurable tendency to precipitate said antidetonant compounds and thereby lose the antidetonant effect.

Other objects and advantages will become apparent from the following disclosure and discussion.

In the manufacture of very high octane motor fuels, such as to 100 octane number aviation gasolines, because of the limitation on tetraethyl lead addition the procedure usually includes the manufacture of synthetic isoparaflins. For example, such manufacture may include the polymerization of isobutylene to form isooctenes, followed by hydrogenation of the polymers to form isooctanes, with less than one per cent residual unsaturation.

These synthetic hydrocarbon fuels havingan octane number of to may then be blended with suitable saturated hydrocarbon stocks to meet the specifications governing volatility and vapor pressure. To such a blend is then added a quantity of an antidetonatlng agent such as tetraethyl lead calculated to result in an octane number within the desired range.

The gasoline stocks which are suitable for use in such blends are carefully selected and are usually limited to saturated hydrocarbon liquids such as light straight-run naphthas which may contain cyclo-paraffins and suitable fractions of natural gasolines which are predominantly aliphatic in nature, although certain non-gumforming aromatic hydrocarbons such as toluene may be used, providing such use does not infringe any specifications for the fuel. The selection of such stocks, mainly pure hydrocarbons, with only negligible amounts of unsaturates and other impurities, is necessary because the finished blends must meet very stringent specifications regarding acid heat tests, gum content and gum formation in storage.

The purity and inherent stability of fuels prepared by the above-outlined procedure, or the various possible modifications, is well illustrated by the following abstract of U. S. Army Specifications No. 2-92-A. The fuel must yield less than 6 milligrams of residue per 100 cubic centimeters, after evaporation of a portion of a 200 cubic centimeter sample which has been heated at 210 F. in contact with 35 square inches of steel surface for 5 hours under 100 pounds per square inch oxygen pressure/i A fuel passing such a test must certainly be judged substantially gum-free and non-gum-forming.

We have found that such fuels in spite of inch oxygen pressure purity, selected composition and inherent stability often exhibit a serious degradation; that ing agent such as tetraethyl lead often show a tendency to suffer the precipitation of insoluble residues from the tetraethyl lead under certain storage or test conditions such as the exposure to heat, oxygen and steel. same fuels, before'the addition of such an antidetonating agent, substantially lack the tendency to form gums, and do not contain appreciable quantities of olefins or dioleflns or the like which ordinarily cause, or contribute to the formation of gum.

* We have now discovered that the precipitation of lead compounds from liquid fuels of the type described which have a tendency to cause "or to allow said precipitation may be prevented by the addition to the leaded fuel of small amounts. of an efllcient anti-oxidant, or gum-inhibitor, such as are available in commercial form to the in- On the other hand, the v is, the finished fuels containing an antidetonatdustry and such as have been used heretofore only in fuels containing gum-forming hydrocarbons.

The function of the inhibitor is, in the light of-the foregoing 'description, not to prevent gum formation, since thehydrocarbon liquids of our composition are substantially non-gumforming. In some manner, which is-not precisely known to us, these added compounds are able either to maintain in their original form the solvents for the antidetonant or to stabilize directly the antidetonant compound and prevent its deterioration or chemical change.

The amount of inhibitor or anti-oxidant which we find effective in our composition is extremely small, being of the order of about 1 to 4 or more pounds of inhibitor per 1000 barrels of gasoline or in other terms between about 0.0001 and 0.002 per cent by weight of the fuel. These quantities are based on the'use-of anti-oxidants approximatel'y as effective as monobenzyl-para-aminophenol, a widely used gum inhibitor. With less eillcient anti-oxidants larger quantities may be required. The addition of the preferred quantity of anti-oxidant produces no deleterious effect on the fuel since other qualities are unimpaired.

Since it is common commercial practice to pur chase and use said inhibitors as solutions of varying concentrations in suitable solvents, it should be stated for the purpose of clarity that these preferred quantities are exclusive of the weight of such solvents or other material of like nature.

The means of adding the anti-oxidant to the liquid fuel may be any conventional method known to the industry, is generally just before or just of the tetraethyl lead composition, as may be convenient or desirable. After the fuel is thus blended, it .is found that the conditions which would formerly cause precipitation of lead compounds in the uninhibited fuel no longer do so. Thus, exposure to the conditions of the previously mentioned gum test (U. S. A'rmy No. 2--92'-A) no longer causes any precipitation of insoluble lead compounds from the gasoline.

The following examples of the eillcacy of our composition are included here, not [as limiting our invention, but to illustrate some of the possible benefits. Many other analogous modifications and uses of our process will b obvious tothose skilled in this art.

Components and finished blends, of aviation gasoline were prepared and heated to 210 F. in a glass-lined bomb under .100 pounds per square in contact with steel surface and the time of addition after the addition for 5 hours. The following observations were made:

3 cc. TEL/gallon.) l4 anti-oxidant(isobutylp amino phenol.

None Lead precipitate (dc- Isooctane base+20% creased oct. N0.)

pentane-free natural gasoline-Hi cc.. TEL/gallon.

Isooctane based-20% 0.00l5% Dupont No. No precipitate.

pentanc-iree nat- /9 anti xidant (nural gasoline+3 cc. butyl-p-aminophe- TEL/gallon. 1101). 100 octane fuel (with 0.0004% Dupont No. Do.

3 cc. TEL/gallon). l4 anti-oxidant (iso bult)yl-p-aminophcno In order to measure any corresponding efiect on lead content occurring with ordinary motor fuels containing cracked gasolines which range from 10 to per cent or more in unsaturation, induction period tests were made on several typical fuels. These tests included placing the sample of gasoline in a glass-lined bomb under 100 pounds per square inch oxygen pressure and heating the bomb at 210 F. until there was a rapid absorption of oxygen by the sample. After the test, the gasoline samples were examined, and while there was in some cases a resinous organic deposit, there was no evidence of substantial precipitation of lead residues. The results of these testsindicat that in ordinary cracked gasoline there is only negligible tendency to precipitate the antidetonant compound, whereas, in the case of pre dominantly saturated and substantially non-gumforming aviation gasolines, thelead-precipitating tendency is greatly magnified.

The inhibitors which we find mosteffective in our composition are monobenzyl-para-aminophenol and homologous substituted aminophenols such as are commerciailyavailable to the industry.

Further, we disclaim all benefits and previously disclosed effects of the use of said gum inhibitors for the prevention or reduction of gum formation in motor fuels containing larg amounts of cleflnic, dioleflnic and other unsaturated gumfcrming hydrocarbons and gum-forming impurities. We emphasize the fact that the fuels to which we add said inhibitors are of such character'as to of our. special fuel composition are sufficient to distinguish over ordinary gum-forming fuels containing gum inhibitors.

What we claimis: p

1. An improved aviation gasoline having an octane number above- 80, comprising essentially a non-gum-forming hydrocarbon fuelcontainin less than one perv cent by volume of oleflnic or diolefinic hydrocarbons, tetraethyl lead and an aminophenol of the group consisting of mono: benzyl-para-aminophenol, isobutyl-para-aminophenol, and normal lmtyl-para-aminophenol in 'an' amount equal to between about weight per cent of'the fuel asessentially the sole added material tending to inhibit decomposition and precipitation of said tetraethyl lead.

2. The method of preventing the precipitation be classified as substantially non-gum-forming, and that the qualities and uses a of insoluble lead compounds which tend to precipitate from a blend of tetraethyl lead antidetonant in essentially non-gum-forming aviation gasolines containing less than one per cent by volume of oleflnic or other unsaturated hydrocarbons, which comprises adding to such a gasoline a small amount of an aminophenol of the group consisting 'of mono-benzyl-para-aminophenol, isobutyl-para-aminophenol, and normal butylpara-aminophenol as essentially the sol added material tending to prevent the precipitation of the antidetonant compound.

3. The method of stabilizing aviation gasolines having an octane number above 80 and composed of essentially non-gum-forming hydrocarbons, with an olefinic or other unsaturated hydrocarbon content of less than one per cent, and tetraethyl lead which comprises adding to such a gasoline between 0.0008 and 0.002 weight per cent of monobenzyl-para-amino-phenol as essentially the sole added material tending to inhibit decomposition and precipitation of said tetraethyl lead, whereby the precipitation of oil-insoluble lead compounds is inhibited.

4. A motor fuel composition, comprising essentially hydrocarbons in the boiling range of motor fuel and of such a character as to be classified as substantially non-gum-forming, an antidetonant compound which tends to decompose and b precipitated when in admixture with such hydrocarbons under normal conditions of storage and handling of aviation motor fuel, and a small amount of an aminophenol of the group consisting of monobenzyl-para-aminophenol, isobutyl-para-aminophenol, and normal butyl-paraaminophenol as essentially the sole material tending to inhibit said decomposition and precipitation of said antidetonant.

5. A motor fuel composition, comprising essentially hydrocarbons in the boiling range of motor fuel and of such a character as to be classified as substantially non-gum-forming, an antidetonant compound which tends to decompose and be precipitated when in admixture with such hydrocarbons under normal conditions of storage and handling of aviation motor fuel, and a small amount of monobenzyl-para-animophenol as essentially the sole material tending to inhibit; said decomposition and precipitation of said antidetonant.

6. A motor fuel composition, comprising essentially hydrocarbons in the boiling range of motor fuel and of such a character as to be classified as substantially non-gum-forming, tetraethyl lead which tends to decompose and be precipitated when in admixture with such hydrocarbons under normal conditions of storage and handling of aviation motor fuel, and a small amount of an aminophenol of the group consisting of monobenzylpara-aminophenol, isobutyl-para-aminophenol,

and normal butyl-para aminophenol as essentially the sole material tending to inhibit said decomposition and precipitation of said tetraethyl lead.

7. A motor fuel composition, comprising essentially hydrocarbons in the boiling range of motor fuel and of such a character as to be classified as substantially non-gum-forming, alead-alkyl antidetonant compound which tends to decompose and be precipitated when in admixture with such hydrocarbons under normal conditions of storage and handling of aviation motor fuel, and a small amount of an aminophenol of the group consisting of monobenzyl-para-aminophenol, isobutylpara-aminophenol, and normal butyl-paraamino phenol as essentially the sole material tending to inhibit said decomposition and precipitation of said antidetonant.

8. A motor fuel composition, consisting essentially of paraflin hydrocarbons in the boiling range of motor fuel and containing less than one per cent by volume of unsaturated hydrocarbons, a lead-alkyl antidetonant compound which tends to decompose and form precipitate when in ad mixture with such hydrocarbons under normal conditions of storage and handling of aviation motor fuel, and a small amount of an aminophenol of the group consisting of monobenzylpara-aminophenol, isobutyl-para-aminophenol, and normal butyl-para-aminophenol as essentially the sole material present tending to inhibit said decomposition and precipitation of said antidetonant.

9. A motor fuel composition, comprising essentially hydrocarbons in the boiling range of motor fuel and of such a character as to be classified as substantially non-gum-forming, a lead-alkyl antidetonant compound which tends to decompose and be precipitated when in admixture with such hydrocarbons under normal conditions of storage and handling of aviation motor fuel, and a small amount of isobutyl-para-aminopheno1 as essentially the sole material tending to inhibit said decomposition and precipitation of said antidetophenol as essentially the sole material tending to inhibit said decomposition and precipitation of said antidetonant.

WALTER A. SCHULZE. JOSEPH PRESTON LYON, JR.