US2608476A - Color stable gasoline composition - Google Patents

Description

Patented Aug. 26, 1952 COLOR STABLE GASOLINE COMPOSITION Barney R. Strickland, Westfield, N. J assignor to StandardOil Development Company, a corporation of Delaware No Drawing. Application January 26, 1949,

' Serial No. 73,013

1 V This invention relates to a gasoline composition of good color stability. More particularly the invention concerns a gasoline composition consisting of a virgin or parafiinic base stock containin a halogenated hydrocarbon, a phenylenediamine inhibitor and a small amount of cyclohexylamine, or its derivatives. This composition is substantially color stable when exposed to light by virtue of the colorstabilizing effect of the cyclohexylamine.

As indicated, this invention concerns a specific fuel composition Whichwithout the use of cyclohexylamine, as herein disclosed, is normally color unstable. The fuel base stocks embraced within the scope of this invention are broadly any. parafiinic or virgin stock, any hydrogenated stock, or any stock containing substantially no olefins. Within this class of fuel base stocks fall the alkyl'ate types of fuels produced by thereaction of isoparafiins and olefins so as to provide a fuel having substantially no oleflns, and hydrogenated polymer types or gasolines formed by the polymerization of low. boiling olefins followed by hydrogenation to form hydrocarbons boiling" in the gasoline boiling range. The invention does not have application to any hydrocarbon compositions containing substantial quantities of olefins. Thus the invention does not have application to gasoline stocks produced by cracking procedures or by any other refinery process which causes the gasoline to have an appreciable olefinfcon'tent unless further processed to eliminate the olefins. l I As a further limitationoffthe composition of this invention, it is necessary that the fuel contain halogen compounds. In its broadest sense the halogen compound can be present in any form although in a practical sense the halogen compound is normally usedjin agasoline as a lead scavengingagent. Suitable lead scavenging agents are, generally speaking, any halogenated hydrocarbons, as this class of compounds has the property of being reactive with lead antiknock agents in the gasoline to yieldyolatile lead compounds which can beevacuated from the engine. As the name suggests, lead scavenger agents are employed to decrease lead deposits in an engine and other undesirable effects otherwise resulting fromthe'presence of lead anti-knock agents. As the present time [the scavenging agents which are employed commercially are mixtures of ethylene dibromide and ethylene dichloride, although many other scavenging agents can be employed such as brominated Cs Cs aromatics, mono-, di-,-and til-halogenatedparaffins,

this invention are fuel compositions containing 1 Claim. 01. 44--69) halogenated compounds, and specifically containing halogenated hydrocarbons used as lead scavenging agents in conjunction with lead antiknock agents. Again the anti-knock agent to be employed may be any of the lead alkyl compounds normally employed as lead scavening agents. While tetraethyllead is the anti-knock agent ordinarily employed, if desired the agent may be tetramethyllead, trimethylethyllead, dimethyldiethyllead, methyltriethyllead, triethyln-propyl lead or other alkyl lead compounds.

This invention is not limited to compositions containing any particular proportion of halogenated compounds or of lead anti knock agents. However aviation gasolines, generally contain quantities of tetraethyllead upto 4.6 ml. tetraethyllead per gallon together with one theory of ethylene dibromide; one theory being the amount of ethylene dibromide which would completely react with all of the lead present. Automobile gasolines generally contain quantities of tetraethyllead up to 3 ml. per gallon together with one theory ethylene dichloride and 0.5 theory ethylene dibromide.

The compositions of this invention also contain a specific class of anti-oxidants; this class of anti-oxidants is the phenylenediamines and particularly the N,N-dialkyl-p-phenylenediamines. Suitable phenylenediamines which are, or may be, employed are N,N-di-sec-butyl-pphenylenediamine and N,Ndi-n-butyl-p-phen ylenediamine. Generally gasolines contain up to about four pounds per-50 00 gallons of the antioxidant.

So far as is presently known this invention has no application to compositions containing antioxidants other than those selected from the class of phenylenediamines.

The color stabilizing agent of this invention is cyclohexylamine, or derivatives of this compound such as derivatives having an alkyl group or groups on either the carbon atoms or on the nitrogen atom. An example would be N-methylcyclohexylamine. Such derivatives havin alkyl groups containing one to eight carbon atoms may be used. The quantity ofcyclohexylamine or its derivatives to be employed is about 0.05 to 0.2 pound per 5000 gallons of gasoline composition, or about 0.0002 to 0.0006 weight percent.

As described, therefore, this invention relates to non-olefinic hydrocarbon fuel compositions containing phenylenediamine anti-oxidants and containing halogen atoms normallypresent in the form of lead scavengers together with lead anti-knock agents. In order to render this composition color stable, a small amount of cyclohexylamine is mixed with the composition. By

' dered substantially color stable.

ascends sition of this invention is particularly adaptedfor use in gasoline pumps having transparent bowls. As will be disclosed, a composition of the nature indicated not containing cyclohe'xylamine is normally subject to rapid and marked coloration generally causing the gasoline to have a pinl:

color. Discoloration apparently is due to the action of sunlight on the composition, as heating the gasoline does not cause this discoloration.

is theorized that light causes a photochemicalreaction of the halogen present in the composition with the phenylenediamine inhibitor. It is probable that sunlight causes release of halogen atoms from the scavenging agent which then combine with the inhibitor to form the pink coloration, or more precisely to form a pink precipitate which is visually apparent. Upon analysis it has been found that this pink precipitate contains 37.1% bromine content when the gasoline composition contained N,N-di-sec butyl-p-phenylenediamine and ethylenedib'romide as the scavenging agent. Insofar as the combination of one atom of bro mine with one molecule of the inhibitor would result in a bromine content of"26.7%, and the combination of two atoms of brominewould give a bromine content of 42.1%, it appears that the precipitate contains-almost two atoms of bromine per'molecule of the inhibitor. v

In order to fully understand the nature of this invention and to appreciate the scope of the invention, the following data and examples are presented. 'In'orde'r to determine the source of the pink coloration encountered in compositions of the general nature described, a series of tests were made employing-compositions of varying nature. Thus the compositions tested contained base stocks of varying kinds, contained different antioxidantspcontained different color dyes, and contained different potential color change inhibitors. Presen'ted in Table I below are a series of tests which establish that the undesirable color instability which may arise is not due to dyes which may be present in the gasoline.

1 Similar data obtained with virgin naphtha. 1 Blue Commercial Ethyl fluid containing a blue dye and l theory of EtBr; based on pure TEL.

- 3 II.)v TEL fluid containing a yellow dye and 1 theory of EtCl; plus 0.5 theory EtBr; based on pure TEL.

- The first composition tested, as indicated in Table I, was an alkylate gasoline base stocli having a boiling range of about to 350 F., and having been obtained by reaction between isobutylene and isobutane in the presence of sulfuric acidcatalyst at about 60 ,F. This alkylate was initially clear and Water white.

- After exposing the alkylate to the action of sun light for three hours, it was found that the color did not change, and that the alkylate remained clear and unco-lored;

The composition (b) indicated in Table 1 consisted of thisalkylate plus 4.6 ml. per gallon of a commercial tetraethyllead fluid normally used in aviation gasolines. This tetraethyllead fluid is colored for identification purposes with a blue dye of an unascertained composition and contains one theory of ethylene dibromide as the lead scavenging agent. In other words the tetraethyllead' fluid contains an amount of ethylene dibromide suflicient to stoichiometrically react with the lead present. By virtue of the blue dye oontained in the 'te'traethylleadlfluid the composition (1)) initially had a blue coloration. After exposure to sunlight it was found that the coloration of the gasolinehad not changed, and that the color oithegasoline remained-the same blue;

Composition (0) of 'Table'I 'was'the valkylate identified plus 4.6 frrilflpe'r gallon or "the blue tetraethyllead fluid employedfin com osition (1)) plus '1 pound of N',l l'-disec-'butyl-'pphenylenediamine .per' 500 .gallons of "composition. Againthe initial color of composition (cl was blue due to the blue dye present in the tetraethyllead fluid. However, "after exposing the composition to sunlight a cjolorchange was observed. The color apparently resulted-from pink color bodies in combination with'the blue dye to yield an apparent purple .color. .It is :apparent from these examples, that is, the testsof compositions (a), (b), and .(c "of Table I, that the blue dye employed 'in'the commercial tetraethyllead fluid'us'ed'was not'responsibie for the discoloration of the alkylate on'exposure tosunlight. In'or'der to 'determineif "the inhibitor -N,N'-di-sec-butylap=phenylenedianiine was re sponsible for this "efiect, the compositions (d), (e),and (ffwerethentested. 0 V p The composition 1d) consisted of th e alkylate plus .1 pound of theinhibitor,N;N di sec5buty1 p-phenylenediamine; per 5000 gallons 'OtfilkYl ate. It was found thatthe lnitial -co lor :ofcomposition (d) was clear-and uncolored'and that no color change occurredafter BXPOSUTEJJO'fSHD- light.

However as "shown by the-test of composition (6) in Table I, employing the composition (21') to whichwas 'added one dropper- 100 cos. of

ethylene dibromide, it was found that while the initial color of' composition e)' was elea n'd,

uncolored, a, pink ;coloration developed after ex! posure to sunlight:

As a furthertest, composition e) was mixed with 4 m1. per-gallon of a yellew tetraethyllead fluid {to obtain composition '(f) T indicated inthe table. The yellow ttraethyllead eiriployed was again i a commercially prepared lead iii id for use in automotive gas'olines an'd contains Tan dinidentified yellow "dye to id'elntify" the fluid,

gether with one theory bf J etliy andOZS theory 'of ethylene dib k I the tetraethyllead contentef th n d. itiwa's found that 'the co iiposition iil gh Jan initial color which was lyellowish duejto the dye 'employ'ed, and it was foun'd" thatfafter exposure to sunlight a color change occurred whi'ch afgain appeared to b QJd HB to'the presence of pin]; color bodies which resulted inan over-all color which was" more; or'less orange. Again, therefore, a'colorchan'ge was notedin an alkylate composition containing theinhibitor N,N'-disec butyl-p-phenylenediamine and a halogen compound; In order to entirely eliminate the possibility that this color, change was due to change inthe color of the dye present in the lead fluid, the composition (9) was prepared.

Composition (g) consistedof the alkylate plus 4 nli-pergallon oi the tetraethylleadfiuid employedin composition (f) [In other words coinposition (g) corresponded to composition (9) ex cept that the inhibitor N,N-di -sec-butyl-pphenylenediamine was not present. It was found that the initial color of composition (9) was yellow and that no color change occurred after exposure to sunlight. I

From tests of the nature indicated" in Table I it was established that the pink coloration encountered in gasolines exposed to sunlight is not due to the discoloration of dyes present in the gasoline, such as the yellow and blue dyes commercially utilized a in tetraethyllead fluids. Further experiments were conducted of the same nature as indicated in Table I utilizing virgin naphtha stocks rather than the alkylate employed in Table I. Again it was found that data were obtained corresponding to those presented for the alkylate compositions.

Insofar as the data of Table I indicates that the inhibitor employed is responsible for the objectionable pink discoloration encountered, a series of tests were conducted in which a variety of inhibitors other than a phenylenediarnine consisted-oi virgin naphtha base stocks containing tetraethyllead fluid containing ablue dye. The virgin naphtha employed was a low sulfur virgin naphtha-having a boiling range of about 200 to 350 "F., 4 ml. of the tetraethyllead fluid were employed per gallon, and theiiiuid utilized was a; commercial fluid colored 'with a blue dye containing an addition to the lead tetraethyl and the blue dye one theory of ethylene dibromide. As indicated-by compositionia) of Table II,';t his compositionhad an initial blue color which was unaltered upon exposure tosunlight. j

The test of composition (1)) indicates that when composition. (a) was mixed with 1 pound per 5000 gallons of N,N-di-sec butylp phenylenediamine; while the inhibitor did not changethe initialblue color of the 'gasolinediscoioration did occur afterfexposure to sunlight, resulting in a purplishtingeinthe gasoline. ;As represented by compositions c), (d) and (e) of Table II, this discoloration was not encountered when employing normalabutyl-para-aminophenol, isobutylparaeaminop'henol or 2,6-di-tert-butyl-4-methylphenol.

The data of Table II, therefore, together with that of Table I, substantiates the fact that the pink coloration developed in the compositions tested was due to the combination of non-olefinic naphtha, a phenylenediamine inhibitor, and a halogen compound.

Further experiments were then conducted employing base stocks other than substantially saturated parafilnic stocks. In particular the stock employed was one containing a substantial proportion of cracked gasoline as indicatedin Table III.

TABLE III Effect of inhibitors on the sunlight stability of gasolines In Direct Sunlight, Hrs. Gasoline Initial r I Gasoine A+2 ml. TEL Uninhib- Orangeh Crange; Orange Orange.

1 8 +2, 6-di-tert-butyl+methylphenol, -.do. ..do -do Do.

2 lbs/5000 gal. +N, N-di-sec-butyl-p-phenylene-di- -.do. do -l -do Do.

amine, 2 lbs/5000 gal. Virgin Naptha+4 ml. TEL 2 Unhib- Blue.. Blue... Blue, Blue,

lted. Slightly Slightly Cloudy Cloudy. +2, o-di-tert-butyl-i-methyl-phenol, .do.. -do... -do Do.

2 lbs/5000 gal. +N, N-di-sec-butyl-p-phcnylene-dido Pink... Pink Pink.

amine, 2 lbs/5000 gal.

1 Fluid contained ethylene dichloride and ethylene dlbromide and orange dye. 2 Fluid contained ethylene dibromidc.

Blue commercial ethyl fluid containing a blue dye and one theory of ethylene dibromide based on pure TEL.

It will be observed that the compositions tested For comparative purposes, gasoline A containing cracked constituents and being a commercial production motor gasoline was tested together with a virgin naphtha. It was found that gasoline A was initially orange, and remained orange after 3%; hours of exposure to direct sunlight. Furthermore, this gasoline showed no color change after exposure to sunlight when IN,N'-disec-butyl-p-phenylenediamine and when 2,6-ditert-butyl-4-methy1phenol were added to the gasoline. On the other hand the virgin naphtha gasoline tested was initially blue and developed no color change on exposure to sunlight either when uninhibited or when containing 2,6-di-tertbutyl-4-methylphenol. However, when the virgin naphtha gasoline contained the phenylenediamine inhibitor, a pink coloration did develop in the gasoline when exposed to sunlight for a period of one-half hour, or longer. It is, therefore, apparent from the data of Table III that the pink discoloration developed when employing a aeoaeve V phenylenediamine, inhibitoronly develops when the gasoline base stool; contains substantially no olefins. This is a logical result in view of the probable mechanism of. they discoloration as formerly stated. If, as theoriaed, the coloration is due to the photochemical reaction of halogens with N,N'-di-sec-butyl-p-phenylenediamine, it is possible that the presence of olefins would prevent the reaction -ofhalogens with the inhibitor and permit a preferential reaction of the halogens I Withthe olefins. As statedtherefore. the s line compositions embraced in this invention are gasoline base stocks containing substantially no olefinic constituents.

As presented, therefore,- from the .data of Tables I, II ancl III, it-appears that the objectionable pink discoloration which develops upon exposure to sunlight of virgin naphtha or nonolefim'c compositions, is due'to the discoloration of N,N-di-sec-butyl-p phenylenediamine on reaction with halogen compounds. In order to determine suitable compounds to inhibit this discoloration, a series of tests were then conducted as reported in Table IV, employing a variety of 7 possible color stabilizers.

TABLE IV 7 Color After Alkylate+4 ml. Blue TEL/gal.+1 lb. N',N-.dij-scc- .LHour butyl-p-pl1enylenediamlne/5#'M gal. Sunlight Exposure a. As'is Pink.

b. +0.1 lb. cyclohexylamine Blue.

0. +0.42 lb. cresylic acids Purple 2. +0.42 lb. n-butyl-p-aminophenol Do.

I. +0.84 lb. n-butyl-p-amiuopbenol.. Do.

9. +0.42 lb. lecithin Do.

It. +0.84 lb. lecithin Do.

1'. +0.42 lb. cyclohexylamine Blue.

j. +0.84 lb. cyclobexylamm Do.

k. +0.21 1b. cyclohexylamin Do.

1. +0.42 lb. tributylamine. Purple m. +0.42 lb. pyridine Do.

at. +0.42 lb. phenol Do.

0. +0.42 lb. alphs-naphthylamine Do.

p. +0.42 lb. naphthenlc sci Do.

g. +0.42 lb. aniline Do.

1. +l.2 lb. alpha-naphthol D0.

s. +0.42 lb. t-butyl catechol Do.

i. +0.421b. pyrogsllol Do.

V The composition tested was alkylate A of Table I with 4 ml. of .tetraethyllead per gallon and one pound per 5000 gallons of N,N-di-sec-butyl-pphenylenediamine. This composition originally had a blue color due to the presence of blue tetraethyllead fluid dye, but after exposure to sunlight for 1 hour, pink color bodies developed in the gasoline as indicated by marked color change. Reported in tests (1)) through (t) of Table IV are the results of combining the compounds indicated with the alkylate containing the tetraethyllead fluid and phenylenediamine. It will be observed that of all the compounds tested none of them, with the exception of cyclohexylamine was successful in stabilizing the color of the gasoline when exposed to sunlight.

Having now fully described this invention, what is claimed is:

A parafiinic base gasoline composition containing 0 to 4.6 milliliters per gallon of tetraethyl lead, about one to one and one-half theories of a halogenated hydrocarbon lead scavenging agent, based on tetraethyllead, a quantity of N,N'-di-sec-butyl p phenylenediamine greater than 0 and less than about four pounds per 5000 gallons. and about 0.05 to 0.2 pound per 5000 gallons of cyclohexylamine.

BARNEY R. STRICKLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,111,307 Bartram Mar. 15, 1938 2,436,838 Von Bramer Mar. 2, 1948 2,498,630 Thompson Feb. 28, 1950