US 2850368 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
nited States Patent GASOLINE COMPOSITIONS Byron M. Vanderbilt, Westfield, John P. Thorn, Union, and George E. Serniuk, Roselle, N. J., assignors to Essa Research and Engineering (Zompany, a corporation or Delaware No Drawing. Application April 27, 1955 Serial No. 504,343
Claims. (Cl. 4456) This invention relates to an improved gasoline composition and more particularly to a gasoline containing substantial amounts of butanes and butenes and a mixture of isopropyl and secondary butyl alcohols.
it has been known in the past to include minor proportions such as about l2.5% of isopropyl alcohol in gasoline forthe purpose of imparting anti-stalling properties by the prevention of carburetor ice formation. This property is particularly valuable for fuels used in operating internal combustion engines during cold, humid weather.
One disadvantage of employing small proportions of isopropyl alcohol has been its tendency to increase the vapor pressure of the gasoline composition in which it is included. Consequently, in order to produce a gasoline containing isopropyl alcohol which would be of sufliciently low vapor pressure as not to have an undesirable vapor-lock tendency, it has, been found necessary to decrease the concentration of volatile hydrocarbons such as butanes and butenes. Such a decrease or backing-out of butanes is highly undesirable from an economic standpoint, since these highly volatile fractions are relatively plentiful in modern refinery operations and possess high octane characteristics.
The effect of small quantities of isopropyl alcohol on the vapor pressure of gasoline is somewhat unexpected. Isopropyl alcohol has a Reid vapor pressure of 1.9 p. s. i. and is miscible with gasoline in all proportions. Gasoline normally has a Reid vapor pressure of 7.15 p. s. i. so that the addition of a soluble component of lower vapor pressure would be expected to effect a net vapor pressure decrease. Actually, an abrupt vapor pressure increase occurs upon the addition of l4% by volume of isopropyl alcohol. One possible explanation of this anomaly is that the isopropyl alcohol molecules, which are known to exist as dimers or higher polymers because of co-ordinated valences, are broken down into individual molecules on being highly diluted by a nonpolar medium such as gasoline. The individual alcohol molecules would be expected to exert a much higher vapor pressure than the polymer existing when the alcohol is in pure or highly concentrated form.
The content of butanes in gasoline generally varies between about 4% to about 20% by volume, depending on the season during which the gasoline is to be used. Summer grade gasoline intended for use and storage-during warm weather should be of the lowest volatility, having a Reid vapor pressure of about 7 to 10 p. s. i. and a C content of 48%. Spring grade fuels are more volatile, having a Reid vapor pressure of 11 to 12 p. s. i.
and containing about 9-12% C hydrocarbons, while winter gasolines, which are the most volatile, have a Reid vapor pressure of 13 to 15 p. s. i. and a C; content of l318%. Since the present invention makes it possible to retain substantial amounts of butanes in the gasoline while adding an effective amount of isopropyl alcohol, and, in some cases, to actually increase the butane ice content without raising volatility, the greatest advantages are to be gained in its application to the volatile winter grade gasoline. However, the present invention may also be used in preparing less volatile spring and summer grade fuels.
It has now been found that by the inclusion of small percentages of secondary butyl alcohol into gasoline fuels containing isopropyl alcohol, the undesirable vapor pressure rise usually associated with the presence of isopropyl alcohol can to a large extent be alleviated and in some cases a gasoline of overall reduced volatility produced, so that additional butanes may be included without adversely affecting the vapor-lock characteristics of the fuel. It may be that this unexpected efiect is the result of re-association of the isopropyl alcohol molecules in the gasoline blend due to the addition of butyl alcohol. This explanation is presented as a hypothesis only.
It is an object of the present invention, therefore, to provide a gasoline fuel composition containing substantial amounts of butanes and at the same time possessing desirable anti-stalling characteristics and having sulficiently low vapor pressure as not to cause undesirable vapor lock when used in internal combustion engines.
It is a further object of this invention to provide a gasoline composition containing isopropyl and secondary butyl alcohols in which the fuel has improved octane rating characteristics.
A still further object of this invention is to provide a stable motor fuel containing isopropyl and secondary butyl alcohols having satisfactory power output characteristics when used in internal combustion engines.
These objects, as well as others which will be in part pointed out specifically and in part apparent from the subsequent description, are attained by providing a gasoline composition containing mixtures of from about 2 to 12% by volume of a blend of isopropyl and secondary butyl alcohols in which the ratio of isopropyl alcohol to secondary butyl alcohol is preferably from about 1:1 to about 1:3.
In the past, it has been customary to evaluate the volatility of hydrocarbon mixtures such as gasoline in terms of so-called Reid vapor pressure. In measuring the vapor pressure of gasoline blends containing isopropyl alcohol, the introduction of either water or water saturated air into the system may seriously affect the total vapor pressure. In the regular Reid vapor pressure method for an all-hydrocarbon gasoline in which a water phase is present, the two immiscible liquids exert additive vapor pressures. However, when a water-soluble material such as isopropyl alcohol or secondary butyl alcohol is present, the distribution of such a component between the water and gasoline phases may have a pronounced effect on the total vapor pressure. Furthermore, in making up blends of gasoline with such compounds as alcohols, the mechanical loss of some of the butanes prescut is difiicult to avoid, thus seriously afiecting the vapor pressure of the final compositions. In view of this, a more exact method of measuring vapor pressure has been developed, and since the results of a number of tests utilizing the vapor pressures thus obtained are set forth in the ensuing description, the special apparatus and method of operation used will be described somewhat in detail. All of the vapor pressure data presented in the ensuing description for gasoline-alcohol blends are based upon this refined method as described below. When Reid vapor pressures are employed, they will be specified as such. It has been found that the Reid vapor pressures are generally proportional to those vapor pressures determined by the method to be described, so that an increase in vapor pressure produced by a particular combination of alcohols in a gasoline would also reflect an ahydrocarbon in,;the, PICSEIICQOf water. ;components-are mutually insoluble, they. exist as, separate --;ph ases'and, consequently, the vapor pressures of the two components are additive. the-hydrocarbon can be obtained by applying the appro- "ass-ease The.,apparatus.employed,for the-.vaponpressure det rminations .comprisedz'a metal jacketed Seltzer. ,b'Qttle .o .abopt.1 3 O ml. capacity fitted with ajspecial adapter carrying, a gauge. reading from 0. to 15 p. s. i. pressure and a self-sealing rubber diaphragm assembly 'through =which.successive samples couldbe withdrawn from, or ,aldtledv to, a-single charge .of gasoline by; means of a hypodermicneedle. .A :calibrated blow-case was used to introducethe original sample into the bottle (or the bomb, as it may.be.called)-against a dry nitrogen atmosphere.
- :A constant temperature: water; bath fitted with -an, elec- Jtronically controlled immersion heater and an air-driven stirrer-was used to maintain the temperature in the bomb constant at IOOLF.
qlBeforeeach determination, a record was made of the y rqom -temperature, barometer reading and. initial temperature of the bomb; The bomb was sealed at a pressure of one atmosphere after being thoroughly flushed ,withdrygnitrogena It wasthen heated at 100 F. to ,equilibrium. pressure with respect to the room and the pressure was recorded in p. s. i. g. If the observed pres- :sure corresponded to the pressure calculated due to temperature differential, the bomb was considered in. suitablec ondition for use; It was then cooled in ice water and-a 265 mlrsample was-introduced intothe bomb from v the calibrated blow case. The sample was charged against .the nitrogen atmosphere in the bomb. The bomb was then placed in the 100 F. bath and readings were taken 7111, accordance with the procedure well known in the Reidmethod. V g I 7 -Equilibrium pressure was assumed when three successive five-minute periods gave the same reading. Blends of the gasoline were then made in the bomb by .introducing'a-calculated amount of alcohol through the v.rubber diaphragm bygmeans of a hypodermic needle.
- Before each addition, an equivalent volume of gasoline ,91 blend was first removed from the charge in order ,to
=-maintain; a constant volume in .the bomb. The, direct reading in p. s.,-i. g. was observed on thegauge and observed values were corrected for-initial temperature -difierent-ial and compressibility of the nitrogen: These :values, as stated before, are close to the true vapor pressures-of the gasolines'and generally comparable to Reid 1vaporpressure-readings, although they are believed to be considerably more accurate.
The conventional Reid method for determining vapor .-,pr ess u res-.;of: petroleum, products, ASTM jdesignation .13 323, Federal specification 1(\ '/'.Li-79l) method: 1201, =is&;based on-the measurementof the. .Vapor pressure of Thus the vapor pressure of priatecorrection for the vapor pressureof water; However, ifthis method and procedure, are. applied to a sys- -tem comprising a hydrocarbon, water, and, a third,
mutually soluble component such as a lower. aliphatic alcohol, the vapor pressure will be in'error, since the -vaporpressures will no longer be additive. The water ,present will be: distributed between a'phase containing the majorportion of the water, the mutually soluble component, and some hydrocarbon, and a phase containing ..the-.major part of the hydrocarbon, mutually soluble com- .ponent, and water. Or, if there is a suflicieut propor- -tion of the mutually soluble alcohol added, it will 'solubilize the water and hydrocarbons tovgive onephase.
" The existence of such phases is dependent uponthe water content, which in the Reid method is indeterminant.
Thus the true vapor pressure of a hydrocarbon blended with a water-soluble component cannot be measured accurately by the Reid method.
Since thejtwo 1 8:%;., .-F 136 3% -F 139 .10% 11- 143 148% 9F 23g 42% r F 240' F 242 38%,.-. ".F 351 2% ,-F -,356 297%" ;F 361. Percent recovery i 97.0 :Percent resid 1 0 Pereentloss 2 G a y AlI. V, 58.9 Reid vapor pressure .'.L 9.7
v the tollowing percentages of theiindicated additive were The present method described measures the vapor pressure of the strictly dry components in a dry, inert atmosphere. This method also provides for the introduction to, or removal of samples from, a single charge of gasoline, a feature which minimizes sample errors due to opening of the bomb whencharging due to loss of low boiling hydrocarbons during this process.
-,In,preparing-,gasoline nigrtures in accordance with the even m ler. afi ut t less a l t f rolumeiimy be employed by gl e usion ,of a small quantity'of secondary. butyl alcohol n the fuel. This will be illustrated in a b equen examp has been found ,that, the effect, of secondary butyl alcohol in lowering the vapor pressure of a gasoline-isopropyl alcohol blend to which it is added is not merely one of counteracting the correpen n i QI VQPQE-P QSP ffe t o op opy o Data in the subse'quent exampleswill illustrate that, a marked synergistic flifict takes place, resulting in much s in r ase: inh he v por pressure of a I gasoline, than isopropyl alcohol but containing some secondary ,butyl alcohol are employed, L
EXAMPLE I in f h sbza ii ff lii c ba Si having The lowing inspections was mixed with various percentages of 99% i wmnrlalwhql swa -5 1W S nd b t alcohol respectively, but not mixtures of the two.
.Ellfl" eit qt qit'peic' t distilld j. .Various of alcohols were added to the base stock and thefiaptarprssure measured in p. s. iflg. The values. given..as AP ..represent the change in vapor employed.
.'1AB LE.I...1. APatyolume'percentageadditive 1 ...indicated (p..s.,i.g.) Composition 7 he .f s.
'oa'sounewmrbprd ilaiiofioijln 0175 piss lolsi 1'0. Gasoline-[secondary butyl alcohol 0.06 '0.12 0.25 O.31
. the above itmight beexpe ctednthat the addition to a base gasoline; stgckcf 8% totaLalcohol comprising a mixture of 6% isopropyl alcohol and 2% secondary Thus, the amount of isopropyl alco here'the addi n of only a small amount butyl alcohol based on the gasoline would result in a net vapor pressure increase of 0.75 p. s. i. (the sum of a +0.81 p. s. i. due to the isopropyl alcohol and 0.06 p. s. i. due to the secondary butyl alcohol). This is not the case, however, as is illustrated by Table II below. In obtaining the data for this latter table the same gasoline base stock Was mixed with blends of isopropyl and secondary butyl alcohols in various volume percentages and using various ratios of isopropyl alcohol to'secondary butyl alcohol. These results, in terms of changes in vapor pressure (AP), are given below.
TABLE II Volume Change in Ratio of isopropyl alcohol to secondary butyl percent of vapor alcohol additive pressure used (AP) in p. s. i.
1/l0 ll 0. 50 1/5" 12 -0.44 l/4 5 0. 12 1/4 l0 0. 19 1/3 4 0. 18 1/3 8 O. 12 1/2 3 0. 25 1/2 6 0. 13 1 2 0. 32 1.. 4 0.38 1 6 0.25 1 8 0. 19 2 2 0. 50 2 4 0. 50 2 6 0. 44 2 8 0. 37 3 2 0. 50 3 4 0. 50 3. 6 0.50 3.-. 8 0.19
Thus, instead of an overall vapor pressure increase of 0.75 p. s. i., as would have been expected to have resulted from the addition of 8% of a 3:1 mixture of isopropyl and secondary butyl alcohols in the absence of a synergistic effect, a vapor pressure increase of only 0.19 p. s. i. resulted. It will be noted by making other comparisons that in all cases the increase in vapor pressure obtained by using the mixture of isopropyl and secondary butyl alcohols was less than would be expected on the basis of the individual alcohols themselves. This difierential of 0.56 p. s. i. is equivalent to 1.1 volume percent of butanes. Therefore, instead of backing out 1.43% butanes, which would be necessary to maintain vapor pressure of the original base gasoline on the basis of the expected 0.75 p. s. i. increase due to the additive mixture, it is necessary to back out only 0.33 volume percent butanes to cancel the 0.19 p. s. i. actual increase. Thus, the advantages of the additives are obtained without the sacrifice of the expected amount of butanes.
1n the most preferred embodiments of the invention, the alcohols are added in such quantities as to produce an actual overall decrease in the vapor pressure. This means that additional butanes can be added to the gasoline and the desired volatility still maintained. To obtain this result the mixture of alcohols added must contain more secondary butyl alcohol than isopropyl alcohol and a substantial amount of the mixture must be employed. This does not adversely affect the fuel value of the gasoline, since as much as about 12% by volume of the alcohol mixture may be employed without appreciably lowering the calorific content of the resulting blend. Secondary butyl alcohol also contributes to the elimination of carburetor icing, especially when used in conjunction with isopropyl alcohol. Mixtures of equal volumes of isopropyl and secondary butyl alcohols are as effective in preventing carburetor icing as is isopropyl alcohol alone. For this reason, it is not always necessary to include as much as l2.5% of isopropyl alcohol in the gasoline to prevent carburetor icing. It may also be desirable in some cases to employ blends containing less secondary butyl alcohol than isopropyl alcohol, even though a net vapor pressure increase results, since this increase is less than the predictable value. In most instances 28% by volume of a blend of the alcohols will be incorporated into the gasoline. However, to obtain a vapor pressure decrease the use of blends containing at least about three times as much secondary butyl as isopropyl alcohol by volume'is preferred.
EXAMPLE II Although secondary butyl alcohol is the preferred additive for gasoline-isopropyl alcohol blends, it has also been found that mixtures of secondary and tertiary butyl alcohols also may be employed advantageously in some cases. The useof such mixtures is of great economic advantage, since in commercial operations mixtures of the secondary and tertiary butyl alcohols are commonly produced as such. The fact that mixtures of secondary and tertiary butyl alcohols may produce a net lowering of vapor pressure is an especially unexpected result, since the tertiary alcohol alone has a pronounced tendency to increase the vapor pressure of a gasoline to which it is added. In Table III below, a gasoline base stock was mixed with various percentages of isopropyl alcohol and various percentages of mixtures of isopropyl alcohol with mixed tertiary and secondary butyl alcohols. The Reid vapor pressures of these mixtures were determined and it was found that blends of isopropyl alcohol with the mixture of tertiary and secondary butyl alcohols often resulted in a net vapor pressure decrease.
TABLE III Modified 1 Composition Reid vapor pressure in p. s. i. g.
Base stock 14. 2 Base stock plus 2% isopropyl alcohol. 14. 6 Base stock plus 4% isopropyl alcohol. 14, 3 Base stock plus 8% isopropyl alcohol 14. 2 Base stock plus 4% of a 50/50 mixture of tertiary and secondary butyl alcohols... 13. 6 Base stock plus 2%iso1 hol and 2% of a 50/50 mix- 40 ture of tertiary and secondary butyl alcohols. 13.7
Base stock plus 4% isopropyl alcohol and 4% of a ture of tertiary and secondary butyl alcohols 13, 2
1 No Water present.
The addition of the mixed butyl alcohols effects a not decrease in vapor pressure of 0.5 p. s. i. in one case and 1.0 p. s. i. in the other. Thus, 0.95% by volume and 1.90% by volume respectively of butane could be added to these blends While maintaining the volatility of the fuel at a constant value.
EXAMPLE ill In addition to providing a beneficial effect in regard to vapor pressure or volatility characteristics of gasoline, secondary butyl or tertiary butyl alcohols provide an improvement in performance characteristics, especially with respect to octane number. In Table IV given below, a base gasoline stock containing 2.2 cc. per gallon of tetra ethyl lead was mixed with various percentages of secondary butyl alcohol and tertiary butyl alcohol, giving The research blending octane number is defined as the research octane number of the blend minus the value obtained when the research octane number of the base stock is multiplied by t1 1e fraction of base stock in the blend and Elie blliiggrence divided by the fraction of blending agent in It will be und rstood, lot c ur tha :th s con a y butyl akoholmaybesrippliejd either pure or'in ad with" other butyhalcohols suchias is'obutyl or butyl alcohols, as ,well as =With+tertiarybutyl alcohol. Thebasic-gasoline stockrnay also contain inaddi tion :to certain conventional materials such as t etraethyl;-lead or other alkyl lead anti-knock gents and conventional scavenging agents of the type conventionally employed Whenftetraethyl lead is used, such other additives as solvent oils, gum inhibitors; oxidationfinhibitor s, and thelike. l: v v i i' N While the invention has been described with respect to 'variou s specific' compositions, it will be, of course, understood thatit' is not to be so lirnited'but isto include such reasonable equivalents as may be included within the scope of the appended claims.
Whatis clair'ned'i's: i
l. A gasoline'con position consisting essentially of a hydrocarbon base stock boiling in thegasoline range,
hydrocarbons, about 1% to about 3%by volume of isopropyl alcohol and about 1% to about 9% by volume of'secondary'butyl alcohol.
'2. gasoline composition consisting essentially of hydrocarbons boiling in the gasoline range,'about 4% to about 20% by volume of C aliphatic hydrocarbons, and about 1% to 12% by volume ofisopropyl' alcohol and secondary butyl alcohol in th'e ratio of about lzl to 1:3.
about' -4% to about 20% "by volurne of C aliphatic 3. A ga o ine is qfi.ascllg ae iaz 2 ii; is
. about 1:3. U a I 5- A asol n hav n R vis van r ressu e mo e fl a bou 5 Pmmds Pe s uar n l 9 28 essenti ly f; a hyd o ar w as tq kwa gasoline ra nge, --abqut 4% to. 20% by volume I ,s. 29 aliphatic y bons. nd ab u 1% t .2 y 3 0 of a mixture of isopropyl alcohol and secondary butyl h l, sa m xture i n f h ee imes a mu s t ondary butyl alcohol as isopropyl alcohol.
References Cited in the file of this'patent V UNITED STATES PATENTS Alcohol, A Fuel-for Internal GOmbuStiQn Engines,
by s. 1; W. Pleeth, Chapman .and HallL td, 1949; page 83.
o P19131 11; iQahiPhltb. rt s 1 f s nm y a q l 9. se a ar h t l 7 9 45