US2408999A - Motor fuels - Google Patents

Description

Patented Oct. 8 1946 MOTOR FUELS Anthony E. Robertson, Roselle, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application January 1, 1944, Serial No. 516,711

9 Claims. (01314-53) In this invention selected alcohols properly blended with certain low molecular weight hydrocarbons provide valuable quick-starting fuels for high-compression spark-ignition engines. These fuels are of special value for developing maximum power and thermal efiioiency in high output engines with freedom from vapor locking difiiculties.

Although it has been known that alcohols, such as methyl or ethyl alcohol, either pure or blended with gasoline have some advantages as motor fuels, mainly that of high octane rating, they have only limited use in countries where adequate petroleum supplies are readily available. The alcohol-gasoline blends introduce certain operating diliiculties; for example, a small amount of water causes separation of the alcohols from the gasoline, meaning that these blends have low water tolerance. These blends, moreover, are subject to vapor locking difficulties, which are more serious than such difliculties incident to the use of the gasoline without the addition of alcohol. The use of the pure alcohols would be advantageous for power, anti-detonating quality, and water tolerance, but the pure alcohols have poor starting characteristics.

In accordance with the present invention, disadvantages of alcohol-gasoline blends and pure alcohols as motor fuels are overcome by blending from to by volume of a selected low molecular weight hydrocarbon component having from 3 to 5 carbon atoms per molecule, with a major proportion of an alcohol having from 1 to 5 carbon atoms per molecule.

I have found that blends of these selected compounds in the proper proportions are not subject to phase separation, even if a considerable amount of water is added. Ihave also found that these blends satisfactorily keep in storage without excessive vapor loss and satisfactorily mix with intake air on being carbureted for obtaining quick starting of a cold motor. These blends exhibit extraordinary freedom from vapor lock in carbureting systems designed and set for use with ordinary hydrocarbon fuels. In comparison to all alcohol containing fuels hitherto proposed, the exceptional properties of the blends herein provided are of tremendous advantage,

In order to obtain a desired efficiency with these fuel blends, it is important that the volatile hydrocarbon component be blended in a proportion of at least 5% of the blended components and should be lower boiling, or of greater volatility, than hexanes or hexenes. Methane, ethane, and ethylene are at the other extreme, in being too low boiling. Limitations on selection 2 and proportioning of the hydrocarbon component are dependent on proper air to fuel ratios in average fuel induction systems.

Fuel blends of the present invention have certain peculiar characteristics in that the low boiling hydrocarbon and the alcohol blended in ascertained proportions do not form ideal solutions but exhibit abnormally large deviations from Raoults law governing ideal solutions. These deviations appear significant for satisfactory airfuel ratios with blends herein described. Small amounts of lower and higher boiling hydrocarbons, such as, ethane or hexane, incidentally present in the composition do not destroy the value of the fuel for the intended purpose,

The upper limit of the hydrocarbon component proportion restricted in accordance with empirical determinations on Vapor lock tendencies of the blends; for example, a blend of more than 10% of isopentane in ethanol, or more than 10% butane in isopropanol or butanol, at ordinary atmospheric temperatures causes vapor lock in the average fuel system. Thus, about 10% by volume of the hydrocarbon component is the upper practical limit.

Blends of between 5% and 10% by volume of the volatile hydrocarbon component with to 90% by volume of the alcohol component exhibit desirable properties of quick-starting, high antiknock quality, low vapor-locking tendency and high-power output.

Alcohols used as a major ingredient of the blends are preferably monohydric aliphatic alcohols (alkanols) of 1 to 5 carbon atoms per molecule, Ethyl and methyl alcohols, on account of their availability and large deviations from ideal solutions in the desired blends are useful.

Of alcohols higher boiling than ethyl alcohol, isopropyl and secondary butyl alcohols are outstanding for present purposes. Other alcohols higher boiling than ethyl, but with less preference, are n-propyl, n-butyl, tertiary-butyl, isobutyl, ter-amyl, n-amyl, and sec-amyl alcohols. The preferred alcohols have normal boiling points below C. It is desirable to omit alcohols boiling above C.

Blends formulated for the practice of this invention have unusual distillation and vapor pressure characteristics, which enable them to form a vapor charge which undergoes quick ignition in cold motors at sub-zero temperatures. These blends remain homogeneous even with 10 or more volumes of water added per 100 volumes of the blend. They remain satisfactorily constant in composition and purity for suitable periods of.

3 time for use under various operating conditions.

For illustration, characteristics of blends forming specific embodiments of this invention are presented in the following table:

4 throughout the boiling range of the fuel being increased. This balancing of the volatility is desirable for more uniform distribution of the combustible mixture. Thus, in characteristics Table I Initial Water toler- 907 d1s- Dist. Reid vapor boiling ance vols. of Blend Composition tilled ofl loss pressure point water/100 F. at a percent vols. oi blend 5% n-pentane in methanol 7.9 122 149 1. 22. 4 10% n-pentane in methanol 11. 4' 88 149 0.8 11.9 isopentane in ethanol 5.7 .185 .178 l. 7 38. 5 10% isopentane in ethanol... 9. 4 97 178 1. 5 29. 5 5% butane cut in isopropanol 8.3 131 179 1.9 111. 0 5% butane cut in butanol 7. 6 185 241 5.0 16. 7

The butane cut used in blends 5 and 6 is otherwise known as plant butane, which contains approximately 60 to 70% n-butane, to lsobutane, and 10 to 20% butenes:

Another remarkable characteristic of the new 20 of prime importance for engine performance, the

and volatility distribution of the blends. To illustrate this phase of the invention, the following examples are given:

EXAMPLES Blends of n-pentane and isopropyl alcohol were made up with varying amounts of water then subjected to tests for determination of their volatility and vapor pressure characteristics. The compositions of the blends and the inspections obtained on them are summarized below:

Table II Blend No.

Vol. per cent n-pentane 10 10 10 10 Vol. per cent isopropanoL 90 80 70 00 Vol. per cent of water 0 10 20 Inspections:

Gravity, A. P. I 50. 5 43.6 38.2 33.0 Reid V. P., #/sq. in 5. 0 6. 7 11. l 13. 5 A. S. T. M. dist.-

I. B. P., F 122 97 95 91 Per cent at 158 11. 8.0 9. 5 11.0 12. 5- Per cent at 212 F 94.0 84 90% at 180 176 100 212 Dist loss, per cen 2.0 1.0 1.0 1.0

By investigation of engine performance with ited amounts of about 10, 20, and 30%, the Reid vapor pressure is increased, while at the same time, the blend is given substantial improvement in volatility balance, the amounts of the fuel vaporized at different intermediate temperatures places minor proportions of alcohol, in the lim-',

aqueous alcoholic solutions containing correct amounts of the highly volatile hydrocarbons are fully satisfactory.

As previously set forth, regardless of whether the fuel blend contains water or is substantially free from water, it should preferably contain a hydrocarbon component blended in a proportion of about 5 to about 10% by volume in order to give the blend the desired advantageous characteristics noted. The alcohol component constituted of one or more alkanols having 1 to 5 carbon atoms per molecule is the major ingredient of the fuel blend, 1. e., the alcohol, whether anhydrous or aqueous i blended in an amount oi at least 60%.

When water is present in the fuel blend to form what is termed an aqueous alcohol component, the proportion of water added should not exceed that amount which is above the water tolerance of the blend, moreover, preferably it should not exceed about 30% by volume.

The ordinarily most useful fuel blends of the present invention are formulated from to 1 part by volume of the 3 to 5 carbon atom hydrocarbon component blended with 6 to 9 parts by volume of the 1 to 5 carbon atom alcohol component and with from 0 to 3 parts by volume of water, the combined parts by volume of the alcohol component and of the water being blended with; the hydrocarbon component in a volume ratio of at least about 9 to 1, so that the aqueous alcohol forms at least about by volume of the fuel.

It is not intended to limit the invention to the specific blends shown in th foregoing tables. It will be observed that these tables illustrate how the blends are obtained with varying characteristicsjso that for a specific purpose, the most efiicient blend is provided.

If requirements of a carbureted engine are such that the Reid vapor pressure must come within the range of'l to 7.5 or 8 pounds per square inch, as in the case of aviation motors, blends meeting this requirement are available among th foregoing types of blends. For example, a blend between 5% and 10% of isopentane in ethanol will clearly have a Reid vapor pressure meeting these requirements. Other properly chosen combinations of the hydrocarbons and alcohols also meet this requirement.

It is to be noted that the preferred blends are obtained by selecting a relatively higher molecular weight hydrocarbon for blending with a lower molecular weight alcohol, e. g., a C4 to C5 hydrocarbon with a C1 to C2 alcohol, vice versa, a lower hydrocarbon blended with a higher alcohol, e. 3.,

5. a C3 or C4 hydrocarbon with a C3 to C5 alcohol, or with modification by added water. However, for an average automotive engine, blends satisfactorily used have Reid vapor pressures ranging from 5 to as high as about 13 pounds per square inch at 100 F., or even slightly higher in cold climates.

One way of eficiently and economically using the disclosed blends is to supply the carburetor of the engine from an individual tank separate from the main supply tank, so that the alcohol blend can be fed to the engine for starting at low temperatures or acceleration at high power.

The advantageous blends described may also contain small amounts of other ingredients ordinarily useful in motor fuels, e. g., a fraction of 1%of an anti-knock agent, such as tetraethyl or tetramethyl lead. They may also contain a small amount of a dye, thickening agent, or lubricant. By a small amount is meant generally less than about 1%.

The volatile hydrocarbon component, as indicated, is preferably a 3 to 5 carbon atom paraffinic hydrocarbon which is resistant to oxidation and readily available in highly purified form; hence, in general, the disclosed blends are easily obtained in a chemically stable form.

The hydrocarbon component may also contain or be composed of unsaturated hydrocarbons having 3 to 5 carbon atoms per molecule. Such unsaturated hydrocarbons may be mono-olefins or diolefins, but preferably the unsaturated hydrocarbons should not contain more than one double bond, i. e., should not be more unsaturated than a mono-olefin. Also, the 3 to 5 carbon atom cycloalkanes or cycloalkenes may be used. Thus, in general, suitable hydrocarbons for the hydrocarbon component may be characterized as 3 to 5 carbon atom molecules containing no more than two double bonds and preferably no more than one double bond.

The alcohol component may contain small amounts of other low boiling oxygen-containing compounds, such as ethers, ketones, aldehydes, and esters, but ordinarily these should not be present in any substantial amounts to avoid upsetting the effective balance between the preferred components in the blend.

The present application is a continuation-inpart of application Serial No. 370,787 filed-December 19, 1940, now Patent No. 2,365,009, dated December 11, 1944, the claims of which read on a motor fuel containing a substantial amount of water as an essential constituent. The purpose of the present application is to claim motor fuels not containing water but which do contain a major proportion of a branched alcohol and a minor amount of a light hydrocarbon of about 3 to 5 carbon atoms.

Some experimental data have already been given above as to blend of isopropyl alcohol containing in one case 5% of butane and in another case of normal pentane. Other satisfactory blends which are preferred even over the above two examples, are blends of isopropyl a1- cohol with either isobutane or isopentane or a light cycloalkane such as cyclopentane, because these blends exhibit superior performance when lead tetraethyl is added to them for use in especially high octane number aviation engines.

The term branched alcohol of 3 to 5 carbon atoms is intended to include isopropyl alcohol which is branched in View of the linkage of the hydroxyl group to the middle of the 3 carbon atoms, as well as secondary or tertiary butyl and amyl alcohol, and even the primary amyl alcohols which contain a branched hydrocarbon structure, such as tertiary butyl carbanol and 2- methyl or 3-methyl'butano1.

When such fuels are prepared without the addition of any water, the branched alcohol should constitute about 80-95% by volume of the fuel ing 80-95% of isopropyl alcohol and 20-5% of a branched paraflinic hydrocarbon of 4-5 carbon atoms, such as isopentane, or a cyclo paraffln such as cyclopentane.

There are obviously a number of modifications which come within the spirit of this invention and it is not intended that the invention as defined in the appended claims be limited to the specific examples that have been given for the purpose of illustration.

I claim:

1. A motor fuel comprising about 80 to 95% of a branched alkanol of 3 to 5 carbon atoms and a minor proportion suificient to raise the Reid vapor pressure of the blend to at least 5 lbs. per square inch at 100 F. but not more than about 1 3 lbs. per square inch at 100 F. of a normally gaseous hydrocarbon of 3 to 5 carbon atoms selected from the group consisting of aliphatic and cyclo-aliphatic hydrocarbons.

2. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. per square inch at 100 F. containing about 5% to 10% of 3 to 5 carbon atoms hydrocarbons containing no more than 2 double bonds per molecule selected from the group consisting of aliphatic and cyclo-aliphatic hydrocarbons, and a major proportion of a 3 to 5 carbon atoms branched alkanol.

3. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. per square inch at 100 F.

I comprising about 80 to 95% by volume of'isoproyl alcohol and about 20-5% of a hydrocarbon of 4 to 5 carbon atoms selected from the group consisting of aliphatic and cyclo-aliphatic hydrocarbons.

4. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. per square inch at 100 F. particularly adapted for quick cold starting and high power output, comprising about to 95% of isopropyl alcohol and about 20-5% of a branched 4 to 5 carbon atoms parafiinic hydrocarbon.

5. A motor fuel according to claim 4 in which the light hydrocarbon is a pentane. I

6. A motor fuel according to claim 4 comprising about of isopropyl alcohol and about 10% of isopentane.

7. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. per square inch at 100 F. comprising about 80 to by volume of a branched alkanol of 3 to 5 carbon atoms, and about 20-5% of a mixed C4 aliphatic hydrocarbon fraction.

8. Motor fuel according to claim 1 containing a small amount of a lead alkyl anti-knock agent.

9. Motor fuel according to claim 3 containing small amounts of tetraethyl lead.

ANTHONY E. ROBERTSON.