Motor Fuel Composition

This invention relates to fuels for internal combustion engines and more particularly to a novel clear stable gasoline-alcohol-water motor fuel composition.

The use of aliphatic alcohols such as methanol and ethanol to extend gasoline fuels while imparting a higher octane rating to the gasoline has been long attempted. Alcohol-gasoline blends have a low tolerance for water that is encountered in the blending and distribution systems. Methanol-gasoline blends are much less water tolerant than ethanol-gasoline blends. Unstable hazy blends may result when water is present in such systems. Hazy gasolines are unacceptable by the public since they may indicate that something is wrong with the product. For example, the fuel may be contaminated. Further, phase separation may occur with water separating out and contributing to corrosion problems and motor starting difficulties.

On the other hand, it has been recognized that some water in the gasoline is desirable since the presence of water will reduce the Octane Requirement Increase (ORI), and will increase the Octane Rating (OR). Advantageously, by the subject invention gasoline may be extended and its performance improved by the addition of the alcohols and water without producing haze and separation of the constituents.

U.S. Pat. No. 3,876,391 discloses clear motor fuel microemulsions comprising gasoline, water, two different surfactants and a water soluble and insufficiently gasoline soluble additive. No alcohol is present. U.S. Pat. No. 4,384,872 discloses a motor fuel composition comprising gasoline, alcohol and an interfacial modifying agent. No water is present.

In accordance with the invention there is provided a clear stable gasoline-alcohol-water motor fuel composition comprising a mixture of an alcohol selected from the group consisting of methanol in the amount of about 2.0 to 5.0 volume percent, ethanol in the amount of about 2.0 to 10.0 volume percent, and mixtures thereof in the amount of about 3.0 to 9.0 volume percent; about 2.0 to 10 volume percent of a cosolvent alcohol selected from the group consisting of tertiary butyl alcohol, isopropanol, and mixtures thereof; water to provide a total water concentration of about 0.1 to 0.5 weight percent; about 0.01 to 3.0 weight percent of surfactant which is represented by Formula I as follows: ##STR1## wherein: R.sup.1 and R.sup.2 may be the same or different and are selected from the group consisting of hydrogen and methyl; n is an integer from 1 to 3; and x is an integer from 8 to 10; and the balance of said motor fuel composition being gasoline. Preferably, the volumetric ratio of tertiary butyl alcohol and/or isopropanol to methanol and/or ethanol in the subject clear stable motor fuel composition is in the range of about 0.3 to 3.0, such as about 0.5 to 2.0.

This invention also provides a process for operating an internal combustion engine, supplying thereto, and combusting therein the above motor fuel composition.

The subject invention deals with clear stable motor fuel compositions comprising gasoline, at least two different alcohols, water and a surfactant. The surfactant more specifically comprises an ethoxylated bisphenol. A low dosage e.g. about two weight percent or less of the surfactant will solubilize the water and form a microemulsion. The microemulsion is of the "water-in-petroleum" type in which the average particle diameter of the dispersed phase is about 0.1 micron or smaller. Clear stable gasoline-alcohol-water motor fuel compositions having upgraded performance characteristics are thereby provided.

The stable gasoline-alcohol-water motor fuel composition comprises a mixture of an alcohol selected from the group consisting of methanol in the amount of about 2.0 to 5.0 volume percent, ethanol in the amount of about 2.0 to 10.0 volume percent, and mixtures thereof in the amount of about 3.0 to 9.0 volume percent, about 2.0 to 10 volume percent of a cosolvent alcohol selected from the group consisting of tertiary butyl alcohol, isopropanol, and mixtures thereof; water to provide a total water concentration of about 0.1 to 0.5 weight percent (basis weight of motor fuel composition), such as about 0.30 to 0.40 wt. %; about 0.01 to 3.0 weight percent such as about 0.02 to 0.50 wt. % (basis motor fuel composition) of a surfactant represented by Formula I to be further described; and the remainder is a gasoline base fuel. Preferably, the volumetric ratio of tertiary butyl alcohol and/or isopropanol to methanol and/or ethanol in the subject clear stable motor fuel composition is in the range of about 0.3 to 3.0, such as about 0.5 to 2.0.

In one embodiment, the subject clear stable motor fuel composition may be prepared as follows:

Mixture A is prepared by mixing together an alcohol selected from the group consisting of methanol in the amount of about 2.0 to 5.0 vol. %, such as about 2.70 to 4.75 vol. % (basis motor fuel composition), ethanol in the amount of about 2.0 to 10.0 vol. %, such as about 4.75 to 9.0 vol. % (basis motor fuel composition), and mixtures thereof in the amount of about 3.0 to 9.0 vol. % (basis motor fuel composition); about 2 to 10 vol %, such as about 4.75 to 6.3 vol. % (basis motor fuel composition) of a cosolvent alcohol selected from the group consisting of tertiary butyl alcohol, isopropanol, and mixtures thereof; and water to provide a total water concentration of about 0.1 to 0.5 weight percent, such as about 0.30 to 0.40 wt. % (basis weight of motor fuel composition). A hazy motor fuel composition is obtained when Mixture A and the base fuel gasoline, substantially comprising the remainder of the motor fuel composition, are mixed together. Further, about 0.01 to 3.0 weight percent (basis weight of motor fuel composition) of a surfactant to be more fully described is preferably added during the blending of Mixture A with the gasoline. Agitation is continued until the clear stable gasoline-alcohol-water motor fuel composition of this invention is made. The clear dispersion produced is a microemulsion.

The aforesaid improved ethoxylated bisphenol surfactant which is used in the subject clear stable motor fuel composition has the structural Formula I as follows: ##STR2## wherein: R.sup.1 and R.sup.2 may be the same or different and are selected from the group consisting of hydrogen and methyl; n is an integer from 1 to 3; and x is an integer from 8 to 10. Preferably, R.sup.1 and R.sup.2 are H, n is 1 and x is 10. The molecular weight of said surfactant is in the range of about 900 to 1110.

Any gasoline suitable for a spark-ignited internal combustion engine can be extended and its octane rating increased by being blended with water and the specified mixture of alcohols in accordance with the practice of this invention. Clear stable gasoline-alcohol-water motor fuel compositions are thereby produced. In general, the base fuel will consist of a mixture of hydrocarbons in the gasoline boiling range i.e., boiling from about 75.degree. to 450.degree. F. The hydrocarbon components may consist of paraffinic naphthenic, aromatic and olefinic hydrocarbons. This gasoline can be obtained naturally or it may be produced by thermal or catalytic cracking and/or reforming of petroleum hydrocarbons. The base fuel will generally have a Research Octane Number above 85 and up to about 102 with the preferred range being from about 88 to 95. The clear stable gasoline-alcohol-water motor fuel composition of this invention will generally have a Research Octane Number about 85 and up to about 102, such as about 90 to 100.

In most cases, water from an external source will be introduced into the motor fuel composition to supplement any water that may be dissolved in the alcohol and/or gasoline. Sources of water include purified deionized water, and bottom phase water e.g. process water that sinks to the bottom of a gravity separation tank containing gasoline.

In another embodiment, gasoline contaminated with water may be processed into an upgraded clear stable motor fuel. In such case, the gasoline-water mixture is mixed with a mixture of the aforesaid alcohols, any additional water, and a surfactant having the previously described Formula I. The amount of each constituent is the same as that previously described in the preferred embodiment. Agitation is continued until a clear dispersion is produced.

Advantages of the present invention are illustrated by the following specific examples. These example are set forth for purpose of illustration and should not be construed as limiting the invention.

A clear gasoline was mixed with 4000 parts per million of water (basis weight of clear gasoline), 2.7 volume % of methanol (basis clear stable fuel composition), and 6.3 volume % of tertiary butyl alcohol (basis clear stable fuel composition) to produce Mixture 1. Clear unleaded base fuel e.g. gasoline called Mixture 2 was mixed with Mixture 1 in the volumeric proportions shown in Table I e.g. 10-50% Mixture 1 and the remainder Mixture 2 to produce a hazy Fuel Composition. Formula I surfactant (as previously described) cut back 50% was added drop wise at a temperature of 64.degree. F. and 35.degree. F. until after the addition of the specified cubic centimeters of surfactant the hazy fuel composition became clear and the subject clear stable fuel composition was produced. The results are shown in Table I below:

Although this invention has been illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made which clearly fall within the scope of the invention.