Motor Fuel

This invention relates to liquid hydrocarbon fuel compositions having improved antiknock properties. In one of its aspects, this invention relates more particularly to liquid hydrocarbon fuel compositions intended for use in internal combustion engines containing novel and effective ashless antiknock agents. In accordance with a further aspect, this invention relates to liquid hydrocarbon compositions containing antiknock quantities of ashless antiknock agents selected from bicyclic diolefins.

Various antiknock agents have, heretofore, been suggested and employed for use in liquid hydrocarbon fuels, particularly in fuels employed in internal combustion engines. In such engines, it is highly desirable, from a stand point of economics that combustion of the fuel occurs at relatively high compression ratios. Such high compression ratios concomitantly necessitate the use of fuels having relatively high octane numbers to insure knock-free operation. Many antiknock agents have been proposed and/or used to improve the antiknock properties of hydrocarbon fuels used for internal combustion engines. In general, however, none of these antiknock additives have proved to be satisfactory in effectively raising the octane number of the fuel without also exhibiting other undesirable properties of varying importance. The phase-down of lead in gasoline as required by federal law and the banning of certain additives from use in unleaded gasoline has given impetus to continuation of a systematic study of the antiknock activity of ashless (non-metallic) compounds. The present invention is directed to the use of ashless (non-metallic) additives as antiknock agents for internal combustion fuels.

Accordingly, an object of this invention is to provide ashless hydrocarbon fuel compositions.

Another object of this invention is to provide ashless (non-metallic) antiknock additives for internal combustion engine fuels.

Another object of this invention is to provide hydrocarbon fuel compositions exhibiting improved antiknock properties.

Other objects, aspects, as well as the several advantages of the invention will be apparent to those skilled in the art upon reading the specification and the appended claims.

In accordance with the present invention, new and improved liquid hydrocarbon fuel compositions are provided containing an antiknock quantity of ashless (non-metallic) antiknock additives selected from bicyclic diolefins represented by norbornadiene (NBD) and alkyl and aryl derivatives thereof.

The antiknock additives of the invention are known and can be prepared by processes known in the art.

Specific examples of bicyclic diolefin ashless antiknock agents of the invention that can be used in internal combustion engine fuels include norbornadiene and structurally closely related compounds having alkyl and aryl substituents. Compounds that can be used include those having lower alkyl groups or aryl groups substituted on the bicyclic diolefin rings. These compounds have suitable solubility and volatility characteristics to permit their application as additives for hydrocarbon fuels.

Specific representative examples of bicyclic diolefin compounds that can be used include norbornadiene (also known as becyclo (2.2.1) hepta-2,5-diene), 1-methylnorbornadiene, 2-methylnorbornadiene, 7-methylnorbornadiene and mixtures thereof; 1,5-dimethylnorbornadiene, 1,2-dimethylnorbornadiene, 1,4-dimethylnorbornadiene, 1,7-dimethylnorbornadiene, 2,5-dimethylnorbornadiene and mixtures thereof; 1, 2, 3, 4, 7 pentamethylnorbornadiene, 2-methyl-5-phenyl norbornadiene, 2-ethylnorbornadiene, 2-isopropylnorbornadiene, 2-t-butylnorbornadiene, 7-isopropylnorbornadiene, and the like, and mixtures thereof.

The specific antiknock additives of the invention are highly suited for use in fuels in view of their ashless characteristics. Naturally, the various compounds of the herein disclosed group do not possess exactly identical effectiveness, and the most advantageous concentration for each such compound will depend to some extent upon the particular compound used. Also, the minimum effective inhibitor concentration can vary somewhat according to the specific nature of the hydrocarbon composition to which it is added.

The amounts of the antiknock agents of the invention added to the hydrocarbon fuels will be sufficient to improve the antiknock properties of the fuel. In general, these novel antiknock additives are employed in amounts from about 0.5 to about 10 percent (5000 to 100,000 parts per million), preferably from about 1 to about 5 percent (10,000 to 50,000 parts per million), by weight of the total weight of the fuel composition.

The motor fuels or gasolines into which the invention additives are incorporated are conventional motor fuel distillates boiling in the range of about 70.degree.-420.degree. F. (21.1.degree.-216.degree. C.). Gasolines or automotive fuels to which the described additives perform the functions described herein include substantially all grades of gasoline presently being employed in automotive and internal combustion aircraft engines. Generally automotive and aircraft gasolines contain both straight run and cracked stock with or without alkylated hydrocarbons, reformed hydrocarbons, and the like. Such gasolines can be prepared from saturated hydrocarbons, e.g., straight run stocks, alkylation products, and the like, with or without gum inhibitors, detergents, corrosion inhibitors, solvents, emulsifiers, and the like. The motor fuels are unleaded and can contain other conventional fuel additives such as antioxidants and the like.

A 0.1 molar solution (1.1 vol. %) of norbornadiene (NBD) in clear (unleaded) FT-175 gasoline was prepared. The following table presents the characteristics of FT-175 gasoline.

The gasoline was engine tested to determine its Research Octane Number (RON) according to ASTM D 2599-47.

Additional runs were carried out using varying amounts of norbornadiene (NBD) in clear (unleaded) FT-266 gasoline. The following table presents the characteristics of FT-266 gasoline.

The gasoline was engine tested to determine its Research Octane Number (RON) according to ASTM D 2599-47.

The increase in RON over the untreated fuel by the addition of norbornadiene is shown in the following table.

The efficacy of the novel ashless antiknock compounds of the present invention for improving the antiknock properties of liquid hydrocarbon fuels will be apparent from the foregoing example and comparative data. It will be understood that the novel ashless antiknock compounds of the present invention can be advantageously employed in any liquid hydrocarbon fuel composition which is suitable for use in a combustion engine regardless of the purpose for which the engine is designated.