GASOLINE COMPOSITION

Abstract: A gasoline composition contains a minor amount of at least one of a specified group of quaternary ammonium hydroxides for decreasing or reversing the octane requirement increase (ORI) for a fuel-fired spark ignition internal combustion engine. Tetrabutylammonium hydroxide and tricaprylicmethylammonium hydroxide are two preferred compounds for use.

Description: FIELD OF THE INVENTION The present invention relates to a method for improving the operation of a gasoline fueled spark ignition internal combustion engine. More specifically, the present invention relates to a method for controlling or decreasing the octane requirement increase typically encountered during the first several thousand kilometres of operation of gasoline fueled spark ignition internal combustion engines. BACKGROUND OF THE INVENTION As is known in the art, the octane requirement is lower for a new or cleaned spark fired internal combustion engine than for one that has been subjected to operation over a period of time equivalent to several thousand kilometres. In other words, as a new or clean engine is used or operated an octane requirement increase (ORI) is observed, i.e., the octane number of the fuel required for knock-free operation of the engine increases over time until a stable level is reached. Also known is the fact that the observed octane requirement increase is associated with build-up of deposits in the combustion chamber of the engine. Consequently, additives have been employed for preventing or reducing deposit formation in or for removing the deposits from the combustion chamber once they have been formed. In this regard, see, for example, US-A-4,357,148 and the patents cited therein. Obviously, there is always a need for new, better and more economical additives which will function so as to reduce the octane requirement increase of spark ignition internal combustion engines. SUMMARY OF THE INVENTION Surprisingly it has been found that when minor amounts of certain quarternary ammonium hydroxides are added to gasolines, the octane requirement increase for fuel fired spark ignition internal combustion engines is decreased or reversed. The quarternary ammonium hydroxides useful according to the present invention are selected from tetrabutyl ammonium hydroxide, tricaprylicmethyl ammonium hydroxide, and mixtures thereof. Thus, in one aspect, the present invention comprises a method for controlling the ORI of spark ignition internal combustion engines by operating such engines on a fuel containing a quaternary ammonium hydroxide of the aforementioned type in amounts sufficient to control the ORI. In view of the foregoing, it should be appreciated that the additives of the present invention may be introduced directly into gasoline, i.e., a liquid hydrocarbon fuel in the gasoline boiling range in amounts sufficient to decrease the ORI thereby providing a composition comprising a major portion of a hydrocarbon base fuel boiling in the range of gasoline and including from 0.001 to 0.075 wt.% of a quaternary ammonium hydroxide of the above-mentioned formula. Indeed, it is particularly preferred to incorporate 0.003 to 0.030 wt.% quaternary ammonium hydroxide. Especially preferred is a gasoline composition comprising a major portion of a hydrocarbon based fuel boiling in the boiling range of gasoline and including from 0.005 to 0.015 wt.% of quaternary ammonium hydroxide selected from tetrabutylammonium hydroxide and tricaprylicmethyl ammonium hydroxide and mixtures thereof. In another embodiment of the present invention a concentrate for use in a base fuel boiling in the range of gasoline is provided comprising 20 to 80 wt.% of the hereinabove described quaternary ammonium hydroxides in an appropriate organic solvent compatible with and boiling in the gasoline range. Suitable organic solvents include aromatic hydrocarbons such as benzene, toluene, xylene, alcohols such as ethanol, ethylisobutylcarbonyl and the like. Mixtures of hydrocarbons and alcohols may also be used in preparing the concentrate. In general the quantity of solvent in such concentrates will range from 20 to 80 wt.%. of the concentrate. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph illustrating the decrease in ORI over that of a base fuel achieved by practice of the present invention. Figure 2 is a graph showing the reversal of ORI that is achieved in accordance with the practice of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The following series of tests are presented to illustrate the invention. EXAMPLE 1 In this example, a 250 CID engine was employed which for each of the three tests conducted had first been cleaned by removing deposits from the intake manifolds, intake ports and combustion chamber area of the engine. As illustrated in Table I below, one of the test was conducted with a base fuel while the remaining two tests were conducted with the same fuel but containing an additive of the present invention. The octane requirement of the engine was determined while increasing engine speed from 1500 to 3000 rpm in a 15 sec. period. The results are set forth in Table I below and shown graphically in Figure 1. Test Fuel Run 1 Run 2 Run 3 Base fuel Base fuel +additive Base fuel +additive RON 0 hrs. 84.9 85.5 85.9 RON 180 hrs. 95.2 88.3 91.3 ORI 10.3 2.8 5.4 ORI Reduction 7.5 4.9 EXAMPLE 2 The procedure of Example 1 was repeated with another 250 CID engine with the results shown in Table II below. Test Fuel Run 1 Run 2 Run 3 Base fuel Base fuel +additive Base fuel +additive RON at 0 hrs. 84.7 83.9 83.7 RON at 180 hrs. 95.7 91.6 87.0 ORI 11.0 7.7 3.3 ORI Reduction 3.3 7.7 As can be seen from Examples 1 and 2, ORI reductions in the range of 3.3 to 7.7 octane numbers were obtained. EXAMPLE 3 In this example, the general procedure of Example 1 was followed. However, after running the engine for 180 hours on the base fuel, the engine was then operated without cleaning on a fuel containing an additive in accordance with this invention. Results are set forth in Table III below and depicted graphically in Figure 2. Fuel Base Fuel Base Fuel + Additive Test Hrs. 0 90 180 210 276 RON 82.6 92.3 94.6 92.8 91.1 As can be seen from the foregoing, the octane requirement of the engine, after having gone from 82.6 to 94.6 in 180 hours with the base fuel was reversed by use of an additive of this invention declining to 91.1 in 96 hours. In the foregoing example, 250 CID engines were employed. By this term is meant straight six cylinder engines of 250 cubic inches (4.097 litres) displacement.

Claims: A method of controlling the octane requirement increase of a spark ignition internal combustion engine, comprising operating said engine on a fuel containing (i) a major proportion of a liquid hydrocarbon base fuel boiling in the boiling range of gasoline and (ii) a minor proportion of at least one quarternary ammonium hydroxide characterised in that the quarternary ammonium hydroxide is selected from tetrabutylammonium hydroxide, tricaprylicmethyl ammonium hydroxide, and mixtures thereof. A method as claimed in claim 1, wherein the quarternary ammonium hydroxide is present in the fuel in a total amount of from 0.001 to 0.075 weight percent. A gasoline composition comprising a major proportion of a hydrocarbon base fuel boiling in the boiling range of gasoline and a minor proportion of at least one quarternary ammonium hydroxide characterised in that the quarternary ammonium hydroxide is selected from tetrabutylammonium hydroxide, tricaprylicmethyl ammonium hydroxide, and mixtures thereof. A composition as claimed in claim 3, wherein said quarternary ammonium hydroxide is present in a total amount of from 0.001 to 0.075 weight percent of the composition. A gasoline additive concentrate suitable for use in a hydrocarbon base fuel boiling in the boiling range of gasoline, comprising (i) an organic solvent, boiling in the range of gasoline, selected from hydrocarbon solvents, aliphatic alcohols and mixtures thereof and (ii) at least one quarternary ammonium hydroxide having characterised in that the quarternary ammonium hydroxide is selected from tetrabutylammonium hydroxide, tricaprylicmethyl ammonium hydroxide, and mixtures thereof, the solvent being present in amounts ranging from 20 to 80 percent by weight of the concentrate.

Inventors: FELDMAN, NICHOLAS
Applicants: EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1987
Main classification: C10L1
IPC codes: C10L1