Technical Field

The present invention concerns a fuel additive with for improving the octane quality of a fuel composition. It also concerns the fuel composition.

Background Art

Fuel additives, for fuel composition suitable for combustion in an (automotive) engine, are known. Fuels, particularly gasoline fuels have undergone many changes over the years in order to improve engine performance and reduce engine emissions. Many octane improving compounds used for improving engine performance and extending fuel supplies, such as tetraethyl lead, aromatic compounds, methycyclopentadienyl manganese tricarbonyl (“MMT”), methyl tertiary butyl ether ("MTBE") and other such additives, have shown excellent performance.

The octane requirement increase effect exhibited by internal combustion engines, e.g., spark ignition engines, is well known in the art. If the engine is operated with a gasoline fuel, which has a lower octane number than the minimum requirement for the engine, "knocking" can occur. Knocking occurs when a gasoline fuel spontaneously and prematurely ignites or detonates in the engine prior to spark plug initiated ignition. This effect is coincidental with the formation of deposits in the region of the combustion chamber of the engine.

Several additives when added to hydrocarbon fuels can prevent or reduce deposit formation, or remove or modify formed deposits, in the combustion chamber and on adjacent surfaces such as intake valves, ports, and spark plugs, which in turn causes a decrease in octane requirement. For example, MMT is known to be an effective antiknock additive (See U.S. Pat. Nos. 2,818,417; 2,839,552; and 3,127,351).

ASTM D2699 is the standard test method for Research Octane Number (“RON”) of sparkignition engine fuels. This laboratory test method covers the quantitative determination of the knock rating of liquid spark-ignition engine fuel in terms of RON., including fuels that contain up to 25 % v/v of ethanol. The sample fuel is tested using a standardized single cylinder, four- stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions. The O.N. scale is defined by the volumetric composition of PRF blends. The sample fuel knock intensity is compared to that of one or more PRF blends. The O.N. of the PRF blend that matches the K.l. of the sample fuel establishes the Research O.N.

Typical commercial fuels produced for spark-ignition engines rate in the 88 to 101 RON range.

WRT BV in The Netherlands has developed a range of additives that enhance fuels by improving their quality, performance, safety or handling. For instance, a gasoline with a RON of 89.6 may be improved to 91.6 with addition of 150 ppm of an additive composed of 50% by volume ferrocene and 50% by volume toluene. The same fuel maybe improved to 92.4 with 150 ppm of MMT.

The need remains, however, to provide additives that provide an improved Research O.N. and do so cost effectively.

Summary of the Invention

The present invention provides a fuel additive consisting essentially of a mixture of

(a) 37-38 % v/v methylcyclopentadienyl manganese tricarbonyl (MMT);

(b) 13-12 % v/v methyl tert-butyl ether (MTBE);

(c) 24-26 % v/v ferrocene, and

(d) 24-26 % v/v toluene, adding up to 100%.

Also provided is a fuel composition comprising the fuel additive.

Detailed description of the Invention

Fuel additive compositions and their uses are known. Methylcyclopentadienyl manganese tricarbonyl (MMT) and bis(r|5-cyclopentadienyl)iron (ferrocene) are known.

Surprisingly a synergistic blend has been found, using the 4 components that performs as good, and at a lower cost, then an additive based on ferrocene/toluene or an additive based on MMT. It even performs better than a blend of ferrocene/toluene and MMT.

The fuel additive of the present invention consists essentially of the 4 components (a)-(d), adding up to 100%. The range where the synergistic effect has been found is narrow. The amount by volume of MMT vs MTBE is preferably about 3:1. In other words, the fuel additive preferably comprises an amount of MMT that is 37.5 % v/v and an amount of MTBE that is 12.5 % v/v. The amount by volume of ferrocene vs toluene is preferably about 1:1. In other words, the fuel additive preferably comprises an amount of ferrocene that is 25 % v/v and an amount of toluene that is 25 % v/v. The expression “about” includes minor deviations up to 0.5 % v/v, preferably up to 0.2 % v/v.

The fuel additive of the present invention may be added to a base fuel, preferably a fuel for spark-ignition engines, more preferably a gasoline base fuel. Conventional amounts may be used, depending on the base fuel. For instance, the fuel composition may comprise from 20 to 1000 ppm preferably 100 to 500 ppm of the fuel additive relative to the fuel composition.

If the research octane number of a fuel composition needs to be enhanced, then the use of the fuel additive of the present invention may help. The current invention therefore also discloses a method for enhancing the research octane number of a fuel composition by adding the fuel additive of the present invention to a base fuel

Examples

For the following examples a “West African Fuel” (WAF) grade gasoline was used in a standardized single cylinder, four-stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions set out in ASTM D 2699: 91.6.

The RON of the base fuel is set out in the below Table. In comparative experiment 1, 150 ppm of an additive consisting of MMT was added to the base fuel. This significantly raised the RON, but at a premium cost. MMT is very expensive. In comparative experiment 2, 150 ppm of a blend consisting of a 50 MMT + 5 ferrocene + 45 toluene (in v/v%) was added to the base fuel. This too significantly raised the RON, but again at a high price. Changing the ratio of these additives did not show improved performance.

In comparative experiment 3, an amount of MMT is replaced with MTBE. Although this blend still shows an improvement vs the base oil, it appears that the replacement of the MMT with MTBE has resulted in a lesser improvement. This would suggest that the replacement of MMT with MTBE does not help. Surprisingly, when replacing about a quart of the MMT with MTBE, in other words, even more MMT, the same high performance as in Comparative experiment 2 is achieved, but at a lower price. This is experiment 4 in the below Table. Table 1 (relative amounts in % v/v)

The above results illustrate the surprising synergistic effect, at a reduced cost.