FUEL ADDITIVE CONTAINING AN IRON COMPLEX AND A LEAD COMPOUND

Abstract: The present invention relates to a fuel. The fuel comprises a composition comprising an iron complex and a tetraalkyl lead compound, characterised in that the concentration of elemental lead is from about 0.01g/litre to about 0.2g/litre and the concentration of elemental iron is from about 1 ppm to less than 30 ppm.

Description: FUEL ADDITIVE CONTAINING AN IRON COMPLEX AND A LEAD COMPOUND The present invention relates to a fuel. The present invention also provides a fuel additive for preparing the fuel. In particular, the present invention relates to fuels comprising new and improved antiknock compositions. These compositions are soluble in hydrocarbon motor fuels - i.e. fuels comprising one or more of saturates, olefins, naphthenes and aromatics. The fuel industry has long recognized the need for greater fuel economy and efficiency in the operation of gasoline powered spark- ignition engines. It is also recognized that the most economical burning of the fuel is obtained at the higher compression ratios, and so to obtain high performance in high compression ratio engines without the risk of knock damage, fuels need to be used with a high octane number and good anti-knock properties. While octane ratings of fuels can be improved by additional refining operations, the additional necessary refinery processes are extremely costly. Refiners have therefore blended anti-knock additives into their fuels to increase the octane number of the fuel. Numerous compounds have been suggested as anti-knock additives for fuel compositions. Anti-knock agents that have been used most are those of the organometallic type, and the most successful of these have been the organo-lead agents - such as tetraalkyl lead compounds. It is well known that tetraalkyl lead antiknock compounds are widely employed to improve the quality of fuels for spark-ignition engines. They do, however, suffer from the drawback that their antiknock effectiveness diminishes with increasing concentration. In order to overcome this disadvantage US-A-3353938 proposes the use of an antiknock composition which comprises 50% -85 % by weight of dicyclopentadienyl iron or substituted dicyclopentadienyl iron and 15%-50% by weight of cyclopentadienyl nickel nitrosyl or substituted cyclopentadienyl nickel. This Fe/Ni binary composition can be used in conjunction with a tetraalkyl lead antiknock compound. FR-A-1078519 also discloses a gasoline fuel that contains from 0.01 to 1 % by weight dicyclopentadienyl iron (i.e. from 100 ppm to 10,000 ppm iron complex) and 0.03 to 0.3% by weight of tetraethyl lead. Lead scavengers may also be present in amounts of 1 to 3 theories. We have now found that a particular combination of an iron complex and a tetraalkyl lead compound provides an improved antiknock composition. According to the present invention there is provided a fuel suitable for use as a fuel for a spark- ignition engine, wherein the fuel comprises an iron complex and a tetraalkyl lead compound, characterised in that the concentration of elemental lead is from about O.Olg/litre to about 0.2g/litre and the concentration of elemental iron is from about 1 ppm to less than 30 ppm. In a highly preferred embodiment, the concentration of elemental iron is from about 1 ppm to about 12 ppm. As used herein, the term "ppm" means μg per g. Hence, 12 ppm elemental iron means 12 μg elemental iron per gram of the fuel. According to the present invention there is also provided a composition comprising a tetraalkyl lead compound and an iron complex for use in preparing a fuel according to the present invention. The combined effect of the iron complex and the tetraalkyl lead compound is highly surprising. In particular, the fuel of the present invention has a high octane rating and to such an extent that an unexpected synergy is found. Another key benefit is that the present invention enables refiners to maximise the ultimate antiknock effects from additives while minimising their use of lead. In this regard, and by way of example, it is possible to reduce the elemental lead content of a gasoline to 0.05g Pb/litre but still get up to a 3 octane improvement compared with only a 2 octane enhancement if, for example, ferrocene (i.e. dicyclopentadienyl iron) is absent. Usually the tetraalkyl lead compound will be a tetra-lower alkyl lead, such as tetramethyl lead, tetraethyl lead (otherwise, commonly known as "TEL"), dimethyl ethyl lead, dimethyl diethyl lead, tri-ethyl methyl lead, tetraisopropyl lead, and the like, including mixtures thereof. There are numerous references to tetraalkyl lead compounds - such as TEL - in the art. For example, reference may be made to any one of the following US patents: 1705723, 1798593, 2004160, 2029301, 2000069, 241453, 2400383, 2043224, 3151142, 2515821, 2477465, 2464398, 1645375, 1652812, 1661809, 1661810, 1717961, 1907701, 1962173 and 2686799 (the contents of which are incorporated herein by reference). The tetraalkyl lead compound is typically prepared by known processes wherein lead/sodium alloy (PbNa) is reacted with an alkyl halide. There are numerous references to the preparation of tetraalkyl lead compounds - such as TEL - in the art. For example, reference may be made to any one of the following US patents: 2411453, 1661809 and 1661810 (the contents of which are incorporated herein by reference). Preferably, the tetraalkyl lead compound is TEL. Typically, the TEL is prepared by the reaction of lead/sodium alloy (PbNa) with ethyl chloride. The tetraalkyl lead compound and the iron complex can be used in conjunction with at least one lead scavenger - such as a poly-halo-hydrocarbon lead scavenger. A typical lead scavenger comprises from 2 to 8 carbon atoms and from 2 to 3 halogen atoms and has a boiling point less than 300 °C, preferably less than 210°C. Suitable scavengers are ethylene dibromide and ethylene dichloride. A preferred scavenger is dichloroethane or dibromoethane. The composition of the present invention may be used in conjunction with any suitable additive normally used in a motor fuel for a spark- ignition engine. Suitable additives include one or more of antioxidants, dyes, solvents, inert materials, perfumes etc. A typical solvent is an aromatic solvent with a high boiling range, such as Shellsol AB™ (supplied by Shell). The iron complex is preferably an iron complex of dicyclopentadienyl or substituted- dicyclopentadienyl, wherein the substituents can be, for example, one or more C,_ 5 alkyl groups, preferably C,_ 2 alkyl groups. A combination of such iron complexes may also be used. Suitable alkyl-substituted-dicyclopentadienyl iron complexes are cyclopentadienyl(methylcyclopentadienyl) iron, cyclopentadienyl(ethyl- cyclopentadienyl) iron, bis-(methylcyclopentadienyl) iron bis-(ethylcyclopentadienyl) iron, bis-(l,2-dimethylcyclopentadienyl) iron, iron pentacarbonyl, and bis-(l-methyl- 3-ethylcyclopentadienyl) iron. These iron complexes can be prepared by the processes taught in US-A-2680756, US-A-2804468, GB-A-0733129 and GB-A- 0763550 - the contents of which are incorporated herein by reference. Suitable iron complexes are dicyclopentadienyl iron and/or bis- (methylcyclopentadienyl) iron. A highly preferred iron complex is ferrocene (i.e. dicyclopentadienyl iron). The fuel of the present invention is preferably a motor fuel for a spark-ignition engine and typically consists of liquid hydrocarbons boiling in the petrol range - which is typically from about 15°C to about 250°C, preferably from about 20°C to about 230°C. These fuels are typically blends of various hydrocarbon fractions comprising one or more of saturates, naphthenes, paraffins, olefins, cycloaliphatic hydrocarbons and aromatic hydrocarbons. The base fuel - i.e. the fuel without the compositions of the present invention - can be any suitable refinery product obtained by any one or more of distillation, isomerisation, cracking, reforming, alkylation, hydrocracking, and polymerisation processes. The fuel typically has an initial boiling point of from about 15°C to about 60°C and a final boiling point of from about 150°C to about 250°C. Preferably the fuel has an initial boiling point of from 20°C to 40°C and a final boiling point of from 150°C to 230°C. More preferably the fuel has an initial boiling point of from 20°C to 40°C and a final boiling point of from 170°C to 200°C. We have found that if the concentration of elemental iron is above 30 ppm, most engines suffer from durability problems. We have also found that the concentration of elemental iron can even be up to just 12 ppm. Even at this concentration of iron, a good octane rating can be achieved and, furthermore, engines do not suffer from durability problems. Thus, a highly preferred embodiment of the present invention relates to fuels (and additives for making same) comprising up to about 12 ppm elemental iron. Preferably the concentration of elemental lead is from about 0.03g/litre to about 0.08g/litre. Preferably the concentration of elemental lead is from about 0.04g/litre to about 0.06g/litre. Preferably the concentration of elemental lead is about 0.05g/litre. Preferably the concentration of elemental iron is from about 6 ppm to about 12 ppm. Preferably the concentration of elemental iron is from about 7 ppm to about 10 ppm. Preferably the concentration of elemental iron is about 9 ppm. Preferably the tetraalkyl lead compound is at least tetraethyl lead. In one embodiment, the tetraalkyl lead compound is essentially only tetraethyl lead. Preferably the iron complex is at least ferrocene. In one embodiment, the iron complex is essentially only ferrocene. When the iron complex is essentially just ferrocene, then preferably the ferrocene should be present in a concentration of from about 1 ppm to about 40 ppm, more preferably in an amount of from about 20 ppm to about 40 ppm, even more preferably in an amount of about 30 ppm. Preferably, the fuel is petrol (or gasoline). The tetraalkyl lead compound can be in admixture with a lead scavenger and/or other suitable fuel additives. The lead scavengers are used to remove lead salts from the combustion chamber. These scavengers typically comprise halogenated compounds - and are otherwise known as lead halo-scavengers. When present, the lead halo-scavengers may be present in an amount of from about 1 to about 5 theories, preferably from about 1 to about 3 theories. A theory is 1 mole Pb to 2 moles halogen. Examples of suitable scavenger mixtures include: 1. Standard mixtures such as: 1 theory DBE (dibromoethane), i.e. "B" or Aviation mix; or 1 theory DCE (dichloroethane) plus 1/2 theory DBE, i.e. "CB" or Motor Mix. 2. Non-standard mixtures such as: scavenger mixes with different proportions of DBE and DCE or their mixes with other halogen scavengers For the present invention it may not be necessary to use such scavenger compounds, particularly when the lead levels are relatively low. Suitable tetraalkyl lead compound admixtures include: "TEL-B", i.e. 61.49% weight tetra ethyl lead plus 35.72% weight dibromoethane and necessary antioxidant, dye or inerts (solvent); "TEL-CB", i.e. 61.49% weight tetra ethyl lead plus 17.86% weight dibromoethane, 18.81 % weight dichloroethane and necessary antioxidant, dye or inerts; and "TEL-SF", i.e. 61.49% weight tetra ethyl lead plus necessary antioxidant, dye and high boiling aromatic solvent - such as Shellsol AB™ (supplied by Shell). In a highly preferred embodiment, the concentration of elemental lead is about 39.39% . The iron complex may be added as pure iron complex. Alternatively, the iron complex can be in admixture with another additive. A suitable iron complex admixture is 5-15% by weight solution of the iron complex in a high boiling solvent - such as Shellsol AB™ (supplied by Shell). Preferably the iron complex is added as any one of: the pure product, i.e. Fe(C 5 H 5 ) 2 containing 30% weight elemental iron; or an 8-10% by weight solution of ferrocene in high boiling solvent - such as Shellsol AB™ (supplied by Shell). Typically the base fuel has a research octane number ("RON") of 70-95. Preferably the base fuel has a RON of 75-90. More preferably the base fuel has a RON of 80-90. Preferable compositions according to the present invention are prepared by adding pure ferrocene to any one of TEL-CB, TEL-B or TEL-SF type products. A preferable mix is 33.5% weight elemental lead and 4.5% weight elemental iron and would be treated at 200 ppm into gasoline of 0.75 kg/litre density. This could be achieved by mixing 85.05% by weight of TEL-B, TEL-CB or TEL-SF with 14.95% by weight ferrocene. In addition, the concentration of elemental lead and iron can be increased by removal of solvent or dichloroethane and dibromoethane. These compositions are then added to the base fuel to yield the composition according to the present invention. Alternative, preferable compositions according to the present invention are prepared by adding the above-mentioned ferrocene solution to any one of TEL-CB, TEL-B or TEL-SF. A preferable mix is 36.2% TEL-CB, TEL-B or TEL-SF/63.8% ferrocene as 10% solution. This mix would contain 14.26% elemental lead and 1.91 % elemental iron and would be treated at 470 ppm. A further alternative preferable composition is prepared by blending pure TEL with 10% by weight solution of ferrocene in Shellsol AB™ (supplied by Shell). In particular, the product could be prepared by blending 25.9% by weight pure TEL with 74.1 % by weight of a 10% solution by weight of ferrocene in Shellsol AB™ (supplied by Shell). If required, appropriate dye and antioxidant could also be added. This yields a composition containing no scavengers but 16.6% by weight of lead and 2.22% by weight of iron. The composition could then be treated into gasoline at 405 ppm. The present invention also covers an additive composition that is used to form a fuel according to the present invention. In this regard, the composition can comprise the iron complex and the tetraalkyl lead compound admixed with a suitable carrier or diluent - such as a gasoline miscible liquid carrier or diluent. The carrier or diluent can be a liquid hydrocarbon, alcohol or ether, or mixture of two or more thereof, or can also be itself a gasoline blend, or base oil stock. When the additive composition is added to a raw fuel (i.e. fuel that does not the iron complex and/or the lead compound) the resultant fuel has a concentration of elemental lead in the range of from about O.Olg/litre to about 0.2g/litre and a concentration of elemental iron in the range of from about 1 ppm to less than 30 ppm, preferably up to about 12 ppm. The term "gasoline" includes blends of distillate hydrocarbon fuels with other additives such as anti-oxidants, detergents, demulsifiers, corrosion inhibitors, metal de-activators, dyes, deposit modifiers, other anti-knock additives (e.g. mefhy .cyclopentadienyl manganese tricarbonyl), oxygenates such as ethers and/or alcohols (e.g. ethanol) and the like. Anti-knock characteristics of an additive are typically evidenced by an increase in the research and motor octane numbers of the fuel when the additive is admixed therewith. The research octane numbers (RONs) and the motor octane numbers (MONs) of fuel compositions are typically measured by ASTM D 2699 and ASTM D 2700 respectively. RONs and MONs are good indicators of the antiknock characteristics of an additised fuel. Thus, the present invention provides a fuel suitable for use as a fuel for a spark- ignition engine, wherein the fuel comprises an iron complex and a tetraalkyl lead compound, characterised in that the concentration of elemental lead is from about O.Olg/litre to about 0.2g/litre and the concentration of elemental iron is from about 1 ppm to less than 30 ppm. In a preferred embodiment, the present invention provides a fuel suitable for use as a fuel for a spark- ignition engine, wherein the fuel comprises an iron complex and a tetraalkyl lead compound, characterised in that the concentration of elemental lead is from about O.Olg/litre to about 0.2g/litre and the concentration of elemental iron is from about 1 ppm to about 12 ppm. In a more preferred embodiment, the present invention provides a fuel suitable for use as a fuel for a spark-ignition engine, wherein the fuel comprises an iron complex and a tetraalkyl lead compound, wherein the iron complex is at least ferrocene and the tetraalkyl lead compound is at least TEL, characterised in that the concentration of elemental lead is from about O.Olg/litre to about 0.2g/litre and the concentration of elemental iron is from about 1 ppm to about 12 ppm. In a more preferred embodiment, the present invention provides a fuel suitable for use as a fuel for a spark-ignition engine, wherein the fuel comprises ferrocene and TEL, characterised in that the concentration of elemental lead is from about 0.03g/litre to about 0.08g/litre and the concentration of elemental iron is from about 6 ppm to about 12 ppm. In a more highly preferred embodiment, the present invention provides a fuel suitable for use as a fuel for a spark- ignition engine, wherein the fuel comprises ferrocene and TEL, characterised in that the concentration of elemental lead is about 0.05g/litre and the concentration of elemental iron is about 9 ppm. The present invention will now be described only by way of examples. In the following examples a series of base fuels and fuels according to the present invention were prepared as follows. The low octane gasolines were produced by taking a readily available unleaded gasoline base-stock and diluting it with low octane light straight run and straight run gasoline components to achieve the required blend octane. As indicated below the properties of the blends show that balanced gasoline properties were maintained in terms of: density; hydrocarbon composition; and distillation profile. The octane ratings of these fuels are shown in the following Tables. As can be seen, the compositions of the present invention increase the RON and/ or MON values of fuels. Thus, it is possible, for example, to reduce the level of elemental lead in a resultant fuel. TABLE 1 - GASOLINE BLENDING TABLE 2 - OCTANE RESPONSE DATA (20 ppm ferrocene = 6 ppm elemental iron; and 30 ppm ferrocene = 9 ppm elemental iron.) The results show that the compositions of the present invention surprisingly increase the octane rating of a base fuel. Other modifications will be apparent to those skilled in the art.

Claims: CLAIMS 1. A fuel suitable for use as a fuel for a spark-ignition engine, wherein the fuel comprises an iron complex and a tetraalkyl lead compound, characterised in that the concentration of elemental lead is from about O.Olg/litre to about 0.2g/litre and the concentration of elemental iron is from about 1 ppm to less than 30 ppm. 2. A fuel according to claim 1, wherein the concentration of elemental lead is from about 0.03g/litre to about 0.08g/litre. 3. A fuel according to claim 1 or claim 2, wherein the concentration of elemental lead is from about 0.04g/litre to about 0.06g/litre. 4. A fuel according to any one of claims 1 to 3, wherein the concentration of elemental lead is about 0.05g/litre. 5. A fuel according to any one of claims 1 to 4, wherein the concentration of elemental iron is from about 1 ppm to about 12 ppm. 6. A fuel according to any one of claims 1 to 5, wherein the concentration of elemental iron is from about 6 ppm to about 12 ppm, preferably from about 7 ppm to about 10 ppm. 7. A fuel according to any one of claims 1 to 6, wherein the concentration of elemental iron is about 9 ppm. 8. A fuel according to any one of the preceding claims, wherein the tetraalkyl lead compound is at least tetraethyl lead. 9. A fuel according to claim 8, wherein the tetraalkyl lead compound is essentially only tetraethyl lead. 10. A fuel according to any one of the preceding claims, wherein the iron complex is at least ferrocene. 11. A fuel according to any one of the preceding claims, wherein the iron complex is essentially only ferrocene. 12. A fuel according to any one of the preceding claims, wherein the fuel is petrol. 13. A composition comprising a tetraalkyl lead compound and an iron complex for use in preparing a fuel according to any one of claims 1-12. 14. A composition comprising a tetraalkyl lead compound and an iron complex as defined in any one of the preceding claims when used as an additive for fuel. 15. A fuel substantially as described herein. 16. A fuel additive comprising a composition according to claim 13 or claim 14.

Inventors: MULQUEEN SIMON CHRISTOPHER, RUSSELL TREVOR JOHN, THOMPSON ALISTAIR ASHLEY, MULQUEEN, SIMON, CHRISTOPHER, RUSSELL, TREVOR, JOHN, THOMPSON, ALISTAIR, ASHLEY
Applicants: ASS OCTEL, MULQUEEN SIMON CHRISTOPHER, RUSSELL TREVOR JOHN, THOMPSON ALISTAIR ASHLEY, MULQUEEN, SIMON, CHRISTOPHER, RUSSELL, TREVOR, JOHN, THE ASSOCIATED OCTEL COMPANY, THOMPSON, ALISTAIR, ASHLEY
Application year: 1998
Main classification: C10L1
IPC codes: C10L1, C10L10