DE69106611T2 - Motor fuels with increased properties. - Google Patents

Description

The invention relates to unleaded gasoline fuel compositions with superior environmental and performance properties.

It is well known that the light fractions of gasoline tend to escape into the atmosphere, especially in warm or hot weather; the removal of the light fractions reduces environmental pollution but reduces the octane quality of the gasoline. To compensate for this reduction in octane quality, increased proportions of aromatic gasoline hydrocarbons of the highest octane quality, such as benzene, toluene and xylene, can be used. However, since aromatics are undesirable, especially from a toxicological point of view, it would be desirable to find a way to reduce the front fraction volatility of gasoline without increasing the aromatic content.

International patent publication WO87/01384 describes unleaded gasoline compositions to which a combination of C₁₋₆ aliphatic alcohols, anti-knock agents based on tricarbonyl (cyclopentadienyl) manganese and aromatic hydrocarbons are added to improve emissions and other environmental problems.

US-A-4 139 349 describes unleaded gasoline compositions which comprise a synergistic combination of antiknock agents based on tricarbonyl-(cyclopentadienyl)-manganese and -(dicyclopentadienyl)-iron.

The unleaded gasoline composition of the invention has a Reid vapor pressure (ASTM Test Method D-323) of 8.5 psi (58.6 kPa) or less, preferably such of 8.0 psi (55.2 kPa) or less, with an aromatic hydrocarbon content of not more than 25% by volume and not more than 1/32 gram per gallon (0.008 g/l) of manganese in the form of at least one fuel-soluble tricarbonyl (cyclopentadienyl) manganese compound. The use of tricarbonyl (cyclopentadienyl) manganese compounds improves the octane quality of low Reid vapor pressure gasoline without increasing its volatility and without requiring an increase in the aromatics content. It has been found that these manganese compounds tend to have a greater octane improving effect in paraffinic and naphthalene hydrocarbons than is the case in aromatic gasoline hydrocarbons. Furthermore, the use of the fuels according to the invention results in a reduced emission of carbon monoxide and nitrogen oxides (NOx) during engine operation, while a small impact is felt at the exhaust level in terms of hydrocarbon emissions. In fact, they have no adverse effect on the exhaust gas catalysts and oxygen sensors of the type commonly used in current fuel vehicles. The fuels according to the invention are therefore "environmentally friendly".

In the improved processing of the gasoline, the tricarbonyl (cyclopentadienyl) manganese and the above-mentioned low Reid vapor pressure fuel are blended in a suitable manner, for example by (a) blending the fuel soluble additive with the gasoline during or after completion of the gasoline blending operations or (b) blending the additive with one or more hydrocarbon gasoline feed streams or other blending components, such as oxygenated fuel blending components, before the feed streams are blended together. The resulting octane-enriched gasoline has It can then be stored in at least one storage tank in a tank farm, if required, before delivery for use in internal combustion engine-powered vehicles. It can then be filled into the motor vehicles.

The use according to the invention reduces the amount of volatile hydrocarbons released during storage and/or refueling of motor vehicles. Compared to the corresponding fuels which do not contain tricarbonyl (cyclopentadienyl) manganese, the amount of carbon monoxide and nitrogen oxides released into the atmosphere during operation of the motor vehicles is reduced.

As noted above, the gasoline used in the practice of the present invention must have a Reid vapor pressure of 8.5 psi (58.6 kPa) or less, preferably 8.0 psi (55.2 kPa) or less. It is well known that the Reid vapor pressure is determined at a temperature of 100ºF (37.8ºC). Such gasolines are considered unleaded in the sense that no organic lead compounds are added to the fuel as antiknock agents, although they may contain trace amounts of lead impurities. The hydrocarbon gasoline bases used to form gasoline blends include distillate gasolines, naphthalene light fractions, cracked gasoline bases obtainable from thermal or catalytic cracking, hydrocracking or similar processes, reformed gasoline obtainable from catalytic reforming or similar processes, polymer gasolines obtained by polymerization of olefins, alkylated gasolines obtained by addition of olefins to isobutane or other hydrocarbons by alkylation processes, isomerate gasolines obtained by isomerization of short chain paraffins such as n-hexane, n-heptane and the like, as well as other hydrocarbons in the boiling point range of the gasoline, which are formed by suitable refinery processes. Suitable amounts of suitable hydrocarbons, which are formed by other processes, such as from coal or shale, are included if desired. For example, reforming products based on liquid fuels, which are formed by the Fischer-Tropsch process, can also be incorporated into the mixtures. In any case, the gasoline thus produced must satisfy the Reid vapor pressure requirements according to the invention, and this gasoline additionally has the distillation marking which is typical for conventional unleaded regular gasoline, conventional unleaded gasoline of medium quality, super or super premium quality.

Thus, the gasolines generally fall within the parameter range of ASTM D-4814 and typically have lower boiling points in the range of 70 to 115ºF (21.1 to 46.1ºC) and upper boiling points in the range of 370 to 440ºF (187.8 to 226.7ºC) as measured by the standard ASTM distillation method (ASTM D-86). The hydrocarbon composition of the gasoline grades based on volume percent of saturated fractions, olefins and aromatics is typically determined by ASTM Test Method D-1319.

In general, the base gasoline is a mixture of bases obtained from various refining processes. The final blend may also contain hydrocarbons obtained by other processes, such as alkylated mixtures prepared from the reaction of C₄-olefins and butane compounds under Use of an acid catalyst, such as sulphuric or hydrofluoric acid, and of aromatics, which can be produced by reforming.

The saturated gasoline components include paraffins and naphthenates. These saturated fractions are generally obtained from: (1) native gasoline by distillation (distillate gasoline), (2) alkylation processes (alkylation products), and (3) isomerization processes (conversion of normal paraffins into branched chain paraffins of higher octane quality). The saturated gasoline components are also found in so-called natural gasolines. In addition to the above, thermally cracked bases, catalytically cracked bases and catalytic reforming mixtures contain some amount of saturated components.

The olefinic gasoline components are usually formed using processes such as thermal and catalytic cracking. The dehydrogenation of paraffins to olefins can supplement the gaseous olefins present in the refinery during the production of feedstock for either polymerization or alkylation processes.

The base gasoline mixtures to which the tricarbonyl-(cyclopentadienyl)-manganese additive is added according to the invention generally contain between 40 and 80 vol.% saturated fractions, between 1 and 30 vol.% olefins and up to a maximum of 25 vol.% aromatics. The gasoline base mixtures that can be used according to the invention contain a maximum of 25 vol.% aromatics. The final fuel mixture preferably contains no more than 1 vol.%, most preferably a maximum of 0.8 vol.% benzene.

In particular, the unleaded gasolines used in the present invention not only meet the Reid vapor pressure criteria as set forth above, but are additionally characterized by having (1) a maximum sulfur content of 300 ppm, (2) a maximum bromine number of 20, (3) a maximum aromatics content of 20 volume percent, (4) a maximum benzene content of 1 volume percent, and (5) a minimum content of 1% oxygen in the form of at least one monoether or polyether, wherein the gasoline contains a maximum of 1/32 gram of manganese per gallon (3.8 L) dissolved in the form of tricarbonyl (methylcyclopentadienyl) manganese. Gasolines of this type which do not contain the manganese additive are sometimes referred to as reformulated gasolines, see, for example, Oil & Gas Journal, April 9, 1990, pp. 43-48.

From an octane rating point of view, the preferred base gasoline blends are those having an octane number (R + M)/2 in the range of 78 to 95.

Any tricarbonyl(cyclopentadienyl)manganese compound, for example those described in U.S. Patent No. 2,818,417, can be used in the invention. Illustrative examples of these manganese compounds include the tricarbonyl(cyclopentadienyl), (methylcyclopentadienyl), (dimethylcyclopentadienyl), (trimethylcyclopentadienyl), (tetramethylcyclopentdienyl), (pentamethylcyclopentadienyl), (ethylcyclopentadienyl), (diethylcyclopentadienyl), (propylcyclopentadienyl), (isopropylcyclopentadienyl), (tert-butylcyclopentadienyl), (octylcyclopentadienyl), (dodecylcyclopentadienyl), (ethylmethylcyclopentadienyl) and (indenyl) manganese compounds, and mixtures of two or three such compounds. Generally speaking, the preferred compounds or mixtures of compounds are those which at ordinary room temperature in the liquid state, such as tricarbonyl-(methylcyclopentadienyl)- or -(ethylcyclopentadienyl)-manganese and liquid mixtures of tricarbonyl-(cyclopentadienyl)- and -(methylcyclopentadienyl)-manganese, as well as mixtures of tricarbonyl-(methylcyclopentadienyl)- and -(ethylcyclopentadienyl)-manganese. The most preferred compound due to its easy commercial availability and its excellent combination of properties and effectiveness is tricarbonyl-(methylcyclopentadienyl)-manganese.

The following examples illustrate the practice of the invention and various embodiments thereof, with percentages of gasoline hydrocarbons being given as volume percent. These examples are not intended to limit the invention, nor are they intended to be construed as limiting.

EXAMPLE 1

An unleaded gasoline blend is produced containing 58.9% saturated hydrocarbons, 17.5% olefinic hydrocarbons, and 23.6% aromatic hydrocarbons, all components in the boiling range of gasoline. The Reid vapor pressure of the blend is 8.5 psi (58.6 kPa). Tricarbonyl (methylcyclopentadienyl) manganese is blended into this base fuel to a concentration of 1/32 g manganese per gallon (0.008 g/L) and 4-methyl-2,6-di-tert-butylphenol to a concentration of 7.5 pounds per 1000 barrels (21.4 g/m³). After storing the gasoline above water in a field storage tank in a tank farm, the product is transported by tank trucks to gasoline filling stations where it is used to fill motor vehicles on demand. The vehicles consume it during operation.

EXAMPLE 2

Unleaded gasoline according to the invention is prepared with a content of 56.9% saturated fractions, 20% olefins, and 23.1% aromatics, all components being in the boiling range of gasoline. The ingredients are selected in such a way that the Reid vapor pressure of the mixture is 8.4 psi (57.9 kPa). A mixture of tertiary, butylated phenolic antioxidants containing 85% by weight of 2,6-di-tert-butylphenol is mixed into the fuel to a concentration of 6.5 pounds per 1000 barrels (18.5 g/m³). The tricarbonyl-(methylcyclopentadienyl)-manganese is mixed into the resulting mixture to a concentration of 1/32 g manganese per gallon (0.008 g/l). This fuel is stored, transported and dispensed for operation and use in motor vehicles, the vast majority of which contain catalytic converters.

EXAMPLE 3

Into an unleaded gasoline (67.7% saturated fractions, 7.5% olefins, 24.8% aromatics) having a Reid vapor pressure of 8.0 are blended tricarbonyl (methylcyclopentadienyl) manganese and methyl tert-butyl ether in an amount such that the resulting fuel contains 1/32 manganese per gallon (0.008 g/L) and 2.7% by weight oxygen in the form of methyl tert-butyl ether. The finished fuel, optionally but preferably containing conventional amounts of an antioxidant, metal deactivator and carburetor cleaner, is dispensed and used in the operation of motor vehicles including passenger cars, buses, trucks, station wagons and motorcycles.

EXAMPLE 4

Examples 1 to 3 are repeated, but with the difference that in one case the respective motor fuels contain 1/40 g manganese per gallon (0.007 g/l), in another case the corresponding motor fuels contain 1/50 g manganese per gallon (0.005 g/l), and in a third case 1/64 g manganese per gallon (0.004 g/l) and in a further case 1/100 g manganese per gallon (0.003 g/l).

EXAMPLE 5

Examples 1 to 4 are repeated, but with the difference that in each case the tricarbonyl-(methylcyclopentadienyl)-manganese is replaced by the same concentration of manganese in the form of tricarbonyl-(cyclopentadienyl)-manganese.

EXAMPLE 6

Examples 1 to 4 are repeated, but with the difference that in a number of cases the respective fuel contains, instead of tricarbonyl-(methylcyclopentadienyl)-manganese, a mixture of 90% by weight of tricarbonyl-(methylcyclopentadienyl)-manganese and 10% by weight of tricarbonyl-(cyclopentadienyl)-manganese in an amount such that the respective fuels contain the same corresponding amounts of manganese as the fuels according to Examples 1 to 4. In another series of cases the respective fuels according to Examples 1 to 4 contain the same corresponding concentration of manganese in the form of tricarbonyl-(dimethylcyclopentadienyl)-manganese instead of tricarbonyl-(methylcyclopentadienyl)-manganese. According to a further series of examples, the specific manganese concentrations in the fuels according to Examples 1 to 4 are determined by the tricarbonyl-(tert-butylcyclopentadienyl)-manganese. In another series of examples, tricarbonyl-(indenyl)-manganese is used as a manganese additive in the manufacture of gasoline compositions instead of tricarbonyl-(methylcyclopentadienyl)-manganese.

EXAMPLE 7

An unleaded gasoline blend having a Reid vapor pressure of 7.8 psi (53.8 kPa) is formulated from 72.5% saturated fractions, 4.0% olefins, and 23.5% aromatics (of which less than 3% by volume is in the form of benzene so that the fuel has less than 1% by volume benzene). The methyl tert-butyl ether is blended into the base gasoline in an amount sufficient to provide an oxygen content of 2% by weight in the fuel. The tricarbonyl (methylcyclopentadienyl) manganese is then blended into the resulting motor fuel in an amount equivalent to 1/35 g manganese per gallon (0.008 g/l).

EXAMPLE 8

Example 7 is repeated except that (a) the initial gasoline mixture has a Reid vapor pressure of 7.9 psi (54.5 kPa) and is composed of 75.7% saturated fractions, 4.8% olefins and 19.5% aromatics (with less than 3.5% benzene by volume in the aromatic mixture), and (b) a mixture of methyl tert-butyl ether and ethyl tert-butyl ether is mixed into the fuel in an amount such that the oxygenated fuel mixture content is equivalent to 2.5% oxygen by weight.

EXAMPLE 9

Example 7 is repeated again, but with the difference that (a) the initial gasoline mixture has a Reid vapor pressure of 7.7 psi (53.1 kPa) and is composed of 78.6% saturated fractions, 4.4% olefins and 17.0% aromatics (the total fuel mixture again containing less than 1% by volume of benzene), and (b) instead of methyl tert-butyl ether, tert-amyl methyl ether is mixed into the gasoline in an amount which is equivalent to an oxygen content in the fuel of 2.7% by weight.

EXAMPLE 10

An anti-deposit additive in the form of a polyetheramine, which is sold by Oronite Chemical Co. under the name OGA-480, is mixed into the corresponding fuels according to Examples 7 to 9 at a concentration of 100 pounds per 1000 barrels (285.3 g/m³).

EXAMPLE 11

A polyalkenyl succinimide deposit control additive sold by Ethyl Petroleum Additives, Ltd. under the name HITEC 4450 additive is blended with the appropriate fuels as per Examples 7 to 9 at a concentration of 100 pounds per 1000 barrels (285.3 g/m³).

EXAMPLE 12

An anti-deposit additive, which is sold by Oronite Chemical Co. under the name OGA-472, is mixed with the respective fuels according to Examples 7 to 9 at a concentration of 100 pounds per 1000 barrels (285.3 g/m³).

As can be seen from the above examples, the fuels according to the invention can optionally, but preferably, contain additional additives in addition to the tricarbonyl (cyclopentadienyl) manganese compound(s). Such additional additives include antioxidants, anti-deposit additives (also known as induction system cleanliness additives or fuel detergents) and oxygenated substances such as dialkyl ethers, but in any case with the proviso that the volatility of such substances in the fuel does not cause the Reid vapor pressure limits required by the invention to be exceeded. Other additives can be used, including additional anti-knock agents such as aromatic amine anti-knock agents such as N-methylaniline, iron-containing anti-knock agents such as ferrocene, methylferrocene, and tricarbonyl-(butadiene)-iron, and nickel anti-knock agents such as nitrosyl-(cyclopentadienyl)-nickel. Corrosion inhibitors, metal deactivators, anti-emulsion agents, and dyes, which are other types of additives, can also be used.

The oxygenated materials preferably used according to the invention can optionally, but preferably, be mixed into the fuels and are ethers of suitably low volatility, such as methyl tert-butyl ether, ethyl tert-butyl ether, tert-amyl methyl ether and 2,2-diethyl-1,3-propanediol. Useful fuel-soluble esters and alcohols of suitably low volatility are, for example, tert-butyl acetate, 1-hexanol, 2-hexanol, 3-hexanol and polyethoxyethanols. For Usually, such oxygenated compounds are used in an amount sufficient to provide up to 3 and 4% by weight of oxygen in the fuel, provided that such use is compatible with existing or proposed legislation. Other suitable oxygenated blending ingredients include p-cresol, 2,4-xylene, 3-methoxyphenol, 2-methylfuran, cyclopentanone, isovaleraldehyde, 2,4-pentanedione and similar oxygen-containing substances.

The preferred antioxidants for the fuels according to the invention are (sterically) hindered, phenolic antioxidants, such as, for example, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-butyl-2,6-di-tert-butylphenol and mixtures of tertiary, butylated phenols, predominantly in the form of 2,6-di-tert-butylphenol. In individual cases, aromatic amine antioxidants may prove useful either when used alone or in combination with a phenolic antioxidant. The antioxidants are usually used in amounts of up to 25 pounds per 1000 barrels (71.3 g/m³), with the amount used in each case depending on the stability of the gasoline (e.g. the olefin content).

Another preferred type of additive used in the fuels of the present invention are the group of ashless detergents such as polyetheramines, polyalkyleneamines, alkenylsuccinimides, polyetheramideamines and the like. Such materials can be used at effective concentrations ranging between 50 and 500 pounds per barrel (142.6 to 1426.4 g/m³), with more common concentrations ranging between 100 to 200 pounds per 1000 barrels (285.3 to 570.6 g/m³).

The tricarbonyl (cyclopentadienyl) manganese compounds as well as the other additional additives or blending agents can be mixed with the base fuels in accordance with well-known procedures which require conventional mixing equipment. The invention extends to any fuel composition which meets the basic requirements of the invention.

Claims (27)

1. Unleaded gasoline composition having a Reid vapor pressure (ASTM Test Method D-323) of 8.5 psi (58.6 kPa) or less, containing not more than 25% by volume of aromatic hydrocarbon components and not more than 1/32 gram per gallon (0.008 g/L) of manganese in the form of at least one fuel-soluble tricarbonyl (cyclopentadienyl) manganese compound. 2. The composition of claim 1 wherein the Reid vapor pressure of the gasoline is 8.0 psi (55.2 kPa) or less. 3. Composition according to claim 1 or 2, in which at least one fuel-soluble tricarbonyl-(cyclopentadienyl)-manganese compound consists essentially of tricarbonyl-(methyl-cyclopentadienyl)-manganese. 4. A composition according to claims 1, 2 or 3, wherein the base gasoline contains less than 1% by volume of benzene. 5. Composition according to one of the preceding claims, in which the base gasoline contains at least 50% by volume of saturated hydrocarbon components. 6. Composition according to one of the preceding claims, in which the fuel composition additionally contains up to about 4% by weight of oxygen in the form of at least one oxygenated fuel blending component. 7. Unleaded gasoline composition according to claim 1, which comprises a gasoline with a maximum sulfur content of 300 ppm, a maximum bromine number of 20, a maximum aromatics content of 20 vol.%, a maximum benzene content of 1 vol.% and a minimum oxygen content in the form of at least one monoether or polyether in an amount of 1 wt.%. 8. Composition according to claim 6 or 7, in which the oxygenated fuel blending component or the monoether is in the form of methyl tert-butyl ether or methyl tert-amyl ether. 9. Composition according to one of the preceding claims, wherein the fuel composition additionally contains at least one ashless detergent. 10. The composition of claim 9 wherein the detergent is selected from polyetheramines, polyalkenylamines, alkenylsuccinimides and polyetheramideamines and is present in an amount ranging from 50 to 500 pounds per 1000 barrels (142.6 to 1426.4 g/m³). 11. Composition according to one of the preceding claims, in which the fuel composition additionally contains at least one antioxidant. 12. Composition according to claim 11, in which the antioxidant is present as a (sterically) hindered phenolic antioxidant. 13. A process for producing gasoline which comprises producing an unmodified base gasoline having a Reid vapor pressure (ASTM Test Method D-323) of 8.5 psi (58.6 kPa) or less containing less than 25% by volume of aromatic hydrocarbons, wherein a maximum of 1/32 gram of manganese per gallon (0.008 g/l) is provided therein in the form of at least one fuel-soluble tricarbonyl (cyclopentadienyl) manganese compound. 14. The method of claim 13, wherein the Reid vapor pressure of gasoline is 8.0 psi (55.2 kPa) or less. 15. A method according to claim 13 or 14, which additionally comprises the inclusion of approximately 4% by weight of oxygen in the form of at least one oxygenated fuel blending component in the gasoline. 16. The method of claim 15, wherein the oxygenated fuel blending component is in the form of at least one monoether or polyether. 17. A method according to any one of claims 13 to 16, which additionally comprises incorporating at least one deposit control additive into the gasoline, the former also being known as an induction system cleanliness additive or fuel detergent. 18. The method of claim 17, wherein the anti-deposit additive is selected from polyetheramines, polyalkenylamines, alkenylsuccinimides and polyetheramideamines. 19. A process according to any one of claims 13 to 18, which additionally comprises incorporating into the gasoline about 25 pounds per 1000 barrels (71.3 g/m³) of one or a mixture of hindered phenolic antioxidants. 20. Using a maximum of 1/32 gram per gallon (0.008 g/L) of manganese in the form of at least one fuel-soluble tricarbonyl (cyclopentadienyl) manganese compound in an unleaded gasoline composition having a Reid vapor pressure (ASTM Test Method D-323) of 8.5 psi (58.6 kPa) or less and containing not more than 25% by volume of aromatic hydrocarbon components for the purpose of reducing carbon dioxide and nitrogen oxide (NOx) emissions during engine operation. 21. Use of manganese according to claim 9 in the form of tricarbonyl (cyclopentadienyl) manganese in an unleaded gasoline composition having a maximum Reid vapor pressure (ASTM test method D-323) of 8.5 psi (58.6 kPa), a maximum sulfur content of 300 ppm, a maximum bromine number of 20, a maximum aromatics content of 20 vol. %, a maximum benzene content of 1 vol. % and a minimum oxygen content of 1 wt. % in the form of at least one mono- or polyether. 22. Use according to claim 20 or 21, wherein the Reid vapor pressure of the unleaded gasoline is 8.0 psi (55.2 kPa) or less. 23. Use according to one of claims 20 to 22, in which the unleaded gasoline additionally contains up to about 4% by weight of oxygen in the form of at least one oxygenated fuel blending component. 24. Use according to claim 23, wherein the oxygenated fuel blending component is in the form of at least one mono- or polyether. 25. Use according to one of claims 20 to 24, in which the unleaded petrol additionally contains at least one anti-deposit additive, which is also known as an induction system cleanliness additive or fuel detergent. 26. Use according to claim 25, wherein the anti-deposit additive is selected from polyetheramines, polyalkenylamines, alkenylsuccinimides and polyetheramideamines. 27. Use according to any one of claims 20 to 26, wherein the unleaded gasoline additionally contains up to about 25 pounds per 1000 barrels (71.3 g/m³) of one or a mixture of (sterically) hindered phenolic antioxidants.