RU2737165C2 - Method and composition for improving combustion of aviation fuel - Google Patents

Abstract

FIELD: fuel industry.SUBSTANCE: invention discloses an aviation fuel composition which contains (a) from about 10 to about 80 % by volume of an aviation alkylate; (b) from about 5 to 50 % by volume of isooctane; (c) from about 5 to about 20 volume percent isopentane; (d) from about 5 to about 30 volume percent aromatic hydrocarbons, selected toluene, mesitylene or combinations thereof; (e) from about 0.5 to 500 mg of Mn/l of manganese methylcyclopentadienyl tricarbonyl; and (f) a manganese purification compound containing tricresyl phosphate, wherein said composition is substantially lead-free and said composition has an octane number of at least about 96, determined using ASTM D2700 testing method. Also disclosed is an aviation fuel additive composition and a method for increasing the octane number of substantially lead-free aviation fuel to produce aviation fuel composition by introduction of additive into base fuel.EFFECT: technical result consists in provision of high detonation resistance of aviation fuel composition.15 cl, 6 dwg, 4 ex

Description

This application is a partial continuation of US patent application Serial No. 14/994199, filed January 13, 2016, incorporated herein by reference in its entirety.

The present invention relates to substantially lead-free aviation fuel compositions. The present invention is further directed to the use of these aviation fuels, which also include a manganese-containing additive and optionally isooctane to increase the octane number of the fuel, and a refining compound.

LEVEL OF TECHNOLOGY

For at least regulatory reasons, aviation fuels are involved in the production of lead-free fuels. Removing lead from the fuel, however, has the undesirable effect of reducing the knock resistance of the fuel. Accordingly, when aviation fuels are made lead-free, the composition of these fuels must take into account the octane reduction due to lead removal. The addition of other fuel components is required.

A common way to improve octane is by introducing large amounts of aromatic hydrocarbons into aviation fuel. These aromatic hydrocarbons produce lead-free fuels, but still meet the requirements for knock resistance. However, the use of significant amounts of aromatic hydrocarbons in aviation fuel alters the combustion efficiency of that fuel and results in increased smoke production during the combustion process. Not to mention, increased amounts of smoke are undesirable in terms of aesthetics and environmental impact. Generally speaking, the greater the amount of aromatic hydrocarbons incorporated into the fuel, the greater the amount of smoke that is generated during the combustion of that fuel.

Another strategy to improve the octane number is to add a manganese additive to aviation fuel. Manganese additives allow for lead-free fuel, but still improve the requirements for knock resistance relative to fuel composition without additives and without lead.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to define an aviation fuel composition that includes a high aromatics content to increase octane along with an effective amount of a manganese compound to reduce smoke generated during the combustion of aviation fuel. Alternatively, the aviation fuel composition may include manganese to improve octane and a purifier to reduce engine manganese oxide build-up. One such useful cleaner is tricresyl phosphate. Also alternatively, the aviation fuel composition may include isooctane and / or isopentane to improve the octane rating of the fuel.

In one example, the substantially lead-free aviation fuel composition contains from 0 to about 80 volume percent aviation alkylate. The fuel composition in this example contains from about zero to 50 volume percent isooctane and from about zero to 20 volume percent isopentane. The fuel composition further contains from about zero to about 30 volume percent aromatic hydrocarbons. And the fuel composition contains about 0.5 to 500 mg Mn / L of one or more manganese cyclopentadienyl tricarbonyl compounds and a manganese stripping compound. This composition is substantially free of lead and has an octane number of at least about 96 according to ASTM D 2700 test method.

In another example, a method for reducing the amount of smoke that is generated from the combustion of aviation fuel comprises several steps. This method includes providing a spark-ignited aircraft engine and providing a substantially lead-free aviation fuel composition as described herein. The method further comprises combusting a given aviation fuel composition in a given engine to form an exhaust jet, wherein the jet contains less smoke than a comparable aviation fuel composition that is otherwise identical, but the comparable aviation fuel composition is substantially free of manganese. ...

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a graph showing comparative emission opacity.

Figure 2 is a bar graph that shows the average opacity of emissions for each of the ten second periods during the first 40 seconds of combustion.

Figure 3 is a bar graph depicting comparative time to ignition test.

Figure 4 is a table comparing octane numbers for various additive components in combination with increasing amounts of manganese compounds.

Figure 5 is a table of calculated MON and energy content for various alternative aviation fuel compositions.

Figure 6 is a flowchart of a calculation that resulted in the calculated MON and energy content in Figure 5.

DETAILED DESCRIPTION

The aviation fuel described herein is a lead-free fuel composition that may or may not include significant aromatics. As an aviation fuel, this fuel may include aviation alkylates. More specifically, the fuel composition described herein will further have an aromatic hydrocarbon content of from about zero to about 30 volume percent. To compensate for smoke generated during the combustion of aromatics-containing fuel, from 0.5 to 500 mg Mn / L is added to the fuel composition. The resulting fuel has a minimum octane rating of at least about 96, or alternatively at least about 98, or alternatively at least about 99.5, determined according to ASTM D 2700 test method. Even more conventional fuels aviation alkylates and aromatic hydrocarbons benefit from the addition of manganese, as described, improving the octane rating of the fuel.

It also describes a method for reducing the amount of smoke that is generated from the combustion of lead-free aviation fuel. Aviation fuels, which can include aviation alkylates and about 20 to 90 percent aromatics, produce an increase in visible smoke and particulate matter during combustion. By adding about 0.5 to 500 mg Mn / L of one or more cyclopentadienyl manganese tricarbonyl compounds, the amount of smoke that occurs in the exhaust jet is reduced compared to the same aviation fuel composition, which is identical except that it is essentially does not contain any manganese.

Even in aviation fuel, which may include a conventional aviation fuel composition of aviation alkylates, aromatic hydrocarbons and isopentane, and in another example, by adding from about 0.5 to 500 mg Mn / L of one or more manganese cyclopentadienyl tricarbonyl compounds, the octane number of the fuel composition is improved to at least about 96 or about 98 octane, or alternatively about 99.5. An additional kit that includes manganese in an amount of from 0.5 to 500 mg Mn / L, or alternatively from 1 to 250 mg Mn / L, or even alternatively from about 125 to 225 mg Mn / L, may also include an antioxidant and one or several cleaning components. The cleansing component in one example can be tricresyl phosphate (TCP), phosphorus-containing organic oligomers, or DMMP (dimethylmethylphosphonate). TCP can be added in an effective amount to remove manganese combustion products. Without limiting this explanation, it is believed that the compound formed by the combustion of a manganese compound (eg MMT) and a phosphorus compound (eg TCP) may be manganese phosphate particles. In one embodiment, TCP is used in an amount that is approximately stoichiometric for the ratio of manganese to phosphorus. Alternatively, TCP can be added in the range from about 1: 0.1 to 1:10 manganese to phosphorus, or alternatively from about 1: 0.5 to 1: 3.

Manganese oxide deposits can form when a manganese compound is used as an additive in an aviation fuel composition. A formulation that includes the cleaners described herein can significantly reduce the occurrence of any manganese oxide deposits in an engine.

It has been found that the benefits of a scrubber in reducing or modifying manganese deposits can, however, have a negative impact on the octane rating of the aviation fuel composition. In addition, the use of a manganese additive may have practical limits with regard to octane improvements. Accordingly, it has been found that the addition of isooctane to a fuel composition, especially in combination with a manganese-containing component and especially with a cyclopentadienyl manganese tricarbonyl compound, can significantly improve the octane number of the fuel composition. More specifically, isooctane can eliminate the negative effect of a manganese scavenger on octane.

The introduction of isooctane is intuitively incomprehensible in the context of aviation fuel compositions. Traditionally, aviation fuels are refined to remove isooctane. This isooctane is then a distillation fraction that is sold separately. It has never been previously considered in an aviation fuel composition or additive kit.

The amount of isooctane in the final fuel composition can vary depending on the parameters of the particular base fuel. The amount of isooctane may also vary with the amount of manganese additive used. The isooctane is expected to comprise from about zero to about 50 volume percent of the fuel composition, or alternatively from about 5 to about 25 volume percent, or alternatively from about 10 to 20 volume percent. When incorporated into an additive, the relative amount of isooctane must be adequate to obtain the desired concentrations of the final fuel composition. It will depend on the octane rating of the base fuel and the amount of other additives used.

Isooctane is also added to the aviation fuel composition with a proportion of isopentane. Some isopentane, for example from about zero to 20 percent by volume, or alternatively from about 5 to 10 percent by volume, is required to meet the additional physical distillation requirements of the aviation fuel composition.

For the purposes of this application, a fuel composition is described in ASTM 4814 as substantially "lead-free" or "lead-free" if it contains 13 mg lead per liter of fuel or less (or about 50 mg Pb / gal or less). Alternatively, the terms "lead-free" or "lead-free" mean approximately 7 mg of lead per liter of fuel or less. Still alternatively, this means a substantially undetectable amount of lead in the fuel composition. In other words, there may be trace amounts of lead in the fuel; however, the fuel is substantially free of any detectable amount of lead. It should be understood that the fuels are lead-free in the sense that the lead-containing anti-knock agent is not intentionally added to the gasoline. Trace amounts of lead due to equipment contamination or similar circumstances are acceptable and are not considered excluded from the fuels described herein.

The aviation fuel composition described herein typically contains aviation alkylates. These components can make up about 10 to 80 percent by volume of the fuel. Aromatic hydrocarbons can be added to the fuel to improve the octane rating of the fuel. These aromatic hydrocarbons are added according to one example of the present invention in an amount of about zero to about 30 percent by volume of the fuel composition. In another example, aromatic hydrocarbons are added in an amount of about 10 to 20 percent by volume of the fuel composition.

The fuel mixture may contain aromatic gasoline hydrocarbons, at least most of which are mononuclear aromatic hydrocarbons such as toluene, xylenes, mesitylenes, ethylbenzene, etc. Other suitable possible gasoline hydrocarbons that can be used in the aviation fuels described herein, include isopentane, light fractions of hydrocracked gasoline and / or C _5-6 gasoline isomerate.

Compounds tricarbonyl cyclopentadienyl manganese, which can be used in the practice described herein fuels include tricarbonyl cyclopentadienyl manganese tricarbonyl methylcyclopentadienyl manganese tricarbonyl dimethylcyclopentadienyl manganese tricarbonyl trimethylcyclopentadienyl manganese tricarbonyl tetramethylcyclopentadienyl manganese tricarbonyl pentamethylcyclopentadienyl manganese tricarbonyl ethylcyclopentadienyl manganese tricarbonyl diethylcyclopentadienyl manganese tricarbonyl propylcyclopentadienyl manganese tricarbonyl isopropylcyclopentadienyl manganese, tricarbonyl tert-butylcyclopentadienyl manganese, tricarbonyl octylcyclopentadienyl manganese, tricarbonyl dodecylcyclopentadienyl manganese, tricarbonyl ethylmethylcyclopentadienyl manganese, mixtures of tricarbonyl manganese or more such compounds, including tricarbonyl of two indenyl. Preferred are cyclopentadienyl manganese tricarbonyls, which are liquid at room temperature, such as tricarbonyl methylcyclopentadienyl manganese tricarbonyl, ethyl cyclopentadienyl manganese tricarbonyl, liquid mixtures of manganese cyclopentadienyl tricarbonyl and manganese methylcyclopentadienyl tricarbonyl, methylcyclopentadienyl ethyl manganese tricarbonyl, mixtures of methylcyclopentadienyl methylcarbonyl and methylpentadienyl tricarbonyl of this invention. an amount of one or more of the above cyclopentadienyl manganese tricarbonyls, sufficient to provide the required octane number and valve seat wear parameters.

Other components that can be used, and in certain circumstances are preferably used, include colorants that do not contribute to excessive build-up of deposits in the system. Typical dyes that can be used are 1,4-dialkylaminoanthraquinone, p-diethylaminoazobenzene (color index # 11020 or aniline yellow color index # 107), methyl derivatives of azobenzene-4-azo-2-naphthol (methyl derivatives of color index # 26105) , alkyl derivatives of azobenzene-4-azo-2-naphthol, or equivalent materials. The quantities used should, whenever possible, meet the limits specified in ASTM specification D 910-90.

Antioxidants such as 2,6-di-tert-butylphenyl, 2,6-di-tert-butyl-p-cresol, phenylenediamines such as N, N'-di-sec-butyl-p-phenylenediamine, N α-isopropylphenylenediamine and the like. Of course, other antioxidants may be used depending on different base fuels and performance requirements.

Fuel system icing inhibitors may also be included in the fuels described herein. Ethylene glycol monomethyl ether and isopropyl alcohol are preferred, although materials giving equivalent characteristics may be considered suitable. The quantities used should, whenever possible, meet the limits specified in ASTM specification D 910-90.

The manganese stripping compound can be any compound that interacts with the manganese-containing additive component. By "purification" herein is meant contacting, combining, reacting, embedding, chemically bonding with or on, physically bonding with or on, adhering to, agglomerating with, attaching, deactivating, processing, inerting, consuming, fusing, collecting, refining, consuming, modification, transformation, or any other method or means by which the first material produces a second material that is not available or less available. Examples of manganese scavengers include phosphorus compounds, organobromides, and tricarbonyls. As explained earlier, these purifiers can have different effects on the octane rating of fuels containing a manganese compound. Accordingly, the amount of isooctane can be varied to maintain the octane number.

In the case of a phosphorus-containing scrubber, the scrubber may be added in an amount in a stoichiometric ratio of Mn to P from about 1: 0.1 to 1:10, or alternatively from about 1: 0.5 to 1: 3.

Example 1

A spark ignition engine was used to demonstrate a typical aviation fuel and a corresponding reduction in smoke production from combustion of this fuel. The spark ignition engine was actually the car engine for the 1994 Chevrolet Silverado. This car engine is unable to run on clean aviation fuel, so a mixture of 50% EEE gasoline and 50% aviation fuel was used. The aviation fuel mixture was based on 83% mesitylene and 17% isopentane. An idle test was started and the emission opacity was measured. In this test, as shown in FIG. 1, the opacity leveled off to approximately zero just before 40 seconds of run for both the control fuel composition (no added Mn) and the control fuel mixed with a manganese compound. The opacity of the control base fuel was much higher than the opacity of the base fuel mixed with the manganese component, including reducing the opacity to at least about 75% as shown. The drop in opacity can alternatively be about 10% -60%, or alternatively about 25% -50%, which is also shown. More specifically, the manganese component that was blended was HITEC®3000, which gave a manganese content of 18 milligrams of manganese per liter of fuel. Note that smoke production was highly dependent on the air / fuel ratio. In addition, the particulate control unit for the test engine was able to adapt the air / fuel ratio in approximately 35 seconds, eliminating fumes generated by combustion.

Finally, referring to Figure 2, the average opacity for each of the 10 second periods during the first 40 seconds of combustion demonstrates that in each case, the opacity of the untreated fuel was significantly greater than the opacity of the fuel that includes the addition of manganese.

Example 2

In another example, an add-on kit was added to lead-free aviation fuel to improve the octane rating of the fuel. The base lead-free aviation fuel contained 72% aviation alkylates, 20% aromatic hydrocarbons, 8% isopentane, and an MOR of 93 (ASTM D2700 method). An add-on kit containing 125 mg Mn / L and 2.12 g / gal (0.56 g / L) tricresyl phosphate (TCP) was added to the base fuel to increase the octane number to 96.

It was found that the resulting values of combustion engine deposits containing manganese oxides were greatly reduced by the addition of a phosphorus compound. Testing was performed on a Honda Accord on a chassis dynamometer. An automotive on-board diagnostic (OBD) system was used to monitor spark plug misfire. The car was started on comparative fuel compositions until the OBD system showed a cylinder flash pass. The tested formulations containing MMT and TCP cleaner had a significantly longer time to skip cylinder flash than the tested formulations containing only MMT.

As shown in Figure 3, fuels # 1 and # 2 were run on test vehicles and contained 250 and 125 mg Mn / L, respectively. Fuel # 3 contained both 125 mg Mn / L and a purifier, and the improved parameters are clearly visible in the graph in figure 3.

Thus, Example 2 illustrates a method for delaying or eliminating a missed cylinder flash caused by the buildup of manganese oxide deposits in an engine that result from the combustion of an aviation fuel composition containing manganese, the method comprising the steps of:

providing an aircraft engine with spark ignition;

providing a substantially lead-free aviation fuel composition comprising:

(a) from about 10 to about 80 volume percent aviation alkylate;

(b) from about 20 to about 90 volume percent aromatic hydrocarbons;

(c) from about 0.5 to 500 mg Mn / L of one or more cyclopentadienyl manganese tricarbonyls; and

(d) an effective amount of a phosphorus compound such as tricresyl phosphate;

where the composition is substantially lead-free, and the composition has a minimum octane value of at least about 96, determined using the ASTM D2700 test method;

combustion of the aviation fuel composition in the engine creates deposits in the engine;

wherein these engine deposits contain less manganese oxide compared to deposits obtained from combustion of a comparable aviation fuel composition that is otherwise identical, but the comparable aviation fuel composition is substantially free of any phosphorus-containing material, such as tricresyl phosphate.

Example 3

A number of tests run to determine the effect on the MON (motor octane number) of increasing amounts of manganese additives in these examples methylcyclopentadienyl manganese tricarbonyl (MMT ^®). Figure 4 shows the test results.

According to these results, the alkylate, which contains a certain percentage of isooctane, which depends on the conditions of the alkylation unit, has a strong response to MMT. But less octane components respond strongly to MMT.

Toluene, although a high octane component, does not respond to MMT at any amount of processing. This is typical for aroma components.

Isopentane (which is added to meet distillation specifications) responds strongly to MMT. But isopentane has a lower initial MOF, so it will respond strongly to MMT.

Isooctane does not respond to MMT as strongly as alkylate or isopentane, but has the highest MOR at 225 mg Mn / L compared to alkylate or isopentane. Therefore, isooctane is used because it is a high-octane component that additionally strongly responds to MMT (compared to toluene).

Example 4

Based on actual experimental results and a number of tests, including, but not limited to, the results in Figure 4, and on extrapolations and calculations, Figure 5 shows the calculations for MOF and energy content (Btu / f) for the compared aviation fuel compositions. As seen, the fuels contain different amounts of aviation alkylate aromatic hydrocarbons (using toluene as an example), isopentane, isooctane, phosphorus cleaner (using tricresyl phosphate as an example), manganese compound (using MMT ^®, including tricarbonyl cyclopentadienyl manganese as an example) and a possible antioxidant.

Different but similar calculations can be used to obtain the calculated MOF and energy content. More actual experimental results or more model derivatives can be used. Figure 6 is a flow diagram of the calculations used to arrive at the calculated MOR results in Figure 5. Similar calculations can be used for the energy content, which is also shown in Figure 5. A combination of actual test results and derived models was used in conjunction with ASTM D3338 to determine the total the heat of combustion of aviation fuels.

Other embodiments of the present application will be apparent to those skilled in the art from a review of this description and the practice of the invention disclosed herein. Unless otherwise indicated, all numbers expressing ingredient amounts, properties such as molecular weight, percentage, ratio, reaction conditions, and so on, used in this specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless otherwise indicated, the numerical parameters set forth in the description and the claims are approximations that may vary depending on the desired properties to be obtained using the present invention. At least and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be considered in light of the number of significant digits presented and using conventional rounding techniques. Although the numerical ranges and parameters representing the general scope of the invention are approximations, the numerical values given in the specific examples are indicated as precisely as possible. Any numerical value, however, invariably contains certain errors, necessarily arising from the standard deviation found in the corresponding measurements when they are tested. It is intended that this description and examples are to be construed as typical only, while the true scope and spirit of the invention are shown in the following claims.

Claims (29)

1. Composition of aviation fuel containing: (a) from about 10 to about 80 volume percent aviation alkylate; (b) from about 5 to 50 volume percent isooctane; (c) about 5 to 20 percent by volume isopentane; (d) from about 5 to about 30 volume percent aromatic hydrocarbons, selected toluene, mesitylene, or combinations thereof; (e) from about 0.5 to 500 mg Mn / L of methylcyclopentadienyl manganese tricarbonyl; and (f) a compound for purification of manganese containing tricresyl phosphate; wherein the composition is substantially lead-free and the composition has an octane value of at least about 96 as determined by the ASTM D2700 test method. 2. The aviation fuel composition of claim 1, comprising from about 15 to about 20 volume percent aromatic hydrocarbons. 3. The aviation fuel composition of claim 1 comprising about 5 to about 10 volume percent isopentane. 4. The aviation fuel composition of claim 1, wherein substantially lead-free means 13 mg of lead or less per liter of the fuel composition. 5. The aviation fuel composition of claim 1, wherein substantially lead-free means about 7 mg of lead or less per liter of the fuel composition. 6. The aviation fuel composition of claim 1, wherein substantially lead-free means a substantially undetectable amount of lead in the fuel composition. 7. The aviation fuel composition of claim 1, wherein the fuel composition contains from about one to about 250 mg Mn / L. 8. The aviation fuel composition of claim 1, wherein the fuel composition contains about 125 to 225 mg Mn / L. 9. The aviation fuel composition of claim 1, wherein the composition has an octane rating of at least about 100 as determined by the ASTM D 2700 test method. 10. The aviation fuel composition of claim 1, wherein the tricresyl phosphate is present in an amount representing a stoichiometric ratio of Mn to P of about 1: 0.1 to 1:10. 11. The aviation fuel composition of claim 1, wherein the tricresyl phosphate is present in an amount representing a stoichiometric ratio of Mn to P of about 1: 0.5 to 1: 3. 12. An aviation fuel additive composition intended to obtain an aviation fuel composition according to claim 1, comprising: (a) isooctane and isopentane in amounts providing from about 5 to about 50 vol% isooctane and from about 5 to about 20 vol% isopentane in the aviation fuel composition; (b) tricarbonyl methylcyclopentadienyl manganese in an amount providing from about 0.5 to about 500 mg Mn / L in the aviation fuel composition; and (c) a compound for purification of manganese containing tricresyl phosphate; however, this additive is essentially lead-free. 13. An aviation fuel additive composition according to claim 12, wherein the manganese decontamination compound contains several phosphorus-containing compounds. 14. A method for increasing the octane number of substantially lead-free aviation fuel to obtain an aviation fuel composition according to claim 1, comprising the steps of: provide a fuel additive composition according to claim 12; adding this fuel additive composition to the substantially lead-free aviation base fuel composition, the resulting fuel composition having an octane number of at least about 98 as determined by the ASTM D 2700 test method. 15. The method for increasing the octane rating of substantially lead-free aviation fuel as recited in claim 14, wherein the resulting fuel composition has an octane rating of at least about 100 as determined by the ASTM D 2700 test method.

Images