KR20090086149A - Fuel additive - Google Patents

Abstract

A fuel additive which contains ferrocene and/or a ferrocene derivative and lecithin. A solid fuel additive which contains from 80 to 99% by mass of ferrocene and/or a ferrocene derivative and from 1 to 20% by mass of lecithin. A granular fuel additive which contains from 78 to 99% by mass of ferrocene and/or a ferrocene derivative, from 0.9 to 20% by mass of lecithin and from 0.1 to 2% by mass of water. A liquid fuel additive which contains a mineral oil containing ferrocene and/or a ferrocene derivative and lecithin dissolved therein, wherein the content of ferrocene and/or a ferrocene derivative is from 2 to 5% by mass and the content of lecithin is from 5 to 50% by mass. These fuel additives are employed in such a manner as to control the concentration of ferrocene and/or a ferrocene derivative to 1 to 50 ppm and the concentration of lecithin to 0.01 to 500 ppm in the fuel. ® KIPO & WIPO 2009

Description

Fuel Additives

The present invention relates to a fuel additive including ferrocene and / or ferrocene derivatives, and more particularly, to ferrocene and / or ferrocene derivatives having enhanced action of promoting combustion, reducing soot, and reducing NOx by adding lecithin. Relates to fuel additives.

Ferrocene and its derivatives have conventionally been used as additives for various liquid fuels. For example, Japanese Patent Laid-Open No. 2-132188 discloses a fuel additive composition comprising an aromatic solvent, an aliphatic solvent, and / or a petroleum solvent, which is a ferrocene and its derivatives and a liquid organic carrier dissolving it. An improved combustion method of liquid hydrocarbons is disclosed. In addition, U.S. Patent No. 4389220 discloses a method of conditioning a diesel engine, in which 20 to 30 ppm of ferrocene is added to the fuel to remove carbon-containing deposits in the combustion chamber, and the fuel consumption per mile is reduced by about 5%. .

In addition, Japanese Patent No. 3599337 describes additives for fuel oils for internal combustion engines consisting of heavy residual oils, in which ferrocene and its derivatives are added directly to the fuel without the addition of other additives, thereby containing carbon in the engine and its accessories. A method of reducing deposits is proposed.

However, the ferrocene and ferrocene derivatives used in the present invention have a problem in that the solubility in an aromatic solvent, an aliphatic solvent and a petroleum solvent is very low.

Prosene is generally in the solid state and in particular dissolving the solid prosene also depends on the size of the solid, but in particular requires agitation power and time. Although the solid ferrocene does not dissolve easily when the addition amount is small, the solid ferrocene does not dissolve before adding it to the fuel, which causes problems in the internal combustion engine, and in the present situation, the solid ferrocene is a solvent in the dissolution tank to which the stirrer is attached. Is dissolved in and added to the fuel.

The present invention aims to solve these problems of the prior art, and an object thereof is to provide a fuel additive in which the contained ferrocene and / or ferrocene derivative can be easily and stably dissolved in fuel.

The present inventors have continually studied to achieve the above object, and thus, by combining ferrocene and / or ferrocene derivatives with lecithin, the present inventors have achieved the above object and completed the present invention.

That is, the fuel additive of the present invention is characterized in that it contains ferrocene and / or ferrocene derivatives and lecithin.

The solid fuel additive of the present invention is characterized in that it comprises 80 to 99% by weight of ferrocene and / or ferrocene derivatives, and 1 to 20% by weight of lecithin, and the particulate fuel additive of the present invention is 78 to 80% of ferrocene and / or ferrocene derivatives. It is characterized by containing 99 mass%, 0.9-20 mass% of lecithin, and 0.1-2 mass% of water.

The liquid fuel additive of the present invention comprises ferrocene and / or ferrocene derivatives and mineral oil for dissolving lecithin, the content of the ferrocene and / or ferrocene derivative is 2 to 5% by mass, and the content of the lecithin is 5 To 50 mass%.

In addition, the fuel additive of the present invention is characterized in that it is used so that the concentration of ferrocene and / or ferrocene derivative in the fuel is 1 to 50 ppm, the concentration of lecithin is 0.01 to 500 ppm.

Hereinafter, the fuel additive of this invention is demonstrated in detail. In this specification, "%" means "mass percentage" unless otherwise specified.

As mentioned above, the fuel additive of the present invention is a fuel additive comprising ferrocene and / or ferrocene derivatives and lecithin. Such fuel additives may be in the form of a solid, in particular particulate and liquid form.

(1) Ferrocene and Ferrocene Derivatives

 Ferrocene is generally referred to as bis (cyclopentadienyl) iron and is also referred to as dicyclopentadienyl iron. The ferrocene derivative used in the present invention is a compound having a substituent such as an alkyl group in the dicyclopentadienyl ring, for example, ethyl ferrocene, butyl ferrocene, acetyl ferrocene, 2,2-bis-ethyl ferrocenyl propane, etc. have.

Ferrocene and its derivatives (hereinafter referred to as "ferrocenes"), for example, US Patent No. 2650756, US Patent No. 2769828, US Patent No. 2834796, US Patent No. 2898360, US Patent No. 3095968, US Patent No. 3238158, US Patent No. 3437634, and the like.

In the present invention, the ferrocenes may be solids such as fine powder, fine particles, pellets, or the like. It is possible to select suitably according to the form of the fuel additive of this invention. This will be described later.

By including ferrocenes, the fuel additive of the present invention can have a combustion promoting effect, a smoke reduction effect, a NOx reduction effect, and the like. In particular, in diesel engines in internal combustion engines, in this combustion promoting effect, the cleaning effect of controlling the formation of valves, piston rings, and deposits in the combustion chamber can be seen. Since such deposits lower the engine's output and also increase the wear of the attached product, controlling the formation of the deposits allows for stable operation of the diesel engine. In addition, it is possible to reduce the fuel consumption by several percent by controlling excess air during combustion by combustion reforming such as combustion promotion, smoke reduction, NOx reduction, and the like.

(2) lecithin

 Lecithin is an animal and vegetable phospholipid based on glycerophospholipids and spinophospholipids. Various vegetable oils, for example, soybean oil, rapeseed oil, rice bran oil, palm oil, sunflower oil, coconut oil, cottonseed oil, corn oil, peanut oil, flaxseed oil, safflower oil, olive oil and the like can be obtained. Usually contains from 1 to 50% vegetable oil, depending on the content of such vegetable oil and the proportion of saturated and unsaturated acids in the vegetable oil, lecithin is present in liquid or solid at room temperature. In recent years, powder lecithin has been produced from liquid lecithin by oil extraction and vacuum drying.

In the present invention, the lecithin may be a liquid or may be a solid such as a fine powder. It is possible to select suitably according to the form of the fuel additive of this invention. This will be described later.

(3) form of fuel additive

 The fuel additive of the present invention may be in the form of solids, particles and liquids.

(Iii) solid fuel additives

The solid fuel additive of the present invention preferably contains 80 to 99% ferrocenes and 1 to 20% lecithin. If the lecithin is less than 1%, it is difficult to dissolve the ferrocenes in the fuel, but if it contains 20% lecithin can be sufficiently improved solubility of the ferrocenes.

The ferrocenes are not particularly limited as long as they have a solid form at room temperature, and may be produced, for example, in the form of fine powder, granulated particles, pellets and the like. Lecithin is preferably in the form of a powder at room temperature. Moreover, it is preferable that it is a form of microparticles whose particle diameter is 1 mm or less. It is because mixing with ferrocene can be manufactured more uniformly.

(Ii) particulate fuel additives

Particle fuel additive of the present invention is one form of the solid fuel additive, to prepare a fine powdered ferrocene compound as a granulator. The particle diameter is preferably 0.5 mm to 15 mm, more preferably 1 mm to 10 mm. If the particle size is less than 0.5 mm, the workability may be poor due to the scattering phenomenon, and if it exceeds 15 mm, the peptizing property may decrease and solubility may decrease.

It is preferable to contain 78 to 99% of ferrocenes, 0.9 to 20% of lecithin and 0.1 to 2% of water. If the lecithin is less than 0.9%, the ferrocenes are difficult to dissolve in the fuel, and if the lecithin is contained 20%, the effect of sufficiently improving the solubility of the ferrocenes can be obtained.

The ferrocenes are preferably in the form of powder at room temperature, and more preferably in the form of fine powder having a particle size of 2 mm or less. The lecithin is also preferably in the form of a powder at room temperature, and more preferably in the form of a fine powder having a particle size of 1 mm or less. This is for convenience of the granulation process.

The powder lecithin used in the present invention has high hygroscopicity and obtains a stickiness suitable for granulation by mixing a small amount of water. However, if the water content is less than 0.1%, sufficient adhesion may not be obtained, and the water content exceeds 2%. In this case, there is a fear that the powdered ferrocenes and the powdered lecithin described above are bulked.

(Iii) liquid fuel additives

The liquid fuel additive of the present invention comprises a ferrocene and / or ferrocene derivative and a mineral oil in which lecithin is dissolved, wherein the content of the ferrocene and / or ferrocene derivative is 2 to 5% and the content of the lecithin is 5 to 50%. Do. Less than 5% of the lecithin is because ferrocenes are difficult to dissolve in the mineral oil, and if 50% of the lecithin is contained, the effect of improving the solubility of the ferrocenes in the mineral oil can be obtained sufficiently.

The ferrocenes may be solids such as fine powders, granules, pellets, and the like, and may be liquids, but are preferably liquids or fine powders from the viewpoint of a shape that is easily soluble in mineral oil. The lecithin can also be a liquid in the same manner, and may be a solid such as a fine powder, but is preferably a liquid or a fine powder having a shape easily soluble in mineral oil.

Mineral oil used in the present invention includes hydrocarbon-based heavy oil, light oil, kerosene and the like. For example, A heavy oil, B heavy oil, light oil, kerosene and the like can be preferably used for C heavy oil used as fuel for a large diesel engine for ships, and A heavy oil can be preferably used.

(4) action and effect of lecithin

Lecithin according to the present invention mainly provides the following actions.

Iii) improvement of solubility and solubility of ferrocenes in fuel.

Ii) dispersion of sludge in fuel oil.

Iii) binder action during granulation in particulate fuel additives.

Iii) peptizing action in particulate fuel additives.

Iii) Improvement of solubility of ferrocenes in mineral oil in liquid fuel additives.

Hereinafter, each of the above operations will be described.

(Iv) improvement of solubility and solubility of ferrocenes in fuels;

As described above, ferrocenes have a problem in that they are low in solubility and solubility in various fuels. "Fuel" herein refers to A heavy oil used as fuel oil for diesel engines, oil combustion furnaces and boiler devices, light oils such as kerosene and light oil, heavy oils, heavy residue oil, lubricating oils, waste oils and mixtures thereof, or emulsion fuels thereof, Moreover, although solid fuels, such as coal, are included, it is not restrict | limited to this, as long as shape is fuel other than gaseous phase.

For example, when using ferrocene alone, the solubility in petroleum solvents such as aromatic solvents and aliphatic solvents other than benzene, toluene and xylene is very low, and only dissolves up to a concentration of up to 3% at 20 ° C. In addition, the ferrocene concentration of the long-term stable solution is preferably 2.5% or less. The same applies to dissolving ferrocene in fuel such as heavy oil. However, it is possible to dissolve the ferrocene to a concentration of 5% by adding a predetermined amount of lecithin, and the stability of the solution is good in a wide range of temperatures.

Table 1 shows the relationship between the maximum solubility of ferrocene in A heavy oil and the amount of lecithin added.

The addition of lecithin, which has a dissolution promoting effect, provides a stable solution in which ferrocenes are easily dissolved in fuels or fuel additives of various combustion equipments, and it is possible to spray ferrocenes into uniform particles in a combustion engine. It was. As a result, it was possible to sufficiently exhibit the effect of ferrocenes.

In addition, lecithin has a lipophilic moiety and a hydrophilic moiety, and is known to act as a surfactant, but the present invention also considered that solubility and the like were improved by the action of the lipophilic moiety of lecithin. That is, when dissolving ferrocenes and lecithin in fuel, a part of the lipophilic portion of lecithin is quickly absorbed by the surface of the ferrocenes, and the other lipophilic portion strengthens the lipophilic on the surface of the ferrocenes. Influences on the improvement of solubility and solubility in fuel oil were also considered.

This action is not seen in lipophilic strong nonionic surfactants or other surfactants, but is inherent in lecithin.

Ii) dispersion of sludge in fuel oil

This action is different from the above-described dissolution promoting action of ferrocenes, and lecithin itself acts as a fuel additive and affects the long-term stable operation of a combustion facility including a diesel engine.

Sludge is particularly an insoluble matter present in heavy fuel oil, and is easily precipitated, which causes a problem of blockage of the filter and poor combustion. Its occurrence is caused by heat treatment, catalytic cracking, pyrolysis, etc. in the refining process of crude oil, which is caused by the oxidation, polymerization and condensation of hydrocarbons remaining in the residual oil into hydrocarbons of low hydrogen.

The aforementioned changes occur in the order of hydrocarbons, maltenes, asphaltenes, carbines, carbodies and carbons, and these polymers are first present in heavy oil as colloids of macromolecules. It is thought that the colloid is surrounded by a hydrocarbon having a very high C / H ratio such as carbine or carbide, surrounded by several asphaltenes around it, and the surroundings are sequentially covered with a high molecular hydrocarbon having a low C / H ratio. .

Asphalt material present in the heavy oil as such colloidal particles, if dispersed in a stable colloid is present in a suspended state, it will not cause problems such as blockage of the precipitated filter, poor combustion. However, these colloidal particles are polar and adsorbable. Therefore, when the equilibrium state such as heating, mixing different kinds of oils, and the like is collapsed for a long time, the colloidal particles are combined in order, and a large particle aggregate (micelle colloid) and precipitated sludge are formed.

Specifically, when a hard powder is added to the heavy oil containing the colloidal particles, the polymer hydrocarbons and maltenes of the colloidal surface portion are dissolved, but the asphaltenes and the carbodies are unsaturated, and include the polar asphaltene particles bonded to each other because they contain polarity. Precipitates and sludge forms. In addition, when heat is applied, the colloidal surface layer portion is dissolved, and the viscosity decreases due to the temperature rise, so that the particle motion increases and the chance of collision of asphaltenes increases, so that sludge is formed by bonding and association.

Lecithin is submerged and absorbed in the bonds or associations of sludge such as carbon and asphaltenes, and acts as a surfactant to subdivide the sludge with its dispersing force. It also includes the effect of preventing the precipitation of sludge by preventing the bonding of colloidal particles by mixing or heating different fuels by this action.

Iii) binder behavior during granulation in particulate fuel additives

In the case of granulating the particulate fuel additive as described above, the lecithin is mixed with a small amount of water, has a moderate adhesiveness for granulation, and serves as a binder.

Iii) peptizing action in particulate fuel additives

The lecithin contained in the particulate fuel additive has a peptizing effect that the particles tend to break when the additive is added to the fuel. In addition, the broken down additive is very easily dissolved by the solubility enhancing effect of lecithin.

Iii) improved solubility of ferrocenes in mineral oil in liquid fuel additives

Ferrocenes have very low solubility in mineral oils and only dissolve up to a concentration of about 2.5%. However, by adding a predetermined amount of lecithin, it is possible to dissolve ferrocene up to a concentration of 5%, and the stability of the concentration is good in a wide range of concentrations.

(5) Concentrations of Ferrocenes and Lecithin in Fuels

The fuel additive of the present invention is used so that the concentration of ferrocenes is in the range of 1 to 50 ppm and the lecithin is in the range of 0.01 to 500 ppm in various fuels used in diesel engines, oil combustion furnaces, boiler devices, and the like used in ships and power generation facilities. It is preferable to add and use.

More preferably, in the concentration of ferrocenes, it is preferable to use the connection injection so that the oil combustion furnace and the boiler apparatus is in the range of 1 to 10 ppm, and the diesel engine is in the range of 10 to 50 ppm.

However, in order to greatly improve the combustion promotion, the smoke reduction, the NOx reduction, and the like, depending on the state of the combustion engine, it is possible to temporarily inject several times to several tens of such continuous injection amounts for a short time.

The concentration of lecithin is advantageous for dissolving ferrocene easily and stably with respect to fuel oil and fuel additive itself, and also for dispersing sludge, especially in heavy fuel oil.

In this way, it is preferable to dissolve the ferrocenes easily and stably at the desired concentration of lecithin, and to sufficiently exert the effect of the ferrocenes, it is possible to influence the long-term stable operation of the combustion equipment.

Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to the following Example.

Evaluation of various properties was performed in the following manner.

[Evaluation by Solubility Test of Ferrocene]

Solid Fuel Additives (Examples 1-4 and Comparative Example 1)

Ferrocene is added while stirring at 200 ° C at 20 ° C and 60 rpm for 200 g of heavy oil A as fuel oil (sulfur content = 0.99%, viscosity = 2.8cst (50 ° C)), and the dissolution rate is measured in seconds until the ferrocene concentration reaches 3%. Thereafter, ferrocene was added to prepare a stable solution at the maximum concentration, which was left at room temperature for 1 week to measure the stability of the state.

Liquid Fuel Additives (Examples 5-7 and Comparative Example 2)

While stirring at 20 ° C. and 60 rpm, the dissolution rate was measured in seconds until the ferrocene was completely dissolved in A heavy oil with respect to the fuel additive prepared by the formulation of Table 2. After leaving the obtained solution for 1 week at room temperature, the stability of the state was measured. The test was performed on a 200 g scale. The results are shown in Table 3.

result

The solid fuel additives of the present invention (Examples 1-4) showed very fast dissolution rates until the ferrocene concentration reached 3% when compared to Comparative Example 1. In addition, in the concentration of the determined solution, Comparative Example 1 was in a state where many insoluble matters existed at 3%, whereas Examples 1 to 4 were capable of a concentration of 3.5 to 5.0%. In addition, the stability evaluation after 1 week of Examples 1-4 was a result of (circle)-(◎). As described above, the solid fuel additive of the present invention was found to be very excellent in terms of dissolution rate, dissolution concentration, and stability evaluation of ferrocene.

[Sludge Dispersion Effect]

Sludge dispersion tests were performed using the examples and comparative examples described in Tables 2 and 3.

The test was conducted in accordance with the Japanese Ship Owners Association Act.

Operation sequence

(1) 0.1 g of C heavy oil was taken from a test tube, and 20 ml of normal butane was added thereto. To this was added 0.02 ml (1 / 1,000) of the fuel additives of Examples 1-7 and Comparative Examples 1-2.

(2) The test tube was sealed and shaken vigorously more than 20 times until complete mixing.

(3) This was left to stand at room temperature, and the dispersion state per elapsed time of each minute was determined by the following criteria.

Criteria

A… Completely dispersed and free from precipitation.

B… Disperse but with precipitate.

Called B1, B2, B3 in order of increasing precipitation.

C… Not dispersed (and also precipitated).

The test results are shown in Table 4.

result

The solid fuel additives of the present invention (Examples 1 to 4) and the liquid fuel additives of the present invention (Examples 5 to 7) showed a very good sludge dispersion effect compared to Comparative Examples 1, 2 and no addition. In Comparative Examples 1 and 2 containing no lecithin, there was no effect, which was the same as no additive C heavy oil. The effect of lecithin has been shown to be generally proportional to the additive.

[Measurement of combustion speed]

10 mg of fuel oil (the same as that used for the evaluation of the sludge dispersion effect) of the fuel oil to which the liquid fuel additive (Examples 5 to 7) of the present invention and the liquid fuel additive of Comparative Example 2 were added were subjected to differential thermal analysis system TG / Residual carbon produced by heating using DTA 6300 (manufactured by Seiko Instruments Co., Ltd.) at a heating rate of 100 ° C./min to 500 ° C. (mass at the end point of residual carbon production is called “m 1”) and held at 500 ° C. The TG (thermogravimetric analysis) residual carbon burning rate constant was calculated from the mass reduction curve of 95% of the point of combustion, called 'm2'. The air volume was 100 ml / min. The calculation method used the following formula (I). ※ 1, ※ 2

TG residual carbon burning rate constant = A x T x In (m1 / m2) / τ. (Ⅰ)

A: integer

T: temperature

m1: mass at the end point of residual carbon formation

m2: mass at 95% burning point

τ: (m2-m1) time

* 1 Shibayama et al., Japanese Society of Mechanical Engineers, 34 (260), 769 (1968)

※ 2 Heavy Rain et al., Japanese Society of Mechanical Engineers, 54 (507), 3301 (1988)

The test results are shown in Table 5.

result

The addition of 1000 ppm of the liquid fuel additive (Examples 5 to 7) of the present invention yielded a high TG residual carbon fuel rate constant (relative rate constant) as compared to the 1000 ppm addition of Comparative Example 2. Although this is a natural result of having a high content of ferrocene, the TG residual carbon combustion rate constant (relative rate constant) was also obtained even with the addition of 500 ppm of Examples 5 to 7 than the 1000 ppm addition of Comparative Example 2. Further, the 1000 ppm addition of Examples 5 to 7 yielded a higher TG residual carbon combustion rate constant (relative rate constant) than the 2000 ppm addition of Comparative Example 2.

This can be presumed to be the synergistic effect of the solubility of lecithin into ferrocene and the sludge dispersion effect. In Comparative Example 2, which does not contain lecithin, it is determined that ferrocene is unstable in the liquid additive and that dissolution is insufficient even in fuel oil. Moreover, since it is not a sludge dispersing effect, when the relative content of ferrocene is the same, it is judged that an effect is bad compared with Examples 5-7.

[System test by diesel engine]

The system test of the cargo ship of the following specification containing a diesel engine was performed using the solid fuel additive of this invention (Example 3) and the solid fuel additive of Comparative Example 1. The system test was performed by dissolving 9.0 kg of solid fuel additive in 360 liters of A heavy oil in a dissolution tank with agitator, and then adding 1/1000 to the fuel (C heavy oil) line from the dissolution tank with an injection pump ( The amount of fuel additive added was 25 ppm.).

In the solid fuel additives of Example 3 and Comparative Example 1, the addition was carried out in the above manner over four months alternately per month (30 days) (for one solid fuel additive, one month x two times). , The fuel consumption and the dust condition of the heat exchanger were visually observed and compared. Water washing was then performed to compare dust removal.

Specification of Cargo Ship

Total tonnage: 160,000 tons

Tonnage of Goods Weight: 300,500 Tons

Maximum continuous power: 21,300KW × 74rpm

Number of cylinders: 10

Speed of Turbocharger: 10,000rpm

Fuel Consumption: 90,000L / day (without addition)

Test effects are shown in Table 6.

In actual ship testing, fuel consumption is affected by wind, tidal flow, and power differences, but the assessment can be considered reliable because two tests for each item yield the same results. .

The solid fuel additive (Example 3) of the present invention showed that although the addition amount of ferrocene itself was much smaller than that of Comparative Example 1, the fuel consumption was also low. This is because the lecithin improves the solubility and solubility of ferrocene, and finely stable fuel spray is realized by the sludge dispersion effect of the lecithin itself, and the combustion effect is integrated and synergistically improved. In addition, since the combustion promoting action was improved, it was observed that the dust of the heat exchanger was also cleaner, compared to Comparative Example 1, and simply washed with water to remove it.

At the same time, when dissolving the fuel additive of Example 3 in the dissolution tank, it was quickly disintegrated and dispersed after the dissolution, completely dissolved after about 10 minutes, and it was confirmed that no precipitates or suspended solids were observed in the dissolution tank during the test. . On the other hand, in the fuel additive of Comparative Example 1, some suspended matter was observed after about 30 minutes of stirring, and even during the test, precipitation and suspension of ferrocene insoluble content were observed in the dissolution tank.

According to the present invention, it is possible to provide a fuel additive in which the ferrocene and / or ferrocene derivatives included by combining ferrocene and / or ferrocene derivatives with lecithin can be easily and stably dissolved in the fuel.

Claims (5)

A fuel additive comprising ferrocene and / or ferrocene derivatives and lecithin. The fuel additive of claim 1, wherein the ferrocene and / or ferrocene derivative is 80 to 99% by mass, and the lecithin is 1 to 20% by mass, and is in a solid phase. The fuel additive of claim 1, wherein the ferrocene and / or ferrocene derivative is 78 to 99% by mass, the lecithin is 0.9 to 20% by mass, and the moisture is 0.1 to 2% by mass. In the fuel additive containing the ferrocene and / or ferrocene derivative and the mineral oil dissolved in the lecithin, The fuel additive of claim 1, wherein the content of the ferrocene and / or the ferrocene derivative is 2 to 5% by mass, the content of the lecithin is 5 to 50% by mass, and a liquid phase. The method according to any one of claims 1 to 4, wherein the ferrocene and / or ferrocene derivatives in the fuel are added in an amount of 1 to 50 ppm and the lecithin is 0.01 to 500 ppm. Fuel additives.