JP5427361B2 - Antioxidant for fuel, fuel composition containing the antioxidant, and method for producing fuel composition - Google Patents

Description

The present invention relates to fuel compositions containing the fuel for antioxidant and the antioxidant, especially low sulfur fuel antioxidants, low sulfur as a fuel for an internal combustion engine such as a diesel engine containing antioxidant The present invention relates to a fuel composition and a method for producing the fuel composition .

  Petroleum products such as light oil, gasoline, kerosene, and heavy oil are used as fuel for diesel engines and gasoline engines, fuel for heating, and the like. When these petroleum products are oxidized, discoloration, formation of precipitateable polymer (sludge), increase in viscosity, etc. are observed, and peroxides (peroxide) generated by oxidation deteriorate the members of the fuel system (rubber, etc.). It is known to let Therefore, oxidation stability is one of the important indexes for evaluating the quality stability of petroleum products, and it is desirable to have high oxidation stability.

  In addition, so-called sulfur-free fuel oil, which has almost no sulfur content to prevent poisoning of the exhaust gas purification catalyst, has been put on the market since January 2005. Moreover, the sulfur content of gasoline and light oil is required to be further reduced to less than 10 mass ppm against the background of fuel consumption regulations, reduction of carbon dioxide emissions, and reduction of toxic substances in exhaust gas.

  In order to remove the sulfur content, hydrodesulfurization treatment is generally performed in which hydrogen is blown into a high-temperature and high-pressure fuel oil and brought into contact with a solid catalyst, and the sulfur content is removed as hydrogen sulfide by a hydrocracking reaction. However, when subjected to a heat load at a high temperature in the process of highly removing sulfur, unstable substances are likely to be generated in the fuel, and oxidation stability may deteriorate. Also, antioxidants such as amines and phenols originally contained in the fuel are removed. Furthermore, there is also an aspect that the sulfur content of the organic sulfur compound itself has an effect of suppressing the oxidation of the fuel, and the reduction of the sulfur content itself is a factor that directly decreases the oxidation stability of the fuel.

  Thus, many attempts have been made so far to obtain a fuel oil excellent in oxidation stability while reducing the sulfur content. Among them, paying attention to a specific aromatic component contained in the fuel composition, the ratio of naphthalenes having good oxidation stability to naphthenebenzenes, fluorenes or bicyclic naphthenes having poor oxidation stability is determined. There are those that are intended to improve the oxidation stability of the fuel composition by increasing the value.

JP-A-2006-137919 (Patent Document 1) discloses that the sulfur content is 50 ppm by mass or less, the sum of the contents of naphthenebenzenes and fluorenes is 8.0% by volume or less, and naphthalene. The content of benzene is 0.5 volume% or more and 3.0 volume% or less, the oxidation stability index Y represented by the following formula (I) is 3 or less, and the ratio of the content of fluorenes and naphthalenes A gas oil composition characterized in that is 1 or less is described.
Y = 2.9 × [fluorene content (volume%)] + 0.016 × [naphthenebenzene content (volume%)] − 0.73 × [naphthalene content (volume%)] Formula (1)

Japanese Patent Application Laid-Open No. 2006-233087 (Patent Document 2) has an aromatic content of 25% by volume or less, of which a 2-ring aromatic content is 2.5% by volume or less, a tricyclic or higher aromatic content. A kerosene composition having a content of 0.5% by volume or less and an oxidation stability index Y represented by the following formula (I) of 10 or less is described.
Y = 1.63 × [naphthenebenzene content (volume%)] + 0.30 × [bicyclic naphthene content (volume%)] − 0.57 × [naphthalene content (volume%)] Formula (1)

JP 2006-137919 A JP 2006-233087 A

  As in the prior art, a method for controlling the composition of the aromatic component contained in the fuel composition in anticipation of the oxidation stability effect of naphthalenes is effective, but in the case of adjusting the fuel composition itself, the fuel Therefore, the oxidation stability of a fuel composition having poor oxidation stability cannot be improved, and the form of a fuel additive is more convenient.

  Conventionally, the influence on oxidation stability as a common property of certain compound groups such as naphthalenes and naphthenebenzenes has only been discussed, and the contribution of individual compounds has not been studied in detail. In general, aromatic components often have poor ignitability, and since the combustibility deteriorates, the production of particulate matter may increase, so even if it is an aromatic component that improves oxidation stability, diesel In consideration of application to fuel, it is preferable that the content is small.

Accordingly, the present invention has an object to provide an aromatic compound having a particularly high effect of improving oxidation stability for a fuel while paying attention to an aromatic component, and further provides a fuel composition containing the aromatic compound. It is another object of the present invention to provide a method for producing a fuel composition .

  As a result of diligent research, the present inventor has found that the number and type of side chains in addition to the number of aromatic rings are greatly involved in antioxidant ability, and aromatic compounds having a specific molecular structure have particularly high antioxidant ability. I found out.

  According to the research result of the present inventor, the effect of improving the oxidative stability is greatly seen in a compound in which aromatic rings are condensed with each other, and it is hardly seen when the compound is not condensed (for example, biphenyl). Even in the case of naphthalenes, there is a significant difference in the improvement effect depending on the molecular structure. A tricyclic aromatic compound such as anthracene tends to exhibit higher oxidative stability than a bicyclic aromatic compound such as naphthalene. And among anthracene, anthracene is the most effective. However, dialkylnaphthalene typified by dimethylnaphthalene exhibits a remarkable effect of improving oxidative stability among naphthalenes, and the effect is comparable to anthracene.

  The present invention completed on the basis of the above can be specified as follows.

The present invention in one aspect, a fuel antioxidants containing anthracene and one or more polycyclic aromatic selected from the group consisting of di-methylation naphthalene compound.

  In one embodiment of the antioxidant for fuel according to the present invention, the anthracene includes anthracene and alkyl-substituted anthracene.

  Another aspect of the present invention includes a hydrocarbon fraction having 80% by volume or more of chain paraffin and the above antioxidant for fuel, and 0.05% by mass or more in total of the polycyclic aromatic compound. It is a fuel composition to contain.

  In one embodiment, the fuel composition according to the present invention has a total content of polycyclic aromatic compounds other than the polycyclic aromatic compound of 1% by volume or less.

  In another embodiment of the fuel composition according to the present invention, in an oxidation stability test of ISO12205, a sample temperature is 115 ° C., oxygen is supplied in 300 mL of a sample at a supply amount of 3 L / h, and a supply pressure of 98 kPa. The difference between the total acid value after oxidizing the sample by supplying for a time and the total acid value before oxidation is 0.5 mgKOH / g or less.

  In another aspect of the present invention, there is provided a method for producing a fuel composition, comprising blending the above-mentioned antioxidant for fuel with a hydrocarbon fraction containing 80% by volume or more of chain paraffin. This is a method of blending so that the total of the polycyclic aromatic compounds is 0.05% by mass or more with respect to the mass of the product.

  Anthracene and dialkylnaphthalene are particularly effective in improving oxidative stability among aromatic compounds, and can achieve desired oxidative stability with a small amount of addition. Therefore, it is possible to obtain an excellent antioxidant effect while minimizing deterioration in combustibility and volatility due to the aromatic component contained in the fuel oil.

(Antioxidant)
In one embodiment, the antioxidant for fuel according to the present invention contains one or more polycyclic aromatic compounds selected from the group consisting of anthracenes and dialkylnaphthalenes.

In the present invention, anthracene refers to a hydrocarbon having an anthracene nucleus,
For example, in addition to anthracene, alkyl-substituted anthracene can be mentioned. Alkyl substituted anthracene is an anthracene substituted with one or more alkyl groups. The number of substituents is not particularly limited, but is typically 1 to 4, more typically 1 to 2. The type of the alkyl group is not particularly limited, but typically includes a linear or branched alkyl group having 1 to 8 carbon atoms, specifically, methyl, ethyl, propyl, Examples include isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, hexyl and octyl groups.

  More typically, methyl substituted anthracene is used as the alkyl substituted anthracene. Methyl-substituted anthracene includes, but is not limited to, methylanthracene such as 1-methylanthracene, 2-methylanthracene, 9-methylanthracene; 2,3-dimethylanthracene, 9,10-dimethylanthracene, 1,5- And dimethylanthracene such as dimethylanthracene; and trimethylanthracene such as 1,4,9-trimethylanthracene and 2,7,9-trimethylanthracene.

  Of the anthracenes, anthracene is particularly preferable. Anthracene has a particularly excellent oxidation stability improving effect.

Anthracene can be produced by any known production method. For example, anthracene can be obtained by separating and refining anthracene oil taken from coal tar. The alkyl-substituted anthracene can be obtained by a Friedel-Crafts reaction in which alkylation is performed by a liquid crystal reaction using anhydrous aluminum chloride, boron trifluoride, iron oxide or the like as a catalyst, or a gas phase reaction using a solid silica / alumina catalyst.
Anthracenes are commercially available and may be used.

  Although dialkylnaphthalene is a kind of naphthalene, it has an effect of improving oxidative stability comparable to anthracene. The arrangement of the two alkyl groups is not particularly limited. The type of the alkyl group is not particularly limited, but typically includes a linear or branched alkyl group having 1 to 8 carbon atoms, specifically, methyl, ethyl, propyl, Examples include isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, hexyl and octyl groups. As the alkyl group, a methyl group is preferable, and as such dimethylnaphthalene, 1,2-dimethylnaphthalene, 1,3-dimethylnaphthalene, 1,6-dimethylnaphthalene, 1,4-dimethylnaphthalene, 1,5- Examples include dimethylnaphthalene, 1,7-dimethylnaphthalene, 1,8-dimethylnaphthalene, 2,3-dimethylnaphthalene, 2,6-dimethylnaphthalene, and 2,7-dimethylnaphthalene. These may be used alone or in combination. can do. Typically, dimethylnaphthalene is provided as a mixture of these.

  The mixture of dimethylnaphthalene is a liquid, but anthracenes are solid at room temperature. Therefore, when anthracenes are used, they may be dissolved in a solvent such as toluene or xylene before being added to the fuel composition. As the solvent, not only a single compound such as toluene or xylene, but also a mixture of a plurality of compounds such as petroleum fraction obtained in the petroleum refining process can be used.

  Anthracene and dimethylnaphthalene contained in the fuel composition can be quantitatively analyzed by a method such as gas chromatography or gas chromatography-mass spectrometry.

  Moreover, the antioxidant for fuels according to the present invention may use the polycyclic aromatic compound alone or use a petroleum base material obtained in a petroleum refining process containing the polycyclic aromatic compound. You can also. The antioxidant for fuel preferably contains the above-mentioned polycyclic aromatic compounds in a total amount of 1% by weight or more, particularly 5% by weight or more, and more preferably 20% by weight or more.

(Fuel composition)
The oxidation stability of the fuel composition can be improved by adding the above-described polycyclic aromatic compound according to the present invention to a fuel composition such as gasoline, light oil, kerosene, or heavy oil. The addition amount may be small, and if the total polycyclic aromatic compound is added in an amount of about 0.05% by mass with respect to the total weight of the fuel composition, a sufficient oxidation stability improving effect can be obtained.

As the amount of the polycyclic aromatic compound contained in the fuel composition increases, the oxidation stability improvement effect also increases, but the improvement effect eventually saturates, and addition of a large amount results in soot formation during combustion, ignitability reduction, It leads to deterioration of volatility.
Therefore, the fuel composition according to the present invention preferably contains 0.05 to 5.0% by mass of the polycyclic aromatic compound, and contains 0.1 to 3.0% by mass in total. It is more preferable that the total content is 0.2 to 2.0% by mass.

  Some aromatic compounds have the effect of improving the oxidative stability of the fuel composition in addition to the polycyclic aromatic compound according to the present invention described above. However, since the solubility in fuel oil decreases as the number of rings increases, such as four rings and five rings, problems such as easy precipitation at low temperatures occur, resulting in poor practicality. For this reason, it is preferable that content of polycyclic aromatic compounds other than the said polycyclic aromatic compound is 5 volume% or less in total, and especially 3 volume% or less.

An increase in aromatic compounds, particularly polycyclic aromatics, in the fuel composition leads to deterioration in ignitability and volatility, and is not suitable for application to diesel fuel.
Therefore, aromatic compounds other than the polycyclic aromatic compound according to the present invention are excluded from the fuel composition as much as possible, and most of the aromatic compounds contained in the fuel composition are the polycyclic aromatic compound according to the present invention. By occupying the fuel composition, the fuel composition is in a state of containing only a minimum amount of an aromatic compound necessary for exhibiting a desired oxidation stability improving effect. As a result, the content of the entire aromatic compound can be suppressed, and deterioration of the ignitability and volatility of the fuel composition can be minimized.

Therefore, in one embodiment of the fuel composition according to the present invention, the total content of polycyclic aromatic compounds other than the polycyclic aromatic compound according to the present invention is 1% by volume or less, preferably 0.1 volume. % Or less, more preferably 0.01% by volume or less, and most preferably 0.001% by volume or less. In the present invention, the polycyclic aromatic compound refers to a polycyclic aromatic compound analyzed according to a high performance liquid chromatography method (JPI-5S-49-97) defined by the Petroleum Institute of Japan.
Examples of the polycyclic aromatic compound thus detected include pentalene, tetralin, naphthalene, indene, fluorene, anthracene, phenanthone, pyrene, and derivatives thereof.

In another embodiment of the fuel composition according to the present invention, the total content of monocyclic aromatic compounds is 15% by volume or less, preferably 10% by volume or less, more preferably 1% by volume. Or less, still more preferably 0.1% by volume or less, and most preferably 0.01% by volume or less. In the present invention, the monocyclic aromatic compound refers to a monocyclic aromatic compound analyzed according to a high performance liquid chromatography method (JPI-5S-49-97) defined by the Petroleum Institute of Japan.
As a monocyclic aromatic compound detected by this, benzene, toluene, xylene, and cumene are mentioned, for example.

Preparation of such a fuel composition substantially free of an aromatic compound other than the polycyclic aromatic compound according to the present invention is performed by, for example, FT (Fischer-Tropsch) synthesis from energy resources such as natural gas, coal, and biomass. Can be carried out by adding the polycyclic aromatic compound according to the present invention to a GTL fuel containing almost no aromatic component.
Moreover, it can also prepare by the method of carrying out the nuclear hydrogenation using the catalyst containing nickel, platinum, etc. for the aromatic component contained in a petroleum fraction. More typically, the polycyclic ring according to the present invention with respect to a hydrocarbon fraction in which the chain paraffin thus obtained is 80% by volume or more, preferably 90% by volume or more, more preferably 95% by volume or more. A fuel composition can be prepared by adding an aromatic compound.

In the fuel composition of the present invention, the sulfur content is preferably 10 ppm by mass or less from the viewpoint of diesel engine fuel efficiency and exhaust gas purification. The sulfur content is more preferably 5 ppm by mass or less, and particularly preferably 1 ppm by mass or less. The removal of the sulfur content may use a known desulfurization method such as hydrodesulfurization, alkali cleaning, solvent desulfurization, gasification desulfurization and the like. Moreover, when GTL fuel is used, sulfur content is essentially hardly contained.
Therefore, in one embodiment of the present invention, it is desirable to add the additive according to the present invention to a fuel composition sufficiently desulfurized until the sulfur content becomes 10 mass ppm or less.

  The fuel composition of the present invention preferably has a saturated hydrocarbon content of 80% by volume or more, and a chain paraffin (chain saturated hydrocarbon) content of 15% by volume or more. The chain paraffin is a component necessary for maintaining the cetane number, which is one of the fuel combustibility indicators, and is preferably 20% by volume or more, more preferably 25% by volume or more, and even more preferably 50% by volume. As mentioned above, it is desirable to contain 90% by volume or more most preferably. If it is less than 15% by volume, it may be difficult to maintain good ignitability during combustion.

  The fuel composition of the present invention preferably corresponds to ordinary light oil and kerosene. Specific preferred ranges are 90% distillation temperature of 250 ° C. to 350 ° C., particularly 260 ° C. to 340 ° C., 10% distillation temperature of 180 ° C. to 270 ° C., particularly 200 ° C. to 260 ° C. The cetane index is 40 to 90, particularly 50 to 80.

  In one embodiment of the fuel composition of the present invention, the difference between the total acid value after sufficient oxidation and the total acid value before oxidation is 0.5 mgKOH / g or less. The difference between the total acid values before and after oxidation is preferably 0.4 mgKOH / g or less, more preferably 0.3 mgKOH / g or less, still more preferably 0.2 mgKOH / g or less, most preferably from the viewpoint of reducing the corrosiveness of vehicle parts. It is 0.1 mgKOH / g or less. The total acid value of the fuel composition is 0.05 mgKOH / g or less, more preferably 0.03 mgKOH / g or less, and still more preferably 0.01 mgKOH / g or less. The total acid value after oxidation to 0.5 mgKOH / g or less, preferably 0.4 mgKOH / g or less, more preferably 0.3 mgKOH / g or less, still more preferably 0.2 mgKOH / g or less, particularly preferably 0. 1 mgKOH / g or less is desirable.

  The term “sufficiently oxidized” as used herein means that the test temperature is changed from 95 ° C. to 115 ° C. in an oxidation stability test of ISO12205, and oxygen is supplied into a 300 mL sample at a supply amount of 3 L / h and a supply pressure of 98 kPa. , Indicates that an oxidation test was performed for 16 hours. After the oxidation test is completed, the sample is quenched with ice in order to prevent the oxidation due to the holding time at a high temperature from proceeding.

  In addition, the fuel additive or fuel composition in the present invention contains a fatty acid ester having 5 or more carbon atoms and a higher alcohol in addition to the usual liquid hydrocarbon, as long as the object of the present invention is not impaired. You can also. In addition, fluidity improvers, lubricity improvers, pour point depressants, cetane number improvers, antioxidants, metal deactivators, detergents, corrosion inhibitors, antifreeze agents, microbial disinfectants, assistants, if desired. You may contain other fuel additives, such as a flame retardant, an antistatic agent, and a coloring agent. Although there is no restriction | limiting in particular regarding the kind and addition amount, Usually, it is preferable that it is the range of 1-3000 mass ppm from surfaces, such as a balance of an effect and economical efficiency.

The physical property measurement method and evaluation method used in the present invention are measured by the following methods.
1) Density: Measured at 15 ° C. by the method defined in JIS K2249 “Crude oil and petroleum product density test method”.
2) Distillation property: A method defined in JIS K2254 “Distillation Test Method”.
3) Kinematic viscosity: Measured at 30 ° C. by the method defined in JIS K2283 “Kinematic viscosity test method”.
4) Sulfur content: A method defined in JIS K2541-6 “Sulfur content test method (ultraviolet fluorescence method)”.
5) Nitrogen content: A method defined in JIS K2609 “Nitrogen content test method (chemiluminescence method)”.
6) Cetane index: Calculated by the method defined in JIS K2280 “Method for calculating cetane index”.
7) Aromatic content: Method specified in JPI-5S-49-97 “Petroleum products—Hydrocarbon type test method—High performance liquid chromatographic method” 8) Total acid number: JIS K2501 “Petroleum products and lubricants— The method specified in “Price Testing Method”.
9) Oxidation test: In the oxidation stability test of ISO12205, the sample temperature was changed from 95 ° C. to 115 ° C., and oxygen was supplied to 350 mL of the sample at a supply amount of 3 L / h and a supply pressure of 98 kPa for 16 hours. A method in which the sample is cooled to ice and returned to room temperature.

  The content of the present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited thereto.

(Base fuel)
As the base fuel, commercially available light oil 1 (GTL light oil manufactured by MOSSGAS) having the properties shown in Table 1 was used.

Example 1
Ten types of fuel compositions described in Table 2 were prepared by adding 0 to 0.4 mass% of anthracene or dimethylnaphthalene as an antioxidant to the base fuel. These fuel compositions were subjected to an oxidation test by the oxidation test method, and the total acid value before and after the test was measured. From the results in Table 2, it can be seen that the oxidation of the fuel was significantly suppressed by adding the antioxidant. It can also be seen that anthracene and dimethylnaphthalene have antagonistic effects. For example, the addition of 0.10% by mass of anthracene can suppress the increase in total acid value by about 90%.

Example 2
An experiment was conducted to show that the effect on the oxidative stability of the fuel differs significantly depending on the molecular structure of the aromatic compound. 0.1% by mass of each compound shown in Table 3 was added to the base fuel, and the total acid value after the oxidation test was measured. From the results in Table 3, it can be seen that anthracenes, which are tricyclic aromatic compounds, tend to have a higher oxidative stability effect of fuel than naphthalenes, which are bicyclic aromatic compounds. In anthracenes, there is no significant difference in the antioxidant effect due to the difference in side chains, but in the naphthalenes, a considerable difference is observed in the antioxidant effect.
While 2-methylnaphthalene and 1-ethylnaphthalene have almost no antioxidant effect, dimethylnaphthalene has a remarkable antioxidant effect.

Claims (6)

Anthracenes and one or more polycyclic aromatic fuel antioxidants containing compound selected from the group consisting of di-methylation naphthalene.   It contains a hydrocarbon fraction whose chain paraffin is 80% by volume or more and the antioxidant for fuel according to claim 1, and the total amount of the polycyclic aromatic compound according to claim 1 is 0.05% by mass or more. Containing fuel composition.   The fuel composition according to claim 2, wherein the total content of polycyclic aromatic compounds other than the polycyclic aromatic compound according to claim 1 is 1% by volume or less.   In the oxidation stability test of ISO12205, the sample temperature was set to 115 ° C., and the total acid number and oxidation after oxidation of the sample by supplying oxygen into 300 mL of the sample at a supply amount of 3 L / h and a supply pressure of 98 kPa for 16 hours. The fuel composition according to claim 2 or 3, wherein the difference in the previous total acid number is 0.5 mgKOH / g or less.   The fuel composition according to any one of claims 2 to 4, wherein the sulfur content is 10 mass ppm or less.   A method for producing a fuel composition comprising blending the antioxidant for fuel according to claim 1 into a hydrocarbon fraction having a chain paraffin content of 80% by volume or more, wherein the claim is based on the mass of the fuel composition. The method of mix | blending so that the sum total of the polycyclic aromatic compound of claim | item 1 may be 0.05 mass% or more.