JP5227626B2 - Fuel composition containing a fuel oil base produced by Fischer-Tropsch synthesis - Google Patents

Description

  The present invention relates to a fuel composition containing a fuel oil base produced by Fischer-Tropsch synthesis, and more particularly to a low-sulfur fuel composition used as a fuel for an internal combustion engine such as a diesel engine.

  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.

As such a sulfur-free fuel oil base material, so-called GTL fuel oil has attracted attention (see Patent Document 1). It was produced by hydrocracking and skeletal isomerization of wax obtained by Fischer-Tropsch synthesis using hydrogen and carbon monoxide generated from biomass, natural gas, steelworks, etc. It is a hydrocarbon oil and is substantially free of sulfur.
JP-T-2004-500977

  However, the hydrocarbon oil produced by Fischer-Tropsch synthesis has a problem of poor oxidation stability.

  Then, this invention makes it a subject to improve the oxidation stability of the fuel composition using the hydrocarbon oil manufactured by the Fischer-Tropsch synthesis.

  As a result of diligent research, the present inventor has found that an aromatic compound having a specific molecular structure has a particularly high antioxidant ability with respect to a hydrocarbon oil produced by Fischer-Tropsch synthesis.

  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.

  In one aspect, the present invention is a fuel composition comprising one or more polycyclic aromatic compounds selected from the group consisting of anthracenes and dialkylnaphthalenes, and a fuel oil base produced by Fischer-Tropsch synthesis.

  In one embodiment of the fuel composition according to the present invention, the total content of the polycyclic aromatic compound is 0.05% by mass or more.

  In another embodiment of the fuel composition according to the present invention, the total content of polycyclic aromatic compounds other than the above polycyclic aromatic compounds is 5% by volume or less, and the content of monocyclic aromatic compounds is The total is 15% by volume or less.

  In yet another embodiment of the fuel composition according to the present invention, in the oxidation stability test of ISO12205, the sample temperature is 115 ° C., the oxygen is supplied in 3 mL / h, and the supply pressure is 98 kPa in 300 mL of the sample. The difference between the total acid value after oxidizing the sample by supplying for 16 hours and the total acid value before oxidation is 0.5 mgKOH / g or less.

  In another embodiment of the fuel composition according to the present invention, one or more polycyclic aromatic compounds selected from the group consisting of anthracenes and dialkylnaphthalenes on a fuel oil base produced by Fischer-Tropsch synthesis Is a method for producing a fuel composition, comprising blending.

  Anthracenes and dialkylnaphthalenes are highly effective in improving oxidative stability against fuel oil bases produced by Fischer-Tropsch synthesis, and can achieve desired oxidative stability with a small amount of addition. Therefore, it becomes possible to improve the stability of fuel oil using the fuel oil base material produced by Fischer-Tropsch synthesis, and at the same time minimize the deterioration of combustibility due to the inclusion of aromatic components in the fuel oil. It is possible to obtain an excellent antioxidant effect while suppressing.

(Polycyclic aromatic compounds)
The fuel composition according to the present invention contains one or more polycyclic aromatic compounds selected from the group consisting of anthracenes acting as an antioxidant and dialkylnaphthalene.

  In the present invention, anthracene refers to a hydrocarbon having an anthracene nucleus, and examples include anthracene and alkyl-substituted anthracene. 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. Examples of methyl-substituted anthracene include, but are not limited to, 1-methylanthracene, 2-methylanthracene, methylanthracene such as 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 dialkylnaphthalene contained in the fuel composition can be quantitatively analyzed by a method such as gas chromatography or gas chromatography-mass spectrometry.

(Fuel composition)
The fuel composition according to the present invention is obtained by blending the above-mentioned polycyclic aromatic compound with a fuel oil base produced by Fischer-Tropsch synthesis. The content of the fuel oil base produced by Fischer-Tropsch synthesis is not particularly limited, but is preferably 5% by volume or more, particularly 10% by volume or more, and more preferably 50% by volume or more. By adding the above-mentioned polycyclic aromatic compound according to the present invention to a fuel oil base produced by Fischer-Tropsch synthesis, the stability of the fuel oil base can be improved. The addition amount may be a very small amount, and if it is added in a total amount of about 0.05 mass% with respect to the total weight of the fuel composition, a sufficient oxidation stability improving effect can be obtained. Therefore, in one embodiment, the fuel composition according to the present invention includes a fuel oil base produced by Fischer-Tropsch synthesis, and one or more polycyclic aromatic compounds selected from the group consisting of anthracenes and dialkylnaphthalenes Is a fuel composition containing 0.05% by mass or more in total.

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.
Accordingly, the fuel composition according to the present invention preferably contains 0.05 to 5% by mass of the polycyclic aromatic compound, more preferably 0.1 to 3% by mass in total. The total content is preferably 0.2% by mass to 2% 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.

  The fuel oil base produced by Fischer-Tropsch synthesis used in the present invention is composed of hydrocarbon compounds produced by FT (Fischer-Tropsch) synthesis from energy resources such as natural gas, coal, and biomass, and further hydrocracking, etc. It is a fuel oil base produced through processes such as decomposition and skeletal isomerization. The fuel composition of the present invention can be obtained using a fuel oil base other than such a fuel oil base, for example, a petroleum fuel base obtained by refining crude oil, or a vegetable oil such as soybean oil as a raw material. A bio-based fuel oil base material may be blended.

  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. In addition, the fuel oil base produced by Fischer-Tropsch synthesis essentially does not contain sulfur.

  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: The method specified in JPI-5S-49-97 "Petroleum products-Hydrocarbon type test method-High performance liquid chromatograph method".
8) Total acid value: A method defined in JIS K2501 “Petroleum products and lubricants—neutralization number test 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 (5)

Anthracenes and di methylation naphthalene 0.05% to 2% by weight of one or more polycyclic aromatic compounds selected in total from the group consisting of, 15% by volume single-ring aromatic compounds in total, and A fuel composition having a 10% distillation temperature of 180 ° C. to 270 ° C. and a 90% distillation temperature of 250 ° C. to 350 ° C., comprising a fuel oil base produced by Fischer-Tropsch synthesis. The fuel composition according to claim 1, wherein the total content of polycyclic aromatic compounds other than the polycyclic aromatic compound according to claim 1 is 5% 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 1 or 2 , 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 1 to 3 , wherein the sulfur content is 10 ppm by mass or less. The Fischer-Tropsch fuel oil base material produced by synthesis, anthracenes, and 0.05 wt% to 2 wt% of one or more polycyclic aromatic compounds in total selected from the group consisting of di-methylation naphthalene blend The manufacturing method of the fuel composition containing this.