JP5147549B2 - Fuel oil composition for diesel engines - Google Patents

Description

  The present invention relates to a fuel oil composition used in a high-pressure fuel injection type diesel engine, such as a common rail fuel injection device and a unit injector fuel injection device.

In recent years, reduction of exhaust gas emitted from automobiles and improvement of thermal efficiency have been demanded due to environmental problems. Diesel vehicles have better thermal efficiency than gasoline vehicles and have less CO ₂ emissions, but the impact on the human body due to particulate matter (PM) emissions and NOx emissions due to the diffusion combustion characteristic of diesel Concerns and adverse environmental impacts are a problem.

  In order to improve the combustion mode against the problem of PM and NOx discharged from these diesel vehicles, introduction of a common rail type fuel injection device and a fuel high pressure injection device represented by a unit injector method has been advanced. The high-pressure injection of fuel can improve the combustion mode by promoting atomization of the fuel injected into the engine cylinder and promoting mixing with the cylinder air. The maximum fuel injection pressure by the common rail type fuel injection device or the unit injector type fuel injection device is as high as about 160 to 200 MPa, whereas the injection pressure of the row type injection device which is a typical conventional vehicle is about 50 MPa. The pressure is further increased. In addition, these high-pressure fuel injection devices use electronic control to pool fuel that has already been increased in pressure rather than the fuel injection pressure corresponding to the engine speed so far, and determine the optimal fuel injection pressure based on operating conditions. In addition, since the injection is performed by adjusting the injection pressure, it is possible to maintain the optimum combustion state in the entire operation region. Further, in the above-described high-pressure injection type vehicle, the size of the injector nozzle injection hole is also smaller than before, which contributes to the miniaturization of the injected fuel.

  With the introduction of such a fuel injection device, the combustion mode has been greatly improved, and PM emissions and NOx emissions have been greatly reduced. And by reducing the exhaust gas from the engine out, it becomes possible to use various post-processing devices (DPF, DPNR, etc.) at the rear stage of the engine that could not be installed with the amount of PM and NOx exhausted from the conventional engine. A significant reduction in NOx has been achieved.

  However, considering the three-state diagram of a substance, even if it is a liquid substance at normal temperature and normal pressure, when it is exposed to an ultra-high pressure state such as 200 MPa, it changes to a solid state. Compared to the conventional fuel injection system, the new fuel injection system is more than three times the maximum pressure and the minimum pressure is 50 MPa or more, so the fuel pooled under high pressure is solidified and gelled. Is concerned. It is clear that the solidification / gelation of the fuel has a great influence on the spray shape of the fuel injection designed on the assumption that the fuel is liquid, and the solid or gel state is 200 MPa. There is a concern that these parts may be damaged in a high-pressure injection type vehicle in which the nozzle hole of the injector is smaller when it is injected at a very high pressure. Therefore, the fuel state can be maintained as a liquid state even under an ultra-high pressure used in a high-pressure injection device, and an appropriate combustion state can be maintained by maintaining the fuel spray form, and the nozzle hole of the injector is damaged. There have been reports of techniques aimed at providing a fuel oil composition for a diesel engine that can avoid this trouble. (For example, Patent Document 1)

Japanese Patent Application No. 2006-328655

In the technology disclosed in Patent Document 1, the content of aromatic hydrocarbons is defined as 15% by volume or more in order to maintain the characteristics of the fuel oil composition under high pressure. In order to sufficiently exhibit the ability of (DPF, DPNR, etc.), it is preferable to further reduce the aromatic hydrocarbon content in order to reduce the exhaust gas at the engine-out.
Furthermore, heavy oil whitening is being promoted as a means of purifying exhaust gas due to recent environmental problems, and by decomposing heavy oil represented by coker, etc. It is preferable that the range in which naphthenes contained in a large amount can be used is widened.
In addition, in order to obtain an operating state in which the fuel spray is properly maintained and the high-pressure injection device and the post-processing device can fully function in a wider temperature environment, the fuel oil does not generate deposits even at lower temperatures. A composition is desired.

  The present invention reflects the above requirements on the fuel quality, maintains the fuel spray properly even in the operating state under all circumstances, and sufficiently exhibits the functions of the high pressure injector and the aftertreatment device. The fuel state can be maintained in a liquid state even under ultra-high pressure as used in the above, and by maintaining the fuel spray form, an appropriate combustion state can be maintained and troubles such as breakage of the nozzle hole of the injector can be avoided. An object is to provide a fuel oil composition for a diesel engine.

As a result of examining the knowledge of Patent Document 1 in more detail, the present inventors have found that fuel having an appropriate composition and properties while reducing the aromatic hydrocarbon content can be used to achieve an appropriate fuel spray under high pressure. As a result, the present invention has been completed.
That is, the present invention provides a fuel oil composition suitable for a high-pressure fuel injection type diesel engine such as a common rail type fuel injection device and a unit injector type fuel injection device having the following characteristics.

(1) Containing 5 to 40 % by volume of a fuel oil base material having an isoparaffin content of 25% by volume or more, a 90% by volume distillation temperature of 290 to 350 ° C., and a paraffin branching index of 0.3 to 0.75. ,
10% by volume distillation temperature is 180-225 ° C., 90% by volume distillation temperature is 315-350 ° C., has a sulfur content of 10 mass ppm or less, saturated hydrocarbon is 70-98% by volume, The aromatic hydrocarbon is 2 to 30% by volume, the bicyclic aromatics content is 1.5% by volume or less, and the polycyclic aromatics having 3 or more rings is 0.5% by volume or less. A diesel engine having a naphthene content of 39.2 to 68 vol %, a polycyclic naphthene content of 35 vol% or less, and an isoparaffin content of 5 to 15.1 vol% Fuel oil composition.
(2) The fuel oil composition for a diesel engine according to (1), which is used for a diesel engine having a fuel injection pressure of 50 MPa or more.

  According to the diesel fuel oil composition of the present invention, the solidification / gelation that occurs when the fuel is brought to a high pressure is suppressed, an appropriate combustion state is maintained, and mechanical damage to the injector is avoided. Can do.

Details of the invention are described below.
The isoparaffin content of the fuel oil base contained in the fuel oil composition for diesel engines of the present invention is 25% by volume or more, preferably 25 to 98% by volume.
If the isoparaffin content is 25% by volume or more, it is possible to keep a large gradient of the solid-liquid equilibrium line representing the boundary between the solid state and the liquid state of the fuel oil composition, which will be described later.

The 90 vol% distillation temperature of the fuel oil base contained in the diesel engine fuel oil composition of the present invention is 290 to 350 ° C, preferably 292 to 347 ° C.
If the 90% by volume distillation temperature is 290 ° C or higher, the kinematic viscosity can be kept appropriately, and if it is 350 ° C or lower, heavy components in light oil, especially aromatic hydrocarbons, can be suppressed to a low level. The flammability can be kept good, which is preferable.

  The paraffin branching index of the fuel oil base contained in the diesel engine fuel oil composition of the present invention is 0.3 to 0.75, preferably 0.3 to 0.73. The paraffin branching degree index is an index representing the average degree of branching of paraffin molecules, and is represented by the proton ratio of the terminal methyl group when the integral value of all protons measured by 1H-NMR is 1. . The larger the paraffin branching index, the greater the proportion of isoparaffin in the paraffin, or the greater the degree of branching of the isoparaffin molecule itself.

  If the paraffin branching index of the base material is 0.3 or more, the n-paraffin ratio is small, the low temperature fluidity is good, and the effect as a solvent is high, and the cloud point of the fuel oil composition is reduced. It is preferable because it can be lowered. If the paraffin branching index is too large, the viscosity may be too high and the oil permeability may be lowered, and the cetane number may be lowered. It is preferable because it can be made into a valence.

Content of the said fuel oil base material in the fuel oil composition for diesel engines of this invention is 5-80 volume%, Preferably, it is 7-80 volume%.
If the content is 5% by volume or more, the cloud point of the fuel oil can be lowered, and the inclination of the solid-liquid equilibrium line representing the boundary between the solid state and the liquid state of the fuel oil composition can be kept large. ,preferable. Moreover, when there is too much content, since a viscosity will become high too much and oil permeability may fall, and there exists a possibility that a cetane number may fall, it is suitable to set it as 80 volume% or less.

  The distillation property of the fuel oil composition for diesel engines of the present invention has a 10 vol% distillation temperature of 180 to 225 ° C, preferably 183 to 222 ° C, and a 90 vol% distillation temperature of 315 to 350 ° C, preferably 317 to 347 ° C.

  If the 10% by volume distillation temperature is 180 ° C. or higher, the flash point and kinematic viscosity appropriate for light oil can be maintained, and if it is 225 ° C. or lower, it has moderate volatility. And the like, and the PM derived from heterogeneous mixed combustion can be reduced. If the 90 vol% distillation temperature is 315 ° C or higher, the kinematic viscosity can be maintained appropriately, and if it is 350 ° C or lower, heavy components in light oil, especially aromatic hydrocarbons, can be suppressed to a low level. The flammability can be kept good, which is preferable.

Moreover, the sulfur content contained in the diesel engine fuel oil composition of the present invention is 10 ppm by mass or less, preferably 8 ppm by mass or less. By setting the sulfur content to 10 mass ppm or less, it is preferable that the amount of sulfate, which is a component of particulate matter (PM) discharged from the engine, is reduced and the influence on the performance of the exhaust gas aftertreatment device is reduced.
The distillation properties in the present invention can be measured by the atmospheric pressure distillation test of JIS K2254, and the sulfur content can be measured by the microcoulometric titration method of JIS K2541.

  The saturated hydrocarbon in the diesel engine fuel oil composition of the present invention is 70 to 98% by volume, preferably 75 to 97% by volume, aromatic hydrocarbon is 2 to 15% by volume, preferably 3 to 10% by volume, Preferably it is 3-6 volume%. The content of bicyclic aromatics in aromatic hydrocarbons is 1.5% by volume or less, preferably 1.4% by volume or less, and there is no limitation on the lower limit. More preferred. The content of polycyclic aromatics having 3 or more rings is 0.5% by volume or less, preferably 0.3% by volume or less, and there is no limitation on the lower limit. preferable.

  Emissions of PM and NOx during combustion by reducing saturated hydrocarbons to 70% by volume and aromatic hydrocarbons to 30% by volume or less, especially by controlling low-level 2-ring aromatics and polycyclic aromatics having 3 or more rings. Can be reduced. Further, by setting the aromatic hydrocarbon to 2% by volume or more, it becomes possible to appropriately swell various rubber seals used in the fuel supply line of the engine and to ensure sealing performance. Therefore, the saturated hydrocarbon is preferably 98% by volume or less.

  In addition, the composition ratio here is calculated | required based on JPI-5S-49-97 "petroleum product-hydrocarbon type test method-high performance liquid chromatograph method (HPLC)".

  The naphthene content in the diesel engine fuel oil composition of the present invention is 68% by volume or less, preferably 65% by volume or less, and there is no limitation on the lower limit. . Among them, the content of polycyclic naphthenes having two or more rings is 35% by volume or less, preferably 30% by volume or less, and there is no limitation on the lower limit, and the smaller the value, the more preferable it is 0% by volume. Naphthenes and polycyclic naphthenes generally have high dissolving power following aromatic compounds, but most of them have a shape that is molecularly close to a planar structure under an ultrahigh pressure of 50 MPa or more. Tends to solidify. Here, examples of naphthenes include cyclohexane and cyclopentylcyclohexane, and examples of bicyclic naphthenes include dicyclohexylethane and decalin. Examples of naphthenes having 3 or more rings include tetradecahydroanthracene. It is preferable that the naphthenes are 68% by volume or less, particularly the polycyclic naphthenes are 35% by volume or less because the slope of the quadratic curve of the solid-liquid equilibrium line (pressure-temperature curve) can be kept large.

  The naphthenes content ratio here is determined by gas chromatographic analysis of saturated hydrocarbons after fractionating the fuel oil composition for diesel engines into aromatic hydrocarbons and saturated hydrocarbons by high performance liquid chromatography (HPLC). Analysis by mass spectrometry (GC-MS), analysis according to ASTM D 2786, calculation of the ratio of naphthenes for each ring number, and the ratio obtained here is determined as JP-5S-49-97 “Petroleum products— It is determined by multiplying the ratio of saturated hydrocarbons determined by “Hydrocarbon Type Test Method—High Performance Liquid Chromatograph Method”.

  The content of isoparaffin in the fuel oil composition for diesel engines of the present invention is 5 to 90% by volume, preferably 10 to 90% by volume. When the isoparaffin is 5% by volume or more, the slope of the quadratic curve of the solid-liquid equilibrium line (pressure-temperature curve) can be kept large, and if it is 90% by volume or less, the combustibility of the fuel oil composition is improved. An appropriate range can be maintained.

  In addition, isoparaffin content ratio here is naphthene content and n-paraffin content from saturated hydrocarbon calculated | required by JPI-5S-49-97 "petroleum product-hydrocarbon type test method-high performance liquid chromatograph method". It can be obtained by subtracting the sum of The n-paraffin content can be obtained by gas chromatography (GC), and can be obtained by converting this to volume%.

  In the fuel oil composition for diesel engines of the present invention, the crystal precipitation temperature at 50 MPa is 20 ° C. or less, more preferably 15 ° C. or less. In addition, the boundary between the solid state and the liquid state of the fuel oil composition The slope of the solid-liquid equilibrium line to be expressed is preferably −0.030 or more, and more preferably −0.028 or more.

  If the crystal precipitation temperature at 50 MPa is 20 ° C. or less, the fuel can be kept in a liquid state at the pressure of the high-pressure fuel injection device immediately after the engine is started, and the engine malfunction immediately after the start can be prevented. If the slope of the solid-liquid equilibrium line is -0.030 or more, even if crystals are precipitated by a certain pressure increase, the state changes from a solid phase to a liquid phase by a small temperature increase (a small amount of heat input). Therefore, it is preferable for maintaining the liquid phase state.

  The crystal precipitation pressure at 50 MPa and the solid-liquid equilibrium line can be obtained using the experimental apparatus shown in FIG. As shown in FIG. 2, the solid-liquid equilibrium line indicates the pressure at which crystals are precipitated in the sample chamber when the temperature in the high pressure chamber is fixed at an arbitrary temperature of −30 to 80 ° C. and the pressure is increased in steps of 5 MPa. The graph can be drawn as a quadratic function graph by plotting on a graph of horizontal axis: temperature, vertical axis: crystal precipitation pressure, and connecting a plurality of points.

  As described above, the fuel oil composition for a diesel engine of the present invention essentially includes a fuel oil base material having a specific amount of isoparaffin, a 90% by volume distillation temperature, and a paraffin branching index. This base material is manufactured by hydrocracking paraffin WAX having a boiling point of 300 ° C. or higher using a zeolite catalyst or the like, and then fractionated by atmospheric distillation, or is commercially available as an isoparaffin solvent. Can be used.

  Furthermore, as a base material other than the above, for example, kerosene or the like is appropriately added to a light oil fraction that has been subjected to treatment such as hydrodesulfurization and aromatic extraction treatment by adjusting the distillation properties of various petroleum fractions by distillation. It can be blended and manufactured. As JIS standard light oil, No. 1, No. 2, No. 2, No. 3, and No. 3 can be used in general, and are not particularly limited. Other diesel oil bases that do not contain kerosene fractions, or diesel oil that is fractionated after heavy oil is catalytically cracked, hydrodesulfurized, hydrocracked, dearomatized, and upgraded with heavy oil by coker, etc. The fraction can be used as long as its properties satisfy the above-mentioned properties, and is not particularly limited, but does not include naphthene or polycyclic naphthene that promotes solidification under ultrahigh pressure. It can be suitably produced by selecting a crude oil or selectively using a base material such as hydrogenating these substances in a hydrodesulfurization reaction.

  It is preferable to add the low temperature fluidity improver to the fuel oil composition for a diesel engine of the present invention in an amount of 10 to 1000 ppm by volume, preferably 50 to 700 ppm by volume. Addition of 10 ppm by volume or more of the low temperature fluidity improver is preferable because the clogging point (CFPP) and the pour point (PP) can be improved. Moreover, it is preferable that the addition amount of the low temperature fluidity improver is 1000 ppm by volume or less because aggregation of the additive itself can be prevented.

  Various low temperature fluidity improvers used in the present invention can be used, for example, alkenyl succinimide, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, copolymer polymer such as polyethylene glycol derivative, Examples thereof include polymers such as chlorinated polyethylene and polyalkyl acrylate. These low temperature fluidity improvers may be used singly or in combination of two or more.

  Moreover, various other additives can be suitably mix | blended with the fuel oil composition for diesel engines of this invention as needed. Examples of such additives include lubricity improvers, cetane number improvers, surfactants, preservatives, rust preventives, defoamers, detergents, antioxidants, hue improvers, and other known fuel additives. Is mentioned. These can be added singly or in combination.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not restrict | limited at all by these examples.

  In Examples and Comparative Examples, the flash point, distillation property, sulfur content, 30 ° C. kinematic viscosity, and measurement were performed according to JIS K 2204. In addition, the 15 ° C. density was measured according to JIS K 2249, and the cloud point was measured according to JIS K 2269.

The paraffin branching index of isoparaffins A, B, and C was calculated as the proton ratio of the terminal methyl group when the integrated value of all protons measured by 1H-NMR was 1. The measurement conditions of 1H-NMR are shown below.
Apparatus: Nuclear magnetic resonance apparatus Alpha-400 manufactured by JEOL Ltd.
Sample tube: 5mm
Sample amount: 0.1g
Solvent: Deuterated chloroform (0.5 ml)
Accumulation count: 4 times Proton chemical shift range ・ Methyl proton: 0.5-1.0ppm
Methylene and methine protons: 1.0-2.0ppm

The ratio of saturated hydrocarbons and aromatic hydrocarbons and the ratio of aromatic hydrocarbons by number of rings were measured according to JPI-5S-49-97. The apparatus configuration and analysis conditions of HPLC are shown below.
Equipment: Agilent 1100 Series (ALS: G1329A, Bin Pump: G1312A, Degasser: G1379A, Rid: G1362A, Colcom: G1316A)
Mobile phase: n-hexane Flow rate: 1.0 ml / min
Column: Silver nitrate impregnated silica column (4.6 mm ID * 70 mm L. AgNO3-1071-Y manufactured by Senshu Scientific)
Amine modified column (4.0 mm ID * 250 mm L. 2 Senshu Scientific LICHROSORB-NH2)
Column temperature: 35 ° C
Sample concentration: 10 vol%
Injection volume: 5 μl

The content of naphthenes and ring-based naphthenes, and isoparaffin analysis were performed by the following methods.
First, a sample was fractionated by saturated hydrocarbons and aromatic hydrocarbons by HPLC, and then type analysis was performed on the saturated hydrocarbons by GC-MS. Based on the analysis result obtained here, analysis was performed according to ASTM D 2786, and the content ratio of paraffins, naphthenes and ring-based naphthenes in saturated hydrocarbons was determined. By multiplying the ratio of naphthenes and naphthenes by number of rings in the saturated hydrocarbon obtained here to the ratio of saturated hydrocarbons obtained as described above, the contents of naphthenes and naphthenes by number of rings are reduced. Asked.

The content of isoparaffin is the sum of the naphthenes obtained by the above method and the content of n-paraffin shown below converted to volume%, as defined in JP-5S-49-97 “Petroleum products-hydrocarbon type. It calculated | required by subtracting from the saturated hydrocarbon calculated | required by the "test method-high performance liquid chromatograph method".
The analysis conditions are shown below.
Apparatus: HP-6890 HP5973 Quadrupole mass spectrometer Column: DB-1: 30 m × 0.25 mm I.D. D. × 0.25μm
Oven temperature: 40 ° C. (1 min) → 10 ° C./min→280° C. (5 min)
Inlet temperature: 43 ° C. Even track mode ON
Interface temperature: 300 ° C
Carrier gas: He: 55 KPa Constant flow mode ON
Solvent Delay: 4.5min
Mass range: 50-500 Threshold = 100 Sampling # 3
Ionization voltage: 70 eV
Injection method: On-column injection 1.0 μl

The n-paraffin content was measured by gas chromatography (GC). The measurement conditions are shown below.
・ Desulfurized diesel oil and diesel engine fuel oil composition Equipment: 5890 series2 (Agilent Technologies)
Column: Ultra 1 (Agilent) Crosslinked Methyl Silicone Gum, 50 m × 0.20 mm I.D. D. Film thickness 0.33μm
Detector: FID
Oven temperature: 60 ° C. (0 min) − (6 ° C./min)→340° C. (10 min) Run 56.7 min
Inlet: On-column
Inlet temperature: oven track mode (oven temperature + 3 ° C)
Detector temperature: 350 ° C
Carrier gas: He 280 kPa (constant pressure) 1.3 mL / min Linear velocity 29.7 cm / sec (at 60 ° C.)
Make-up gas: He
FID combustion gas: H2 30 mL / min, Air 400 mL / min
Injection volume: 0.2 μl
Quantitative method: Internal standard method (Internal standard substance: Dibutyl phthalate)
For isoparaffins A, B, and C Equipment: 6890 (Agilent Technologies)
Column: DB-1 30m x 0.25mmI. D. Film thickness 0.25μm
Detector: FID
Oven temperature: 50 ° C. (1 min) − (5 ° C./min)→340° C. (20 min) Run 79 min
Inlet: Split (Back) 100: 1
Carrier gas: He 83 kPa (constant pressure) 1.0 mL / min Total 100 mL / min
Average linear velocity: 26 cm / sec
Make-up gas: He
FID combustion gas: H2 30 mL / min, Air 400 mL / min
Injection volume: 0.1 μl
Sample dilution: 1/2 dilution with carbon disulfide Baseline: with correction

  The experimental apparatus in the present invention is shown in FIG. This experimental apparatus consists of a high-pressure chamber in which experimental samples are placed and a glass piston that moves up and down in response to pressure from a pressure medium (at normal temperature: water, at low temperature: ethanol). By pumping the pressure medium with a pump, the pressure in the high-pressure chamber can be increased from normal pressure to an arbitrary pressure of 300 MPa. At this time, the high pressure cell itself shown in the figure is filled with the pressure medium, so that the high pressure chamber and the outer wall of the piston can be observed without being deformed or damaged by the pressure. Observation in the high-pressure chamber can be optically performed by a microscope or the like through a glass piston through sapphire windows above and below the apparatus.

<Base material>
・ Desulfurized gas oil base material A gas oil fraction having a boiling point range of 185 to 380 ° C. and a 90% distillation temperature of 350 ° C. obtained by atmospheric distillation of a naphthene-based crude oil having a high content of naphthene and polycyclic naphthene has a sulfur content of 10 Hydrodesulfurization and dearoma treatment were carried out to a mass ppm or less to obtain a desulfurized light oil base material having the properties shown in Table 1.
・ Isoparaffin A
Paraffin WAX having a boiling point of 300 ° C. or higher is hydrocracked using a zeolite catalyst under the conditions of a reaction temperature of 260 ° C. and a hydrogen pressure of 10 MPa, and then fractionated by atmospheric distillation to have a boiling range of 177 to 324.5. Isoparaffin A having the properties shown in Table 2 was obtained at ° C.
・ Isoparaffin B
Using commercially available isoparaffin (isoparaffin content is 97.9% by volume), the boiling range was adjusted to 207 to 341.5 ° C., and isoparaffin B having the properties shown in Table 2 was obtained.
・ Isoparaffin C
Paraffin WAX having a boiling point of 300 ° C. or higher was hydrocracked using a zeolite catalyst under the conditions of a reaction temperature of 260 ° C. and a hydrogen pressure of 10 MPa, and fractionated by atmospheric distillation. -A boiling point range of 216 is obtained by mixing 80% by volume of a paraffin solvent (n-C9 to n-C21) and a commercially available n-paraffin reagent adjusted to have a boiling point range of 220 to 310 ° C. Isoparaffin C having the properties shown in Table 2 was obtained at ˜319.5 ° C.

<Example 1>
By mixing 40% by volume of isoparaffin A with 60% by volume of the desulfurized light oil base material, a fuel oil composition for a diesel engine was obtained. The resulting diesel engine fuel oil composition was mixed with a fluidity improver comprising an ethylene-vinyl acetate copolymer at 300 ppm by volume based on the total amount of the diesel engine fuel oil composition, and a lubricity comprising a long chain alkyl ester. The improver was added at 100 mg / kg to the total amount of the diesel engine fuel oil composition. Properties of the obtained diesel engine fuel oil composition are shown in Table 3.

<Example 2>
A fuel oil composition for a diesel engine was obtained by mixing 90% by volume of the desulfurized light oil base material and 10% by volume of isoparaffin B. The resulting diesel engine fuel oil composition was mixed with a fluidity improver comprising an ethylene-vinyl acetate copolymer at 300 ppm by volume based on the total amount of the diesel engine fuel oil composition, and a lubricity comprising a long chain alkyl ester. The improver was added at 100 mg / kg to the total amount of the diesel engine fuel oil composition. Properties of the obtained diesel engine fuel oil composition are shown in Table 3.

<Comparative Example 1>
A diesel engine fuel oil composition was obtained by mixing 97% by volume of the desulfurized light oil base material and 3% by volume of isoparaffin B. The resulting diesel engine fuel oil composition was mixed with a fluidity improver comprising an ethylene-vinyl acetate copolymer at 300 ppm by volume based on the total amount of the diesel engine fuel oil composition, and a lubricity comprising a long chain alkyl ester. The improver was added at 100 mg / kg to the total amount of the diesel engine fuel oil composition. Properties of the obtained diesel engine fuel oil composition are shown in Table 3.

<Comparative example 2>
A fuel oil composition for a diesel engine was obtained by mixing 90% by volume of the desulfurized light oil base material and 10% by volume of isoparaffin C. The resulting diesel engine fuel oil composition was mixed with a fluidity improver comprising an ethylene-vinyl acetate copolymer at 300 ppm by volume based on the total amount of the diesel engine fuel oil composition, and a lubricity comprising a long chain alkyl ester. The improver was added at 100 mg / kg to the total amount of the diesel engine fuel oil composition. Properties of the obtained diesel engine fuel oil composition are shown in Table 3.

  In Table 3, regarding the maintenance of the liquid state at 15 ° C. and 50 MPa, if the fuel in the high-pressure chamber is in a liquid state, the judgment is “◯”, if crystal precipitation is observed, or if the fuel is solidified, “×”. It was determined.

  In Examples 1 and 2 in which isoparaffins A and B having a high paraffin content and high paraffin branching degree index were mixed, no precipitation of crystals was observed at 15 ° C. and 50 MPa. However, in Comparative Example 1 in which only a small amount of isoparaffin B having a high paraffin branching index and isoparaffin content was mixed with the same light oil base as in Examples 1 and 2, precipitation of crystals was observed at 15 ° C. and 50 MPa. . In the case where a sufficient amount of isoparaffin C is mixed with the same light oil base as in Examples 1 and 2, the isoparaffin C has a low isoparaffin content and a paraffin branching index, so that crystal precipitation is observed at 15 ° C. and 50 MPa. As a result.

  FIG. 2 shows a solid-liquid equilibrium diagram of the fuel oil composition. The horizontal axis shows the sample temperature [° C.], and the vertical axis shows the crystal precipitation pressure [MPa] at a certain temperature. By plotting the crystal precipitation pressure at an arbitrary temperature at multiple points, the solid-liquid equilibrium diagram is usually It is drawn as a quadratic curve. The portion to the left of the solid-liquid equilibrium line indicates that crystals are deposited on the sample and are in a gel or solid state. Starting point of solid-liquid equilibrium diagram: The temperature of crystal precipitation in the sample when the pressure is 0 indicates a so-called cloud point. Even for samples with the same cloud point, the slope of the quadratic curve differs depending on the composition in the sample, and the solid state region of the sample varies greatly. In the figure, curve 1 represents Example 1 and curve 2 represents Comparative Example 1. In Example 1, it is in a liquid state at 15 ° C. and 50 MPa.

It is the schematic of the experimental apparatus used for the measurement of a crystal precipitation pressure and a solid-liquid equilibrium line. 2 is a graph in which solid-liquid equilibrium lines of Example 1 and Comparative Example 1 are plotted.

Claims (2)

5 to 40 % by volume of a fuel oil base material having an isoparaffin content of 25% by volume or more, a 90% by volume distillation temperature of 290 to 350 ° C., and a paraffin branching index of 0.3 to 0.75,
10% by volume distillation temperature is 180-225 ° C., 90% by volume distillation temperature is 315-350 ° C., has a sulfur content of 10 mass ppm or less, saturated hydrocarbon is 70-98% by volume, The aromatic hydrocarbon is 2 to 30% by volume, the bicyclic aromatics content is 1.5% by volume or less, and the polycyclic aromatics having 3 or more rings is 0.5% by volume or less. A diesel engine having a naphthene content of 39.2 to 68 vol %, a polycyclic naphthene content of 35 vol% or less, and an isoparaffin content of 5 to 15.1 vol% Fuel oil composition. The fuel oil composition for a diesel engine according to claim 1, which is used for a diesel engine having a fuel injection pressure of 50 MPa or more.

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