JP5205640B2 - Method for producing fuel oil composition for diesel engine - 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. There have been reports of techniques aimed at providing a fuel oil composition for diesel engines that can avoid troubles such as breakage. (For example, Patent Document 1)

Japanese Patent Application No. 2006-328656

In the technique disclosed in Patent Document 1, in order to maintain the characteristics under high pressure in addition to the high cloud point (crystal precipitation at normal pressure), which is a problem with n-paraffin fuel, aromatic carbonization with high dissolving power is achieved. The problem is solved by mixing with a light oil composition containing hydrogen, naphthene, and isoparaffin. However, in order to maintain the high ignitability that is an advantage of n-paraffin fuel, a small amount is more soluble. It is desirable to mix with a high fuel oil composition (containing a large amount of aromatic hydrocarbon, naphthene and isoparaffin). However, since the increase in aromatic hydrocarbons increases the PM in the exhaust gas, it is preferable to use naphthene or isoparaffin as the main component, but heavy oil fuels that are difficult to burn due to recent environmental problems There is a flow of white oil. The composition of the fuel obtained by cracking heavy oil represented by coker etc. contains a lot of naphthene, and when considering the future direction of fuel, the main component is naphthene. It is important to establish technology for using fuel oil compositions.
On the other hand, as the amount of naphthenes increases, the fuel oil composition containing the optimum amount of naphthenes is desired because crystals tend to precipitate as the fuel pressure increases.

  The present invention reflects the above-mentioned social demands and technical problems in fuel quality, and maintains fuel spray properly even in operating conditions under all circumstances, and functions of a high-pressure injection device and a post-processing device. In order to fully exhibit the fuel, the state of the fuel can be maintained as a liquid state even under an ultra-high pressure such as that used in a high-pressure injection device, and an appropriate combustion state can be maintained by maintaining the fuel spray form. An object of the present invention is to provide a fuel oil composition for a diesel engine that can avoid troubles such as breakage of a nozzle hole of an injector.

  As a result of examining the knowledge of Patent Document 1 in more detail, the inventors of the present invention use a base material having a specific naphthene content to obtain a fuel having an appropriate composition and properties as a fuel oil composition. The inventors have obtained knowledge that enables appropriate fuel spraying below, and have completed the present invention.

  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 ) A fuel oil base material having a naphthene content of 20 to 80% by volume, an aromatic hydrocarbon content of 40% by volume or less, a 90% by volume distillation temperature of 315 to 360 ° C., and a Kauri butanol number of 13 or more. And paraffin gas oil are blended so that the content of the fuel oil base is 5 to 55% by volume based on the fuel oil composition obtained,
10% by volume distillation temperature is 180 to 245 ° C., 90% by volume distillation temperature is 315 to 350 ° C., has a sulfur content of 10 mass ppm or less, and saturated hydrocarbon is 85 to 100% by volume. The aromatic hydrocarbon is less than 15% by volume, the content of the bicyclic aromatics is 1.5% by volume or less, and the content of the polycyclic aromatics having 3 or more rings is 0.5% by volume or less. A fuel oil composition having a naphthene content of 3 to 6.6 % by volume, a polycyclic naphthene content of 3.4 % by volume or less, and an isoparaffin content of 5 to 90% by volume is obtained. A method for producing a fuel oil composition for a diesel engine.

  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 naphthene content of the fuel oil base contained in the diesel engine fuel oil composition of the present invention is 20 to 80% by volume, preferably 25 to 80% by volume.
If the naphthene content is 20% by volume or more, the cloud point can be lowered by mixing with fuel oil, and if it is 80% by volume or less, the boundary between the solid state and the liquid state of the fuel oil composition is obtained. It is possible to suppress the inclination of the solid-liquid equilibrium line to be too small, which is preferable.

  The content of naphthenes here is determined by gas chromatography-mass spectrometry (GC-MS) of saturated hydrocarbons after fractionated and collected into aromatic hydrocarbons and saturated hydrocarbons by high performance liquid chromatography (HPLC). And analyzed in accordance with ASTM D 2786, and calculated the ratio of naphthenes for each ring number. The ratio obtained here was determined as JPI-5S-49-97 “Petroleum products—Hydrocarbon type test method—High-speed liquid”. It is calculated by multiplying the ratio of saturated hydrocarbons determined by “chromatographic method”.

The 90 vol% distillation temperature of the fuel oil base contained in the diesel engine fuel oil composition of the present invention is 315 to 360 ° C, preferably 315 to 355 ° C.
If the 90% by volume distillation temperature is 315 ° C or higher, the kinematic viscosity can be maintained appropriately, and if it is 360 ° C or lower, heavy components in light oil, particularly polycyclic aromatic hydrocarbons, are suppressed to a low level. This is preferable because it can maintain good flammability.

The aromatic hydrocarbon content of the fuel oil base contained in the fuel oil composition for a diesel engine of the present invention is 40% by volume or less, preferably 35% by volume or less, and there is no limitation on the lower limit. More preferably, it is 0% by volume.
When the aromatic hydrocarbon content is 40% by volume or less, it becomes possible to lower the cloud point of the fuel oil when mixed into the fuel oil composition for a diesel engine, and low temperature characteristics such as clogging points are obtained. It is possible to improve, which is preferable.

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

The kauri butanol number of the fuel oil base material contained in the fuel oil composition for a diesel engine of the present invention is 13 or more, preferably 15 or more, and more preferably 15 to 50.
When the Kauri butanol number is 13 or more, it becomes possible to lower the cloud point of the fuel oil when mixed into the fuel oil composition for diesel engines, and it is possible to improve the low temperature characteristics typified by clogging points. It is preferable.

  In addition, the kauri butanol value here shows the relative dissolving power of hydrocarbon, and shows that resin solubility is so high that a kauri butanol value is high. The measuring method of the Kauri-butanol value in this invention can be calculated | required based on ASTMD1133.

Content of the said fuel oil base material in the fuel oil composition for diesel engines of this invention is 5-55 volume%, Preferably, it is 7-50 volume%.
If the content is 5% by volume or more, the cloud point of the fuel oil can be greatly lowered, which is preferable. Further, when the content is too large, the cetane number decreases and the slope of the solid-liquid equilibrium line representing the boundary between the solid state and the liquid state of the fuel oil composition becomes too small. is there.

The distillation property of the fuel oil composition for diesel engines in the present invention has a 10 vol% distillation temperature of 180 to 245 ° C, preferably 183 to 243 ° 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 245 ° 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, particularly polycyclic aromatic hydrocarbons, are kept at a low level. This is preferable because it can maintain good flammability.

Moreover, the sulfur content contained in the fuel oil composition for diesel engines in the present invention is 10 mass ppm or less, preferably 8 mass ppm 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 85 to 100% by volume, preferably 90 to 100% by volume, and the aromatic hydrocarbon is less than 15% by volume, preferably 2% by volume or more and less than 15% by volume. It is. 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. Is more preferable.

  Emissions of PM and NOx during combustion by reducing saturated hydrocarbons to 85% by volume or more and aromatic hydrocarbons to less than 15% by volume, especially by controlling 2-ring aromatics and polycyclic aromatics having 3 or more rings to a low level Can be reduced. Therefore, when aromatic hydrocarbons are zero (saturated hydrocarbons are 100% by volume), the amount of PM and NOx emissions during combustion can be reduced as much as possible, which is preferable.

  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 fuel oil composition for diesel engines in the present invention is 3 to 40% by volume, preferably 5 to 38% by volume, of which the content of polycyclic naphthenes having two or more rings is 20% by volume or less, Preferably it is 10 volume% or less, there is no limitation about a minimum, it is so preferable that it is small, and it is more preferable that it is 0 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. If the naphthenes are 3% by volume or more, it is preferable because the dissolving power of the fuel oil composition for diesel engines can be improved and the low-temperature performance represented by cloud point can be improved. The naphthenes are preferably 40% by volume. In the following, it is preferable that the polycyclic naphthenes be 20% by volume or less, because the inclination 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 20 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%.

  The cloud point of the fuel oil composition for diesel engines in the present invention is 0 ° C. or lower, more preferably −2 ° C. or lower. By setting the cloud point to 0 ° C. or lower, it is possible to improve low temperature characteristics typified by a clogging point and the like, which is preferable.

  In the fuel oil composition for a diesel engine in the present invention, the crystal precipitation temperature at 50 MPa is 20 ° C. or less, more preferably 15 ° C. or less, and the crystal precipitation temperature at 150 MPa, which is a higher pressure, is 40 ° C. or less, more preferably. It is 35 degrees C or less. In addition, the slope of the solid-liquid equilibrium line representing the boundary between the solid state and the liquid state of the fuel oil composition is preferably −0.01 or more, more preferably −0.005 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 engine startup, the engine malfunction immediately after startup can be prevented, and the crystal at 150 MPa can be prevented. By setting the precipitation temperature to 40 ° C. or lower, it is possible to avoid crystal precipitation in the ultra-high pressure injection that accompanies an operation with a high load immediately after engine startup. If the slope of the solid-liquid equilibrium line is -0.01 or more, even if crystals are precipitated by an arbitrary 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 and the solid-liquid equilibrium line at 50 MPa and 150 MPa 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 according to the present invention requires a fuel oil base material having a specific amount of naphthenes, aromatic hydrocarbon content, 90% by volume distillation temperature, and Kauri-butanol number. . This is produced, for example, by decomposing heavy oil such as a coker or hydrodesulfurizing decomposed light oil obtained from a catalytic cracker.

  Other than the above-mentioned base material is not particularly limited. For example, kerosene is used for a light oil fraction that has been subjected to treatment such as hydrodesulfurization and aromatic extraction treatment by adjusting its distillation properties by distillation from various petroleum fractions. Etc. can be blended as appropriate. 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 not mixed with kerosene fractions, and diesel oil fractions that are fractionated after heavy oil is upgraded by catalytic cracking, hydrodesulfurization, hydrocracking treatment, dearoma treatment, etc. However, it can be used as long as its properties satisfy the above-mentioned properties, and is not particularly limited. However, crude oil that does not contain naphthene or polycyclic naphthene that promotes solidification under ultra high pressure. Or by selectively using a substrate obtained by 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 properties, sulfur content, and 30 ° C. kinematic viscosity were measured according to the method defined in JIS K 2204. In addition, 15 ° C. density was measured by JIS K 2249, and cloud point was measured by JIS K 2269 method.

Kauributanol number was measured based on ASTM D 1133.
The analysis conditions are shown below.
That is, 20 ± 0.1 g of a standard kauributanol solution prepared with natural kauri resin and butyl alcohol was placed in a 200 milliliter (hereinafter referred to as “mL”) Erlenmeyer flask, and the Erlenmeyer flask was added to an aqueous solution maintained at 25 ± 1 ° C. Soaked. Next, toluene was first taken into a burette and titrated into the above Erlenmeyer flask. The end point was set when the print type was placed under the flask and the type stroke was unclear. Similarly, titration is also performed for a mixed solution of toluene and n-heptane (volume ratio of toluene 25: n-heptane 75). Then, the oil for measuring the Kauri-butanol value (hereinafter referred to as “sample”) was taken in a burette and titrated by the same operation. The Kauri-butanol value was calculated by the following formula (1).

  In the above Kauri-butanol number measurement method, the standard Kauri-butanol solution has a Kauri-butanol value of 100 to 110 when titrated with toluene, and a Kauri-butanol value when titrated with a mixed solution of toluene 25: heptane 75 at a volume ratio. Is adjusted in advance to be 40.

The ratio of saturated hydrocarbons and aromatic hydrocarbons and the ratio of aromatic hydrocarbons by number of rings were measured based on 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.

For isoparaffin, the sum of the naphthenes obtained by the above method and the content of n-paraffin shown below converted to volume% is determined by JPI-5S-49-97 "Petroleum products-Hydrocarbon type test method- It can be determined by subtracting from the saturated hydrocarbon determined by “high performance liquid chromatography”.
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.
-About fuel oil composition for naphthenes A and B and diesel engines Equipment: 5890 series 2 (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)
-About naphthene C and paraffin light oil Apparatus: 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>
Paraffin light oil Using commercially available n-paraffin solvent (n-C7 to n-C21), paraffin having a boiling point of 300 ° C. or higher is added to 60% by mass of an n-paraffin mixture adjusted to have a boiling range of 260 to 330 ° C. WAX was hydrocracked at a reaction temperature of 260 ° C. and a hydrogen pressure of 10 MPa using a zeolite catalyst, and then 40% by mass of hydrocracked oil having a boiling point range of 250 to 320 ° C. obtained by fractional distillation by atmospheric distillation. By mixing, the paraffin light oil base material of the property shown in Table 1 was obtained.
・ Naphthenic A
A commercially available naphthene and isoparaffin were prepared so as to have a boiling range of 208 to 245 ° C., and naphthene A having the properties shown in Table 2 having a naphthene content of 47.7% by volume was obtained.
・ Naphthenic B
The cracked gas oil obtained from the catalytic cracker is hydrorefined and adjusted to have a boiling point range of 180.5 to 350 ° C. The naphthene content is 59.0% by volume, and the properties of naphthene B shown in Table 2 Got.
・ Naphthenic C
Using a commercially available n-paraffin solvent (n-C9 to n-C21) and a commercially available n-paraffin reagent, the boiling point range was adjusted to 258.5 to 309.5 ° C., and the properties shown in Table 2 were obtained. Naphthene C was obtained.

<Example 1 >
A fuel oil composition for a diesel engine was obtained by mixing 90% by volume of paraffin gas oil and 10% by volume of naphthene 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 fuel oil composition for a diesel engine was obtained by mixing 90% by volume of paraffin light oil and 10% by volume of naphthene 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.

<Comparative example 2>
A diesel fuel oil composition was obtained by mixing 60% by volume of naphthene B with 40% by volume of paraffin light oil. 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., 50 MPa, and 40 ° C., 150 MPa, if the fuel in the high-pressure chamber is in the liquid state, the determination of “◯”, crystal precipitation is observed, or the fuel is solidified Then, it determined with "x".

Solubility shown in Kauri butanol value is mixed with an appropriate amount of the high INA excitation point B, it was lowered cloud point sufficiently Example 1 although the slope of the solid-liquid equilibrium line is not so large, 15 ℃, 50MPa, 40 ℃ , 150MPa Crystallization was not confirmed under both conditions. In contrast, cloud point in Comparative Example 1 obtained by mixing a low naphthenic C solubility is not lowered sufficiently, although the slope of the solid-liquid equilibrium line is greater Ri good Example 1, 15 ° C., 50 MPa, 40 ° C., Crystallization was confirmed under both conditions of 150 MPa. Further, in Comparative Example 2 containing naphthene B beyond the range of the present invention, the cloud point was sufficiently lowered, but the inclination of the solid-liquid equilibrium line was too small, so that crystals were precipitated under the conditions of 40 ° C. and 150 MPa. Occurred.

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. Curve 2 in the figure shows the comparative example 1. At 15 ° C. and 50 MPa , Comparative Example 1 is at the solid-liquid interface, and the solid and liquid coexist.

It is the schematic of the experimental apparatus used for the measurement of a crystal precipitation pressure and a solid-liquid equilibrium line. Is a graph plotting the solid-liquid equilibrium line of specific Comparative Examples 1.

Claims (1)

A fuel base material having a naphthene content of 20 to 80% by volume, an aromatic hydrocarbon content of 40% by volume or less, a 90% by volume distillation temperature of 315 to 360 ° C., and a Kauri butanol number of 13 or more, and paraffin The light oil is blended so that the content of the fuel oil base is 5 to 55% by volume based on the fuel oil composition obtained,
10% by volume distillation temperature is 180 to 245 ° C., 90% by volume distillation temperature is 315 to 350 ° C., has a sulfur content of 10 mass ppm or less, and saturated hydrocarbon is 85 to 100% by volume. The aromatic hydrocarbon is less than 15% by volume, the content of the bicyclic aromatics is 1.5% by volume or less, and the content of the polycyclic aromatics having 3 or more rings is 0.5% by volume or less. A fuel oil composition having a naphthene content of 3 to 6.6 % by volume, a polycyclic naphthene content of 3.4 % by volume or less, and an isoparaffin content of 5 to 90% by volume is obtained. A method for producing a fuel oil composition for a diesel engine.

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