JP5520115B2 - Light oil composition - Google Patents

Description

  The present invention relates to a light oil composition, and more particularly to a light oil composition capable of reducing emissions of environmentally hazardous substances such as soot, nitrogen oxides, unburned hydrocarbons and carbon monoxide in exhaust gas. is there.

  Since the exhaust gas of a small diesel engine mounted on a passenger car contains nitrogen oxides and soot, from the viewpoint of environmental problems etc., the nitrogen oxides are temporarily stored by the nitrogen oxide storage catalyst, and then A method has been proposed in which unburned hydrocarbons and carbon monoxide in exhaust gas are oxidized by nitrogen oxides desorbed in a reducing atmosphere, and further, a filter is provided downstream to reduce soot released into the atmosphere. ing.

  On the other hand, the reduction of emissions of environmentally hazardous substances has also been studied from the aspect of fuel. For example, a high boiling point fraction of 310 ° C or higher greatly affects the generation of particulate matter, so 90% distillate. There have been proposed a light oil composition in which the generation of particulate matter is suppressed by lowering the temperature, and a light oil composition in which the solvent-soluble component constituting the particulate matter is reduced by lightening (Non-Patent Document 1). And 2). In addition, a fuel oil composition for diesel engines (Patent Document 1) containing a cetane number improver in order to significantly suppress the generation of particulate matter in the entire load range of the engine and having a 90% lower distillation temperature, A fuel oil composition for a diesel engine with a 90% distillation temperature and a low aromatic content of two or more rings has been proposed (Patent Document 2). In addition, in order to significantly reduce the emission of environmental pollutants such as particulate matter, nitrogen oxides and unburned hydrocarbons in the exhaust gas, the sulfur content is lowered and the distillation properties and aromatic content are under certain conditions. A diesel engine fuel oil composition (Patent Document 3) that satisfies the above has been proposed.

JP 2000-144155 A JP 2001-303076 A JP 2001-303080 A

Watanabe, Akimoto et al., “Emission reduction effect of lighter diesel oil”, Petroleum and petrochemical debate abstract, p. 172-173 (2000) Takei, Fujimoto et al., “Study on diesel oil properties for diesel exhaust reduction”, Automobile Engineering Society Academic Lecture Preprint, 9540426 (1995)

  However, according to these proposals, by reducing the light oil, the soot emission is reduced, but the resulting light oil composition is low in density and very light, resulting in a deterioration in fuel consumption and output. Cause incurring. Furthermore, the mixing of the light oil base and the kerosene base also reduces the kinematic viscosity of the composition, which tends to cause problems with the lubricating surface of the fuel injection pump and the like.

  The exhaust gas from the engine outlet is usually oxidized by the oxidation catalyst of the post-treatment catalyst, and the soot is removed by the diesel particulate filter (DPF). In this case, the amount of NOx is Since it does not change before and after, it is necessary to keep the NOx emission amount low at the engine outlet. In addition, if the amount of soot discharged is large, the amount of soot deposited on the DPF increases and the regeneration frequency increases. Therefore, it is desirable that the amount of soot discharged is low at the engine outlet. However, the aforementioned NOx emission amount and soot emission amount are generally in a trade-off relationship, and if one emission amount is reduced, the other emission amount is increased.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and appropriately combine the physical properties represented by the density and volatility of light oil with the chemical properties represented by the composition of light oil, thereby eliminating NOx emissions. An object of the present invention is to provide a light oil composition capable of reducing the amount of soot discharged in a trade-off relationship with the NOx emission amount while maintaining the amount low.

  As a result of diligent research on the influence of the light oil composition on the exhaust gas properties, the present inventors set the density of the light oil, the 90% distillation temperature of the volatile index, and the kinematic viscosity of the viscosity index within a specific range. The fuel composition of the flammability index (partially hydrogenated aromatic compounds of two or more rings, wholly aromatic compounds and naphthenic hydrocarbons (cyclic saturated hydrocarbons)) ), The exhaust gas properties can be optimized, and the present invention has been completed.

That is, the light oil composition of the present invention has a density at 15 ° C of 0.8209 to 0.8239 g / cm ³ , a sulfur content of less than 1 ppm by mass, and a 90% distillation temperature of 335.0 to 337.0 ° C. The kinematic viscosity at 30 ° C. is 4.132 to 4.146 mm ² / s, the cetane number is 63.2 to 66.6 , the total aromatic content is 1.7 to 7.7 % by volume, and the naphthene content is 57.8. ~ 66.0 vol% Aromatic compounds obtained by partially hydrogenating two or more aromatic compounds are 5.4 vol% or less as measured by a GC system comprising a GC and a time-of-flight mass spectrometer. Features.

The gas oil composition of the present invention has a sulfur content of less than 1 ppm by weight, a bicyclic aromatic content of 0.1 to 0.6 % by volume, a tricyclic or higher aromatic content of 0.2 % by volume or less, a naphthene content ( The volume ratio (N / P) between N) and the paraffin content (P) is preferably 2.0 to 2.1 .

  Here, the naphthene content means the content (volume%) of naphthenic hydrocarbons, that is, cyclic saturated hydrocarbons, and the paraffin content refers to the content of paraffinic hydrocarbons, that is, chain saturated hydrocarbons. (Capacity%).

  According to the light oil composition of the present invention, the amount of soot discharged can be reduced while keeping the amount of NOx emitted from the diesel engine low. Further, by reducing the amount of soot discharged, the combustion frequency of soot accumulated on the soot removal filter is reduced, and the carbon dioxide emission can be reduced.

(Cetane number)
In the light oil composition of this invention, it is necessary to make a cetane number into the range of 56-70. If the cetane number is too low, startability at low temperatures deteriorates and the amount of unburned hydrocarbons increases, so the cetane number is 56 or more, preferably 58 or more, more preferably 60 or more. On the other hand, if the cetane number is too high, ignition is likely to occur at high loads, and the premixing period becomes insufficient, and the amount of soot discharged increases, so the cetane number is 70 or less, preferably 68 or less, more preferably Is 66 or less. Here, the cetane number is measured by a method defined in JIS K2280 “Petroleum products-fuel oil-octane number and cetane number test method and cetane index calculation method”.

(Aromatic content)
In the light oil composition of the present invention, the total aromatic content needs to be 10% by volume or less. If the total aromatic content is too high, the amount of soot emission increases, and the amount of calorific value increases, so that the nitrogen oxide emission amount also increases. Therefore, the total aromatic content is 10% by volume or less, preferably 8 The capacity is less than%. On the other hand, even if the aromatic content is too low, the fuel consumption increases as the calorific value decreases, so the total aromatic content is preferably 1% by volume or more, more preferably 3% by volume or more. The bicyclic aromatic content is preferably 2% by volume or less, and more preferably 0.8% by volume or less, in order to reduce the amount of soot discharged. Similarly, from the viewpoint of reducing soot discharge, the aromatic content of three or more rings is preferably 1% by volume or less, more preferably 0.3% by volume or less. These aromatic components are measured by the method defined in JPI-5S-49-97 “Petroleum products—Hydrocarbon type test method—High performance liquid chromatograph method”.

(density)
In the light oil composition of the present invention, the density at 15 ° C. needs to be 0.815 g / cm ^{3 to} 0.825 g / cm ³ . By setting the density within this range, it is possible to maintain good fuel efficiency and optimize exhaust gas properties. The density is preferably more than 0.820 g / cm ³ and 0.825 g / cm ³ or less from the viewpoint of maintaining good fuel efficiency. The density is measured by a method defined in JIS K2249 “Crude oil and petroleum product density test method”.

(Kinematic viscosity)
Moreover, in the light oil composition of this invention, it is necessary to make kinematic viscosity in 30 degreeC into the range of 4.1-5.0 mm < ² > / s. By setting the kinematic viscosity within this range, the lubricity in the fuel injection pump can be maintained, and the atomization of the fuel during fuel injection can be promoted to improve the exhaust gas properties. The kinematic viscosity is preferably in the range of 4.10 to 4.50 mm ² / s from the viewpoint of further improving lubricity and exhaust gas properties. Here, the kinematic viscosity is measured at 30 ° C. by the method defined in JIS K2283 “Kinematic Viscosity Test Method”.

(Distillation properties)
In the light oil composition of the present invention, the 90% distillation temperature is set in the range of 325 to 340 ° C. from the viewpoint of reducing soot discharge by improving volatility and maintaining good fuel economy. There is a need. The 90% distillation temperature is preferably in the range of 330 ° C to 338 ° C from the viewpoint of further improving volatility and fuel consumption. In addition, this distillation property is calculated | required by the method prescribed | regulated to JISK2254 "distillation test method".

(Sulfur content)
In the light oil composition of this invention, a sulfur content is 10 mass ppm or less from a viewpoint of the reduction | decrease of the sulfur oxide in exhaust gas, and the durable improvement of the aftertreatment apparatus of exhaust gas. Further, in a vehicle equipped with a NOx occlusion reduction catalyst, fuel is used for regeneration of sulfur poisoning of the catalyst. Therefore, reduction of the sulfur content contributes to improvement of fuel consumption. And since these effects are so remarkable that a sulfur content is low, it is preferable that the sulfur content in the light oil composition of this invention is 1 mass ppm or less. The sulfur content is measured by the method defined in JIS K2541-6 “Sulfur content test method (ultraviolet fluorescence method)”.

(True calorific value)
In the light oil composition of the present invention, in order to improve fuel efficiency, the true calorific value is preferably in the range of 42800 to 43350 kJ / kg, more preferably 43100 to 43300 kJ / kg. Here, the true calorific value is obtained by a method defined in JIS K2279 “Crude oil and petroleum products—a calorific value test method and a calculation estimation method”.

(Partially hydrogenated aromatic content of 2 or more rings)
In the light oil composition of the present invention, from the viewpoint of reducing soot emissions and maintaining good fuel economy, the content of partially hydrogenated aromatics of two or more rings is less than 9% by volume, preferably 5% by volume. % Or less. Here, the partially hydrogenated aromatic component having two or more rings is an aromatic compound obtained by partially hydrogenating two or more aromatic compounds containing biphenyl, and is at least one benzene ring that is not hydrogenated. And the content (volume%) of an aromatic compound having at least two rings in which at least two hydrogen atoms are added to the benzene ring (hydrogenated). For example, tetralin and 9,10-dihydroanthracene are examples of partially hydrogenated aromatic compounds having two or more rings. In addition, the partially hydrogenated aromatic content of two or more rings can be adjusted by appropriately selecting the hydrodesulfurization conditions. If the amount of partially hydrogenated aromatics in two or more rings is too large, the aromatic content in two or more rings is likely to decrease, but the naphthene content and paraffin content described later are reduced, and the amount of soot discharged is likely to increase.

(For naphthenic)
In the light oil composition of the present invention, it is necessary to reduce the naphthene content to 52 to 75% by volume from the viewpoint of reducing soot discharge and maintaining good fuel economy. The naphthene content is preferably 55 to 70% by volume, more preferably 60 to 70% by volume, from the viewpoint of further reducing soot emission and further improving fuel consumption.

(Capacity ratio of naphthene and paraffin)
In addition to adjusting the naphthene content, the present inventors need to consider the relationship between the naphthene content and the paraffin content in order to ensure lubricity while reducing the amount of soot discharged. I found out. Therefore, the present inventors have examined that, in the light oil composition of the present invention, from the viewpoint of reducing the amount of soot discharged and maintaining the lubricity in the fuel injection pump, naphthene (N) and paraffin The volume ratio (N / P) of the minute (P) is preferably 1.8 to 2.2, more preferably 1.9 to 2.2.

  For analysis of the above-mentioned two or more partially hydrogenated aromatics, naphthenes and paraffins, GC with Agilent Technologies HP-6890N type FID detector and AccuTOF JMS-T100GC time-of-flight type manufactured by JEOL Ltd. A GC system consisting of a mass spectrometer was used. Detailed analysis conditions are as follows.

Primary column: Slight polar column (PTE-5 manufactured by Supelco, length 30 m, inner diameter 0.25 mm, film thickness 0.25 μm)
Modulator hollow column: length 2m, inner diameter 0.25mm
Secondary column: High-polarity column (SpelcoWAX10 from Supelco, length 2 m, inner diameter 0.25 mm, film thickness 0.25 μm)
Temperature rising condition: 10 ° C./min (from 50 ° C. (5 min hold) to 280 ° C. (27 min hold))
Inlet temperature: 280 ° C
Injection volume: 1.0 μl
Split ratio: 100: 1
Carrier gas: helium (He), 1.0 ml / min Modulator temperature: The following cold temperature and hot temperature are repeated.
Hot jet gas temperature: The temperature was raised from 150 ° C. (5 minutes hold) to 320 ° C. (33 minutes hold) at 10 ° C./min.
Cold jet gas temperature: about -140 ° C
Modulator frequency: 6 seconds for 0.3 seconds hot temperature, then 5.7 seconds for cold temperature.
Interface hollow column: 0.5m length, 0.25mm inner diameter
FID gas conditions: hydrogen (45 mL / min), air (450 mL / min), make-up helium (25 mL / min)

  Here, the GC system can measure a compound having 7 to 44 carbon atoms, and the compound corresponding to each peak (yamagata) is identified from the elution time and mass spectrum of the measured peak (yamagata). To do. The sum of all identified peaks (yamagata) is defined as the total content (100 peak volume%), and the content of each corresponding compound is calculated as the peak volume% from each peak (yamagata). To do.

(H / C ratio)
In the light oil composition of the present invention, from the viewpoint of further reducing the number of fine particles, the hydrogen / carbon ratio (H / C ratio) is preferably in the range of 1.8 to 2.0. It is preferable to be in the range of 95 to 2.0. The H / C ratio is obtained by measuring the hydrogen (H) content and carbon (C) content by organic elemental analysis to obtain the H / C ratio (molar ratio).

(Preparation of light oil composition)
The gas oil composition of the present invention is a distillate distilled as a raw material oil, for example, various gas oil fractions obtained from an atmospheric distillation apparatus, a catalytic cracking apparatus, a thermal cracking apparatus, or the like, that is, a boiling point of 140 to 400 ° C. It can be obtained by mixing and hydrodesulfurizing and mixing appropriately after hydrodesulfurization, or when processing raw material oils rich in aromatics, the sulfur content and aromatic content of the product should be reduced. It is effective to increase the reaction temperature and the hydrogen partial pressure and to increase the hydrogen / oil ratio in order to obtain a predetermined range. In addition, since the raw material oil containing a lot of aromatics contains a lot of difficult desulfurization components, it is preferable to use a catalyst that selectively removes sulfur in hydrodesulfurization. The hydrodesulfurization uses one or more of Co, Mo and Ni, and uses a hydrogenation catalyst supporting Zn, the reaction temperature is 200 to 400 ° C., the reaction pressure is 1.5 to 10 MPa in terms of hydrogen partial pressure, LHSV Is appropriately selected within the range of the conditions of 2.0 to 50 h ⁻¹ and the hydrogen / oil ratio of ¹ to 1000 NL / L, so that the light oil composition of the present invention described above can be obtained.

  In the present invention, the hydrodesulfurized gas oil fraction is a kerosene fraction, a by-product fraction when producing GTL, BTX, a by-product fraction when producing a lubricating oil, a normal paraffin compound, a normal paraffin series. Light oil composition suitable for the above-mentioned properties and quality by appropriately blending solvent, isoparaffin compound, isoparaffin solvent, aromatic compound, aromatic solvent, biomass-derived fuel base material, naphthene compound, naphthenic solvent, etc. Can be prepared.

  In addition, to the light oil composition obtained by the above method, known fuel additions such as a low temperature fluidity improver, an abrasion resistance improver, a cetane number improver, an antioxidant, a metal deactivator, and a corrosion inhibitor are added. An agent may be added. As the low temperature fluidity improver, an ethylene copolymer or the like can be used. In particular, a vinyl ester of a saturated fatty acid such as vinyl acetate, vinyl propionate or vinyl butyrate is preferably used. As the wear resistance improver, for example, a long-chain fatty acid (carbon number 12 to 24) or a fatty acid ester thereof is preferably used, and the wear resistance is sufficient with an addition amount of 10 to 500 ppm by mass, preferably 50 to 100 ppm by mass. Will improve.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

<Preparation of light oil composition>
First, light oil compositions (test light oils 1 to 4) used for the evaluation test were prepared as follows. Table 1 shows analytical values such as the composition of these test diesel oils 1 to 4. Although analysis is based on the method described above, the H / C ratio was measured for H and C using an organic element analyzer (CHN-1000 model manufactured by LECO) to determine the molar ratio of both. . The cetane index is measured by the method specified in JIS K2280 “Petroleum products—fuel oil—octane number and cetane number test method and cetane index calculation method”. It was measured by the method prescribed in “Hydrocarbon Type Test Method—High Performance Liquid Chromatograph Method”.

Test gas oil 1: 70% by volume of straight-run gas oil obtained by distillation of Middle Eastern crude oil, and hydrocracked and obtained by catalytic cracking of a vacuum gas oil fraction obtained by distillation of Middle Eastern crude oil A light oil fraction A was obtained by mixing 20% by volume of the pyrolytic oil obtained by pyrolyzing 10% by volume of the obtained light catalytic cracked oil and heavy oil mainly composed of vacuum residue.
Next, the volume ratio of CoMo / alumina (cobalt content 3 mass%, molybdenum content 13 mass%) and NiMo / alumina (nickel content 3 mass%, molybdenum content 12 mass%) prepared by the loading method. The reaction tube was filled to 1: 3. Then, as a pretreatment, light oil containing 1% by mass of dimethyl disulfide was passed through the reaction tube in the presence of hydrogen at 300 ° C. and 5 MPa to perform sulfurization treatment. Thereafter, the light oil fraction A was passed through the reaction tube and reacted under the conditions of a reaction temperature of 345 ° C., a hydrogen partial pressure of 7.0 MPa, an LHSV of 1.2 hr ⁻¹ , and a hydrogen / oil supply ratio of 440 NL / L. A light oil fraction B, which is a light oil fraction as a raw material, was obtained.
On the other hand, NiO—ZnO composite oxide (nickel content 17% by mass, zinc content 59% by mass) prepared by the coprecipitation method is charged into a new reaction tube, and hydrogen gas (purity 100% by volume) is charged into this. The reduction treatment was performed by circulating for 40 hours at a temperature of 300 ° C. and 3.0 MPa. Thereafter, the gas oil fraction B and hydrogen are passed through the reaction tube, the reaction temperature is 300 ° C., the hydrogen partial pressure is 3.0 MPa, the LHSV is 3.0 hr ⁻¹ , and the hydrogen / oil supply ratio is 400 NL / L. The test fuel 1 was obtained by hydrogenation reaction for 800 hours.

  Test gas oil 2: An experiment was performed in exactly the same way as test gas oil 1 except that the hydrogen partial pressure was 6.0 MPa in the hydrogenation reaction using the NiO-ZnO composite oxide described in Preparation method of test gas oil 1. Test fuel 2 was obtained.

  Test gas oil 3: Exactly the same experiment as test gas oil 1 except that the hydrogen partial pressure was 8.0 MPa in the hydrogenation reaction using the NiO-ZnO composite oxide described in the preparation method of test gas oil 1 Sample fuel 3 was obtained.

  Test diesel oil 4: The diesel fuel fraction B was used as the test fuel 4.

Next, for the above test diesel oil, using a commercially available diesel engine shown below, the smoke (煤) value (%) as an exhaust gas property immediately after the engine outlet in a steady condition was measured with a transmission smoke meter manufactured by SHIKENKEN, In addition, emissions (g / kWh) of nitrogen oxides (NOx), carbon monoxide (CO), unburned hydrocarbons (THC), and carbon dioxide (CO ₂ ) are measured with an exhaust gas analyzer manufactured by Best Sokki Co., Ltd. did. The obtained numerical values were evaluated relative to the test diesel oil 4 of Comparative Example 1. These results are shown in Table 2. In addition, (circle) is favorable with respect to a reference | standard, (triangle | delta) is equivalent to a reference | standard, and x shows that it is inferior to a reference | standard.

<Test engine specifications and operating conditions>
Number of cylinders: 4 cylinders Total displacement: Approximately 2L
Compression ratio: about 17
Maximum output: 103kW / 4000rpm
Regulatory compliance: European EUROIV regulations Steady conditions: 1500 rpm, 1/4 load

From these results, the test light oils 1 to 3 of Examples 1 to 3 which are light oil compositions of the present invention have the same NOx emissions and CO ₂ emissions as compared to the test light oil 4 of Comparative Example 1. It can be seen that the smoke emission amount is small, and the CO emission amount and the THC emission amount are also small.

  The light oil composition of the present invention can be suitably used as a diesel engine fuel or a mixed base material thereof.

Claims (2)

The density at 15 ° C. is 0.8209 to 0.8239 g / cm ³ or less, the sulfur content is less than 1 ppm by mass, the 90% distillation temperature is 335.0 to 337.0 ° C. , and the kinematic viscosity at 30 ° C. is 4.132. To 4.146 mm ² / s, cetane number of 63.2 to 66.6 , total aromatic content of 1.7 to 7.7 % by volume, naphthene content of 57.8 to 66.0 % by volume, two rings A gas oil composition , wherein the aromatic compound obtained by partially hydrogenating the above aromatic compound is 5.4 % by volume or less as measured by a GC system comprising a GC and a time-of-flight mass spectrometer . The sulfur content is less than 1 ppm by mass, the bicyclic aromatic content is 0.1 to 0.6 % by volume, the aromatic content of 3 or more rings is 0.2 % by volume or less, the naphthene content (N) and the paraffin content (P). The gas oil composition according to claim 1, wherein the volume ratio (N / P) to the gas is 2.0 to 2.1 .