JP5627845B2 - Fuel oil composition for premixed compression ignition gasoline engine - Google Patents

Description

The present invention relates to a fuel oil composition for a premixed compression ignition (CAI) engine, and more particularly to premixed compression ignition (CAI) combustion when used in a premixed compression ignition (CAI) engine. The present invention relates to a fuel oil composition that can expand the operating range of an engine that can ensure the above to a range that cannot be achieved by conventional gasoline and that emits less CO ₂ .

Nitrogen oxides (NOx), particulate matter (PM), carbon monoxide (CO), and hydrocarbons (HC) emitted from automobiles have a certain contribution to the concentration of these harmful components in the atmosphere. From the viewpoint of improvement, reduction of these harmful exhaust gas components is strongly demanded. On the other hand, in order to prevent global warming, it is necessary to reduce the CO ₂ emitted by the combustion of fossil fuels, which reduces CO ₂ emissions from automobiles, that is, improves the fuel consumption efficiency (fuel consumption) of automobiles. There is a strong demand. As described above, in automobiles, it is necessary to simultaneously achieve emission reduction of harmful gas components and CO ₂ emission reduction. Recently, premixed compression ignition (HCCI) engine has attracted attention as a countermeasure technology. Has been. In general, a PCCI (Premixed Charged Compression Ignition) engine that achieves HCCI combustion with a diesel engine is an CAI engine that achieves HCCI combustion with a gasoline engine.

In the CAI engine, the start (ignition) of combustion depends on the self-ignition of fuel, and therefore, a fuel with good ignitability is required when the temperature in the combustion chamber is low or the load is low. However, fuel with good ignitability causes sudden combustion (knocking) due to multipoint simultaneous ignition in the combustion chamber under high load conditions where the temperature in the combustion chamber is high, resulting in increased combustion noise and engine damage. End up. Therefore, under high load conditions where the temperature in the combustion chamber is high, a fuel with low ignitability, that is, a fuel with high anti-knock property that exhibits a slow combustion behavior is required. Therefore, as the fuel for the CAI engine, it is necessary to control the ignitability and anti-knock property of the fuel to optimum values so that CAI combustion is established under a wide range of load conditions. Furthermore, in order to reduce the CO ₂ from the fuel, it is desired CO ₂ emissions per unit calorific value is small, a small CO ₂ emission intensity, and CAI combustion range is required wide fuel.

  There are cetane number and octane number as a scale (evaluation index) for expressing the ignitability and anti-knock property of conventional gasoline engine and diesel engine fuel. It is known that these evaluation indexes are insufficient for grasping the properties and compositions required for a fuel oil composition that can be used within a range of load conditions where combustion is established.

JP 2004-91657 A Paul W. Besonette, Charles H. Schleyer, Kevin P Duffy, William L. Hardy and Michael P. Liechty, “Effects of Fuel Property Changes on Heavy-Duty HCCI Combustion”, SAE Paper 2007-01-0191, 2007

Accordingly, an object of the present invention is to grasp the properties and composition required for a fuel oil composition that can be used within the range of load conditions where CAI combustion is established, and to expand the combustion range of CAI combustion to a range that cannot be achieved with conventional gasoline. It is an object of the present invention to provide a fuel composition that can be reduced and emits less CO ₂ .

  As a result of intensive studies to achieve the above object, the present inventors describe the ignitability and combustibility of CAI engine fuel, and accurately predict the range of load conditions where CAI combustion is established. We considered that the scale based on the molecular structure of the fuel that directly affects the ignition and combustion behavior is useful, and developed an evaluation index that expresses the average molecular structure of the multi-component automotive fuel. Then, CAI combustion is established by using a fuel oil composition having a specific distillation property and a newly created ignitability and anti-knock property index within a specific range for a premixed compression ignition (CAI) engine. It has been found that the operating range of the engine extends to a range that cannot be achieved with conventional automobile fuels (gasoline, light oil), and the present invention has been completed.

That is, the fuel oil composition for premixed compression ignition (CAI) engine of the present invention is
・ Sulfur content is 4 mass ppm or less,
・ 90 vol% distillation temperature is 260.0 ℃ or less,
-The following formula (1):
IQI = Ha × (−1723) + Ha × Ha × (228) + Ho × (−1988) + Ho × Ho × (3696) + Hα × (−1607) + Hα × Hα × (71) + Hβ × (−1529) + Hβ × Hβ × (41) + Hγ × (−1677) + Hγ × Hγ × (75) +1618 (1)
[In the formula, Ha is a ratio of the peak area of 9.20 to 6.20 ppm of the ¹ H-NMR spectrum of the fuel oil composition, and Ho is 6.00 to 6.00 of the ¹ H-NMR spectrum of the fuel oil composition. The ratio of the peak area of 4.20 ppm, Hα is the ratio of the peak area of 4.17 to 2.00 ppm in the ¹ H-NMR spectrum of the fuel oil composition, and Hβ is the ratio of ¹ H of the fuel oil composition. -The ratio of the peak area of 2.000 to 1.00 ppm of the NMR spectrum, and Hγ is the ratio of the area of the peak of 1.00 to 0.50 ppm of the ¹ H-NMR spectrum of the fuel oil composition, The spectral position indicates the chemical shift position from tetramethylsilane (TMS) used as the internal standard substance, and 0 ppm is the spectral position of TMS]. The ignitability index (IQI) defined by . In the following,
-The following formula (2):
AKI = Ha × (8321) + Ha × Ha × (1194) + Ho × (9818) + Ho × Ho × (4481) + Hα × (10660) + Hα × Hα × (−696) + Hβ × (9538) + Hβ × Hβ × (− 209) + Hγ × (9479) + Hγ × Hγ × (97) −9447 (2)
The antiknock index (AKI) defined by [wherein Ha, Ho, Hα, Hβ, and Hγ are as defined above] is 51.1 or more and 66.1 or less,
-The following formula (3):
CO2I = 1000 × {(16 × 2 + 12) / 12} × (C / 100) / (true calorific value)} (3)
[In the formula, C is the mass ratio (%) of carbon obtained by elemental analysis, and the true calorific value (kJ / kg) is expressed by the following formula (4):
True calorific value (kJ / kg) = 4.184 × [8100 × C / 100 + 29000 × {H / 100−O / (8 × 100)}] (4)
{In the formula, C is a mass proportion (%) of carbon obtained by elemental analysis, H is a mass proportion (%) of hydrogen obtained by elemental analysis, and O is a mass proportion (%) of oxygen obtained by elemental analysis. The CO ₂ emission basic unit (CO2I) defined by the following formula (5) is 0.069 (CO2-g / kJ) or less, and the following formula (5):
Ha / Htotal = Ha / (Ha + Ho + Hα + Hβ + Hγ) (5)
In the formula, Ha is as defined above, and Htotal is the sum of Ha, Ho, Hα, Hβ, and Hγ, and the aromaticity (Ha / Htotal) is 0.047 or more and 0.069 or less. It is characterized by being.

In the present invention, the sulfur content is measured according to JIS K2541-6, the 90% by volume distillation temperature is measured according to JIS K2254, and the ¹ H-NMR spectrum is measured by JEOL Ltd. nuclear magnetic resonance apparatus (AL-400). Measured according to type). Moreover, the said Formula (4) is an empirical formula which disregarded the sulfur content and the mass ratio (ppm) of the water | moisture content.

According to the present invention, a fuel oil composition having a specific distillation property, a small CO ₂ emission basic unit, and a newly created ignitability and combustibility index within a specific range is premixed compression ignition ( By using it in an engine, it is possible to expand the range of load conditions where CAI combustion is established to a range that cannot be achieved with conventional automobile fuels (gasoline, light oil), and contribute to CO ₂ reduction.

The present invention is described in detail below. The premixed compression ignition (CAI) engine fuel oil composition of the present invention has a sulfur content of 4 ppm by mass or less, a 90% by volume distillation temperature of 260.0 ° C. or less, and is defined by the above formula (1). The ignitability index (IQI) is 32.4 or more and 33.1 or less, and the antiknock index (AKI) defined by the above formula (2) is 51.1 or more and 66.1 or less. In addition, the premixed compression ignition (CAI) engine fuel oil composition of the present invention has a CO ₂ emission basic unit (CO2I) defined by the above formula (3) from the viewpoint of reducing CO ₂ emission during combustion. The aromaticity (Ha / Htotal) defined by the above formula (5) is 0.047 or more and 0.069 or less from the viewpoint of suppressing emission of harmful exhaust gas components at 0.069 (CO2-g / kJ) or less. It is.

As described above, the cetane number (CN) and the research octane number (RON) that have been conventionally used as indicators of fuel ignitability are not necessarily appropriate as indicators of CAI engine fuel ignitability. By the way, ignition and combustion are chemical reactions, and the present inventors considered that in a CAI engine in which a premixed gas is prepared, the chemical characteristics of the fuel, that is, the molecular structure becomes dominant. Based on this idea, the present inventors have used IQI and AKI as indices that are more useful than these as measures that represent the ignition / combustibility of multicomponent fuels that have been changed to cetane number and octane number, which have been conventionally used. Created. In the ¹ H-NMR spectrum, the peak of 9.20 to 6.20 ppm corresponds to hydrogen bonded to the aromatic ring, and the peak of 6.00 to 4.20 ppm corresponds to hydrogen bonded to carbon of a double bond. Correspondingly, the 4.17 to 2.00 ppm peak corresponds to the methylene hydrogen adjacent to the aromatic ring, the 2.000 to 1.00 ppm peak corresponds to the methylene hydrogen adjacent to the alkyl group, and 1.000 to The 0.50 ppm peak corresponds to methyl hydrogen adjacent to the alkyl group.

  And since the IQI defined by the said Formula (1) is high enough, the fuel oil composition of this invention has low enough the lower limit of the load conditions which can ensure CAI combustion. Moreover, since the fuel oil composition of the present invention has a sufficiently high AKI defined by the above formula (2), the upper limit value of the load condition that can ensure CAI combustion is sufficiently high. Therefore, the fuel oil composition of the present invention has a sufficiently high upper limit value and a sufficiently low lower limit value of load conditions that can ensure CAI combustion. , Diesel oil) can be expanded to a range that cannot be achieved, and is particularly suitable for CAI engines.

<Sulfur content>
The fuel oil composition for CAI engines of the present invention has a sulfur content of 4 ppm by mass or less, preferably 1 ppm by mass or less. Since the fuel oil composition of the present invention has a sulfur content of 10 ppm by mass or less, there are few sulfur oxides as combustion products, which can contribute to reduction of environmental burden. Further, since the sulfur content poisons the exhaust gas purification catalyst, the reduction of the sulfur content can contribute to the reduction of the environmental load through the maintenance of the performance of the exhaust gas purification catalyst. Furthermore, 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 also 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 fuel oil composition of this invention is 1 mass ppm or less.

<90 volume% distillation temperature (T90)>
The fuel oil composition for CAI engines of the present invention has a 90% by volume distillation temperature (T90) of 260.0 ° C. or lower, preferably 255.0 ° C. or lower, more preferably 250 ° C. or lower, particularly 200 It is below ℃. The volatility of the trailing portion of the fuel oil composition affects the formation of the mixture of air and the combustibility of the fuel oil composition and air, and if the 90 vol% distillation temperature (T90) exceeds 260.0 ° C, it is sufficient A premixed gas mixture cannot be obtained. In addition, if T90 is extremely high, the later fraction of the fuel adheres to the combustion chamber wall and causes dilution of the lubricating oil. Therefore, T90 is 260.0 ° C. or lower. Further, although not particularly limited, the fuel oil composition of the present invention has a 90 vol% distillation temperature (T90) of 120 ° C or higher from the viewpoint of maintaining the cleanliness of the intake valve and the injection nozzle. Is preferred.

<Ignition index (IQI)>
In the fuel oil composition for a CAI engine of the present invention, the IQI defined by the above formula (1) that affects the lower limit of the load condition that can ensure CAI combustion is 32.4 or more and 33.1 or less . In order to improve the ignitability of the fuel, measures such as an improvement in the compression ratio are taken on the engine side. However, in order to ensure reliable ignition of the fuel and stability of combustion, the IQI of the fuel itself is set to 32.4. That's it .

<Antiknock index (AKI)>
The CAI engine fuel oil composition of the present invention has an AKI defined by the above formula (2) that affects the upper limit of the load condition that can ensure CAI combustion, and is preferably 51.1 or more and 66.1 or less , preferably It is 54 or more and 66.1 or less , More preferably, it is 60 or more and 66.1 or less . To ensure slow combustion to avoid damage to the increase and the engine noise and NOx caused by the rapid combustion at high load conditions, and the AKI 51.1 or more. In order to avoid rapid combustion, in the engine-side Although measures such as the introduction of the exhaust gas recirculation system (EGR) are taken, in order to expand the high-load operation region, the AKI and 51.1 or more , 54 or more .

<CO ₂ emission intensity (CO2I)>
In the fuel oil composition for a CAI engine of the present invention, CO2I defined by the above formula (3) is 0.069 (CO2-g / kJ) or less. In order to reduce the CO ₂ emitted from the engine, a fuel having a small amount of CO ₂ emission per unit calorific value of the fuel is required, and CO _{2 I} is 0.069 (CO 2 -g / kJ) or less .

<Aromaticity (Ha / Htotal)>
In the fuel oil composition for a CAI engine of the present invention, the Ha / Htotal defined by the above formula (5) is 0.047 or more and 0.069 or less . When Ha / Htotal increases, more hydrogen is bonded to the aromatic ring, leading to an increase in harmful exhaust gas, so Ha / Htotal is 0.069 or less . In particular, since NOx and CO are affected by Ha / Htotal, Ha / Htotal is 0.069 or less .

<Preparation of fuel oil composition>
The fuel oil composition for a CAI engine of the present invention can be prepared from a saturated hydrogenated fuel of a petroleum naphtha, a catalytic cracked gasoline base and a catalytic reformed gasoline base so as to satisfy the above properties.

<Additives>
An antioxidant for ensuring the stability of the fuel oil composition, a detergent for ensuring the cleanliness of the engine, and the like can be appropriately added to the fuel oil composition for the CAI engine of the present invention.

  Examples of the antioxidant include 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,4-dimethyl-6-t-butylphenol, 2,4,6- Phenolic antioxidants such as tri-t-butylphenol, 2-t-butyl-4,6-dimethylphenol, 2-t-butylphenol, N, N'-diisopropyl-p-phenylenediamine, N, N'- Examples thereof include amine-based antioxidants such as di-sec-butyl-p-phenylenediamine, and mixtures thereof. The addition amount of these antioxidants is preferably in the range of 0.05 to 1% by mass.

  Examples of the detergent include succinimide, polyalkylamine, and polyetheramine. The addition amount of these detergents is not particularly limited, and can be appropriately selected according to the purpose.

<Premixed compression ignition engine>
The fuel oil composition of the present invention described above is used in a premixed compression ignition (CAI) engine. The CAI engine is also called an HCCI (Homogeneous Charge Compression Ignition) engine, which is compression ignition like a conventional diesel engine, but fuel injection timing, fuel injection pressure and injection pattern, EGR, compression ratio, combustion chamber structure, etc. Is a combustion system that completes combustion only by a premixed flame formed by combustion of a premixed gas in which fuel and air are sufficiently mixed. Therefore, when the heat generation pattern is observed, one heat generation peak due to the premixed flame as the main combustion is observed following the weak heat generation (although it may not be observed) accompanying the cold flame. Conventional diesel combustion is greatly different in that two peaks associated with premixed flame and diffusion flame are observed. Further, unlike a gasoline engine in which combustion is completed by propagation of a premixed flame, it has a feature of high efficiency.

  And, by using the above-described fuel oil composition of the present invention for such a premixed compression self-ignition (CAI) engine, there is no range of load conditions that can ensure CAI combustion with conventional automobile fuels (gasoline, light oil). Since it can be expanded to a range that can not be obtained, it improves the fuel efficiency of automobiles while reducing harmful exhaust gas components such as nitrogen oxides (NOx) and particulate matter (PM) compared to the case of using conventional automobile fuel be able to.

  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.

Properties of the following test fuels were analyzed by the following method.
<Preparation of test fuel>
-RG: Commercial regular gasoline was prepared.
RFG: octane number obtained by reacting heavy naphtha with a solid catalyst using a moving bed reactor to reform to a hydrocarbon with high aromatic content and distilling and separating the pentane fraction and below. Of gasoline was used.
ALK: An alkylate gasoline having an octane number of 95.5 obtained by isomerizing by a sulfuric acid catalytic method using butylene distilled from a fluid catalytic cracking unit and butane distilled from an atmospheric distillation unit as raw material oil Was used.
・ GTL: FT synthesized paraffinic fuel purchased as moss gas from Jomosan Energy Co., Ltd. ・ Fuel-1: Contact with naphtha produced by hydrorefining light gasoline obtained by atmospheric distillation of crude oil Reformation was carried out, and the obtained catalytically reformed gasoline base material was mixed with 50% by volume of fuel obtained by converting the total amount of naphthenic components by hydrogenation, and 50% by volume of RG.
・ Fuel-2: Middle East crude oil was separated into boiling points of 170-360 ° C by atmospheric distillation, hydrodesulfurized, and further extracted at 280 ° C or higher by precision distillation, 50% by volume, RG 50% by volume Mixed.

<Fuel property analysis method>
・ Density: JIS K2249 “Crude oil and petroleum product density test method”
・ Distillation properties: JIS K2254 "Distillation test method"
・ Sulfur content: JIS K2541-6 “Sulfur content test method (ultraviolet fluorescence method)”
-Cetane number (CN): Measured method defined in JIS K2280 "Petroleum products-Fuel oil-Octane number and cetane number test method and cetane index calculation method" (index is not applicable)
-Research octane number (RON): JIS K2280 "Petroleum products-Fuel oil-Octane number and cetane number test method and cetane index calculation method"
・¹ H-NMR spectrum was measured according to a nuclear magnetic resonance apparatus (AL-400 type) manufactured by JEOL Ltd. ・ Carbon mass ratio: measured by elemental analysis ・ True calorific value: Carbon mass ratio determined by elemental analysis, Calculated according to the above formula (4) using the mass proportion of hydrogen and the mass proportion of oxygen

<Evaluation of test fuel>
Using a single-cylinder engine with a displacement of 1.8 (L), the CAI combustion range of each of the above-mentioned fuels was relatively evaluated as compared to commercially available gasoline (RG). The low load limit of CAI combustion was determined by the stability of ignition, and the high load limit was determined by the maximum value of the heat generation rate. RFG and ALK show a CAI combustion range almost equivalent to RG, but GTL has a smaller AKI and a higher high load limit than RG. On the other hand, the mixture of hydrogenated RFG and RG (fuel-1) and the mixture of light gas oil and RG (fuel-2) have moderate IQI and AKI, so the CAI combustion range is wider than RG. ing. Table 1 shows that the CAI combustion range based on RG is equivalent to RG, ◯ when wider than RG, × when narrower than RG, Δ / △ when RG is equivalent to both upper and lower limits, RG The case where the upper limit is the same and the lower limit is narrow is indicated by Δ / x.

  As is apparent from Table 1, the fuel composition satisfying the properties defined in the present invention can expand the CAI combustion range as compared with commercially available gasoline.

Claims (1)

Sulfur content is 4 mass ppm or less, 90 vol% distillation temperature is 260.0 ° C or less,
Following formula (1):
IQI = Ha × (−1723) + Ha × Ha × (228) + Ho × (−1988) + Ho × Ho × (3696) + Hα × (−1607) + Hα × Hα × (71) + Hβ × (−1529) + Hβ × Hβ × (41) + Hγ × (−1677) + Hγ × Hγ × (75) +1618 (1)
[In the formula, Ha is a ratio of the peak area of 9.20 to 6.20 ppm of the ¹ H-NMR spectrum of the fuel oil composition, and Ho is 6.00 to 6.00 of the ¹ H-NMR spectrum of the fuel oil composition. The ratio of the peak area of 4.20 ppm, Hα is the ratio of the peak area of 4.17 to 2.00 ppm in the ¹ H-NMR spectrum of the fuel oil composition, and Hβ is the ratio of ¹ H of the fuel oil composition. -The ratio of the peak area of 2.000 to 1.00 ppm of the NMR spectrum, and Hγ is the ratio of the area of the peak of 1.00 to 0.50 ppm of the ¹ H-NMR spectrum of the fuel oil composition, The spectral position indicates the chemical shift position from tetramethylsilane (TMS) used as the internal standard substance, and 0 ppm is the spectral position of TMS]. The ignitability index (IQI) defined by . In the following,
Following formula (2):
AKI = Ha × (8321) + Ha × Ha × (1194) + Ho × (9818) + Ho × Ho × (4481) + Hα × (10660) + Hα × Hα × (−696) + Hβ × (9538) + Hβ × Hβ × (− 209) + Hγ × (9479) + Hγ × Hγ × (97) −9447 (2)
The antiknock index (AKI) defined by [wherein Ha, Ho, Hα, Hβ, and Hγ are as defined above] is 51.1 or more and 66.1 or less,
Following formula (3):
CO2I = 1000 × {(16 × 2 + 12) / 12} × (C / 100) / (true calorific value)} (3)
[In the formula, C is the mass ratio (%) of carbon obtained by elemental analysis, and the true calorific value (kJ / kg) is expressed by the following formula (4):
True calorific value (kJ / kg) = 4.184 × [8100 × C / 100 + 29000 × {H / 100−O / (8 × 100)}] (4)
{In the formula, C is a mass proportion (%) of carbon obtained by elemental analysis, H is a mass proportion (%) of hydrogen obtained by elemental analysis, and O is a mass proportion (%) of oxygen obtained by elemental analysis. The CO ₂ emission basic unit (CO2I) defined by the formula (5) is 0.069 (CO 2 -g / kJ) or less and the following formula (5):
Ha / Htotal = Ha / (Ha + Ho + Hα + Hβ + Hγ) (5)
In the formula, Ha is as defined above, and Htotal is the sum of Ha, Ho, Hα, Hβ, and Hγ, and the aromaticity (Ha / Htotal) is 0.047 or more and 0.069 or less. A fuel oil composition for a premixed compression ignition engine, characterized by comprising: