JP2009167405A - Fuel oil composition for premixed compressed ignition engine, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel oil composition for a premixed compressed ignition engine, capable of expanding the range of loading condition for establishing PCCI (premixed charge compression ignition) combustion to a range which conventional automobile fuels such as gasoline, light oil, or the like, cannot achieve. <P>SOLUTION: In the fuel oil composition for the premixed compressed ignition engine, a sulfur content is ≤10 mass ppm, the temperature of 90 vol.% distillation is ≤165°C, a cetane number (CN) is ≥12, a research method octane number (RON) is ≥80, and the sum of the cetane number and research method octane number (CN+RON) is ≥100. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel oil composition for a premixed compression ignition engine and a method for producing the same, and in particular, when used in a premixed compression ignition engine, the range of load conditions that can ensure premixed compression ignition combustion is The present invention relates to a fuel oil composition that can be expanded to a range that cannot be achieved with conventional automobile fuels such as oil and diesel oil.

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 reduction of CO ₂ emission. Recently, premixed compression ignition (PCCI) engine has attracted attention as a corresponding technology. Has been.

  In the PCCI engine, since the start (ignition) of combustion depends on the self-ignition of fuel, 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 rapid combustion due to multi-point 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. Therefore, under high load conditions where the temperature in the combustion chamber is high, a fuel with low ignitability, that is, a fuel exhibiting slow combustion behavior is required. Therefore, as a fuel for PCCI engines, a fuel having a high cetane number (CN), which is an index of ignitability under low load conditions, and a high research octane number (RON) capable of expecting slow combustion under high load conditions is desirable.

  More specifically, since the presence or absence of premixed compression ignition (PCCI) combustion under low load conditions is defined by the cetane number (CN) of the fuel, the lower limit value of the load condition that can ensure stable ignition and combustion is Depends greatly on the cetane number (CN) of the fuel. On the other hand, since the existence of PCCI combustion under high load conditions is defined by the fuel research method octane number (RON), the upper limit of the load condition that can ensure slow combustion is the fuel research method octane number (RON) Depends heavily on Therefore, the range of the load condition in which PCCI combustion is established greatly depends on both the cetane number (CN) and the research octane number (RON) of the fuel.

  Under engine load conditions where PCCI combustion is not established, the conventional combustion mode (gasoline combustion or diesel engine combustion) will be used, but there is a range of PCCI combustion that can simultaneously achieve reduction of harmful emissions and improvement of fuel consumption. Since the wider the engine performance is, the higher the cetane number (CN) and the research octane number (RON) fuel are demanded.

JP 2004-91657 A Daisei, “Future Perspectives on Diesel Engine Technology”, Automotive Technology, Vol.59, No.4 (2005)

  However, the relationship between the hydrocarbon cetane number (CN) and the research octane number (RON) is a trade-off, and fuel with a high cetane number (CN) is found to have a low research octane number (RON). Yes.

  Therefore, an object of the present invention is to balance the range of load conditions where PCCI combustion is established by balancing both the cetane number (CN) and the research octane number (RON) to the optimum values, and to achieve conventional automobiles such as gasoline and light oil. It is an object of the present invention to provide a fuel oil composition for a premixed compression ignition engine that can be expanded to a range that cannot be achieved with a fuel for industrial use.

  As a result of intensive studies to achieve the above object, the present inventors have preliminarily obtained a fuel oil composition having a specific distillation property and having a cetane number (CN) and a research octane number (RON) in a specific range. By using it for a mixed compression ignition engine, it has been found that the range of load conditions for establishing PCCI combustion is expanded to a range that cannot be achieved by conventional automobile fuels (gasoline, light oil), and the present invention has been completed. .

That is, the fuel oil composition for the premixed compression ignition engine of the present invention is
・ The sulfur content is 10 mass ppm or less,
・ 90 vol% distillation temperature is 165 ℃ or less,
-The cetane number (CN) is 12 or more,
・ Research octane number (RON) is 80 or more,
-The sum of the cetane number and the research octane number (CN + RON) is 100 or more.

  The method for producing a fuel oil composition for a premixed compression ignition engine according to the present invention is characterized in that the fuel oil 1 is mixed with the fuel oil 2 having a research octane number (RON) lower than that of the fuel oil 1 by 10 or more. And

  In the present invention, the sulfur content is measured according to JIS K2541-6, the 90 vol% distillation temperature is measured according to JIS K2254, and the cetane number (CN) and the research octane number (RON) are measured according to JIS K2280.

  According to the present invention, by using a fuel oil composition having a specific distillation property and having a cetane number (CN) and a research octane number (RON) in a specific range for a premixed compression ignition engine, It is possible to expand the range of the load conditions that are satisfied to a range that cannot be achieved with conventional automobile fuels (gasoline, light oil).

  The present invention is described in detail below. The fuel oil composition for premixed compression ignition engines of the present invention has a sulfur content of 10 mass ppm or less, a 90% by volume distillation temperature of 165 ° C. or less, a cetane number (CN) of 12 or more, a research octane number ( (RON) is 80 or more, and the sum of cetane number and research octane number (CN + RON) is 100 or more. Since the fuel oil composition of the present invention has a sufficiently high cetane number (CN), the lower limit of the load condition that can ensure PCCI combustion is sufficiently low. In addition, since the fuel oil composition of the present invention has a sufficiently high research octane number (RON), the upper limit value of the load condition that can ensure PCCI combustion is sufficiently high. Furthermore, since the fuel oil composition of the present invention has a sufficiently high sum of cetane number and research octane number (CN + RON), the range of load conditions that can ensure PCCI combustion is wide, and conventional automobile fuels (gasoline, light oil) Thus, the range of load conditions where PCCI combustion is established can be expanded to a range that cannot be achieved, which is particularly suitable for a premixed compression ignition engine.

<Sulfur content>
The fuel oil composition for PCCI engines of the present invention has a sulfur content of 10 ppm by mass or less, preferably 2 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 a reduction in 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 2 mass ppm or less.

<90 volume% distillation temperature (T90)>
The fuel oil composition for PCCI engines of the present invention has a 90% by volume distillation temperature (T90) of 165 ° C. or lower, preferably 163 ° C. or lower, more preferably 160 ° C. or lower, particularly 150 ° C. or lower. If the 90% by volume distillation temperature (T90) exceeds 165 ° C., the amount of particulate matter (PM) discharged increases and the environmental load cannot be reduced sufficiently. Further, the volatility of the rear fraction portion of the fuel oil composition affects the formation and combustion properties of the mixture of the fuel oil composition and air. This may hinder the formation of an air-fuel mixture of the fuel oil composition and air, or the combustibility of the air-fuel mixture may be reduced. In order to cope with the above problem, since the 90% by volume distillation temperature (T90) is preferably as low as possible, the fuel oil composition of the present invention has a 90% by volume distillation temperature (T90) of 163 ° C. or lower. Preferably, it is 160 degrees C or less, and it is especially preferable that it is 150 degrees C or less. 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. It is preferable.

<Cetane number (CN)>
The fuel oil composition for PCCI engines of the present invention has a cetane number (CN) that affects the lower limit of the load condition that can ensure PCCI combustion is 12 or more, preferably 14 to 40. In order to improve the ignitability of the fuel oil, measures such as improving the compression ratio are taken on the engine side. However, in order to ensure reliable ignition of the fuel oil and stability of combustion, the cetane of the fuel oil itself is used. The valence (CN) must be 12 or more, preferably 14 or more. If the cetane number (CN) of the fuel oil is too high, the time from fuel oil injection to ignition, that is, the ignition delay is shortened, so the time allowed for the formation of the air-fuel mixture is shortened, It is preferable that the cetane number (CN) of the fuel oil composition is 40 or less because the engine performance is deteriorated due to excessive advance of the ignition timing due to early ignition.

<Research Method Octane Number (RON)>
The fuel oil composition for PCCI engines of the present invention has a research octane number (RON) of 80 or more, preferably 81 or more, more preferably 85 or more, which affects the upper limit of the load conditions that can ensure PCCI combustion. . In order to ensure slow combustion under high load conditions, it is necessary to set the research octane number (RON) of the fuel oil composition to 80 or more. In order to avoid premature ignition and rapid combustion, measures such as the introduction of an exhaust gas recirculation system (EGR) are taken on the engine side, but noise and combustion pressure that are acceptable as PCCI combustion under high load conditions. In order to ensure the rate of increase, the research octane number (RON) of the fuel oil composition needs to be 80 or more, preferably 81 or more, more preferably 85 or more.

<CN + RON>
In the PCCI engine fuel oil composition of the present invention, the sum of the cetane number (CN) and the research octane number (RON) (CN + RON) is 100 or more, preferably 101 or more, more preferably 103 or more. In order to secure an appropriate PCCI combustion range, it is necessary to keep each of the cetane number (CN) and the research octane number (RON) appropriately, and to make the sum of both (CN + RON) 100 or more, Preferably it is 101 or more, More preferably, it is 103 or more.

<Preparation of fuel oil composition>
The fuel oil composition for a PCCI engine of the present invention can be produced by mixing fuel oil 1 with fuel oil 2 having a research octane number (RON) 10 or less lower than that of fuel oil 1 so as to satisfy the above properties. . For example, the fuel oil composition for a PCCI engine of the present invention comprises both a commercially available premium gasoline having a high octane number, an aromatic base material or isoparaffin, and a naphtha having a low octane number, a commercially available normal paraffin, or a gasoline base containing a large amount of paraffin. It can be prepared by mixing appropriately. The volume ratio of the fuel oil 1 and the fuel oil 2 (fuel oil 1 / fuel oil 2) may be adjusted as appropriate so as to satisfy the above-mentioned properties. For example, a range of 80/20 to 20/80 is preferable. .

<Additives>
In order to improve the above-mentioned cetane number (CN), the cetane number improver can be mix | blended with the fuel oil composition for PCCI engines of this invention. Examples of the cetane number improver include alkyl nitrate cetane number improvers and organic peroxide cetane number improvers. As said alkyl nitrate type | system | group cetane improver, a C6-C12 alkyl nitrate is preferable and 2-methylhexyl nitrate is especially preferable. Moreover, as said organic peroxide type | system | group cetane number improver, a C6-C12 dialkyl peroxide is preferable and di-t-butyl peroxide is especially preferable. The addition amount of these cetane number improvers is preferably in the range of 0.05 to 1% by mass.

  Further, the PCCI engine fuel oil composition of the present invention includes, as other additives, an antioxidant for ensuring the stability of the fuel oil composition, and a low temperature fluidity improver for ensuring low temperature fluidity. Further, a lubricity improver for ensuring lubricity, a detergent for ensuring engine cleanliness, and the like can be appropriately added.

  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.

  As the low-temperature fluidity improver, known ethylene copolymers and the like can be used. In particular, vinyl esters of saturated fatty acids such as vinyl acetate, vinyl propionate and vinyl butyrate are preferably used. The addition amount of these low temperature fluidity improvers is not particularly limited, and can be appropriately selected according to the purpose.

  As the above-mentioned lubricity improver, for example, a long chain (for example, having 12 to 24 carbon atoms) fatty acid or a fatty acid ester thereof is preferably used. By adding the lubricity improver in the range of 10 to 500 ppm by mass, preferably in the range of 50 to 300 ppm by mass, the wear resistance can be sufficiently improved.

  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 (PCCI) engine. The PCCI 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 that is the main combustion is observed following the weak heat generation accompanying the cold flame (which may not be observed). Conventional diesel combustion is greatly different in that two peaks associated with premixed flame and diffusion flame are observed. It is also different from a gasoline engine where combustion is completed by propagation of a premixed flame. In an actual PCCI engine, tailing of the heat generation pattern may be observed, but the cause (whether premixed flame or diffusion flame) is not clear, so the main combustion in the PCCI engine is 90% or more (tailing). The heat generation associated with is less than 10%). Further, the PCCI engine has a feature that it is more efficient than a gasoline engine (spark ignition type engine) because it can be operated at a high compression ratio.

  And, by using the above-described fuel oil composition of the present invention for such a premixed compression ignition engine, the range of load conditions that can ensure PCCI combustion is in a range that cannot be achieved with conventional automotive fuels (gasoline, light oil). Since it can be expanded, it is possible to improve the fuel efficiency of the automobile while reducing harmful exhaust gas components such as nitrogen oxides (NOx) and particulate matter (PM) as compared with the case of using conventional automobile fuel.

  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.
-ADO: Commercially available light oil (JIS No. 2) was prepared.
-KERO: Commercial kerosene was prepared.
-GTL: Moss gas products were purchased through JOMO Sun Energy.
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. The catalytic reforming gasoline was used.
ALK: Butylene distilled from fluid catalytic cracking gasoline and butane distilled from atmospheric distillation equipment are used as raw material oils and isomerized by sulfuric acid contact method to obtain an alkylate gasoline with an octane number of 95.5 Was used.
LN: Light naphtha having an octane number of 60 obtained by hydrodesulfurizing naphtha obtained by distilling Middle Eastern crude oil to 140 ° C. or lower with an atmospheric distillation apparatus and further distilling to 90 ° C. or lower was used.
Fuel-1: Prepared by mixing equal amounts of 50% by volume of RFG [RON = 106] and LN [RON = 60].
Fuel-2: Prepared by mixing 25% by volume of LN [RON = 60] with 75% by volume of ALK [RON = 95.5].

<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"

  As is apparent from Table 1, the fuel oil composition satisfying the properties defined in the present invention has a higher octane number than Comparative Examples 2, 3 and 4 in order to increase the upper limit value of the load condition. In order to lower the lower limit value, the cetane number is higher than that of Comparative Example 1, and further, CN + RON is higher than that of Comparative Examples 1, 2, 3, and 4, and the range of load conditions for establishing PCCI combustion is expanded. It is the most suitable fuel composition.

Claims (2)

  The sulfur content is 10 mass ppm or less, the 90% by volume distillation temperature is 165 ° C. or less, the cetane number (CN) is 12 or more, the research octane number (RON) is 80 or more, and the cetane number and the research method octane number A fuel oil composition for a premixed compression ignition engine, wherein the sum (CN + RON) is 100 or more.   2. The fuel oil composition for a premixed compression ignition engine according to claim 1, wherein the fuel oil 1 is mixed with a fuel oil 2 having a research octane number (RON) lower than that of the fuel oil 1 by 10 or more. Method.