JP2024098588A - Fuel oil composition - Google Patents

Abstract

The present invention provides a fuel oil composition that contains a fatty acid alkyl ester and thus has excellent combustion performance and room temperature oil passing performance.
[Solution] The fuel oil composition contains a fatty acid alkyl ester and a cracked light oil fraction having specific properties in amounts of 15.0 to 35.0 vol.% and 20.0 to 40.0 vol.%, respectively, based on the total amount of the composition, and satisfies all of the following: (1) a density at 15°C of 0.8700 to ^0.8900 g/ ^cm3 , (2) a kinetic viscosity at 50°C of ^2.000 to 4.500 ^mm2 /s, (3) a sulfur content of 0.400 mass% or less, (4) a content of aromatics with 3 or more rings of 2.9 vol.% or more, and (5) a residual carbon content of 0.21 mass% to 0.60 mass% in 10% residual oil.
[Selection diagram] None

Description

The present invention relates to a fuel oil composition.

JIS K2205:1991 Class 1 heavy oil (hereinafter also referred to as "A heavy oil"), especially JIS K2205:1991 Class 1 No. 1 heavy oil (hereinafter also referred to as "low-sulfur A heavy oil"), has a higher calorific value per unit volume than kerosene, light oil, etc., and can reduce the amount (volume) of fuel oil used. It also has less sulfur, nitrogen, and residual carbon than C heavy oil (JIS K2205:1991 Class 3 heavy oil), so it has a smaller environmental impact. Furthermore, unlike C heavy oil, it does not need to be heated, can be stored and used at room temperature, and has excellent supply stability, so it is widely used as a fuel oil for internal combustion engines such as marine diesel engines and as a fuel oil for external combustion engines such as power generation boilers.

As fuel oils for ships, fuel oils that satisfy ISO8217 "Petroleum products-Fuels (class F)-Specification of marine fuels" are known. In ISO8217:2017, additional regulations (DF grades: DFA, DFZ and DFB) were added for marine distillate oils with a maximum content of fatty acid methyl esters (FAME) of 7% by volume or less. As fuel oil compositions containing fatty acid methyl esters (FAME), compositions described in Patent Documents 1 to 3 are known. Patent Documents 1 to 3 disclose internal combustion engine fuel oil compositions and external combustion engine fuel oil compositions that contain 5 to 100% by volume of a methyl ester of rapeseed oil containing fatty acid methyl esters such as methyl myristic acid ester.

JP 2007-231119 A JP 2007-231120 A JP 2007-231121 A

Fatty acid alkyl esters such as fatty acid methyl esters (FAME) contained in the fuel oil compositions described in Patent Documents 1 to 3 have high combustion performance and are one of the base oils that are being considered for use as fuel oils. In addition, when fatty acid alkyl esters derived from animals and plants are used, carbon dioxide emissions are reduced, which contributes to the suppression of global warming by reducing carbon dioxide emissions, and is extremely useful from the perspective of environmental protection. Therefore, by using fatty acid alkyl esters such as fatty acid methyl esters (FAME) as base oils, improved combustion performance can be expected, and furthermore, when fatty acid alkyl esters derived from animals and plants are used, they can become base oils that contribute to environmental protection.

However, when fuel oil compositions are used in ships, particularly in diesel engines on ships, the frequency of blockage of fuel oil filters is likely to increase due to the generation of sludge caused by the aggregation of asphaltene during normal use. Furthermore, when the fuel oil composition is used after long-term storage in a fuel oil tank on the ship, sludge is more likely to be generated, and the frequency of blockage tends to increase.

Although fuel oils that satisfy the above-mentioned ISO 8217 are known as fuel oil compositions for ships, they may cause clogging of fuel oil filters. Known methods for reducing the frequency of clogging include a method of reducing potential sediment (total sediment aged, ISO 10307-2) to 0.10 mass% or less, and a method of reducing actual sediment (total sediment by hot filtration, ISO 10307-1) to 0.10 mass% or less. However, for fuel oils for ships, particularly distillate oils, the oil passing performance through fuel oil filters after storage at room temperature is not sufficient, and a fuel oil composition that can further reduce the frequency of clogging is required.

In Japan, it is known that the Japan Fisheries Federation's fuel oil standard for fishing boats requires that the water content and dry sludge content be below a certain level in order to reduce the frequency of blockages in heavy oil A for fishing boats. Thus, marine fuel oil compositions used both at home and abroad are required to further reduce the frequency of blockages, and requirements regarding oil passing performance are becoming stricter every year.

The fuel oil compositions described in the above Patent Documents 1 to 3 focus on reducing unburned substances (smoke) and particulate matter (PM) in exhaust gas, improving heat generation and reducing soot concentration in combustion exhaust gas, as well as reducing sulfur content and improving sludge stability due to the incorporation of a carbon residue imparting agent. However, attention is not paid not only to improving combustion performance but also to improving oil permeability by reducing the frequency of blockages, and there is room for improvement, especially in terms of oil permeability. In addition, ISO 8217 sets standards for ship distillate oils with a fatty acid methyl ester (FAME) content of 7% by volume or less, but does not mention low-sulfur A heavy oil with a fatty acid alkyl ester content of more than 7% by volume. Low-sulfur A heavy oil with a fatty acid methyl ester (FAME) and other fatty acid alkyl ester content of more than 7% by volume is prone to blockage of fuel oil filters when used after storage at room temperature, and cannot be said to be excellent in terms of oil permeability through fuel oil filters (hereinafter also referred to as "room temperature oil permeability"). Therefore, further improvements are needed to improve fuel oil filter performance by reducing the frequency of blockages in fuel oil filters when used after storage at room temperature.

The present invention was made in consideration of these circumstances, and aims to provide a fuel oil composition that contains a fatty acid alkyl ester and thus has excellent combustion performance and also room temperature oil passing performance.

As a result of intensive research into the above-mentioned problems, the present inventors have found that the problems can be solved by the following invention. That is, the present invention provides a fuel oil composition having the following composition.

[1] A fuel oil composition comprising a fatty acid alkyl ester satisfying all of the following ( _a1 ) to ( _a3 ) and a cracked light oil fraction satisfying all of the following ( _b1 ) to ( _b4 ), wherein the fatty acid alkyl ester is an ester of a fatty acid having from 8 to 22 carbon atoms and an alkyl alcohol having from 1 to 4 carbon atoms, the content of the fatty acid alkyl ester is from 15.0 to 35.0 vol. % based on the total volume of the composition, and the content of the cracked light oil fraction is from 20.0 to 40.0 vol. % based on the total volume of the composition, and the composition satisfies all of the following (1) to (5):
( _a1 ) Cetane number is 49.0 or more; ( _a2 ) Acid number is 0.50 mgKOH/g or less; ( _a3 ) Residual carbon content of 10% residual oil is 0.80 mass% or more and 1.50 mass% or less; ( _b1 ) Kinematic viscosity at 50°C is 1.700 ^mm2 /s or more and 3.600 ^mm2 /s or less; ( _b2 ) Sulfur content is 0.40 mass% or less; ( _b3 ) Aromatic content is 50.0 vol% or more; ( _b4 ) 3 or more ring aromatic content is 5.0 vol% or more; (1) Density at 15°C is 0.8700 g/cm3 ^or more and 0.8900 g/cm3 ^or less; (2) Kinematic viscosity at 50°C is 2.000 ^mm2 /s or more and 4.500 ^mm2 /s or more; (3) a sulfur content of 0.400 mass% or less; (4) a content of aromatics with 3 or more rings of 2.9 volume% or more; and (5) a residual carbon content of 10% residual oil of 0.21 mass% or more and 0.60 mass% or less. [2] The fuel oil composition according to the above [1], wherein the fatty acid alkyl ester is a fatty acid methyl ester.
[3] The fuel oil composition according to the above [1] or [2], wherein the fatty acid is a mixed fatty acid containing two or more kinds of fatty acids having from 8 to 22 carbon atoms.
[4] The fuel oil composition according to the above [3], wherein the mixed fatty acid is obtained from at least one raw material selected from animal oils and vegetable oils.
[5] The fuel oil composition according to the above [4], wherein the raw material is waste edible oil.
[6] The fuel oil composition according to any one of the above [1] to [5], which is used in an internal combustion engine.
[7] A method for producing a fuel oil composition which satisfies all of the following ( ₁ ) to ( ₅ ), comprising mixing a fatty acid alkyl ester which is an ester of a fatty acid having from 8 to 22 carbon atoms and an alkyl alcohol having from 1 to ₄ carbon atoms and which satisfies all of the following (a1) to (a3) with a cracked light oil fraction which satisfies all of the following ( _b1 ) to (b4) so that the content of the fatty acid alkyl ester is from 15.0 to 35.0 vol. % based on the total volume of the composition, and the content of the cracked light oil fraction is from 20.0 to 40.0 vol. % based on the total volume of the composition.
( _a1 ) Cetane number is 49.0 or more; ( _a2 ) Acid number is 0.50 mgKOH/g or less; ( _a3 ) Residual carbon content of 10% residual oil is 0.80 mass% or more and 1.50 mass% or less; ( _b1 ) Kinematic viscosity at 50°C is 1.700 ^mm2 /s or more and 3.600 ^mm2 /s or less; ( _b2 ) Sulfur content is 0.40 mass% or less; ( _b3 ) Aromatic content is 50.0 vol% or more; ( _b4 ) 3 or more ring aromatic content is 5.0 vol% or more; (1) Density at 15°C is 0.8700 g/cm3 ^or more and 0.8900 g/cm3 ^or less; (2) Kinematic viscosity at 50°C is 2.000 ^mm2 /s or more and 4.500 ^mm2 /s or more; (3) Sulfur content is 0.400 mass% or less; (4) Three or more ring aromatic content is 2.9 volume% or more; (5) Residual carbon content of 10% residual oil is 0.21 mass% or more and 0.60 mass% or less.

The present invention provides a fuel oil composition that contains a fatty acid alkyl ester and thus has excellent combustion performance and room temperature oil passing performance.

The fuel oil composition according to an embodiment of the present invention (hereinafter, sometimes simply referred to as "this embodiment") will be specifically described below. Note that in this specification, the numerical values of "less than," "greater than," and "to" in describing a numerical range are numerical values that can be arbitrarily combined. For example, when a certain numerical range is described as "A to B" and "C to D," the numerical ranges "A to D" and "C to B" are also included. The numerical values in the examples are numerical values that can be used as upper or lower limits.

[Fuel oil composition]
The fuel oil composition of this embodiment comprises a fatty acid alkyl ester that satisfies all of the following ( _a1 ) to ( _a3 ) and a cracked light oil fraction that satisfies all of the following ( _b1 ) to ( _b4 ), wherein the fatty acid alkyl ester is an ester of a fatty acid having from 8 to 22 carbon atoms and an alkyl alcohol having from 1 to 4 carbon atoms, the content of the fatty acid alkyl ester is from 15.0% to 35.0% by volume based on the total amount of the composition, and the content of the cracked light oil fraction is from 20.0% to 40.0% by volume based on the total amount of the composition, and the fuel oil composition satisfies all of the following (1) to (5).
( _a1 ) Cetane number is 49.0 or more; ( _a2 ) Acid number is 0.50 mgKOH/g or less; ( _a3 ) Residual carbon content of 10% residual oil is 0.80 mass% or more and 1.50 mass% or less; ( _b1 ) Kinematic viscosity at 50°C is 1.700 ^mm2 /s or more and 3.600 ^mm2 /s or less; ( _b2 ) Sulfur content is 0.40 mass% or less; ( _b3 ) Aromatic content is 50.0 vol% or more; ( _b4 ) 3 or more ring aromatic content is 5.0 vol% or more; (1) Density at 15°C is 0.8700 g/cm3 ^or more and 0.8900 g/cm3 ^or less; (2) Kinematic viscosity at 50°C is 2.000 ^mm2 /s or more and 4.500 ^mm2 /s or more; (3) Sulfur content is 0.400 mass% or less; (4) Three or more ring aromatic content is 2.9 volume% or more; (5) Residual carbon content of 10% residual oil is 0.21 mass% or more and 0.60 mass% or less.

(Composition and properties of fuel oil composition)
The fuel oil composition of this embodiment satisfies the composition and properties specified in the following (1) to (5).
(1) Density at 15° C. The density at 15° C. of the fuel oil composition of this embodiment is 0.8700 g/cm ³ or more and 0.8900 g/cm ³ or less. If the density at 15° C. is not within the above range, deterioration of combustion performance and decrease in total calorific value may occur.

From the viewpoint of improving room temperature oil passing performance and combustion performance, and further improving the total calorific value, the density at 15°C of the fuel oil composition of this embodiment is preferably 0.8740 g/ ^cm3 or more, more preferably 0.8750 g/ ^cm3 or more, and even more preferably 0.8770 g/ ^cm3 or more, and the upper limit is preferably 0.8880 g/ ^cm3 or less, more preferably 0.8850 g/ ^cm3 or less, and even more preferably 0.8830 g/ ^cm3 or less.
In this specification, the density at 15°C is a value measured in accordance with JIS K 2249-1:2011 (Crude oil and petroleum products-Determination of density-Part 1: Vibration method).

(2) Kinematic Viscosity at 50° C. The kinematic viscosity of the fuel oil composition of this embodiment at 50° C. is 2.000 mm ² /s or more and 4.500 mm ² /s or less. If the kinematic viscosity at 50° C. is not within the above range, the combustion performance may be reduced. In addition, it may become difficult to conform to the range of use of various devices such as pumps and flow meters, and lubricity may not be ensured, making it impossible to use as a fuel oil composition.

By making it easier to set the kinetic viscosity at 50°C of the fuel oil composition of this embodiment within the above range, it is possible to improve combustion performance, make it easier to adapt to the range of use of various equipment, and improve lubricity. From the viewpoint of this, the kinetic viscosity at 50°C is preferably 2.800 ^mm2 /s or more, more preferably 3.600 ^mm2 /s or more, and even more preferably 3.680 ^mm2 /s or more, with the upper limit being preferably 4.300 ^mm2 /s or less, more preferably 4.100 ^mm2 /s or less, and even more preferably 3.850 ^mm2 /s or less.
In this specification, the kinematic viscosity at 50° C. is a value measured in accordance with JIS K 2283:2000 (Testing method for kinematic viscosity of crude oil and petroleum products).

(3) Sulfur content The sulfur content of the fuel oil composition of this embodiment is 0.400% by mass or less. If the sulfur content is not within the above range, corrosion may occur due to an increase in sulfur oxides in the exhaust gas, and the environmental load may increase, resulting in a decrease in environmental performance. In consideration of the inhibition of corrosion and the improvement of environmental performance, the sulfur content is preferably 0.380% by mass or less, more preferably 0.350% by mass or less, and even more preferably 0.300% by mass or less. In addition, the lower the sulfur content, the more preferable it is, and there is no particular limit as to the lower limit, but from the viewpoint of improving storage stability and lubricity, it is usually 0.05% by mass or more.
In this specification, the content of sulfur other than fatty acid alkyl esters is measured by selecting a measurement method depending on the content, and when the content is 0.01 to 5 mass%, it is a value measured in accordance with JIS K 2541-4:2003 (Crude oil and petroleum products-Determination of sulfur content-Part 4: Radioactive excitation method).

(4) Aromatic content of 3 or more rings The aromatic content of 3 or more rings of the fuel oil composition of this embodiment is 2.9% by volume or more. If the aromatic content of 3 or more rings is not within the above range, the storage stability decreases. In particular, from the viewpoint of suppressing the decrease in the storage stability of the fatty acid alkyl ester and improving the storage stability of the fuel oil composition, it is preferably 3.0% by volume or more, more preferably 3.1% by mass or more, and even more preferably 3.2% by volume or more, and although there is no particular limit as the upper limit, it is usually 6.0% by volume or less.
In this specification, the aromatic content (monocyclic aromatic content, bicyclic aromatic content, and tricyclic or higher aromatic content), as well as the saturated content and olefin content, are values measured by the High Performance Liquid Chromatography method specified in JPI-5S-49-2007, Petroleum Products - Hydrocarbon Type Test Method.

(5) Carbon Residual in 10% Residual The carbon residual in the 10% residual of the fuel oil composition of this embodiment is 0.21% by mass or more and 0.60% by mass or less. If the carbon residual in the 10% residual exceeds 0.60% by mass, it becomes difficult to maintain the combustion performance, and sludge is easily generated, resulting in a decrease in room temperature oil passing performance. In addition, by making it 0.21% by mass or more, the fuel oil composition of this embodiment can be treated as heavy oil A and is not subject to the light oil delivery tax, so that a tax benefit can be obtained. From the viewpoint of improving the combustion performance and room temperature oil passing performance, and considering the tax benefit, the carbon residual in the 10% residual is preferably 0.22% by mass or more, and the upper limit is preferably 0.50% by mass or less, more preferably 0.45% by mass or less, even more preferably 0.40% by mass or less, and even more preferably 0.38% by mass or less.
In this specification, the carbon residue of 10% residual oil is a value measured in accordance with JIS K 2270-2:2009 (Crude petroleum and petroleum products-Determination of carbon residue-Part 2: Micro method) using 10% residual oil prepared in accordance with Appendix A.

In addition to the properties and composition of (1) to (5) above, the fuel oil composition of this embodiment preferably also satisfies at least one of the following (6) to (12), and it is particularly preferable that it satisfies all of the following (6) to (12).

(6) Flash Point From the viewpoint of safety in handling, the flash point of the fuel oil composition of the present embodiment is preferably 60.0° C. or higher, more preferably 65.0° C. or higher, and even more preferably 70.0° C. or higher. There is no particular upper limit, but it is usually 100.0° C. or lower.
In this specification, the flash point of a substance other than a fatty acid alkyl ester is a value measured in accordance with JIS K 2265-3:2007 (Crude oil and petroleum products-Flash point test method-Part 3: Pensky-Martens closed-cell method).

(7) Cetane Number The cetane number of the fuel oil composition of the present embodiment is preferably 39.0 or more, more preferably 40.0 or more, even more preferably 40.5 or more, and even more preferably 41.0 or more, and although there is no particular upper limit, it is usually 45.0 or less. When the cetane number is within the above range, the combustion performance is improved.
In this specification, the cetane number is a value determined in accordance with JIS K 2280-4:2013 (Petroleum products-Determination of octane number, cetane number and cetane index-Part 4: Cetane number).

(8) Water Content The water content of the fuel oil composition of the present embodiment is preferably 0.10% by volume or less, more preferably less than 0.10% by volume, and even more preferably 0.05% by volume or less. When the water content is within the above range, the generation of sludge due to an emulsion of asphaltene and water and the occurrence of freezing during storage at room temperature can be suppressed, thereby reducing the frequency of blockage in the fuel oil filter, and improving the room temperature oil passing performance.
In this specification, the water content other than fatty acid alkyl esters is a value measured in accordance with JIS K 2275-1:2015 (Crude oil and petroleum products-Determination of water content-Part 1: Distillation method).

(9) Copper Plate Corrosion The copper plate corrosion of the fuel oil composition of this embodiment is preferably 1 or less (1a or 1b) in the classification of copper plate in the copper plate judgment, and more preferably 1a. If the copper plate corrosion is 1 or less, corrosion of various auxiliary machines such as fuel oil tanks, piping, diesel engines, and pumps installed therein can be prevented, and therefore, more stable operation of various devices such as internal combustion engines and external combustion engines can be achieved.
In this specification, copper plate corrosion is measured in accordance with JIS K 2513:2000 (Petroleum products-Copper plate corrosion test method) at a test temperature of 50° C. and for a test time of 3 hours.

(10) Acid value The acid value of the fuel oil composition of this embodiment is preferably 0.05 mgKOH/g or less, more preferably less than 0.05 mgKOH/g, and even more preferably 0.03 mgKOH/g or less. The smaller the acid value, the more preferable it is, and there is no particular lower limit, and it is particularly preferably 0.0 mgKOH/g. When the acid value is within the above range, the frequency of blockage in the fuel oil filter can be reduced by suppressing the generation of sludge, so that the normal temperature oil passing performance can be improved, and corrosion of components such as storage tanks and piping during normal temperature storage can be further suppressed.
In this specification, the acid value is a value measured in accordance with JIS K 2501:2003 (Petroleum products and lubricants -- Determination of neutralization number).

(11) Pour Point The pour point of the fuel oil composition of the present embodiment is preferably −0.0° C. or lower, more preferably −2.5° C. or lower, and even more preferably −5.0° C. or lower, and although there is no particular lower limit, it is usually −35.0° C. or higher. When the pour point is within the above range, the fluidity in a storage tank or in piping at low temperatures is improved, and handleability is also improved.
In this specification, the pour point is a value measured in accordance with JIS K 2269:1987 (Test method for pour point and cloud point of crude oil and petroleum products).

(12) Nitrogen Content The nitrogen content of the fuel oil composition of this embodiment is preferably 200 ppm by mass or less, more preferably 190 ppm by mass or less, even more preferably 180 ppm by mass or less, and even more preferably 175 ppm by mass or less, and although there is no particular lower limit, it is usually 30 ppm by mass or more. If the nitrogen content is within the above range, NOx emissions can be reduced, and environmental performance is improved.
In this specification, the nitrogen content is a value measured in accordance with JIS K 2609:1998 (Crude oil and petroleum products -- Determination method for nitrogen content).

(Fatty acid alkyl ester)
The fuel oil composition of this embodiment satisfies all of the following ( _a1 ) to ( _a3 ) and contains a fatty acid alkyl ester, which is an ester of a fatty acid having from 8 to 22 carbon atoms and an alkyl alcohol having from 1 to 4 carbon atoms, in an amount of 15.0 vol. % or more and 35.0 vol. % or less based on the total amount of the composition.
( _a1 ) Cetane number is 49.0 or more; ( _a2 ) Acid value is 0.50 mgKOH/g or less; ( _a3 ) Residual carbon content of 10% residual oil is 0.80 mass% or more and 1.50 mass% or less.

( _a1 ) Cetane number The cetane number of the fatty acid alkyl ester is 49.0 or more. Fatty acid alkyl esters are known as oils with high cetane numbers, and by using fatty acid alkyl esters, the cetane number of the fuel oil composition of this embodiment can be improved, and the combustion performance can be improved. Therefore, if the cetane number of the fatty acid alkyl ester is less than 49.0, the effect of improving the cetane number of the fuel oil composition of this embodiment cannot be sufficiently obtained, and the combustion performance may be reduced.
From the viewpoint of improving combustion performance, the cetane number of the fatty acid alkyl ester is preferably 50.0 or more, more preferably 51.0 or more. There is no particular upper limit, and it is usually 70.0 or less.

( _a2 ) Acid value The acid value of the fatty acid alkyl ester is 0.50 mgKOH/g or less. If the acid value of the fatty acid alkyl ester is not within the above range, the frequency of clogging in the fuel oil filter is likely to occur due to the suppression of sludge generation, which may reduce the room temperature oil passing performance, and corrosion of components such as storage tanks and piping during storage at room temperature may occur. From the viewpoint of improving the room temperature oil passing performance and suppressing corrosion of components, the acid value of the fatty acid alkyl ester is preferably 0.48 mgKOH/g or less, more preferably 0.47 mgKOH/g or less, and even more preferably 0.46 mgKOH/g or less, with no particular lower limit, and is usually 0.05 mgKOH/g or more.

( _a3 ) Carbon Residual in 10% Residual The carbon residual in the 10% residual of the fatty acid alkyl ester is 0.80% by mass or more and 1.50% by mass or less. If the carbon residual in the 10% residual of the fatty acid alkyl ester is not within the above range, it is difficult to make the carbon residual in the 10% residual of the fuel oil composition of this embodiment 0.21% by mass or more and 0.60% by mass or less, so that it is difficult to maintain the combustion performance. In addition, it is difficult to reduce the frequency of clogging in the fuel oil filter, and the room temperature oil passing performance may be reduced.
By making it easier to make the residual carbon content of the 10% residual oil of the fuel oil composition of this embodiment 0.21 mass% or more and 0.60 mass% or less, from the viewpoint of improving combustion performance and room temperature oil passing performance, the residual carbon content of the 10% residual oil of the fatty acid alkyl ester is preferably 0.85 mass% or more, more preferably 0.90 mass% or more, even more preferably 1.00 mass% or more, and even more preferably 1.05 mass% or more, with the upper limit being preferably 1.40 mass% or less, more preferably 1.30 mass% or less, even more preferably 1.20 mass% or less, and even more preferably 1.10 mass% or less. In addition, it becomes easier to enjoy tax benefits.

(Fatty acids and alkyl alcohols)
In a broad sense, a fatty acid alkyl ester is an ester of a fatty acid and an alkyl alcohol. The fatty acid alkyl ester used in the present embodiment is an ester of a fatty acid having 8 to 22 carbon atoms and an alkyl alcohol having 1 to 4 carbon atoms, and satisfies all of the above ( _a1 ) to ( _a3 ).

As the fatty acid, either saturated or unsaturated fatty acids can be used. Among fatty acids having 8 to 22 carbon atoms, representative examples of saturated fatty acids include caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid, and behenic acid.

Representative examples of unsaturated fatty acids include monounsaturated fatty acids such as myristoleic acid, palmitoleic acid, oleic acid, eicosenoic acid, and erucic acid; and polyunsaturated fatty acids such as linoleic acid, linolenic acid, stearidonic acid, eicosadienoic acid, mead acid, arachidonic acid, eicosapentaenoic acid, docosadienoic acid, docosapentaenoic acid, and docosahexaenoic acid.

The fatty acid may be one type or a mixed fatty acid containing two or more types, and in consideration of making the fatty acid alkyl ester easily satisfy all of the above ( _a1 ) to ( _a3 ) and the following ( _a4 ) to ( _a11 ) and improving the combustion performance and room temperature oil passing performance, a mixed fatty acid containing two or more types is preferable. That is, it is preferable to use two or more fatty acid alkyl esters using mixed fatty acids containing two or more types as described below.
Although the above fatty acids are representative examples of straight-chain fatty acids, the fatty acids may be either straight-chain or branched-chain fatty acids as long as they have 8 or more and 22 or less carbon atoms.

Examples of the alkyl alcohol having 1 to 4 carbon atoms include methanol, ethanol, propanol, and butanol. Propanol and butanol may have a straight chain or a branched chain.
In consideration of making it easier for the fatty acid alkyl ester to satisfy all of the above ( _a1 ) to ( _a3 ) and further the following ( _a4 ) to ( _a11 ), thereby improving combustion performance and room temperature oil passing performance, and of the ease of production of the fatty acid alkyl ester, the carbon number is preferably 3 or less, more preferably 2 or less, i.e., more preferably methanol or ethanol, and particularly preferably methanol. Thus, the fatty acid alkyl ester used in this embodiment is particularly preferably a fatty acid methyl ester.

In the present embodiment, the fatty acid alkyl ester may be used alone or in combination of two or more. In order to make the fatty acid alkyl ester more likely to satisfy the above ( _a1 ) to ( _a3 ) and the following ( _a4 ) to ( _a11 ) and to improve the combustion performance and room temperature oil passing performance, it is preferable to use two or more in combination.
Examples of combinations of two or more types include two or more fatty acid alkyl esters formed from two or more fatty acids and one type of alkyl alcohol, two or more fatty acid alkyl esters formed from one type of fatty acid and two or more alkyl alcohol, and two or more fatty acid alkyl esters formed from two or more fatty acids and two or more alkyl alcohols, and any of these may be used in this embodiment.

In order to improve the combustion performance and room temperature oil passing performance by making it easier for the fatty acid alkyl ester to satisfy all of the above ( _a1 ) to ( _a3 ) and further the following ( _a4 ) to ( _a11 ), it is preferable to use two or more fatty acid alkyl esters composed of two or more fatty acids and one alkyl alcohol. When two or more fatty acids are used, for example, the fatty acids exemplified above may be mixed and used, or a mixed fatty acid containing two or more fatty acids may be used.
Preferred examples of mixed fatty acids include fatty acids obtained from raw materials such as animal oils, vegetable oils, etc. By using fatty acids derived from animals and plants obtained from these raw materials, it is possible to contribute to the suppression of global warming by reducing carbon dioxide emissions, and is extremely useful from the viewpoint of environmental protection.

Representative and preferred examples of animal oils that can be used as raw materials for mixed fatty acids include beef tallow, lard, mutton tallow, whale oil, fish oil, liver oil, etc. Representative and preferred examples of vegetable oils include linseed oil, safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, sesame oil, olive oil, castor oil, peanut oil, coconut oil, palm kernel oil, rapeseed oil, rice bran oil, etc.
When using a naturally derived raw material such as an animal oil or a vegetable oil, a pretreatment may be carried out as necessary before preparing a fatty acid alkyl ester by esterification with an alkyl alcohol. For example, the pretreatment may be carried out by purification such as distillation or clay treatment.

When two or more fatty acids are used, the two or more fatty acid alkyl esters preferably include fatty acid alkyl esters of an unsaturated fatty acid having 18 carbon atoms and an alkyl alcohol, and among the unsaturated fatty acids having 18 carbon atoms, it is more preferable to include fatty acid alkyl esters of oleic acid, linoleic acid, and linolenic acid, i.e., oleic acid alkyl esters, linoleic acid alkyl esters, and linolenic acid alkyl esters.
In this case, the total content of fatty acid alkyl esters of unsaturated fatty acids having 18 carbon atoms and alkyl alcohols contained in the fatty acid alkyl ester is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, and although there is no particular upper limit, it is preferable to set the upper limit to 95% by mass or less. When the total content of fatty acids having 18 carbon atoms is within the above range, the fatty acid alkyl ester can be easily made to satisfy all of the above ( _a1 ) to ( _a3 ) and further the following ( _a4 ) to ( _a11 ), thereby improving the combustion performance and room temperature oil passing performance.

The raw material of the mixed fatty acid is preferably vegetable oil, and more preferably rapeseed oil.The raw material of the mixed fatty acid is preferably waste edible oil, more preferably waste edible oil containing vegetable oil, and more preferably waste edible oil containing rapeseed oil, that is, vegetable oil containing rapeseed oil.By adopting waste edible oil for animal and vegetable oil, it is possible to avoid competition with food and to protect the environment by reusing waste.
Like the above-mentioned naturally derived raw materials such as animal oils and vegetable oils, waste edible oils may be pretreated as necessary before being esterified with alkyl alcohol to prepare fatty acid alkyl esters. For example, pretreatment by purification such as distillation or clay treatment may be performed.

In this embodiment, when fatty acids derived from animals and plants are used as the mixed fatty acids, fatty acids other than fatty acids having 8 to 22 carbon atoms, i.e., fatty acids having 7 or less and 23 or more carbon atoms, may be included. In this case, the content of fatty acids having 8 to 22 carbon atoms included in the mixed fatty acids is preferably 90% by mass or more, more preferably 92% by mass or more, and even more preferably 95% by mass or more. In other words, the content of fatty acids other than fatty acids having 8 to 22 carbon atoms is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less, and the lower limit is preferably as low as possible, and there is no particular limit, but it is usually 0.5% by mass or more.

In addition to the properties and composition of the above ( _a1 ) to ( _a3 ), the fatty acid alkyl ester preferably satisfies at least one selected from the following ( _a4 ) to ( _a11 ), and preferably satisfies all of the following ( _a4 ) to ( _a11 ).

( _a4 ) Density at 15°C The density of the fatty acid alkyl ester at 15°C is preferably 0.8700 g/ ^cm3 or more, more preferably 0.8800 g/ ^cm3 or more, or 0.8830 g/ ^cm3 or more, with the upper limit being preferably 0.9000 g/ ^cm3 or less, more preferably 0.8900 g/ ^cm3 or less, and even more preferably 0.8880 g/ ^cm3 or less. When the density at 15°C is within the above range, the density at 15°C of the fuel oil composition of this embodiment is easily set to 0.8700 g/ ^cm3 or more and 0.8900 g/ ^cm3 or less, so that the combustion performance and room temperature oil passing performance are improved, and the total calorific value is improved.

( _a5 ) Kinematic Viscosity at 50°C The kinematic viscosity of the fatty acid alkyl ester at 50°C is preferably ^3.000mm2 /s or more, more preferably ^3.200mm2 /s or more, and even more preferably ^3.500mm2 /s or more, with the upper limit being preferably ^4.500mm2 /s or less, more preferably ^4.200mm2 /s or less, and even more preferably ^3.800mm2 /s or less. If the kinematic viscosity at 50°C is within the above range, the kinematic viscosity at 50°C of the fuel oil composition of this embodiment can be easily adjusted to ^2.000mm2 /s or more and ^4.500mm2 /s or less, thereby improving combustion performance, making it easier to adapt to the range of use of various devices such as pumps and flow meters, and improving lubricity.

( _a6 ) Sulfur content The sulfur content of the fatty acid alkyl ester is preferably 3 ppm by mass or less, more preferably 2.5 ppm by mass or less, and the lower limit is not particularly limited because the lower the better. If the sulfur content is within the above range, the sulfur content of the fuel oil composition of the present embodiment can be easily set to 0.400% by mass or less, so that the occurrence of corrosion can be further suppressed and environmental performance can be improved.
In this specification, the sulfur content of the fatty acid alkyl ester is a value measured in accordance with JIS K 2541-6:2013 (Crude oil and petroleum products-Sulfur content test method-Part 6: Ultraviolet fluorescence method).

( _a7 ) Flash point From the viewpoint of safety in handling, the flash point of the fatty acid alkyl ester is preferably 100.0° C. or higher, more preferably 130.0° C. or higher, and even more preferably 150.0° C. or higher. There is no particular upper limit, but it is usually 200.0° C. or lower.
In this specification, the flash point of the fatty acid alkyl ester is a value measured in accordance with JIS K 2265-2:2007 (Crude oil and petroleum products-Flash point test method-Part 2: Rapid equilibrium closed test method).

( _a8 ) Moisture content The moisture content of the fatty acid alkyl ester is preferably 1000 mg/kg or less, more preferably 500 mg/kg or less, and even more preferably 250 mg/kg or less. The lower limit is not particularly limited, and the lower limit is preferably as low as possible. However, the moisture content is usually 100 mg/kg or more. When the moisture content is within the above range, the generation of sludge and freezing can be suppressed, and the frequency of blockage can be reduced, thereby improving the normal temperature oil passing performance.
In this specification, the water content of the fatty acid alkyl ester is a value measured in accordance with JIS K 2275-2:2015 (Crude oil and petroleum products-Determination of water content-Part 2: Karl Fischer volumetric titration method).

( _a9 ) Copper Plate Corrosion The copper plate corrosion of the fatty acid alkyl ester is preferably 1 or less (1a or 1b) in the classification of copper plate in the judgment of copper plate, and more preferably 1a. If the copper plate corrosion is 1 or less, the corrosion of various auxiliary machines can be prevented, and therefore, various devices such as internal combustion engines and external combustion engines can be operated more stably.

(a ₁₀ ) Pour Point The pour point of the fatty acid alkyl ester is preferably −0.0° C. or lower, more preferably −2.5° C. or lower, and although there is no particular lower limit, it is usually −20.0° C. or higher. When the pour point is within the above range, the fluidity in a storage tank or in a piping at low temperatures is improved, and the handleability is also improved.

(a ₁₁ ) Composition Analysis The composition analysis of fatty acid alkyl esters can be carried out by gas chromatography analysis using a flame ionization detector (FID) in accordance with "2.4.21.3-77 Fatty acid composition (FID temperature-programmed gas chromatographic method)" in the Standard Methods for Analysis of Fats, Oils and Related Materials (established by the Japan Oil Chemists' Society in 1993).
As the fatty acid alkyl ester, as described above, it is preferable to include a fatty acid alkyl ester of an alkyl alcohol and a mixed fatty acid containing at least an unsaturated fatty acid having 18 carbon atoms, particularly oleic acid, linoleic acid, and linolenic acid. The total content of the mixed fatty acid containing at least oleic acid, linoleic acid, and linolenic acid and the fatty acid alkyl ester of an alkyl alcohol based on the total amount of the fatty acid alkyl ester is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more, and although there is no particular upper limit, it is preferable to set it to 95% by mass or less.

When the fatty acid alkyl ester contains two or more kinds of fatty acid alkyl esters, it is preferable that they contain at least an oleic acid alkyl ester, a linoleic acid alkyl ester, and a linolenic acid alkyl ester (a fatty acid alkyl ester of an unsaturated fatty acid having 18 carbon atoms and an alkyl alcohol) as described above.
It is more preferable that the composition further contains a stearic acid alkyl ester (a fatty acid alkyl ester of a saturated fatty acid having 18 carbon atoms and an alkyl alcohol), and even more preferable that the composition further contains a palmitic acid alkyl ester (a fatty acid alkyl ester of a saturated fatty acid having 16 carbon atoms and an alkyl alcohol), and even more preferable that the composition further contains an arachidic acid alkyl ester and an erucic acid alkyl ester (a fatty acid alkyl ester of a saturated fatty acid having 20 or 22 carbon atoms and an alkyl alcohol), as well as an eicosenoic acid alkyl ester and a behenic acid alkyl ester (a fatty acid alkyl ester of an unsaturated fatty acid having 20 or 22 carbon atoms and an alkyl alcohol), and even more preferable that the composition further contains at least one selected from a caprylic acid alkyl ester, a capric acid alkyl ester, a lauric acid alkyl ester, and a myristic acid alkyl ester.

(Fatty acid alkyl ester content)
The content of the fatty acid alkyl ester based on the total amount of the composition is 15.0% by volume or more and 35.0% by volume or less. If the content of the fatty acid alkyl ester is less than 15.0% by volume, the combustion performance decreases, and if it exceeds 35.0% by volume, the room temperature oil passing performance decreases. From the viewpoint of improving the combustion performance and the room temperature oil passing performance, the content of the fatty acid alkyl ester based on the total amount of the composition is preferably 17.5% by volume or more, and the upper limit is preferably 32.5% by volume or less.

(Light cracked oil fraction)
The fuel oil composition of this embodiment contains a cracked light oil fraction in an amount of 20.0% by volume or more and 40.0% by volume or less based on the total volume of the composition. The cracked light oil fraction is a catalytically cracked light oil fraction obtained by fluid catalytic cracking of atmospheric distillation residue oil and/or vacuum distillation residue oil. The cracked light oil fraction used in this embodiment is one of the above fractions that satisfies the properties and composition of the following ( _b1 ) to ( _b4 ).
( _b1 ) a kinematic viscosity at 50°C of 1.700 ^mm2 /s or more and 3.600 ^mm2 /s or less; ( _b2 ) a sulfur content of 0.40 mass% or less; ( _b3 ) an aromatic content of 50.0 volume% or more; ( _b4 ) an aromatic content of 3 or more rings of 5.0 volume% or more.

( _b1 ) Kinematic Viscosity at 50° C. The kinematic viscosity of the cracked light oil fraction at 50° C. is 1.700 mm ² /s or more and 3.600 mm ² /s or less. If the kinematic viscosity at 50° C. is not within the above range, it will be difficult to achieve a kinematic viscosity at 50° C. of 2.000 mm ² /s or more and 4.500 mm ² /s or less for the fuel oil composition of this embodiment, which may result in reduced combustion performance, difficulty in conforming to the range of use of various equipment such as pumps and flow meters, and reduced lubricity.
By making it easier to keep the kinematic viscosity at 50°C of the fuel oil composition of this embodiment within the above range, it is possible to improve combustion performance, make it easier to adapt to the range of use of various equipment, and improve lubricity.From the standpoint of this, the kinematic viscosity is preferably 1.900 ^mm2 /s or more, more preferably 2.100 ^mm2 /s or more, with the upper limit being preferably 3.400 ^mm2 /s or less, more preferably 3.200 ^mm2 /s or less.

( _b2 ) Sulfur content The sulfur content of the cracked light oil fraction is 0.400 mass% or less. If the sulfur content is not within the above range, it is difficult to make the sulfur content of the fuel oil composition of the present embodiment 0.400 mass% or less, so it is difficult to suppress the occurrence of corrosion, and environmental performance may be reduced.
In order to suppress the occurrence of corrosion and improve environmental performance by making it easier to keep the sulfur content of the fuel oil composition of this embodiment to 0.400 mass% or less, the sulfur content of the cracked light oil fraction is preferably 0.300 mass% or less, more preferably 0.250 mass% or less, and the lower limit is preferably as low as possible, and although there is no particular restriction, it is usually 0.05 mass% or more.

( _b3 ) Aromatic content The aromatic content of the cracked light oil fraction is 50.0% by volume or more. Here, the aromatic content refers to the total content of one-ring aromatics, two-ring aromatics, and three or more ring aromatics. If the aromatic content is not within the above range, it is not possible to suppress clogging of the fuel oil filter due to the generation of sludge, and the normal oil passing performance may decrease and the combustion performance may also decrease.
From the viewpoint of further suppressing fuel oil filter clogging due to sludge generation, thereby improving normal oil passing performance and improving combustion performance, the content is preferably 60.0 vol.% or more, more preferably 65.0 vol.% or more, and the upper limit is preferably 85.0 vol.% or less.

( _b4 ) Content of aromatics with 3 or more rings The content of aromatics with 3 or more rings in the cracked light oil fraction is 5.0% by volume or more. If the content of aromatics with 3 or more rings is not within the above range, it is difficult to make the content of aromatics with 3 or more rings in the fuel oil composition of this embodiment 2.9% by volume or more, which may result in reduced storage stability.
In the fuel oil composition of this embodiment, the aromatic content of 3 or more rings is easily adjusted to 2.9% by volume or more, and from the viewpoint of improving storage stability, the aromatic content is preferably 6.0% by volume or more, and more preferably 7.0% by volume or more, with no particular upper limit, and is usually 15.0% by volume or less.

In addition to the properties and composition of the above (b ₁ ) to (b ₄ ), the cracked light oil fraction preferably satisfies at least one selected from the following (b ₅ ) to (b ₁₄ ), and more preferably satisfies all of the following (b ₅ ) to (b ₁₄ ).

( _b5 ) Density at 15°C The density at 15°C of the cracked light oil fraction is preferably 0.9000g/ ^cm3 or more, more preferably 0.9100g/ ^cm3 or more, and even more preferably 0.9120g/ ^cm3 or more, with the upper limit being preferably 0.9400g/ ^cm3 or less, more preferably 0.9300g/ ^cm3 or less, and even more preferably 0.9200g/ ^cm3 or less. If the density at 15°C is within the above range, the kinematic viscosity at 15°C of the fuel oil composition of this embodiment is easily adjusted to 0.8700g/ ^cm3 or more and 0.8900g/ ^cm3 or less, thereby improving room temperature oil passing performance and combustion performance, and further improving the total calorific value.

(b ₆ ) Flash Point From the viewpoint of improving safety in handling, the flash point of the cracked light oil fraction is preferably 65.0° C. or higher, more preferably 70.0° C. or higher.

( _b7 ) Residual carbon content of 10% residual oil The residual carbon content of 10% residual oil of the cracked light oil fraction is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and the upper limit is preferably 0.20 mass% or less. If the residual carbon content of 10% residual oil is within the above range, the residual carbon content of the 10% residual oil of the fuel oil composition of this embodiment can be easily set to 0.21 mass% or more and 0.60 mass% or less, thereby improving the combustion performance and room temperature oil passing performance. In addition, it is easier to enjoy tax benefits.

( _b8 ) Cetane Number The cetane number of the cracked light oil fraction is preferably 20.0 or more, more preferably 25.0 or more, and there is no particular upper limit, but it is usually 50.0 or less. If the cetane number is within the above range, the combustion performance is improved.

( _b9 ) Water Content The water content of the cracked light oil fraction is preferably 0.10% by volume or less, more preferably less than 0.10% by volume, and even more preferably 0.05% by volume or less. If the water content is within the above range, the generation of sludge and the occurrence of freezing can be suppressed, and the frequency of blockage can be reduced, thereby improving the normal temperature oil passing performance.

( _b10 ) Copper Plate Corrosion The copper plate corrosion of the cracked light oil fraction is preferably 1 or less (1a or 1b) in the classification of copper plate in the copper plate judgment, and more preferably 1a. If the copper plate corrosion is 1 or less, corrosion of various auxiliary machines can be prevented, and more stable operation of various equipment such as internal combustion engines and external combustion engines is possible.

( _b11 ) Acid value The acid value of the cracked light oil fraction is preferably 0.05 mgKOH/g or less, more preferably less than 0.05 mgKOH/g, and even more preferably 0.03 mgKOH/g or less. The smaller the acid value, the more preferable it is, and there is no particular lower limit, and 0.0 mgKOH/g is particularly preferred. If the acid value is within the above range, the normal temperature oil passing performance is improved, and corrosion of components can be suppressed.

(b ₁₂ ) Pour Point The pour point of the cracked light oil fraction is preferably −10.0° C. or lower, more preferably −12.5° C. or lower, and even more preferably −15.0° C. or lower, and although there is no particular lower limit, it is usually −35.0° C. or higher. If the pour point is within the above range, the fluidity in storage tanks and piping at low temperatures is improved, and the handleability is also improved.

( _b13 ) Nitrogen Content The nitrogen content of the cracked light oil fraction is preferably 500 ppm by mass or less, more preferably 400 ppm by mass or less, and even more preferably 300 ppm by mass or less. Although there is no particular lower limit, it is usually 50 ppm by mass or more. If the nitrogen content is within the above range, NOx emissions can be reduced, improving environmental performance.

(b ₁₄ ) Distillation Properties As the distillation properties of the cracked light oil fraction, the 10% by volume distillation temperature is preferably 170.0 ° C. or more, more preferably 180.0 ° C. or more, and even more preferably 195.0 ° C. or more, and the upper limit is preferably 230.0 ° C. or less, more preferably 220.0 ° C. or less, and even more preferably 210.0 ° C. or less. The 50% by volume distillation temperature is preferably 240.0 ° C. or more, more preferably 250.0 ° C. or more, and even more preferably 260.0 ° C. or more, and the upper limit is preferably 300.0 ° C. or less, more preferably 285.0 ° C. or less, and even more preferably 270.0 ° C. or less. The 90% by volume distillation temperature is preferably 310.0 ° C. or more, more preferably 320.0 ° C. or more, and even more preferably 330.0 ° C. or more, and the upper limit is preferably 370.0 ° C. or less, more preferably 355.0 ° C. or less, and even more preferably 340.0 ° C. or less. When the distillation properties of the cracked light oil fraction are the above 10 vol. % distillation temperature, 50 vol. % distillation temperature and 90 vol. % distillation temperature, the effects of low boiling point components and high boiling point components are suppressed and combustion performance is improved.
In this specification, the 10% by volume distillation temperature, 50% by volume distillation temperature, and 90% by volume distillation temperature of the distillation properties are values measured in accordance with JIS K2254:2018 (Petroleum products-Determination of distillation properties-(normal pressure method)).

(Content of cracked gas oil fraction)
The content of the cracked light oil fraction based on the total amount of the composition is 20.0% by volume or more and 40.0% by volume or less. If the content of the cracked light oil fraction is less than 20.0% by volume, the room temperature oil passing performance decreases, and if it exceeds 40.0% by volume, the combustion performance decreases. From the viewpoint of improving the combustion performance and room temperature oil passing performance, the content of the cracked light oil fraction based on the total amount of the composition is preferably 22.5% by volume or more, and the upper limit is preferably 37.5% by volume or less.

(Other diesel and kerosene fractions)
The fuel oil composition of this embodiment may contain, in addition to the above-mentioned cracked light oil fraction, light oil fractions such as straight-run light oil fraction, vacuum light oil fraction, desulfurized light oil fraction, desulfurized cracked light oil fraction, and kerosene fractions such as straight-run kerosene fraction, desulfurized kerosene fraction, etc. Among these light oil fractions and kerosene fractions, straight-run light oil fractions are preferred from the viewpoint of improving combustion performance and normal temperature oil passing performance by combining with fatty acid alkyl esters and cracked light oil fractions.
Directly desulfurized diesel fraction (a diesel fraction obtained by directly desulfurizing atmospheric distillation residue and/or vacuum distillation residue in a desulfurization unit)
・Straight-run diesel fraction (diesel fraction obtained by distilling crude oil at atmospheric pressure using an atmospheric distillation unit)
・Vacuum diesel fraction (diesel fraction obtained by vacuum distillation of atmospheric distillation residue using a vacuum distillation unit)
・Desulfurized diesel fraction (a diesel fraction obtained by desulfurizing a straight-run diesel fraction and/or a vacuum diesel fraction)
・Desulfurized cracked diesel fraction (a diesel fraction obtained by desulfurizing a catalytic cracked diesel fraction obtained by fluid catalytic cracking of atmospheric distillation residue and/or vacuum distillation residue)
・Straight-run kerosene fraction (kerosene fraction obtained by distilling crude oil at atmospheric pressure using an atmospheric distillation unit)
・Desulfurized kerosene fraction (kerosene fraction obtained by desulfurizing straight-run kerosene fraction)

(Properties of other diesel fractions)
The other diesel fractions that can be used in the present embodiment preferably have the following properties. When the other diesel fractions have the following properties, excellent combustion performance and room temperature oil passing performance are easily obtained.
The kinetic viscosity at 50° C. is preferably 2.900 mm ² /s or more, more preferably 4.000 mm ² /s or more, and the upper limit is preferably 5.000 mm ² /s or less, more preferably 4.400 mm ² /s or less.
The sulfur content is preferably 0.40% by mass or less, more preferably 0.10% by mass or less, and the lower limit is preferably as low as possible, and is usually 0.01% by mass.
The aromatic content is preferably 40.0% by volume or more, more preferably 42.0% by volume or less, and there is no particular upper limit, but it is usually 65.0% by volume or less.
The content of aromatic components having 3 or more rings is preferably 2.0% by volume or more, more preferably 2.3% by volume or more, and there is no particular upper limit, but it is usually 5.0% by volume or less.
The density at 15° C. is preferably 0.8300 g/cm ³ or more, more preferably 0.8400 g/cm ³ or more, and the upper limit is preferably 0.8900 g/cm ³ or less, more preferably 0.8800 g/cm ³ or less.
The flash point is preferably 60.0° C. or higher, more preferably 65.0° C. or higher.
The residual carbon content of the 10% residual oil is preferably 0.01% by mass or more, and the upper limit is preferably 0.20% by mass or less.
The cetane number is preferably 30.0 or more, more preferably 35.0 or more, and there is no particular upper limit, but it is usually 70.0 or less.
The moisture content is preferably 0.10% by volume or less, more preferably less than 0.10% by volume, and even more preferably 0.05% by volume or less.
The copper plate corrosion is preferably classified as 1 or less (1a or 1b) in the evaluation of the copper plate, and more preferably 1a.
The acid value is preferably 0.05 mgKOH/g or less, more preferably less than 0.05 mgKOH/g, and even more preferably 0.03 mgKOH/g or less. The smaller the acid value, the more preferable it is, and there is no particular lower limit, and the most preferable is 0.0 mgKOH/g.
The pour point is preferably −0.0° C. or lower, more preferably −2.5° C. or lower.
The nitrogen content is preferably 500 ppm by mass or less, more preferably 400 ppm by mass or less, and further preferably 300 ppm by mass or less. There is no particular lower limit, but it is usually 50 ppm by mass or more.
As for the distillation properties, the 10% by volume distillation temperature is preferably 170.0° C. or higher, more preferably 180.0° C. or higher, and the upper limit is preferably 270.0° C. or lower, more preferably 260.0° C. or lower. The 50% by volume distillation temperature is preferably 250.0° C. or higher, more preferably 265.0° C. or higher, and the upper limit is preferably 310.0° C. or lower, more preferably 300.0° C. or lower. The 90% by volume distillation temperature is preferably 310.0° C. or higher, more preferably 330.0° C. or higher, and the upper limit is preferably 370.0° C. or lower, more preferably 355.0° C. or lower.

(Other heavy oil fractions)
The fuel oil composition of the present embodiment may also contain atmospheric distillation residual oil, vacuum distillation residual oil, direct decomposition heavy oil fraction, and cracked heavy oil. Among these heavy oil fractions, atmospheric distillation residual oil is preferred from the viewpoint of improving combustion performance and room temperature oil passing performance by combining with fatty acid alkyl esters and cracked light oil fractions.
・Atmospheric distillation residual oil (residual oil obtained by atmospheric distillation of crude oil using an atmospheric distillation unit)
・Vacuum distillation residual oil (residual oil obtained by vacuum distilling atmospheric distillation residual oil using a vacuum distillation apparatus)
Directly desulfurized heavy oil fraction (heavy oil fraction obtained by directly desulfurizing atmospheric distillation residue and/or vacuum distillation residue in a desulfurization unit)
・Cracked heavy oil fraction (heavy oil fraction obtained by fluid catalytic cracking of directly decomposed heavy oil fraction)

(Properties of other heavy oil fractions)
The other heavy oil fractions that can be used in the present embodiment preferably have the following properties. When the other heavy oil fractions have the following properties, excellent combustion performance and room temperature oil passing performance are easily obtained.
The kinematic viscosity at 50° C. is preferably 190.0 mm ² /s or less, more preferably 185.0 mm ² /s or less, and there is no particular lower limit, but it is usually 30.00 mm ² /s or more.
The sulfur content is preferably 3.0% by mass or less, more preferably 2.75% by mass or less, and there is no particular lower limit, but it is usually 0.50% by mass or more.
The density at 15° C. is preferably 0.8800 g/cm ³ or more, more preferably 0.9000 g/cm ³ or more, and the upper limit is preferably 0.9700 g/cm ³ or less, more preferably 0.9600 g/cm ³ or less.
The carbon residue is preferably 12.0% by mass or less, more preferably 9.0% by mass or less, and even more preferably 7.5% by mass or less, with the lower limit being preferably 3.0% by mass or more, and more preferably 5.0% by mass or more. In this specification, the carbon residue is a value measured in accordance with JIS K 2270-2:2009 (Crude oil and petroleum products-Determination of carbon residue-Part 2: Micro method).

(Various additives)
In the fuel oil composition of this embodiment, various additives such as antioxidants, low-temperature fluidity improvers, lubricity improvers, cetane number improvers, combustion promoters, detergents, sludge dispersants, and fungicides can be appropriately selected and blended as necessary within the range that allows the above-mentioned various properties to be maintained. In addition, coumarin may be blended from the viewpoint of diesel delivery tax.

(Application)
The fuel oil composition of the present embodiment can be used in both internal combustion engines and external combustion engines, but considering the excellent combustion performance and room temperature oil passing performance, it is preferable to use it in an internal combustion engine. In addition, considering the above-mentioned properties of the fuel oil composition of the present embodiment, it is particularly suitable for use in internal combustion engines such as marine diesel engines.

[Method for producing fuel oil composition]
The fuel oil composition of this embodiment can be produced by mixing the above-mentioned fatty acid alkyl ester and cracked light oil fraction, and, if necessary, other light oil fractions, kerosene fractions, heavy oil fractions, and various additives, so that the contents of the fatty acid alkyl ester and the cracked light oil fraction based on the total volume of the composition are 15.0 vol.% or more and 35.0 vol.% or less, and 20.0 vol.% or more and 40.0 vol.% or less, respectively.

There is no particular restriction on the order of mixing the fatty acid alkyl ester, the cracked light oil fraction, and, if necessary, other light oil fractions, kerosene fractions, heavy oil fractions, and various additives. For example, the fatty acid alkyl ester may be mixed by sequentially adding the cracked light oil fraction, the other light oil fractions, heavy oil fractions, and various additives to the fatty acid alkyl ester, or the fatty acid alkyl ester, the cracked light oil fraction, and, if necessary, the other light oil fractions, kerosene fractions, heavy oil fractions, and various additives may be mixed simultaneously (lump-mixing), or the fatty acid alkyl ester and the cracked light oil fraction may be mixed in advance, and then the other light oil fractions, kerosene fractions, heavy oil fractions, and various additives may be mixed as necessary.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The properties of each substrate were determined according to the following methods, as described above.

[Measurement of properties and composition]
The properties and compositions of the various base materials, i.e., fatty acid alkyl esters, cracked light oil fraction, direct desulfurized light oil fraction, direct desulfurized light oil fraction, and atmospheric distillation residual oil, used in the Examples and Comparative Examples, and the properties and compositions of the fuel oil compositions in the Examples and Comparative Examples, were measured by the following methods. The properties and compositions of the fatty acid alkyl esters are shown in Table 1, and the properties and compositions of the other various base materials are shown in Table 2. The properties and compositions of the fuel oil compositions are shown in Table 3.
(1) (a ₄ ) (b ₅ ) Density at 15°C: Measured in accordance with JIS K 2249-1:2011 (Crude oil and petroleum products -- Determination of density -- Part 1: Vibration method).
(2) ( _a5 ) ( _b1 ) Kinematic viscosity at 50°C: Measured in accordance with JIS K 2283:2000 (Testing method for kinematic viscosity of crude oil and petroleum products).
(3) ( _a6 ) ( _b2 ) Sulfur content: The sulfur contents of the fuel oil composition, the cracked light oil fraction, the straight-run light oil fraction, and the atmospheric distillation residue are measured in accordance with JIS K 2541-4:2003 (Crude oil and petroleum products-Determination of sulfur content-Part 4: Radioactive excitation method), and the sulfur content of the fatty acid alkyl ester is measured in accordance with JIS K 2541-6:2013 (Crude oil and petroleum products-Determination of sulfur content-Part 6: Ultraviolet fluorescence method).
(4) (b ₃ ) (b ₄ ) Aromatic content (monocyclic aromatic content, dicyclic aromatic content and tricyclic aromatic content), saturates content and olefin content: These were measured by the High Performance Liquid Chromatography method specified in JPI-5S-49-2007, Petroleum Products-Hydrocarbon Type Testing Method.
(5) ( _a3 ) ( _b7 ) Carbon residue of 10% residual oil: This is a value measured in accordance with JIS K 2270-2:2009 (Crude petroleum and petroleum products -- Determination of carbon residue -- Part 2: Micro method) using 10% residual oil prepared in accordance with Appendix A.
(6) ( _a7 ) ( _b6 ) Flash point: The flash points of the fuel oil composition, the cracked light oil fraction, the straight-run light oil fraction, the straight-run light oil fraction and the atmospheric distillation residual oil were measured in accordance with JIS K 2265-3:2007 (Crude oil and petroleum products-Flash point test-Part 3: Pensky-Martens closed-close method), and the flash point of the fatty acid alkyl ester was measured in accordance with JIS K 2265-2:2007 (Crude oil and petroleum products-Flash point test-Part 2: Rapid equilibrium closed-close method).
(7) (a ₁ ) (b ₈ ) Cetane number: a value measured in accordance with JIS K 2280-4:2013 (Petroleum products-Determination of octane number, cetane number and cetane index-Part 4: Cetane number).
(8) ( _a8 ) ( _b9 ) Moisture content: The moisture content of the fuel oil composition, the cracked light oil fraction, the straight-run light oil fraction, and the atmospheric distillation residual oil was measured in accordance with JIS K 2275-1:2015 (Crude oil and petroleum products -- Determination of moisture -- Part 1: Distillation method), and the moisture content of the fatty acid alkyl ester was measured in accordance with JIS K 2275-3:2015 (Crude oil and petroleum products -- Determination of moisture -- Part 3: Karl Fischer coulometric titration method).
(9) ( _a9 ) ( _b10 ) Copper plate corrosion: Measured according to JIS K 2513:2000 (Petroleum products - Copper plate corrosion test method) The test temperature was 50°C and the test time was 3 hours.
(10) (a ₂ ) (b ₁₁ ) Acid value: Measured in accordance with JIS K 2501:2003 (Petroleum products and lubricants -- Determination of neutralization number).
(11) (a ₁₀ ) (b ₁₂ ) Pour point: Measured in accordance with JIS K2269:1987 (Test method for pour point and cloud point of crude oil and petroleum products).
(12) (b ₁₃ ) Nitrogen content: Measured in accordance with JIS K 2609:1998 (Crude petroleum and petroleum products -- Determination of nitrogen content).
(a ₁₁ ) Composition analysis of fatty acid alkyl ester: Measured by gas chromatography analysis using a flame ionization detector (FID) in accordance with "2.4.21.3-77 Fatty acid composition (FID temperature-programmed gas chromatograph method)" in the Standard Methods for Analysis of Fats, Oils and Related Materials (established by the Japan Oil Chemists' Society in 1993).
(b ₁₄ ) Distillation properties (10% by volume distillation temperature, 50% by volume distillation temperature, and 90% by volume distillation temperature): Measured in accordance with JIS K2254:2018 (Petroleum products - Determination of distillation properties - (normal pressure method)).

[Performance evaluation criteria]
The following performances were evaluated according to 1 to 4, and the worst evaluation was used as the overall evaluation. Evaluation of each performance is shown in Table 3.

1. Combustion Performance The increase in cetane number (Δ cetane number) of the fuel oil compositions of the Examples and Comparative Examples relative to the cetane number of the Reference Example was evaluated according to the following criteria.
A: The increase in cetane number (Δ cetane number) is 2.5 or more. B: The increase in cetane number (Δ cetane number) is 2.0 or more and less than 2.5. C: The increase in cetane number (Δ cetane number) is less than 2.0.

2. Room temperature oil permeability Three liters of the fuel oil compositions of the Examples and Comparative Examples were placed in an 18 L can (made of tinplate) with an open section (φ32.5 mm) at the top to allow air to circulate, and stored in a dark place at room temperature for 90 days (no temperature control was performed by air conditioning, and the room temperature during the period was 16.0 to 28.0°C). After storage, the fuel oil compositions were subjected to an oil permeability test using an oil permeability tester described in JP 2007-197512 A. The amount of oil passing through the fuel oil composition for 10 minutes was evaluated according to the following criteria.
A: The amount of oil passing is 1.10 L or more. B: The amount of oil passing is 0.70 L or more and less than 1.10 L. C: The amount of oil passing is less than 0.70 L.

3. Low-Temperature Flow Performance The pour points of the Examples and Comparative Examples were evaluated according to the following criteria.
A: Pour point is -2.5°C or less. B: Pour point is greater than -2.5°C and less than 5.0°C. C: Pour point is greater than 5.0°C.

4. Environmental performance Based on the sulfur content, the following criteria were used to evaluate the environmental performance.
A: Sulfur content is 0.300 mass% or less B: Sulfur content is more than 0.300 mass% and 0.400 mass% or less C: Sulfur content is more than 0.400 mass%

[Examples 1 to 3, Comparative Examples 1 to 7 and Reference Example]
Various base materials having the properties and compositions shown in Tables 1 and 2 were mixed in the ratios shown in Table 3 to prepare the fuel oil compositions of Examples 1 to 3, Comparative Examples 1 to 7 and Reference Example.
The resulting fuel oil compositions were evaluated for combustion performance, room temperature oil passing performance, low temperature flow performance and environmental performance according to the methods described above. The results are shown in Table 3.

*1. Base material 1 (fatty acid alkyl ester 1) and base material 2 (fatty acid alkyl ester 2) are both fatty acid methyl esters obtained using waste edible oil containing rapeseed oil.

[Performance evaluation results]
As shown in Table 3, the fuel oil composition of this embodiment was evaluated to be good in terms of combustion performance, room temperature oil passing performance, low temperature flow performance and environmental performance, and it was confirmed that the composition can withstand use in internal combustion engines, particularly marine diesel engines.
On the other hand, the fuel oil composition of Comparative Example 1, which contains specific fatty acid alkyl ester 1 but in a small amount, is inferior in combustion performance, while the fuel oil composition of Comparative Example 2, which contains a large amount, is inferior in room temperature oil passing performance. It was confirmed that the fuel oil compositions of Comparative Examples 5 to 7, which do not contain specific fatty acid alkyl ester 1 and contain fatty acid alkyl ester 2 with a small residual carbon content in 10% residual oil, all have inferior room temperature oil passing performance. It was also confirmed that the fuel oil composition of Comparative Example 3, which contains a small amount of cracked light oil fraction, is inferior in room temperature oil passing performance, while the fuel oil composition of Comparative Example 4, which contains a large amount, is inferior in combustion performance.

The fuel oil composition of this embodiment contains fatty acid alkyl esters, and thus has excellent combustion performance, room temperature oil passing performance, and excellent low-temperature flow performance and environmental performance. It is suitable for use in internal combustion engines and external combustion engines, and is particularly suitable for use in internal combustion engines such as marine diesel engines.

Claims (7)

A fuel oil composition comprising a fatty acid alkyl ester satisfying all of the following ( _a1 ) to ( _a3 ) and a cracked light oil fraction satisfying all of the following ( _b1 ) to ( _b4 ), wherein the fatty acid alkyl ester is an ester of a fatty acid having from 8 to 22 carbon atoms and an alkyl alcohol having from 1 to 4 carbon atoms, the content of the fatty acid alkyl ester is from 15.0 to 35.0 vol. % based on the total volume of the composition, and the content of the cracked light oil fraction is from 20.0 to 40.0 vol. % based on the total volume of the composition, and the composition satisfies all of the following (1) to (5).
( _a1 ) Cetane number is 49.0 or more; ( _a2 ) Acid number is 0.50 mgKOH/g or less; ( _a3 ) Residual carbon content of 10% residual oil is 0.80 mass% or more and 1.50 mass% or less; ( _b1 ) Kinematic viscosity at 50°C is 1.700 ^mm2 /s or more and 3.600 ^mm2 /s or less; ( _b2 ) Sulfur content is 0.40 mass% or less; ( _b3 ) Aromatic content is 50.0 vol% or more; ( _b4 ) 3 or more ring aromatic content is 5.0 vol% or more; (1) Density at 15°C is 0.8700 g/cm3 ^or more and 0.8900 g/cm3 ^or less; (2) Kinematic viscosity at 50°C is 2.000 ^mm2 /s or more and 4.500 ^mm2 /s or more; (3) Sulfur content is 0.400 mass% or less; (4) Three or more ring aromatic content is 2.9 volume% or more; (5) Residual carbon content of 10% residual oil is 0.21 mass% or more and 0.60 mass% or less. The fuel oil composition according to claim 1, wherein the fatty acid alkyl ester is a fatty acid methyl ester. The fuel oil composition according to claim 1 or 2, wherein the fatty acid is a mixed fatty acid containing two or more fatty acids having 8 to 22 carbon atoms. The fuel oil composition according to claim 3, wherein the mixed fatty acid is obtained from at least one raw material selected from animal oils and vegetable oils. The fuel oil composition according to claim 4, wherein the raw material is waste edible oil. The fuel oil composition according to any one of claims 1 to 5, which is used in an internal combustion engine. A method for producing a fuel oil composition that satisfies all of the following ( ₁ ) to ( ₅ ), comprising mixing a fatty acid alkyl ester, which is an ester of a fatty acid having from 8 to 22 carbon atoms and an alkyl alcohol having from ₁ to ₄ carbon atoms and satisfies all of the following (a1) to (a3), with a cracked light oil fraction that satisfies all of the following (b1) to (b4), so that the content of the fatty acid alkyl ester is from 15.0 to 35.0 vol. % based on the total volume of the composition, and the content of the cracked light oil fraction is from 20.0 to 40.0 vol. % based on the total volume of the composition.
( _a1 ) Cetane number is 49.0 or more; ( _a2 ) Acid number is 0.50 mgKOH/g or less; ( _a3 ) Residual carbon content of 10% residual oil is 0.80 mass% or more and 1.50 mass% or less; ( _b1 ) Kinematic viscosity at 50°C is 1.700 ^mm2 /s or more and 3.600 ^mm2 /s or less; ( _b2 ) Sulfur content is 0.40 mass% or less; ( _b3 ) Aromatic content is 50.0 vol% or more; ( _b4 ) 3 or more ring aromatic content is 5.0 vol% or more; (1) Density at 15°C is 0.8700 g/cm3 ^or more and 0.8900 g/cm3 ^or less; (2) Kinematic viscosity at 50°C is 2.000 ^mm2 /s or more and 4.500 ^mm2 /s or more; (3) Sulfur content is 0.400 mass% or less; (4) Three or more ring aromatic content is 2.9 volume% or more; (5) Residual carbon content of 10% residual oil is 0.21 mass% or more and 0.60 mass% or less.