JPH0662964B2 - Fuel oil composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel oil composition mainly composed of a heavy fraction in petroleum having improved hue, less sludge generation, and improved low temperature fluidity. It is about things.

Among the known distillates obtained from Touri crude oil, the distillate with a boiling point of about 150 to 450 ° C, called the medium distillate, is
It is used in large quantities in various fuel sources such as kerosene, light oil, and heavy oil A.

These kerosene, light oil, and A heavy oil are particularly strong as demand for petroleum products as three intermediate products, and compared with the sharp decline in crude oil prices after the oil shock, B, C heavy oil, etc. fell significantly. You can see a strong growth.

Among them, heavy fuel oil A is used for many purposes, but typical applications include fuel for internal combustion engines of ships, fuel for warmers in house agriculture, and boiler fuel for heating in buildings and homes. A heavy oil is Japanese Industrial Standard No. JISK2205
The quality has been standardized as the first type of heavy oil specified in 1), and is further subdivided into No. 1 and No. 2 in consideration of uses, regions, etc.

The general method for preparing heavy oil A produced mainly by oil refiners is to distill and recover several types of fractions, which are obtained by distilling crude oil and dividing it by boiling point, and catalytically cracking heavy fractions to lighten the components. The cut fractions are mixed at an appropriate mixing ratio in consideration of the application, consumption area, season, etc., and are used as base oils. There is.

This heavy oil base oil A is mainly composed of a distillate, and it is usually modified by adding various substances in order to satisfy the standard value of quality. In other words, it is a measure against the fact that the standard for residual carbon content (measured by JIS K2270), which is provided to distinguish the use from the light oil of similar composition, is specified higher than that of light oil.

Specifically, with light oil, the residual carbon content of 10% residual oil is 0.10% by mass.
In contrast to the following, heavy oil A is specified to have a residual carbon content of 4 mass% or less. In order to satisfy the standard value of residual carbon content of heavy fuel oil A, a by-product which is generated from a petroleum refining process and contains a large amount of residual carbon content (for example, residual oil and extraction during manufacturing of lubricating oil) The method of adding a small amount of the prepared component) is used.

As mentioned above, the composition of heavy fuel oil A is relatively similar to that of light oil, and it has the problem of low temperature fluidity as in the case of light oil.

For example, if the heavy fuel oil A is retained under low temperature conditions such as winter, fluidity may be significantly deteriorated due to precipitation of the wax component contained in the oil, which may cause a serious problem.
To give an example, in an internal combustion engine of a fishing boat, a fine screen installed in a filter for preventing foreign substances provided in the middle of a line for supplying fuel causes a wax clogging by a wax deposited on a fine screen, which causes the fuel to be discharged. In some cases, the fuel cannot be supplied, or at low temperatures, the fuel itself falls into a gelled state and loses its fluidity completely, making it impossible to operate the internal combustion engine.

The present invention pursues the problems of fuel oil as shown in heavy oil A and comprehensively examines the quality of the fuel oil to improve not only low-temperature fluidity but also hue and a fuel oil composition with a small amount of sludge generation. Is provided.

[Conventional technology]

Conventionally, various measures have been taken to improve the fluidity of fuel oil at low temperatures.

For example, there are methods such as heat retention and heating so that a decrease in air temperature does not directly cause a decrease in temperature of fuel oil, but improvements in equipment and a new energy cost burden are required.

There is also a method of mixing and diluting a kerosene fraction, which has excellent fluidity at a relatively low temperature, to reduce the amount of wax deposited. However, relatively light oils such as distillate for kerosene are in great demand and are indispensable for citizen's life, and therefore cannot be said to be a preferable method.

In the crude oil situation, which can be said to be the raw material for raw oil, imported crude oil has tended to become heavier in recent years due to the light crude oil preservation policy of the oil producing countries and the relatively high proportion of heavy crude oil in newly mined oil fields. On the other hand, under the situation where the need for light distillates is increasing, effective measures are indispensable for the purpose of producing a larger amount of light distillates such as the current light oil and heavy oil A from the viewpoint of effective utilization of petroleum resources. Is becoming.

On the other hand, although it was not originally used for the purpose of improving the low temperature fluidity, which is represented by the pour point (measured by JIS K2269) and the low temperature filtration plugging temperature (CFPP) (measured by IP-309), As a side effect, a method of adding the above-mentioned residual oil is known as a method capable of improving low temperature fluidity.

That is, like petroleum products such as heavy oil A,
% Residual carbon content of residual oil is high. When residual oil containing a large amount of residual carbon is added in order to satisfy the specified quality standard, low temperature fluidization is caused by the effect of the components contained in the residual oil. The fuel property is improved. Specifically, "Fuel Association Magazine" Vol. 57, No. 614 (Published in 1978) No. 419-42.
This is as described in page 4, or in JP-A-58-149991.

The effect of improving the low temperature fluidity by adding residual oil is
It is speculated that some of the substances contained in the residual oil are based on the effect of inhibiting the crystal growth of wax deposited from the fuel and the entanglement between the crystals, and thus preventing the gelation by the wax and oil.

However, the effect of improving the low temperature fluidity is not sufficient if only a small amount of residual oil is added, and if the amount of addition is increased to increase the effect, the asphalt content that is poorly soluble in the fuel contained in the residual oil will be increased. High molecular weight substances such as sludge precipitate and become sludge, which is a very fine strainer (generally in general) for preventing foreign substances provided near the room temperature, not in special low temperature conditions, for example, in the line of the fuel tank of a fishing boat and the internal combustion engine. The fibrous filter (pore size: 3 to 10 μm) may become clogged, making it difficult to supply fuel.

In addition, an increase in the amount of residual oil added to the fuel causes deterioration of the hue (black, opaque), and problems such as an increase in the consumer's anxiety caused by the appearance also occur, leading to a decline in commercial value. Become.

As another method for improving the low temperature fluidity of fuel oil,
There is a method of adding a fluidity improver. The majority of fluidity improvers are chemically synthesized products, and their role is to act when the wax content contained in fuel oil precipitates at low temperatures, preventing the wax from becoming huge and forming fine crystallites. It is intended to improve the fluidity by stabilizing as.

Many types of fluidity improvers have been proposed, and they are actually added to fuel oil to exert a great improvement effect.
Typical fluidity improvers are copolymers of ethylene and unsaturated esters, (co) of (meth) acrylic acid esters.
Examples include polymers, amidation products and salts synthesized from alkenyl succinic anhydride, which is the addition or copolymerization of maleic anhydride to α-olefin, and long-chain alkylamines, or ester compounds having long-chain alkyl groups. To be done.

Among them, many examples using a copolymer of ethylene and a vinyl ester of a saturated carboxylic acid have been proposed. For example, JP-B-39-20069, JP-B-48-23165, and JP-A-56-56
-141390, JP-A-58-129096, JP-A-59-8789, JP-A-59-136391 and the like.

Further, JP-B-60-33154 discloses an example showing a synergistic effect of improving low temperature fluidity by using a small amount of residual oil in combination with an ethylene-ethylenically unsaturated carboxylic acid ester copolymer.

Among the above-mentioned copolymers, the ethylene-vinyl acetate copolymer, in particular, not only lowers the pour point of fuel oil, but also
Since it is excellent in the effect of lowering the clogging temperature at low temperature,
In recent years, the amount used has been rapidly increasing, mainly for addition to light oil, but the effect is not satisfactory for fuels with small amounts of residual oil added.

[Problems to be solved by the invention]

As described above, a fuel oil mainly composed of heavy fractions in petroleum containing a required amount of residual carbon (for example, heavy fuel oil A)
In order to improve the low temperature fluidity, it is not preferable to add a large amount of residual oil in terms of hue and sludge generation amount, and the method of adding a low temperature fluidity improver to specific fuel oils is also recommended. Is only effective, or requires a large amount of addition despite being relatively expensive,
Not necessarily satisfactory.

Therefore, we searched for the optimum residual oil obtained from a specific crude oil, and added the required minimum amount to a fuel oil with a good hue, small sludge blockage, low temperature and low clogging temperature, and a specific ethylene It is an object of the present invention to provide a fuel oil composition in which the problems of conventional fuel oils (particularly class 1 heavy oils) are significantly improved by using a polymer to lower the pour point.

[Means for solving problems]

As a result of intensive studies to solve such problems, the present inventors have arrived at the present invention, and determined the optimum amount of residual oil obtained from a specific crude oil and the optimum amount of a specific fluidity improver. When used together, it provides a fuel oil with improved hue, reduced sludge generation, and improved low-temperature fluidity.

That is, the present invention provides: (A) a fuel oil composed of a large proportion of medium and / or heavy distillates of petroleum, and (B) a residual oil obtained by distilling a crude oil having a sulfur content of less than 1.0% by weight. % Residual carbon content of residual oil (measured by JIS K2270)
To be in the range of 0.1 to 0.4% by weight, and (C) ethylenically unsaturated ester monomer content 10 to 50
The present invention relates to a fuel oil composition characterized by being blended with 10 to 2,000 ppm by weight of an ethylene-ethylenically unsaturated ester copolymer having a number average molecular weight of 800 to 5,000.

Further, the present invention provides a fuel oil composition characterized in that the residual oil in the above fuel oil composition is atmospheric residual oil, and a fuel oil composition characterized in that the ethylenically unsaturated ester is vinyl acetate. It is about things.

The present invention will be described in detail below.

The medium and / or heavy oil fraction of petroleum used in the present invention is a distillate obtained by distilling crude oil under atmospheric pressure or reduced pressure, and has a boiling point converted to atmospheric pressure of about 180 to 450 ° C. It means something in the range. Specifically, kerosene, light oil, heavy oil, etc. are illustrated.

Further, regarding the residual oil used in the present invention, the residual oil is a generic term for heavy oil withdrawn from the bottom of the distillation column when crude oil is distilled in a petroleum refining process, and is referred to as distillate oil. Be contrasted. Residual oil is a residual oil obtained by distilling off light components by distillation, and therefore its boiling point is usually as high as 300 ° C or higher and it also has high viscosity.

Residual oil is the residual oil from atmospheric distillation of crude oil and has a boiling point of about 35.
Examples include atmospheric residual oil having a temperature of 0 ° C. or higher, and a vacuum residual oil having a boiling point of approximately 400 ° C. or higher obtained by further distilling the atmospheric residual oil under reduced pressure.

Atmospheric pressure residual oil is commonly called long-residue, and JIS K2205
It is used for petroleum products such as the second type (B heavy oil) and the third type (C heavy oil) among the heavy oils regulated in 1.

Vacuum residue oil is commonly called short residue and is used as a raw material for asphalt.

The residual oil used in the present invention is obtained from a specific crude oil as a raw material.

In general, crude oil contains about 0.01 to 5% by weight of a substance, which is quantified as a sulfur content, depending on the place of production and the oil well.

Among them, the crude oil selected for obtaining the residual oil suitable for the present invention is produced by distilling a crude oil containing less than 1.0% by weight of sulfur. Specific crude oil names include Millie Light, Tempungo, Labuan Light, Light Ceria, Champion, Arjuna, Ataca, Bunyu, Bukapai,
Handil, Sumbakun, Sawarachi, Maban etc. are illustrated.

Among the residual oils obtained from these crude oils, atmospheric residual oils are particularly preferable in consideration of ensuring appropriate amount stability, handleability and compatibility with petroleum and heavy fractions.

The components of the residual oil are not constant depending on the type of crude oil and the operating conditions of the distillation column, but are roughly divided into asphaltene, resin and oil. Since the components are different from each other, the effect of improving low temperature fluidity when added to fuel oil naturally changes. Therefore, the addition amount can be determined in consideration of this, but the hue is improved, the amount of sludge formation is suppressed, and the flowability is improved. In order to improve the low temperature fluidity by using it together with a performance improver, the residual carbon content of 10% residual oil measured by adding it to fuel oil was 0.1%.
An amount in the range of up to 0.4% by weight is preferred.

When the residual oil obtained by distilling crude oil containing 1.0 wt% or more of sulfur was added to the fuel oil, the hue deteriorated, and the effect of improving the low temperature fluidity by the combined use with the fluidity improver of the present invention was poor. It is not preferable.

Note that when distilling crude oil, two or more kinds of crude oil having different sulfur contents may be used as raw materials, but the sulfur content of the crude oil targeted by the present invention is the same as that of crude oil collected immediately before being fed to the distillation apparatus. It can be represented by sulfur content.

The ethylene-ethylenically unsaturated ester copolymer (hereinafter referred to as an ethylene copolymer) used in the present invention can be produced by a known method.

For example, it can be produced by free radical bulk polymerization, emulsion polymerization or solution polymerization. Among them, the free radical bulk polymerization method has an advantage that it can be produced without using a large amount of solvent. This method uses a continuous high-pressure polymerization apparatus at a pressure of 500 to 4,000 kg / cm ² and a temperature of 100 to 300 ° C. to produce a free radical group-forming polymerization catalyst such as α · α′-azobisisobutyronitrile. Such azo catalysts, tert-butyl peroxypivalate, tert-butyl peroxy 2-ethylhexanoate, di-tert-butyl peroxide, hydrogen peroxide, diethyl peroxide, persuccinic acid, alkali metals, alkaline earths Using a peroxygen type polymerization catalyst such as metal or ammonium persulfate, propane, butane, propylene, butene, propionaldehyde, methyl ethyl ketone, tetrahydrofuran, n-butyraldehyde, acetone, cyclohexane, methylcyclohexane, cyclohexanone, heptane, etc. In the presence of polymerization regulator ethylene and other A method of copolymerizing monomers.

Comonomers of ethylenically unsaturated ester copolymerized with ethylene include vinyl acetate, vinyl propionate,
Fatty acid vinyl esters such as vinyl butyrate, vinyl octanoate, vinyl stearate, or methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate, octyl methacrylate, acrylic Examples include alkyl esters of ethylenically unsaturated carboxylic acids, such as acrylic acid esters of stearyl acid stearyl and stearyl methacrylate, and methacrylic acid esters.
More than one seed is used.

The ethylene copolymer used in the present invention may be a single type, or may be a combination or a mixture with a type whose physical properties are changed by changing the production conditions.

Among the above ethylene copolymers, they are industrially easily available, and in terms of price and improvement of low temperature fluidity,
An ethylene-vinyl acetate copolymer is particularly preferred.

The comonomer content of the ethylene copolymer used in the present invention,
For the physical properties such as number average molecular weight, molecular weight distribution, and degree of branching, polymerization conditions such as reaction pressure, temperature, catalyst amount, type and amount of polymerization regulator, type and amount of comonomer, average residence time in reactor, etc. are selected appropriately. By doing so, a desired value can be obtained. Further, the characteristic ethylene copolymer can be obtained by the shape of the reactor, for example, a tank reactor with or without internal partition, a tubular reactor and the like.

In the present invention, when the ethylenically unsaturated ester monomer is vinyl acetate, its content is determined by the saponification method [the method described in “Japanese Industrial Standard (JIS) No. K6730” (1977) is helpful]. It is required, and the content of other monomers is described in infrared spectroscopy ["Polymer measurement method, structure and physical properties (2)", edited by the Society of Polymer Science, Baifukan, pp. 3 to 71, 1973. Is used as a reference].

Further, the number average molecular weight is determined by the vapor pressure osmotic pressure method [the method described in “Polymer Measurement Method, Structure and Physical Properties (1)”, Polymer Society of Japan, published by Baifukan 1973, pp. 57-75, is helpful]. It is what is done.

The comonomer content is preferably in the range of 10 to 50% by weight, and particularly preferably in the range of 25 to 40% by weight.

The comonomer content is less than 10% by weight, or
If it is more than 50% by weight, it may have poor solubility and precipitate when mixed with fuel oil. Further, it is not preferable because a large amount of addition is required to obtain a sufficient low temperature fluidity effect.

The number average molecular weight of the ethylene copolymer in the present invention is 800
It ranges from ~ 5,000. When the number average molecular weight is less than 800 or more than 5,000, it does not sufficiently act on the wax precipitated from the fuel oil, and the low temperature fluidity improving effect becomes poor. It is preferably 1,500 to 4,000.

The degree of branching of the ethylene copolymer in the present invention is expressed by "the number of methyl terminal side chains per 100 methylene groups in the main chain other than the methyl group of the ester group", and the nuclear magnetic resonance ( ¹ H NMR)
It is calculated by using the results obtained by the method (the method described in "Journal of the Chemical Society of Japan", 1980, No. 1, pp. 74 to 78).

That is, in the proton nuclear magnetic resonance spectrum,
The peak ratio between 0.85 ppm and about 1.45 ppm is obtained, and the ethylenically unsaturated ester monomer content and the number average molecular weight obtained by the vapor pressure osmometry are used for calculation. Incidentally, assuming that both terminals of the main chain methylene group are methyl groups and the side chains are all ethyl groups, two terminal methyl groups are subtracted to obtain the value.

In addition, the molecular weight distribution is determined by gel permeation chromatography (GP
C) method [reference is given to the method described in "Polymer Measurement Method, Structure and Physical Properties (1)", Polymer Society of Japan, Baifukan, pp. Pp. 76-89, 1973). W) / number average molecular weight (N) ratio.

The degree of branching of the ethylene copolymer used in the present invention is not particularly limited, and those having a degree of branching of about 1 to 20 which can be produced by relatively easy polymerization equipment are used. Particularly preferable effects are obtained.

Also, the molecular weight distribution is not particularly limited, and those having a relatively narrow molecular weight distribution of 4 or less, or those having a wide molecular weight distribution of 4 or more by mixing a plurality of ethylene copolymers are used, but 4 or less. Those having a molecular weight distribution of are particularly preferred. The ethylene copolymer used in the present invention is added in an amount of 10 to 2,000 ppm by weight with respect to the fuel oil composed of a large proportion of petroleum intermediate or / and heavy oil fractions.
Is suitable, and preferably about 30 to 1,000 ppm. More preferably, it is 50 to 500 ppm. If the addition amount is less than 10 ppm, only the addition effect within the error range can be expected, and if the addition amount exceeds 2,000 ppm, it is economically disadvantageous as compared with the effect obtained by the addition, which is not preferable.

There is no particular limitation on the method for adding the ethylene copolymer used in the present invention to a large proportion of the medium and / or heavy oil fractions,
The residual oil and the ethylene copolymer may be mixed in advance and then added to the heavy fraction in petroleum, or may be added separately.

Further, the residual oil and / or the ethylene copolymer can be added directly at room temperature or by heating, but it is usually easier to add them as a solution of 5 to 90 wt% by dissolving them in a suitable solvent. Good solubility in fuel oil. Aliphatic hydrocarbons and aromatic hydrocarbons can be used as the solvent, such as kerosene, light oil, aromatic solvent naphtha, light cycle oil (a fraction produced as a by-product from a petroleum cracking reformer), and aromatic hydrocarbons. Examples include high boiling point solvents having a high content.

In the method according to the present invention, rust preventives, antioxidants, antistatic agents, anticorrosives and the like usually added to petroleum fraction fuel oils may be used.

For the purpose of further improving low-temperature fluidity, other fluidity-improving agents such as chlorinated polyethylene, branched polyethylene, amide or amine salt of alkenylsuccinic acid, Friedel-Craft type hydrocarbon wax / naphthalate, and long-chain carboxylic acid are used. It may be used in combination with an ester with a nitrogen-containing compound containing a hydroxyl group (for example, triethanolamine behenic acid ester), an ester with a long-chain carboxylic acid and a compound containing a hydroxyl group (for example, ethylene glycol behenic acid ester), and a polyalkyl methacrylate. .

〔Example〕

The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

(1) Production of residual oil In a round-bottomed flask with an internal volume of 1,000 ml, 500 g of various crude oils with different residual carbon contents shown in Table 1 were put and distilled at atmospheric pressure. Was distilled off to obtain a residual oil. The results are shown in Table 2.

(2) Production of ethylene copolymer Various ethylene copolymers were produced under the conditions of ethylene and various comonomers, pressure, temperature, polymerization initiator and molecular weight modifier using a high pressure continuous reactor. Table 3 shows the polymerization conditions and the properties of the polymer.

(3) Adjustment and evaluation of fuel oil Specific gravity (15/4 ℃) 0.842, initial distillation temperature 202 ℃ by distillation test,
10% distillation temperature 245 ℃, 90% distillation temperature 340 ℃, end point 361 ℃, 10
% Residual carbon content of residual oil 0.00wt%, cloud point -3 ℃, CFPP-4
℃, pour point -7.5 ℃ distillate fuel oil, various residual oils produced in (1) and (2) and ethylene copolymer were added and mixed well, and allowed to stand for 24 hours or more, The quality was evaluated. Table 4 shows the composition of fuel oil to which various residual oils and / or ethylene copolymers were added, and the quality evaluation results thereof as Examples, Comparative Examples and Reference Examples.

In order to confirm the effect of the present invention, the quality of fuel oil was measured by the following method.

 Specific gravity According to JIS K 2249.

 Sulfur content According to JIS K 2541.

 Residual carbon content According to JIS K 2270.

 Residual carbon content of 10% residual oil According to JIS K 2270.

 Distillation test According to JIS K 2254.

 Cloud point According to JIS K 2269.

 Pour point According to JIS K 2269.

Cold Filter pluggin shown in CFPP (Low Temperature Filtration Clogging Temperature) IP-309 (UK 1976)
Automatic low temperature filtration clogging tester manufactured according to g Point of distillate fuels (A4F2 made by Yoshida Scientific Machinery Co., Ltd.)
Type).

Color ASTM color was measured according to JIS K 2580. However, in order to apply this test method, the test oil is deeply colored, so an equivalent volume dilution with a commercially available xylene reagent (ASTM color 0.5 or less) was used as the sample. The larger the measured value, the darker the color of the sample oil.

Sludge blockage test From the bottom of the beaker containing 1,000 ml of fuel oil to the suction port of the plunger type metering pump placed above, the inner diameter is 6 m.
The pipe is attached by a stainless steel conduit of m, 50 cm in length,
In addition, a stainless steel pipe with an inner diameter of 6 mm and a length of 50 cm with a Bourdon tube type pressure gauge installed in the center was vertically lowered from the outlet of the plaza type metering pump, and the lower end was marketed by Toyo Roshi Co., Ltd. Connect a stainless steel filter (SM162 60 type, filter inner diameter 100 mm, effective filtration area 60 cm ² ) commercially available from Carl Zeiss Co., Ltd. with a membrane filter with a pore size of 5.0 μm inserted. I set the vessel.

50 ml / hr by operating the plunger type metering pump at room temperature
The fuel oil was discharged to the receiver at the flow rate of 15 minutes, the pressure rise was measured, and the filter clogging by sludge was investigated.

From Reference Examples 1 to 10, the fuel oil without addition of the residual oil and / or the ethylene copolymer could not obtain the effect of sufficiently lowering the CFPP and / or the pour point, and the hue decreased when a large amount of the residual oil was used. Also, there is a large increase in pressure due to the sludge blockage test, indicating that the commercial value is poor.

On the other hand, the fuel oil compositions obtained by combining the specific residual oil according to the present invention with the specific ethylene copolymers shown in Examples 1 to 2 had a good hue, a small pressure increase due to the sludge clogging test, and the CFPP And there is a sufficient drop in pour point.

In addition, in the case of adding a large amount of residual oil or the combination of the residual oil and the ethylene copolymer other than the present invention shown in Comparative Examples 1 to 6, deterioration of hue and increase of pressure and / or decrease of CFPP by sludge clogging test were performed. There is a shortage.

(4) Table 5 shows the test results under different combination conditions of the residual oil and the ethylene copolymer of Examples 1 and 2.

According to Examples 3 to 8, in the combination of the specific residual oil and the specific ethylene copolymer according to the present invention, the hue is good, the pressure increase by the sludge clogging test is small, and the CFPP and the pour point are lowered. However, it is understood that the combination of the residual oil and the ethylene copolymer other than the present invention according to Comparative Examples 7 to 10 cannot sufficiently achieve the decrease in CFPP.

[Effects of the Invention] As described above, according to the present invention, by using the minimum amount of the residual oil obtained from the specific crude oil, the hue is good, the sludge clogging property is small, and in particular, the CFPP can be reduced, In addition, by using a specific ethylene copolymer, the phenomenon that the pour point can be lowered was discovered, and a fuel oil composition that greatly improves the problems of conventional fuel oils (particularly class 1 heavy oil) Can be provided.

Claims (4)

[Claims] 1. A fuel oil comprising (A) a large proportion of medium and / or heavy distillates of petroleum, and (B) 10 residual oil obtained by distilling crude oil having a sulfur content of less than 1.0% by weight. % Residual carbon content of residual oil (measured by JIS K2270)
To be in the range of 0.1 to 0.4% by weight, and (C) ethylenically unsaturated ester monomer content 10 to 50
A fuel oil composition comprising a blend of 10 to 2,000 ppm by weight of an ethylene-ethylenically unsaturated ester copolymer having a number average molecular weight of 800 to 5,000. 2. The fuel oil composition according to claim 1, wherein the residual oil is atmospheric residual oil. 3. The fuel oil composition according to claim 1, wherein the ethylenically unsaturated ester is vinyl acetate. 4. The fuel oil composition according to claim 3, wherein the vinyl acetate content is 25 to 40% by weight.