JPH0421718B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for improving the low-temperature fluidity of fuel oil prepared from heavy fractions of petroleum. As is well known, among the fractions obtained by distilling crude oil, there are especially those called medium and heavy fractions, which have a boiling point of about 150 to 150.
The 450°C fraction is used in large quantities as a variety of fuel sources, such as kerosene, light oil, and A-heavy oil. Among these, especially light oil and A heavy oil, under low temperature conditions such as winter, due to precipitation of wax contained in the oil, fluidity may be significantly deteriorated and serious problems may occur. For example, in order to prevent the wax contained in light oil from precipitating under cold winter conditions, a fine screen is built into a filter installed in the line that supplies light oil to diesel engines to prevent contaminants. In some cases, the fuel oil becomes clogged and the fuel oil cannot be supplied, and in the case of low temperatures, the fuel oil itself becomes gelled and loses its fluidity completely, making it impossible for the diesel engine to operate. There are many examples. In addition, in the case of heavy oil A, which is used to drive the engines of fishing boats, heating machines for greenhouse cultivation, heating of buildings, etc., similar wax precipitation causes combustion defects, which can have a serious impact on human life and property. I have something to give. The present invention relates to a method for improving the cold fluidity of these fuel oils. [Prior Art] Various measures have been taken to improve the fluidity of fuel oil at low temperatures. For example, there are methods such as insulation and heating that prevent a drop in air temperature from directly causing a drop in fuel oil temperature, but this requires equipment improvements and new energy costs. Another method is to mix and dilute a kerosene fraction, which has excellent fluidity at relatively low temperatures, to reduce the amount of wax deposited. However, relatively light oil such as kerosene distillate is in high demand and is essential to people's lives, so this method cannot be said to be preferable. In addition, regarding crude oil, which can be said to be the raw material for fuel oil, imported crude oil has tended to become heavier in recent years due to the policies of oil-producing countries to conserve light crude oil and the relatively high proportion of heavy crude oil in newly mined oil fields. On the other hand, with the increasing need for light distillates,
From the perspective of effective use of petroleum resources, the current diesel oil and A
Effective measures are becoming essential for the purpose of producing larger quantities of light distillates such as heavy oil. Another method aimed at improving the cold flow properties of fuel oil is the addition of flow improvers. The majority of fluidity improvers are chemically synthesized products, and their role is to act when the wax contained in fuel oil precipitates at low temperatures, preventing wax from becoming large and forming microcrystals. The aim is to improve fluidity by stabilizing the Many types of fluidity improvers have been proposed.
Furthermore, it has actually been added to fuel oil and has shown great improvement effects. Typical fluidity improvers include copolymers of ethylene and unsaturated esters, (co)polymers of (meth)acrylic esters, addition of maleic anhydride to α-olefins, or copolymerized alkenyl succinic acids. Examples include amidates and salts synthesized from anhydrides and long-chain alkyl amines, and ester compounds having long-chain alkyl groups. Among these, many examples using copolymers of ethylene and vinyl esters of saturated carboxylic acids have been proposed. For example, Special Publication No. 39-20069, Special Publication No.
No. 48-23165, JP-A-56-141390, JP-A-58-
No. 129096, JP-A-59-8789, JP-A-59-136391
It is stated in the issue bulletin etc. Among the above-mentioned copolymers, ethylene-vinyl acetate copolymer (hereinafter referred to as EVA) has been used in recent years because it not only lowers the pour point of normal fuel oil but also has an excellent effect of lowering the clogging temperature of low-temperature filters. This usage is rapidly increasing. [Problems to be solved by the invention] However, in these fluidity improvers, n-
Effective for fuel oils containing large amounts of paraffin and fuel oils with a very narrow boiling point range (for example, fuel oils with a temperature difference of 130°C or less between 90% distillation temperature and 10% distillation temperature). Although it is difficult to handle and requires a large amount of addition even though it is relatively expensive, it is not always satisfactory, and improvements have been desired. The fluidity improver has little effect on preventing wax from precipitating when the fuel oil is cooled, but it prevents the precipitated wax from growing into huge crystals and keeps it as fine crystals. Even if wax precipitates in cold conditions, it can be smoothly circulated through fine piping in fuel oil consuming equipment, wire mesh strainers, etc. Taking EVA as an example, its chemical structure and its interaction with wax are estimated to behave as follows. Molecular structure of EVA The molecular structure of EVA varies slightly depending on its manufacturing method, but the following physical properties are particularly important when looking at its interaction with wax. Namely, the chain length of polymethylene units based on ethylene polymerization (ethylene content), acetoxy branching based on vinyl acetate polymerization (vinyl acetate content), alkyl branching based on chain transfer reactions in ethylene polymerization (branching degree), and molecular weight. , molecular weight distribution, etc. These physical properties differ depending on conditions such as the polymerization method (solution system or gas phase system, batch system or continuous system, etc.), comonomer feed amount and ratio, type of molecular weight regulator, polymerization temperature, etc. It is well known that according to the radical polymerization method, the copolymer composition of ethylene and vinyl acetate has random bonds rather than block bonds. Fuel oil and precipitated wax Fuel oil produced as light oil or A heavy oil is mainly a distillate of crude oil, and is usually a mixture of components having a fairly wide boiling point range, depending on the operating conditions of the distillation equipment. A typical manufacturing method involves mixing intermediate products that have been distilled into several types or recovered from other petroleum refining processes, taking into consideration the season and region of consumption. It is known that when the produced light oil and A heavy oil are cooled to a low temperature, components with a high carbon number precipitate out as wax, and the main component thereof is n-paraffin. The largest number of carbon atoms in n-paraffin that precipitates under normal practical low-temperature conditions is about 35, while the smallest is about 15. However, depending on the manufacturing method of light oil and A heavy oil, the mixing ratio of intermediate products, etc., the precipitation temperature and amount of wax and the carbon number distribution of n-paraffin in the precipitated wax vary greatly, and the fluidity This may have a significant effect on the effectiveness of the enhancer. Interaction between EVA and wax Various mechanisms of action have been proposed in which EVA acts on wax precipitated from fuel oil, preventing the wax from forming giant crystals and maintaining it as a fine crystal.
It can be roughly explained in the following way. Wax nucleation effect due to polymethylene chains Before the fuel oil cools and wax precipitation begins, or almost simultaneously, the polymethylene chains in EVA become wax crystal nuclei and precipitate, and this stimulates the precipitated wax to become crystal nuclei. They adhere one after another to form crystals. In this case, the chain length of the polymethylene unit that can act as a crystal nucleus is important, and at the same time, the molecular weight distribution, degree of branching, and molecular weight of EVA, which can correspond to the wax precipitation rate, are also factors that affect the temperature at which it can act as a crystal nucleus. Growth of Wax Crystals As the fuel oil is further cooled, waxes with lower carbon numbers precipitate one after another and adhere to the large number of fine crystal particles generated above, causing individual crystals to gradually grow. Inhibition of wax crystal growth by acetoxy branching The acetoxy branching in EVA has a different structure from n-paraffin, which is the main component of wax.
It has the effect of inhibiting the growth of wax crystals due to steric hindrances or differences in electrical polarity.
As a result, the crystal growth rate is significantly suppressed and giant crystallization is prevented. In order to sufficiently obtain this growth inhibiting effect, it is preferable to have as many acetoxy branches as possible; however, if the number of acetoxy branches is increased, the number of polymethylene chains mentioned above will be reduced, which is contradictory. Therefore, it is necessary to select an appropriate balance between polymethylene chains and acetoxy branches. Above, we have described the effects of fluidity improvers on wax precipitated from fuel oil from a structural perspective, but in reality, the wax precipitation temperature and its composition are not constant depending on the composition of fuel oil. The effect of improving sex was difficult to obtain. For example, even if an ethylene-ethylenically unsaturated ester copolymer (e.g. EVA) as described in Japanese Patent Publication No. 48-23165 is added to light oil or heavy oil A, there are cases where the effect is obtained and cases where it is not. It was found that mere control of molecular weight, ester content, and degree of branching was insufficient. Furthermore, even if an ethylene-ethylenically unsaturated ester copolymer (e.g. EVA) as described in JP-A No. 59-8789 is added to light oil or heavy oil A, there are cases where the effect is obtained and cases where it is not. It was found that simple control of molecular weight, ester content, degree of branching, and molecular weight distribution was insufficient. In other words, the fluidity improver can act effectively when wax precipitates from fuel oil (wax nucleation effect), and the fluidity improver can act when wax deposits one after another and grows into crystals (wax growth inhibition). (effect) is important, and for this purpose, satisfactory effects can only be obtained if the understanding of the properties of the fuel oil and the control of the physical properties of the fluidity improver are well matched. The purpose of the present invention is to take into account the fact that the properties of fuel oil, the physical properties of fluidity improvers, and their effects have not been fully understood in the past.
The object of the present invention is to provide a method for obtaining extremely effective low-temperature fluidized fuel oil by understanding the optimal fuel oil properties and the optimal physical properties of a fluidity improver. [Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive studies to solve the problems, and have achieved the present invention as shown in Japanese Industrial Standard (JIS) No. K2254 (1980). By identifying the properties of the fuel oil from various distillation temperatures in the distillation properties measured using a method using It is possible to obtain an effective low-temperature fluidized fuel oil, and the present invention has been achieved. That is, the present invention consists of a large proportion of medium and/or heavy fractions of petroleum, and has a distillation temperature of 90% and a temperature of 10%.
% distillation temperature difference is 130℃ or less, and the initial boiling point is 160℃ or more and the final point is 390℃ or less, and the ethylenically unsaturated ester monomer content is 27~ 40% by weight, number average molecular weight 1400-2900,
The molecular weight distribution is 4 or less, and the degree of branching is 6 or less methyl terminal side chains (hereinafter referred to as the degree of branching) per 100 methylene groups in the main chain in addition to the methyl groups of the ester group. Ethylene-ethylenically unsaturated ester copolymer (hereinafter referred to as ethylene copolymer) is
The present invention relates to a method for improving the low-temperature fluidity of fuel oil, which is characterized by adding 2000 ppm. Furthermore, the present invention relates to the improved method described above, characterized in that the ethylenically unsaturated ester is vinyl acetate. 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. K6780" (1977) is used as a reference]. Other monomer contents can be determined by infrared spectroscopy [“Polymer Measurement Methods, Structure and Physical Properties (Part 2)” edited by The Society of Polymer Science and Technology, published by Baifukan in 1971, pp. 8-71. The method described in 2013 is a reference.] In addition, the number average molecular weight can be determined by the vapor pressure osmotic pressure method [the method described in "Polymer Measurement Methods, Structure and Physical Properties (Part 1)" edited by the Society of Polymer Science, published by Baifukan in 1971, pp. 57-75 is a good reference]. Molecular weight distribution is determined by gel permeation chromatography (GPC) method [described in "Polymer Measurement Method, Structure and Physical Properties (Part 1)" edited by The Society of Polymer Science, published by Baifukan in 1971, pp. 76-89. Weight average molecular weight (MW) / number average molecular weight (MN) in terms of standard polystyrene
It is determined from the ratio. Furthermore, in the present invention, the degree of branching is expressed as "the number of methyl-terminated side chains per 100 methylene groups in the main chain other than the methyl groups of the ester group", and is expressed by nuclear magnetic resonance (H
NMR) method (Journal of the Chemical Society of Japan, 1980, No. 1,
Calculated using the results obtained using the method described on pages 74 to 78 (for reference). That is, the peak ratio of 0.85 ppm and 1.45 ppm in the proton nuclear magnetic resonance spectrum was determined, and the content of ethylenically unsaturated ester monomer,
It is calculated using the number average molecular weight determined by vapor pressure osmotic pressure method. Assuming that both ends of the main chain methylene group are methyl groups and all side chains are ethyl groups, the value is determined by subtracting the two terminal methyl groups. The present invention will be explained in detail below. The medium and/or heavy oil fraction of petroleum used in the present invention refers to distillate oil obtained by distilling crude oil under normal pressure or reduced pressure, and has a boiling point of 130% when converted to normal pressure.
It is in the range of ~450℃. This distillate oil can be used as it is, mixed in an appropriate ratio, or if necessary mixed with a small amount of non-distillate oil (distillation pot residual oil) obtained by distillation under normal pressure or reduced pressure. It is commercially available as type 1 (A heavy oil) under the JIS) numbers K2203 (kerosene), K2204 (light oil), and K2205 (heavy oil), and the temperature difference between 90% distillation temperature and 10% distillation temperature is A fuel oil is used that has a distillation property of 130°C or lower, an initial boiling point of 160°C or higher, and a final boiling point of 360°C or lower. Various ethylene copolymers used in the present invention can be produced by known methods. For example, they can be produced by free radical bulk polymerization, emulsion polymerization or solution polymerization. Among these, the free radical bulk polymerization method has the advantage that it can be produced without using a large amount of solvent. This method uses a continuous high-pressure polymerization device at a pressure of 500 to 4000 Kg/cm ² and a temperature of
Free radical group-forming polymerization catalysts under conditions of 100 to 800°C, such as azo catalysts such as α・α′-azobisisobutyronitrile, tertiary butyl peroxy pivalate, tertiary butyl peroxy 2- Propane, propane This is a method of copolymerizing ethylene and other comonomers in the presence of a polymerization regulator such as butane, propylene, butene, propionaldehyde, methyl ethyl ketone, tetrahydrofuran, n-butyraldehyde, acetone, cyclohexane, methylcyclohexane, cyclohexanone, heptane, etc. Ethylenically unsaturated ester comonomers copolymerized with ethylene include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octoate,
fatty acid vinyl esters such as vinyl stearate,
or methyl acrylate, methyl methacrylate,
Acrylic esters such as ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate, octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, stearyl acrylate, stearyl methacrylate, methacrylate esters, etc. Ethylene Examples include alkyl esters of unsaturated carboxylic acids,
One or more of these may be used. The ethylene copolymer used in the present invention may be one type, or may be used in combination or in a mixture with other types whose physical properties are changed by changing manufacturing conditions. Among the above-mentioned ethylene copolymers, ethylene-vinyl acetate copolymers are particularly preferred from the viewpoint of industrial availability, cost, and ability to improve low-temperature fluidity. Physical properties such as comonomer content, number average molecular weight, molecular weight distribution, and degree of branching of the ethylene copolymer used in the present invention are determined by polymerization conditions, such as reaction pressure, temperature, amount of catalyst, type and amount of polymerization regulator, and type of comonomer. A desired value can be obtained by appropriately selecting the amount, average residence time in the reactor, etc. Furthermore, a characteristic ethylene copolymer can be obtained by changing the shape of the reactor, for example, a tank reactor with or without internal partitions, a tubular reactor, etc. The comonomer content is suitably in the range of 5 to 50% by weight, particularly preferably in the range of 15 to 40% by weight. More preferably, it is in the range of 20 to 30% by weight. If the comonomer content is less than 5% by weight or greater than 50% by weight, the solubility may be poor and sedimentation may occur when mixed with fuel oil. In addition, it is not preferable that a large amount of the additive be added in order to obtain a sufficient low-temperature fluidity effect. The number average molecular weight is preferably in the range of 800 to 2900.
Number average molecular weight is less than 800 or 2900
If it is larger than , it will be difficult to act sufficiently on wax precipitated from fuel oil, and the effect of improving low-temperature fluidity will be poor. The molecular weight distribution is preferably 4 or less. When the molecular weight distribution is larger than 4, the proportion of components that do not act on the wax precipitated from fuel oil increases, and the effect of improving low-temperature fluidity becomes poorer than that of an ethylene copolymer having a molecular weight distribution of 4 or less. The degree of branching is usually 15 or less, particularly preferably 6 or less. The greater the degree of branching, the weaker the effect of keeping wax precipitated from fuel oil in a fine state, resulting in a poorer low-temperature fluidity improvement effect. The amount of the ethylene copolymer used in the present invention is:
For fuel oil consisting of a large proportion of medium and/or heavy oil fractions of petroleum, a range of 10 to 2000 ppm by weight is appropriate, preferably about 30 to 1000 ppm. If the amount added is at the end of 10 ppm, the effect of addition can only be expected within the error range, and if it is added in excess of 2000 ppm, it will be economically disadvantageous compared to the effect obtained by adding it, so it is not preferable. There is no particular restriction on the method of adding the ethylene copolymer used in the present invention to a large proportion of medium and/or heavy oil fractions, and the ethylene copolymer can be added directly at room temperature or heated. Usually, it is easier to add it by dissolving it in an appropriate solvent and adding it as a 5 to 90% by weight solution, and it has better solubility in fuel oil. As the solvent, aliphatic hydrocarbons, aromatic hydrocarbons, etc. can be used, such as kerosene, light oil, aromatic solvent naphtha, light cycle oil (a fraction produced by petroleum cracking and reforming equipment), and aromatic hydrocarbons. Examples include high-boiling point solvents with high content. The method according to the present invention has an excellent effect of lowering the clogging temperature of low-temperature filtration filters of fuel oil compared to conventional methods using fluidity improvers, etc., and is particularly effective in lowering the clogging temperature of fuel oils containing relatively large amounts of n-paraffin. It is suitable as a method for improving the low-temperature fluidity of fuel oils and fuel oils with narrow boiling point ranges. In the method according to the invention, rust inhibitors, antioxidants, antistatic agents, anticorrosion agents, etc. that are commonly added to petroleum distillate fuel oils may be used. In addition, for the purpose of further improving low-temperature fluidity, other fluidity improvers such as chlorinated polyethylene, branched polyethylene, amides or amine salts of alkenylsuccinic acids, Friederk-Crafts type hydrocarbon waxes and naphthalates, and long-chain carboxylic acids may be used. It may be used in combination with esters with hydroxyl group-containing nitrogen compounds, polyalkyl methacrylates, and the like. [Example] The present invention will be specifically explained below using Reference Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. (1) Production of ethylene copolymers Various ethylene copolymers were produced using ethylene and the comonomers, pressures, temperatures, polymerization initiators, and molecular weight regulators shown in Table 1 using a high-pressure continuous reactor.
Table 2 shows the properties of the obtained ethylene copolymer. (2) Adjustment and evaluation of fuel oil Fuel oils (a) and (b) shown in Table 3 (both n-
Each of the various ethylene copolymers A to L produced by the above method was added to the paraffin content (approximately 20%).
After adding 200 ppm and dissolving it, its low temperature fluidity was measured. The low-temperature fluidity was measured using an automatic filtration clogging point tester [manufactured by Yoshida Scientific Instruments Co., Ltd., A4F2] manufactured in accordance with the low-temperature filtration clogging point test method specified in IP-309 (1976 UK). It was done in a mold. The measurement results are shown in Table 4 as an example and in Table 5 as a comparative example. Regarding the fuel oil (c) having a relatively narrow boiling point range, 250 ppm of each of the ethylene copolymers A to L shown in Reference Examples were added and dissolved, and the low temperature filtration clogging temperature was measured. The results are shown in Table 6. In addition, the temperature difference between the 90% distillation temperature and the 10% distillation temperature shown in Table 3 is outside the range specified by the present invention.
250 ppm of each of the ethylene copolymers A to N shown in the reference example was added and dissolved in fuel oil (d) at 135°C, and the low-temperature filtration clogging temperature was measured. It is shown in Table 7. Note that the temperature at which the low-temperature filtration clogging temperature decreases, which was observed due to the addition of the fluidity improver, is also indicated as △CFPP. From Tables 4 to 7, it can be seen that the examples according to the present invention have lower low-temperature filtration clogging temperatures and excellent low-temperature fluidity than the comparative examples. In particular, it can be seen that it has a remarkable effect on fuel oils (a), (b) and (c) having the distillation properties specified in the present invention. That is, as is clear from Table 7, for fuel oil (d) whose distillation properties are outside the range specified in the present invention, copolymers A, B, and D specified in the present invention are used.
It cannot be said that even F and H have a remarkable effect, and H, I, K, etc., which have higher molecular weights, are preferable as copolymers. [Effects of the Invention] As explained above, according to the present invention, by adding an ethylene-ethylenic unsaturated ester copolymer having specific physical properties to fuel oil having specific distillation properties, extremely favorable It has been found that it is possible to provide a fuel oil with excellent low-temperature fluidity, and the effect is significant in producing industrially stable and good fuel oil.

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Claims (1)

[Claims] 1. Consisting of a large proportion of medium and/or heavy fractions of petroleum, having distillation properties in which the temperature difference between 90% distillation temperature and 10% distillation temperature is 130°C or less, and Station point is 160
℃ or higher and the end point is 390℃ or lower, the content of ethylenically unsaturated ester monomer is 27 to 40% by weight,
Ethylene-ethylenically unsaturated ester having a number average molecular weight of 1400 to 2900, a molecular weight distribution of 4.0 or less, and a degree of branching of 6 or less methyl terminal side chains per 100 methylene groups in the main chain in addition to the methyl groups of the ester group. A method for improving the low-temperature fluidity of fuel oil, characterized by adding 10 to 2000 ppm of a copolymer. 2. The improved method according to claim 1, wherein the ethylenically unsaturated ester is vinyl acetate.