JPH0145516B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing pitch, which has excellent performance as a raw material for producing carbon fibers. Currently, carbon fiber is mainly manufactured using polyacrylonitrile as a raw material. However, when polyacrylonitrile is used as a raw material, there are disadvantages in that the raw material is expensive, the original fibrous shape is easily destroyed during heating and carbonization, and the carbonization yield is also poor. In recent years, focusing on this point, many methods have been reported for producing carbon fibers using pitch as a raw material.
When pitch is used as a raw material, it is expected that carbon fibers can be produced at low cost because the raw material is inexpensive and the carbonization yield is usually as high as 85 to 95%. However, carbon fibers obtained using pitch as a raw material have a higher modulus of elasticity than polyacrylonitrile carbon fibers, but have a problem in that they are inferior in strength. Therefore, if this problem could be solved and the modulus of elasticity could be further improved, it would be possible to produce carbon fibers with high strength and high modulus at low cost from pitch. Recently, commercially available petroleum pits have been heat-treated to obtain pits containing optically anisotropic liquid crystals called mesophases, and pitches containing this mesophases have been converted into precursor pits (hereinafter referred to as melt-spun). The pitch at the time is called the precursor pitch),
After melt-spinning this precursor pitch, it is made infusible and
Then, by carbonization or further graphitization,
It was reported that carbon fibers with improved elastic modulus and strength could be obtained (Japanese Patent Application Laid-open No. 19127-1983). However, whether a pitch can form a liquid crystal is determined by various factors, and the structure, softening point, viscosity, and other physical properties of the liquid crystal greatly depend on the raw material pitch. Said Japanese Unexamined Patent Application Publication No. 1973-
No. 19127 relates to a method for producing pitch containing mesophase (hereinafter abbreviated as mesophase pitch), but does not mention anything about the raw material pitch for forming high quality mesophase pitch. As mentioned above, a high-quality mesophase pitch largely depends on the raw material pitch, and if an optimal raw material pitch can be found, it will be possible to produce carbon fibers with even better elastic modulus and strength. Therefore, finding this optimal raw material pitch is an important challenge in this technical field. For example, coal tar pitch contains substances that are insoluble and infusible in carbon black quinoline, and these not only cause non-uniformity of the precursor pitch and deteriorate spinnability, but also reduce the strength and strength of carbon fibers. Adversely affects elastic modulus. On the other hand, many commercially available petroleum pitches and other synthetic pitches contain almost no substances that are insoluble and infusible in quinoline. Insoluble high molecular weight components are produced. In other words, when these pitches are heat-treated, thermal decomposition and polycondensation reactions occur simultaneously, and the low molecular weight components gradually increase in molecular weight.
It becomes a high molecular weight component that is insoluble in quinoline, and at the same time, the high molecular weight component further increases in molecular weight. At the same time, the softening point of pitch increases. If this quinoline insoluble matter is similar to the carbon black-like substance in coal tar, it will have an adverse effect on the steps after spinning as described above. Furthermore, even if the substance is different from the carbon black-like substance mentioned above,
The presence of a large amount of quinoline insolubles and a high softening point have an adverse effect on the melt spinning stage. That is, in order to melt-spun a precursor pitch, it is necessary to raise the spinning temperature until the precursor pitch reaches a viscosity that allows spinning, and if the softening point of the precursor pitch is too high, the spinning temperature will also increase. Naturally, it had to be expensive,
As a result, the molecular weight of the quinoline-insoluble components becomes higher, and the pitch is thermally decomposed to generate soft gas, making it impossible to form a uniform precursor pitch and making spinning virtually impossible. Thus, the precursor pitch must have a suitable viscosity for spinning with a relatively low softening point. Furthermore, it must not substantially contain volatile components during spinning or carbonization. For this reason, precursor pitch for carbon fiber production is prepared by removing the generated quinoline insoluble matter by means such as pressurization and solvent separation (Japanese Patent Application Laid-Open No. 47-9804, 50 −142820,
55-1342, 55-5954). however,
When these means are used, the processing equipment becomes complicated and the processing cost increases, which is not preferable from an economic point of view. It would be most preferable if a pitch having excellent performance could be used as the raw material pitch to prevent the formation of high molecular weight components that would become quinoline-insoluble components during the heating step of mesophase formation. The present inventors have completed the present invention as a result of intensive research into these problems. That is, the present inventors suppressed the formation of high molecular weight components at the stage of preparing the precursor pitch, had an optimal viscosity, and created a composition in which the aromatic planes were easily arranged in an orderly manner at the early stage of carbonization. We have discovered a raw material pitch with excellent performance. In other words, the present invention provides a method for producing a raw material pitch in which the softening point is kept relatively low and the mesophase is easily formed. The present invention will be explained in detail below. In the present invention, in producing carbon fiber by melt-spinning a precursor pitch obtained by heating a raw material pitch, and then subjecting it to infusibility treatment and carbonization or further graphitization treatment, the raw material pitch is (1) (2) heavy oil with a boiling point of 200°C or more obtained when petroleum is subjected to fluid catalytic cracking, and (3) heavy oil that is obtained by steam cracking of petroleum. Produced when heat-treating a fraction with a boiling point range of 160 to 400°C obtained when cracking and/or heavy oil with a boiling point of 200°C or higher obtained when steam cracking petroleum at a temperature of 380 to 480°C. A fraction with a boiling point range of 160 to 400°C is brought into contact with hydrogen in the presence of a hydrogenation catalyst, and 10 to 70% of the aromatic nuclei of aromatic hydrocarbons contained in the fraction are hydrogenated. This is a method for producing a raw material pitch for carbon fiber, characterized in that it is obtained by heat-treating a mixture with hydrogenated oil at a temperature of 370 to 480°C and a pressure of 2 to 50 kg/cm ² ·G. When the mesophase reaction is carried out using the raw material pitch obtained by the present invention, not only the production of quinoline-insoluble components is suppressed, but also the pitch is modified,
It was completely unexpected that the final product, carbon fiber, could have a high modulus of elasticity and high strength. On the other hand, when coal tar pitch, commercially available petroleum pitch, or synthetic pitch was heat-treated to form a mesophase according to the method of JP-A-49-19127, the resulting pitch had a softening point of 340°C or higher. thing,
In many cases, melt spinning was practically impossible, such as in cases where the solid content was precipitated, or even when no solid content was precipitated, the quinoline insoluble content reached 70 wt% or more. Furthermore, even if melt spinning is possible,
Furthermore, the strength of the carbon fiber obtained by infusibility, carbonization, and graphitization is 120 to 200 Kg/mm ² and the elastic modulus is 12 to 200 kg/mm 2
It was ^around 20ton/mm2. Furthermore, when a material having a softening point was spun, pores were present in the spun material due to the generation of thermal decomposition gas. The heavy oil with a boiling point of 200°C or higher obtained by steam cracking of petroleum used in the present invention refers to petroleum such as naphtha, kerosene, or light oil, which usually has a boiling point of 700°C or more.
It is a heavy oil that is produced as a by-product during the production of olefins such as ethylene and propylene by steam cracking at 1200°C, and it is a heavy oil with a substantially boiling point within the range of 200 to 450°C. The heavy oil with a boiling point of 200°C or higher obtained by fluid catalytic cracking of petroleum used in the present invention is:
Petroleum such as kerosene, light oil, or atmospheric residual oil is heated at 450 to 550℃ and at normal pressure to 20 kg/kg in the presence of a natural or synthetic silica/alumina catalyst or zeolite catalyst.
A heavy oil that is produced as a by-product when producing light oil such as gasoline by fluidized catalytic cracking at ^cm2・G, and has a boiling point substantially within the range of 200 to 450℃. be. The hydrogenated oil used in the present invention is naphtha,
Petroleum such as kerosene or light oil is usually heated to 700 to 1200℃.
Distillates with a boiling point range of substantially 160 to 400°C, preferably 170 to 350°C, which are produced as by-products when producing olefins such as ethylene and propylene by steam decomposition, and/or naphtha, kerosene, light oil, etc. A distillate with a boiling point of substantially 200°C or higher, preferably a boiling point range of 200 to 450°C, is a by-product produced when producing olefins such as ethylene and propylene by steam cracking petroleum products, usually at 700 to 1200°C. ℃ distillate temperature 380
When heated at ~480℃ and a pressure of 2~50Kg/ ^cm2・G for 15 minutes~20 hours, the boiling point range of the product is substantially
A fraction of 160 to 400°C, preferably 170 to 350°C is brought into contact with hydrogen in the presence of a hydrogenation catalyst to partially denucleate the aromatic nuclei of aromatic hydrocarbons contained in the fraction. It is hydrogenated. The hydrogenation catalyst used at this time may be a catalyst used in ordinary hydrogenation reactions, for example, using an inorganic solid such as bauxite, activated carbon, diatomaceous earth, zeolite, silica, titania, zirconia, alumina or silica gel as a carrier, copper etc. Metals from group B of the periodic table, such as chromium, molybdenum, cobalt, palladium, or platinum, supported on the carrier in the form of metals, or in the form of oxides or sulfides, are used. . Hydrogenation conditions vary depending on the type of catalyst used, but usually the temperature is 120 to 450°C, preferably 150 to 350°C, and the pressure is 20 to 100 Kg/cm ² G, preferably 30 to 70°C/ It is carried out in cm ²・G. Further, when the hydrogenation treatment is carried out in a batch manner, the appropriate hydrogenation treatment time is 0.5 to 3 hours. When carried out in a continuous manner, a space velocity (LHSV) of 0.5 to 3.0 is selected. To give an example of hydrogenation conditions, 2wt% Raney
When the process is carried out batchwise using nickel as a catalyst, the pressure is preferably 40 to 50 kg/cm ² G, the temperature is 160 to 170°C, and the treatment time is 1 to 1.5 hours. When using the formula, the pressure is 30-50Kg/ ^cm2・G, the temperature is about 330℃,
A space velocity (LHSV) of about 1.5 is preferably adopted. The aromatic nuclei of aromatic hydrocarbons contained in the fraction are partially hydrogenated by the hydrogenation reaction, and the nuclear hydrogenation rate at this time is preferably 10 to 70%.
It should be between 15 and 50%, most preferably between 15 and 35%. Incidentally, the nuclear hydrogenation rate is defined by the following formula, and the number of aromatic ring carbon atoms in the following formula is as indicated by ASTM D-2140-66. Nuclear hydrogenation rate = (number of aromatic ring carbons before hydrogenation treatment) - (
(Number of aromatic ring carbon atoms after hydrogenation treatment)/Number of aromatic ring carbon atoms before hydrogenation process The method for producing the raw material pitch of the present invention is as follows: (2) heavy oil with a boiling point of 200°C or more obtained when petroleum is subjected to fluid catalytic cracking; and (3) a fraction with a boiling point range of 160 to 400°C obtained when petroleum is steam cracked. Alternatively, in the presence of a hydrogenation catalyst, a distillate with a boiling point range of 160 to 400 °C, which is generated when heavy oil with a boiling point of 200 °C or more obtained when petroleum is steam cracked, is heat-treated at a temperature of 380 to 480 °C. is brought into contact with hydrogen to remove the aromatic nuclei of the aromatic hydrocarbons contained in the fraction.
It is obtained by mixing hydrogenated oil obtained by ~70% nuclear hydrogenation in a specific ratio and heat-treating it under specific conditions. The mixing ratio of component (1) and component (2) above is component (1):
Component (2) has a weight ratio of 1:0.1 to 9, preferably 1:
It is 0.2 to 4. The mixing ratio of component 3 is 0.1 to 2 times, preferably 0.2 to 1.5 times, the total weight of component (1) and component (2). The heat treatment temperature is 370 to 480°C, preferably 390 to 460°C. If the heat treatment temperature is lower than 370°C, the reaction progresses slowly and takes a long time, which is uneconomical. Further, heat treatment at a temperature higher than 480° C. causes problems such as caulking, which is not preferable. The heat treatment time is determined in consideration of the heat treatment temperature; when the temperature is low, the heat treatment is performed for a long time, and when the temperature is high, the heat treatment is performed for a short time. Usually 15 minutes to 20 hours, preferably 30 hours
Processing times ranging from minutes to 10 hours can be employed. Regarding the pressure, it can be carried out under any pressure, but it is preferable to use a pressure at which the active ingredients in the raw materials do not substantially distill out of the system unreacted.
~50Kg/cm ² ·G, preferably 5 to 30Kg/cm ² ·G is adopted. After the heat treatment, it is also preferable to remove light components by distillation or the like, if necessary. By using the raw material pitch of the present invention thus obtained, when heat-treated to form a mesophase, the production of high molecular weight components that are insoluble in quinoline is suppressed, and at the same time, the softening point of the pitch is prevented from increasing. Furthermore, it becomes a good precursor pitch having a composition in which the aromatic planes are easily arranged in an orderly manner. As a result, carbon fibers with extremely excellent elastic modulus and strength can be obtained. A known method can be used to produce carbon fiber using the raw material pitch obtained according to the present invention. That is, a raw material pitch is heat-treated to form a mesophase, the resulting precursor pitch is melt-spun, and then subjected to infusibility treatment and carbonization or further graphitization treatment to produce carbon fibers. The reaction at the stage of heat-treating the raw material pitch to convert it into a mesophase to obtain the precursor pitch is usually carried out at a temperature
It is carried out at 340 to 450°C, preferably 370 to 420°C, under normal pressure or reduced pressure and by bubbling inert gas such as nitrogen. The heat treatment time at this time is the temperature,
Although it can be carried out arbitrarily depending on conditions such as the amount of inert gas ventilation, it is usually carried out for 1 to 50 hours, preferably 3 to 20 hours. Inert gas ventilation rate is 0.7~
A pitch of 5.0 scfh/lb is preferred. As a method for melt-spinning the precursor pitch, known methods such as an extrusion method, a centrifugation method, and an atomization method can be used. The pitch fiber obtained by melt spinning is then subjected to an infusible treatment in an oxidizing gas atmosphere. As the oxidizing gas, one or more of oxidizing gases such as oxygen, ozone, air, nitrogen oxide, halogen, and sulfur dioxide gas are usually used. This infusibility treatment is carried out under temperature conditions at which the melt-spun pitch fibers to be treated do not soften or deform. For example 20~
Temperatures of 360°C, preferably between 20 and 300°C are employed. Further, the treatment time is usually 5 minutes to 10 hours. The infusible pitch fibers are then carbonized or further graphitized in an inert gas atmosphere to obtain carbon fibers. Carbonization is usually carried out at a temperature of 800-2500°C. Generally, the processing time required for carbonization is 0.5 minutes ~
It is 10 hours. Further, when graphitizing is carried out, it is carried out at a temperature of 2500 to 3500°C, usually for 1 second to 1 hour. In addition, during infusibility, carbonization or graphitization treatment,
If necessary, a slight load or tension may be applied to the object to be processed in order to prevent shrinkage, deformation, etc. The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 Heavy oil with a boiling point of 200°C or higher (hereinafter abbreviated as heavy oil (1)) was produced as a by-product when naphtha was steam cracked at 830°C.
The properties are shown in Table 1). Hydrotreated vacuum gas oil (VGO) of Arabian crude oil is heated to 500℃ using a silica/alumina catalyst.
A heavy oil (hereinafter referred to as heavy oil (2), whose properties are shown in Table 2) with a boiling point of 200° C. or higher was obtained by catalytic cracking. Next, add heavy oil (1) at a pressure of 15Kg/cm ²・G and a temperature of
After heat treatment at 400℃ for 3 hours, 250℃/1mmHg
The fraction (3) with a boiling point range of 160 to 400°C was collected. Its properties are shown in Table 3. This fraction (3) was brought into contact with hydrogen using a nickel-molybdenum catalyst (NM-502) at a pressure of 35 Kg/cm ² G, a temperature of 330°C, and a space velocity (LHSV) of 1.5, resulting in partial nuclear hydrogenation. was carried out to obtain hydrogenated oil (4). The nuclear hydrogenation rate was 31%. 60 parts by weight of the heavy oil (1), 30 parts by weight of heavy oil (2) and 100 parts by weight of hydrogenated oil (4) were mixed and heated to a pressure of 20 parts by weight.
Heat treatment was performed at a temperature of ⁴³⁰ ° C. for 3 hours.
This heat-treated oil is distilled at 250℃/1.0mmHg to remove light components, which have a softening point of 80℃ and a benzene-insoluble component of 22wt.
% raw material pitch was obtained. Next, add 550 g of nitrogen to 30 g of this raw material pitch.
Stir with ventilation at ml/min, heat treatment at 400℃ for 10 hours, softening point 280℃, quinoline insoluble content.
Pitch with a mesophase content of 80% and 33wt% was obtained. This pitch was melt-spun at 334°C using a spinner with a nozzle diameter of 0.3 mmφ and L/D = 2 to produce pitch fibers of 11 to 15μ, and further treated with infusibility, carbonization, and graphitization under the conditions shown below. Carbon fiber was obtained. The processing conditions for infusibility, carbonization and graphitization are as follows. ΓInfusibility conditions: 3 in air atmosphere up to 200℃
℃/min, heat at a rate of 1℃/min up to 300℃, and hold at 300℃ for 10 minutes. Γ Carbonization conditions: Temperature raised at 10℃/min in nitrogen atmosphere.
Hold at 1000℃ for 30 minutes. Γ Graphitization conditions: Heat treatment in an argon stream at a heating rate of 50°C/min to 2500°C. The obtained carbon fiber had a tensile strength of 258 Kg/mm ² and a Young's modulus of 42 ton/mm ² .

【table】

【table】

[Table] Comparative example 1 100 parts by weight of heavy oil (1) used in Example 1 and heavy oil
(2) Mixture with 50 parts by weight at a pressure of 15Kg/ ^cm2・G and a temperature of
Heat treatment was performed at 400°C for 3 hours. 250% of this heat treated oil
Distillation was carried out at ℃/1.0 mmHg to remove light components to obtain raw material pitch with a softening point of 49℃. Next, this raw material pitch was heat treated in the same manner as in Example 1, so that the softening point was 308°C and the quinoline insoluble content was 48°C.
Pitch with a mesophase content of 86% by weight was obtained. This pitch was melt-spun at 358°C using the spinning machine used in Example 1 to produce pitch fibers of 20 to 27μ, which were then subjected to infusibility, carbonization, and graphitization treatments in the same manner as in Example 1 to produce carbon fibers. Obtained. This carbon fiber had a tensile strength of 154 Kg/mm ² and a Young's modulus of 27 ton/mm ² . Comparative Example 2 Instead of the raw material pitch of the present invention used in Example 1, Ash land 240LS (softening point 120°C), which is a commercially available petroleum pitch, was used and heat treated in the same manner as in Example 1. As a result, pitch was obtained with a mesophase content of 50%. This pitch was subjected to melt spinning, infusibility treatment, carbonization and graphitization treatment in the same manner as in Example 1 to obtain carbon fibers. The obtained carbon fiber had a tensile strength of 137 Kg/mm ² and a Young's modulus of 28 ton/mm ² . Example 2 A fraction (4) with a boiling point of 160 to 400°C, which was produced as a by-product when naphtha was steam decomposed at 830°C, was collected. Its properties are shown in Table 4. This fraction (4) was treated with a cobalt-molybdenum catalyst (Ketsuchen Huain 124).
At temperature 330℃, pressure 35Kg/cm ²・G, LHSV1.0,
Partial nuclear hydrogenation was performed by contacting with hydrogen to obtain hydrogenated oil (5). The nuclear hydrogenation rate was 24%. Mix 100 parts by weight of heavy oil (1) used in Example 1, 50 parts by weight of heavy oil, and 220 parts by weight of hydrogenated oil (5),
Heat treatment was performed at a pressure of 15 kg/cm ² ·G and a temperature of 430° C. for 2 hours. This heat-treated oil was distilled under reduced pressure to remove light components to obtain raw material pitch with a softening point of 73°C. Next, this raw material pitch was heat treated in the same manner as in Example 1, with a softening point of 282°C and a quinoline insoluble content of 29wt.
% and a mesophase content of 83% was obtained. This pitch was melt-spun at 340°C using the spinning machine used in Example 1 to produce pitch fibers of 13 to 16 μm.
Infusible, carbonized and graphitized treatments were performed in the same manner as above to obtain carbon fibers. The tensile speed of this carbon fiber is
The weight was 255Kg/cm ² ·G, and the Young's modulus was 40ton/mm ² .

【table】

Claims (1)

[Claims] 1 After melt-spinning a precursor pitch obtained by heating a raw material pitch, infusibility treatment and carbonization or further graphitization treatment is performed to produce carbon fiber. (2) heavy oil with a boiling point of 200°C or higher obtained when petroleum is subjected to fluid catalytic cracking;
(3) A distillate with a boiling point range of 160 to 400°C obtained when steam cracking petroleum and/or a boiling point 200°C obtained when steam cracking petroleum.
A fraction with a boiling point range of 160 to 400 °C, which is produced when heavy oil with a temperature of 380 to 480 °C is heated, is brought into contact with hydrogen in the presence of a hydrogenation catalyst, and the fraction contained in the fraction is 10 to 70% of the aromatic nuclei of aromatic hydrocarbons
Temperature of the mixture with hydrogenated oil obtained by nuclear hydrogenation
A method for producing a raw material pitch for carbon fiber, characterized in that it is obtained by heat treatment at 370-480°C and a pressure of 2-50 Kg/cm ² ·G.