JPS6131158B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a latent anisotropic pitch, and more particularly, a method for producing a latent anisotropic pitch, and more specifically, a method for producing a latent anisotropic pitch, and more particularly, a method for producing a latent anisotropic pitch. The present invention relates to an industrially advantageous method for producing anisotropic pitches. Note that the potential anisotropic pitch referred to in this specification is
It is disclosed in Japanese Patent Application Laid-Open No. 100186/1986, which forms a homogeneous and optically isotropic single phase as a whole without substantially forming a mesophase in a molten state, and when an external force is applied, shows orientation in that direction,
It means a pitch whose H/C is 0.55 to 1.2. Generally, pitch has been used as a binder, pitch for impregnation, raw material for coke, raw material for artificial graphite, etc., but recently, in addition to these, its use as a raw material for carbon fibers has been attracting attention. Therefore, below, pitch as a raw material for carbon fiber will be mainly explained. Regarding pitch as a raw material for carbon fiber, initially optically isotropic (hereinafter simply referred to as isotropic) pitch was industrially adopted, but in recent years, optically anisotropic (hereinafter simply referred to as anisotropic) pitch has been adopted industrially. The use of pitch (called carbon fiber) as an industrial carbon fiber raw material is being considered. Isotropic carbon fiber obtained from isotropic pitch falls under the so-called low elastic modulus and low strength product from the viewpoint of mechanical properties, etc. On the other hand, isotropic carbon fiber obtained from anisotropic pitch Anisotropic carbon fibers are high-modulus, high-strength products, and exhibit properties comparable to high-performance carbon fibers obtained by heat-treating polyacrylonitrile or rayon under tension. Therefore, it is thought that anisotropic pitches will account for an increasing proportion of raw material pitches for carbon fiber production in the future, and much research is being focused on their production. Anisotropic pitches are generated in the process of heat treating isotropic pitches. In other words, the isotropic pitch is 350~
When heated to 450℃, reactions such as cyclization, aromatization, and polycondensation proceed in the pitch, forming anisotropic small spheres (spherulites) in the isotropic pitch matrix.
begins to appear. These anisotropic microspheres are composed of relatively high molecular weight hydrocarbons with a polycyclic and polynuclear skeleton, are composed of components with a high aromatic content, and are a type of liquid crystal with a nematic structure. Moreover, the spherules are mainly composed of quinoline-insoluble components, and by increasing the temperature or prolonging the treatment time, they gradually grow and then coalescence of the spherules occurs. Through this process, the entire pitch becomes to have an anisotropic structure, and the viscosity of the entire system increases significantly, eventually turning into coke. Microspheres or a phase of microspheres that exhibit this anisotropy are called memphaceous, and pitches that contain memphaceous or are mostly memphaceous are called memphaceous pitches. Conventional carbon fibers having an anisotropic structure are manufactured by spinning the membrane pitch described above, making it infusible, and carbonizing it. (Japanese Patent Publication No. 49-8634, Japanese Patent Application Publication No. 19127-1982, Japanese Patent Application Publication No. 65425-1972, Japanese Patent Publication No. 53-654-
119326, JP-A-54-160427) There are several difficult problems when manufacturing carbon fiber using memphace pitch as a raw material, but the fundamental problem is that the melting temperature and melt viscosity of the memphace component are generally This is due to the fact that the isotropic components forming the matrix are higher than those of the isotropic components. In other words, when a pitch containing memphace is melted at a relatively low temperature such that the matrix component exhibits a liquid state, memphace behaves like a solid phase and the entire system exhibits thixotropic behavior, making its spinning difficult. . On the other hand, if the memphaceous pitch is melted at a relatively high temperature at which it also melts, the memphaceous pitch will gradually increase its viscosity and eventually become coke since it is thermally unstable at such high temperatures. Ru. Particularly in pitches with a high memphace content, the rate of coke formation is high. This coking phenomenon makes continuous spinning difficult. In this way, when producing carbon fiber using membrane pitch as a raw material, the resulting carbon fiber exhibits anisotropy and has superior performance compared to carbon fiber obtained from isotropic pitch.
The fundamental problem is that melt spinning is difficult. On the other hand, a potentially anisotropic pitch was proposed in the aforementioned Japanese Patent Application Laid-open No. 100186/1986 as a pitch that fundamentally solved the drawbacks seen in the membrane pitch. This pitch is (a) a homogeneous one-phase pitch with good thermal stability, and (b) has a low melting temperature and low melt viscosity, so it can be heated up to 300°C.
It is a special pitch that can be spun at temperatures as low as: This potentially anisotropic pitch basically consists of a process in which a pitch containing at least 1% by weight of quinoline-insoluble matter is hydrogenated to obtain a hydrogenated pitch containing no quinoline-insoluble matter; It is manufactured by heat treating pitch at a temperature above its melting point. However, when such a method is examined from an industrial viewpoint, it has been found that there are practical difficulties in the hydrogenation step. That is, in this hydrogenation process, pitch containing quinoline-insoluble matter is used as the raw material to be treated, and this quinoline-insoluble matter is partially hydrogenated while retaining the basic skeletal structure of the polycyclic polynuclear material that can be a component of memphaceous acid. Since it is necessary to convert the quinoline into a soluble component, it is difficult to carry out hydrogenation efficiently, and conventional hydrogenation cannot produce industrially advantageous results. The present inventors have completed the present invention as a result of extensive research aimed at solving the above-mentioned problems encountered in the production of potentially anisotropic pitches. That is, according to the present invention, when producing a potentially anisotropic pitch, at least 1
% by weight of pitch was heated under hydrogen pressure in the presence of a non-acidic catalyst with an average pore diameter of 150 to 600 Å, which is a heat-resistant porous inorganic oxide support supporting a metal hydride component, and in the coexistence of an aromatic organic solvent. After hydrogenation under conditions of 30-250Kg/cm ² G and a reaction temperature of 250-380°C to convert the hydrogenated pitch into a hydrogenated pitch substantially free of quinoline insoluble matter, the obtained hydrogenated pitch is heated to 450 °C above its melting point.
A method of manufacturing a potentially anisotropic pitch is provided, which is characterized by heat treatment at a temperature of 0.degree. C. or less. The raw material pitch used in the present invention can be either petroleum-based or coal-based, but it is required to contain quinoline-insoluble content, and it is generally called mesophase pitch or anisotropic pitch. Pitches, or specific pitch components separated from these pitches, are also optionally employed. In addition, the pitch property used in the present invention has a H/C of 0.8
Below, it is usually in the range of 0.43 to 0.75. The quinoline insoluble content in pitch is at least 1% by weight, usually 1 to 90% by weight, preferably 3 to 90% by weight.
It is 40% by weight. If the quinoline insoluble content in the pitch is too low, the potential anisotropy of the resulting product will be weak, while if it is too high, it will be difficult to handle and it will be extremely difficult to carry out hydrogenation. Therefore, it becomes uneconomical. Furthermore, in the present invention, the raw material pitch can be hydrogenated in the form of a mixture with an organic solvent in order to facilitate its handling and smooth the hydrogenation. The smaller the particle diameter of the solvent-insoluble part is, the more preferable it is, and it is generally preferable that the particle diameter of the insoluble part at room temperature is 50 μm or less. In the present invention, the raw material pitch first includes:
It is subjected to a hydrogenation step, but in this case, as a catalyst, a heat-resistant porous inorganic oxide carrier supporting a hydrogenation metal with an average pore diameter of 150 to 600 Å, preferably
200-400Å, specific surface area ^10m2 /g or more, preferably
A material having physical properties of 70 m ² /g or more and a pore volume of 0.2 cc/g or more, preferably 0.3 cc/g or more is used. Note that the average pore diameter, specific surface area, and pore volume referred to in this specification refer to pores with a pore diameter of 75 Å or more, and are measured by the so-called mercury intrusion method using a Mercury Pressure Porosimeter. It was requested. In this case, the surface tension of mercury was 474 dyne/cm at 25°C, the contact angle used was 140°, and the absolute mercury pressure was varied from 1 to 2000 Kg/cm ² . The pore diameter of 75 Å or more at this time is expressed by the following formula. Pore diameter (Å) = 150000/absolute mercury pressure (Kg
/ ^cm2 ) The catalyst used in the present invention includes one formed by supporting a hydrogenation-active metal component on a non-acidic porous carrier. In this case, a non-acidic porous carrier means that when methyl red, which is used as an indicator for measuring the surface acidity of a catalyst carrier, is adsorbed onto the surface of the carrier, the methyl red becomes non-acidic, that is, neutral or basic. This refers to a porous carrier that develops a yellow color. Examples of such non-acidic porous carriers include silica, magnesium silicate, calcium silicate, magnesia, calcium oxide, barium oxide, rare earth oxides, alkali silicates, porous glass, etc.
Clay minerals having a double-chain structure mainly composed of magnesium silicate, preferably naturally occurring sepiolite, attapulgite, palygorskite, etc., can be used. Furthermore, as the catalyst carrier used in the present invention, a non-acidic porous inorganic oxide composed of a mixture of the above-mentioned non-acidic oxide and a clay mineral with a double-chain structure mainly composed of magnesium silicate is also preferably used. . As the hydrogenation catalyst used in the present invention, it is preferable to use one in which a hydrogenation-active metal component is supported on the non-acidic porous carrier, but even if an acidic porous carrier is used, the content of the acidic inorganic oxide is small,
Those that are not substantially acidic or those that have been neutralized with a basic compound such as amine, ammonia, or pyridine are applicable. For this neutralization treatment, in addition to the method of pre-treating the surface with a basic substance before using the catalyst, when hydrogenating pitch, a preliminary operation with a basic compound coexisting in the reaction system is used to neutralize the catalyst surface. There are methods to neutralize the catalyst surface, and methods to neutralize the catalyst surface using basic impurities contained in the raw material pitch. Therefore, in the present invention, acidic inorganic oxides,
For example, alumina, titania, boria, zirconia, alumina-magnesia, alumina-titania, silica-titania, alumina-zirconia,
A catalyst having silica-zirconia or the like as a carrier can also be applied after being subjected to the neutralization treatment as described above. The hydrogenation metal component supported on the carrier contains at least one transition metal selected from metals in Group B, Group B, and Group B of the periodic table, and particularly preferably vanadium. , molybdenum, tungsten, chromium, cobalt, nickel, copper, etc. These catalytic metal components are effective in any state such as a metal state, a metal oxide, a metal sulfide, or the like. Moreover, such a catalytic metal component may exist in a form in which part of the metal component is bonded to the catalyst carrier through ion exchange or the like. The content of this catalytic metal component, calculated as oxide, is approximately 0.1 to 30% based on the total weight of the catalyst.
% by weight. As mentioned above, the hydrogenation catalyst used in the present invention is
It is sufficient that it exists in a non-acidic state in the hydrogenation reaction system, and the presence of a non-acidic catalyst in the present invention means such a state. The hydrogenation treatment in the present invention is performed at a hydrogen pressure of 30 to 250 Kg/cm ² G, preferably 70 to 150 Kg/cm ² G, in conjunction with the use of the above-mentioned non-acidic catalyst (hereinafter referred to as non-acidic porous catalyst). Reaction temperature 250~380℃, preferably 300~350℃, hydrogen/raw material pitch ratio 100~
It is carried out under conditions of 5000 N/, preferably 1000 to 2000 N/, and a liquid hourly space velocity of 0.1 to 10 Hr ^-1 , preferably 0.25 to 1 Hr ^-1 . In order to obtain a potentially anisotropic pitch, in the hydrogenation process, the quinoline-insoluble content that forms memphaceous acid in the pitch is partially hydrogenated while retaining its basic skeleton, the polycyclic polynuclear structure, to form quinoline. The most important thing is to convert it into soluble matter. The quinoline-insoluble component is composed of hydrocarbons with a highly aromatic polycyclic and polynuclear structure, and constitutes the mesophase of membrane pitch. The quinoline-soluble polycyclic polynuclear structure hydrocarbon obtained by adding hydrogen is a factor in the potential expression of anisotropy. It is approximated by . Therefore, a hydrogenated pitch containing such a quinoline-soluble polycyclic polynuclear structure hydrocarbon does not substantially form memphaceous compounds in the molten state, and is entirely homogeneous and optically isotropic. Despite forming a phase, when an external force is applied, it becomes oriented in that direction. As mentioned above, in the hydrogenation process of the raw material pitch, it is required to hydrogenate the quinoline insoluble components that form memphace while maintaining its basic skeleton polycyclic polynuclear structure. The combination of non-acidic catalyst and reaction conditions used satisfies that requirement. That is, in the present invention, the hydrogenation treatment is carried out in the presence of a non-acidic catalyst, and the reaction temperature is 380°C or lower, preferably 300°C or lower.
Since a temperature of 350° C. was employed, the quinoline insoluble portion was hydrogenated while substantially retaining its basic skeleton structure. This is confirmed by the fact that the H/C of the hydrogenated pitch is higher than that of the raw material pitch and that the molecular weight distribution of the hydrogenated pit does not change significantly. When using an acidic catalyst such as silica-alumina as it is, compared to when using a non-acidic catalyst, the quinoline-insoluble components are more likely to coke and the desired purpose cannot be achieved, and the reaction temperature is 380°C. If the temperature is higher than 0.degree. C., coking of quinoline-insoluble components is similarly promoted, which is not preferable. Furthermore, in the present invention, 380
In order to maintain high hydrogenation activity for quinoline insolubles at temperatures below .degree. C., the average pore diameter of the catalyst is defined in the range of 150 to 600 Å, preferably 200 to 400 Å. When carrying out the hydrogenation step of the present invention, the raw material pitch is supplied in a state in which it is dissolved or suspended in an aromatic organic solvent. In this case, it is preferable to use an aromatic organic solvent that is highly aromatic and exists as a liquid in the hydrogenation reactor.
The aromaticity index fa (ratio of aromatic carbon number Ca to total carbon number C) of this aromatic organic solvent is 0.4 or more, preferably 0.5 or more, and its boiling point is in the range of 200 to 500°C. It is preferable that the Examples of such aromatic organic solvents include cycle oil obtained from a fluid catalytic cracker, heavy cracked oil obtained from an ethylene cracker, coal tar fraction (for example, anthracene oil), and various other substances. Examples include aromatic compounds. Specific examples of aromatic compounds in this case include, for example,
Examples include methylnaphthalene and dimethylnaphthalene. The mixing ratio of organic solvent to raw material pitch is usually 0.1 to 10 parts by weight of raw material pitch.
Parts by weight, preferably 0.5 to 5 parts by weight. The raw material pitch is supplied to the hydrogenation process in the form of a mixture with an aromatic organic solvent. In this case, the raw material pitch is mixed with the organic solvent by an appropriate method and then mixed with hydrogen gas or a hydrogen-containing gas. After that, it is preheated and introduced into the hydrogenation process. Further, the mixture of raw material pitch and organic solvent may be heated to a temperature not exceeding 200°C in order to promote dissolution of raw material pitch in the organic solvent. As the hydrogenation reaction method, any one of a suspended bed, an ebullated bed, and a fixed bed method may be employed, but a fixed bed is usually employed. Note that some raw material pitches already contain an aromatic solvent, and in such cases, it is not particularly necessary to add the aromatic solvent from the outside as described above. Next, a preferred embodiment of the hydrogenation process of the present invention is shown in which a catalyst containing magnesium silicate as the main component is used, and the hydrogen/raw material pitch ratio is 1000 to 100.
2000, temperature 300~350℃, hydrogen pressure 70~150Kg/ ^cm2
G, it is shown that the raw material pitch is hydrotreated under conditions of a liquid hourly space velocity of 0.25 to 1 Hr ^-1 . After the reaction product from the hydrogenation process is subjected to gas-liquid separation treatment,
A hydrogen-rich gas and a substantially liquid hydrogenation pitch are separated. In the present invention, the hydrogenation pitch is then heat treated. This heat treatment is carried out by holding the hydrogenated pitch in a molten state for a certain period of time, and the heat treatment temperature in this case is generally higher than the melting temperature of the hydrogenated pitch to 450°C, preferably 280 to 430°C. It is ℃. This heat treatment can be carried out under normal pressure or under pressure-controlled conditions throughout. Through this heat treatment, unstable substances remaining in the hydrogenation pitch are volatilized or partially dehydrogenated and converted into stable compounds.
A hydrogenated pitch with increased thermal stability is obtained.
In addition, it goes without saying that this heat treatment is carried out with care so that the membrane phase is not formed again in order to maintain the potential anisotropy of the hydrogenation pitch. This heat treatment not only improves the thermal stability of the hydrogenation pitch, but also reduces the partial dehydrogenation of quinoline-insoluble polycyclic and polynuclear hydrocarbons when they are excessively hydrogenated in the hydrogenation process. It gives an enhanced potential anisotropy development effect that can be easily oriented by external forces. When supplying the hydrogenation reaction product obtained in the hydrogenation process to the heat treatment process, after separating the aromatic organic solvent from the hydrogenation reaction product, only the obtained hydrogenation pitch should be supplied to the heat treatment process. However, as an alternative method, the hydrogenation reaction product containing the aromatic organic solvent can be directly fed to the heat treatment process, and the aromatic organic solvent can be separated by evaporation at the same time as the heat treatment of the hydrogenation pitch. . In the present invention, as described above, by treating the raw material pitch in a combination of a hydrogenation step and a heat treatment step, the hydrocarbon content of the polycyclic polynuclear structure that acts as a potentially anisotropic component can be adjusted. The pitch of the anisotropy can be obtained. The potentially anisotropic pitch of the present invention can be regarded as an isotropic pitch as a whole, but it contains a polycyclic polynuclear skeleton hydrocarbon with a carbon skeleton that can be a component of memphaceous acid. Therefore, it has latent orientation, and when an external force such as shearing force or stretching force is applied, optical anisotropy is observed indicating that the molecules are oriented in that direction, and carbonization and graphitization are observed. It is a pitch that has the property of exhibiting anisotropy during the process. The hydrocarbon component with a polycyclic polynuclear skeleton having a carbon skeleton that can be a constituent component of memphace is H/
A polycyclic polynuclear hydrocarbon existing in an aromatic pitch having C of 0.43 to 0.75, preferably 0.45 to 0.65 has a partially hydrogenated structure, and has a conventional anisotropic structure. It is similar to the hydrocarbons constituting memphace contained in pitch in that it has a polycyclic and polynuclear skeleton, but it is substantially soluble in quinoline,
They are clearly different in that they do not form memphaceous substances in the molten state and exist without phase separation. Therefore, the potential anisotropic pitch of the present invention including this is
Unlike the so-called anisotropic pitch containing membrane ace, it exhibits optical isotropy, forms a homogeneous single phase, has a low melting temperature, and has a low melt viscosity. Furthermore, since the pitch of the present invention has the above-mentioned potential anisotropy, for example, by melt-spinning it as a raw material,
When carbonized or graphitized, it has the characteristic of giving carbon fibers with an anisotropic structure. In addition, the pitch of the present invention is not only useful as a raw material for producing carbon fibers, but also has the advantage of being easily melted at low temperatures, having low viscosity as a melt, and having good thermal stability and low potential anisotropy. It can be applied to various fields by taking advantage of its characteristics such as being .
For example, it is used as a binder pitch, an impregnating pitch, and a raw material pitch for producing needle coke and various carbon materials that are relatively easily converted into graphite. Next, the present invention will be explained in more detail with reference to Examples. In addition, in the examples shown below, pitch A
is a petroleum pitch obtained by heat treating cracked oil obtained from a fluid catalytic cracker, and pitch B is
It is coal tar pitch. Table out their properties.
Shown in 1.

[Table] In addition, in the examples shown below, the catalysts used were made by extrusion molding using natural ore sepiolite having the chemical composition shown in Table 2 as a carrier material, and supporting Co and Mo on this. The chemical composition and physical properties of the catalyst are shown in Table 3.

【table】

【table】

[Table] Example 1 Mix 5 times the weight of α-methylnaphthalene with raw material pitch A, and mix this mixed oil with a hydrogen-rich gas at a flow rate of 20 c.c./Hr so that the hydrogen to oil ratio is 500 N/. After mixing, the mixture was preheated to 300°C using a preheater and supplied to the hydrogenation process. The hydrogenation step in this case is an upflow fixed bed reactor packed with the catalyst. reaction temperature 350
The hydrogenation conditions were adopted: °C, reaction pressure 140 Kg/cm ² G, LHSV 1 Hr ^-1 and H ₂ /oil ratio 500 N/. The obtained product is separated into hydrogen-rich gas and
The reaction product was separated into a substantially liquid reaction product. The liquid reaction product was distilled under reduced pressure of 25 mmHg to separate and remove the solvent component to obtain hydrogenated pit. The properties of the hydrogenated pitch thus obtained are shown in Table 4. As a result of compositional analysis of the solvent components by gas chromatography, no deterioration due to decomposition was observed. Table-4 Toluene insoluble content: 8.6 wt% Quinoline insoluble content: 0.0 wt% H/C (atomic ratio): 0.792 Sulfur content: 0.83 wt% Softening point: 34 °C Quinoline insoluble content conversion rate: 100 wt% Toluene insoluble content conversion Rate: 67% by weight The hydrogenated pitch obtained above was heated to 400% by weight in an inert atmosphere
After heating at °C for 1 hour, the mixture was kept under reduced pressure to remove trace amounts of low molecular components. The hydrogenated pitch heat-treated in this manner contained substantially no quinoline insoluble matter (0.3% or less), and its H/C was 0.76. When this heat-treated pit was viewed with a polarizing microscope, no memphaceous structure was observed, but by rubbing in one direction, strong polarized light was seen along that direction, indicating potential anisotropy. confirmed. For comparison, a commercially available desulfurization catalyst (Mo, Ni-
When the above-mentioned hydrogenation treatment was carried out in the same manner except that SiO ₂ ) was used, in this case, catalyst deterioration was so severe that substantial hydrogenation treatment could not be carried out. Table 5 Amount of metal supported MoO ₃ 4.0% by weight NiO 2.0% by weight Specific surface area 234 m ² /g Pore volume 0.63cc/g Average pore diameter 108 Å Example 2 15 times the weight of anthracene oil was mixed with raw material pitch B Hydrogenation was carried out under the same conditions as in Example 1, except that the material was heated to 150°C and filtered, and the precipitate was removed. The obtained liquid reaction product was distilled under reduced pressure of 5 mmHg to separate and remove the anthracene oil component to obtain hydrogenated pitch. The properties of this hydrogenated pitch are shown in Table 6. Table-6 Toluene insoluble matter: 9.4 wt% Quinoline insoluble matter: 0.2 wt% H/C (atomic ratio): 0.692 Softening point: 52°C Quinoline insoluble matter conversion rate: 97 wt% Toluene insoluble matter conversion rate: 75 wt% Above The hydrogenated pitch obtained in
After heating at °C for 1 hour, the mixture was kept under reduced pressure to remove trace amounts of low molecular weight components. The hydrogenated pitch thus heat-treated contained substantially no quinoline insoluble matter (0.3% or less), and its H/C was 0.67.
When this heat-treated pit was viewed under a polarizing microscope, no memphaceous structure was observed, but by rubbing in one direction, strong polarized light was seen along that direction, indicating that it had potential anisotropy. confirmed.

Claims (1)

[Claims] 1. When producing a potentially anisotropic pitch, a pitch containing at least 1% by weight of quinoline insoluble matter is prepared by supporting a metal hydride component on a heat-resistant porous inorganic oxide carrier, and the average pore diameter is 150
Hydrogenation was carried out in the presence of a non-acidic catalyst with ~600 Å, in the coexistence of an aromatic organic solvent, at a hydrogen pressure of 30-250 Kg/cm ² G, and at a reaction temperature of 250-380°C to substantially remove the insoluble components of quinoline. After converting this hydrogenated pitch into a hydrogenated pitch that does not contain
A method for producing a potentially anisotropic pitch characterized by heat treatment at a temperature of ℃ or less.