JPS62256887A - Production of raw pitch for carbon fiber - Google Patents

Abstract

PURPOSE:To obtain a large amount of the title pitch capable of providing a final product, i.e. a carbon fiber, having a high strength and a high modulus of elasticity from which fine particles have been removed with a high efficiency, by treating a high-boiling oil derived from petroleum with a high gradient magnetic separator and heat treating the treated oil. CONSTITUTION:A boiling oil having a b.p. of 200 deg.C or above which contains about 10-550ppm of fine particles containing iron and compds. of iron, Ni, V, etc. having a particle diameter of 0.1-100mum is treated with a high gradient magnetic separator to obtain a high-boiling oil of which the content of the residual fine particles having a particle diameter of 0.5mum or less has been reduced to 5ppm or less. The treated high-boiling oil is heat treated at 380-480 deg.C under a pressure of 2-50kg/cm<2> and then treated by e.g., thin film distillation method at 250-500 deg.C under a reduced pressure of 5mmHg or less for 5min-30hr, thereby removing a low boiling component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing carbon m miscellaneous raw material pitch. In particular, the present invention provides a method for producing bits with improved performance for carbon fiber raw materials by removing fine particles present in heavy oil using a specific method.

BACKGROUND OF THE INVENTION It is known to produce carbon fibers from pitch. In particular, petroleum pitch is heat-treated to obtain a mesophase pitch containing optically anisotropic liquid crystals, which is melt-spun into pitch TA fibers and then subjected to infusibility treatment, followed by carbonization treatment or further graphite treatment. It is known that carbon fibers with high strength and high elastic modulus can be obtained by chemical treatment (Japanese Patent Publication No. 59-3567).

Problems to be Solved by the Invention However, carbon fibers obtained using pitch as a starting material are superior in elastic modulus but inferior in tensile strength compared to polyacrylonitrile carbon ta4iN, so improvements are desired.

Petroleum-based heavy oil contains various fine particles, and so-called decant oil obtained by fluid catalytic cracking of petroleum contains catalyst residues and the like. If these fine particles remain in the spinning pitch, they will not only clog the spinneret during melt spinning and make stable spinning difficult, but they will also reduce the tensile strength of the carbon fibers. This is a contributing factor.

Therefore, it is expected that if these fine particles can be removed from heavy oil, it will be possible to obtain carbon fibers with improved tensile strength.

However, since the particle size of the fine particles is usually extremely small, 01 to 30 microns, it is impossible to remove them using filters used in the petroleum refining industry. One possible method for removing these particles is to use a fine-mesh filter such as a filter paper or a membrane filter, but when these filters are used, the pressure loss is large and clogging occurs, resulting in long operation times. It is difficult to replace it, and even if it were to be replaced, it is not suitable for large-scale processing due to operational reasons.

A method of removing particles using a centrifuge has also been proposed, but there is a problem with the throughput, and furthermore, the removal rate of fine particles is not necessarily sufficient (1), and further improvements are desired.

As a result of intensive research, the inventors of the present invention have conducted intensive research to solve the above-mentioned problems.By treating petroleum-based heavy oil with a high gradient magnetic separator, the fine particles in the lI heavy oil can be removed. It has been discovered that it can be removed with extremely high efficiency. Furthermore, this method has the advantage of extremely high throughput.

In other words, the present invention eliminates the flow of petroleum! ] Catalytic cracking
: The heavy oil with a boiling point of 200℃ or higher obtained in the process is treated with a high gradient magnetic separator to capture and remove fine particles, and then
The present invention relates to a method for producing raw material pitch for carbon fibers, which is characterized by heat treatment at ~480°C and a pressure of 2~50 kg/cj-G.

By using the method of the present invention, not only can the fine particles in heavy oil be reduced to 5 ppsa or less, but also
It becomes possible to reduce the particle size of the remaining m particles to 0.5 μm or less.

The present invention will be explained in detail below.

The heavy oil obtained by 7A dynamic catalytic cracking of petroleum used in the present invention refers to petroleum such as kerosene, light oil, atmospheric residual oil, vacuum distillation distillate, or hydrotreated oil of these oils. Usually at 450-550℃ and normal pressure in the presence of a catalyst such as natural or synthetic silica-alumina or zeolite.
By fluid catalytic cracking at 20 kg/Cm'-G, the substantially boiling point range of by-products produced when producing light oil such as gasoline is 200 to 550°C, preferably 30°C.
It is a heavy oil within the range of 0 to 550°C.

Such heavy oils usually contain iron and iron/Nl.

(2) Contains about 10 to 550 pp@ of fine particles containing the compound, and the particle size ranges over a wide range of 01 to 100 microns.

The present invention treats the heavy oil with a high gradient magnetic separator to capture and remove fine particles present in the heavy oil, and in particular fine particles containing iron and iron/N1/■ compounds. can be effectively removed.

The magnetic separator used in the present invention is a method in which a ferromagnetic packing is placed in a uniform high magnetic field space, and a magnetic field is applied to generate a high magnetic field gradient of usually 100×IO' Gauss/cm or more around the packing. This magnetic separator is designed to magnetize ferromagnetic or paramagnetic fine particles on the surface of a packing material and separate them from weak paramagnetic fine particles or diamagnetic fine particles.

As the above-mentioned ferromagnetic filler, an aggregate of ferromagnetic fine wires such as steel wool or steel net having a diameter of 1 to 1000 .mu.m, preferably 10 to 500 .mu.m, expanded metal, steel peas, etc. is used. Preferably steel wool is used.

An example of a high gradient magnetic separator is the rsA manufactured and sold by Saramagnetic Inc. in the United States.
LA-HGMS■ (product name).

A method for removing fine particles from heavy oil using a high gradient magnetic separator involves introducing heavy oil into the magnetic field space of the high gradient magnetic separator, and attaching the fine particles to a ferromagnetic packing placed in the magnetic field space. It is to remove magnetism.

Variables when operating a high gradient magnetic separator include magnetic field strength, linear velocity, processing temperature, type of particles to be magnetized,
Choose the optimal conditions depending on the size etc.

The magnetic field strength is the strength of the magnetic field in the space in which the filling is placed, and is usually 500 Gauss or more, for example, or 500 to 20 Gauss.
．． 000 Gauss, preferably 1.000-20.000
It is Gauss.

The treatment temperature refers to the temperature of the oil when it is introduced into the high gradient magnetic separator, and is usually from room temperature to 400°C, preferably from 50 to 200°C.
The temperature is 50°C.

In addition, the linear velocity is the linear velocity of oil when passing through a magnetic field space, and is usually 001 to 100 cm/sec, preferably 01 to 2 cm/sec.
It is 0 cm/sec.

The heavy oil treated with the high gradient magnetic valve machine is then heated to a temperature of 3
80-480°C, preferably 400-450°C, pressure 2
~50kg/ej, preferably 5-30 kg/c
After heat treatment (first heat treatment) at step t, light components are distilled off to obtain raw material pitch for carbon fibers. The heat treatment time is usually 5 minutes to 30 hours, preferably 05 to 10 hours.

The method of distilling off light components is not particularly limited, but a thin film distillation method is preferably employed, and is usually carried out at a temperature of 250 to 500 ml.
C., preferably 300-400.degree. C., under reduced pressure. The pressure is preferably 50 ms I (or less. Also, the thin film is preferably 100 ms or less, preferably 5++ s or less.

The carbon ta fiber miscellaneous pitch of the present invention is obtained by substantially removing the fraction having a boiling point of 400° C. or lower by R4 membrane distillation.

In order to produce charcoal "3 miscellaneous" using the charcoal of the present invention, J: the raw material pitch for fibers, first the raw material pitch for carbon fibers is heated to 3.
Heat treatment (secondary heat treatment) is performed at 40 to 450°C, preferably 370 to 420°C, under normal pressure or reduced pressure to obtain optically anisotropic pitch as pitch for spinning.

The heat treatment time is usually 1 to 50 hours, preferably 3 to 20 hours.

The secondary heat treatment can also be carried out while passing an inert gas such as nitrogen. In this case, it is preferable that the amount of inert gas aerated is in the range of 0.7 to 5.0 scfh/lb pitch.

The proportion of optically anisotropic phase in the spinning pitch is 70 to 100
% is preferred, particularly 90 to 100%.

The spinning pitch thus obtained can be melt-spun by a known method, and then the pitch fibers and pheasant obtained can be subjected to infusibility treatment and firing treatment to produce carbon fibers.

Real” example r below 1 fall! The present invention will be specifically explained by referring to the following examples, but the present invention is not limited thereto.

Example 1 Hydrotreated vacuum gas oil of Arabian crude oil was subjected to fluid catalytic cracking at 485° C. using a silica/alumina catalyst to obtain heavy 1Th(A). Its properties are shown in Table 1.

Next, 1fi quality oil (A) is separated using high gradient magnetic separator rsALA-
HGMS" (trade name) under the following conditions to obtain treated oil (B).

Magnetic field strength: 129 kilogauss Linear velocity: 0.47cm/sec'IQ degree = 150℃ Filling: Steel wool Also, same as above 1 except that the magnetic field strength was 20 kilogauss.
The treatment was carried out under the conditions of 1 to obtain treated itl+ (C).

The filtrate ash contents in the heavy oil (A), treated oil (B), and treated oil (C) were as shown in Table 2.

Example 2 3 and Comparative Example 1 The treated oil (C) treated in Example 1 was heated at a temperature of 410°C and a pressure of 9.
Heat treatment was performed for 3 hours at kg/crd. Next, the heat-treated product was subjected to thin film distillation at a temperature of 355°C and a pressure of 15n+a+[1g, with a film thickness of 3 mm, to substantially distill off the fraction with a boiling point of 490°C or lower, and to mash the carbon * miscellaneous raw material pitch. T-ko.

Next, 30 g of the raw material pitch was stirred once while passing nitrogen through at 600 m/min, and heat-treated at a temperature of 400° C. under normal pressure for 7 hours to form the pitch for spinning.

The obtained spinning pitch was melt-la-spun at a temperature of 345°C to obtain pitch fibers with a diameter of 12μ, and the pinched fibers were subjected to infusible, carbonized, and graphitized treatments under the following conditions to obtain -C carbon fibers. Good deal. The above results are shown in Table 3.

The processing conditions for infusibility, carbonization and graphitization are as follows.

0 Infusibility conditions: 50°C to 300°C in oxygen atmosphere
Also, heated at a heating rate of 2°C/min to reach 300°C & immediately cooled 0 Carbonization conditions: Raised at a rate of 25°C/min in a nitrogen atmosphere 7
Hold at 00°C for 1 minute Graphitization conditions: Heat treatment in a nitrogen stream at a heating rate of 50°C/min to 2500°C Comparative example 1 In Example 2, heavy oil (A) was used instead of treated oil (C).
Carbon hawk fibers were produced in the same manner as in Example 2, except that . The results are also listed in Table 3.

Comparative Example 2 The heavy oil (A) obtained in Example 1 was heated at 150°C.
Centrifugation treatment was performed at 4.500 rpa+ to obtain treated oil (D). The ash content of the treated oil (D) is 15 ppm
Met.

Next, carbon magnetic wires were produced in the same manner as in Example 2, except that treated oil (D) was used instead of treated oil (C). The results are also listed in Table 3.

As described above, fine particles (ash) in heavy oil can be removed with extremely high efficiency by the method of the present invention, and by using the spinning pitch obtained by heat treating the raw material pitch for carbon fiber of the present invention. When melt spinning is performed, not only is stable spinning possible without yarn breakage, but also the final product, carbon fiber, has high strength and high elasticity.

Claims (1)

[Claims] Heavy oil with a boiling point of 200°C or higher obtained when petroleum is subjected to fluid catalytic cracking is treated with a high gradient magnetic separator to capture and remove fine particles, and then separated at a temperature of 380 to 480°C and a pressure of 2 to 50 kg.
A method for producing raw material pitch for carbon fibers, characterized by heat treatment at /cm^2・G.