JPS62131090A - Production of precursor pitch - Google Patents

Abstract

PURPOSE:To obtain the titled pitch having excellent spinnability and infusibility and capable of providing a carbon fiber having excellent mechanical properties, by hydrogenating a particular fraction of a heavy distillate derived from petroleum, mixing the hydrogenation product with a recovered high-boiling oil, heat-treating the mixture under pressure and removing insoluble matter, followed by heat treatment. CONSTITUTION:A petroleum heavy distillate obtd. by steam cracking and catalytic cracking of petroleum or the like is distilled to obtain a fraction having a b.p. of 250 deg.C or above. The fraction is hydrogenated under a hydrogen pressure of 50-300kg/cm<2> at 300-550 deg.C for 10-120min in the presence of a hydrogenation catalyst. To the hydrogenated fraction is added a recovered heavy distillate. The mixture is heat-treated under pressure at 350-550 deg.C, followed by removal of insoluble solids by means of filtration or the like. The filtrate is distilled to remove the solvent and a light oil having a b.p. of 250 deg.C or below which has been produced as a by-product, thereby obtaining a fraction having a b.p.of 250 deg.C or above. The fraction is heat-treated under a reduced pressure of 5-100mmHg and/or in a stream of an inert gas at 350-550 deg.C to obtain the titled pitch having a b.p. of 220-320 deg.C and contg. 40% or less quinoline-insoluble matter and 70% or more toluene-insoluble matter. The heavy distillate which has been recovered by stripping is also circulated for reuse.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a precursor pitch suitable as a raw material for carbon processed products. More specifically, the present invention relates to a method for producing precursor pitch for carbon products such as carbon fibers using petroleum-based heavy oil as a raw material.

(Prior Art) As is well known, various carbon processed products such as filaments, films, ribbons, etc. are produced using various carbon buying materials as raw materials.
There is interest in producing pitches that can be applied to sheets and the like. In particular, carbon fs fibers are one of the products that are being industrialized today, and although pitch applicable thereto will be described in this specification, it is also applicable to other carbon processed products.

It is widely known that various studies are currently underway with the aim of producing high-performance carbon fibers at low cost using pitches as raw materials.

In the production of carbon EM orange using pitches as raw materials, precursor pitch prepared by various physical and chemical methods is melt-spun, the resulting pitch Hi fibers are made infusible, and then carbonized. , the mechanical properties of the obtained carbon iso fibers are highly dependent on the chemical and rheological properties of the precursor pitch.

In other words, the chemical properties of the precursor pitch for high-performance carbon fibers are that its constituent molecules are rich in aromaticity, have a high degree of selective orientation, and at the same time are essentially condensed polynomial aromatics that are easily graphitized. It is necessary to be a group compound.

On the other hand, the rheological properties of the precursor pitch include that the temperature at which the bath melt viscosity suitable for melt spinning is exhibited is as low as possible, and thermal history such as thermal decomposition and polymerization of the pitch during melt spinning can be prevented.

As a precursor pitch suitable for manufacturing such carbon fibers, for example, JP-A-54-16042 discloses a method for obtaining neomesophase pitch as a precursor pitch by solvent extraction of petroleum pitch, JP-A-57-16042. No. 119984 describes a method in which tar obtained from catalytic cracking of petroleum is subjected to thermal decomposition and condensation, and then allowed to stand still to extract the separated lower layer of men-phase pitch. In JP-A No. 58-18421, coal tar pitch, etc., is heated to obtain a precursor pitch by adding 2 to 5 atoms of nuclear-hydrogenated aromatic carbide and heat-treating the tar obtained by heating. Various methods have been proposed, including a method of obtaining a precursor pitch called pre-mesophase by modifying it by chemical conversion and then heat-treating it under reduced pressure.

(Problems to be Solved by the Invention) Although the mechanical properties of pitch-based carbon fibers have been improved by these methods, the yield of the obtained precursor pitch is lower than that of feedstock oil from which light valves have been removed. It is unfortunately low at 10 to 20, which is not industrially sufficient. In particular, when petroleum-based heavy oil, for example, heavy oil obtained during steam cracking such as naphtha, is used as a raw material, the yield of precursor pitch is at most 10 pitch compared to the raw material from which light valves have been removed. is extremely low.

The reason for this is that petroleum heavy oil generally has a high molecular weight of 7/C.
This is because it is rich in fused ring aromatic compounds having a 7-flutene structure or a relatively long alkyl side chain, and the number of fused rings is relatively small, 2 to 5.

In other words, compounds having high molecular weight asqualtene or long alkyl side chains in the raw material oil, which are undesirable for the production of precursor pitch for high-performance carbon fibers, are removed by solvent extraction, etc., or by hydrogenolysis, etc. Further, during the polycondensation process such as heat treatment under reduced pressure, low molecular weight condensed ring compounds are removed as low boiling point components, which is a factor that reduces the yield. .

An object of the present invention is to take these factors into consideration and to produce a precursor pitch for high-performance layer fA fibers at a high yield using petroleum-based heavy oil as a raw material. Furthermore, other objects of the invention will become apparent from the description below.

(Means for Solving the Problems) As a result of intensive research to achieve this objective, the present inventors discovered that when preparing carbon fiber precursor pitch from petroleum-based heavy oil, first, hydrogen Decomposition and modification of asqualtene or alkyl side chains in the raw materials are carried out through chemical treatment.
Next, the heavy oil recovered in the next step is added and heat treated under pressure to increase the molecular weight through a partial polycondensation reaction, followed by further heat treatment under reduced pressure and/or in an inert gas stream. It was discovered that a high-yield, high-performance precursor pitch could be obtained by this method, and the present invention was completed.

That is, the present invention comprises: (a) a step of hydrotreating a fraction with a boiling point of 250C or higher from petroleum heavy oil; (b) mixing the hydrotreated fraction with the heavy oil from step (d). (C) Step of removing solid impurities and light oil with a boiling point of 250C or less from the heat-treated fraction (d) Heat-treating the fraction from which the insoluble matter and light oil have been removed under reduced pressure and/or Or heat-treated under a stream of inert gas, with toluene insolubles of 70% by weight or more and quinoline insolubles of 40% by weight.
A method for producing a precursor pitch, characterized in that it is a precursor pitch containing the following, and consists of a combination of the steps at least the step of recycling part or all of the heavy oil recovered at this time to step (b). .

The method of the present invention will be explained in detail below.

In the method of the present invention, the petroleum-based heavy oil used as a raw material is heavy oil obtained during steam cracking, catalytic cracking, etc. of petroleum, or heavy oil obtained by thermal cracking, distillation, etc. of crude oil. Oil etc.

Furthermore, if its physical properties are specified, the aromatic hydrogen measured using proton NMR of the fraction with a boiling point of 250C or higher is 50 to 60%, and the aromatic carbon content is 40 to 80% as measured by carbon ("C) NMR. Further, it is preferable that the hydrogen atom/carbon atomic ratio (hereinafter referred to as H/C) is 0.7 or more.

Particularly for carrying out the present invention, ethylene bottoms obtained from steam cracking of petroleum products or decant oil obtained from fluid catalytic cracking are preferred.

From these selected petroleum heavy oils, a fraction with a boiling point of 250C or more, preferably I/is o OC or more is obtained by isobaric distillation, and this is treated with a suitable hydrogenation catalyst, such as cobalt-
If necessary, in the presence of a commercially available hydrodesulfurization catalyst containing molybdenum, nickel-molybdenum, etc. supported on alumina,
Aromatic oil such as quinoline, naphthalene oil, anthracene oil, hydrogenated oil thereof, or by-product aromatic light oil is used as a solvent, and hydrogen pressure is 50 to 500 k.
g/(support) - Preferably 80 to 200 kg is treated for 10 to 120 minutes at a temperature of 600 to 550 C, preferably 400 to 500 C, but a batch method using an autoclave or the like, or Any method such as a flow method using a tubular reactor or the like may be used.

Then, after substantially removing the hydrogen gas, the heavy oil obtained in the next step, i.e., heat treatment under reduced pressure and/or in an inert gas stream, is added and heated to a temperature of 350A-550C.
Preferably, the pressure heat treatment is performed under the conditions of 400A-500C, and the pressure at this time is autogenous pressure or #i20-2
00 kg/C1N". The reaction may be carried out in either a batch manner using an autoclave or the like, or a flow method using a tubular reactor or the like.

After the heat treatment reaction, insoluble matter generated by coking etc.
The used catalyst and the like are removed by a method such as K filtration or centrifugation.

After removing insoluble matter, the used solvent and the by-produced @ quality oil are recovered by a method such as distillation to obtain a fraction with a boiling point of 250C or higher, preferably 300C or higher. The recovered solvent or by-produced aromatic light oil can be reused as a solvent for the previous hydrotreatment.

The properties of the middle distillate obtained above are determined by proton NMR.
Aromatic hydrogen by 40 to 70%, carbon ('3C)NM
The number of aromatic carbons due to R is 60 to 90, and H/
C is 0.6 to 1.0, and toluene static content is 10
~50% is required.

The middle distillate prepared in such a state is further heated under reduced pressure and/or in an inert gas stream, preferably j/15-5-
Heat treatment is performed at a temperature of 350-%-500C while blowing an inert gas such as 9 elements under a reduced pressure of 100 JIIHg. The method may be a batch method using a reaction tank or the like, a semi-batch method, or a flow method using a thin film evaporation reactor or the like.

The properties of the precursor pitch obtained in this way have a melting point of 2
The temperature at which the melt viscosity is 20 to 390 c% is 520 to 390 c, the quinoline insoluble content is 40% or less, and the toluene insoluble content is 704 or more. Moreover, when this pitch is pulverized and oxidized at 300C in an oxygen stream, the pitch is prepared so that it has an oxidation property with a weight increase rate of 5 to 20.

A part or all of the heavy oil stripped in this heat treatment, preferably a fraction with a boiling point of 350c or higher, is recycled to the pressurized heat treatment process described above to produce a precursor suitable for producing carbon fibers. Pitch can be obtained in high yield.

(Operations and Effects of the Invention) By implementing the method of the present invention, the yield of precursor pitch from petroleum heavy oil such as ethylene bottom or decant oil can be significantly improved to /fi30A-50%. Further, the precursor pitch obtained by this method is characterized by excellent spinnability and infusibility, and the mechanical properties of its carbon fibers are also high.

The reason why the method of the present invention increases the yield of precursor pitch is that the low molecular weight aromatic metal ring compound modified by hydrogenation is subjected to pressure heat treatment and partially condensed and polymerized.
In the next heat treatment step under reduced pressure and/or in an inert gas flow, the IJ piping is suppressed and the condensation polymerization proceeds further.
This is thought to be due to the fact that heavy oil, which is converted into precursor pitch and recovered during heat treatment under reduced pressure, is repolymerized by pressure heat treatment.

Moreover, the precursor pitch obtained by this method is carbon 1
It is not clear whether it has excellent performance as a tissue, but the two-step heat treatment after hydrogenation produces condensed aromatization with good orientation, while at the same time creating a molecular structure that retains appropriate reactivity. It is estimated that In other words, pitch with high aromaticity has excellent spinnability and has appropriate functional groups such as alkyl or naphthenic structures.
This is thought to be due to the fact that infusibility becomes easy and the structure of the carbon fibers exhibits random orientation.

(Example) Examples of the present invention will be shown below, but the present invention is not limited thereto.

Reference Example 3 kg of decant oil with a boiling point of 300 to 550 C obtained when gas oil is catalytically cracked at 450 to 550 C, and 1 kg of commercially available cobalt-molybdenum-alumina supported catalyst 501F.
The autoclave was charged into a 0-ton autoclave, the atmosphere was replaced with nitrogen, and then the pressure was increased to 100 kgl (2G) with hydrogen gas. Then, without stirring, the mixture was heated to 465C and hydrogenated for 20 minutes. After cooling, the pressure was reduced to substantially remove hydrogen gas, and then the mixture was heated again to 465C and heat-treated under pressure for 60 minutes. At this time, the reaction pressure Ifi120 is ν'OII”G
reached. After cooling, the pressure is reduced, the liquid is extracted, and this is
After filtering at 0 to 90C to separate and remove the catalyst and insoluble matter generated by coking, the resulting tar was distilled under reduced pressure to obtain 1.8klIk of intermediate pitch with a boiling point of 250C or higher.

The pitch thus obtained was charged into a flask equipped with a pressure reducing device and 9 blowing nozzles.20-30111)
It was heated to 460C under a vacuum of 1 g while blowing nitrogen at 1200 mtitm, held for 25 minutes, and then cooled.

The pitch thus obtained, ie, the precursor pitch, was 5402, and the yield was 18 pitch. In addition, by stripping, heavy oil with a boiling point of 300C or higher is removed from 1250℃. Recovered.

The obtained precursor pitch had a quinoline insoluble content of 15.
The toluene-insoluble content is 91%, and by making it into g-fused thread and carbonizing it at 1.1500C, the tensile strength is 3.
05 kg/rats" and an elastic modulus of 23 T/-12.

Similar to the reference example, decant oil L with a boiling point of 500 to 550C
To 7! J and a commercially available cobalt-molybdenum-alumina supported catalyst 301 were placed in a 10 t autoclave, and after exchanging nitrogen, the mixture was heated to 100 kf/DtL"G with hydrogen gas.
Pressure was applied. Then, without stirring, the mixture was heated to 465C and hydrogenated for 20 minutes.

After cooling, reducing the pressure and substantially removing hydrogen gas, the boiling point 50 obtained by vacuum stripping in the reference example
5c was added to the heavy oil L2 at 0C or higher, heated again to 465C, and subjected to pressure heat treatment for 60 minutes. At this time, the reaction pressure reached ij 120 kglon" G. After cooling, the pressure was reduced and the liquid was extracted. This was filtered at 80 to 90 C, and the insoluble matter produced by the catalyst and coking was removed at the valve part. The tar is distilled under reduced pressure to a boiling point of 25
An intermediate pitch of 1780r of 00 or more was obtained.

The pitch obtained in this way was charged into a flask equipped with a pressure reducing device and 9 blowing nozzles, and the pitch
Under reduced pressure of ′? While blowing 4 elements at 1200 d/frame, it was heated to 460C, held for 20 minutes, and then cooled.

The pitch thus obtained, that is, the precursor pitch, was 5102, and the yield was 30% based on the raw material oil.
It was Chi. Also, the heavy oil recovered by stripping is 1270? It was approximately the same amount as the heavy oil added during the pressure heat treatment.

The obtained precursor pitch had a quinoline insoluble content of 16,
The toluene content is 92%, and by melt-spinning it, making it infusible, and carbonizing it at 1500C, the tensile strength is 29%.
A carbon fiber with an elastic modulus of 0 kl1MI8 and 4T/dI, which was almost the same as the reference example, was obtained.

Claims (1)

[Scope of Claims] (a) A step of hydrotreating a fraction with a boiling point of 250°C or higher from petroleum heavy oil (b) Adding the hydrotreated fraction to the heavy oil from step (d) (c) removing solid insoluble matter and light oil with a boiling point of 250°C or less from the heat-treated fraction; (d) heating the fraction from which the insoluble matter and light oil have been removed under reduced pressure and / or heat-treated under an inert gas flow, toluene insoluble content of 70% by weight or more and quinoline insoluble content of 40% by weight
A method for producing a precursor pitch, characterized in that it is a precursor pitch containing the following, and consists of a combination of the steps at least the step of circulating part or all of the heavy oil recovered at this time to step (b).