JPS5867786A - Mesophase pitch raw material from hydrogen- treated decant oil - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to mesoface pitch, a raw material for mesoface pitch.

Meso 7 Ace pitch is used in the production of carbon fiber with 1% better mechanical properties for the production of carbon products. Carbon fiber made from menface pitch is lightweight, strong and
It is known that it has good rigidity and conductivity, and is chemically and thermally inert. Charcoal Used in the aerospace industry and high-end sporting goods.

In this specification, "Meso7Ace" is understood as used in the art, and is generally the same as liquid crystal. Liquid crystals are in a state of matter intermediate between crystalline solids and ordinary liquids. Normally, mesophase-like materials have anisotropy and liquid properties.

In Kikiri IT, "Meso 7 Ace Pitch" is a pitch that contains more than about 100% by weight of mesofaces and is capable of forming an anisotropic continuous phase when dispersed by conventional techniques (such as stirring).

Generally, decant oil is converted to pitch by distillation. Sometimes a heat treatment step is performed before distillation. The product obtained from distillation is isotropic pitch, which must be further processed to convert it into meso-7 ace pitch.

Conventional methods for producing mesoface pitch from isotropic pitch raw materials involve applying approximately 350 N of the raw material to cause thermal polymerization.
It includes heat treatment at 450°C.

A typical conventional method is to maintain the reactor at about 400° C. for about an additional period of time. The properties of the meso-7ace pitch produced can be controlled by the reaction temperature, heat treatment time, and volatilization rate.Since there is a high molecular weight portion due to zero polymerization, the softening point of the meso-7ace pitch is The temperature will reach at least 300°C. The softening point increases as the mesophase content increases. Typically, in order to spin mesoface pitch, the temperature is about 蜀°C to about 10°C above the softening point of the mesoface pitch. It is desirable to be able to spin at relatively low temperatures, to avoid excess polymerization that could clog the narrow orifices used for spinning, and to minimize energy consumption.

The mesophase content in pitch is a paper.

Quant mouth alive Determinatio
n of Mesophase Content 1
n Pitch″B, ChWllttak, R,'r
, Lewis, J.

D, Rugiero 11, Flfteenth
BIenniml Conference on
Carbon, June 1981, pp. 148, 149).

Generally, the terms "softening point" and "melting point" are used interchangeably in the art to broadly characterize pitch with respect to molecular weight composition and to estimate the required spinning temperature.

There are several methods for measuring softening temperature, and the temperatures measured by these different methods are quite different from each other.

The MeFler softening point measurement method has been widely adopted as a standard for pitch evaluation.This method can be applied to Mezzo 7 Ace pitches.

Hot stage microscopy to examine the softening temperature of mesoface pitch
It can also be measured by In this method, mesoface pitches are heated under polarized light on the hot stage of a microscope in an inert atmosphere. While controlling the rate of increase in mesoface pitch temperature, increase the temperature,
When the membrane pitch begins to deform, the temperature at that time is recorded as the softening temperature.

Specification: In iF, "softening point" or "softening temperature"
are used interchangeably and shall refer to the temperature determined by the Mettler measurement method both in the case of the precursor and also in the case of Mens-Nice pitch.

In this Example A, the experimental formula of the decanted oil before and after hydrogen treatment was obtained from the molecular weight and elemental analysis data by a conventional method.

Decanted oil is widely used in the production of isotropic pitch-like feedstocks that can be converted into mesoface pitch. Methods for producing pitch precursors from decanted oil are well known and usually involve applying heat to the decanted oil. The process includes distilling the decant oil under reduced pressure while adding it.

Decant oil is highly aromatic and the industry teaches that high aromaticity is required in the raw materials to produce good mesoface pitch, so decant oil is used for mesoface pitch. It is desirable to produce pitch precursors of up to %. Edited by P. L. Walker, @Chemistry and Phyljtlo
f Carban', vol, 4.261, 262
Page (1960), @Carbon'', 12, 332
(1974) and US Pat. No. 4,005,183.

The decanedioyl used in the industry to make raw materials for mesoface pitch is similar in sulfur content from about 1 to about 2.5% by weight. Mesoface pitch produced from this raw material has an anisotropic region (d
omain) can be formed. It is important to have the kind of people who can form such a large field. This is because it shows that the &1° mesoface pitch is suitable for producing carbon fibers with good mechanical properties as well as good spinnability.

It is known that membrane pitch, which can form large anisotropic regions, has high deformability.

When spinning commercially, the mesophase content of the two mesophases is at least 70% by weight, preferably 1% by weight, to produce good carbon fibers. This is one goal of the present invention.

The sulfur content of the decant oil is important for commercial carbon fiber production. Problems may arise with carbon fibers that require processing temperatures above about 2500°C. This is because at such high temperatures, sulfur power is displaced, resulting in lower tensile strength and lower density of the resulting carbon fibers.

According to the prior art, high sulfur decant oils have been deemed unsuitable for the production of meso 7 ace pitch for high quality carbon fibers.

U.S. Pat. No. 4,075,084 or 4,166.
Preferably, 1 g of 16 sulfur decanted oil is subjected to hydrodesulfurization by the known method taught in No. 026.
Generally, by hydrodesulfurization, hydrocarbon oil is contacted with hydrogen in the presence of a catalyst.

However, it is well known that hydrotreating reduces the aromaticity of hydrocarbon oils, and therefore, hydrotreated decant oils give mesoface pitches with relatively poor spinnability, and such mesoface pitches It is expected in the art that carbon fibers made from carbon fibers will have poor mechanical properties.

P. H. Emmett Q Collection, ”Cata
lysis'', vol, V.

Rhelnhold Publ irhlng Cor
p., New York, 1957.

Published and edited by C. L. Thomas, “Catal
ytic pro-cesas and prove
n Catalysts”, Acadamlc P
Res (1970) points out that hydrogen treatment reduces aromaticity.

As used herein, "hydroprocessing" is any method of contacting decanted oil with hydrogen in the presence of a catalyst according to techniques in the art.

Contrary to the teachings of the art, the hydrotreated decant oil of the present invention produces a mesoface pitch that exhibits improved properties compared to mesoface pitch made from non-hydrotreated decant oil. It has been newly discovered that it can be processed to

Furthermore, the improved mesoface pitch can be processed into carbon fibers with improved properties by known methods.

These surprising results can be generally explained as follows. However, this explanation is only a guideline that can be considered when applying the present invention, and is not intended to be limiting. A thermal polymerization process for converting a pitch precursor raw material into mesoface pitch will be described.

Typically, pitch precursors have a relatively broad molecular weight distribution. Pitch contains both low and high reactivity molecules. Rapid polymerization by highly reactive molecules is not preferred. This is because very large molecules are produced in the resulting meso-7 ace pitch. These high molecular weight components make the viscosity of the mesoface pitch relatively thick (thus, the size of the corresponding mesoface region becomes small).

This phenomenon is discussed in US Pat. No. 3,976.729.

Hydrogenation of the decant oil according to the invention slows down the reaction rate of the highly reactive molecules and allows them to undergo the desired structural rearrangements before and during the polymerization reaction. As a result, the viscosity of the membrane pitch is relatively low and the size of the anisotropic region is relatively large.

The pitch precursor raw material produced according to the present invention is J,
E. Zbrmer, “Mesophase Trs.
+nsformatlon ln aSolvent-
Extracted Pitch'', Fifteen
lhBlennialConference on
Carbon, June, 1981. 146 pages, 1
It can also be converted to mesophase pitch by solvent extraction as described on page 47 and in the literature cited herein. Surprisingly, the mesoface pitches produced are characterized by excellent area size and softening point.

The mesophase yield from hydrogenated decant oil is lower compared to untreated decant oil.

However, this lower yield and increased cost associated with the hydrotreating step is compensated for by a surprising improvement in the quality of the membrane pitch.

In its broadest embodiment, the present invention provides a process for hydrotreating a decant oil and distilling the hydrotreated decant oil until the decant oil has an average number of hydrogen atoms in excess of about 2 to about 3 hydrogen atoms per molecule. The present invention relates to a method for producing a raw material for mesoface pitch.

The present invention also relates to mesoface pitch fibers and carbon fibers formed from the mesoface pitch of the present invention.

Another embodiment of the present invention relates to improvements in subjecting hydrotreated decant oil to heat-pressure treatment to create a tar residue and distilling the kernel tar residue to form pitch.

Compared to the process of the invention without heat treatment, the overall yield of raw material for decanted oil is increased by heat-pressure treatment.

Generally, % heat-pressure treatment is
It is carried out by the method described in No. Specification '@ (filed on October η, 1979 and assigned to the present applicant). This patent application is patented and the assignment thereof is hereby incorporated by reference. The outline of this application is as follows.

The severity of heating under pressure is widely known in the petroleum industry (technical term used is soaking volume factor).
It can be evaluated by the following: king volume factor). The soaking I volume factor of 1.0 is approximately 52.7 KPCI & (approximately 750 ps1
g) at a pressure of about 427° C. and a temperature of about 427° C. for 4.28 hours. The effect of temperature on the rate of polymerization or decomposition of hydrocarbons is known in the art. For example, the decomposition rate at 450°C is 3.6 of the decomposition rate at 427°C.
It is 8 times more. Most of the examples shown herein are about 4
Since the temperature was 50° C., the strictness of the heat treatment was calculated based on the seven temperature equivalence criteria.

Preferred temperatures for patch heat-pressure treatment.

The pressure and soaking-lume factor ranges depend on the precursor. For decant oil, the temperature range is about 400 to about 475 °C and the pressure range is about 14 to
Approximately 1059α・G (approximately 200 to approximately 1500pm 1g)
and the soaking gel factor is 11E0.4 to about 8.6. The Norking I ream factor corresponds to about 0.5 to about 10 hours at about 450°C. Conradson carbon content is low (approximately 20%,
Preferably, the patch heat-pressure treatment is stopped when the concentration is greater than about 30% and less than about 65%. If the mesophase content is less than about 601% by weight and infusible solids are present, hot filtration is preferred. When filtering, the temperature can be raised to such a point that the product liquefies, so that the infusible solids can be separated by filtration. During the heat-pressure treatment, cuff agitation is preferably used to maintain homogeneous distribution.

The present invention is more economical to use continuous heat-pressure treatment instead of patch treatment. For continuous heat-pressure treatment, the temperature range is about 420 to about 550°C and the pressure range is about 14
~ Approx. 10511ffi””-G (Approx. 2oo ~ Approx. 1500
pm1g) and the Sorkinderium Factor is about 0.4 to about 2.6. The soaking-lume factor corresponds to about 0.5 S for about 3 hours at about 450''C.

The Conradson carbon content of the material to be treated is at least about 5%
, preferably greater than about lθ% (less than about 65%), the continuous heat-pressure treatment is stopped. The mesophase content is less than about % by weight. If infusible solids are present, high temperature Filtration is preferred.

Accordingly, the present invention encompasses the scope of the invention as indicated in the several steps and the relationship between those steps (all of which are detailed in the description below) and the scope of the specific Ft'i* requirements. do.

For a further understanding of the nature and objects of the invention, reference should be made to the detailed description of T1 in conjunction with the accompanying drawings.

Many other examples may easily be derived in light of the guiding principles and teachings contained in the following six illustrative, non-limiting examples of the invention.

The examples described herein are merely illustrative of the invention and are not intended to limit the manner in which the invention may be practiced. Unless otherwise specified herein, parts and percentages are N'N parts and weight. %.

In FIG. 1, the decant oil is hydrogen treated as follows.

Reactor 1 is a stainless steel tube with an inner diameter of 32111,
It is heated in a resistance furnace (not shown). Reactor 1 is.

The decant oil is introduced from the top from the decant oil supply source 2 to create a trickle bed type system.
de ) is operated.

The hydrotreating catalyst in the reactor is of the type commonly used for the hydrodesulfurization of petroleum feedstocks. A 100 MJ catalyst pellet is mixed with 200xj quartz chips (12/16 mesh) and charged into a stainless steel tube. The length of the catalyst bed obtained is 370 square meters.

Fresh catalyst bed is supplied from paths 3 and 4 and valve 6
and activated with hydrogen and hydrogen sulfide controlled by 7.

The nitrogen supplied via line 9 and controlled by valve 8 is
Used to remove dissolved hydrogen sulfide from the catalyst.

Gas from reactor 1 is removed via line 11 to separator 12 and recovered hydrogen is removed via valve 14 via line 13. The hydrotreated decant oil is sent from reactor 1 via line 16 to storage 17 .

The continuous heat-pressure treatment shown in FIG. 2 is as follows.

The hydrotreated decant oil is placed in the supply tank 18. If desired, a heater can be provided in the supply tank 18 to heat the decant oil to reduce its viscosity and improve its flowability. Supply tank 18 is route 19
is connected to a pump 21, and this meso sends decant oil through path n, which is monitored by a pressure gauge B.

Decanted oil passes through a furnace coil in a fluidized sand bath.

If a long treatment is desired, several fluidized sand baths can be used in tandem.

The treated decant oil passes through line A to valve N, which is controlled by pressure regulator 4, and is collected via line 31 into a product collection tank vane for use in subsequent steps of the invention. .

Example 1 The decant oil was subjected to hydrogen treatment until the average number of water atoms per molecule of the decant oil was approximately 3 stripes. The hydrotreated decant oil was distilled and converted into pitch at a final temperature of about 260°C.

In order to evaluate the properties of the pitch precursor as a raw material for mesoface pitch, a portion of the pitch precursor was heated to approximately 400°C.
It was heat-treated for about 2 hours to convert it into mesoface pitch.

The height of the mesoface pitch region generated by heat treatment was measured to be approximately 500 microns. Mesoface pitch produced in the same way from untreated decanted oil was
Typically.

The larger area size of the mesoface pitch produced according to the present invention, which had an area size of about 250 microns, indicates that the quality of the mesoface pitch is better. Therefore, it can be expected that it will be well suited for commercial spinning.

Furthermore, the relatively large area size also indicates that: The membrane pitch produced according to the present invention exhibits high deformability, and it can be expected that the molecules will align relatively easily when spun into fibers. This results in favorable low orientation parameters and excellent mechanical properties for carbon fibers.

The yield of pitch precursor obtained amounted to 21x% by weight with respect to the decant oil. Pitch during reaction 0.454Kf
Approximately 0.141 per pound! Semi-37h (about 5
The pitch precursor was converted to mesoface pitch by sparging with altan at a rate of 0.2 scfh) and a conventional heat treatment at about 390° C. for about 9 hours with agitation.

The resulting mesophase pitch contained approximately 100% by weight mesophase WL, a 14% yield with respect to the pitch precursor. The Mettler softening point of mesoface pitch was about 289°C. This softening point is

Surprisingly low for a thermally generated mesophase with 100% mesophase content.Furthermore, this mesophase pitch can be spun at a temperature of about (9) to about 40 degrees Celsius lower than regular 100% mesophase pitch. I can do it.

The overall yield of mesoface pitch on decant oil was about 3 fold it%.

Example 2 The hydrotreated decant oil of Example 1 was weighed in a press-type autoclave to weigh approximately 4 to 35 kg CIL・G (approximately 40
0 to about 500 pslg) under nitrogen at a pressure of about 430 pslg)
It was subjected to patch heat-pressure treatment at a temperature of 0.degree. C. for about 4 hours. A tar residue amounting to approximately % by weight was obtained. This residue was then distilled to yield a pitch precursor that reached approximately 37% Ni yield on the hydrotreated decant oil.

The pitch precursor was then heat treated at about 390° C. for about I hours to convert it to mesophase pitch. The resulting men's nice pitch contained about 100% mesoface and had a Mettler softening point of about 317°C.

The mesoface pitch yield was about 1% by weight with respect to tar residue, and the overall yield of mesoface pitch was about 11.3% by weight with respect to the hydrotreated decant oil.

This overall yield is significantly greater than the overall yield obtained in Example 1 and demonstrates the value of hydrotreated decanted oil when subjected to heat-pressure treatment.

The resulting membrane pitch was spun into monofilaments, thermosetted, and then carbonized at about 1700° C. by conventional methods. The diameter of the filament was approximately 8 microns. Typically, the mechanical properties of the filaments were excellent. The average Young's modulus is approximately 1.97810'tcs+-2(
Approximately 28X10' psi) tear'), average tensile strength is approximately 39400s1-1 (approximately 560,0OOpsi)
From the ratio of these values, it can be seen that the strain vs. failure value is approximately 2%, which is approximately twice that of the conventional mesoface pitch carbon fiber.・High strain vs. failure value teeth,
It is believed that the commercial product Klj has many advantages.

Example 3 A second decant oil was hydrotreated until the average number of hydrogen atoms per molecule of the decant oil was about 2 more.

To evaluate the hydrotreated decant oil, a portion of ca.
Mesoface pitch was produced by heat treatment at 00° C. for U hours. The area size of the meso7 ace pitch was approximately 300 microns.

In contrast, untreated decant oil produced mesoface pitch with an area size of about 200 microns in the same test.

Hydrogenated decant oil is heated to approximately 23 Kl fi-”G (approximately 330 psig) in a pressure autoclave.
The sample was subjected to patch heat-pressure treatment at a pressure of about 440°C and a temperature of about 440°C for about 4 hours. The resulting tar residue reached a yield of about 79% by weight with respect to the decant oil. 2 tar residues
Vacuum distillation was carried out at mI pressure to a pot temperature of about 262°C. The raw material obtained reaches a part weight % yield with respect to tar residue,
This residue was then processed using a reactor to produce a pitch of 0.454.
Approximately 0.14 standard m per Kl (1 portd)
The dispersion yield of alnon was reached at a rate of about 5 scfh (about 5 scfh) and the softening point was about 332°C. The mesophase content was approximately 100% by weight.

The mesoface pitch was spun into monofilaments, and the monofilaments were heat cured by heating at about 375° C. in air. Approximately 170
Carbonized at 0°C. The carbon thread diameter was about 18 sacrons.

The average Young's modulus of carbon fiber is approximately 1.55X10'KPff
i-2 (approximately 22 x 10'psi), and the average tensile strength is approximately 14.1 x 103 psl (approximately 200 psl
), and as a comparison, the average Young's modulus of carbon fibers obtained from meso7 ace pitch from untreated decant oil was about 1.55. The decant oil was hydrotreated. A portion of the hydrotreated decant oil was meso-7 as in the previous example.
Converted to Ace Pitch.

The size of the area of mesoface pitch was approximately 260 microns.

In contrast, men's nice pitch made from unhydrogenated decant oil had a field size of about 119 microns.

Example 5 The decant oil of Example 1 was hydrogen-treated until the average number of hydrogen atoms per molecule of the decant oil was about 3. The tar residue was subjected to continuous heat-pressure treatment for about 9 minutes at a temperature of about 9 minutes.A tar residue was obtained with a yield of about n% by weight with respect to the decant oil.The tar residue was distilled to produce pitch raw material with a softening point of 104 °C. I got it.

The yield was approximately n% by weight with respect to tar residue. This raw material was thus heat treated at about 400° C. for about 18.5 hours. The yield of two pieces of Meso 7 Ace obtained was about 52 weight units based on the raw materials, and the softening point was about 318°C.

The mesophase content was approximately 95% by weight.

The mesoface pitch is spun into multifilaments, which are heat cured by heating to about 375°C in air, and then processed by conventional techniques in an inert atmosphere to about 8°C.
It was carbonized at 500°C. The average properties of carbon fiber are Young Hontsuri 7.0X10@騨3-2 (approximately 100 XIO” pg
i) *1 tensile strength [approximately 27.4 x 10”KP
Atta with ll (approximately 390 x 10” psl).

As a comparison, mesoface pitch was produced by processing decant oil that was not hydrogen treated. The decant oil was converted into a tar residue by patch heat-pressure treatment at a pressure of about 70.3 r#g (about 1000 pmlg) and a temperature of about 470° C. for about 8 minutes. The yield of tar residue obtained was 98.5% by weight with respect to the decanted oil.

This residue was distilled to form a pitch precursor with a softening point of 116°C. The yield was approximately t% with respect to tar residue.

This pitch was heated at about 400° C. for about 16.5 hours to convert it into Men 7 Ace pitch. The yield of this mesoface pitch was about 100% by weight with respect to the pitch precursor, and the softening point was about 318°C. The mesoface content was approximately 90 gk%.

This mesoface pitch was processed into carbon filaments in the same manner as men7ace pitch from hydrogen treated decant oil. Obtained carbon edge taf) average 'r
y/14 to approximately 4.4 xto' Kpcyn-2 (approximately 63X10'psl) and the tensile strength to 19.7X10
3KPcm-” (approximately 280 x 10” psj)
Carbon fibers produced with feedstock obtained from atta-hydrogenated decant oil had superior mechanical properties compared to carbon fibers obtained from untreated decant oil.

Example 6 The pitch raw material obtained from the hydrotreated decant oil of Example 5 was
Solvent extraction to obtain mesoface pitch
The solid raw material was stirred with toluene at room temperature for 1 hour (stirring). The raw to toluene ratio was Iflol. The insoluble portion obtained in 8.3 wt% yield contains about 6 wt% mesophase. It was a mesoface pitch.This mesoface pitch had a Mettler softening point of 272°C.
The size of the anisotropic region was approximately 50°.

Summary of Examples Showing a summary of the data for Examples 1-6, water bulk treated decant oils are desulfurized as shown in the data.

Aromatic hydrogen content was determined by conventional nuclear magnetic resonance (NMR).

G1 vA c4 et5-A tci The invention is not to be limited to the precise description shown and described. This is because obvious modifications will occur to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing hydrogen treatment of decant oil,
FIG. 2 is a diagram showing continuous heat-pressure treatment. 1... Reactor, 2... Decant oil supply source, 3.
...Route, 4...Route, 6...Valve, 7...Valve, 8
···valve. 9...route, 11...route, 12...separator, 1
3...Route. 14... Valve, 16 = Route, 17... Reservoir, 1
8... Supply tank. 19...route, 21...2ndzo, 22...route,
23...Pressure gauge. U...fluidized sand bath, g...route, n...valve, 29.
- pressure control valve, 31...path, 32...product collection tank;

Claims (1)

[Claims] 1. The method is characterized by including the following steps. A method for producing raw materials for mesoface pitch (provided that the mesoface content is at least 70% by weight). (a) A step of hydrogen-treating the decant oil until the average number of hydrogen atoms per molecule of the decant oil increases by about 2 to about 3. 10) Distilling the hydrotreated decant oil to form pitch. 2. It is characterized by the following steps: A method for producing a raw material for mesoface pitch (provided that the mesoface content is at least 70 weight fl:%). (a) A step of hydrogen-treating the decant oil in a trench in which the average number of hydrogen atoms per molecule of the decant oil increases by about 2 to about 3. (b) A process of subjecting the hydrogen-treated decant oil to heat-pressure treatment to remove tar residue. (c) A process of distilling this tar residue to form pitch. 3. Preheat-pressure treatment #α・G (about 200 to about 15 ■
3. The method of claim 2, wherein the process is a patch heat-pressure treatment under a pressure of 100 psig. 4.@Heat-pressure treatment at a temperature of about 420 to about 550°C and about 14 to about 105
It is a continuous heat-pressure treatment under a pressure of 0 pmjg). The method according to claim 2. 5. A method for producing 161 tons of mesoface per day (provided that the mesoface content is small (both 70% by weight)), which is characterized by including the following steps: ) Hydrotreating the decant oil until the average number of hydrogen atoms per molecule of the decant oil increases by about 2 to about 3. (B) Distilling the hydrogen-treated decant oil to form f. C) A step of processing this pitch to convert it into mesoface pitch. 6. It is characterized by including the following steps. (a) A process of hydrogen-treating the decanted oil until the average number of water-reduced atoms per molecule of the decanted oil is about 2 to about 3. (b) Hydrogen A process of subjecting the treated decant oil to a heat-pressure treatment to create a tar residue. (c) A process of distilling this tar residue to form pitch. B) Processing this pitch to convert it into mesoface pitch. 7. A method for producing carbon fiber, characterized by including the following steps: (a) Hydrogenating the decant oil until the average number of water X atoms per molecule of the decant oil increases by about 2 to about 3. (b) Distilling the hydrogen-treated decant oil to form pitch. (c) Processing this pitch to produce mesoface pitch, provided that it has a mesoface content of at least 70% by weight. ) to 1) A process for producing carbon fiber from this mesoface pitch. 8. A method for producing carbon fiber, characterized by including a step of manure. 0) Average hydrogen per molecule of decant oil Hydrotreating the decanted oil until the number of atoms increases by about 2 to about 3 atoms. (b) A step in which the hydrogen-treated decant oil is subjected to heat-pressure treatment to form a tar residue. (c) A process of distilling this tar residue to form pitch. ) processing this pitch to convert it into mesoface pitch, provided that it has a mesoface content of at least 70% by weight; (e) A process of manufacturing carbon fiber from this membrane pitch.