CN112442385A

CN112442385A - Process for preparing spinnable pitch

Info

Publication number: CN112442385A
Application number: CN201910834338.XA
Authority: CN
Inventors: 熊杰明; 宋以常; 李佩佩; 马文明; 李海军; 何启军; 倪前银
Original assignee: China Petroleum and Chemical Corp
Current assignee: China Petroleum and Chemical Corp
Priority date: 2019-09-03
Filing date: 2019-09-03
Publication date: 2021-03-05
Anticipated expiration: 2039-09-03
Also published as: CN112442385B

Abstract

The invention relates to the field of pitch-based carbon fibers, and discloses a method for preparing spinnable pitch, which comprises the following steps: (1) extracting refined asphalt by using a mixed solvent at the temperature of 150-180 ℃ to obtain a supernatant and a lower heavy phase; the mixed solvent is a mixture containing a petroleum product and methyl naphthalene oil, the distillation range of the petroleum product is within 150-210 ℃, and the distillation range of the methyl naphthalene oil is within 230-260 ℃; the mass ratio of the petroleum product to the methyl naphthalene oil is 1: 0.1-0.8; the mass ratio of the refined asphalt to the mixed solvent is 1: 1-3; (2) and distilling the lower heavy phase, and removing the mixed solvent to obtain the spinnable asphalt. The method can solve the problems of over low softening point, over high QI, high vacuum degree requirement in the production process, high equipment investment, high product cost and the like of the conventional spinnable asphalt.

Description

Process for preparing spinnable pitch

Technical Field

The invention relates to the field of pitch-based carbon fibers, in particular to a method for preparing spinnable pitch.

Background

The pitch-based carbon fiber is a carbon fiber prepared by taking substances such as pitch and the like rich in polycyclic aromatic hydrocarbon as raw materials through polymerization, spinning, non-melting and carbonization, and is divided into general-grade pitch carbon fiber and high-performance pitch carbon fiber according to the difference of performances. The preparation method of the general-purpose pitch-based carbon fiber generally comprises the steps of taking isotropic spinnable pitch as a raw material, and obtaining the general-purpose pitch-based carbon fiber after melt spinning, pre-oxidation and carbonization treatment. Among them, the most basic conditions for preparing a general-purpose pitch-based carbon fiber are that the softening point of the spinnable pitch needs to be raised to about 250 ℃ and the QI (quinoline insoluble) content is less than 1.0%.

At present, methods for improving the softening point of asphalt mainly comprise two types, one is an oxidation method, and the specific process is that refined asphalt with the softening point of about 120 ℃ and basically no quinoline insoluble is used as a raw material, and the oxidation and crosslinking of asphalt molecules are promoted through air or oxygen oxidation treatment, so that the molecular weight is obviously improved, and the softening point is up to 220-280 ℃. However, the main problems of this method are: a large amount of tail gas is produced in the oxidation process, wherein the tail gas contains a large amount of carcinogens, nitrides and the like, so that serious air pollution is caused; air or oxygen is not distributed uniformly in the reactor, so that the reaction degree is not uniform, and the softening point is not uniform; the air concentration in certain areas of the reactor is too high, so that the temperature is too high, the oxidation is excessive, and carbon black-like substances, intermediate and equal solid substances are generated, and the spinning effect is directly influenced. The other method is a distillation method, which completely depends on a molecular distillation method with high vacuum to remove light components so as to improve the softening point of asphalt, and requires high operation temperature and extremely high vacuum degree, such as absolute pressure of 120Pa or less, and requires large equipment investment, thus being very difficult to implement industrially, having high production cost and being easy to produce secondary QI. In addition, there is a literature that uses lower operating temperatures but produces spinnable pitches with very low softening points.

In general, for a general-purpose pitch-based carbon fiber, low QI and high softening point are a pair of contradictions that are difficult to solve, and restrict the development of pitch-based carbon fibers. For the reasons, the quality of domestic asphalt-based carbon fiber products is not high, and industrialization is rare.

Disclosure of Invention

The present invention aims to overcome the above problems of the prior art and to provide a process for preparing a spinnable pitch. The method can obviously improve the softening point of the asphalt and effectively inhibit the generation of secondary QI, thereby obtaining the spinnable asphalt with high softening point and low QI content, and the method has simple process and reduces the equipment investment.

In order to achieve the above object, the present invention provides a method for preparing spinnable pitch, comprising:

(1) extracting refined asphalt by using a mixed solvent at 150-180 ℃ to obtain a supernatant and a lower heavy phase; wherein the content of the first and second substances,

the softening point of the refined asphalt is 110-130 ℃, and the QI content is less than or equal to 0.1 wt%;

the mixed solvent is a mixture containing a petroleum product and methyl naphthalene oil, the distillation range of the petroleum product is within 150-210 ℃, and the distillation range of the methyl naphthalene oil is within 230-260 ℃; the mass ratio of the petroleum product to the methyl naphthalene oil is 1: 0.1-0.8;

the mass ratio of the refined asphalt to the mixed solvent is 1: 1-3;

(2) and distilling the lower heavy phase, and removing the mixed solvent to obtain the spinnable asphalt.

The method can solve the problems of over low softening point, over high QI, high vacuum degree requirement in the production process, high equipment investment, high product cost and the like of the conventional spinnable asphalt. The method of the invention not only can produce spinnable asphalt with high softening point and low QI, but also can realize the industrialized production of the asphalt-based carbon fiber, reduce the production difficulty and cost of the spinnable asphalt and make the product more competitive.

In the extraction process, the mixed solvent and the asphalt are added simultaneously, so that the corresponding equipment is simple, the flow is shorter, and the equipment investment is reduced; the lower heavy phase obtained by extraction has good fluidity, the separation process is simple and easy, and the method is suitable for industrial continuous operation; the vacuum degree requirement in the distillation process is obviously reduced, and the operation difficulty and the cost are further reduced. The method can effectively inhibit the generation of the sub QI, and the obtained spinnable asphalt has low QI content. Because only the solvent before 260 ℃ in the asphalt needs to be distilled out, the operation temperature and the vacuum degree are not required to be too high. In contrast, the conventional molecular distillation method is generally carried out under vacuum with absolute pressure less than or equal to 120Pa, has extremely high implementation difficulty, is easy to cause the problem of secondary QI growth, and has limited improvement degree of a softening point.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a method for preparing spinnable asphalt, which comprises the following steps:

(1) extracting refined asphalt with mixed solvent, and separating to obtain supernatant and lower heavy phase;

In the invention, the refined asphalt used for preparing the spinnable asphalt has a softening point of 110-130 ℃ and a QI content of less than or equal to 0.1 weight percent. The refined asphalt can be obtained commercially or prepared by referring to the prior art, for example, by subjecting the catalytic slurry oil to high temperature thermal polymerization, reduced pressure distillation and centrifugal separation, and the specific operation is well known in the art and will not be described herein.

In the present invention, the mixed solvent is a mixture containing a petroleum product and a methyl naphthalene oil.

In the invention, the distillation range of the petroleum product is within 150-210 ℃, which means that the petroleum product has an initial boiling point of more than or equal to 150 ℃ and a dry point of less than or equal to 210 ℃. The invention has no special requirements on the types of the petroleum products and can be various oil products meeting the distillation range requirements. Preferably, the petroleum product is selected from kerosene and/or straight run gasoline meeting the above-mentioned distillation range requirements.

In the invention, the distillation range of the methyl naphthalene oil is 230-260 ℃, specifically the methyl naphthalene oil with an initial boiling point of more than or equal to 230 ℃ and a dry point of less than or equal to 260 ℃.

In the invention, the mass ratio of the petroleum product to the methyl naphthalene oil is 1: 0.1-0.8. Preferably, the mass ratio of the petroleum product to the methyl naphthalene oil is 1 to (0.1-0.5), so that the yield of the spinnable asphalt can be further improved.

In the invention, the mass ratio of the refined asphalt to the mixed solvent is 1: 1-3. Preferably, the mass ratio of the refined asphalt to the mixed solvent is 1: 1.5-3, so that the yield of the spinnable asphalt can be further improved.

In the invention, the extraction temperature is 150-180 ℃.

In one embodiment, in step (1), the extraction process comprises: and stirring the mixed solvent and the refined asphalt for 0.5-3.0 hours, and then standing for 0.5-5 hours.

The inventor of the invention finds in research that the methyl naphthalene oil has high solubility on the refined asphalt, is convenient to dissolve with macromolecular heavy asphalt components in the refined asphalt at the extraction temperature, and enables a heavy phase separated by extraction to have good fluidity; moreover, the boiling point range of the solvent is narrow, so that the solvent is not too high in boiling point with the petroleum product and is easy to separate from the petroleum product, and the solvent can be effectively removed in the subsequent heavy-phase asphalt distillation process without too high temperature and vacuum degree, thereby obviously reducing the difficulty of molecular distillation and the cost of industrial implementation. The method can avoid the problem that other solvents are additionally introduced to remove the extraction solvent in the heavy phase or the harsh operation condition of further increasing the temperature or lowering the absolute pressure is needed after the heavy phase is obtained by the conventional extraction method, and therefore, the method has the characteristics of low cost, shorter flow and simpler operation.

In the step (1), a supernatant and a lower heavy phase can be obtained by the extraction. The supernatant contains mainly a large amount of solvent and a low molecular weight asphalt component. Optionally, the method further comprises: and distilling the supernatant liquor, and recycling the separated mixed solvent for the extraction.

In the invention, the lower heavy phase mainly comprises heavy components with large molecular weight and a small amount of solvent, and the viscosity of the lower heavy phase is usually 100-300 mPa · s at the extraction temperature (namely the settling temperature), so that the lower heavy phase has better fluidity, and on one hand, the separation of the solvent and the heavy components is easy to realize, and on the other hand, the continuous production of the spinnable asphalt is convenient to realize.

In the step (2), the distillation conditions comprise: the temperature is 300-350 ℃, and the pressure is 300-1000 Pa. In the present invention, the pressure means an absolute pressure.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples,

the distillation range of the methyl naphthalene oil is 230-260 ℃, and the methyl naphthalene oil is purchased from Xinnuo Xinnaxing fine chemical industry Co., Ltd;

the distillation range of the straight-run gasoline is 150-180 ℃, and the straight-run gasoline is purchased from Beijing Yanshan petrochemical company.

The softening point of the refined asphalt is measured according to a cup and ball method;

the softening point of the spinnable pitch is measured according to a needle penetration method;

the QI content (hereinafter referred to as "QI") was measured in accordance with GB/T2293-2008 (test method for quinoline insolubles in coker bitumen products).

Example 1

To 200g of refined asphalt (softening point 110 ℃ C., QI ═ 0.08%) was added 400g of a mixed solvent composed of straight-run gasoline and methyl naphthalene oil (mass ratio of straight-run gasoline to methyl naphthalene oil was 1: 0.3), and the mixture was stirred and mixed at 150 ℃ for 2.0 hours, and then allowed to stand for 0.5 hour, and the supernatant was separated and removed to obtain a lower heavy phase having fluidity (150 ℃ C., viscosity 300 mPas). The lower heavy phase was distilled at 350 ℃ and 1000Pa to remove the solvent, yielding 80g of spinnable pitch. The spinnable pitch has a softening point of 240 ℃ and QI of 0.5%.

The spinnable asphalt is spun at 345 ℃ and 0.016MPa at the linear speed of 450 m/min, the spinning duration is 15 min, and the yarn diameter is 20 mu m.

Example 2

To 200g of refined asphalt (softening point 130 ℃ C., QI ═ 0.06%) was added 600g of a mixed solvent composed of kerosene (distillation range 150 to 210 ℃ C., from Beijing Tian Minn petrochemical company) and methyl naphthalene oil (mass ratio of kerosene to methyl naphthalene oil 1: 0.1), and the mixture was stirred and mixed at 180 ℃ for 1.0 hour, and then allowed to stand for 0.5 hour, and the supernatant was separated and removed to obtain a lower heavy phase having fluidity (viscosity at 180 ℃ C., 260 mPas). The lower heavy phase was distilled at 330 ℃ and 310Pa to remove the solvent, yielding 90g of spinnable pitch. The spinnable pitch has a softening point of 260 ℃ and QI of 0.7%.

The spinnable asphalt is spun at 370 ℃ and 0.016MPa at the linear speed of 400 m/min, the spinning duration is 13 min, and the yarn diameter is 18 mu m.

Example 3

200g of a mixed solvent composed of kerosene (same as in example 2) and methyl naphthalene oil (the mass ratio of kerosene to methyl naphthalene oil was 1: 0.8) was added to 200g of refined asphalt (softening point 120 ℃ C., QI ═ 0.05%), and the mixture was stirred and mixed at 180 ℃ for 1.5 hours, and then allowed to stand for 0.5 hour, and the supernatant was separated and removed to obtain a lower heavy phase having fluidity (viscosity at 180 ℃ C., 100 mPas). The lower heavy phase was distilled at 300 ℃ under 500Pa to remove the solvent, yielding 75g of spinnable pitch. The spinnable pitch had a softening point of 230 ℃ and QI of 0.5%.

The spinnable pitch was spun at 330 ℃ and 0.015MPa at a line speed of 420 m/min for a duration of 17 min and a diameter of 15 μm.

Example 4

A spinnable asphalt was prepared by following the procedure of example 1, except that the amount of the mixed solvent was adjusted to 300g, and the mass ratio of kerosene to methylnaphthalene oil was adjusted to 1: 0.5, to obtain 80g of spinnable asphalt. The spinnable pitch had a softening point of 245 ℃ and QI of 0.7%.

The spinnable pitch is spun at 350 ℃ and 0.015MPa at a linear speed of 430 m/min for a spinning duration of 16 min and a yarn diameter of 19 μm.

Comparative example 1

A spinnable asphalt was prepared by following the procedure of example 1, except that the amount of the mixed solvent was adjusted to 800g to obtain 52g of spinnable asphalt. The spinnable pitch has a softening point of 248 ℃ and a QI of 0.8%.

The spinnable pitch is spun at 355 ℃ and 0.016MPa at the linear speed of 450 m/min, the spinning duration is 12 min, and the yarn diameter is 20 mu m.

Compared with example 1, the yield of pitch is significantly lower, QI is increased and spinnability is reduced.

Comparative example 2

Spinnable asphalt was prepared according to the method of example 1, except that 48g of spinnable asphalt was obtained by adjusting the mass ratio of petroleum products to methyl naphthalene oil to 1: 1.5 in the mixed solvent. The spinnable pitch has a softening point of 260 ℃ and QI of 0.83%.

The spinnable asphalt is spun at 360 ℃ and 0.016MPa, the linear speed is 450 m/min, the spinning duration is 11 min, and the yarn diameter is 20 mu m.

Compared with example 1, the yield of pitch is lower, QI is increased and spinnability is reduced.

Comparative example 3

Adding 400g of a mixed solvent (the mass ratio of kerosene to methyl naphthalene oil is 1: 0.3) consisting of another kerosene (210-265 ℃ C., from Beijing Tianyi petrochemical technology Co., Ltd.) and methyl naphthalene oil into 200g of refined asphalt (the softening point is 110 ℃ C., and the QI is 0.08%), stirring and mixing at 180 ℃ for 2.0h, standing for 1h, and separating and removing a supernatant to obtain a lower heavy phase. The lower heavy phase was distilled at 350 ℃ and 1000Pa to remove the solvent, yielding 90g of pitch product. The softening point of the bitumen product was 255 ℃ and QI ═ 0.6%.

The pitch product is spun at 360 ℃ and 0.016MPa, the linear speed is 300 m/min, the duration is only 2 min, and filaments are easy to break in the spinning process, so that filaments cannot be obtained.

In this comparative example, kerosene could not be completely removed in distillation and was mixed in the asphalt product. To completely remove the kerosene to obtain spinnable pitch, a large amount of solvent (such as wash oil) is added additionally, mixed and stirred, and then distilled. Resulting in excessive solvent usage and complex operation.

Comparative example 4

To 200g of refined asphalt (softening point 130 ℃ C., QI 0.06%) was added 600g of a mixed solvent (mass ratio of kerosene to wash oil 1: 0.1) composed of kerosene (same as in example 2) and wash oil (distillation range 227-290 ℃ C., available from Tangshan division of carbon chemical Co., Ltd., Cooper (China)), followed by stirring and mixing at 180 ℃ for 1.0h, standing for 0.5h, separating and removing the supernatant, distilling the obtained lower heavy phase at 350 ℃ C., 300Pa, and removing the solvent to obtain 83g of an asphalt product. The softening point of the bitumen product was 210 ℃ and QI ═ 0.7%. The softening point is too low to be suitable for carbon fiber.

In this comparative example, the wash oil was not completely removed during distillation, resulting in a final softening point that was too low. If the wash oil is to be removed, higher temperatures or lower absolute pressures are required to achieve the spinnable pitch softening point requirements.

Comparative example 5

200g of a mixed solvent (the mass ratio of kerosene to anthracene oil was 1: 0.8) composed of kerosene (same as in example 2) and anthracene oil (the distillation range was 310 to 390 ℃ and obtained from down mountain division, a carbon chemical co., ltd., cobbs (china)) was added to 200g of refined asphalt (softening point 120 ℃ C., QI ═ 0.05%), and the mixture was stirred and mixed at 210 ℃ for 1.5 hours, then allowed to stand for 0.5 hour, and the supernatant was separated and removed, and the lower heavy phase obtained was distilled at 350 ℃ C., 300Pa to remove the solvent, whereby 97g of an asphalt product was obtained. The softening point of the bitumen product was 200 ℃ and QI ═ 0.5%. The softening point is too low to be suitable for carbon fiber.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method of preparing a spinnable pitch, the method comprising:

(1) extracting refined asphalt by using a mixed solvent at the temperature of 150-180 ℃ to obtain a supernatant and a lower heavy phase;

the mass ratio of the refined asphalt to the mixed solvent is 1: 1-3;

2. The method according to claim 1, wherein the refined asphalt has a softening point of 110 to 130 ℃ and a QI content of 0.1 wt.% or less.

3. The method of claim 1, wherein in step (1), the extracting comprises: and stirring the mixed solvent and the refined asphalt for 0.5-3.0 hours, and then standing for 0.5-5 hours.

4. The method according to any one of claims 1-3, wherein the petroleum product is kerosene and/or straight run gasoline.

5. The method according to any one of claims 1 to 4, wherein the mass ratio of the petroleum product to the methyl naphthalene oil is 1: 0.1 to 0.5.

6. The method according to any one of claims 1 to 5, wherein the mass ratio of the refined asphalt to the mixed solvent is 1: 1.5 to 3.

7. The method of claim 1, wherein in step (2), the distillation conditions comprise: the temperature is 300-350 ℃, and the pressure is 300-1000 Pa.