Isotropic pitch with excellent spinning performance and preparation method and application thereof

Abstract

The present application relates to a kind of isotropic pitch of excellent spinning performance and its preparation method and application, belong to pitch technical field.The preparation method of isotropic pitch-based carbon fiber in prior art is relatively complex, the equipment requirement is high, the cost is high, and the spinning performance is poor, etc.The preparation method of the present application, first, aromatic-rich heavy oil is used as raw material, polyaldehyde oxygen-containing polymer is used as co-carbonization reagent, and low polycondensation product with different molecular weights is prepared by co-carbonization reaction;Then, using supercritical / subcritical extraction process, different extractants with different solubility parameters are used to extract low polycondensation product, to obtain the residue containing dimmer with molecular weight of 330-450;Finally, the residue is distilled, and the extractant is recovered, and the obtained dimmer is subjected to thermal polycondensation treatment by fluidized bed tubular reactor, and combined with flow control, to obtain isotropic pitch.The spinning performance of the isotropic pitch is excellent, and the carbon fiber with excellent mechanical properties can be prepared.

Description

Technical Field

[0001] This invention relates to an isotropic pitch with excellent spinning properties, its preparation method and application, and particularly to the application of the isotropic pitch in the preparation of carbon fibers, belonging to the field of pitch technology. Background Technology

[0002] Pitch-based carbon fiber is a fiber material with extremely high carbon content (>90%) and excellent comprehensive performance. It has a series of excellent properties such as low density, high specific strength, high specific modulus, excellent resistance to extreme temperatures, outstanding corrosion resistance, fatigue resistance, creep resistance, high electrical conductivity, high thermal conductivity and low coefficient of thermal expansion. It is widely used in aerospace, transportation, chemical industry, general engineering and other fields.

[0003] Pitch-based carbon fiber can be further divided into isotropic pitch-based carbon fiber and mesophase pitch-based carbon fiber. Isotropic pitch-based carbon fiber, made from isotropic pitch, is also known as general-purpose pitch-based carbon fiber. Compared to mesophase pitch-based carbon fiber, isotropic pitch-based carbon fiber has advantages such as refined raw materials, simple processing, and low production costs, resulting in huge market demand. However, compared to foreign countries, my country's research and development of pitch-based carbon fiber is relatively recent, with only one general-purpose pitch-based carbon fiber production line producing just over 200 tons per year. This has led to a low domestic production rate and insufficient supply in my country's pitch-based carbon fiber market, further restricting my country's economic and social development. Therefore, developing and producing high-strength isotropic pitch-based carbon fiber is a major challenge facing my country's carbon fiber industry.

[0004] Studies have found that the mechanical properties of carbon fibers are closely related to the molecular composition and spatial configuration of isotropic pitch. Generally, the higher the linearity of pitch molecules, the better the spinning performance of isotropic pitch, and the higher the mechanical properties of the corresponding carbon fibers. This is because, during melt spinning, under the influence of shear forces, pitch molecules with high linearity are more likely to align within the carbon fibers, resulting in higher mechanical properties. To improve the linearity of pitch molecules, a methylene bridging structure is introduced into the pitch molecules through bromination-debromination. This method is highly effective, but the process is relatively complex, requires sophisticated equipment, and liquid bromine is highly corrosive, producing byproducts such as HBr. Improper operation can severely pollute the environment, limiting the large-scale application of this process. Furthermore, the complex production process further increases the production cost of isotropic pitch-based carbon fibers.

[0005] CN115466626B discloses a method for preparing high-quality isotropic pitch. The method first involves adding methylnaphthalene and a brominating agent to a solvent and carrying out a bromination reaction under visible light catalysis to obtain brominated methylnaphthalene. This brominated methylnaphthalene is then mixed with coal tar pitch and subjected to a co-carbonization reaction under an inert gas atmosphere to obtain the high-quality isotropic pitch. Carbon fibers can then be produced using this as a raw material. This method addresses the low reactivity of coal tar pitch to some extent. However, it involves the use of highly corrosive liquid bromine, requires specialized production equipment, and results in a low yield of isotropic pitch, leading to increased production costs.

[0006] CN115873617A discloses a method for preparing petroleum-based isotropic high softening point asphalt. First, a petroleum-based aromatic hydrocarbon-rich feedstock is enriched at 250-350℃ using nitrogen purging at a certain temperature. Then, the temperature is raised to 400-420℃ and reacted for 13 hours to obtain high softening point isotropic asphalt. However, the asphalt produced by this method exhibits a high degree of molecular condensation, leading to an increased content of quinoline insolubles and a decrease in the asphalt's spinning properties.

[0007] CN116288816A discloses a method for preparing isotropic pitch-based carbon fibers. This method uses ethylene tar as a raw material, first heat-treating it under a nitrogen atmosphere, then mixing it with coal tar pitch while simultaneously introducing nitrogen-bromine succinimide, and finally irradiating it with a xenon lamp at a certain temperature to remove benzene and obtain isotropic pitch. However, this method has a complex process route, high production costs, and the resulting pitch has a high softening point and poor spinning performance. Summary of the Invention

[0008] In view of this, in order to solve the technical problems of relatively complex operation process, high equipment requirements, high cost and poor spinning performance of the preparation method of isotropic pitch-based carbon fiber in the prior art, the present invention provides an isotropic pitch with excellent spinning performance, its preparation method and application.

[0009] This invention utilizes a low-temperature controllable induced co-carbonization reaction to induce shallow polycondensation of aromatic molecules in feedstock oil, synthesizing a dimer linked by methylene groups. The dimer is then selectively enriched using a supercritical / subcritical extraction process. A fluidized bed tubular reactor combined with flow control further promotes the polymerization of the dimer, allowing the methylene bridging structure to be "inherited" into isotropic pitch molecules. This method optimizes the structural composition and spatial configuration of pitch molecules, achieving a simultaneous improvement in pitch spinning performance and carbon fiber mechanical properties.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0011] This invention provides a continuous method for preparing isotropic pitch with excellent spinning properties, comprising the following steps:

[0012] (1) Using aromatic heavy oil as raw material and polyaldehyde oxygen-containing polymer as co-carbonizing agent, the reaction parameters are adjusted to prepare low condensation products with different molecular weights through co-carbonization reaction.

[0013] (2) Using supercritical / subcritical extraction technology, extractants with different solubility parameters are selected to extract the low condensation product prepared in step (1), and the extraction parameters are adjusted to obtain raffinate containing dimers with a molecular weight of 330-450.

[0014] (3) The extract prepared in step (2) is distilled to recover the extractant, and the resulting dimer is thermally polycondensed in a fluidized bed tubular reactor. Combined with the flow control of the dimer, linear polycyclic aromatic hydrocarbon macromolecules with a molecular weight of 820-1130 and a softening point of 250-290℃ are prepared to obtain isotropic asphalt.

[0015] Preferably, in step (1), the aromatic-rich heavy oil is one or more of the following: catalytic cracking slurry oil, ethylene tar, atmospheric residue, vacuum residue, high-temperature coal tar, and bamboo tar.

[0016] Preferably, in step (1), the co-carbonizing agent is one or more of trioxymethylene, pentaoxymethylene, and polyacetaldehyde; more preferably, the co-carbonizing agent is trioxymethylene.

[0017] Preferably, in step (1), the amount of the co-carbonizing agent is 3wt%-10wt% of the mass of the aromatic-rich heavy oil.

[0018] Preferably, in step (1), the co-carbonization reaction temperature is 160-200℃ and the reaction time is 0.5-1.5h; more preferably, the co-carbonization reaction temperature is 180℃ and the reaction time is 1.1h.

[0019] Preferably, in step (1), the molecular weight range of the low condensation product is 100-550.

[0020] Preferably, in step (2), the equipment used in the supercritical / subcritical extraction process is a supercritical extraction tower with a top temperature of 400-430℃, a middle temperature of 370-390℃, a bottom temperature of 310-370℃, an extraction pressure of 1.6-3.2MPa, and an extractant selected from one or more of toluene, N-methylpyrrolidone, chloroform, carbon tetrachloride, furfural, and tetrahydrofuran. The mass ratio (extractant-to-oil ratio) of extractant to low condensation product is 5:1-9:1.

[0021] More preferably, the temperature at the top of the column is 425°C, the temperature in the middle of the column is 381°C, the temperature at the bottom of the column is 330°C, and the extraction pressure is 2.2 MPa;

[0022] More preferably, the extractant is a mixed solvent of toluene, furfural, and chloroform in a mass ratio of 1:1:4;

[0023] More preferably, the extractant and the low-condensation product are mixed in a countercurrent manner.

[0024] Preferably, in step (2), the methylene carbon content (C) in the dimer is... CH2 )≥15wt%, aromatic content≥75wt%, asphaltene content≤4wt%, ash content≤5μg / g.

[0025] Preferably, in step (3), the distillation temperature is 160-210℃ and the pressure is -20KPa to -40KPa; more preferably, the distillation temperature is 200℃ and the pressure is -30KPa.

[0026] Preferably, in step (3), the fluidized bed tubular reactor is divided into three temperature zones: the first temperature zone has a processing temperature of 220-270℃, the second temperature zone has a processing temperature of 300-340℃, and the third temperature zone has a processing temperature of 350-380℃.

[0027] Preferably, in step (3), the flow rate of the dimer is 20-50 ml / min.

[0028] Preferably, in step (3), the methylene carbon content (C) in the isotropic asphalt is... CH2 ≥11wt%.

[0029] The present invention also provides isotropic asphalt prepared by the above-described continuous preparation method of isotropic asphalt.

[0030] The present invention also provides the application of the above-mentioned isotropic pitch in the preparation of carbon fibers.

[0031] Preferably, isotropic pitch is melt-spinned, pre-oxidized, and carbonized to obtain carbon fibers.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention discloses a continuous preparation method for isotropic pitch with excellent spinning properties. Using aromatic-rich heavy oil as raw material and the pyrolysis products of polyaldehyde oxygen-containing polymers as crosslinking agents, a co-carbonization reaction at low temperature is employed to link the aromatic components in the aromatic-rich heavy oil together through a methylene bridging structure, forming dimers with a shallow degree of condensation. This structure not only improves the solubility of the condensation product, making it easier and more efficient to enrich in subsequent supercritical / subcritical extraction processes, but the methylene bridging structure is also "inherited" into the isotropic pitch molecules, improving the linearity of the pitch molecules and thus enhancing the spinnability of the pitch. Furthermore, in the supercritical / subcritical extraction process, by controlling the extraction parameters of the supercritical extraction tower, the efficient enrichment of dimers in the condensation product is ensured, while unreacted raw material components are also removed and reintroduced into the reaction system as raw materials, improving the utilization rate of the raw materials. To allow more methylene bridging structures to enter the asphalt molecules, a multi-temperature zone fluidized bed tubular reactor is used to further condense the dimer, forming polycyclic aromatic hydrocarbon molecules with higher molecular weight. This multi-temperature zone fluidized bed tubular reactor not only increases the reaction rate, but also better preserves the methylene bridging structures in the dimer, thereby improving the linearity of the asphalt molecules.

[0034] The continuous preparation method of isotropic pitch with excellent spinning performance of the present invention has a relatively simple operation process, low equipment requirements, and low cost.

[0035] The isotropic pitch of this invention exhibits excellent spinning properties. During melt spinning, under the influence of shear forces, it readily forms oriented patterns within the fibers, thereby reducing the number of microscopic defects and improving the mechanical properties of the carbon fibers. Testing shows that the carbon fibers have a tensile strength ≥1.4 GPa and a tensile modulus ≥50 GPa. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are only some specific embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A schematic diagram of the process flow for the continuous preparation method of isotropic pitch with excellent spinning performance provided by the present invention. Detailed Implementation

[0038] To further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0039] The continuous preparation method of isotropic pitch with excellent spinning properties according to the present invention includes the following steps:

[0040] (1) Using aromatic heavy oil as raw material and polyaldehyde oxygen-containing polymer as co-carbonizing agent, the reaction parameters are controlled and the aromatic molecules in the aromatic heavy oil are linked through the methylene bridging structure by low-temperature controllable co-carbonization reaction to obtain low-molecular-weight polycondensation products with different molecular weights.

[0041] (2) Using supercritical / subcritical extraction technology, extractants with different solubility parameters are selected to extract the low condensation product prepared in step (1), and the extraction parameters are adjusted to obtain raffinate containing dimers with a molecular weight of 330-450. The extracted light distillate oil can be discharged and stored.

[0042] (3) The extract prepared in step (2) is distilled to recover the extractant, and the resulting dimer is thermally polycondensed in a fluidized bed tubular reactor. Combined with the flow control of the dimer, linear polycyclic aromatic hydrocarbon macromolecules with a molecular weight of 820-1130 and a softening point of 250-290℃ are prepared to obtain isotropic asphalt.

[0043] In this invention, the aromatic-rich heavy oil is preferably one or more selected from catalytic cracking slurry oil, ethylene tar, atmospheric residue, vacuum residue, high-temperature coal tar, and bamboo tar. The co-carbonizing agent is preferably one or more selected from paraformaldehyde, pentaformaldehyde, and polyacetaldehyde, more preferably paraformaldehyde. The amount of the co-carbonizing agent is preferably 3wt%-10wt% of the mass of the aromatic-rich heavy oil. The co-carbonization reaction temperature is preferably 160-200℃, and the reaction time is 0.5-1.5h; more preferably, the co-carbonization reaction temperature is 180℃, and the reaction time is 1.1h. The molecular weight of the low-polymerization product is preferably in the range of 100-550, typically determined by gel permeation chromatography.

[0044] In this invention, the preferred supercritical / subcritical extraction process uses a supercritical extraction column with a top temperature of 400-430°C, a middle temperature of 370-390°C, a bottom temperature of 310-370°C, and an extraction pressure of 1.6-3.2 MPa. Preferably, the top temperature is 425°C, the middle temperature is 381°C, the bottom temperature is 330°C, and the extraction pressure is 2.2 MPa. The extractant is one or more of toluene, N-methylpyrrolidone, chloroform, carbon tetrachloride, furfural, and tetrahydrofuran; preferably, the extractant is a mixed solvent of toluene, furfural, and chloroform in a mass ratio of 1:1:4. The mass ratio (extractant-to-oil ratio) of the extractant to the low-condensation product is 5:1-9:1. Preferably, the extractant and the low-condensation product are mixed countercurrently.

[0045] In this invention, flash distillation is preferred, with a distillation temperature of 160-210℃ and a pressure of -20KPa to -40KPa, preferably 200℃ and -30KPa. Utilizing 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The content of aromatics in the dimer was ≥15wt%, and the content of asphaltenes was ≤4wt%, and the ash content was ≤5μg / g, as determined by four-component analysis. A fluidized bed tubular reactor with three temperature zones was preferred: the first zone had a processing temperature of 220-270℃, the second zone 300-340℃, and the third zone 350-380℃. The preferred flow rate of the dimer was 20-50 ml / min. 13 C10-NMR analysis revealed the methylene carbon content (C10) in isotropic bitumen. CH2 ≥11wt%.

[0046] like Figure 1 As shown, as a preferred embodiment, the continuous preparation method of the isotropic pitch with excellent spinning performance of the present invention is described in conjunction with the apparatus. The steps are as follows: First, the aromatic-rich heavy oil in the raw oil storage tank is transported to the reaction vessel through a pipeline pump and heat exchanger. At the same time, the co-carbonizing reagent stored in the crosslinking agent storage tank is transported to the reaction vessel. The reaction parameters are adjusted, and the aromatic molecules in the aromatic-rich heavy oil are linked through a methylene bridging structure by a low-temperature controllable induced co-carbonization reaction to obtain low-molecular-weight polycondensation products. The low-molecular-weight polycondensation products enter the supercritical extraction tower through a pipeline metering pump and heat exchanger. At the same time, the extractant in the extract liquid storage tank is transported through a pipeline pump. The product is fed into a supercritical extraction tower, where the extractant and low-molecular-weight polycondensation product come into contact. Light distillate oil is obtained at the top of the tower and stored in a light distillate oil receiving tank. Raffinate containing dimers with a molecular weight of 330-450 is obtained at the bottom of the tower and discharged into a dimer storage tank. The raffinate in the dimer storage tank is first transported to a flash evaporation tower via a heat exchanger and pipeline pump to recover the extractant. The recovered extractant is then transported to a recovered extractant storage tank via a vacuum pump, and can then be reused in the extractant storage tank. The enriched dimers are transported to a fluidized bed tubular reactor via a pipeline metering pump for thermal polycondensation treatment to obtain isotropic asphalt, which is stored in an isotropic asphalt storage tank. It should be noted that the above apparatus is only for more clearly illustrating the preparation method of the present invention; those skilled in the art can select other suitable apparatus for the preparation method of the present invention as needed.

[0047] The isotropic pitch of this invention can be used in the preparation of carbon fibers. There are no particular limitations on the specific application method; methods for preparing carbon fibers from pitch in the prior art can be referenced, mainly including melting and spinning the isotropic pitch, pre-oxidizing it, and then carbonizing it to obtain carbon fibers. Preferably, carbon fiber precursors are obtained by melt spinning in a nitrogen atmosphere at 305℃-335℃, pre-oxidizing them in an air atmosphere (50ml / min) at 275℃, and then carbonizing them in a nitrogen atmosphere (100ml / min) at 1100℃ to obtain carbon fibers. Due to the excellent spatial configuration of the isotropic pitch of this invention, the carbon fibers prepared from it have excellent tensile properties.

[0048] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0049] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0050] Example 1

[0051] 2 kg of catalytic cracking slurry was weighed and pumped into a reactor using a pipeline pump. 100 g of paraformaldehyde was added to the reactor, and the reaction was carried out at 160°C for 1.1 h. The reaction product was then transferred to a supercritical extraction tower, with the top temperature set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, and the mass ratio of extractant to reaction product (extractant-to-oil ratio) was 7:1. The raffinate containing dimers was then transferred to a flash tank to recover the extractant. The flash temperature was set... At a temperature of 200℃ and a pressure of -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain isotropic pitch. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 305℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0052] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 337. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2The asphalt contained 15.2 wt% aromatics, 3.6 wt% asphaltene, and 4 μg / g ash, as determined by four-component analysis. The resulting isotropic asphalt had a weight-average molecular weight of 846 and a softening point of 255℃. 13 C10-NMR analysis determined the methylene carbon content (C10) in asphalt. CH2 The carbon fiber obtained by adding 14.1 wt% has a tensile strength of 1.4 GPa and a tensile modulus of 51 GPa.

[0053] Example 2

[0054] 2 kg of catalytic cracking slurry was weighed and pumped into a reactor using a pipeline pump. 100 g of polyacetaldehyde was added to the reactor, and the reaction was carried out at 200°C for 1.1 h. The reaction product was then transferred to a supercritical extraction tower, with the top temperature set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, and the mass ratio of extractant to reaction product (extractant-to-oil ratio) was 7:1. The raffinate containing dimers was then transferred to a flash tank to recover the extractant. The flash temperature was set... At a temperature of 200℃ and a pressure of -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain isotropic pitch. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 317℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0055] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 336. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The asphalt contained 16.3 wt% aromatics, 3.7 wt% asphaltene, and 4.6 μg / g ash, as determined by four-component analysis. The resulting isotropic asphalt had a weight-average molecular weight of 874 and a softening point of 267℃. 13 C10-NMR analysis determined the methylene carbon content (C10) in asphalt. CH2 The carbon fiber obtained by adding 11.1 wt% has a tensile strength of 1.43 GPa and a tensile modulus of 57 GPa.

[0056] Example 3

[0057] 2 kg of catalytic cracking slurry was weighed and pumped into a reactor using a pipeline pump. 100 g of paraformaldehyde was added to the reactor, and the reaction was carried out at 180°C for 1.1 h. The reaction product was then transferred to a supercritical extraction tower, with the top temperature set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, and the mass ratio of extractant to reaction product (extractant-to-oil ratio) was 7:1. The raffinate containing dimers was then transferred to a flash tank to recover the extractant. At a temperature of 200℃ and a pressure of -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain isotropic pitch. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 315℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0058] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 386. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The asphalt contained 17.2 wt% aromatics, 2.4 wt% asphaltene, and 1.7 μg / g ash, as determined by four-component analysis. The resulting isotropic asphalt had a weight-average molecular weight of 983 and a softening point of 265℃. 13 C10-NMR analysis determined the methylene carbon content (C10) in asphalt. CH2 The carbon fiber obtained by adding 13.4 wt% has a tensile strength of 1.7 GPa and a tensile modulus of 67 GPa.

[0059] Example 4

[0060] 2 kg of catalytic cracking slurry was weighed and pumped into a reactor using a pipeline pump. 100 g of paraformaldehyde was added to the reactor, and the reaction was carried out at 180°C for 1.1 h. The reaction product was then transferred to a supercritical extraction tower, with the top temperature set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, and the mass ratio of extractant to reaction product (extractant-to-oil ratio) was 7:1. The raffinate containing dimers was then transferred to a flash tank to recover the extractant. At a temperature of 200℃ and a pressure of -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain isotropic pitch. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 305℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0061] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 391. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The asphalt contained 15.2 wt% aromatics, 3.4 wt% asphaltene, and 3.7 μg / g ash, as determined by four-component analysis. The resulting isotropic asphalt had a weight-average molecular weight of 963 and a softening point of 255℃. 13 C10-NMR analysis determined the methylene carbon content (C10) in asphalt. CH2 The carbon fiber obtained by adding 15.4 wt% has a tensile strength of 1.55 GPa and a tensile modulus of 56 GPa.

[0062] Example 5

[0063] 2 kg of ethylene tar was weighed and pumped into a reactor using a pipeline pump. 100 g of paraformaldehyde was added to the reactor, and the reaction was carried out at 180°C for 1.1 h. The reaction product was then transferred to a supercritical extraction tower, with the top temperature set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, and the mass ratio of extractant to reaction product (extractant-to-oil ratio) was 7:1. The raffinate containing dimers was then transferred to a flash evaporator to recover the extractant. The flash evaporation temperature was set at... At a temperature of 200℃ and a pressure of -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain isotropic pitch. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 312℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0064] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 367. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The asphalt contained 16.2 wt% aromatics, 2.1 wt% asphaltene, and 1.1 μg / g ash, as determined by four-component analysis. The resulting isotropic asphalt had a weight-average molecular weight of 917 and a softening point of 262℃. 13 C10-NMR analysis determined the methylene carbon content (C10) in asphalt. CH2 The carbon fiber obtained by adding 14.4 wt% has a tensile strength of 1.67 GPa and a tensile modulus of 62 GPa.

[0065] Example 6

[0066] 2 kg of vacuum residue was weighed and pumped into a reactor using a pipeline pump. 100 g of paraformaldehyde was added to the reactor, and the reaction was carried out at 180°C for 1.1 h. The reaction product was then transferred to a supercritical extraction tower, with the top temperature set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, and the mass ratio of extractant to reaction product (extractant-to-oil ratio) was 7:1. The raffinate containing dimers was then transferred to a flash tank to recover the extractant. The flash temperature was set... At a temperature of 200℃ and a pressure of -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain isotropic pitch. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 335℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0067] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 374. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The asphalt contained 15.7 wt% aromatics, 3.9 wt% asphaltene, and 2.7 μg / g ash, as determined by four-component analysis. The resulting isotropic asphalt had a weight-average molecular weight of 924 and a softening point of 281℃. 13 C10-NMR analysis determined the methylene carbon content (C10) in asphalt. CH2 The carbon fiber obtained by adding 15.4 wt% has a tensile strength of 1.57 GPa and a tensile modulus of 57 GPa.

[0068] Comparative Example 1

[0069] 2 kg of catalytic cracking slurry was weighed and pumped to a reactor using a pipeline pump. It was heated at 180°C for 1.1 h. The resulting reaction product was then pumped to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250°C, the second temperature zone at 310°C, and the third temperature zone at 370°C. The flow rate of the reaction product was controlled at 41 ml / min to obtain asphalt. Carbon fiber precursor was then melt-spun at 285°C under a nitrogen atmosphere. After pre-oxidation treatment at 275°C under an air atmosphere (50 ml / min), carbon fiber was obtained after carbonization treatment at 1100°C under a nitrogen atmosphere (100 ml / min).

[0070] Tests revealed that the obtained asphalt had a weight-average molecular weight of 669 and a softening point of 215℃. 13 C10-NMR analysis revealed that the asphalt contained methylene carbon (C10-NMR). CH2 The carbon fiber obtained by adding 1.1 wt% has a tensile strength of 0.28 GPa and a tensile modulus of 15 GPa.

[0071] Comparative Example 2

[0072] 2 kg of catalytic cracking slurry was weighed and pumped to a reactor using a pipeline pump. It was heated at 180°C for 1.1 h. The resulting reaction product was then pumped to a supercritical extraction tower using a pipeline metering pump. The tower top temperature was set at 425°C, the middle temperature at 381°C, and the bottom temperature at 330°C. The extraction pressure was 2.2 MPa. A mixed solvent of toluene, furfural, and chloroform (mass ratio 1:1:4) was used as the extractant, with an extractant-to-product mass ratio (extractant-to-oil ratio) of 7:1. The raffinate was then transferred to a flash evaporator to recover the extractant. The flash evaporation temperature was set at 20°C. At 0℃ and -30KPa, the enriched dimer was transported to a fluidized bed tubular reactor using a pipeline metering pump. The first temperature zone was set at 250℃, the second temperature zone at 310℃, and the third temperature zone at 370℃. The flow rate of the dimer was controlled at 41ml / min to obtain asphalt. Then, carbon fiber precursor was obtained by melt spinning in a nitrogen atmosphere at 295℃. After pre-oxidation treatment in an air atmosphere (50ml / min) at 275℃, carbon fiber was obtained after carbonization treatment in a nitrogen atmosphere (100ml / min) at 1100℃.

[0073] Tests revealed that the weight-average molecular weight of the dimers enriched after supercritical extraction was 331. 13 C10-NMR analysis determined the methylene carbon content (C10) in the dimer. CH2 The asphalt contained 3.2 wt% aromatics, 18 wt% asphaltene, and 9 μg / g ash, as determined by four-component analysis. The weight-average molecular weight of the obtained asphalt was 916, and its softening point was 231℃. 13 C10-NMR analysis revealed the methylene carbon content in asphalt (C10-NMR). CH2 The carbon fiber obtained by adding 2.1 wt% has a tensile strength of 0.3 GPa and a tensile modulus of 18 GPa.

[0074] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A continuous preparation method for isotropic bitumen, characterized in that, Includes the following steps: (1) Using aromatic heavy oil as raw material and polyaldehyde oxygen-containing polymer as co-carbonizing agent, the reaction parameters are adjusted to prepare low condensation products with different molecular weights through co-carbonization reaction. (2) Using supercritical / subcritical extraction technology, extractants with different solubility parameters are selected to extract the low condensation product prepared in step (1), and the extraction parameters are adjusted to obtain raffinate containing dimers with a molecular weight of 330-450. (3) The extract prepared in step (2) is distilled to recover the extractant, and the resulting dimer is thermally polycondensed in a fluidized bed tubular reactor. Combined with the flow control of the dimer, linear polycyclic aromatic hydrocarbon macromolecules with a molecular weight of 820-1130 and a softening point of 250-290℃ are prepared to obtain isotropic asphalt.

2. The continuous preparation method of isotropic asphalt according to claim 1, characterized in that, In step (1), the aromatic-rich heavy oil is one or more of the following: catalytic cracking slurry oil, ethylene tar, atmospheric residue, vacuum residue, high-temperature coal tar, and bamboo tar. And / or, the co-carbonizing agent is one or more of trioxymethylene, pentaoxymethylene, and polyacetaldehyde; And / or, the amount of the co-carbonizing agent is 3wt%-10wt% of the mass of the aromatic-rich heavy oil.

3. The continuous preparation method of isotropic asphalt according to claim 1, characterized in that, In step (1), the reaction temperature of the co-carbonization is 160-200℃, the reaction time is 0.5-1.5h, and the molecular weight range of the low condensation product is 100-550.

4. The continuous preparation method of isotropic asphalt according to claim 1, characterized in that, In step (2), the equipment used in the supercritical / subcritical extraction process is a supercritical extraction tower with a top temperature of 400-430℃, a middle temperature of 370-390℃, a bottom temperature of 310-370℃, and an extraction pressure of 1.6-3.2MPa. The extractant is one or more of toluene, N-methylpyrrolidone, chloroform, carbon tetrachloride, furfural, and tetrahydrofuran, and the mass ratio of extractant to low condensation product is 5:1-9:

1.

5. The continuous preparation method of isotropic asphalt according to claim 4, characterized in that, The extractant and the low-condensation product are mixed in a countercurrent manner; And / or, the extractant is a mixed solvent of toluene, furfural and chloroform in a mass ratio of 1:1:4; And / or, the temperature at the top of the column is 425°C, the temperature in the middle of the column is 381°C, the temperature at the bottom of the column is 330°C, and the extraction pressure is 2.2 MPa.

6. The continuous preparation method of isotropic asphalt according to claim 1, characterized in that, In step (3), the distillation temperature is 160-210℃ and the pressure is -20KPa to -40KPa; And / or, the fluidized bed tubular reactor is divided into three temperature zones: the first temperature zone has a processing temperature of 220-270℃, the second temperature zone has a processing temperature of 300-340℃, and the third temperature zone has a processing temperature of 350-380℃. And / or, the flow rate of the dimer is 20-50 ml / min.

7. The continuous preparation method of isotropic asphalt according to claim 1, characterized in that, In step (3), the dimer contains ≥15wt% methylene carbon, ≥75wt% aromatics, ≤4wt% asphaltenes, and ≤5μg / g ash. And / or, the methylene carbon content in the isotropic bitumen is ≥11wt%.

8. Isotropic asphalt prepared by the continuous preparation method according to any one of claims 1-7.

9. The application of the isotropic pitch according to claim 8 in the preparation of carbon fibers.

10. The application of the isotropic pitch according to claim 9 in the preparation of carbon fibers, characterized in that, Carbon fibers are obtained by melting and spinning isotropic pitch, followed by pre-oxidation and carbonization.

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