Preparation Of Mesophase Pitch Research Articles

Preparation of Mesophase Pitch with Fine-Flow Texture from Ethylene Tar/Naphthalene by Catalytic Synthesis for High-Thermal-Conductivity Carbon Fibers.

Mesophase pitch is usually prepared by radical polymerization or catalytic polymerization from coal tar, petroleum, and aromatic compounds, and the catalytic synthesis of mesophase pitch from pure aromatic compounds is more controllable in the preparation of high-quality mesophase pitch. However, the corrosive and highly toxic nature of the catalyst has limited the further development of this method. In this study, mesophase pitch was synthetized using ethylene tar and naphthalene as raw materials and boron trifluoride diethyl etherate as a catalyst. The effect of the catalytic reaction on the structure and properties of the mesophase pitch was investigated. The results show that naphthalene plays an important role in the mesophase content and reaction pressure (from above 6 MPa to 2.35 MPa). Mesophase pitch with fine-flow texture can be prepared by introducing more methylene groups, naphthenic structures, and aliphatic hydrocarbons during synthesis. Carbon fibers prepared from mesophase pitch show a split structure, and the thermal conductivity is 730 W/(m·K). This work provides theoretical support for lower toxicity and causticity and for reaction-controlled technology for the synthesis of high-purity mesophase pitch.

Preparation of Mesophase Pitch through Supercritical Fluid Extraction of Coal Tar Pitch.

This paper explores the preparation of mesophase pitch by employing supercritical fluid extraction on coal tar pitch sourced from a coal chemical company. The raw material undergoes pretreatment using various extraction solvents, and the resulting refined components are thermally polycondensed in a laboratory microreactor to create mesophase pitch. Qualitative and quantitative analyses of the mesophase pitch's structure are conducted through polarized light microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and other analytical methods to identify an optimal supercritical fluid extraction pretreatment solvent for coal tar pitch. The results reveal that using n-hexane solvent in the supercritical fluid extraction process yields a mesophase pitch with a remarkable mesophase content of 90.07%, displaying excellent optical texture distribution, superior directional arrangement and order, the closest lamellar accumulation, and the highest degree of anisotropy and graphitization.

The effect of boron trifluoride complex on the preparation of mesophase pitch from FCC decant oil fractions with different compositions and molecular structures

The boron trifluoride complex catalyst can effectively facilitate the development of anisotropic structures in FCC decant oil (FCC-DO) through cationic polymerization reaction. However, the fractions of FCC-DO with different boiling points possess different molecular compositions and aromatic nuclei configurations. In this study, FCC-DO is separated into light fraction, middle fraction, and heavy fraction by vacuum distillation. The different carbonization reaction pathways and reactivity were systematically investigated for three narrow fractions with no or 5 wt% addition of boron trifluoride complex catalyst. The results show that the heavy fraction is dominated by 4 and 5 plus ring aromatics with short side chains and methylene-bridged bonds. The catalyst showed excellent catalytic activity for the heavy fraction, the resulting product (MP-HF-5) possessing a softening point of 307 °C and 3.06 wt% methylene-bridged hydrogen at 95.3 wt% mesophase content. However, the catalyst slightly facilitated the development of anisotropic structures in the middle fraction (rich in 3 and 4 rings aromatics with naphthenic structures), which provided mesogen molecules during the FCC-DO carbonization reaction. Finally, the 1 ∼ 3 ring aromatics with long alkyl side chains are mainly present in the light fractions. The catalyst did not show obvious catalytic activity for the light fraction, in contrast, the oxygen-containing functional groups in the catalyst reacted with the aromatic molecule to form a disordered oxidative cross-linked structure, resulting in an almost completely isotropic structure of MP-LF-5.

Hydrogenation of coal tar pitch for improved mesophase pitch molecular orientation and carbon fiber processing

The high softening point and mosaic optical textures of coal tar pitch (CTP)-derived mesophase pitches are the main factors limiting their application in high performance carbon fibers. Spinnable mesophase pitch was prepared using CTP hydrogenation process, and the effect of hydrogenation process on the preparation of mesophase pitch and the crystal structure of carbon fibers was investigated. Molecular structure characterization results show that the naphthenic structures and the aliphatic groups in hydrogenated CTP were generated by the hydrogen addition reaction of aromatic rings and the subsequent naphthenic cracking reactions, respectively. The naphthenic structures and aliphatic groups introduced during the CTP hydrogenation process of CTP have a significant effect on improving the homogeneity of anisotropic textures, molecular weight distributions and the molecular stacking heights of mesophase pitches. The prepared mesophase pitch has lower viscosity and enhanced flowability, significantly improving its spinning stability and the molecular orientation of their as-spun pitch fibers. Benefits from this, the optimized carbon fibers present distorted graphite lamellar structures and possess a larger crystal size than commercial coal tar-based carbon fibers K13D2U. The work provides some valuable insights for enhancing crystal structures of carbon fibers via molecular structure regulations of their precursors.

Preparation of mesophase pitch with domain textures by molecular regulation of ethylene tar pitch for boosting the performance of its carbon materials

The fast formation of mosaic optical textures is one of main factors limited its application in high performance carbon materials due to active components containing olefins in ethylene tar pitch (ETP). In this paper, a thermal pretreatment process is proposed for effective molecular reformation of ETP, especially for separation of these active components containing olefins. Mesophase pitch with developed rheological properties and domain anisotropic textures was then prepared via polymerization of the post-treated ETP. Molecular structures analysis results show that these active components containing olefins in ETP prefer to form macromolecules consisted of multiple aromatic cores via rapid radical reactions, and develop a mixed anisotropic texture consequently. Nevertheless, these normal aromatic components tend to produce a semi-rigid molecular structure with less aromatic cores by aliphatic chains transfer reactions and stable radical polymerization reactions. This architecture facilitates its molecular stacking and orientation thus the prepared mesophase pitch (ETP-MP) shows better anisotropic domain texture. The prepared mesophase pitch had suitable performance for the application in needle cokes and carbon foams. This work will help to expand the manufacturing of ETP-derived carbon materials through molecular reformation.

Research progress in the preparation of mesophase pitch from fluid catalytic cracking slurry.

For the preparation of high-performance pitch-based carbon fibers and other carbon materials, mesophase pitch serves as a high-quality precursor. Since FCC (Fluid Catalytic Cracking) oil slurry is abundant in aromatic hydrocarbons and saturated hydrocarbons (about 95% in total), it has become an ideal choice for developing new carbon material products. This paper details the research progress of preparing mesophase asphalt with FCC oil slurry as a raw material from perspectives including the preparation method of synthesizing mesophase asphalt from FCC oil slurry, the impact factors of the formation process of mesophase asphalt and the industrial application of mesophase asphalt.

OBTAINING MESOPHASE PITCHES FROM COAL TAR

This article presents the results of research on mesophase pitch production from coal tar. The preparation of mesophase pitch was carried out by heat treatment in an argon atmosphere at temperatures of 300, 350, and 400 °C. The resulting carbon pitches were analyzed by scanning electron microscopy, Raman spectroscopy, and energy-dispersive analysis. An increase in the degree of surface degradation and the number of mesophase centers per unit area was observed with an increase in the treatment temperature to 300 °C. At 350 °C, a transition from an isotropic to an anisotropic structure was observed, where the mesophase centers were about 2 μm in size. A similar anisotropic structure was observed for a sample of coal tar obtained at 400 °C, and in some areas, a layered structure was observed, which could be associated with an increase in the graphitization degree of the samples. The particle size of the mesophase increases to 3.5-5 microns. The results of energy dispersive analysis showed that an increase in temperature leads to a decrease in the sulfur content. At 400 °C, sulfur is completely removed from the coal tar pitch composition. A correlation between the heat treatment temperature and the structure of the obtained pitch was established.

Effects of the addition of coal tar pitch-based mesocarbon microbeads on the preparation of mesophase pitch

Mesophase pitch was prepared by co-carbonization of the hydrocracking tail oil (HCTO) and coal tar pitch-based mesocarbon microbeads (MCMB). The effects of the addition amount of coal tar-based MCMBs on the C/H atomic ratio, softening point, carbon residue, optical texture, aromatic lamellae stacking order degree, and chemical reaction kinetics of mesophase pitch were investigated. The results show that MCMB can be used as a nucleating agent to accelerate the nucleation of mesophase spheres and reduce the energy barriers for the formation of the anisotropic phase. However, excessive MCMB greatly increases the viscosity of the pitch matrix and weakens the mobility of condensed aromatic macromolecules, leading to the formation of mesophase pitch with a mosaic structure and poor lamellar orientation. When the addition amount of MCMB is 5 wt%, the mesophase pitch with a large domain texture, high aromatic lamellar stacking order degree, and low softening point can be formed. This work provides a pathway to efficiently prepare mesophase pitch without catalyst removal.

Spinnable Mesophase Pitch Prepared via Co-carbonization of Fluid Catalytic Cracking Decant Oil and Synthetic Naphthalene Pitch

Using, as starting materials, fluid catalytic cracking decant oil (FDO), rich in short-chain alkyl groups, and synthetic naphthalene pitch (NP), with stable naphthenic structures, the synthesis of a spinnable mesophase pitch via a co-carbonization process was investigated. The effects of NP addition and the precursor molecular structure on properties of the resultant mesophase pitches and their carbon fiber derivatives were also discussed. With the increase of NP inclusion from 10wt% to 30wt%, the solubility in Toluene and Quinoline and the optically anisotropic domain size of the synthesized pitches increase. However, the softening points of the resultant mesophase pitches decrease. In comparison with FDO, more naphthenic structures are retained in NP and these show higher thermal stability during the preparation of mesophase pitch. The interaction of naphthenic structures in NP and short-chain alkyl groups in FDO promotes an increase in the molecular weight of the mesophase pitch prepared via co-carbonization and, in the present case, also increases the orientation and domain size in the resulting mesophase liquid crystal. The synthesized mesophase possesses low softening point, good solubility and 100 vol% mesophase content. Carbon fibers prepared from the co-carbonized mesophase pitch exhibit higher thermal conductivity than that of K-1100.

Effects of the addition of conductive graphene on the preparation of mesophase from refined coal tar pitch

Refined coal tar pitch (RCTP) and conductive graphene were used as raw materials to prepare the mesophase pitch (MP) by pyrolysis and the forming mechanism of MP was also inferred. Polarizing microscope, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and chemical kinetic analysis were used to characterize and analyze the effects of conductive graphene addition on the preparation of MP. The results show that conductive graphene can significantly affect the anisotropic structural development of MP due to promoting the formation of mesophase spheres as a nucleating agent at the initial stage of the reaction. However, the excess conductive graphene hinders the coalescence of the mesophase spheres and the formation of the wide-area streamline mesophase in the later stage of the reaction. When the conductive graphene content is 0.01 wt%, the wide-area streamline MP can form. With the increase of conductive graphene content, the numbers of mesophase spheres gradually increase, and their sizes gradually reduce. This study is of great significance for the preparation of cheap and low-ash MP.

Preparation of mesophase pitch from refined coal tar pitch using naphthalene-based mesophase pitch as nucleating agent

By adding naphthalene-based mesophase pitch (NBMP) into refined coal tar pitch (RCTP), pyrolysis products were obtained by dry-blending and co-carbonization method. The properties of pyrolysis products were characterized by polarizing microscope, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and Raman spectroscopy. The result shows the NBMP can obviously change the mesophase development of RCTP because it can promote the formation of mesophase spheres during the pyrolysis process. The carbon yield and aromaticity of pyrolysis products were increased with the increase of NBMP content. The anisotropic texture was wide-area structure when the NBMP content was 5 wt%. However, when the content of the additive is increased to 10 wt%, pyrolysis products will appear coking. The main role of this additive is to accelerate the reaction rate as the “nucleating agent” of the thermal condensation reaction.

Preparation of Mesophase Pitch from Petroleum Pitch

Preparation of Mesophase Pitch from Petroleum Pitch

Preparation of mesophase pitch from coliquefaction residue under pressure

ABSTRACTLarge wide-area mesophase pitch (MP) could be prepared by thermal polymerization method from asphaltene (AP) extracted from coliquefaction residue. The influences of temperature, soaking time, and initial gauge pressure on MP formation were investigated. The results indicate that initial gauge pressure has a strong impact on MP formation except for temperature and time. Increasing initial gauge pressure appropriately promotes the coalescence and rearrangement of mesophase microspheres, but too high pressure hinders microspheres to coalesce. The optimum formation condition of large wide-area MP with lower softening point (~270°C) is determined by the temperature at about 400°C, initial gauge pressure at about 1 MPa, and a soaking time of about 10 h. Based on SEM result, mesophase microspheres present a globe structure, they grow and coalesce obeying the mechanism of homogeneous nucleation.

Study on the Preparation of Mesophase Pitch from Modified Naphthenic Vacuum Residue by Direct Thermal Treatment

Two feedstocks (LPA and HPA) obtained from modification of naphthenic vacuum residues were selected to prepare mesophase pitch by direct thermal treatment. The influence of reaction temperature, soaking time, reaction pressure, and molecular structures of the feedstock on mesophase development was systematically investigated by analyzing variations in carbonization yield, carbon residue, quinoline insolubles (QI) content, density, optical textures, crystal structure, and surface morphology of derived products. It is found that the mesophase development and the properties of resultant mesophase products were closely related to the molecular structure of the original materials and preparation conditions. Compared with LPA, HPA was the preferable feedstock for thermal treatment because of its high degree of aromaticity and a large proportion of naphthenic carbon, and the resultant product obtained under the optimum conditions showed large flow domain mesophase, fewer alkyl side chains, and a high degree of m...

Investigation on Preparation of Mesophase Pitch by the Cocarbonization of Naphthenic Pitch and Polystyrene

Two modified pitches with softening points of 70 °C (LPA) and 110 °C (HPA) produced from modification of naphthenic vacuum residue were cocarbonized with polystyrene (PS), respectively, and the mesophase pitches were obtained. The effects of reaction time, PS addition, pressure, and properties of raw materials on cocarbonization behavior were analyzed by H/C, quinoline insoluble content (QI), carbon residue value, density, polarized optical images, X-ray diffraction pattern (XRD), scanning electron microscopy (SEM) analysis, Fourier transform infrared (FTIR) spectra, and 1H nuclear magnetic resonance (1H NMR) analysis. Comparing with HPA, the cocarbonization process showed more suitable for LPA to prepare the mesophase pitch due to the favorable occurrence of radical chain transfer reactions between LPA and PS components which contributed to the existence of aliphatic side-chains and naphthenic structures in mesogens as well as the formation of a well-developed mesophase pitch. Mesophase pitch with larger...

Preparation of mesophase pitch by aromatics-rich distillate of naphthenic vacuum gas oil.

Two aromatics-rich distillates R1 and R2 with different properties from naphthenic base vacuum gas oil were used for preparing mesophase pitch through high-pressure thermal treatment. 1H-NMR, FT-IR and VPO were employed to characterize the structural parameters of the raw materials. The products’ optical texture and molecular structure were analyzed by polarized light optical microscopy, 1H-NMR, FT-IR and XRD. The effect of raw materials’ structure on the formation of mesophase pitch was discussed. The results showed that the structure of the raw material had an important effect on the formation of mesophase pitch. The raw material R2 with higher aromaticity, more naphthenic structure and less alkyl side chains was easy to form mesophase pitch with large-domains optical texture, lower softening point and more ordered crystal structure.

Preparation of Mesophase Pitch from Coal Tar Pitch for C/C Composites

Mesophase pitch (MPP) has a high carbon yield and excellent graphitizability, compared with commercial coal tar pitch (CTP), which make it suitable for the preparation of C/C composites. In this paper, two MPP were prepared by heat-treatment of two coal tar pitches (CTP and modified coal tar pitch (MCTP)) in the presence of nitrogen. Elemental analysis and FTIR were used to monitor the change of chemical structures of MPP transition from CTP and MCTP. The pyrolysis behaviors of CTP and MCTP were studied by means of thermal analysis (TG and DSC). The morphologies of MPP were inspected by optical microscope. The structures of the MPP were characterized by XRD. The results show that there are more alkyl functional groups existing in CTP and MCTP than in MPP, and MPP has a higher C/H ratio than CTP and MCTP, which indicate MPP formation predominantly polycondense aromatic and release the alkyl functional groups. An endothermic band due to volatilize light compounds around 290 °C, two exothermic peaks at 430°C and 490 °C were characteristic of polymerization reactions, exothermic peaks of MCTP are higher than that of CTP because the former has a higher reaction active for its more alkyl side chain. The optical texture of MPP from CTP is mosaics texture, while from the MCTP is flow domains texture. (002), (101) peaks of graphite occur on XRD patterns, the peaks of MPP from MCTP are higher and narrower than MPP from CTP, which indicates the former is more graphitizability than the latter.

Effects of pressurized pretreatment on the preparation of mesophase pitch

Spinnable mesophase pitch as a precursor of high-performance carbon fiber was prepared from coal-tar pitch by using two-stage heat treatment, which consisted of pretreatment under pressure as a first stage and successive heat treatment under normal pressure as a second stage. Employing two different types of pressure reactor, a tube bomb and a laboratory autoclave, the effect of the pressurizing system was compared. The pretreatment under pressure of raw pitch was very effective in increasing the yield of mesophase pitch and developing its texture. The structural modification of the pitch induced by the pretreatment is discussed in terms of the chemical reactions of the pitch components.

Preparation of mesophase pitch from aromatic hydrocarbons by the aid of [formula omitted

Two procedures to prepare mesophase pitch from naphthalene using HF BF 3 , are described. The first procedure heats naphthalene at 80°C with HF BF 3 to give a naphthene rich pitch followed by either (a) heat treatment at 400–480°C under vacuum (0.1 kPa) or (b) Heat treatment at 2.1 MPa followed by vacuum treatment at 0.1 kPa. Approach (a) gives a spinnable mesophase pitch of S.P. 228°C of 98% anisotropy, 23 wt% yield, and approach (b) of 40–60 wt% yield. Stabilization in air was very slow especially with the pitch made by approach (b), taking 90–120 min or longer at 300°C. Programmed heating was effective to reduce the stabilization time. The second procedure heated naphthalene with HF BF 3 , under pressure at 260–300°C. The resultant pitches had 100% anisotropy and S.P. of 215–285°C with BS amounts of 52-12 wt% in yields of up to 60 wt%. Smoothly spun fibers were stabilized, 15–30 min at 270°C. Noncatalytic preparation produced mesophase pitch of high aromaticity: catalytic preparations maintained naphthenic hydrogen, the cause of stabilization reactivity. HF BF 3 could be removed from the pitch.