Mesophase Content Research Articles

Optimization of the Carbonization Process for the Preparation of High-Grade Needle Coke Based on the Response Surface Method and Microstructure Analysis.

Refined coal tar pitch (RCTP) with a quinoline insoluble (QI) content less than 0.01% was obtained from Wuhai coal tar pitch (CTP), which was used as a raw material to prepare needle coke by carbonization and calcination experiments. In this work, the effects of carbonization time, carbonization temperature, and carbonization pressure on the optical structure of green coke and the microstructure of needle coke were investigated. Meanwhile, the microstructure changes of products were characterized by polarizing microscopy, XRD analysis, Raman analysis, and SEM. The reliable transfer functions between the green coke mesophase content and the investigated factors, as well as the graphitization degree of needle coke, were established based on the response surface analysis method. Furthermore, we provide an operable window for carbonization temperature, time, and pressure, guaranteeing that the content of the green coke mesophase is greater than 90% and the graphitization degree of needle coke is greater than 80%. It can be found that the carbonization temperature has the most significant effect on the mesophase content and graphitization degree of coke. Prolongation of carbonization time is helpful for mesophase molecules to fully grow up, and the directional arrangement, which results in the structure of the coke, is regular. The appropriate carbonization pressure not only ensures that the carbonization reaction system has a certain viscosity but also provides hydrogen free radicals, which is conducive to the formation of drainage optical structure.

Increasing softening point of isotropic spinnable asphalt by two-step preparation from ethylene tar residue modified with bio tar residue

Carbon fiber prepared from asphalt may be a critical type of low-weight chemical material of excellent mechanical performances. Here, an isotropic spinnable asphalt (EBA) was prepared from ethylene tar residue (ETR) by a two-step method of bio tar residue (BTR) through co-polymerization-air blowing, and isotropic asphalt carbon fibers were prepared from the product asphalt. The main types of molecules contained in the two feedstocks were determined by 1H NMR and LDI-TOF MS analyses. The co-polymerization behavior and thermal stability of the asphalt blends were analyzed using polarized light microscopy and thermogravimetric analyzer, respectively. Finally, the morphology and mechanical properties of carbon fibers made from EBA were evaluated by scanning electron microscope and universal testing machine. The results show that BTR contains much more oxygen-containing functional groups and unique long-chain sawtooth molecular structure; the former can promote the reactivity of the co-polymerization reaction, and the latter can limit the formation of large-plane cyclic aromatic hydrocarbon polymers due to the spatial resistance effect to greatly reduce the content of the mesophase. The softening point of the product asphalt shows a tendency of increasing and then decreasing with the increase of the proportion of BTR in the raw material mixture, and a reaction mechanism based on linear and bulky molecules is proposed to explain it by analogy with the structure of macromolecules. Consequently, the EBA made from a mixture of ETR and BTR at ideal moderate proportions has excellent performance in terms of softening point and mesophase content than ETRO made from ETR alone, and the carbon fiber made has a high tensile strength of 1.82 GPa with an elastic modulus of 38.9 GPa, which has reached the level of high tensile strength carbon fiber. Therefore, the use of inexpensive renewable energy bio-asphalt in the modification of heavy oil to obtain high softening point isotropic asphalt for preparing isotropic carbon fiber with excellent properties is achievable.

Effect of isopropyl chloride addition in AlCl3 catalytic system on the formation of coal tar pitch-based mesophases

Mesophase pitch is a high-quality precursor for the synthesis of high-performance pitch-based carbon fibers. The mesophase content, texture and softening point are the most important factors for the structure, properties and spinnability of mesophase pitch (MP). Herein, we report a novel approach for the preparation of mesophase pitch with high anisotropic content and low softening point by AlCl3 catalytic pyrolysis in the presence of isopropyl chloride (PrCl). The variation of anisotropic content and mesophase texture under different PrCl additions and the effect of the introduction of isopropyl on the molecular stacking of aromatic lamellar molecules were investigated. The results confirmed that, except for their role in improving catalytic activity, carbocation co-catalysts can improve the structure and molecular assembly of aromatic molecules through the introduction of alkyl groups. The reaction of isopropyl chloride (PrCl) as a co-catalyst catalyzed pyrolysis of medium-temperature coal pitch at 370 ℃ for 8 h produced a bulk mesophase with a content close to 100 %. Compared to the AlCl3 system (without PrCl), the AlCl3-PrCl system can catalyze the preparation of mesophases at lower temperatures. In addition, it is logical that the introduction of isopropyl group significantly increases the stacking spacing of the mesophase pitch layer molecules, which can effectively improve the mobility of the aromatic layer molecules resulting in the growth of mesophase. The fusion texture and anisotropic content of mesophase pitch were significantly improved by replacing the nucleophilic reagent of the AlCl3-catalyzed system. This work provides feasible ideas for the preparation of high-performance coal tar based mesophase pitch.

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.

Pyrolytic Modification of Heavy Coal Tar by Multi-Polymer Blending: Preparation of Ordered Carbonaceous Mesophase.

In order to achieve the high-value utilization of heavy tar for the production of enhanced-performance graphite foam carbon, the carbon mesophase was ready from the heavy component of low-temperature coal tar, and the coal tar was modified by styrene-butadiene-styrene (SBS), polyethylene (PE) and ethylene-vinyl-acetate (EVA) copolymers. The order degree of the carbonite mesophase was analyzed using a polarizing microscope test, Fourier transform infrared spectroscopy and X-ray diffraction to screen out the most suitable copolymer type and addition amount. Furthermore, the mechanism of modification by this copolymer was analyzed. The results showed that adding SBS, PE and EVA to coal tar would affect the order of carbonaceous mesophase; however, at an addition rate of 10.0 wt.%, the linear-structure SBS copolymer with a styrene/butadiene ratio (S/B) of 30/70 exhibited the optimal degree of ordering in the carbonaceous mesophase. Its foam carbon prepared by polymer modification is the only one that forms a graphitized structure, with d002 of 0.3430 nm, and the maximum values of Lc and La are 3.54 nm and 2.22 nm, respectively. This is because, under elevated pressure and high-temperature conditions, SBS underwent chain scission, releasing a more significant number of methyl and other free radicals that interacted with the coal tar constituents. As a result, it reduced the affinity density of heavy coal tar molecules, enhanced fluidity, promoted the stacking of condensed aromatic hydrocarbons and increased the content of soluble carbonaceous mesophase, ultimately leading to a more favorable alignment of the carbonaceous mesophase.

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.

Phase transition behavior and mesophase aging phenomenon during liquid-state carbonization of FCC decant oil

The FCC decant oil (FCC-DO), primarily comprising 2- to 5-ring aromatic hydrocarbons with short alkyl side-chains, is widely acknowledged as the optimal precursor for the production of spinnable mesophase pitch, thus achieving its high-value utilization. The preparation of spinnable mesophase pitch from FCC-DO faces the challenge associated with achieving both high mesophase content and low softening point. To address this challenge, the phase separation behavior of the isotropic matrix and the aging phenomenon of coexisting anisotropic phases are examined using high-temperature centrifugation and advanced analytical techniques. The phase transition behavior of isotropic matrix can be described by a multi-stage continuous self-assembly induced by polymerized reactions. And this dynamic assembly process is tightly related to “steric hinderance effect” and “solvent dispersion effect”, which are mainly affected by the configuration and size distribution of formed mesogens respectively. Meanwhile, the formed anisotropic phase gradually undergoes two-staged time-dependent aging behavior, leading to poor compatibility of sub-fractions and then deterioration of melt fluidity. The initial aging of the mesophase is characterized by an almost unchanged molecular weight distribution, but a transformation of molecular configuration from a semi-rigid skeleton to a rigid one. This transformation is caused by intramolecular condensation resulting from the removal of the α-CH3 shielded by adjacent aromatic rings and dehydrogenation of naphthenic rings. When the previously-formed anisotropic phase under the liquid-state carbonized conditions for a long time, the second-stage aging of mesophase is readily triggered through the elimination of the α-CH3 not shielded by adjacent aromatic rings. This gives rise to the intermolecular polymerization and a shift towards higher molecular weight. This study provides insights into the preparation of excellent melt-fluidity mesophase pitch by promoting the rapid transformation of the isotropic matrix before significant aging of the coexisting anisotropic phase.

Correlation between properties of coal-based mesophase pitch with sea-island texture prepared by hydrogenation and graphite fibers

Refined coal tar pitch (RCTP) without pre-hydrogenation modification usually needs thermal sedimentation or centrifugation to obtain 100% coal-based mesophase pitch (CMP) after thermal polycondensation. This process is intricate and results in a low utilization rate of the overall pyrolysis products. Here, the sea-island texture CMP with mesophase content of more than 80% was directly prepared from RCTP by the co-carbonization method. Then, the practicality of this CMP was verified by the preparation of graphite fibers with high calculated thermal conductivity (1191W⋅m-1⋅K-1). The characterization results showed that 5 wt% tetrahydronaphthalene (THN) played the role of increasing the reactivity of pitch molecules, reducing the viscosity of the reaction system, increasing the mobility, and maintaining the molecules' planeness to a certain extent. Such effects were beneficial to the evolution of non-mesophase to mesophase molecules and its uniform dispersion in the mesophase, resulting in sea-island textures CMP with high anisotropy content. During the spinning process, the mesophase and non-mesophase molecules were oriented together, and they were further condensed to form larger carbon layers to obtain high thermal conductivity during high-temperature treatment. Therefore, this study is of great significance for the effective utilization of CMP and the preparation of high-value carbon materials.

Effect of two-stage thermal treatment on the reduction of quinoline-insoluble in Mesophase pitch

ABSTRACT Mesophase pitch (MP) is an important carbon material precursor with excellent physical performance and has a wide application in new energy utilization field. However, the current preparation process leads to a high quinoline-insoluble (QI) content in the MP, limiting its application. Here, we use two-stage thermal treatment to slow the degree of polycondensation during the formation of the MP. The two-stage thermal treatment can facilitate the formation of MP and limit the generation of QI. Moreover, the low content of polycyclic aromatic hydrocarbons (PAHs) in the liquid by-products indicates that the degree of thermal cracking of the feedstock becomes milder. The high content of cycloparaffins in gaseous by-products is due to the better polycondensation of the feedstock. Therefore, a wide area streamlined MP is prepared, which has a high mesophase content (96.8%), a low QI content (20.6%) and a good crystal structure (L c = 57.37 Å, N = 17.64, n = 99.53). At last, a possible mechanism of MP sample formation is discussed, which will provide an insight in the optimization of MP preparation process.

Effect of secondary gas-phase reactions (SGR) in pyrolysis of carbon feedstocks for anisotropic carbon materials production – 3: Modifying non-coking coal tar through co-pyrolysis of coal with linear low-density polyethylene and high-impact polystyrene

This work focuses on co-pyrolysis experiments of Utah Sufco coal with linear low-density polyethylene (LLDPE) and high-impact polystyrene (HIPS). These two plastic types have differing pyrolysis chemistries and have different hydrogen transfer behavior. Similar to earlier work in this series of papers, controlled secondary gas-phase reactions during pyrolysis were used to induce cracking and condensation reactions among the pyrolytic tar species. Co-pyrolysis tests were performed with feed plastic percentages ranging from 10 to 20 wt % and pyrolysis SGR temperatures ranging from 800 to 900° C. Analyses of the intermediate tar products showed that oxygen contents and aromaticity were substantially different, depending on the plastic, and resulting pitch softening points and mesophase contents also varied greatly depending on the starting plastic feedstock used. Most of the synergies observed in the co-pyrolysis results were negative, except for the oxygen content. Oxygen contents were higher than expected when LLDPE was used, resulting in reactive pitches with softening points >350° C. On the other hand, oxygen contents were lower than expected when HIPS was used, resulting in less reactive pitches. Ultimately, only the HIPS/coal samples created at the SGR temperature of 900° C had reasonable softening points at or under 350° C, making them the only samples created in this work potentially suitable for mesophase pitch-based carbon fiber production. The success in creating fusible mesophase pitches from co-pyrolyzing HIPS with Utah Sufco coal is likely attributed to the fact that polystyrene is a stronger hydrogen acceptor rather than donor, which should facilitate more cracking rather than stabilizing tar oxygen functional groups, making the tar species ultimately less reactive during thermal conversion to mesophase pitch.

Preparation and characterization of high performance coal tar pitch-based carbon fiber

High performance carbon fiber based on coal tar pitch is a new type of functional material with unique properties, such as light weight, high strength, high modulus, high thermal conductivity, high electrical conductivity and low thermal expansion coefficient. It is a new type of functional material for both military and civilian use. In order to study the preparation of high performance carbon fiber based on coal tar pitch, this article obtained high performance carbon fiber based on coal tar pitch through raw material pretreatment, spinnable asphalt modulation, asphalt melt spinning, non-melting, carbonization, graphitization and other processes, and characterized the performance of spinnable mesocase asphalt and carbon fiber. The results show that high-performance spinnable mesophase pitch can be prepared by three steps raw material refining, hydrogenation modification and thermal polymerization. The mesophase content is 95%, the softening point is 280 °C, and the 3000 m filament can be spun under melt spinning conditions of 375 °C and 0.01 MPa. After graphitization, the coal pitch-based carbon fiber has excellent mechanical properties, small structural defects and a diameter of 12 μm. The tensile strength is 3089 MPa, the elastic modulus is 689 GPa, and the thermal conductivity is 902 w/(m·K).

Influence of resin on the formation and development of mesophase in fluid catalytic cracking (FCC) slurry oil

Resin is one of the key components of fluid catalytic cracking slurry oil which is the raw material to form high-quality mesophase pitch. The effect of resin variations on the formation of mesophase was investigated in this paper. The results showed when the resin addition was from 0 to 20 wt%, the formation rate of mesophase remained basically invariable, but it was beneficial to the development of mesophase pitch with higher order degree. However, excessive additions of resin (>20 wt%) sharply accelerated the formation of mesophase due to the high concentration of reactive sites in the system, which shortened the time to form pitch with mesophase content close to 100%, adversely it led to the generation of mesophase pitch with lower order degree. In addition, the approximate molecular structure model of resin was constructed by various characterization methods. The aromatic ring skeleton of resin was dominated by 3–4 ring aromatic hydrocarbons. Resin also possessed structural features such as higher aromaticity, higher N and S content, larger molecular size, longer branched chains, more cyclic alkane structures and methylene bridges, and higher concentration of reactive sites than FCC-exR. Furthermore, an explanation of the effect of resin on the formation and development of mesophase with respect to the molecular structure characteristics was presumed. This work has important implications for regulating the raw material properties of FCC slurry oil and the preparation of high-quality mesophase pitch.

Assessment of the structures contribution (crystalline and mesophases) and mechanical properties of polycaprolactone/pluronic blends

Films of biodegradable blends of polycaprolactone (PCL) and Pluronics F68 and F127 were manufactured by an industrial thermo-mechanical process to be applied as potential delivery systems. The effects of Pluronics on the structure (mesophase organization), and thermal and mechanical properties of polycaprolactone were investigated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), polarized optical microscopy (POM) and tensile mechanical tests. The addition of Pluronics affected the crystallization process by changing the relative amounts of crystalline, amorphous, and meso- (condis + plastic) phases. The melting transition and XRD profiles were deconvoluted to assess the individual contribution of the different crystal morphologies. Furthermore, it was found that the mechanical properties of the blends depended on the ratio and type of Pluronic. Thus, Pluronic F127 showed a larger mesophase content than its F68 counterpart with PCL and blends with enhanced ductility.

Optimization of Molecular Composition Distribution of Slurry Oil by Supercritical Fluid Extraction to Improve the Structure and Performance of Mesophase Pitch

The composition distribution of slurry oil has a significant impact on the structure and performance of the mesophase. In this study, supercritical fluid extraction oil (SFEO) and extraction components were extracted from two slurry oils (SLOs) using the supercritical fluid extraction (SFE) technique. The fundamental properties and composition distribution of two SLOs and associated SFEOs were thoroughly investigated. Electron microscopy and spectroscopic techniques were employed to study the morphology and structures of mesophase pitch produced by carbonizing SLOs and their extraction components under the same conditions. The findings revealed that, compared to SLO–LH, SLO–SH has a higher proportion of 4–5 aromatic rings and a narrower hydrocarbon distribution range. In SLO–LH, O1, N1, and N1O1 molecules with long side chains and poor flatness make up the majority of the heterocyclic aromatic hydrocarbons. The distribution of CH compounds can be narrowed by using supercritical fluid extraction to efficiently separate various heteroatom-containing compounds with a higher condensation degree. After supercritical extraction, the mesophase content, texture distribution, and graphitization degree of the mesophase were improved. Polycyclic aromatic hydrocarbons with high planarity help polymer macromolecules stick together and build up in an orderly way. Heterocyclic aromatic hydrocarbons with high condensation and low planarity, on the other hand, play an important role in the formation of mosaic structures.

Effective preparation of mesophase by segmented hydrogenation/thermal polycondensation of coal liquefied pitch

Mesophase pitches were prepared by segmental hydrogenation/thermal condensation using Shenhua coal liquefaction residue refined pitch (CLP) as raw material, and the effects of tetralin (THN) addition (5 ∼ 15 wt%) and hydrogenation temperature (350 ∼ 450 °C) on the structure and properties of the resulting products were investigated. The results showed that the H/C atomic ratio of the hydrogenated pitch (HP-12.5%) reached 0.64 at the temperature of 400 °C and THN addition of 12.5 %, and the content of the generated mesophase reached 76.0 % after heat treatment, which increased by 33.5 % compared with the mesophase content without hydrogenation. And the optical texture of the mesophase was improved from mosaic type to coarse fiber type and coarse flake type. The structures of the hydrogenated pitches were characterized by 1H NMR and FT-IR, which showed that the addition of THN increased the alkyl groups of the hydrogenated pitch molecules and resulted in more α- structures. The X-ray diffraction results showed a better orientation arrangement of pitch aromatic planar molecules due to enhanced fluidity of pitches caused by the increased alkyl structure after the addition of THN.

Effect of Mesophase particles on the Electrographite carbon brush tribology behavior under no-load condition

Electrographite (EG) has partial electrical conductivity and is used as a current collector in direct current motors. EG is prepared from a suitable carbon source through a multi-step process to convert it to conductive carbon. In this work, EG was prepared with coal tar pitch (CTP) having different mesophase (MP) content (4, 8, 19, and 33%) and their characteristics were compared. The microstructural analysis of CTP indicated that increase in MP leads to increase in mesophase particle size. MP was found to have a significant impact on the physical and binding properties of CTP. X-ray diffraction studies showed EG to be a partially graphitized material with a degree of graphitization (DOG) ranging from 30% to 60%. Since coke-based materials graphitize more easily than lamp black, the DOG, crystal size, and d-spacing of coke-based material were higher. Graphitization in tube furnaces was better than induction and Acheson furnaces because of its concentrated heat in small size susceptor. The Design of Experiments (DOE) method with Face Centre Factorials was used to generate 14 different combinations of load (20 N,60 N, and 100 N) and velocity (1 m s−1, 3 m s−1, and 5 m s−1) for wear and COF analysis which were done on pin on disc apparatus. Response surface method (RSM) was used to investigate the relationship between wear, COF, and MP content. The CTP binder properties had a significant impact on wear. The COF decreased as the number of Brooks and Taylor structure MP particles increased. On the EG wear characteristics, adhesive wear was a more dominant factor than abrasive wear.

Reversible mesophase in stress-annealed poly(3-hydroxybutyrate) fibers: A synchrotron x-ray and polarized ATR-FTIR study

Structural changes in poly(3-hydroxybutyrate) (P3HB) monofilaments (diameter ~90 μm), induced by annealing under tensile stress (1 h with 1.6–40 MPa loading at 80–130 °C) have been investigated with synchrotron wide-angle x-ray diffraction (WAXD) and polarized attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Melt-spun P3HB fibers consist of an amorphous phase, a crystalline α-phase and a mesophase. Specific IR bands in s-polarized (electric field vector along the fiber axis) spectra have been identified to arise from the mesophase. For fibers annealed at low stress (1.6 MPa), the mesophase content practically disappears but can be recovered with tensile drawing. In-situ WAXD and polarized ATR-FTIR studies, performed during cyclic tensile loading/unloading, have revealed that the mesophase formation/dissolution is highly reversible in fibers annealed at low stress. This reversibility behavior, and the lack of off-axis reflections in WAXD patterns, support the theory that the mesophase is made of conformationally disordered and stretched chains, which are mainly located in-between α-crystals.

Investigation of the Dependence of the Softening Temperature on the Content of Mesophase in Petroleum Pitches Obtained from Heavy Pyrolysis Resin and Decant Oil

Investigation of the Dependence of the Softening Temperature on the Content of Mesophase in Petroleum Pitches Obtained from Heavy Pyrolysis Resin and Decant Oil

Исследование зависимости температуры размягчения от содержания мезофазы в нефтяных пеках, полученных из тяжелой пиролизной смолы и декантойля

Samples of petroleum pitches were obtained from heavy pyrolysis resin and decantoil (heavy gas-oil of catalytic cracking) by thermal polycondensation at atmospheric pressure, temperatures of 380–400 and 410–440°С (for resin and decantoil, respectively) and isothermal holding time of 30–480 min. Analysis of the dependence of the softening point on the mesophase content for the obtained samples showed that at the same mesophase content, decantoil pitches exhibit a lower softening point compared to pyrolysis resin pitches, for which, even at 30 % mesophase, the softening point approaches 300°C. This suggests that it is impossible to obtain pitch from pyrolysis resin with high mesophase content without preliminary preparation (for example, by hydrogenation). On the other hand, it has been shown that for pitches from decantoil, it is possible to isolate the mesophase up to 65% or more with a softening point not higher than 250°C.

Acceleration of petroleum based mesophase pitch formation by PET (polyethylene terephthalate) additive

To improve mesophase formation in petroleum-based pitch, the PET (polyethylene terephthalate) additive reaction was studied. PFO (pyrolysis fuel oil) was used to prepare the petroleum pitch, and PET was added at a weight ratio of 0.33–1.50%. The chemical structure of PET-added pitch was analyzed by Fourier transform infrared spectroscopy, and the thermal properties were characterized by thermogravimetric analysis and the softening point method. Added PET provides oxygen during the pitch synthesis reaction, and the polycondensation of the pitch was accelerated by oxygen crosslinking. Thus, the softening point and carbonization value increased with the amount of PET added; moreover, the mesophase content increased by more than three times with 0.33wt% PET addition. However, at more than 0.67wt% PET addition, the fluidity rapidly decreased, so the mesophase spheres decreased in size and were independently distributed.