Mesophase Spheres Research Articles

The Neglected Role of Asphaltene in the Synthesis of Mesophase Pitch.

This study investigates the synthesis of mesophase pitch using low-cost fluid catalytic cracking (FCC) slurry and waste fluid asphaltene (WFA) as raw materials through the co-carbonization method. The resulting mesophase pitch product and its formation mechanism were thoroughly analyzed. Various characterization techniques, including polarizing microscopy, softening point measurement, Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), were employed to characterize and analyze the properties and structure of the mesophase pitch. The experimental results demonstrate that the optimal optical texture of the mesophase product is achieved under specific reaction conditions, including a temperature of 420 °C, pressure of 1 MPa, reaction time of 6 h, and the addition of 2% asphaltene. It was observed that a small amount of asphaltene contributes to the formation of mesophase pitch spheres, facilitating the development of the mesophase. However, excessive content of asphaltene may cover the surface of the mesophase spheres, impeding the contact between them and consequently compromising the optical texture of the mesophase pitch product. Furthermore, the inclusion of asphaltene promotes polymerization reactions in the system, leading to an increase in the average molecular weight of the mesophase pitch. Notably, when the amount of asphaltene added is 2%, the mesophase pitch demonstrates the lowest ID/IG value, indicating superior molecular orientation and larger graphite-like microcrystals. Additionally, researchers found that at this asphaltene concentration, the mesophase pitch exhibits the highest degree of order, as evidenced by the maximum diffraction angle (2θ) and stacking height (Lc) values, and the minimum d002 value. Moreover, the addition of asphaltene enhances the yield and aromaticity of the mesophase pitch and significantly improves the thermal stability of the resulting product.

Changes in Functional Groups and Crystal Structure of Coal Tar Pitch with Respect to Carbonization Temperature

In this study, changes in the microstructure of coal-tar pitch (CTP) during successive processes, including pyrolysis, polycondensation, and crystallization, were examined in connection with the resulting variations in structure factors, as measured by X-ray diffraction (XRD) analysis, and functional groups, as confirmed by Fourier transform infrared (FTIR) spectroscopy. To this end, four zones were defined based on variations in crystallinity, which were indicated by d002 and Lc. Each zone was further characterized by interpreting crystallinity development in relation to changes in functional groups and specimen height. At around 400 °C, polycondensation occurred as the C-Har and C-Hal peaks decreased in intensity. These peak reductions coincided with the formation of mesophase spheres, resulting in enhanced crystallinity. Subsequently, at around 500 °C, the peak intensity of C-H and COOH decreased, which was attributed to the release of large amounts of gases. This led to sharp volume changes and a temporary reduction in crystallinity. All these results suggest that changes in the functional groups of CTP at lower temperatures (600 °C or less) during the carbonization process are closely associated with variations in its crystallinity. The major findings of the present study provide valuable insights for designing highly effective processes in the manufacturing of synthetic graphite blocks using CTP as a binder material, including by selecting appropriate temperature ranges to minimize volume expansion and crystallinity degradation and determining the lowest possible carbonization temperature to ensure adequate binder strength.

Functionalized graphene assisted the formation of mesocarbon microbeads with ultra-large size and loose microcrystalline structure from petroleum pitch for sodium-ion batteries anode

It is a significant way to improve the sodium storage performance of mesocarbon microbeads (MCMBs) by adjusting the size and microcrystalline structure of it. A petroleum-based MCMBs with an ultra-large size and loose microcrystalline structure was synthesized by introducing functionalized graphene (FNG). The results indicate that the FNG can hinder the ordered stacking of planar aromatic macromolecules, prevent the coalescence and prolong the growth time of mesophase spheres. Mesophase spheres are easier to grow to an ultra-large size with looser microcrystalline structure. The MCMBs with a size of 250 µm and a larger microcrystalline spacing can be achieved by adding 1.0 wt% FNG during the polycondensation process. Such MCMBs deliver a competitive specific capacity of 123.4 mAh g−1 at a current density of 1.0 A g−1 with a high initial coulombic efficiency of 81.79% and an excellent stability of cycle performance when applied as anode of SIBs. This work provides a valuable and efficient method to enhance the SIB performance by designing the size and microcrystalline structure of MCMBs.

Production of monodisperse spherical mesophase from coal tar pitch by solvent extraction

Production of monodisperse spherical mesophase from coal tar pitch by solvent extraction

Effects of olefinic compounds on the thermal transformation for FCC slurry oil: Evolution pattern and mechanism

FCC decant oil was always used as the raw material for the preparation of high-value-added carbonaceous materials. There is little disagreement that the free radical mechanism induces thermal polymerization reactions between reactant molecules and intermediate species, which leads to the formation of carbonaceous mesophase in the early stage of carbonization. Olefinic hydrocarbons were recently found to be widely distributed in FCC decant oil in our previous research, and these chemically active compounds usually possess weak π-bonds in molecules and thus potentially form free radicals easily, which may impact the carbonization performance dramatically. This research investigated the effects of olefinic compounds on the preparation of needle coke from FCC decant oil, as well as the corresponding mechanism in depth combined with the evolution pattern of the intermediate species during liquid carbonization. ESR analyses were adopted to evaluate the variation of the concentration of stable free radicals. Stable free radical concentration varied greatly in diverse polymerizing systems along with the carbonization process. Olefin showed a significant effect on the stable free radical concentration during carbonization. The stable free radical concentration of the polymerizing system derived from FCC decant oil was 3.32 × 1020 spins/g when the reaction time was 4 h. But with 3 wt% addition of 2-vinylnaphthalene and squalene in FCC decant oil, the stable free radical concentration increased to 2.14 × 1021 spins/g and 1.33 × 1021 spins/g, respectively, with the same reaction time. Meanwhile, the olefins conjugated with aromatic rings shown more obvious effect on the generation of free radicals. Olefinic compounds can lead to a high generation rate of free radicals and significantly high stable free radical concentration in the polymerizing system which then promote the formation of disordered carbon materials. Besides, plenty of fine particles appeared between mesophase spheres with the addition of olefinic hydrocarbons, and then impeded the coalescence between mesophase spheres. Effect mechanism for olefin on the development of carbonaceous mesophase was proposed accordingly. In sum, the content of olefinic compounds in raw materials should be limited for reaching the requirements of the synthesis of carbon materials with superior structures, in which the content of olefinic compounds should be less than 1 wt% at least based on the research in this paper.

Petrologic Characteristics and Chemical Structures of Macerals in a Suite of Thermally Altered Coals by Confocal Raman.

Thermally altered coals affect the safety and efficiency of coal mining and utilization, but most studies of thermally altered coal have only focused on the whole coal instead of on different macerals. Thermally altered coals have complex and special maceral components; not only intrinsic macerals but also newly formed macerals such as pyrolytic carbon can be observed. The shape and texture of intrinsic macerals also change significantly after thermal alteration, especially for vitrinite. Therefore, employing an in situ testing method to study the macerals in thermally altered coals is necessary. Herein, a confocal Raman imaging microscope was used. Results show that macerals become coked in samples adjacent to the sill, and circular mosaic texture is the most common texture observed in this series of samples. In samples away from the sill, inertinite is isotropic, while in samples closest to the sill, anisotropic inertinite can be found. The Raman spectra of inertinite and vitrinite (mosaic texture) are significantly different. For vitrinite, the D and G peaks are closer, and the height of D is lower than for inertinite. The Raman spectra of thermally altered coal include 13 bands after curve fitting. Curved-fitted results show that for vitrinite, polycondensation provides the nucleation of mesophase spheres, and newly formed aromatics take part in the growth of mesophase spheres. However, for inertinite, excessive amorphous carbon and substituents, such as aromatic alkyl and aryl–alkyl ether, form cross-linked structures and hinder the anisotropic development of inertinite.

Preparation of mesocarbon microbeads as anode material for lithium-ion battery by co‑carbonization of FCC decant oil and conductive carbon black

Low yield and unremarkable electrochemical performance of MCMB prepared from conventional thermal polymerization are inevitable, which limits its large-scale application as anode material for lithium-ion batteries. Hence, in this work, MCMBs were prepared by co‑carbonization of low-valued FCC decant oil and conductive carbon black (CCB). CCB can enhance the nucleation, inhibit the growth of the mesophase spheres and adhere on the surface of spheres, thereby increasing the yields (38.9 wt%), influencing the microstructure and subsequent electrochemical performance of MCMB. The MCMBs prepared by doping with 3 wt% CCB exhibited a small particle size (15.0 μm) and moderate structural disorder degree with wide interlayer spacing (AD3/Aall = 18.15%, d002 = 3.5342 Å), which shortened the transport pathway of Li+ inside the microbeads. Besides, chain-like conductive carbon black connected to the surface of the MCMBs, forming a continuous and developed conductive network, which was benefit for increasing of electron conduction and enhancing the Li+ transport rate outside the microbead. Such MCMB delivered the superior long-term cyclability with specific capacity of 394.5 mAh g−1 at 0.5 A g−1 (over 400 cycles) and presented a high-rate capability with reversible capacity of 276.0 mAh g−1 at an ultra-high current density of 3 A g−1.

Study on structures and properties of isotropic pitches and carbon fibers from co-carbonization of aromatic-rich distillate oil and polyethylene glycol

Obtaining cost-competitive carbon fibers with excellent mechanical properties remains a great challenge. Here we report the co-carbonization of polyethylene glycol (PEG) and an aromatic-rich distillate oil (HCT0-RF) to prepare isotropic pitches that have superior spinnability for the production of carbon fibers. Among all of the carbon fiber productions, H-P10-CFs exhibited the best tensile strength of 1050 MPa and elongation of 2.5 %, respectively, at the breaking point. We reason that the addition of PEG into HCTO-RF can effectively increase the yield of isotropic pitches, accompanied by restricting the appearance of the mesophase spheres. The amount of aliphatic carbon in spinnable pitches were observed to increase with the amount of PEG. Thus, the changes in molecular structure can improve the rheological properties of spinnable pitch and enhance the spinnability. In addition, the increase of aliphatic components can accelerate the oxidative reaction and promote the stabilization efficiency. Unfortunately, excessive aliphatic components would inevitably cause higher oxygen uptake content, which deteriorate the uniformity of the fiber structures during carbonization process. With the increase of PEG content, the tensile strength of these carbon fibers increased first and then decreased. The optimized PEG content should be in the range of 5–10 wt%. The PEG acted as the co-carbonization agent provides new perspective in the field of carbon fiber production.

Preparation of mesophase carbon microbeads from fluidized catalytic cracking residue oil: The effect of active structures on their coalescence

Mesophase carbon microbeads (MCMBs) were synthesized by thermal polycondensation with fluidized catalytic cracking residue oil (FRO) as the feedstock. The evolution features of functional groups of the residual oils and the residual solid products from thermal polymerization were analyzed, and the effect of olefinic compounds on the coalescence between mesophase spheres was investigated in depth. The results showed that the olefin contents of residual oil, heptane-soluble, and heptane-insoluble/toluene-soluble decreased simultaneously as the reaction proceeded while that of toluene-insoluble increased, indicating that the olefins in the solvent phase could not only provide molecule sources for the development of carbonaceous mesophase but also directly assemble into the insoluble mesogens. More importantly, the involvement of olefins caused a sharp increase of the system viscosity, making it difficult for the mesophase spheres to completely coalesce into regular large ones after cohering, leading to the apparent deformation. In contrast, catalytic hydrotreatment can saturate olefinic species and enhance the hydrogen transfer ability of FRO to further avoid the induction effect of olefins, slow down the mesophase development, reduce the system viscosity, and consequently avoid the deformation of mesophase spheres.

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.

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.

Modified effect on properties of mesophase pitch prepared from various two-stage thermotreatments of FCC decant oil

The comparative study of different two-stage heat treatments was conducted to illustrate the modified effects on improving yield and spinnability of mesophase pitch. In such two-stage thermotreatments, a pressured condensation is employed to involve low-molecular-weight species into the formation of mesogens, thereby increasing pitch yields. Subsequently, vacuum polymerization could contribute to rapid development of mesophase and then reduce the residence time. The results indicate that the short duration could decrease occurrence of the intramolecular aromatization and intermolecular polymerization reactions that are readily induced by elimination of α-methyl and dehyroaromatization of naphthenic rings during the later stage of heat treatment. Consequently, the formed semi-rigid molecules in QS sub-fraction (i.e., fusible component) are seldom transformed into rigid ones mainly constituting QI sub-fraction (i.e., infusible component). Ultimately, sufficient QS sub-fraction, with a higher average Mw and a large amount of short alkyl and naphthenic substituents, is more likely to completely dissolve QI sub-fraction. Thus, the resultant mesophase exhibits an excellent fusible deformability. Besides, the structural feature of semi-rigid oligomer could somewhat loosen molecular association of layered stacking and contribute to the slippage between stacked mesogens due to its steric effects, thereby decreasing the softening points of mesophase pitch. Above modified effects are easily implementable during a suitable process of two-stage thermotreatment, such as the processes of preparing MP-4-0.01-1.0, MP-4-0.005-1.0 and MP-3-0.01-2.0 in this study. It is worthwhile to mention that the vacuum treatment is required to be conducted prior to large-scale coalescence of mesophase spheres in order to obtain spinnable mesophase pitch.

Preparation of mesocarbon microbeads as anode material for lithium-ion battery by thermal polymerization of a distillate fraction from an FCC slurry oil after hydrofining with suspended catalyst

Slurry oil (SO) as the starting feedstock for the preparation of mesocarbon microbeads (MCMBs), an excellent carbonaceous anode material, is of significant commercial value and environmentally friendly. In this study, the MCMBs were prepared by thermal polymerization of SO after modification through suspended-bed hydrofining followed by distillation (SBHD). The results showed that SBHD is fully competent in saturating olefins and increasing naphthenes of SO simultaneously and thus bringing forth more naphthenic hydrocarbons and less olefins in SBHD-SO, which is indeed beneficial to the preparation of MCMBs with better morphology and more uniform size distribution. More interestingly, there was evident coalescence between MCMBs prepared from D-SO during the growth process due to the existence of abundant active groups on the MCMBs’ surfaces, whereas the MCMBs prepared from SBHD-SO grew via absorbing the mesogen molecules in the mother liquor and there was no obvious coalescence between mesophase spheres. Moreover, the anode performance showed that the MCMBs prepared from SBHD-SO can deliver the highest discharge specific capacity of 315 mAh/g at a current density of 500 mA/g and an excellent stability of cycle performance. Thereby, the MCMBs prepared from SBHD-SO best meet the application requirements. This study paves a new strategy for the efficient preparation of MCMBs by using SO, which may expand the application prospect of SO.

Pitch derived graphene oxides: Characterization and effect on pyrolysis and carbonization of coal tar pitch

In this work, the coal tar pitch (CTP) is modified by the pitch derived graphene oxide (pGO) prepared from the same CTP using ZnO template and in-situ KOH activation technique. The results indicate that the prepared pGO has the oxygen-containing functional groups with a high specific surface area up to 1937 m2/g. The mass ratio of ZnO to pitch is crucial to adjust the surface area of pGO. The pGO modified CTP have more condensed structures of pyrolysis products with increased structural regularity. This is also paralleled with enhanced microstructure development of mesophase spheres and their transforming into more orderly lamellar structure, due to the increased surface area and active role of the pGO additions. Such structure changes and reduced weight loss in pyrolysis and carbonization are beneficial for improving coke yield of CTP. The result reported is of great significance for exploring potential high value utilization of CTP.

Preparation and Electrochemical Performance of Spherical Mesophase Soft Carbon Materials Composite Anodes for Lithium-ion Batteries

Preparation and Electrochemical Performance of Spherical Mesophase Soft Carbon Materials Composite Anodes for Lithium-ion Batteries

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.

Effect of Different Catalysts on Properties of Coal Tar Pitch Modified by Cinnamaldehyde

Cinnamaldehyde- (CMA-) modified coal tar pitches (CTPs) are prepared in the presence of acids. In this paper, the effect of boric acid and p-toluene sulfonic acid on the pyrolysis and graphitization process of CMA-modified CTP was studied. The pyrolysis process was studied by Fourier transform infrared spectroscopy, thermogravimetric analysis and derivative thermogravimetry, and polarized-light microscopy. In addition, the graphitization process was studied by X-ray diffraction and Raman spectroscopy. The results indicate the carbon yield of CMA-modified CTP with boric acid as catalyst (B7C10) is higher than that of CMA-modified CTP with p-toluene sulfonic acid as a catalyst (P7C10). In addition, under the same experimental condition (heated at 400°C and held for 1 h), the mesophase spheres of B7C10 are more regular than those of P7C10 and the largest diameter of the mesophase spheres can reach to 40 um. Further, after the graphitization process, the graphitization degree of B7C10 is higher than that of P7C10. So, it is more effective to modify CTP with boric acid as a catalyst.

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 and characterization of mesophase formation of pyrolysis fuel oil-derived binder pitches for carbon composites

Petroleum-based mesophase binder pitches were prepared from pyrolyzed fuel oil (PFO) using heat treatment. The mesophase was fabricated by an additional heat treatment of PFO-based raw pitches. Therefore, during the formation of the mesophase, the generation of small spherical particles was confirmed with increasing reaction temperature, for temperatures under 400 °C. During heat treatment at temperatures above 400 °C, the small spherical mesophase structures coalesced to form mesophase structures in the bulk. In addition, with increasing heat treatment temperature and time, the softening point, the C/H ratio, and quinoline-insoluble (QI) material of the binder pitches increased significantly, confirming an increase in the mesophase content.

Occurrences and origin of reservoir solid bitumen in Sinian Dengying Formation dolomites of the Sichuan Basin, SW China

Reservoir solid bitumen is pervasive throughout the Sinian Dengying Formation dolomites of the Sichuan Basin and neighboring areas, yet its origin remains controversial. Optical and scanning electron microscope (SEM) studies of the Dengying Formation were carried out to elucidate the nature and origin of the solid bitumen. Solid bitumen in dissolution pores, intercrystal pores, and stylolites appears to have formed in association with regional hydrocarbon charging processes. Reservoir solid bitumen displays a variety of morphologies, each of which appears to reflect different precursor hydrocarbons. Massive/crust-like solid bitumen was probably derived from solid precursors whereas finger-like solid bitumen likely evolved from liquid precursors. Sheet-like and thin skinned globular solid bitumen appeared to have precipitated from wet gas precursors. Analyzed solid bitumen is characterized by high random reflectance (average = 3.4%) and bireflectance values (4.2–6.9%), exhibits strong optical anisotropy, and displays different coke structures, including granular mosaic, domain, and fibrous. The coke textures, which appear to reflect the nature of bitumen precursors, formed by physical coalescence of mesophase spheres and parallel arrangement of laminated aromatic sheets in association with a rapid heating event. The inferred thermal episode, which is evidenced by the presence of hydrothermal minerals, including saddle dolomite, quartz, authigenic illite, and barite, may have been associated with the Late Permian eruption of the Emeishan Traps. Thus, widespread solid bitumen in the Dengying Formation reflects the effects of hydrothermal alteration rather than the impact of normal burial-related thermal maturation. Further, the close association of sold bitumen and authigenic kaolinite indicates that natural deasphalting plays a role in the formation of reservoir solid bitumen.