FCC Decant Oil Research Articles

Production of needle cokes via mild condition co-pyrolysis of FCC-DO and PFPE

The conventional needle coke production process suffers from high reaction temperature and pressure, and therefore, alternative approaches for needle coke production with low energy consumption should be developed. The co-pyrolysis process of FCC decant oil (FCC-DO) and perfluoropolyether (PFPE) was suggested to prepare needle cokes under mild reaction conditions in this work. The characteristics of green pitches and cokes from the co-pyrolysis process were evaluated with XRD, FT-IR, TGA, EA and polarized images to prove the effectiveness of the PFPE-aided reaction in accelerating polymerization. The mixture of FCC-DO and 10 wt% of PFPE was heated to 420, 430, 440, and 450 °C and 1 bar in continuous nitrogen flow, and needle cokes could be successfully derived at a temperature of 440 °C and atmospheric pressure with the addition of PFPE, which are significantly milder conditions compared with prior studies on needle coke production. The reaction mechanism of co-pyrolysis was suggested with radical-based reactions that emerged during the thermal decomposition of PFPE. Furthermore, the electrical and thermal properties of the carbonized needle cokes indicated the superior structural, thermal, and chemical characteristics of PFPE-assisted reaction-derived needle cokes; the needle cokes obtained from PFPE co-pyrolysis showed a 23.5 % reduced CTE value and 7.2 times higher electrical conductivity compared with cokes from pure FCC-DO. Effective needle coke production at a low temperature and pressure could be achieved with a PFPE-assisted co-pyrolysis reaction, and we believe that this study could contribute to a novel method for preparing needle cokes with low energy consumption and extending the applicability of needle cokes by supplying high-quality and low-price needle cokes.

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.

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.

Influence of boron trifluoride complex addition on structure and composition of mesophase pitch from FCC decant oil via two-stage thermotreatment

In order to optimize the molecular structure and composition distribution of mesophase pitch, the two-stage thermotreatment process preparation using boron trifluoride ethyl valerate complex as catalyst was investigated. During the two-stage thermotreatment, the cationic polymerization initiated by catalytic polycondensation made carbonaceous microcrystalline molecules contain more semi-rigid structures, while parts of alkyl side chains and naphthenic structures were retained. Subsequently, the mesophase pitch was rapidly induced to form by removing non-mesogens and enriching sufficient concentrations of mesogens in the vacuum polycondensation stage. The results showed that the two-stage thermotreatment process could change the chemical structure of the aromatic nucleus and obtain a suitable softening point (283 °C) at 100% anisotropic content. The mesophase pitch with 5 wt% catalyst addition (MP-5) had high content of methylene structure (HF = 3.18 wt%), naphthenic structure (HN = 3.45 wt%) and fusible/soluble TI-PS sub-fraction (28.07 wt%). In addition, MP-5 also possessed high aromaticity (fa = 0.90) and stacking order (Lc = 37.48 Å, n = 11.70). Unfortunately, an increase in the oxygen-containing groups was accompanied when the catalyst content reached to 10 wt%, which disrupted the aromatic lamellae parallel stacking structure of the mesophase pitch due to steric hindrance, resulting in more isotropic structures in the product.

Effects of decompressing carbonization on the preparation of needle coke from FCC decant oil

More efficient treatments of FCC decant oil (FDO) were developed to convert this common by-product in refineries to high-value-added carbonaceous materials, such as needle coke. The performance of the produced needle coke was determined by the properties of raw materials and the carbonization process based on the theories of carbonaceous mesophase. The preparation of needle coke can generally be divided into two stages before calcination and graphitization: liquid carbonization and solidification stage. Pressure in both stages, especially the pressure in the solidification stage, showed great effects on the properties of the products. The microstructure of semi-coke can hardly be the preferred needle structure with carbonization without decompressing operation, although the raw material satisfies the preparation requirement of needle coke. A new method for evaluating the order degree of microstructure (ODM) of semi-cokes was developed, enabling semi-cokes with preferable axial orientation to be further efficiently distinguished. The ODM value can also be used as an index to evaluate whether a semi-coke can be used as a precursor for further preparation of high-quality needle coke. The evolution of product gases can provide external force to the orientation of mesophase into the preferred needle structure in the product. This improvement can be achieved through decompressing operations in the second stage of carbonization and optimized when the pressure is at 0.5 MPa.

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.

Carbonization of mesocarbon microbeads prepared from mesophase pitch with different anisotropic contents and their application in lithium-ion batteries

To clarify the relationship between the chemical compositions of green mesocarbon microbeads (GMCMBs) and the electrochemical behavior of carbonized mesocarbon microbeads (CMCMBs) for lithium-ion batteries, GMCMBs were prepared by emulsifying mesophase pitch (MP) with various anisotropic contents derived from FCC decant oil. Subsequently, GMCMBs were carbonized at 1000 °C, and their electrochemical behaviors were investigated. It was found that the GMCMB prepared from MP with a high anisotropic content (98 vol%) exhibited highly ordered aromatic lamellae stacking (ID/IG = 0.68) and a high condensation degree (IOS = 0.268). Therefore, CMCMB-98 with a highly ordered structure (ID/IG = 1.01) and low porosity (SBET = 80 m2/g) was formed, resulting in a high initial coumbic efficiency (74.8%). In addition, the GMCMB prepared from MP with a low anisotropic content (12 vol%) had more alkyl side chains and light components (ICHS = 0.50 TS = 22.7 wt%). CMCMB-12 with high porosity (SBET = 390.65 m2/g) and disorder degree (ID/IG = 1.21) was produced after the carbonization process, leading to a high capacity and rapid solid-state diffusion speed of Li+. Hence, CMCMB-12 can deliver the highest reversible capacity (405 mAh g−1 at 500 mA g−1 over 200 cycles) and excellent rate performance.

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.

The effect of accumulation of polycyclic aromatics in FCC decant oil on subsequent pyrolysis behaviors

To control the liquid-phase carbonization of the petroleum residue, the transition of the aromatics in earlier stages of the thermal conversion and its effect on subsequent carbonization behavior were analyzed. It was found that more monocyclic and dicyclic aromatics was converted to polycyclic aromatics in a comparatively shorter time between 450 and 500 °C. The higher polycyclic aromatics content of the oil accelerated the formation of the anisotropic phase, thus the excessive carbonization of the system was prevented and the lamellar orientation of the pyrolysis product was modified (the time required to obtain a fully developed carbonaceous mesophase decreased by 2 h and the stacking height (Lc) increased from 18.58 Å to 21.18 Å when the polycyclic aromatics content increased by 14.92 wt%). The modified oil obtained by thermal pretreatment (HCTO-RF-B) was converted to a carbonaceous mesophase with a large domain texture and good lamellar orientation (d002 = 3.4599 Å, Lc = 21.94 Å), as well as a low softening point (273 °C) in a short carbonization time (8 h), which is attributed to the higher polycyclic aromatics content (which accelerated the formation of an anisotropic phase) and fewer long side chains (which controlled an appropriate free radical concentration) of the thermal pretreated oil. The fully developed carbonaceous mesophase from HCTO-RF-B had a higher stabilization reactivity, which is attributed to the alkyl chains preserved in the system (C–H substitution indice (ICHS) = 0.7513, alkyl indice (IA) = 0.7690).

Investigation on the development and orientation of mesophase microstructure during the two-stage pyrolysis of FCC decant oil

The two-stage pyrolysis was proposed to effectively form uniaxially fibrous mesophase during pyrolysis of FCC decant oil. Detailed investigation focuses on main factors of regulating mesophase orientation and corresponding changes of mesogen stacks. The first-stage treatment under low temperature of 440 °C and high pressure of 2 MPa for 8 h ensures formation of bulk mesophase with well-coalesced texture and good molten fluidity; subsequently, fracture of residual alkyl side-chains together with devolatilization of trapped light molecules under high temperature (450–480 °C) and low pressure (0.2–1.0 MPa), mainly contributes to volatile evolution at solidification of two-stage pyrolysis. Thereby, the overlap between sufficient volatile evolution that provides enough shear force on mesophase and appropriate viscosity of bulk mesophase, high enough for maintenance of mesophase deformation but not too high to prevent penetration of gas bubbles, is readily achieved and then significantly promotes the transition from mesophase domain into acicular flow texture. Moreover, mesophase orientation at solidification is followed by transformation of mesogen stacks from columnar short-range order into nematic order, leading to decrease of stacked height and number of layer per stack. And further cracking and dehydroaromatization reactions at solidification of two-stage pyrolysis facilitate elimination of steric hindrance, relaxation of structural strains and heal of defects within the planar aromatic sheets, thus resulting into a more homogenous distribution of stacked mesogens and a smaller degree of disorder within the 2D mesogen lattice.

Hydroconversion kinetics of Marlim vacuum residue

A kinetic model was obtained for the Marlim crude vacuum residue (VR) hydroconversion. Marlim VR mixed with FCC decant oil in an 80%/20% weight basis was put in contact with a commercial NiMo on γ-alumina catalyst in a stirred batch reactor. Several temperatures and oil/catalyst ratios were used over different times (0–240 min), at a 110 bar pressure and constant hydrogen flow. The analysis of the collected product showed residua conversions of up to 70%. Hydroconversion kinetics involving thermal and catalytic cracking contributions was proposed to represent the obtained data. The resulting system of differential equations of the kinetic model was solved within reaction time, taking into account the experimental temperature profile. The chi-square objective function was minimized to adjust model parameters. A proposed effective hybrid minimization method was used, by applying a Newton-type method between certain simulated annealing minimization steps. The proposed kinetic model allowed the representation of thermal and catalytic cracking effects, in order to take into account different catalyst concentrations. Therefore it is possible to consider distinct reactor hydrodynamics, such as expanded or bubble column reactors.

Hydrotreating of FCC decant oil as a needle coke feedstock.

Two levels of hydro-desulfurizing experiments using FCC decant oil were performed with a conventional petroleum hydrorefining catalyst in order to obtain detailed information on hydro-desulfurizing of feed oil and coke derived from it. Hydro-desulfurizing products and the feed decant oil were analyzed by the HPLC-MS method, and the carbonization was carried out in a small batch reactor after which properties of coke produced were measured.There is no difference with sulfur condensation ratios in cokes formed from hydro- desulfurized and unhydro-desulfurized feedstocks. Low sulfur coke clearly can be produced from low sulfur feedstocks which have beenhydro-desulfurized. Coke coefficient of thermal expansion (CTE) decreases by feedstock hydro-desulfurizing, but coke CTE from the more severely hydro-desulfurized decant oil is higher than that from the mildly hydro-desulfurized decant oil. Under the severehydro-desulfurizing conditions, hydrogenation of aromatic rings occurs, as does naphthenic ring opening and dealkylation. Severehydro-desulfurizing also causes a decrease in hydrogen donor ability and an increase in the carbon number of alkyl side chain for one of compound classes.

Coke production from an FCC-decant oil: characterization of the thermal process

Detailed characterization of the thermal transformation of a decant oil, obtained from a fluid catalytic cracking (FCC), in a closed system makes it possible to determine the mode and timing of coke production. A fast dismutation process into light and heavy liquid products is observed, followed by slow production of coke with an activation energy of only 150 kJ mol −1. From elemental analysis, nuclear magnetic resonance (n.m.r.) and mass spectra, dehydrogenation and condensation reactions are detected. These results are well modelled by the pyrolysis of a set of 1-aryl, 2-phenylethylene compounds (aryl = two to four aromatic rings) under the same conditions. The phenanthrenic derivative presents a similar thermal profile towards coke production. The first steps are mainly dominated by non-radical processes such as electrocyclic reactions.

Study on Mechanism of Formation and Quality Improvement of Petroleum-based Needle Coke.

Needle coke which has been the best filler of graphite electrodes need to be upgraded because the quality of graphite electrodes for electric arc furnace is improved with progress of steel making technique.The role of respective feedstock based on mechanism of formation of needle coke is overviewed in terms of pretreatment of the feedstocks, such as modification of FCC decant oil (FCCDO), solvent deasphaltene process, and heat treatment of low sulfur vacuum residue (LSVR), to improve the characteristics of the needle coke.The mechanism of formation of needle coke is traced through the observation of the carbonization process using tube bomb which can provide nearly the same condition as delayed coker. Coefficient of thermal expansion (CTE), which is the most important property of needle coke, is strongly influenced by uni-axial orientation of flow texture in the coke. Gas evolution of solidification, therefore, is important for production of low CTE coke as well as formation of bulk mesophase. The carbonization condition, especially pressure and temperature, influences the above important factor. Furthermore, the cocarbonization of LSVR with FCCDO produced excellent needle coke of low CTE because formation of bulk mesophase and gas evolution at solidification were improved. As the amount of mosaic coke of high CTE affects the CTE of needle coke, in the present study, the modification of FCCDO and LSVR was studied to eliminate the formation of mosaic coke.Addition of high aromatic pitch, dewaxing and heat treatment were highly effective for elimination of mosaic coke by modification of FCCDO. On the other hand, elimination of asphaltene by solvent extraction and heat treatment with hydrogen donor were highly effective as modification of LSVR.

Characterization of meso-carbon microbeads prepared by emulsion method

This article describes the preparation of meso-carbon microbeads by the emulsion method from three kinds of bulk-mesophase pitches (coal-tar, FCC-decant oil, and naphtha-tar pitch), and their physicochemical properties. The meso-carbon microbeads were obtained as the spherical particles from respective pitches in yields of 65%–90%. The meso-carbon microbeads from the coal-tar and FCC-decant oil pitches had a larger amount of quinoline insolubles than those of starting pitches, while that from naphtha-tar pitch was approximately constant with heat treatment temperature. The coal-tar and FCC-decant oil based microbeads had an optically anisotropic texture with different domain sizes, whereas the naphtha-tar based microbeads exhibited an optically isotropic texture. The results of FTIR and ash content suggest that a permeation of silicone oil during heat treatment causes a distortion and expansion of the lamellar structure for the naphtha-tar based microbeads. Furthermore, it was found from FTIR and 13C-NMR analysis that the coal-tar based microbeads had the highest aromaticity and that the naphtha based microbeads had the largest amount of aliphatic carbons, such as methyl, methylene, and alicylic groups.

Cocarbonization properties of dewaxed FCC decant oils with low sulfur vacuum residue leading to production of needle coke.

Cocarbonization properties of a particular FCC decant oil (FCC-DO) of paraffinic nature with low sulfur vacuum residue (LSVR) were studied in an attempt to find guiding principles of its thermal modification for production of better quality needle coke, using a tube bomb, as these oils do not always make excellent coke of homogeneous quality because of difference existing in the oils properties. FCC-DO was heattreated under some conditions of temperature and residence time before cocarbonization with LSVR, to eliminate the unfavorable bottom mosaic coke. The heattreatment of FCC-DO removed paraffins and alkyl groups of longer chains on aromatic ring, which increased the aromaticity. Highly aromatized FCC-DOs increased solvency, at early stage cocarbonization, dissolving viscous mesophase derived from the most reactive portion in LSVR which is believed to cause bottom mosaic structure. The coefficient of thermal expansion (CTE) of the coke was maintained at optimum range for graphite electrodes by selecting adequate carbonization conditions for the particular feed.

Carbonization in the tube bomb leading to needle coke: II. Mechanism of cocarbonization of a petroleum vacuum residue and a FCC-decant oil

Cocarbonization of a FCC decant oil (FCCDO) and a vacuum residue of low sulfur crude (LSVR) was studied at 460 and 480°C through the sequential microscopic observation and analyses of the carbonization intermediates produced in a tube bomb to discuss how the best needle coke was produced from their mixture of a particular ratio subjective to the carbonization temperature. The cocarbonization moderates the reactivity of LSVR to allow the formation of the mesophase of low viscosity comparable to that from FCCDO alone as indicated by the solubility change and allows at same time more evolution of gas at the solidification stage which may originate from LSVR. Thus, the better uni-axial arrangement of mesophase components is achieved in the cocarbonization, leading to the production of better needle coke. Such a cocarbonization is strongly influenced by the carbonization temperature, defining the best ratio of the mixing at the respective temperature because of the reactivity subjective to the temperature. The formation mechanism of the bottom mosaic coke is also discussed from a view of solubility of the reactive portion of the asphaltene in the cocarbonization matrix.

Carbonization in the tube bomb leading to needle coke: I. Cocarbonization of a petroleum vacuum residue and a FCC-decant oil into better needle coke

The cocarbonization of a Fluidized Catalytic Cracking decant oil (FCCDO) with a petroleum low sulfur vacuum residue (LSVR) was studied at a temperature range of 460 to 480°C by evaluating the qualities of coke lumps produced in a tube bomb in terms of their CTE and anisotropic development. The cocarbonization certainly improved the orientation of flow texture and CTE of the resultant coke, providing the smallest CTE as low as 0.10 × 10 −6/° C and 0.36 × 10 −6/° C at particular FCCDO/LSVR mixing ratios of 5 5 and 7 3 according to the respective carbonization temperatures of 460 and 480°C. The natures of bulk mesophase and gas evolution at the solidification stage for the axial-rearrangement of mesophase aromatic component, both of which essentially define the coke quality, are strongly influenced by the carbonization reactivities of blended feedstocks and carbonization conditions. FCCDO may moderate the carbonization progress of reactive LSVR and LSVR supply the sufficient gas evolution during the solidification, leading to excellent flow texture of axial arrangement. The formation of mosaic coke in the bottom part of the lump which may deteriolate the quality of the coke produced in a commercial coker appeared to be caused by the phase separation between the paraffin and asphaltene fractions. Such a separation at a early stage of the carbonization was found to be controlled by the blending and the carbonization conditions.

A two-stage preparation of mesophase pitch from the vacuum residue of FCC decant oil

The preparation of mesophase pitch as a precursor for the high-performance carbon fiber from a vacuum residue of FCC-decant oil (FCC-DOVR) was studied, applying a two-stage heat treatment to improve the pitch yield as well as its liquid crystal properties. The present two-stage preparation consisted of the pressurized heat treatment (1–5 MP) of the first stage at 430–480°C and the successive heat treatment under 13–260 Pa at 430°C. Such a two-stage preparation increased the yield of the spinnable mesophase pitch of 100% domain texture with lower softening point to 45% from 22% by the single-stage one from the same feedstock. Spinning properties of the mesophase pitch were excellent to allow smooth spinning for longer than 15 min and random orientation of mesogen molecules in the tranverse section of the fiber perpendicular to the fiber axis. The chemistry of the two-stage preparation for the higher yield and better properties as the fiber precursor is briefly discussed.