Ethylene Tar Pitch Research Articles

Modification mechanism of graphite anode in lithium-ion battery coated with ethylene tar pitch

Modification mechanism of graphite anode in lithium-ion battery coated with ethylene tar pitch

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.

Preparation and electrochemical performance of the N-doped hollow pitch-based activated carbon fibers as supercapacitor electrodes

Mixtures of polyethyleneimine (PEI) and ethylene tar pitch (0, 15, 20, 30 wt% of PEI) were melt-spun, stabilized, carbonized and activated to prepare nitrogen-doped (N-doped) activated carbon fibers (ACFs). The morphology, porous structure and surface chemistry of the N-doped ACFs were characterized by N2 adsorption, XPS and SEM. Their electrochemical performance as supercapacitor electrode materials was investigated. Results indicate that the specific surface area, pore volume and number of nitrogen-containing functional groups of the N-doped ACFs are much increased compared to undoped ACFs. PEI pyrolysis during the carbonization of the fibers leads to the formation of hollow N-doped ACFs that increases the utilization% of the surface area, resulting in a significant increase of the specific capacitance. When 20 wt% PEI was added, the specific surface area of the N-doped ACF reached 2 756 m2/g, its pore sizes ranged from 0.7 to 2 nm, and its specific capacitance reached 314 F/g at 0.5 A/g, which is much higher than that (194 F/g) of the undoped ACF.

Preparation of General Purpose Carbon Fibers by the Two-Step Method from Ethylene Tar Pitch

In this paper, besides the single method of air blowing and thermal condensation, a new two-step combining method was taken to modulate the pitch precursor for carbon fibers: the ethylene tar pitch was first air-blown under 280 °C for 10 h, and then thermal-condensed in nitrogen under 380 °C. Then group composition, elemental and thermal analysis, FT-IR, SEM and polarized optical micrographs were used in this paper, and the influence of different methods of modulation on the performance of pitches was discussed. The results revealed that neither in the method of air blowing nor thermal treatment can the pitch with a high softening point and coking value but no mesophase be produced. However, isotropic spinnable pitch with high softening point (286 °C), coking value (80.2%) and superior thermal stabilities can be synthesized in the two-step combining method. Carbon fibers from such pitches had been produced through melt-spinning, stabilization and carbonization, they showed uniform diameters (about 15.5 μm) with smooth and homogeneous surfaces. After stabilization and carbonization, the shrinkage of carbon fibers’ diameter was limited to 6%.

Eutectic effect during mesophase formation in co-carbonization of ethylene tar pitch and polystyrene

Ethylene tar pitch was co-carbonized with waste polystyrene to prepare mesophase pitch. The characteristics of mesophase pitches were examined using polarized light optical microscopy, apparent viscometry, Fourier transform infrared spectrometry, 1H nuclear magnetic resonance spectrometry, and X-ray diffractometry. The properties of the mesophase pitch were greatly improved because of the eutectic effect. The soluble content increased from 5% to 56%, the mesophase itself increased from 32% to 100%, and the optical texture was changed from a coarse mosaic into a flow domain after the waste polystyrene was added to the ethylene tar pitch. The apparent viscosity showed that the mesophase pitch changed from thixotropic to Newtonian suggesting improved rheological behavior during co-carbonization. The increased number of alkyl groups, which are mainly methylene groups, altered the molecular structure of the mesophase pitch in a way that resulted in the eutectic effect.

Needle coke formation derived from co-carbonization of ethylene tar pitch and polystyrene

Ethylene tar pitch was co-carbonized with waste polystyrene to prepare needle coke. The modified properties of mesophase, which were greatly improved due to increasing naphthenic and other alkyl content, availed the formation of needle coke with high quality. The coefficient of thermal expansion value was decreased from 3.2 × 10 −6/°C to 0.3 × 10 −6/°C and the optical texture of the coke was changed from coarse mosaic texture to flow domain of high uniaxial orientation after adding waste polystyrene into ethylene tar pitch. The low viscosity of the mesophase pitches favored the development of mesophase and highly uniaxial arrangement. The increase in alkyl group content greatly improved characteristics of the needle coke.

Removal of SO2 over ethylene tar pitch and cellulose based activated carbon fibers

The activities of activated carbon fibers (ACFs) from ethylene tar pitch and cellulose with various surface areas were examined for the oxidative conversion of SO2 into aq.H2SO4 in the presence of H2O and O2, and compared to those of coal tar pitch and polyacrylonitrile based ACFs. Cellulose ACF with surface area of ∼1000 m2/g after calcination at 1000°C in N2 showed the highest activity among the ACFs of similar surface area. The higher activity of cellulose ACF appeared to be obtained through the larger amount of CO evolution during the calcination. The SO2 adsorption was enhanced while H2O adsorption was inhibited over the ACFs by the calcination regardless of the sources of ACFs. Activities of fibers decreased significantly with increasing adsorption temperature.

A study of the carbonization of ethylene tar pitch and needle coke formation

Carbonization of ethylene tar pitch (ETP) and its hydrogenated products was studied in a tube bomb to find the appropriate carbonization conditions for producing a good needle coke. At the relatively low temperature of 460 °C under a pressure of 784 kPa for 10 h, ETP produced lump coke of low CTE and of excellent flow texture without any mosaic coke being formed at the bottom of the reactor (bottom mosaic coke). A higher carbonization temperature (480 °C) gave a mosaic texture coke of large CTE, although the carbonization was complete in 6 h. A lower carbonization temperature (440 °C) or pressures above 784 kPa resulted in bottom mosaic coke. The catalytic hydrogenation of ETP improved the anisotropic texture of coke carbonization at 480 °C, but could not eliminate the mosaic coke forming at the reactor bottom. N.m.r. and g.p.c. analysis revealed that ETP contained some olefins and high molecular weight substances in the major 2–3 ring aromatic hydrocarbons. The roles of such minor components in the formation of needle and mosaic cokes are discussed.

Co-carbonization of ethylene tar pitch and coal tar pitch to form needle coke

The co-carbonization of ethylene tar pitch (ETP) and coal tar pitch (CTP) was studied in a tube bomb. A small amount of CTP was found to effectively modify the carbonization properties of ETP to produce excellent needle coke of low nitrogen content without formation of mosaic coke at the reactor bottom (bottom mosaic coke) in a wide range of carbonization temperatures and pressures. Blending 30–50 wt% CTP into ETP provided lump coke of thin lamellar flow texture, with a good CTE value and nitrogen content after calcination at 1000 °C. The influences of carbonization temperature and pressure on the nitrogen remaining in the coke were also investigated.

Carbonization of hydrogenated ethylene tar pitch; study of the pitch molecular compactness factor and coke optical texture

Compactness factors of aromatic molecules in hydrogenated ethylene tar pitch were calculated as a parameter to relate to properties of mesophase of the carbonization system. Compactness factors, φ, derived from structural analyses of hydrogenated ethylene tar pitch were also related to the size and shape of optical textures of resultant cokes. Hydrogenated ethylene tar pitches having values of φ 〉 0.5 gave cokes with flow type anisotropy and relate to formation of peri-condensed structures. The spin-lattice relaxation times, T 1, for the cokes derived from hydrogenated ethylene tar pitch, are related to their optical texture.

Reflux modification of ethylene tar pitch into mesophase pitch precursor using less aluminium chloride

Reflux modification of ethylene tar pitch into mesophase pitch precursor using less aluminium chloride

Preparation and properties of carbonaceous mesophase-II highly soluble mesophase from ethylene tar modified using aluminum chloride as a catalyst

A carbonaceous anisotropic mesophase, highly soluble in THF and quinoline, was prepared from ethylene tar pitch (ETP) modified using aluminum chloride as a catalyst. A mesophase pitch prepared at 360°C under vigorous nitrogen flow and stirring from ETP modified with 10 wt% of AlCl 3 at 250°C for 7 hr exhibited solubility of 80 wt% in quinoline at 90 vol% of anisotropic content, its solubilities in THF and pyridine being as high as 52 and 62 wt%, respectively. Such a high solubility of the mesophase pitch is ascribed to the naphthenic groups of its component molecules which are produced during the modifying reaction catalyzed by AlCl 3. The moderate molecular size of modified ETP is another advantage. The anisotropic mesophase of high solubility and low melting temperature is transformable into a flow domain texture by annealing. Easy spinning into highly oriented fibers is expected.

Relation between X-ray Parameters of Semi-cokes and Magneto Resistance Anisotropy Factors of Graphite from Hydrogenated Ethylene Tar Pitch

Relation between X-ray Parameters of Semi-cokes and Magneto Resistance Anisotropy Factors of Graphite from Hydrogenated Ethylene Tar Pitch

Graphitization behavior of hydrogenated ethylene tar pitch

The graphitization behavior of cokes prepared from ethylene tar pitch (ETP) hydrogenated at temperatures from 473 to 673 K has been studied by magnetoresistance measurements at liquid nitrogen temperature and by scanning electron microscopy. Graphitization heat treatment of the cokes was carried out at 3273 K. Hydrogenation temperatures of 473 and 523 K resulted in graphitized cokes with random layer plane textures and low degrees of graphitization. Hydrogenation at higher temperatures was effective in promoting development of flow-type textures during graphitization. The coke from ETP hydrogenated at 673 K showed the highest graphitizability, preferred orientation and flow-type texture developed by heat treatment.

Binderless moulding of green cokes delivered from solvent refined coal and ethylene tar pitch

Green cokes, derived from the co-carbonization of Solvent Refined Coals with ethylene tar pitch, have been moulded into discs without using a binder. Cokes with a range of size of optical texture have been prepared by control of the ratios of the two components of the carbonization blend. The appearance of the discs was assessed by optical and scanning microscopy after calcination to 1200° C. The most acceptable disc was prepared by moulding carbon of a heat treatment temperature (HTT) of 440° C. With cokes of HTT 440° C, dimished cohesion of the coke grains prevented the development of a strong disc on calcination. It is considered that the presence of benzene-soluble (BS) and benzene-insoluble/quinoline-soluble (BI/QS) fractions in the pitch systems contribute to cohesion of coke particles having a HTT of 440° C.

Carbonization behavior of hydrogenated ethylene tar pitch

Carbonization behavior of ethylene tar pitch has been studied with respect to mesophase formation by means of modification of the chemical composition of the starting materials. The hydrogen treatment of ethylene tar pitch has been carried out over the temperature range from 473 to 673 K under a pressure of 10 MPa without catalyst. Then, the hydrogenated ethylene tar pitches were carbonized at 723 K and the optical texture of the resultant cokes were assesed by optical microscopy. It was revealed that the carbonization of the ethylene tar pitch hydrogenated at 673 K gives a coke of optical texture with enlarged flow-domain. The hydrogen-transfer ability of the ethylene tar pitches during the temperature range of mesophase formation was estimated by the method of 9,10 dihydroanthracene (DHA) formation through co-carbonization of the pitch with anthracene. It was recognized that the larger the amount of conversion of DHA, the better is the development of optical texture.

Study of carbonaceous mesophase through the e.s.r. spectra of vanadyl chelates

The behaviour of vanadyl chelate complexes in Iranian heavy oil and ethylene tar pitch during the carbonization process has been investigated by the e.s.r. technique to obtain information on the mesophase transformation. Activation energies for rotation of chelates incorporated with aromatic lamellae, and ordering parameters, are estimated from correlation times and intensities of e.s.r. spectra. The molecular plane of the chelates incorporated into the mesophase was found to be oriented parallel to the applied field. The value of activation energy is higher for a mesophase of small size than for a larger one.