Mixture Of Coal Tar Pitch Research Articles

Электрохимические свойства углеродных материалов с высоким содержанием азота

The development and improvement of materials for storing electrical energy is important for the development of renewable energy technology. Some of the most suitable devices for storing electrical energy are supercapacitors, since they are able to withstand high charge and discharge currents, and they have a large number of recharge cycles. The characteristics of double-layer supercapacitors (DLSC) largely depend on the materials of the electrode on which the electrical double layer is formed. The most promising materials for the production of DLSC are carbon-based materials, such as activated carbons, soot, fullerenes, nanotubes, and graphene. It is possible to improve the characteristics of existing materials by increasing their electric conductivity, electrolyte wettability, and increasing the specific surface area. Doping carbon materials with nitrogen atoms makes it possible to solve these problems in many ways, including reducing their electric resistance. One of the ways to obtain nitrogen-rich carbon materials is the slow thermolysis of a mixture of coal tar pitch and melamine. This method makes it possible to obtain single-phase carbon materials with the pitch mass fraction up to 22 wt %. Electron microscopy methods have shown that with increasing nitrogen concentration, materials become loosened. With the use of X-ray phase analysis it has been shown that the resulting materials have a layered structure similar to graphite. Using the XPS method, it has been established that nitrogen atoms are embedded in the structure of the graphite sheet. The resulting materials are dominated by nitrogen atoms in the pyridine configuration. The electrochemical properties of the resulting materials have been studied in an electrochemical cell, which is a prototype of DLSC. The material with the nitrogen concentration of 4.2 wt % has the greatest capacity. The characteristics of the resulting DLSC have been compared with a commercially produced capacitor with a capacity of 220 mF and have shown their great similarity.

New method for synthesis of carbon foam on the base of mixture of coal tar pitch and furfural without using pressure and stabilization treatment

Carbon foam is an advanced porous material with multiple high-technology applications, due to its cell structure, light weight, high thermal stability, high thermal and electrical conductivity, as well as exceptional electromagnetic and acoustic properties. This work is dedicated to development of a new method for synthesis of carbon foam from a mixture of organic substances with suitable chemical properties and appropriate oxidation treatment, which allows synthesis of foam without the use of high pressure and stabilization step. The appropriate treatment conditions (thermo-oxidative modification with conc. H2SO4 or conc. HNO3 of mixtures of furfural and industrial coal tar pitch in different proportions), allowing the formation of porous structure of the resulting carbon foam, are established. The properties of the synthesized carbon foam can be controlled by varying the composition of the starting mixture and the type of oxidant. The formation mechanism of the porous structure of carbon foams is considered. Obtained carbon foam samples are characterized by XRD, Scanning Electron Microscopy, TG and DSC analysis, elemental analysis. The proposed new, less energy consuming synthesis method enables the production of carbon foam with very good physico-chemical properties.

Preparation of discrete cage-like oxidized hollow carbon spheres with vertically aligned graphene-like nanosheet surface for high performance Pb2+ absorption

A novel oxidized hollow carbon sphere (OHCS) as absorbent for the removal of Pb2+ was fabricated from the mixture of coal-tar pitch and aluminum isopropoxide followed by nitric acid oxidation. The as-prepared OHCSs were characterized by FESEM, TEM, BET, TG, FTIR and XPS, and meanwhile the effects of adsorption conditions on the Pb2+ removal were investigated by batch experiments. Results show that the OHCSs prepared possess discrete cage-like structures and well-defined inner/outer surface features, exhibiting vertically aligned graphene-like nanosheets on their surfaces with mesoporous nature and high hydrophobicity. The maximum absorption capacity for Pb2+ of the OHCSs can reach 280.79 mg g−1 at the optimum condition. The adsorption kinetic of Pb2+ onto the OHCSs was found to be well modeled by pseudo-second-order kinetic model, and the experimental equilibrium data were represented well by Langmuir isotherm model. Moreover, the OHCSs still exhibit excellent adsorption ability and stability after recycling 5 times, indicating its excellent reusability performance. Overall, the OHCS is a promising adsorbent for Pb2+ removal.

Study on electrochemical performances of composite carbon (FeO/C) materials fabricated by coal tar pitch and Fe3O4 particles

The new functional FeO/C composite carbon materials are successfully fabricated by controlling the adding amounts of Fe3O4 particles in mixtures of coal tar pitch and Fe3O4 particles. The structures of prepared FeO/C composite carbon materials were verified by XRD measurements. The excellent electrochemical performances of FeO/C composite carbon materials were evaluated in detail. For instance, the prepared materials show the high cycling performances at 679 mAh/g after carrying out charge-discharge 100 cycles. Meanwhile, the high rate performances and long cycle life characteristics of FeO/C composite materials were also observed. As a result, it is palpable that the carbon contents and specific area are the vital factors to improve the electrochemical performances of FeO/C composite materials, which effectively provides the reference to design the transition metal oxide/carbon composite materials as Li+ ion storage materials.

Fine-grained graphite with super molten salt barrier property produced from filler of natural graphite flake by a liquid-phase mixing process

A series of fine-grained graphite (FG) derived from the mixtures of coal-tar pitch, natural graphite flake (NGF) and tetrahydrofuran were prepared by a liquid-phase mixing process. And another FG was prepared from same coal-tar pitch and NGF by a conventional mixing process and named as CG. Compared with CG, several kinds of FG produced by liquid-phase mixing process exhibited much better comprehensive properties such as higher graphitization degree, smaller median pore diameter, lower open porosity, higher mechanical strength and better molten salt barrier property. And thus, these kinds of graphite not only might be used as moderator or reflector materials for molten salt reactor, but also might have great potential application in sealing area after being impregnated with resin, silver, PTFE, and so on. This work demonstrated that the liquid-phase mixing process had more advantages in improving the structure and properties of FG than conventional mixing process. Furthermore, the related mechanisms were also discussed in detail in this paper.

Numerical modeling of compaction and flow of coke/pitch mixtures using discrete element method

A variety of composite materials are composed of a viscoelastic matrix and elastic fillers. These materials range from polymer matrix composites to asphalt concretes. Discrete element method (DEM) has the capability of explicitly modeling the mechanical and physical properties of both matrix and aggregates. In the present work, DEM is applied to simulate the compaction and deformation of mixtures of coal tar pitch and calcined coke at 135, 140, 145 and 150 °C. Rheological properties of pitch and those of the binder matrix (mixture of pitch and fine coke particles) were experimentally measured by means of a dynamic shear rheometer. Obtained data was then used to estimate the four parameters of Burger’s viscoelastic model for pitch and binder matrix. The dynamic shear rheometer test was simulated by a three dimensional DEM model to verify the proposed viscoelastic model. Results showed that there is a very good agreement between the measured values and model predictions for complex, storage and loss moduli of pitch and binder matrix in a wide range of frequencies at all studied temperatures. The verified models were then used to study the compaction and densification of coke/pitch mixtures. Results showed that temperature has a positive effect on densification of coke/pitch mixtures and lower value of porosity is expected for the material pressed or vibrated at higher temperatures.

Preparation of Paving Asphalt by Co-pyrolysis of Coal Tar Pitch and FCC Slurry

Coal tar pitch was co-pyrolyzed with FCC slurry. The co-pyrolysis temperature is at 420oC with the mixture of coal tar pitch and FCC slurry mixing ratio of 1:1. The penetration, softening point, ductility and other properties meets the specifications of BZ200. The co-pyrolysis asphalt was analyzed using FTIR, NMR etc. The results show that there occurs hydrogen transfer and alkyl transfer reaction of FCC slurry and coal tar pitch during co-pyrolysis, leading to the improvement of molecular structure of modified asphalt.

Activated carbons prepared from mixtures of coal tar pitch and petroleum pitch and their electrochemical performance as electrode materials for electric double-layer capacitor

Activated carbons (ACs) were prepared by activation of coal tar pitch (CTP) in the range of <TEX>$700^{\circ}C-1000^{\circ}C$</TEX> for 1-4 h using potassium hydroxide (KOH) powder as the activation agent. The optimal activation conditions were determined to be a CTP/KOH ratio of 1:4, activation temperature of <TEX>$900^{\circ}C$</TEX>, and activation time of 3 h. The obtained ACs showed increased pore size distribution in the range of 1 to 2 nm and the highest specific capacitance of 122 F/g in a two-electrode system with an organic electrolyte, as measured by a charge-discharge method in the voltage range of 0-2.7 V. In order to improve the performance of the electric double-layer capacitor electrode, various mixtures of CTP and petroleum pitch (PP) were activated at the optimal activation conditions previously determined for CTP. Although the specific capacitance of AC electrodes prepared from CTP only and the mixtures of CTP and PP was not significantly different at a current density of 1 A/g, the AC electrodes from CTP and PP mixtures showed outstanding specific capacitance at higher current rates. In particular, CTP-PP61 (6:1 mixture) had the highest specific capacitance of 132 F/g, and the specific capacitance remained above 90% at a high current density of 3 A/g. It was found that the high specific capacitance could be attributed to the increased micro-pore volume of ACs with pore sizes from 1 to 2 nm, and the high power density could be attributed to the increased meso-pore volume.

Influence of air-blowing conditions on the properties of pitches and microstructure of pitch cokes

The influence of the raw materials and the conditions of air-blowing on the properties of the airblown pitches (ABP) produced and the microstructure of the corresponding pitch cokes is investigated. In the production of ABP, variation in the temperature (270–390°C) and duration (1–14 h) of air-blowing and the air flow rate (0–100 L/(kg h)) is investigated. The initial materials considered are coal tar pitch (CTP) and a mixture of CTP with the anthracene fraction from coal tar. The samples of ABP are characterized by a softening point of 87–239°C and contain 27.3–67.7% of the toluene insolubles and 8.8–58.2% of the quinoline insolubles. Although most of the pitch samples obtained exhibit a relatively high degree of condensation, they do not yield coke with uniform isotropic microstructure for the production of high-quality strong and dense structural graphite. The mean microstructure score of the coke obtained is 2.7–4.2; anisotropic structural elements predominate (with scores of 4 and 5); and numerous shrinkage cracks, pores, and other structural defects are observed. Since it is impossible to obtain satisfactory isotropic coke by the air-blowing of CTP, new methods of modifying carbon-bearing materials so as to obtain coke with uniform and isotropic microstructure must be developed.

Nanostructuring effect of multi-walled carbon nanotubes on electrochemical properties of carbon foam as constructive electrode for lead acid battery

In the present study, nanostructuring effect of multi-walled carbon nanotubes (MWCNTs) on electrochemical properties of coal tar pitch (CTP) based carbon foam (CFoam) was investigated. The different weight fractions of MWCNTs were mixed with CTP and foam was developed from the mixture of CTP and MWCNTs by sacrificial template technique and heat treated at 1,400 and 2,500 °C in inert atmosphere. These foams were characterized by scanning electron microscopy, X-ray diffraction, and potentiostat PARSTAT for cyclic voltammetry. It was observed that, bulk density of CFoam increases with increasing MWCNTs content and decreases after certain amount. The MWCNTs influence the morphology of CFoam and increase the width of ligaments as well as surface area. During the heat treatment, stresses exerting at MWCNTs/carbon interface accelerate ordering of the graphene layer which have positive effect on the electrochemical properties of CFoam. The current density increases from 475 to 675 mA/cm2 of 1,400 °C heat treated and 95 to 210 mA/cm2 of 2,500 °C heat-treated CFoam with 1 wt% MWCNTs. The specific capacitance was decreases with increasing the scan rate from 100 to 1,000 mV/s. In case of 1 % MWCNTs content CFoam the specific capacitance at the scan rate 100 mV/s was increased from 850 to 1,250 μF/cm2 and 48 to 340 μF/cm2 of CFoam heat treated at 1,400 °C and 2,500 °C respectively. Thus, the higher value surface area and current density of MWCNTs-incorporated CFoam heat treated to 1,400 °C can be suitable for lead acid battery electrode with improved charging capability.

The role of ferrocene on the enhancement of the mechanical and electrochemical properties of coal tar pitch-based carbon foams

In the present study, the role of ferrocene on mechanical and electrochemical properties of coal tar pitch (CTP)-based carbon foam (CFoam) was investigated. The different weight fractions of ferrocene were mixed with CTP and foam was developed from the mixture of CTP and ferrocene by sacrificial template technique. Before the characterisation of foams, it was heat treated at 1000 and 2500 °C in inert atmosphere. It was observed that the bulk density of CFoam increased with the increase in ferrocene content and as a consequence of an improvement of structural properties of the CFoam. The compressive strength increased by 60 and 62 % of 1000 and 2500 °C heat-treated CFoam with 5 wt% of ferrocene content. However, higher content of ferrocene had negative effect on the compressive strength. The electrical and thermal conductivity increased with the increasing ferrocene content and as a result of catalytic graphitization of ligaments in CFoam. The current density increased with the increasing electrical conductivity of CFoam, and it was 102 mA/cm2 at 10 wt% ferrocene. The specific capacitance was 865 μF/cm2 at scan rate 10 mV/s, which was due to the higher conductivity and surface area of CFoam. This demonstrated that ferrocene could be useful for improving the properties of CFoam.

Effect of activated carbons derived from different precursors on the hydrogen sorption properties of magnesium

The absorption–desorption characteristics towards hydrogen of obtained by ball milling under argon atmosphere magnesium based composites (containing respectively 95 wt% Mg and 5 wt% activated carbon (AC) derived from bean pods (BP), apricot stones (AS) and mixture of coal tar pitch and furfural (CTPF)), were investigated. Actually there is no substantial difference between the rate of hydriding and the absorption capacity for magnesium composite with AC derived from apricot stones, and for magnesium composite with AC derived from a mixture of coal tar pitch and furfural — the capacity is 6.13 wt% for the former and 5.98 wt% for the latter. More significant difference between the investigated composites was observed for the dehydriding process. The magnesium composite with synthetic carbon (from furfural and coal tar pitch) desorbs at 623 K and 0.15 MPa and the absorbed hydrogen about twice faster than magnesium composite with AC from bean pods. The activated carbon derived from a mixture of coal tar pitch and furfural has the highest specific surface area, and obviously this characteristic has important influence especially on the dehydriding kinetics of magnesium.

Synthesis and electrochemical properties of activated carbons and Li4Ti5O12 as electrode materials for supercapacitors

New activated nanoporous carbons, produced by carbonization of mixtures of coal tar pitch and furfural with subsequent steam activation, as well as electrochemically active oxide Li4Ti5O12, prepared by thermal co-decomposition of oxalates, were tested and characterized as electrode materials for electrochemical supercapacitors. The phase composition, microstructure, surface morphology and porous structure of the materials were studied. Pure carbon electrodes as well as composite electrodes based on these materials obtained were fabricated. Two types of supercapacitor (SC) cells were assembled and subjected to charge–discharge cycling study at different current rates: (1) symmetric sandwich-type SC cells with identical activated carbon electrodes and different organic electrolytes, and (2) asymmetric hybrid SC cell composed by activated graphitized carbon as a negative electrode and activated carbon–Li4Ti5O12 oxide composite as a positive electrode, and an organic electrolyte (LiPF6–dimethyl carbonate/ethylene carbonate (DMC/EC). Four types of carbons with different specific surface area (1,000–1,600 m2 g−1) and texture parameters, as well as three types of organic electrolytes: Et4NBF4–propylene carbonate (PC), LiBF4–PC and LiPF6–DMC/EC in the symmetric SC cell, were tested and compared with each other. Capacitance value up to 70 F g−1 for the symmetric SC, depending on the electrolyte microstructure and conductivity of the carbon material used, and capacitance of about 150 F g−1 for the asymmetric SC cell, with good cycleability for both supercapacitor systems, were obtained.

Synthesis of nanoporous carbons from mixtures of coal tar pitch and furfural and their application as electrode materials

Synthetic nanoporous carbons are prepared by polymerization of mixtures containing coal tar pitch and furfural in different proportions, followed by carbonization of obtained solid product and steam activation of the carbonizate. The chemical composition of the initial mixture significantly affects the physicochemical properties (surface area, pore structure, electro resistance and amount of oxygen-containing groups on the surface) of the obtained materials. The incorporation of oxygen in the precursor mixture by means of furfural, has a strong influence in the synthetic step; increasing the furfural content facilitates the formation of a solid product characterized by a large oxygen content. Moreover, the solid product is more reactive towards activation as the furfural content increases, giving rise to nanoporous carbons with large surface areas and unique chemical features (high density of oxygen functionalities of basic nature). These nanoporous carbons have been investigated as electrodes in electrochemical applications.

Carbon-coated Ni 20Si 80 alloy–graphite composite as an anode material for lithium-ion batteries

A carbon-coated Ni 20Si 80 alloy–graphite composite has been studied as the anode for lithium-ion batteries. The composite is prepared by simple heat-treatment of a mixture of coal tar pitch and a Ni 20Si 80–graphite composite at 900 °C and under argon. The Ni 20Si 80 alloy powders are synthesized by mechanical alloying. The composite demonstrates promising electrochemical properties such as high reversible capacity, excellent cycle performance, and sufficiently high initial charge–discharge coulombic efficiency. This suggests buffering and conductive actions on the main active material, viz., Ni 20Si 80 alloy, of the graphite. These two effects are strongly enhanced by the carbon coating treatment.

99/00070 Porosity development in steam activated chars from mixtures of coal tar pitch with graphite-FeCl 3 intercalation compounds

99/00070 Porosity development in steam activated chars from mixtures of coal tar pitch with graphite-FeCl 3 intercalation compounds

Porosity development in steam activated chars from mixtures of coal tar pitch with graphite-FeCl 3 intercalation compounds

The effect of addition of the iron graphite intercalation compound (GIC-FeCl 3) to coal tar pitch, used as a carbon precursor, on the porosity development in the resulting steam activated chars, was studied. Different conditions of chars preparation have been considered. Benzene (298 K), nitrogen (77 K), carbon dioxide (298 K) and water (298 K) sorption measurements were taken as basis for the porosity evaluation. The changes in the development of pores of different categories, caused by added amounts of GIC-FeCl 3 to coal tar pitch, temperature of carbonization and activation, and the degree of activation, are discussed.

96/06322 Carbonization of mixtures of coal tar pitch and graphite FeCl 3 compounds: A Mossbauer study

96/06322 Carbonization of mixtures of coal tar pitch and graphite FeCl 3 compounds: A Mossbauer study

A thermodesorption study of first stage graphite FeCl3 intercalation compounds

Abstract With the aim of synthesizing carbonaceous materials with specific adsorbent properties obtained from the pyrolysis of mixtures of coal tar pitch (CTP) and FeCl 3 graphite intercalation compounds (GIC), we present a study of the thermodesorption of first stage FeCl 3 GIC. These GICs were synthesized in a two temperature reactor with several kinds of graphites characterized by different granulometry and crystallinity (one a monocrystalline graphite and the others, polycrystalline). During heating under an inert atmosphere, FeCl 3 is decomposed into FeCl 2 and partially sublimed. At 500 °C, second stage FeCl 2 GIC reflections are observed on X-ray diffractograms, and at 750 °C, all iron and chlorine are desorbed out of the graphene layers in polycrystalline graphite, whereas monocrystalline graphite always contains some amount of iron and chlorine. Thermogravimetric evolution has been followed using a McBain balance. FeCl 3 desorption mainly occurs between 350 and 550 °C, and is more quantitative in the case of polycrystalline materials. The graphite granulometry significantly influences the desorption level, and the higher the heating rate, the greater the FeCl 3 desorption.

Carbonization of mixtures of coal tar pitch and graphite FeCl 3 compounds. A Mössbauer study

Mixtures of coal tar pitch (CTP) and first-stage FeCl 3-graphite intercalation compounds (GIC) have been synthesized with different GIC concentrations, then pyrolysed at different final temperatures and at several heating rates. Mössbauer spectroscopy has been used to characterize the iron states after these thermal treatments. The initial GIC is characterized by a typical singlet of highspin Fe(III) and we have studied the thermal stability of the GIC under nitrogen flow by X-ray measurements: FeCl 3 is progressively reduced to FeCl 2 and reduction is complete at 500 °C. At 750 °C, all iron has been removed from the graphene layers. After pyrolysis of the CTP and GIC mixture, different phases are identified in the resulting green-coke: metallic iron (α-Fe), which is present in greater quantities at high GIC concentrations and at higher pyrolysis temperatures, ferrous chloride, iron sulfide (FeS, troilite), nonstoichiometric Fe 1 − χS (pyrrhotite), and a not-well-determined fourth phase that could be austenitic iron (γ-Fe). After steam activation of the green-coke at 750 °C, most of the iron is oxidized into magnetite as confirmed by X-ray measurements and Mössbauer spectroscopy.