Coal Tar Research Articles

Structural and catalytic investigations of the novel carbon foam composites containing double hybrid nano reinforcements

Recently many attempts were conducted to enhance the structural morphology and properties of pitch-derived carbon foam (CF) by dispersing different additives in the CF matrix. But unfortunately, these additives enhance one property at the cost of another one. Herein, this work mainly considered the collaborated effect of multi-walled carbon nanotubes (MWCNTs) and functionalized nanodiamonds (FNDs) in the CF matrix phase was studied and compared with coupled CF/MWCNTs and CF/MWCNTs-FNDs hybrid composites. Coal tar pitch (CTP), a raw substance was applied to synthesize pretreated CF pitches via forming, carbonization, and graphitization techniques. Both types of nanocomposites were checked for various structural and morphological characterizations. Investigations revealed that the upgradation of microstructure, pore size, and uniform dispersion of samples can be made possible with the incorporation of nanofillers. However, between two different types of reinforcement materials, FNDs proved more influential to maximize the mechanical, thermal, and electrical attributes of CF nanocomposites. Different samples including pure CF, 1, 2, and 4 wt% CF/MWCNTs and CF/MWCNTs-FND were investigated. It was observed that with an increment in the amount of nanofiller, properties showed different variations. The best thermal, mechanical, and electrical properties were offered by 2 and 4 wt% CF/MWCNTs-FNDs hybrid samples respectively. Furthermore, the photocatalytic activity of the CF samples was investigated against Alizarin red (AR) dye. Results show that a hybrid sample of CF/MWCNTs-FND (4 wt%) is the most effective and sustainable as well as it almost decolorized about 88 % AR dye. Furthermore, it was also noticed that the dye decolorization increases with increasing catalyst dosage and pH of the medium and decreasing initial dye concentration.

Removal of Organochlorine Compounds from Coal Tar by Nucleophilic Substitution and Coalescence

AbstractAn integrated process of phase transfer nucleophilic substitution and coalescence is proposed to upgrade coal tar by simultaneously removing organochlorine compounds (OOCs) and water. For the phase transfer catalysts (PTCs) and nucleophiles, polyethylene glycol 400 (PEG‐400) and triethanolamine (TEOA) were the most effective to remove OOCs from coal tar. The optimal parameters of the dichlorination process in terms of molar ratio of PEG‐400 and TEOA to OOCs, reaction temperature, reaction time, and stirring speed were determined. The chloride removal efficiency reached 80.66 % when glass fiber was used for oil‐water coalescence separation. A promising method for simulllltaneously removing chloride and water from coal tar is provided.

Effect of swelling pretreatment by coal tar on the microwave pyrolysis of waste tires

Microwave pyrolysis is considered a promising method for the treatment of waste tires (WTs). A method of swelling modification coupled with microwave-induced pyrolysis was proposed in this study, based on the feature of swelling pretreatment reducing the cross-link density of molecular chains of rubber and the unique advantages of microwave pyrolysis. The modification effect of swelling on WTs and the effect of swelling pretreatment on the yields and compositions of three-phase products at different powers were investigated. It was found that the pyrolysis of swelled WTs was more complete and the yields of solid products were greatly decreased, with a solid product yield of 22.69% at 900 W, which was reduced by about 14.57 percentage points compared with that of raw WTs. In addition, there was a synergistic effect between coal tar and WTs, and the swelling of WTs by coal tar could significantly increase the yields of liquid products (up to 67.18%). This study will provide some directions for the efficiency improvement of microwave pyrolysis of WTs.

Ultrafine red phosphorus confined in reasonably designed pitch-based carbon matrix built of well-interconnected carbon nanosheets for high-performance lithium and potassium storage

Red phosphorus has been well-recognized as promising anode materials for lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs) due to its extremely high theoretical capacity and low cost. However, the huge volume change and poor electric conductivity severely limit its further practical application. Herein, the nanoscale ultrafine red phosphorus has been successfully confined in a three-dimensional pitch-based porous carbon skeleton composed of well-interconnected carbon nanosheets through the vaporization-condensation method. Except for the traditional requirement of high electric conductivity and stable mechanical stability, the micropores and small mesopores in the porous carbon matrix centered at 1 to 3 nm and the abundant amount of oxygen-containing functional groups are also beneficial for the high loading and dispersion of red phosphorus. As anode for LIBs, the composite exhibits high reversible discharge capacities of 968 mAh g−1, excellent rate capabilities of 593 mAh g−1 at 2 A g−1, and long cycle performance of 557 mAh g−1 at 2 A g−1. More impressively, as the anode for PIBs, the composite presents a high reversible capacity of 661 mAh g−1 and a stable capacity of 312 mAh g−1 at 0.5 A g−1 for 500 cycles with a capacity retention up to 84.3%. This work not only sheds light on the structure design of carbon hosts with specific pore structure but also open an avenue for high value-added utilization of coal tar pitch.

Liquid-liquid equilibria and mechanism analysis for separating phenol from coal tar containing toluene using 1,2-propanediol or 1,3-propanediol

Liquid-liquid equilibrium (LLE) data for the ternary systems of phenol + toluene + solvent were determined at 298.2, 308.2, and 318.2 K under 101.3 kPa, in which 1,2-propanediol (1,2-PDO) or 1,3-propanediol (1,3-PDO) was screened as the extracting agent. Two important indicators (distribution coefficient and separation factor) were calculated to evaluate the extraction performance of solvent for separating phenol from coal tar containing toluene. The separation factor was all greater than one, indicating that it is feasible to select 1,2-PDO or 1,3-PDO as extractants for separating phenol from coal tar containing toluene. Meanwhile, solvation free energy and interaction energy among the components were calculated to investigate the separation mechanism of phenol from coal tar containing toluene using 1,2-PDO or 1,3-PDO at a molecular level. Furthermore, NRTL and UNIQUAC thermodynamic models were utilized to correlate experimentally determined LLE data for phenol + toluene + solvent (1,2-PDO or 1,3-PDO) ternary systems at (298.2–318.2) K under 101.3 kPa, and the root-mean-square deviation value was used to evaluate the discrepancy between correlated and experimental values, yielding corresponding binary interaction parameters. In addition, graphical user interface method for topological analysis developed by Marcilla was used to corroborate the reliability of obtained binary interaction parameters.

Separation and thermal conversion of group components from medium‐low‐temperature coal tar pitch

AbstractMedium‐low‐temperature coal tar pitch (MLP) is a complex mixture of varied heavy organic hydrocarbons, which was generally used as the raw materials to produce artificial carbon materials. It was great significance for the high value‐added utilization of MLP to understand the property of components of MLP. The methanol, n‐heptane, n‐butanol, and dimethyl sulfoxide were used as the solvents to separate the components from medium‐low‐temperature coal tar pitch, and the eight kinds of components (include four kinds of solubles and four kinds of insolubles) were obtained after solvent separation. In addition, the liquid phase carbonization and calcination of medium‐low‐temperature coal tar pitch and its group components were carried out to obtain the corresponding pitch coke. The structural properties of components and pitch cokes have been studied in detail by FTIR, 1H‐NMR, TGA, optical microscope, scanning electron microscope, Raman spectrum, and X‐ray diffraction. The results showed that the optical microstructure of pitch coke prepared from the soluble group components of n‐heptane was mainly fibrous structure and leaflet structure, and the content can reach as 72.83%. In other words, the soluble group composition of n‐heptane was a suitable and excellent precursor for the production of needle coke. The optical microstructure of DMSOS‐C and HI‐C was only composed of fine mosaic structure, which was more suitable for the production of isotropic coke (a kind of special coke and also named as fine mosaic coke).

Printing Three-Dimensional Refractory Metal Patterns in Ambient Air: Toward High Temperature Sensors.

Refractory metals offer exceptional benefits for high temperature electronics including high-temperature resistance, corrosion resistance and excellent mechanical strength, while their high melting temperature and poor processibility poses challenges to manufacturing. Here this work reports a direct ink writing and tar-mediated laser sintering (DIW-TMLS) technique to fabricate three-dimensional (3D) refractory metal devices for high temperature applications. Metallic inks with high viscosity and enhanced light absorbance are designed by utilizing coal tar as binder. The printed patterns are sintered into oxidation-free porous metallic structures using a low-power (<10W) laser in ambient environment, and 3D freestanding architectures can be rapidly fabricated by one step. Several applications are presented, including a fractal pattern-based strain gauge, an electrically small antenna (ESA) patterned on a hemisphere, and a wireless temperature sensor that can work up to 350°C and withstand burning flames. The DIW-TMLS technique paves a viable route for rapid patterning of various metal materials with wide applicability, high flexibility, and 3D conformability, expanding the possibilities of harsh environment sensors.

Effect of coal tar pitch modification on the structure and char yield of pyrolysis epoxy resin carbons

Epoxy resin carbons are of high strength, high temperature resistance, and corrosion resistance, which are widely used as the precursor of carbon composite materials. However, the applications of epoxy resin carbons are greatly limited for the characteristic of non-graphitization and low char yield (22 wt%). In this paper, coal tar pitch was used to modify epoxy resin carbons via a simple heating mixing, pyrolysis and high temperature graphitization. The results show that the coal tar pitch content and heat treatment temperature can improve the ordered graphite carbon content. As the coal tar pitch content increase, the ordered graphite carbon content of modified epoxy resin carbon increase after 3000 °C graphitization for 0.5 h. Particularly, the graphitization degree of epoxy resin carbon and 40 wt% coal tar pitch modified epoxy resin carbon are 8.42 % and 44.21 %, respectively. The grain size (Lc = 13.84 nm) and grain stacking height (La = 7.79 nm) of 40 wt% coal tar pitch modified epoxy resin carbon are bigger than epoxy resin carbon (Lc = 3.44 nm, La = 3.45 nm). The ordered coal tar pitch graphite carbon and disordered epoxy resin amorphous carbon are evenly distributed in the modified epoxy resin carbon, indicating a good comparability of coal tar pitch and epoxy resin. Besides, the entangling carbon ribbon are observed in the epoxy resin carbon after graphitization at 3000 °C. With the coal tar pitch content increasing, the carbon element content and aromatic ring number of modified epoxy resin increased. As the coal tar pitch content increase, the char yield and thermal decomposition temperature of modified epoxy resin gradually increase. The char yield of 50 wt% coal tar pitch modified epoxy resin is 42 wt%, almost double that of epoxy resin (22 wt%). The char yield increased values of modified epoxy resin mainly inherited the high char yield of coal tar pitch (50 wt%) and a small portion of char yield increased value is from the chemical crosslinking weight gain. When the coal tar pitch content is 40 wt%, the chemical crosslinking weight gain reaches the maximum value of 15 wt%. Possible chemical crosslinking reaction can be epoxy group and hydroxyl group of epoxy resin and carboxyl group and phenolic hydroxyl group of coal tar pitch. This study provides some theory foundation for the future application of epoxy resin carbon composite materials.

Preparation of flotation refined carbon from gasification slag

Highly efficient and environmentally friendly utilization of coal gasification slag is a hot research subject in the coal chemical industry at present. The preparation of activated carbon with a flotation refined carbon from gasification slag, a long flame coal, a high temperature coal tar containing 70% asphalt and an active agent in proper proportion was carried out. The influence of activation temperature and time on the surface properties and compressive strength of the produced activated carbon was investigated in a tube furnace. The oxygen functional group, pore structure and absorption performance of the produced activated carbon were characterized by FT-IR, N2 adsorption-desorption, SEM and iodine adsorption. The COD removal from biochemical waste water by the produced activated carbon was verified. The results show that the key factors for the effective formation and expansion of pore are the suitable activation temperature and time for the floatation refined carbon from gasification slag as the feedstock. The activated carbon prepared by carbonization at 550 °C for 30 min and steam activation at 950 °C for 2 h exhibits a crisscross morphology of organic carbon components and minerals. The surface area, pore capacity and average pore diameter are 566 m2/g, 0.5611 mL/g and 5.1 nm, respectively, with the characteristics of a concentrated pore distribution and a certain quantity of mesopore. Both iodine value (650 mg/g) and methylene blue value (128 mg/g) meet the requirements of the Chinese standard “Technical Specifications and Test Methods of Activated Carbon for Purification of Industrial Wastewater”. The COD in biochemical waste water treated by the activated carbon for 60 min with a solid-to-liquid ratio of 0.6 g/L can be reduced to lower than 30 mg/L, meeting the B class water quality of the Chinese standard “Integrated Discharge Standard of Water Pollutants” (DB11/307—2013).

Regularities of changes in pitch characteristics when varying the parameters of PJSC “KOKS” coal tar distillation

The regularities of changes in the main characteristics of coal tar pitch (softening point, ash content, volatile matter yield, content of α-, α1-, α2-, γ- and β-fractions) obtained by coal tar distillation, were studied changing three process parameters – tar heating rate, temperature and duration of isothermal exposure. The mathematical model obtained in the form of regression equations satisfactorily describes the dependence of the studied pitch characteristics on the coal tar distillation process parameters and can be used to predict the quality of the resulting coal tar pitch.

Amorphous carbon nanosheets suitable for deep eutectic solvent electrolyte toward cryogenic energy storage

The emerging deep eutectic solvent (DES) electrolyte has great potential in realizing commercial-scale application of electric double-layer capacitors (EDLCs) served in low temperature environment. That goal, however, rests with how to design the interface structure of electrode materials for well-matching with DES electrolyte. Herein, porous carbon nanosheets (PCNs) were obtained from coal tar pitch through Friedel–Crafts acylation reaction and melting salt intercalation process. The morphology, specific surface area and porosity of porous carbon nanosheets were regulated by tailoring the abundance of the dangling-bonds grafted on the CTP molecules. Profiting from the large specific surface area, suitable pore structure and good two-dimensional structure to provide more active sites and enhance ion transport capacity, the PCNs-0.10 delivers a maximal specific capacitance of 504F g−1 at 0.1 A g−1, which is overmatch than most of previously reported for other carbon materials. As-assembled symmetrical EDLCs using K+ DES electrolyte, can be assembled to work at −40 °C to 75 °C and exhibit satisfactory energy density. The strategy proposed here has opened a new way for exploring the large-scale preparation of electrode materials suitable for ultra-low temperature capacitors.

Molecular Characteristics of Catalytic Nitrogen Removal from Coal Tar Pitch over γ-Alumina-Supported NiMo and CoMo Catalysts.

The removal of nitrogen from coal tar pitch (CTP) through the hydrodenitrogenation (HDN) of CTP and its molecular behavior were evaluated in the presence of NiMo/γ-alumina and CoMo/γ-alumina catalysts. Fourier transform ion cyclotron resonance mass spectrometry with atmospheric pressure photoionization was used to analyze the complicated chemical classes and species of CTP and the treated products at the molecular level. Nitrogen species were qualitatively analyzed before and after hydrotreatment. A single-stage hydrotreatment with an HDN catalyst resulted in a high sulfur removal performance (85.6-94.7%) but a low nitrogen removal performance (26.8-29.2%). Based on relative abundance analyses of nitrogen and binary nitrogen species, CcHh-NnSs was the most challenging species to remove during HDN treatment. Furthermore, prior hydrodesulfurization was combined with HDN treatment, and the dual hydrotreatments yielded a significantly improved nitrogen removal performance (46.4-48.7%).

Investigation of pitch modification and its effect on anode properties: Effect of pitch type

AbstractAluminium is produced by electrolysis using carbon anodes. These anodes are manufactured with dry aggregate (mainly calcined petroleum coke, butts, and rejected green and baked anodes) and coal tar pitch, which acts as a binder. Utilization of good quality anodes decreases the consumption of carbon and energy, hence the process cost as well as the emission of greenhouse gases (GHG). The interactions between coke and pitch play an important role in determining the anode quality. If they are compatible, pitch can penetrate into the pores of the coke particles as well as into the voids between the particles, resulting in denser anodes. One way to improve these interactions is to modify the chemical composition of pitch using an additive. The objective of this study is to investigate the effect of the pitch type on the effectiveness of pitch modification in improving the anode properties. Two types of pitch with different quinoline insoluble (QI) contents were used: one with high QI (HQI pitch) and the other with low QI (LQI pitch). They were modified using the same additive. The interactions between the pitches and the coke were studied by measuring the wettability of coke by the pitches. The pitch chemical composition was studied using FTIR and XPS. Then, anodes were produced and characterized. Their apparent density, electrical resistivity, air and CO2 reactivities, and permeability were compared. The results showed that the properties of anodes produced using modified HQI pitch were improved. Modifying LQI pitch did not significantly improve the anode properties.

Multi-scale analysis on the aggregation mechanism of oxygen-rich coal-derived asphaltene molecules

Significant differences exist in the structural features between coal-derived asphaltene and petroleum asphaltene (e.g., the degree of alkylation, aromatic nuclei size, heteroatom content, as well as morphology characteristics). The self-aggregation behavior exhibited by coal tar asphaltene for coal tar processing should be investigated in accordance with the structural characteristics of coal tar asphaltene. In this study, the focus was placed on the effect exerted by oxygen structure format, location and content on the aggregation behavior of asphaltene. The electrostatic potential (ESP) maps, theoretical reactivity parameters, molecular orbitals, dimerization interaction energies, and weak interactions of coal tar asphaltene were determined based on quantum chemistry. The self-aggregation behavior exhibited by coal-derived asphaltene was explored through molecular dynamics simulations. As indicated by the results of this study, the π-π interactions among asphaltenes were enhanced by the heteroatoms embedded in polycyclic aromatic hydrocarbons (PAHs). In the identical oxygen content, the π-π stacking of asphaltenes with five-membered heterocyclic structures turned out to be more intense. The carboxyl and hydroxyl were more likely to form hydrogen bonds, such that the stability of asphaltene aggregates was increased. Furthermore, as indicated by the molecular dynamics simulation results, the oxygen-containing structures far from PAHs exhibited small steric resistance and a higher probability of the formation of hydrogen bonds.

Influence mechanism of a compound collector from coal tar and dodecane in the flotation of fine molybdenite particles

With the depletion of high-grade molybdenum (Mo) deposits, it is more pressing to separate the low-grade deposits effectively due to the large demand for Mo. However, traditional hydrocarbon oil collectors such as kerosene suffered low collecting capacity for low-grade ores because of the fine disseminated nature and crystal anisotropy of molybdenite. In this study, the effect of a compound collector prepared from coal tar and dodecane (CTD) on the flotation of fine molybdenite was investigated by micro-flotation experiments, bubble-particle attachment tests, gas chromatography-mass spectrometry (GC–MS), density functional theory (DFT) calculations, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The results of micro-flotation experiments demonstrated that CTD improved the flotation recovery of fine molybdenite dramatically compared with dodecane and kerosene, the fine particles pretreated with CTD had a better affinity for bubbles, and a stronger mineralization efficiency was achieved than that with dodecane as the improvement of the surface coverage and attachment rate constant. The results of GC–MS, FTIR, and DFT calculations indicated that there were plenty of compounds with benzene rings in the CTD, especially for phenanthrene and naphthalene, which showed a stronger interaction on the (100) plane of molybdenite than dodecane, thereby proving a stronger affinity for hydrophilic planes. The results of XPS analysis depicted that more adsorption amounts were achieved on molybdenite by CTD than that of dodecane, and contact angle test results further demonstrated that the effect of CTD was stronger than dodecane in improving the hydrophobicity of fine molybdenite particles. In general, the compound collector (CTD) is beneficial to the improvement of attachment rate of molybdenite particles to bubble and hydrophobicity of molybdenite particles, which improves the flotation recovery of fine molybdenite. The extract from coal tar had more affinity for the (100) plane of molybdenite compared to the (001) plane through DFT calculations. The finding has important reference value and guiding significance for the future research on collectors for fine molybdenite flotation.

Isotropic coal tar pitch-based carbon fibers: Effect of nitric acid towards elimination of air-stabilization step

The remarkable properties exhibited by carbon fibers have generated considerable interest in seeking alternative approaches to replace time-consuming, energy-intensive, and multi-step procedures for their synthesis. Among the various stages involved in carbon fiber synthesis, the stabilization step plays a crucial role as it necessitates an extended duration to transform thermoplastic pitch-fibers into thermosetting fibers, thus preventing them from melting during high-temperature treatments. In this study, isotropic coal tar pitch (ICTP) was transformed into pitch fibers through melt-spinning process and subsequently subjected to chemical treatment for stabilization using varying concentrations (ranging from 5% to 50% v/v) of aqueous nitric acid (HNO3) solutions. The objective was to determine the optimal concentration for effective stabilization. Consequently, this research eliminates the conventional, time-consuming air-stabilization process by treating the pitch fibers with nitric acid prior to carbonization. To produce carbon fibers, all chemically stabilized pitch fibers were directly carbonized at 1000 °C. Comprehensive characterizations including Rheology, Elemental analysis, FTIR, TGA, FE-SEM, XRD, Raman, and XPS were conducted to investigate the chemical and structural transformations occurring during the fiber processing. It was observed that aqueous nitric acid solutions ranging from 15% to 30% (v/v) exhibited superior structural, morphological, and mechanical properties compared to other concentrations of HNO3.

Exploration of the mechanism for the extraction of phenolic compounds in model coal tar by choline chloride:ethylene glycol deep eutectic solvents

Exploration of the mechanism for the extraction of phenolic compounds in model coal tar by choline chloride:ethylene glycol deep eutectic solvents

Impact of Pitch Modification on Anode Properties: Effect of Additive Type.

Aluminum is one of the major industries in Canada. The main challenges facing the aluminum industry are carbon loss, energy use, greenhouse gas emissions, cell performance, and production costs, especially for high-amperage cells. The quality of carbon anodes plays a major role in the stability of cell operation and energy consumption. Anodes are made from petroleum coke, rejected green and baked anodes and butts, as well as coal tar pitch, which binds all of the particles. Although the industry depends on a steady supply of high-quality anodes, the availability of quality anode raw materials-coke and pitch-has decreased. A means of improving raw material quality is to modify their properties. In this work, using two additives, low- and high-quinoline insoluble (LQI and HQI) pitches were modified. These additives enrich the surface functional groups of the pitch, thereby increasing coke-pitch interactions. Various additive concentrations and pitch percentages were assessed. It is found that the choice of additive type has a marked effect on pitch properties, with different additives improving different pitches. Additive 1 is suitable for the HQI pitch, whereas additive 2 modifies the LQI pitch better. Anode properties are improved by modifying one of the pitches, whereas modifying the other pitch affects the anode quality to a lesser extent. Thus, the results showed that the modification of an already good-quality pitch (LQI pitch) does not significantly affect the anode quality. On the other hand, the modification of the inferior-quality pitch (HQI pitch) improved the anode quality and decreased the optimum pitch percentage necessary to obtain good anodes compared to the percentage of the LQI pitch needed. This would help decrease the anode production cost. The wettability tests give an indication of if the additive has the potential to improve the coke-pitch interactions, but it cannot predict the effect of pitch percent.

N, S co-doped porous graphene-like carbon synthesized by a facile coal tar pitch-blowing strategy for high-performance supercapacitors

Herein, coal tar pitch (CTP) derived nitrogen and sulfur co-doped porous graphene-like carbon (NSPC) is performed by an ammonium sulfate-assisted chemical blowing strategy. Afterward, NSPC was activated by KOH to form a-NSPC features a bubble-like structure with a thin porous shell and a well-balanced porous ratio. Serving as electrode materials for supercapacitors, the capacitance of a-NSPC was 368 F g−1 at 0.5 A g−1. Meanwhile, the prepared materials exhibit excellent cycling stability after 10,000 cycles. This work may not only prepare superior electrode materials but also provide a feasible strategy for large-scale production of high-performance and low-cost electrode materials.

Experimental Study on Coal Partial Gasification Coproducing Char, Tar, and Gas

Experimental Study on Coal Partial Gasification Coproducing Char, Tar, and Gas