High-temperature Coal Tar Research Articles

Adsorptive separation of anthracene and carbazole by carboxyl-functionalized carbon material derived from MAF-6

Anthracene and carbazole are high-value heavy carbon resources mainly found in the anthracene oil fraction of high-temperature coal tar. Because of their similar structures, traditional solvent crystallization methods are not capable of achieving the separation of high-purity anthracene and carbazole. In this study, MAF-6, a material that can be synthesized in large quantities at room temperature, was used as a sacrificial precursor, carbonized (MC-1000), and subsequently oxidized to form carboxyl-functionalized carbon material (CMC-1000). The presence of carboxyl groups, along with lactones, hydroxyl groups, and carbonyl groups in MC-1000 and CMC-1000, was confirmed through XPS spectra and Boehm titration. CMC-1000 showed an increase of 5.7 mmol/g in oxygen-containing functional groups. The adsorption and separation capacities of MAF-6, MC-1000, and CMC-1000 for anthracene and carbazole in model oil were investigated. FT-IR analysis and DFT calculations demonstrated that the major interaction between CMC-1000 and carbazole involved hydrogen bonding (N–H···O and N–H···N). The results show that CMC-1000 has a high separation selectivity for carbazole over anthracene, with a selectivity of up to 44.4. The formation of hydrogen bonds between the N–H group of carbazole and the oxygen-containing groups on CMC-1000 plays an essential role in achieving high adsorption capacity and selectivity. In addition, CMC-1000 showed strong regenerative capacity, maintaining a selectivity above 29.7 over five cycles.

Separation of quinoline from quinoline/2-methylnaphthalene using deep eutectic solvents: Experimental and COSMO-RS prediction

The high-temperature coal tar wash oil contains two valuable components, namely, quinoline and 2-methylnaphthalene. These two components are challenging to separate during the deep processing. To address this issue, the COSMO-RS (Conductor-like Screening Mode for Real Solvent) model was utilized to identify them as a potential deep eutectic solvents (DESs) extractant. Based on the calculated infinite dilution activity coefficient, the performance indexes of DESs, including selectivity, solubility, and performance index were determined and utilized to identify high-performance extractants for the quinoline/2-methylnaphthalene system. Finally five DESs were selected based on these indexes, they are DES1 formed by Choline chloride: propionic acid with the molar ratio of 1:1, similarly, DES2 is Choline chloride:oxalic acid of 1:1, DES3 Tetraethylammonium chloride:propionic acid of 1:1, DES4 Tetraethylammonium bromide:itaconic acid of 1:2 and DES5 Tetraethylammonium bromide:propionic acid of 1:2. The liquid–liquid phase equilibrium experiments of the aforementioned five DESs at different temperatures (30 ℃, 40 ℃, and 50 ℃) under atmospheric pressure were conducted. The results showed that five kinds of DESs had good extraction effect on quinoline. The DESs formed by choline chloride and anhydrous oxalic acid had the best extraction effect. The quantum chemical single-molecule optimization of different HBDs and HBAs in DESs, intermolecular interaction energy analysis and independent gradient modeling shows that it is mainly induced by the formation of shared electron pairs by providing empty orbitals from DESs and lone pair of electrons from the quinoline molecule, and the main force is the weak hydrogen bonding force.

Facile and controllable preparation of nanosheet hierarchical Y for enhanced adsorptive denitrogenation from fuels

Adsorptive removal of nitrogen containing compounds (NCCs) from high temperature coal tar over Y zeolites has received more attention for its mild operating conditions. In order to eliminate the diffusion limitation caused by zeolites micropores, a series of nanosheet hierarchical Y zeolites have been synthesized through a three–stage temperature method without the addition of template in this work. The results indicate that the particle size, pore structure and acid properties of synthesized samples can be easily tuned by controlling the H2O/SiO2 ratio of precursor gel, which was confirmed by a series of analysis. The adsorbent with the H2O/SiO2 ratio at 20.1 consists of best relative crystallinity of primary zeolite, the highest BET surface of 850 m2·g−1, the highest total acidity of 0.43 mmol·g−1 and the largest amount Lewis acid sites (LAS) of 928.2 μmol·g−1, which made it a superior candidate for denitrogenation adsorbents. In addition, the relationship between the structure of adsorbents and their denitrogenation performance was evaluated by batch adsorption experiments in model fuels. The results demonstrate that the ZY20.1 exhibited the highest adsorption capacity of 17.09 mg N·g−1 adsorbent for quinoline (QUI) and 21.51 mg N·g−1 adsorbent for indole (IND), respectively, which is roughly twice that of the conventional NaY. ZY20.1 also has an excellent adsorption selectivity for NCCs and can effectively resist the effect of competitive components. Furthermore, the adsorption performance in real fraction and its good regeneration performance of ZY20.1 confirm its potential commercial application. In this study, a kind of structurally controllable nanosheet Y zeolite with enhanced adsorptive denitrogenation was prepared by a green and environmental method, which will provide useful guidance for the development of efficient denitrogenation material.

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).

Distribution of Metallic Elements in Four Group Components of High-Temperature Coal Tar Pitch.

The metallic elements in high-temperature coal tar pitch (HCTP) will affect the properties of carbon materials produced from the HCTP. The study on the metallic elements in HCTP is essential for the quality improvement of its derived carbon materials. In this paper, the content of 15 metallic elements in HCTP and its four group components, including n-heptane-soluble substance (HS), n-heptane-insoluble-toluene-soluble substance (HI-TS), toluene-insoluble-quinoline-soluble substance (TI-QS), and quinoline-insoluble substance (QI), was determined. The results show that the content of Na, Ca, Fe, Mg, Zn, K, Pb, and Al is more than 100 ppm and is much higher than that of other metallic elements. The content of Ni, V, Cr, Mo, Sb, Cu, and Mn ranges from 0 to 50 ppm. By mass calculation of the contents of four group components in HCTP, it can be concluded that Na and Fe are randomly distributed in the group components. Al, Zn, Pb, V, and Mn are mainly distributed in the inorganic form in the QI component. Ca, Mg, K, Ni, Cr, Mo, Sb, and Cu are mainly distributed in the small molecular group components such as HS and HI-TS.

Study on the Preparation of Clean Liquid Fuel by Wide Fraction High-Temperature Coal Tar Deep Hydro-Upgrading on a Pilot Plant Trickle Bed Reactor.

High-temperature coal tar contains a high content of heavy components, and the mechanism of its hydrogenation to fuel oil has not been completely revealed at present. In this work, clean environmental friendly fuel oil was obtained from wide fraction high-temperature coal tar (WHTCT) hydrotreated in a three-stage continuous pilot-scale trickle bed reactor filled with commercial catalysts. The effect of reaction temperature (345-405 °C), reaction pressure (10-18 MPa), and LHSV (0.2-0.4 h-1) on the product properties was investigated while the hydrogen/oil ratio remained constant (2000:1). Simultaneously, four lumped kinetic models were established to study the effects of reaction conditions on each component and interconversion between them. The results showed that the increase in temperature and pressure and the decrease in LHSV can effectively improve the quality of products. Under the reaction conditions of a temperature of 390 °C, a pressure of 16 MPa, an LHSV of 0.25 h-1, and a hydrogen/oil ratio of 2000:1, the S and N in the feedstocks can be reduced from 4600 and 6800 μg/g to 24.06 and 14.32 μg/g in the products, respectively. So WHTCT can be used as a suitable feed to obtain gasoline and low-freezing point diesel blending components through hydrogenation. Tail oil (TO) can easily be converted into diesel fraction (DF) and gasoline fraction (GF) with high selectivity. DF can be converted into GF only at higher temperatures, and GF hardly undergoes cracking to gas. The established kinetic model can accurately predict the content of TO, DF, GF, and gas of the products. Therefore, the results can provide a certain valuable reference for further development of industrial applications.

Effects of co-carbonization of medium and low temperature refined pitch and high temperature refined pitch on the structure and properties of needle coke

Needle coke has attracted much attention as a high-quality raw material for high-power graphite electrodes and other advanced functional materials. In this study, needle coke was prepared by co-carbonization of medium and the low temperature coal tar refined pitch (RCTP) and the high temperature coal tar refined pitch (RHCTP). The effect of co-carbonization of blended refined pitches with different proportions on the structure and properties of needle coke was studied. Elemental analysis, 1H NMR spectroscopy, Fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry revealed the effect of changes in the key components of the blended refined pitch on the structure of needle coke. In addition, the structure and properties of needle coke were analyzed by polarized light microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and powder resistivity. The results showed that adding RHCTP to RCTP can increase the content of aromatic hydrocarbons and reduce the content of heterocyclic compounds in the blended refined pitch, which was beneficial to the evolution and growth of carbonaceous structures. The fiber content of needle coke (N-R-C-15) prepared by adding 15 wt% RHCTP to RCTP was 50 wt%, the optical texture index (OTI) of the coke was 63.04, Lc= 8.387 nm, La= 18.17 nm, d002 = 0.3427 nm, the content of well-aligned carbon microcrystals was 91.17 wt%, and the content of perfect graphite crystals reached 24.37 wt%. As the ratio of RHCTP in RCTP increased, the needle coke exhibited more fibrous structures, the degree of defects in graphite crystals decreasing, and the degree of graphitization increasing. In addition, with the increasing proportion of RHCTP in RCTP, the average resistivity of needle coke decreased from 167.55 μΩ·m to 144.5 μΩ·m, and the average powder compaction density increased from 1.065 g/cm3 to 1.206 g/cm3.

Mechanism for the catalytic thermal polycondensation of naphthalene at low temperature

Naphthalene is an important component of high temperature coal tar and its content can reach more than 10%. Catalytic polycondensation of naphthalene is an effective way to prepare mesophase pitch and functional carbon materials. In this work, anhydrous AlCl3 was used as a catalyst for the polymerization of naphthalene under atmospheric pressure below 170 °C and the reaction mechanism was then systematically investigated. The results indicate that at 110 °C, the polymer product is mainly composed of tricyclic compounds and the content of heavy products is only 29.5%. At 150 °C, four to five peri-condensed aromatic compounds turn to be the main components and the content of medium components remains about 50%. At 170 °C, there appear a large number of six-ring aromatic cores and the conversion of naphthalene reaches 90.7%. The polymer products exhibit good fluidity and solubility in THF, which can facilitate the high-temperature thermal polycondensation and subsequent graphitization process. With an AlCl3/naphthalene molar ratio of 1/100, the second to seventh order naphthalene oligomers are obtained by the simulation of the short chain oligomerization of naphthalene. In contrast, when the AlCl3/naphthalene molar ratio exceeds 10/100, acetylene and methylnaphthalene are produced by the catalytic pyrolysis of naphthalene. The mechanism of “Oligomerization-Pyrolysis-Aromatization” was then proposed to explain the molecular transformation from naphthalene to pitch, which should be useful for the production of mesophase pitch precursor.

Preparation and Characterization of Mesocarbon Microbeads by the Co-Polycondensation of High-Temperature Coal Tar Pitch and Coal Pyrolytic Extracts.

Mesocarbon microbeads (MCMBs) are a kind of engineering and functional artificial carbon materials generally prepared by the polymerization of polycyclic aromatic hydrocarbons. The physicochemical property of the raw materials plays a key role in the quality of MCMBs. For a detailed analysis of the synergistic effects of the generation of MCMBs, a high-temperature coal tar pitch was used as raw materials, and coal pyrolytic extracts were used as additive to synthesize the MCMBs. The microstructure and morphology of the derived MCMBs were determined by an optical microscope, scanning electron microscope, X-ray diffraction, Raman spectrum, and laser particle size analyzer. In fact, the addition of the coal pyrolytic extracts can adjust the molecular structure of the blending pitch, and the coal pyrolytic extracts can promote the generation of the MCMBs during the co-polycondensation process. The MCMBs obtained by co-polycondensation method have a good degree of sphericity, lower defects in the surface morphology, and a lower charge transfer resistance (Rct) of 4.677 Ω.

Overview: Effective Separation of Oxygen-, Nitrogen-, and Sulfur-Containing Aromatics in High-Temperature Coal Tar by Ionic Liquids and Deep Eutectic Solvents: Experimental and Computational

Overview: Effective Separation of Oxygen-, Nitrogen-, and Sulfur-Containing Aromatics in High-Temperature Coal Tar by Ionic Liquids and Deep Eutectic Solvents: Experimental and Computational

Ionic liquids design for efficient separation of anthracene and carbazole

• COSMO-RS is applied to screen ionic liquids for separation of anthracene and carbazole. • The anthracene with high purity can be obtained by ionic liquids. • The anthracene and carbazole do not form solid solutions in Ionic liquids. • The separation mechanism of anthracene and carbazole in Ionic liquids is discussed. Anthracene (ANT) and carbazole (CAR) are highly value-added compounds in chemical industry. They are always mixed in preliminary processing products of high temperature coal tar and need to be separated and purified. In this study, ionic liquids (ILs) were used to separate ANT and CAR. [C 3 PY], [PM 2 IM] and [PMPIP] cations along with 7 classes of anions were screened by the conductor-like screening model for real solvents (COSMO-RS). [PMPIP][TFAc] (IL a ) and [PMPIP][Ac] (IL b ) were selected and synthesized. The structures of ILs were studied by σ-profile at the micro-level to analysis the hydrogen bonds formed between anion of ILs and H-N of CAR. The ternary phase diagrams of ANT-CAR-ILs were plotted to analysis the separation efficiency. Two ILs were used as extractant to separate ANT and CAR. The separation results showed that the synthesized ILs were the highly efficient solvents. The purity of refined ANT separated by IL b was improved to 97.87 wt%, with a yield of 80.04 wt%. The separation mechanism of ANT and CAR was further discussed.

Study on the co-carbonization behavior of high-temperature coal tar pitch and raffinate oil of low-temperature coal tar

In needle coke industry, the raffinate oil from raw material refining could be used for co-carbonization to improve the structural evolution of aromatic feedstock with high aromaticity and low alkyl side chain content. High-temperature coal tar pitch (HCTP) and raffinate oil obtained from low-temperature coal tar (LCT) were used to prepare needle coke by liquid phase carbonization, and the characteristics of carbonization behavior as well as the structural evolution of blended materials were also investigated. The raffinate oil possessed abundant saturated compositions and the aromatic component distribution mainly concentrated in 1–3 cyclic aromatic hydrocarbons which resulted in a low yield of derived products and the carbonaceous sheets with poor planarity. Raffinate oil provided sufficient small molecular volatiles of alkyl radicals and generated abundant active sites for the polycondensation of HCTP with high aromaticity and low alkyl side chain content during co-carbonization. The addition of raffinate oil in HCTP facilitated the elimination of steric hindrance and healed the structural defects within the planar aromatic lamellae. This paper improved the utilization of raw material refining treatment and optimized the industrial structure of the needle coke preparation process.

Differences and correlations between microstructure and macroscopic properties of mesophase cokes derived from the components of high temperature coal tar pitch

It has been universally believed that the soluble and insoluble components of coal tar pitch obtained by solvent extraction were good precursors to prepare mesophase cokes. The microstructure and macro properties of mesophase cokes derived from the soluble and insoluble components are varied in general. In order to study the differences and correlations between the microstructure and macro properties of mesophase cokes, 16 kinds of component in two categories have been prepared mesophase cokes as the raw materials. Briefly, Scanning electron microscope (SEM), Polarizing Microscope (PM), Raman spectroscopy, X-Ray Diffraction (XRD), thermogravimetry (TG) and Micro-strength intensity (MSI) have been used to characterize microstructure and macro properties of cokes. In fact, the graphite structure in extract-based cokes is larger and more orderly than that in residue-based cokes. The MSI of residue-based cokes (66 ∼ 81%) is higher than that of extract-based cokes (53 ∼ 60%), while Tmax (615 ∼ 645 ℃ and 680 ∼ 715 ℃) of the two are opposite. In a word, the results indicate that all data of the two categories of cokes go to bipolar distribution. And the results of this work were helpful for understanding and providing direction for the evaluation of cokes used to prepare isotropic and anisotropic graphite.

Nitrogen-doped porous carbon supported nickel nanoparticles as catalyst for catalytic hydroconversion of high-temperature coal tar

A novel and highly active nitrogen-doped porous carbon-supported nickel catalyst Ni@N-PC was successfully developed by a thermolysis of nickel-based zeolitic imidazolate frameworks growing on both sides of graphitic carbon nitride and used for catalyzing hydroconversion of isopropanol soluble portion from ultrasonic extraction of high-temperature coal tar (ISPHTCT). The active nickel nanoparticles were mainly encapsulated on the top of carbon nanotubes and partially dispersed on the surface of carbon nanosheets. Naphthalen-1-ol was used as a model compound to investigate the catalytic hydroconversion activity under different reaction conditions and reveal the mechanism for catalytic hydroconversion. The ISPHTCT and catalytic hydroconversion products of ISPHTCT (ISPCHCP) were analyzed with gas chromatograph/mass spectrometer. The results show that 70% of naphthalen-1-ol was converted at 160°C and completely converted at 200°C for 120 min, and the ISPHTCT was greatly upgraded. A total of 180 organic compounds including 33 nitrogen-containing organic compounds, 11 sulfur-containing organic compounds and 39 oxygenates were identified in ISPHTCT, while no obvious nitrogen-containing organic compounds, sulfur-containing organic compounds and oxygenates were detected in ISPCHCP, indicating the excellent performance of Ni@N-PC for heteroatom removal. All the alkenes, cyclenes and alkynes were saturated and the majority of arenes were converted to cyclanes by catalytic hydroconversion over Ni@N-PC, which exhibited high catalytic hydrogenation activity.

Effect of the addition of deep eutectic solvent to the anthracene separation

Anthracene (AN) is an important fine chemical feedstock, mainly derived from the anthracene oil fraction of high-temperature coal tar. The traditional solvent crystallization method used to obtain anthracene involves large amounts of solvents. A method with a high separation capacity and a high selectivity needs to be developed urgently. To this end, the composition of crude AN oil and the solubility of its main components in xylene were determined, and phenanthrene in crude AN oil was extracted with xylene. Pure deep eutectic solvents (DESs) and DESs–organic solvent mixture were then applied to separate anthracene and carbazole, respectively. Based on the distribution coefficient, selectivity, and purity of the AN product, the influence of organic solvent type, the molar ratio of DESs to organic solvent, and DESs type on the separation efficiency were investigated. Finally, the separation mechanism was investigated with density functional theory calculations and UV–visible spectroscopy. The results show that the phenanthrene content decreased from 25.5% to 2.6% and most of other condensed aromatics in crude AN were removed after washing twice with xylene. DESs–organic solvent mixtures had better performance than pure DESs for the separation of anthracene and carbazole, and under optimal condition, the 97.5% purity of AN is acquired in a single separation step with a tetraethyl ammonium chloride–glycerol DESs–DMF mixture. The more complicated interactions between phenanthrene and xylene than between anthracene / carbazole and xylene favored the removal of phenanthrene. The hydrogen bond with the minimum bond energy (-17.6 kJ/mol) between DESs and carbazole is also stronger than that with the maximum bond energy (-16.8 kJ/mol) between DESs and anthracene. Adding DESs to organic solvent can enhance the interactions between carbazole and the solvent, but had no significantly influence on interactions between anthracene and the solvent, thereby facilitating the separation of anthracene and carbazole.

Insight into molecular interactions between condensed aromatics in high-temperature coal tar and organic solvents by combining experimental, density functional theory, and molecular dynamics

Kilogram-level extraction, modified high-pressure preparative chromatography (MHPPC), and flash preparative chromatography (FPC) were applied to separate condensed arenes (CAs) and heteroatom-containing aromatics (HACAs) from a high-temperature coal tar and its petroleum ether-extractable portion (PEEP). A series of CAs and HACAs were enriched from PEEP via MHPPC. Naphthalene and other 8 arenes were purified with purities of 99.9% and higher than 75%, respectively, by recrystallization and FPC. Density functional theory and molecular dynamics were used to calculate the solvation free energies (SFEs) and the complex intermolecular interactions (IMIAs), respectively, between solvent and solute at the molecular level. The difference in SFE is positively correlated with the number of aromatic rings of each compound. The IMIAs related to the separations include hydrogen bonds, such as >CH2···X (X denotes NH<, –N<, or HO-AR), >CO···X, and –O–H···X bonds, >CH2···π, >CO···π, –O–H···π bonds, π···π stacking, and van der Waals forces.

Characteristics and evolution of products under moderate and high temperature coal pyrolysis in drop tube furnace

Drop tube furnace is a high-efficiency pyrolysis reactor, which is helpful for fundamental research of coal base poly-generation technology. In this paper, the characteristics of coal pyrolysis product at various temperature using drop tube furnace were investigated. A typical Chinese lignite Pingzhuang coal was used in current research, pyrolysis temperature ranged from 600 to 1000 °C with a step of 100 °C. The compositions of pyrolysis gas, coal tar and char were characterized and discussed in detail. Results showed that volatiles and moisture content decreased after pyrolysis, hydrophilic functional groups like carboxyl and hydroxyl also decreased, pyrolysis was a dehydration upgrading process for lignite. Specific surface area and total pore volume increased from 1.65 m2/g and 11.57 mm3/g in raw coal to 199.10 m2/g and 191.95 mm3/g in 1000 °C char, respectively. As for pyrolysis gas, when temperature increased, H2 and CO increased obviously, other compositions like CO2, CH4 and C2~C3 hydrocarbons decreased, consequently, the gross heating value of pyrolysis gas decreased from 22.5 MJ/m3 at 600 °C to 13.1 MJ/m3 at 1000 °C. High temperature pyrolysis had a high content of syngas (H2+CO), which can be utilized as raw material in synthetic chemical industry. There were high content of toluene in low temperature coal tar. There were more polycyclic aromatic hydrocarbons and less aliphatic chain hydrocarbons in high temperature coal tar.

Formation of mesophase from the components of high temperature coal tar pitch

Formation of mesophase from the components of high temperature coal tar pitch

Effective Separation of Condensed Arenes from High-Temperature Coal Tar and Insight into Related Intermolecular Interactions

An extraction-column chromatography system was designed to enrich and purify condensed arenes (CAs) from a high-temperature coal tar (HTCT). Pyrene, fluoranthene, phenanthrene, anthracene, and naph...

Composition and Structural Characteristics of Heavy Distillate from Xinjiang High Temperature Coal Tar

Composition and Structural Characteristics of Heavy Distillate from Xinjiang High Temperature Coal Tar