Solvent Extraction Of Coal Research Articles

Synthetic Pitch from Solvent Extraction of Coal as a Source for High-Quality Graphite

This work evaluates the potential for obtaining graphitizable precursors from domestically available coal as a possible solution to the declining availability of high-quality precursors and projected rapid growth driven by demand for synthetic graphite in the US. The graphitizability of a coal-derived synthetic pitch (Synpitch) obtained by a novel solvent extraction process is compared with a commercially available petroleum pitch. The process outlined in this paper offers the advantages of lower temperature, pressure, and hydrogen addition requirement. An upgraded (higher H/C) aromatic pitch with low quinoline insoluble (QI) and ash content is obtained. The distinctions between the pitches have been characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis/differential scanning calorimetry. The pitches have been graphitized at 2500 °C and characterized by X-ray diffraction and transmission electron microscopy for graphitic quality assessment. The Synpitch showed larger crystallites (by over 50%) and markedly better nanostructure compared to the commercial pitch used in this study. The structural differences between the pitches are highlighted here to explain the significantly better graphitic quality of the Synpitch.

Interactions between Coal and Solvent during the Solvent Extraction of Coal in View of Free Radicals.

In this study, variations in the free radical concentration, degree of swelling (Q), and extraction yield of Buertai coal (C%, 80.4%) in 11 solvents with different characteristics were determined to investigate the interaction between the coal and solvent, as well as the bond cleavage during solvent extraction. Derivative thermogravimetry (DTG) results for the residues and raw coal were compared to confirm whether the covalent bond breaks during solvent extraction. The free radical concentration decreases in certain solvents but increases in a few others. The relative free radical concentration, Q, and extraction yield are positively correlated. The charge-transfer capability of the solvent, and in particular its electron-donating capability, plays an essential role in influencing the interaction between the coal and solvent. The increase in the free radical concentration during solvent extraction can be attributed to (1) the formation or decomposition of charge-transfer complexes, (2) dissociation of charge-transfer complexes into radical ions, and (3) breakage of weak covalent bonds. DTG results show the occurrence of weak covalent bonds breakage at temperatures of 133.9–320.1 °C during solvent extraction due to the reduction of the bond energy caused by the formation of radical ions.

Distribution of Sulfur during Solvent Extraction of Coals and Desulfurization of Extracted Product

Three kinds of coal with different ranks and sulfur contents were extracted using 1-methyl naphthalene at 350°C. The sample coals were fractionated into three fractions: a solvent-soluble fraction, a deposited fraction from the solvent-soluble fraction at room temperature, and the solvent-insoluble fraction. The forms of sulfur in the raw coals and the extracted products were determined by X-ray adsorption near edge structure analysis. Most of the inorganic sulfur was transferred to the solvent-insoluble fraction and the organic sulfur was distributed among the three fractions. Interestingly, the solvent-soluble fraction contained organic sulfur without inorganic sulfur, and only thiophenic sulfur was detected independent of coal type. Because of the high selectivity of imidazolium type ionic liquid for thiophenic sulfur, dimethyl imidazolium methyl sulfate was applied to extract the sulfur contained in the solvent-soluble fraction. The extractive experiment using ionic liquid showed that the sulfur content decreased linearly with the number of extraction stages. A high extent of desulfurization was obtained with a high concentration of ionic liquid.

Changes in sulfur functionality during solvent extraction of coal in HyperCoal production

In this paper, the structural changes of the chemical forms of sulfur in coal, as induced by thermal extraction with industrial solvents (HyperCoal [HPC] production), were examined using X-ray photoelectron spectroscopy (XPS). In raw coal, thiophenic sulfur is more common than alkyl sulfides, and the observed structural changes during solvent extraction depend on the initial chemical form of sulfur. The majority of sulfur remains in the residue after extraction, and inorganic sulfur is found only in the residue. Only thiophenic sulfur (~84%) and sulfoxides (~16%) were found in the resulting HPC; no other types of sulfur (e.g., alkyl sulfides) were detected. These results demonstrate that, during HPC extraction, sulfates are not extracted and that some or most of the extracted alkyl sulfides, sulfoxides, and sulfones are likely decomposed and eliminated as gases. It was found that thiophenic and sulfate sulfur are unaffected by the extraction process and are found in the HPC and/or the extraction residue.

Producing low-ash coal by microwave and ultrasonication pretreatment followed by solvent extraction of coal

Low ash clean coal was produced from Indian coking coal through microwave irradiation or ultrasonication followed by solvent extraction in N-methyl-2-pyrollidone (NMP) containing smaller amount of Ethylenediamine (EDA) or Monoethanolamine (MEA). Pretreatment by ultrasonication followed by extraction with only NMP gave 10–15% higher clean coal yield of (56–58%) than extraction with only NMP (without pretreatment). Effect of using up to 10% EDA as cosolvent in NMP led to maximum clean coal yield. However use of EDA concentration beyond this showed decrease in clean coal yield and increase in ash contents. Clean coal yield increases because EDA is a strong polar solvent and strong base, which disrupts coal interactions and breaks bonds in coal by acid-base interactions. The extraction yield with and without pretreatment and microwave irradiation led to the enhancement in the yield of clean coal and was found to be in the range of 66–70% with microwave irradiation, which was 3–4% higher than without pretreatment. Clean coal Free Swelling Index (FSI) was improved by one unit. This was demonstrated at lab scale. Subsequently, this process was scaled up to 40 kg/batch coal mini-pilot plant.

Study on the structure of small molecule compounds and their functional groups in coal

ABSTRACTSmall molecular compounds from Yanzhou Coal and Shenfu coal were extracted with tetrahydrofuran (THF). The experimental results showed that the end point of the solvent extraction of coal by THF was determined as 12 h. At this point, the extraction rates (ERs) of Yanzhou coal and Shenfu coal were 14 and 10.7%, respectively. The experimental results of the molecular weight and density showed that the extracted materials were the small molecular compounds. The IR characterization indicated that the structure of the small molecular compounds contained mainly the functional groups of aliphatic hydrocarbon, cycloalkane, aromatic hydrocarbons, alcohols, and ethers.

24.ハイパーコール(完全無灰炭)製造技術の開発-1 : 石炭の溶剤抽出と灰分の除去特性

24.ハイパーコール(完全無灰炭)製造技術の開発-1 : 石炭の溶剤抽出と灰分の除去特性

Behavior of radicals during solvent extraction of three low rank bituminous coals

Solvent extraction of coals has been practiced extensively for various purposes including the determination of coal structure. It is generally assumed that the extraction is mainly a physical process involving little change in covalent bonds. But different opinions were reported. This work studies the behavior of radicals during extraction of 3 low rank bituminous coals using 5 solvents, including hexane, toluene, tetrahydrofuran (THF), 1,2,3,4-tetrahydronaphthalene (THN), and N-methyl-2-pyrrolidinone (NMP), using electron spin resonance (ESR). The extractions are carried out at temperatures from the ambient temperature to temperatures somewhat higher than the boiling points of the solvents, as well as under ultrasound. It is found that the radical concentration of the coals changes during the extraction, and the change is influenced by temperature and varies with the solvent. The decrease in radical concentration in most solvents at temperatures lower than their boiling points is attribute to coupling of free radicals dissolved from the coals, while the increase in radical concentration at high temperatures and in NMP is attributed to the cleavage of weak bonds in coals by the solvents.

Optimization of solvent extraction process of some Turkish coals using response surface methodology and production of ash‐free coal

AbstractIn order to produce ash‐free coal (AFC) from three Turkish coals, solvent extraction of coals using 1‐methylnaphthalene (1‐MN) at different temperatures were conducted. The extraction yield of coals was found dependent on coal, temperature, and solvent type. When there was usage of 1‐MN as solvent, the extraction yield was low. However, on addition of N‐methyl‐2‐pyryrolidone (NMP) or quinoline (QN) into 1‐MN, the extraction yield increased. Following the extractions, we obtained AFC with less than 0.65% ash content for the three coals used in this study. The response surface methodology (RSM) was employed to investigate the solvent extraction conditions. The factors investigated were extraction temperature and additional polar solvent ratio. The obtained results demonstrated that either excess amount of polar solvent into 1‐MN should be added at low temperatures or extraction should be done at high temperatures using less polar solvent to obtain an increase in extraction efficiency. The sensitivity and validity of results obtained by RSM were confirmed through validation experiments. The results of validation experiments showed a good agreement between the experimental and predicted values (relative error <1.2) and that indicated the robustness of the models. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

Coal and solvent properties and their correlation with extraction yield under mild conditions

Coal solvent extraction is a clean coal technology that involves the extraction of organic matter from coal using solvents. In this study, the effects of various coal and solvent properties on extraction yield were studied and their correlations were observed. Solvent extraction was performed for fifteen coal samples of different ranks with eight solvents under mild conditions. Statistical analyses were then conducted to find correlations between the extraction yields and the coal and solvent characteristics. The extraction yield was strongly correlated with the atomic H/C ratio or volatile matter content. Among the solvent properties, the correlation between the electron donor, acceptor number (DN-AN) and yield was confirmed to be high. The results of multiple regression showed that positive correlations were found with the content of volatile matter of coal and polar force, DN-AN of solvent. Whereas negative correlations were found with the Ca/Mg content of coal and dispersion force, hydrogen bonding force of solvent. The regressionequation- calculated value was similar to the experimental value.

Effect of Direct Coal Liquefaction Conditions on Coal Liquid Quality

Solvent extraction of coal was investigated with a focus on the quality of the coal liquids rather than coal conversion. The aim was to determine how the hydrogen/carbon ratio and other quality mea...

Solvent–Coal–Mineral Interaction during Solvent Extraction of Coal

Solvent extraction of coal is a coal-to-liquids conversion process whereby the organic matter in coal is dissolved in a solvent to produce a substantially mineral matter free product. The solvent extraction of Poplar lignite coal was studied with three model solvents (tetralin, quinoline, and 1-naphtol) and one industrial coal liquid derived solvent. Of interest was the fate of hydrogen, nitrogen, sulfur, and mineral constituents during physical dissolution at 200 °C and during reactive dissolution at 400 °C. The hydrogen redistribution in all solvents at 400 °C was within a narrow range, even though hydrogen-donor solvents resulted in higher extraction yield and in a higher H/C ratio of the residue. Quinoline strongly interacted with the coal, which masked its high physical extraction yield at 200 °C and enabled more mineral matter to be stabilized in solution. This behavior is typical of nitrogen bases in the coal, but was amplified by quinoline. Nitrogen redistribution took place with all solvents to nitrogen enrich the residue. Little or no sulfur redistribution took place during solvent extraction at 200 °C with any of the solvents, but at 400 °C, sulfur was redistributed. Evidence that sulfur is removed from the mineral matter during solvent extraction was provided by an observed decrease in S/Fe ratio, decrease in sulfur content of the ash, and increase in S/C ratio of extraction residues.

Optimization of Solvent Extraction Process Parameters of Indian Coal

Medium coking coals from West Bokaro coalfield, India, were extracted with N-methyl-2-pyrrolidone (NMP) and ethylenediamine (EDA) under reflux condition at atmospheric pressure. The objective of the study was to maximize the clean coal yield maintaining the specified clean coal ash content. Experimentations using three level full factorial designs were carried out to elucidate the importance of variables such as extraction time, coal to solvent ratio, and filtration mesh size upon solvent extraction of coal. To determine the significance of the effects, Pareto chart, residual analysis, and surface plots were used. It was found that the maximum extraction yield was obtained for 1 h extraction time and 1:12 coal to solvent ratio. Finer mesh (0.025 mm) size in filtration was found favorable in producing low ash clean coal (CC). Under optimum conditions it was possible to produce clean coal with 6% ash and 55% yield for coals having about 29% ash.

Pitch production using solvent extraction of coal: Suitability as carbon anode precursor

Pitch production using solvent extraction of coal: Suitability as carbon anode precursor

Partitioning of Boron during the Generation of Ultraclean Fuel (HyperCoal) by Solvent Extraction of Coal

Extraction of coal by organic solvent is an effective strategy for producing clean fuel and thereby minimizing the ash-related problems and improving coal power generation efficiency. Up to date, most elements in coal extracts have been investigated, but little attention has been given to boron. In this paper, the partitioning behavior of boron has been investigated in one coal extraction process, named HyperCoal (HPC) generation, developed in Japan. Five coals were extracted by both 1-methynaphthalene and its mixture with 20 wt % polar indole for 1 h at 360 °C. Boron in coal extract (HPC), coal residues, and raw coals has been examined by inductively coupled plasma−optical emission spectroscopy and solid-state 11B magic angle spinning−nuclear magnetic resonance spectroscopy. The results indicate that, regardless of the coal rank, boron has a lower concentration in HPC than in the corresponding raw coal and coal residue. Up to 20% of the original boron could be eluted. The eluted boron is an organoboron complex associated chemically within the coal matrix which has the following characteristics: resonates from −5.88 to −7.00 ppm in 11B NMR spectra, completely decomposes when coal is ashed by plasma at 150−200 °C, and is insoluble in acetic acid while preferentially extracted by organic solvents. No boron-bearing mineral particles have been detected in HPCs. Regarding the elution amount of boron, it is a function of the fraction of organoboron in raw coal and HPC yield. For raw coal having more organoboron as well as a higher HPC yield, a larger fraction of its original boron could be extracted accordingly. The eluted boron could also in part undergo chemical reactions with coal radicals and/or polar indole to form new coordination states in HPCs.

Elution of Ti during solvent extraction of coal and the transformation of eluted Ti upon combustion

Solvent extraction of coal is an effective method for removing coal ash, thereby generating the ultraclean fuel that can be directly combusted in gas turbine. Due to their organic affinity, a few inorganic elements can be extracted as well. Ti in coal extract, its elution from raw coal as well as the transformation of eluted Ti during coal extract combustion, have been investigated. Two coals of the U.S. and their acid-washed samples were extracted under 1 MPa N2 (cold) at 360°C. The solvents used include nonpolar 1-methynaphthalene and its mixtures with polar indole. The results indicate that, Ti in coal extracts is mainly composed of nanoparticles including TiO2 (anatase) and Ti associated with quartz. These particles are insoluble in any acids, having a fine dispersion into coal matrix. Upon coal fragmentation at 360°C, they could be librated, and, hence, traversed the filter for isolating coal extracts. The organo-Ti was preferentially extracted as well, which is most likely in a form of Ti porphyrin or Ti chelated with phenol-oxygen. These findings also have implications for revealing the modes of occurrence of Ti in the raw coals. Combustion of coal extract at 1,000°C resulted in the formation of nanometric TiO2 polymorphs and much complex compound like FeZnTiO4. The former species could be mainly formed by the phase change of TiO2 (anatase) at high-temperatures, while formation of the latter one could involve the capture of metallic vapors like Zn on TiO2 polymorphs. The resultant nanoparticles may escape the conventional pollution control devices, causing environmental concern. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Studies on the Reaction Engineering of Combustion and Carbonization of Indian Coals, Depolymerized Coals and Residual Coal Obtained After Organo-Refining

Kinetics of the combustion of original and depolymerized Assam, Raniganj and Talcher coals and Neyveli lignite has been studied under non-isothermal conditions in a thermogravimetric analysis apparatus by employing Coats and Redfern kinetic modeling. Depolymerization of coals through acidic phenoation was found to improve the reactivity of the coals for combustion. Similarly, depolymerization reaction also led to the improvement in the pyrolysis behavior of coals. The order and activation energy of the reactions have been reported. The kinetics studies of the residual coal obtained after the successive solvent extraction of coal has also been studied. The present studies on the reaction engineering of coal conversion and utilization technologies may help in the reactor design and in the process development engineering.

Formation of humic acids from air-oxidized Alaskan subbituminous coals

The results of a study aimed at evaluating the effect of air oxidation on humic acid production from two Alaskan subbituminous C coals are reported. Raw as well as partly acid-demineralized and debituminized samples of the coals were oxidized at 120 and 180 °C in a forced air circulating oven for up to 12 d. Humic acid was extracted from the oxidized samples by sodium hydroxide. The yield of humic acid increased with increase in temperature and oxidation time. Humic acid production was enhanced by partial demineralization. Solvent extraction of coal before oxidation hindered humic acid formation. The rate of humic acid formation increased at first with increase in oxidation time, reached a maximum and then decreased.

Solvent extraction of coals during analytical solvent swelling. A potential source of error [Erratum to document cited in CA114(6):46240d

ADVERTISEMENT RETURN TO ISSUEPREVArticleSolvent extraction of coals during analytical solvent swelling. A potential source of error [Erratum to document cited in CA114(6):46240d]John W. Larsen, Jane C. Cheng, and Cheng Sheng PanCite this: Energy Fuels 1991, 5, 2, 354Publication Date (Print):March 1, 1991Publication History Published online1 May 2002Published inissue 1 March 1991https://doi.org/10.1021/ef00026a023RIGHTS & PERMISSIONSArticle Views20Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (44 KB) Get e-Alerts Get e-Alerts

Solvent extraction of coals during analytical solvent swelling. A potential source of error

Bruceton coal (Pittsburgh No. 8) was exhaustively extracted with pyridine, and the residue was swollen with toluene, chlorobenzene, and pyridine. The solvent volume used to swell a constant amount of coal was varied. The coal swelling in chlorobenzene and pyridine increased as the volume of the solvent used to swell the coal increased. Vapor pressure osmometry was used to measure the concentration of materials dissolved in the swelling solvents contacting the coal. Both chlorobenzene and pyridine extracted enough material from the coal residue to promote solvent activity and reduce solvent swelling. The concentration of extracted material decreased as the volume of the swelling solvent increased. The use of solvent:coal ratios in solvent swelling experiments is recommended and long exposure of the coal to the solvent after equilibrium has been reached should be avoided