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Easily soluble organic components in Santanghu long flame coal (SLFC) from Hami (Xinjiang, China) were separated by CS2 and acetone mixed solvent (v/v = 1:1) under ultrasonic condition, and the extract residue was stratified by carbon tetrachloride to obtain the light raffinate component (SLFC-L). The effect of solvent treatment on the composition and structure of the coal and its rapid pyrolysis products was analyzed. Solvent treatment can reduce the moisture content in coal from 9.48% to 6.45% and increase the volatile matter from 26.59% to 28.78%, while the macromolecular structure of the coal changed slightly, demonstrating the stability of coal's complex organic structure. Compared with raw coal, the relative contents of oxygen-containing functional groups and aromatic groups in SLFC-L are higher, and the weight loss rates of both SLFC and SLFC-L reached the maximum at about 450 °C. In contrast, the loss rate of SLFC-L is more obvious, being 33.62% higher than that of SLFC. Pyrolysis products from SLFC at 450 °C by Py-GC/MS are mainly aliphatic hydrocarbons and oxygenated compounds, and the relative contents of aliphatic hydrocarbons decreased from 48.48% to 36.13%, while the contents of oxygenates increased from 39.07% to 44.95%. Overall, the composition and functional group in the coal sample were changed after solvent treatment, resulting in a difference in the composition and distribution of its pyrolysis products. [ABSTRACT FROM AUTHOR]

Four supported catalysts, nickel and ruthenium on a HZSM-5 support, were prepared by equal volume impregnation and in-situ decomposition of carbonyl nickel. The properties of catalysts were investigated by catalytic hydro-conversion of 2,2′-dinaphthyl ether as the model compound and extraction residue of Naomaohu lignite as the sample under an initial H2 pressure of 5 MPa and temperature at 150 °C. According to the catalytic hydro-conversion results of the model compound, Ni—Ru/HZSM-5 exhibited the best catalytic performance. It not only activated H2 into H⋯H, but also further heterolytically split H⋯H into immobile H− attached on the acidic centers of Ni—Ru/HZSM-5 and relatively mobile H+. Catalytic hydro-conversion of the extraction residue from Naomaohu lignite was further examined over the optimized catalyst, Ni—Ru/HZSM-5. Detailed molecular compositions of products from the extraction residue with and without hydrogenation were characterized by Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry. The analytical results showed that the oxygen-containing functional groups in products of hydrogenated extraction residue were obviously reduced after the catalytic treatment. The relative content of oxygenates in the product with catalytic treatment was 18.57% lower than that in the product without catalytic treatment. [ABSTRACT FROM AUTHOR]

It is difficult to obtain comprehensive information on coal pyrolysis with a single analytical tool due to the diversity of coal pyrolysis products. Low-temperature pyrolysis of coals with three ranks was characterized by online analytical methods to accurately explore pyrolysis mechanisms. Thermogravimetric (TG) analysis was used to characterize the basic pyrolysis characteristics of the coals. In-situ pyrolysis technique combined with gas chromatography-mass spectrometry (Py-GC/MS) and pyrolysis synchrotron radiation vacuum ultraviolet photoionization time-of-flight mass spectrometry (Py-SVUV-PI-TOF-MS) were employed in explaining the mechanism of coal pyrolysis at low temperature. The temperature of macromolecules fragmentation increases with coal rank, and a higher coal rank leads to aromatic products with a larger ring size. Different trends of adsorbed substances in coal pores with coal rank and the corresponding pyrolysis products were analyzed by Py-SVUV-PI-TOF-MS. The peak area of ethanol decreased with increasing temperature, while the pyrolysis products increased. By combining Py-GC/MS and Py-SVUV-PI-TOF-MS, possible coal macromolecular structures were obtained by reverse extrapolation of the pyrolysis products. • Two on-line MS techniques were used to characterize pyrolysis products of coals. • The fracture temperature of the coal structure is obtained by Py-GC/MS. • Adsorbed gases and pyrolysis products are distinguished by Py-SVUV-PI-TOF-MS. [ABSTRACT FROM AUTHOR]

A low-rank coal was subjected to deoxygenation using NiO/Mo2O3-ZSM-5 as the catalyst and ethanol as the solvent under pressurized hydrogen circumstance to acquire a catalytic product (CP). Another parallel reaction was repeated with the same procedure but with nitrogen circumstance and without the catalyst to obtain a non-catalytic product (NCP). Both CP and NCP were analyzed with a Fourier-transform infrared spectroscopy, a gas chromatography/mass spectrometer (GC/MS) and an Orbitrap mass spectrometer (Orbitrap MS) to understand the deoxygenation features of low-rank coal. Low polar and molecular mass compounds were detected in NCP and CP using GC/MS. Compared with GC/MS, more species and high polarity were identified in NCP and CP by Orbitrap MS. The three analytical techniques indicated the effective oxygen removal during the catalytic treatment and provide a comprehensive evaluation of the deoxygenation process. [ABSTRACT FROM AUTHOR]

Comprehensive and in-depth understanding of the molecular structure of low-rank coals is the basis for clean and efficient utilization. The detailed molecular structure of sequential thermal dissolution (TD) extracts from a subbituminous coal was characterized using a high-resolution mass spectrometry run in a tandem MS method, in-source collision-activated dissociation. Cyclohexane and toluene TD extracts released compounds with less oxygen and more nitrogen atoms located on aromatic cores compared to ethanol and isopropanol TD extracts. Archipelago-structured compounds presented in asphaltenes were also observed in compounds from toluene TD extract. Principle component analysis, a multivariate statistical method, was introduced to mine molecular characteristics of the TD extracts. TD yield and relative abundance of CH class (without heteroatom) became the key point to determine the clustering pattern for whole molecules and aromatic cores, respectively. • Coal extracts were characterized by high resolution tandem mass spectrometry. • A statistical method was introduced to mine molecular characteristics of extracts. • Detailed molecular characteristics is important for the downstream coal processing. [ABSTRACT FROM AUTHOR]

Rationale: Gas chromatography/mass spectrometry (GC/MS) and high‐performance liquid chromatography/time‐of‐flight mass spectrometry (HPLC/TOF‐MS) were used to separate and reveal the molecular characteristics of organic matter in low‐rank coals. Methods: Six soluble portions (SPs) were obtained by sequential thermal dissolution (TD) of two low‐rank coals in the order of cyclohexane, acetone and methanol solvents at 300°C. Organic matter with different molecular characteristics were enriched in eachTD extract, which was further separated and analyzed by GC/MS and HPLC/TOF‐MS using an electrospray ionization source in positive mode to obtain a comprehensive understanding of the structural composition of coals. Results: Low polarity compounds like alkanes and arenes have a better solubility in cyclohexane. Phorone has the highest relative abundance in the acetone SPs, and the main compounds detected in the methanol SPs are alcohols and phenols. According to the data from HPLC/TOF‐MS, most of the oxygen atoms are in the form of carbonyl and alkoxy groups. The nitrogen‐containing compounds in SPs are mainly saturated aliphatic amines and pyridines. The sulfur‐containing compounds mainly exist in the form of thioalkanes and thiophenes. Conclusions: Non‐destructive methods were used to obtain soluble matter from coals, and different chromatographic and mass spectrometric techniques were used to separate and analyze the organic matter in coals. Detailed molecular structural information was obtained for the efficient and clean utilization of low‐rank coals. [ABSTRACT FROM AUTHOR]

Thermal dissolution (TD) and ultrasonic-assisted extraction (UAE) were applied to the extraction of soluble components from Shengli lignite (SL) and Shenfu sub-bituminous coal (SS) using cyclohexane as the solvent. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOF-MS) was used to analyze the complex molecular composition of soluble fractions. The powerful separation ability of GC × GC/TOF-MS enriches compounds with similar molecular characteristics. The extracts of SL exhibited a high relative abundance of oxygen-containing compounds, up to 81.10 % in SL 100. The extracts of SS had a high relative abundance of hydrocarbons such as 70.30 % in SS 100. Meanwhile, those hydrocarbons and oxygenates embraced a considerable variety of biomarkers of coal, which were the constituents of plants and microbes from ancient times, including aliphatic hydrocarbons, sesquiterpenoid compounds, long-chain fatty compounds, furans, and aromatic esters. TD at below 200 °C mainly induced the dissociation of intermolecular interactions, but both the dissociation of intermolecular interactions and the partial cleavage of weak covalent bonds at 300 °C. • GC × GC/TOF-MS enriches compounds with similar molecular characteristics. • Supercritical TD of cyclohexane promotes the dissociation of strong intermolecular interactions. • CH and O class compounds in coal exhibit biological characteristics of original plants. [ABSTRACT FROM AUTHOR]

Catalytic deoxygenation of coal is an important step to obtain high quality coal-derived liquid fuels. Bimetallic catalysts exhibit excellent hydrodeoxygenation performance, because their synergistic effects. In this work, NiO–Mo 2 O 3 /ZSM-5 was prepared by impregnation method, and applicated to catalytic hydrodeoxygenation of Wucaiwan long flame coal (WCW). The thermal dissolution (TD) and catalytic hydrodeoxygenation (HDO) of WCW were investigated using cyclohexane as the solvent. The soluble portions from TD (SF NHDO) and HDO (SF HDO) were analyzed by gas chromatograph/mass spectrometry. The relative abundance of arenes and alkanes in SF HDO increased by 12.30 % and 29.98 %, respectively, compared to that in SF NHDO. Most detected oxygen-containing compounds in SF NHDO were alcohols and ethers, and their relative abundances decreased by 50.27 % and 84.13 %, respectively, after the catalytic treatment. Thus, the cleavage of C–O bond and deoxygenation in WCW were significantly proceeded during the HDO of coal over NiO–Mo 2 O 3 /ZSM-5 catalyst. The hydrodeoxygenation mechanism was proposed according to the catalytic deoxygenation of model compounds. Mobile H+ attacks oxygen atom and iso-carbon in coal, and produces aryl-molecules and aromatic alcohols. Aryl-molecules can be also generated from the attacking of H+ to the oxygen atom in aromatic alcohols. • NiO–Mo 2 O 3 /ZSM-5 was prepared for hydrodeoxygenation of long flame coal. • The catalyst is effective for the generation of arenes and alkanes. • Hydrodeoxygenation mechanism was revealed via catalytic reaction of model compounds. [ABSTRACT FROM AUTHOR]

Dayan lignite was subjected to thermal dissolution sequentially with cyclohexane, acetone, and methanol. Each thermal dissolution extract was subjected to further separation/enrichment using column chromatography, which was sequentially eluted with petroleum ether, a mixture of ethyl acetate and petroleum ether (vol:vol = 1:1), and ethyl acetate. The three thermal dissolution extracts and nine enrichment subfractions were characterized by an Orbitrap mass spectrometry equipped with an atmospheric pressure chemical ionization ion source. The mass spectrometry data were also statistically analyzed by principal component analysis, which can reduce the dimensionality of data and classify multiple samples according to principal components. Identified compounds in the extracts and subfractions are classified into eight classes according to the heteroatom distribution. Hydrocarbon class is mainly presented in the petroleum ether fraction, and oxygen class, nitrogen class, and oxygen‐nitrogen class are distributed in both petroleum ether/ethyl acetate and ethyl acetate subfractions. The combination of different analytical methods enhances the understanding of coal at the molecular level and provides important data for downstream refining processes. [ABSTRACT FROM AUTHOR]

An active and novel magnetic difunctional solid superbase catalyst Ni‐Mg2Si/attapulgite powder (AP) was prepared by thermally decomposing nickel tetracarbonyl onto the as‐synthesized Mg2Si/AP followed by impregnating Mg2Si onto AP in CCl4 and characterized by multiple analyses. It was also successfully used in the catalytic hydroconversion (CHC) of coal‐related model compound oxybis (methylene) dibenzene (OBMDB) and an extract (E) from Piliqing subbituminous coal (PSBC) in n‐hexane. As a result, OBMDB was completely converted to methylcyclohexane by the CHC under 3 MPa of initial hydrogen pressure at 240 °C for 2 h. Ni‐Mg2Si/AP can activate H2 to biatomic active hydrogen (H...H) and split H2 to immobile H+ attached on the Ni‐Mg2Si/AP surface and relatively mobile H−. Then the bridged linkage (BL) in OBMDB can be cleaved by H− attack on a α‐carbon atom in OBMDB, producing toluene and benzyloxy anion, which abstracts H+ from the Ni‐Mg2Si/AP surface to afford phenylmethanol (PM). The α‐carbon in PM is attacked by H‐ to generate toluene and HO−. H...H transfers to benzene ring in toluene yields methylcyclohexane. The soluble portion (SP) from the CHC (SPE‐CHC) and non‐CHC (NCHC) (SPE‐NCHC) of E were analyzed with a gas chromatograph/mass spectrometer and Fourier transform infrared spectrometer. Non‐substituted cycloalkanes (NSCAs) are predominant in the SPE‐CHC, accounting for 66.9 % of the total group components, and interestingly 65.3 % of NSCAs is cyclohexane, while non‐substituted arenes are the most abundant in the SPE‐NCHC. The results indicate that the CHC is beneficial to the fracture of COCBB and hydrogenation of ARs to produce more NSCAs. [ABSTRACT FROM AUTHOR]

In‐depth understanding of coal conversion processes is a key step for clean and efficient utilization of coals in chemical industry. Currently, most analytic methods aim to evaluate heteroatom release on the entire molecules. However, the production of value‐added chemicals from complex mixtures like coals are technically demanding which inevitably requires in‐depth fundamental knowledge of the treatment processes for coals. In‐source collision‐activated dissociation (ISCAD), a mass spectrometric method, can obtain details of aromatic cores and was employed in this work to provide in‐depth understanding of the catalytic conversion process of a low‐rank coal under different solvent conditions. Different heteroatom release patterns on aromatic and alkyl locations were observed for the solvents. Each solvent exhibited a characteristic preference over deoxygenation/denitrogenation on aromatic versus alkyl positions. Such preference is important for developing a desired catalytic treatment for a targeted heteroatom release. Overall, this study provides novel insights in catalytic heteroatom release processes during coal conversion that may be critical for the production of value‐added chemicals from coals. [ABSTRACT FROM AUTHOR]

Highlights • HCA and EMGM are introduced to reach in-depth statistic results for coal extracts. • The similarities and differences of clusters are visually exhibited in a plot via HCA. • Molecular structures in the same EMGM model have a certain similarity. Abstract A coal was extracted and thermally dissolved with cyclohexane, acetone and methanol sequentially. The ultrasonic extracts and thermal dissolution (TD) products were analyzed using an Orbitrap mass spectrometer (MS) with an atmospheric pressure chemical ionization source in positive ion mode. Large amounts of MS data were obtained but there were challenges in obtaining meaningful information from the data. The purpose of cluster analysis is to reduce complex multivariate data into meaningful groups. Two cluster analysis methods, hierarchical cluster analysis and expectation maximum algorithm based on Gaussian mixture model (EMGM), run by R language were introduced to obtain in-depth statistical results for compounds in both extracts and TD products. Seven types of heteroatomic compounds (O 1 , O 2 , N 1 , S 1 , O 1 N 1 , O 1 S 1 and N 1 S 1) in the extracts under the condition of ultrasonic extraction with cyclohexane were clustered with EMGM and possible structures of the related models can be inferred by analyzing the relationship between carbon number and double bond equivalent. The application of cluster analysis will provide methodological guidance in studying the structure of coal molecules. [ABSTRACT FROM AUTHOR]

Dayan lignite (DL) was subjected to thermal dissolution sequentially with cyclohexane, acetone and methanol to obtain three filtrates. The filtrates were characterized by Fourier transform infrared spectroscopy, gas chromatography/mass spectrometry (GC/MS), and time-of-flight mass spectrometry (TOF-MS) equipped with atmospheric pressure photoionization (APPI), electrospray ionization (ESI) or direct analysis in real time (DART) to understand the structural features of DL. Aliphatic hydrocarbons, furans and alcohols were enriched in the filtrate of cyclohexane, acetone and methanol, respectively, according to the data of GC/MS. One ring aromatics was also identified by GC/MS as major species in the three filtrates. Both GC/MS and APPI-MS can well analyze compounds with low polarity, but APPI-TOF-MS in this work successfully characterized polycyclic aromatics and extended the measurement range (molecular weight and ring size) of GC/MS. ESI-TOF-MS is suitable to analyze polar compounds in coal. Data from ESI-TOF-MS indicated that heteroatom compounds including non-aromatics and aromatics with 1-2 rings are the major polar components in DL. As an ambient MS ionization method, DART shortened the analysis time without sample pretreatment and more aromatics over 4 rings were identified by DART-TOF-MS. Characterization of the complex coal filtrates with multiple mass spectrometers provided a full view of the molecular information of DL. [ABSTRACT FROM AUTHOR]

Catalytic deoxygenation of coal enhances the stability and combustion performance of coal-derived liquid fuels. However, determination of the selectivity of removal of oxygen atoms incorporated in or residing outside of aromatic rings is challenging. This limits the ability to evaluate the success of catalytic deoxygenation processes. A mass spectrometric method, in-source collision-activated dissociation (ISCAD), combined with high resolution product ion detection, is demonstrated to allow the determination of whether the oxygen atoms are in aromatic compounds reside outside of aromatic rings or part of the aromatic system, because alkyl chains can be removed from aromatic cores via ISCAD. Application of this method for the analysis of a subbituminous coal treated using a supported catalyst revealed that the catalytic treatment reduced the number of oxygen-containing heteroaromatic rings but not the number of oxygen atoms residing outside the aromatic rings. [ABSTRACT FROM AUTHOR]

A series of carbon disulfide/acetone mixtures were used to extract organic species from Shengli lignite, a Chinese coal. Orbitrap mass spectrometry coupled with electrospray ionization was used to characterize the molecules in the extracts. Heteroatomic species, including oxygenates, nitrogenates, and sulfonates, were determined. Pure carbon disulfide or acetone had the lowest extraction for oxygenates while the mixtures increased the relative abundance of oxygenates. From the value of the double bond equivalence, the compounds with 1 oxygen contained the highest concentrations of aromatics and aliphatics, but compounds with 6 were aliphatic with a double bond equivalence of 3. For compounds containing 2 oxygens, aromatics with one ring were present at the highest concentrations in the 1:1 carbon disulfide:acetone extract. For compounds containing 3, 4, and 5 oxygens, most aromatic species were identified with double bond equivalence values between 4 and 6, showing the presence of an aromatic ring. The results indicated that the solvent mixtures enhanced the extraction of oxygenates from Shengli lignite. [ABSTRACT FROM PUBLISHER]

• Preparative HPLC separated and enriched soluble organic matter in coal. • Three times of compounds were identified after the pre-separation. • Molecular polarity and alkyl chain structure of analyte determine elution time. • Unsupervised analysis methods follow different clustering principles. Three soluble fractions (SFs) of a low-rank coal were obtained by sequential thermal dissolution (TD) using cyclohexane, toluene and methanol as the solvent. SFs were further separated using preparative high-performance liquid chromatography (HPLC) to obtain subfractions. Both SFs and subfractions were characterized by gas chromatography/mass spectrometry (GC/MS). Low polar compounds such as alkanes and arenes were enriched by cyclohexane. A large number of arenes and esters were detected in toluene extracts. Strong polar compounds like phenols were concentrated by methanol. After the separation by using preparative HPLC, more phenols, alcohols, esters and ketones were identified in subfractions, and the number of compounds detected by GC/MS increased by around 3 times. In addition, two trace compounds, (2,6-dimethoxybenzoyl chloride and tetrachloro-o-benzoquinone), were identified and one compound, 1,4-benzene-dicarboxylic acid-bis(2-ethylhexyl) ester, was enriched to 89.9% after separation. Two unsupervised analysis methods, hierarchical cluster analysis and principal components analysis, revealed the differences in distributional and compositional features of SFs and subfractions. [ABSTRACT FROM AUTHOR]

The effects of mechanical activation (MA) atmosphere on the co-liquefaction of Xigou coal and Karamay petroleum vacuum residues were investigated. MA induces a smaller particle size of coal powders, which are more easily dissolved in wash oil during co-liquefaction. FT-IR and 13C NMR data of coal samples show that MA can partially break alkyl side chains. Especially, it is easier for MA under hydrogen and air atmosphere to shorten or break alkyl side chains and bridged bonds compared to vacuum and nitrogen atmosphere. MA enhances pyrolysis reaction activity of coal samples through decreasing the apparent activation energy, which is conductive for co-liquefaction. For MA with hydrogen atmosphere, the highest conversion rate and oil yield of co-liquefaction are obtained, which are 98.2% and 84.4%, respectively, followed by air atmosphere. More distillate oil and heavy oil are produced from co-liquefaction with MA under hydrogen atmosphere, but fewer gaseous products. There are 9.7% petrol generated from co-liquefaction with MA under air atmosphere, which are higher than that from other atmospheres. MA partially destroys the physicochemical structure of coal and increases the concentration of free radicals because of the energy generated by collision and friction, thereby enhancing the reactivity in co-liquefaction. • Alkyl side chains and ether bonds in coal are broken through mechanical activation. • Mechanical activation enhances pyrolysis reaction activity of coal samples. • Hydrogen radicals determine the highest conversion rate and oil yield. • More petrol is generated from co-liquefaction with mechanical activation under air. [ABSTRACT FROM AUTHOR]

Oxidative depolymerization of low-rank coals is promising for obtaining benzene carboxylic acids (BCAs). However, it is hindered by the low yield of BCAs along with a large number of alphatic acids. Thermal dissolution could modify the physico-chemical structural features of low-rank coals, which is expected to improve the oxidation of LRCs. In this paper, lignite and subbituminous coal were firstly subjected to thermal dissolution with cyclohexane at 250 °C for 2 h. Then, the raw coal and the corresponding thermal insoluble portion (TIP) were oxidized by NaOCl under the same conditions. The residual yields of TIPs oxidation were both lower than those of raw coals oxidation, indicating that TIPs were more easily oxidized than the raw coals. The yield of BCAs obtained by TIPs oxidation was above 19% higher than that from the oxidation of raw coals. Meanwhile, the selectivity of BCAs was improved in the resulting oxidation products from TIPs compared with that from the raw coals. The relationship between BCAs generation and thermal dissolution of low rank coals was investigated by ultimate analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The results suggested that thermal dissolution could enrich aromatic portion in the remaining TIPs, resulting in an increasing of the yield and selectivity of BCAs. Simultaneously, thermal dissolution raised the specific surface area and expanded the looser space structure of TIPS, which were beneficial for the sufficient collision between aromatic structures and oxidant, facilitating the oxidative depolymerization of TIPs. This investigation would provide a novel route for promoting BCAs production by mild oxidative depolymerization of low-rank coals. [ABSTRACT FROM AUTHOR]

• Monitoring catalytic conversion of coal using mass spectrometry. • Single-heteroatom loss method well fits denitrogenation patterns. • Aromatic cores of compounds between 300 and 400 Da show similarity in ring size. The structure-reactivity relationship during catalytic reactions for coal has been extensively simulated by using model compounds. However, the direct study of structure-reactivity relationship is not sufficient for coal, the complex mixture, partially due to the challenging task of monitoring catalytic reactions in complex mixtures at the molecular level. In this study, a tandem mass spectrometry (MS) approach was designed for selective observation of catalytic single-atom denitrogenation and deoxygenation reactions of a coal. According to the tandem MS data, structure of aromatic cores, total carbon number in alkyl chains, heteroatom release efficiency and preference of heteroatom removal on aromatic cores versus alkyl chains were explored and compared to reveal the relationship between heteroatom release pattern and molecular structure. Structure-reactivity relationship was not clearly observed in deoxygenation patterns due to majorities of molecules contain multiple oxygen atoms. However, structure-reactivity relationships were revealed in denitrogenation patterns due to the presence of single nitrogen atom in most nitrogen-containing molecules. [ABSTRACT FROM AUTHOR]

The present environmentally-friendly coal processing technology discussed herewith focuses on the combined effect of ultrasonic and microwave energy in the extent of mineral matter (ash yield) removal from high-sulfur, low-quality coals for their clean utilization. The novelty of this study is that the technique is very efficient instead of using drastic chemicals with less treatment time, less amount of reagent in comparison to the conventional method, and has the potential to adopt in large-scale commercial production of cleaner coals. The quality of the cleaner coal products was examined by using chemical analysis and advanced analytical techniques (electron beam analysis). The combined irradiation process of ultrasonic and microwave energy is observed to be the most effective for the beneficiation of high-sulfur coal than the single process. The result showed a maximum of 51.28% and 66.34% ash (mineral matter) removal from the coal samples by microwave followed by an ultrasonic process. The X-ray photoelectron spectroscopy (XPS) analysis revealed that both inorganic and organic sulfur is present in these Cenozoic low-rank, high-sulfur Indian coals. The high resolution-transmission electron microscopy (HR-TEM) image analysis of the treated coal samples showed nearly agglomerated collections of nanomaterials; carbon spheres/flacks with an irregular shape; and the elements such as oxygen, iron, silicon, sulfur, and aluminum in the beneficiated coal samples. The major mineral phases, including quartz, kaolinite, and gypsum, are found to be removed during the beneficiation process. The thermal analysis (TGA-DTG) also showed the suitability of the beneficiated coals for the power plant application. ga1 • Ultrasound and microwave energy in removal of mineral matters from low-quality coal. • Thermal properties of such cleaner coals is improved. • Advanced level analytical characterizations of raw and cleaner coals are discussed. [ABSTRACT FROM AUTHOR]

In coal chemistry, thermal dissolution (TD) is an effective processing technique to obtain soluble components from coal by using organic solvents under a certain pressure and temperature. Exploring molecular structures of the TD extracts of low-rank coal is of great importance for eco-friendly and value-added utilization in chemical industry. To well elucidate the structural information of components in coal, higher-energy collisional dissociation (HCD) specific to Orbitrap mass spectrometry was applied to analyze four TD extracts of a subbituminous coal. Alkyl chains of aromatic compounds can be removed from aromatic cores during a HCD process, allowing determination of the distribution of heteroatoms in either aromatic cores or alkyl chains. Both double bond equivalent value and carbon number of precursor ions (whole molecules) and the corresponding fragment ions (aromatic cores) obtained via a HCD process were used to evaluate the relationship between aromatic cores and alkyl chains for compounds in coal. With the increase of molecular weight, compounds in coal exhibited different distributions for aromatic cores and alkyl chains. From 200 Da to 300 Da, the increase of carbon number mainly contributed to the formation of condensed aromatic cores. However, from 300 Da to 400 Da, it was attributed to the formation of both aromatic cores and alkyl chains. In addition, heteroatom distribution index indicated that a higher TD yield of heteroatom-containing compounds would be obtained via solvents with a smaller molecular size and nitrogen-containing aromatics would be enriched by using TD solvents containing aromatic ring. [ABSTRACT FROM AUTHOR]

Three low-rank coals were subjected to a thermal dissolution (TD) process sequentially using cyclohexane (CYH) and methanol (MeOH) solvent to obtain six TD extracts. The six TD extracts were analyzed by Fourier transform infrared spectroscopy (FTIR), gas chromatograph/mass spectrometry (GC/MS) and gas chromotography/quadrupole time-of-flight MS (GC/Q-TOF MS) to understand the compositional features of three low-rank coals. Hierarchical clustering analysis (HCA) and principle component analysis (PCA) were applied to show the relationships among 10 classes in the six TD extracts. Compared with GC/MS, a routine analytical method, more species with relative high molecular mass and more oxygen-containing organic compounds (OCOCs) were determined using GC/Q-TOF MS. In addition, HCA dendrogram and heatmap reveal the difference among 10 classes in the TD extracts. Meanwhile, the distributional and compositional features of six TD extracts were also exhibited in the score plot and loading plot of PCA. [ABSTRACT FROM AUTHOR]

Highlights • A method to evaluate the bias of three MS ionization methods was proposed for coal. • Elemental compositions obtained from ultimate analysis was set as a reference. • Elemental compositions derived from APCI-MS showed closer values to ultimate analysis. • Adjusted compound classes offer a closer measurement to the actual values. Abstract The relative abundances of compound classes (e.g. CHO 1 , CHO 2 and CHNO 1) in fossil fuels have been widely used in previous researches based on the data from mass spectrometry (MS). However, such observations are susceptible to the ionization bias of MS due to the variation of ionization efficiency, which may affect the downstream quantitative analysis. Many efforts have been devoted to investigating the ionization efficiencies of a variety of model compounds, but not complex and diverse mixtures. Therefore, it is necessary to investigate how quantitatively ionization bias affects the MS analysis of complex mixtures. In this study, ionization bias was preliminarily investigated by comparing the elemental compositions obtained from MS-analysis via different ionization methods with the data acquired by a standard elemental analyzer. A coal-derived liquid and mixtures of five model compounds were ionized by atmospheric-pressure chemical ionization (APCI), electrospray ionization or direct analysis in real-time, followed by analyzing using a high-resolution Orbitrap MS to obtain elemental compositions. MS-based results via APCI ion source showed the closest elemental compositions to those obtained from the elemental analyzer. For the MS-based analysis, the abundances of S- and O-containing compounds were significantly lower and that of N-containing compounds was clearly higher compared to ultimate analysis. The abundances of compound classes were adjusted to provide a closer approximation of the actual contents, which might better serve for the downstream quantitative analysis. Although absolute quantification still needs additional work, the adjusted MS-based analysis provides not only the molecular level data, but also a better quantification ability compared to previous analytical approaches. [ABSTRACT FROM AUTHOR]

Highlights • Fragmentation patterns of 22 model compounds with varied energies were discussed. • The optimal collision energy to investigate aromatic core structures should be 80 eV. • Energy-resolved ISCAD showed potential for in-depth structural analysis of coal/biomass. Abstract In-source collision activated dissociation (ISCAD) is an effective method to obtain molecular structure of coal and biomass and provide basic knowledge for coal/biomass conversion. Twenty two coal/biomass-based model compounds and one coal extract were studied via ISCAD to understand the relationship between collision energy and molecular structure and the application of ISCAD in the characterization of coal. Model compounds showed different fragmentation patterns with the increase of collision energy and the detailed fragmentation pathways in context of collision energies were proposed. According to the ISCAD results of coal extract, the weighted mean molecular weight (MW) and weighted mean double-bond equivalent (DBE) values of ionized coal molecules decreased over collision energy of 80 eV. The decrease of weighted mean MW and DBE were mainly caused by the cleavage of alkyl chains, bridged bonds, and minor cracking of small aromatic cores from precursor ions upon fragmentation. Therefore, the optimal ISCAD collision energy for the investigation of aromatic core structures of the coal extract should be around 80 eV. [ABSTRACT FROM AUTHOR]

• Functional groups are effective variables of machine learning for FTIR spectra. • OH is a key factor discriminating the samples because of deoxidation reactions. • Pre-integration of initial samples increases the classification effects of PCA. Three biomass (rice straw, rice husk and wheat straw) and three coal samples (lignite, subbituminous coal and bituminous coal) were extracted via a thermal dissolution (TD) process, and the TD extracts were treated by catalytic hydrogenation to obtain reaction products. To reveal the similarity in molecular information among the samples and elucidate their chemical reactivity, four machine learning algorithms were applied to analyze the Fourier transform infrared spectra of both TD extracts and catalytic hydrogenation products. Functional groups were used as variables and the difference in peak area can be treated as the basis for sample classification. Aromatic C H, C O C, aliphatic CH 2 or CH 3 and aromatic C O or C C bonds were the main characteristic variables in principal component analysis algorithm to classify biomass- and coal-derivated samples. These samples were also grouped into four clusters by hierarchical clustering analysis algorithm according to the similarity and difference in the distribution of functional groups. For artificial neural network algorithm, aliphatic C H and OH bonds are the most important variables to classify these samples into four groups, and aromatic C H, OH, and C O C groups are the main variables contributed to the classification trees in random forest algorithm. Machine learning algorithms will provide methodological guidance for the data mining of the spectra of complex organic systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mass spectrometry was used to underatand the molecular composition of carbon precursors. • Reveal the relationships between composition of precursor and performance of supercapacitors. • N- and O-containing compounds can improve the conductive and capacitance of carbon materials. In this work, soluble portions obtained from the co-thermal dissolution (CTD) of rice husk (RH) and coal were used as the carbon precursor for the synthesis of 3D hierarchical porous carbons (HPCs). The electrochemical properties of HPCs were tested in supercapacitors as working electrode. HPC-RH 3/1 showed a specific capacitance of 352 F/g at 1 A/g and a retention rate of 100% after 10,000 cycles. The composition of the carbon precursors is a key factor determining the characteristics of carbon-based materials. The detailed composition of carbon precursors was obtained by gas chromatography/mass spectrometry (GC/MS) and Orbitrap MS. The N-containing organic matters in carbon precursors can improve conductivity and the O-containing compounds can contribute to pseudocapacitance. According to the MS analysis, the high content of compounds with unsaturated structures was of benefit to excellent electrochemical properties. The study on the relationships between molecular compositions of carbon precursors and electrochemical characteristics can give a direction of selection and optimization of carbon precursors, which further improve the electrochemical performance of carbon materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy-resolved HCD fragmentation of coal-related model compounds was studied. • Fragmentation pathways and de-alkylation behaviors were explored. • Relationship between fragment structure and collision energy was established. To provide basic knowledge for coal conversion, twenty one coal-related model compounds (MCs) were analyzed using a tandem Orbitrap mass spectrometer (MS). Higher-energy collisional dissociation (HCD), a method of Orbitrap MS, unraveled the detailed fragmentation pathways and de-alkylation behaviors of the ionized MCs under collision energies from 10 to 80 eV. Chemical bond breaking, hydrogen loss, rearrangement reaction, and elimination of neutral fragments were discussed to elucidate clear fragmentation pathways. For arenes without alkyl chains, a higher energy threshold of fragmentation was observed with the increasing of aromatic ring due to a higher conjugate effect of condensed aromatic structure. The existence of alkyl chains decreased the threshold of fragmentation because of the electron-donating effect of alkyl chains. Heteroatom-containing aromatic compounds, a series of important species in coal, showed a diversified fragmentation patterns due to a low bond dissociation energy and a weak conjugate effect compared with arenes. Fragmentation pathways and de-alkylation behaviors of coal-related MCs will contribute to building monitoring methods for coal and its derivatives conversions in chemical industry. [ABSTRACT FROM AUTHOR]

• Structure parameters, δ and B, of 19 coals are calculated via simplified formulas. • Coals in the liquefaction zone exhibit high conversion rates and oil yields. • Coal structure-chemical index effectively predict the performance of liquefaction. As a semi-theoretical and semi-empirical method, structure-chemical index has classified the utilization of coals with different coalification degrees and petrographic constituents in Russia. In this work, the formulas of structure-chemical index were simplified to building methodology for evaluating the utilization of coals in direct coal liquefaction (DCL). Nineteen coals from Xinjiang, China, were characterized by ultimate analysis and thermal gravimetric analysis, and the corresponding DCL products were evaluated. After the calculation of structure-chemical index, 12 coals fall into the liquefaction zone, and exhibit higher H/C ratios and faster pyrolysis rates, which are helpful to coal liquefaction reaction. Therefore, the conversion rates and oil yields are more than 85.0% and 65.0%, respectively, for coals in the liquefaction zone, and less than 80.0% and 50.0% for coals out of the zone. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spectral stitching improves the detection ability towards minor and trace species. • Comprehensive molecular information and transfer behavior of O and N atoms are revealed. • Similarity and difference of samples are visually exhibited in PCA and HCA plots. The combination of mass spectrometry (MS) data and chemometrics methods is conducive to obtaining more comprehensive molecular information and evaluating the transfer behavior of O and N atoms during the conversion of biomass and coal. In this work, 12 thermal dissolution (TD) extracts of coal/biomass samples and the catalytic hydrogenation products of TD extracts were analyzed by Orbitrap MS using spectral stitching and in-source collision-activated dissociation (ISCAD) methods. Spectral stitching improves the detection ability towards minor and trace species, enhancing the number of identified compounds by two times. Meanwhile, ISCAD provides more comprehensive molecular structure information, which can illustrate the transfer patterns of heteroatoms and deepen the understanding of the structural characteristics of aromatic rings during the conversion of biomass and coal. Two chemometrics methods, principal component analysis (PCA) and hierarchical cluster analysis (HCA), were introduced to dig out the detailed similarities and differences between O-containing and N-containing compounds in coal and biomass. HCA method not only recognized the category of O-containing and N-containing compounds in each sample, but also showed the removal behavior of O and N atoms in biomass and coal. Thus, the combination of MS methods and chemometrics method is expected to provide methodological support to elucidate the molecular structure and conversion pathways for complex coal and biomass. [ABSTRACT FROM AUTHOR]

• Isometric NMP and IL mixture was used as solvent to swell Hefeng subbituminous coal. • Hefeng subbituminous coal was swelled by three enhancement methods. • Fractal dimension and pyrolysis kinetic parameter of the swelled coal were calculated. • Yields of solid, liquid and gas of pyrolysis product of the swelled coal were showed. Hefeng subbituminous coal (HSBC) was swelled with different enhancement method, including mechanical activation (THSBC 2), ultrasonic radiation (THSBC 3) and microwave radiation (THSBC 4), with isometric N-methylpyrrolidone (NMP) and 1-ethyl-3-methylimidazole acetate (IL) mixture as the solvent (the un-enhancement coal was marked as THSBC 1). Pore structure and pyrolysis performance of each sample were discussed. Results showed that the five samples presented abundant micropores, mesopores and some macropores from N 2 adsorption-desorption profiles. In lower P/P 0 range, the pore type was mainly semi-open pore closed at one end that did not affect the hysteresis loop of the samples; in higher P/P 0 range, the pore types were mainly open pore (including cylindrical pore with two open ends and parallel plate pore with four open sides), ink-bottle pore and semi-open pore closed at one end. Hysteresis loops of THSBC 3 and THSBC 4 were similar to THSBC 1 , and the pore types were similar to some extent. The hysteresis loop in higher P/P 0 range of THSBC 2 was not obvious, indicating that there were more semi-open pores closed at one end (with no ink-bottle pore). Pore structure and pyrolysis kinetics of each sample were investigated, and fractal dimension and kinetic parameter were calculated by Frenkel-Halsey-Hill model and Coats-Redfern model, respectively. Results demonstrated that the fractal dimensions D 1 (related to surface roughness) and D 2 (related to complexity of inner pore structure) were closely related to the pore structure. Compared to THSBC 1 , the value of D 1 is larger for THSBC 2 , presenting more obvious surface roughness. While the complexity of the pore structure of the five samples is little different, showing very close D 2. In addition, the change of pyrolysis activation energy was more obvious for the sample of THSBC 2 (29.027 kJ∙mol−1), 4.75% less than THSBC 1 (30.482 kJ∙mol−1), which might be attributed to the violent collision process caused by mechanical activation. HSBC presents higher solid yield during pyrolysis, up to 64%, and the solid yield of others samples is around 60%. Compared with HSBC, the gas yields of other four samples have little change, while the liquid yields are increased, indicating that the swelling treatment can promote the formation of tar. [ABSTRACT FROM AUTHOR]

Two Chinese coals, Shengli lignite and Shenmu–Fugu subbituminous coal, were subjected to non-catalytic hydroconversion (NCHC) and catalytic hydroconversion (CHC) in cyclohexane at 300 °C for 3 h under pressurized hydrogen using a solid acid as the catalyst, which was prepared by impregnating isometric pentachloroantimony and trimethylsilyl trifluoromethanesulfonate into an activated carbon. The reaction mixtures from both NCHC and CHC were sequentially extracted with petroleum ether, carbon disulfide, methanol, acetone, and isometric acetone/carbon disulfide mixed solvent to afford extracts 1–5 (E 1 –E 5 ). The results show that both E 1 and total extract yields from CHC are appreciably higher than those from NCHC of each coal. E 1 from either NCHC or CHC of each coal was analyzed with a gas chromatograph/mass spectrometer (GC/MS) and an atmospheric solids analysis probe/time of flight mass spectrometer (ASAP/TOF-MS). GC/MS analysis shows that each E 1 consists of alkanes, arenes, and oxygen-containing organic compounds (OCOCs), and most of the arenes are methyl-substituted ones, whereas alkenyl groups only appear on benzene ring; most of the OCOCs are arenols, especially alkylarenols. According to ASAP/TOF-MS analysis, organic compounds with molecular masses ranging from 500 to 950 u appear in E 1 from CHC of both coals. [ABSTRACT FROM AUTHOR]

Highlights: [•] [M+H]+ to M+• ratio is positively related to Sr value for the three arenes used. [•] The fragmentation pathways for BCRMCs in ASAP were proposed. [•] RMDNM, WSPchar and MEWSPTBC were directly and rapidly analyzed by ASAP/TOF-MS. [Copyright &y& Elsevier]

• Solid superacid catalysts with different supports were prepared for direct coal liquefaction. • TFMSA/ZrO 2 presented high catalytic activity for direct coal liquefaction. Highly active, recyclable, and reusable supported super-acid catalyst is of great significance for improving coal liquefaction performance and liquefaction conditions and realizing comprehensive utilization of coal resources. Solid super-acid catalysts were prepared by impregnation method with trifluoromethanesulfonic acid (TFMSA) supported on different carriers (ZrO 2 , Al 2 O 3 , SiO 2 , and ZSM-5). Hefeng sub-bituminous coal (HFSB) was used as raw material to investigate the liquefaction effect of the catalysts. Composition, structure, acidity property of the catalysts were analyzed by EDS, XRD, and NH 3 -TPD methods, and direct coal liquefaction performance of the catalysts was performed, and TG-DTG characterization was used to evaluate the pyrolysis behavior of the liquefaction residue. Results showed that activity of the four supported solid super-acid catalysts was followed by TFMSA/ZrO 2 , TFMSA/ZSM-5, TFMSA/Al 2 O 3 , and TFMSA/SiO 2 , with coal conversions of 84.20 %, 78.40 %, 76.67 % and 73.23 %, and oil yields of 67.16 %, 62.53 %, 61.15 %, and 58.41 %, respectively. The Coast-Redfern method was used to analyze the pyrolysis kinetics of the four coal liquefaction residues (R-ZrO 2 , R-ZSM-5, R-Al 2 O 3 , and R-SiO 2). Results presented that, in low temperature range (200−530 ℃), except R-SiO 2 , the pyrolysis process of residues conforms to the third-order reaction. And in high temperature range (530−850 ℃), the four-order reaction is more suitable for the four residues. The pyrolysis activation energy of R-ZrO 2 is lower at low temperature region (16.822 kJ/mol), while R-Al 2 O 3 presents lower activation energy at high temperature range (45.494 kJ/ mol). [ABSTRACT FROM AUTHOR]

• FT-ICR MS provided big data of compounds in coal due to ultrahigh resolving power. • PCA and HCA clustered extracts according to pretreatment and solvent polarity. • H 2 O 2 pretreatment inhibited generation of Cl-containing species for NaClO oxidation. Shengli lignite, a low-rank coal, was pretreated and oxidized with aqueous H 2 O 2 and NaClO, respectively, to obtain an oxidation product. Both pretreated and un-pretreated oxidation products were sequentially extracted with diethyl ether and ethyl acetate to acquire extracts. A Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) coupled with an electrospray ion source was used to analyze the extracts to obtain MS big data about molecular distribution of organic matter. Two chemometrics methods, principal component analysis and hierarchical clustering analysis were applied to cluster the extracts according to the similarities and differences in molecular characteristics. The results showed that the polarity of solvent affected the compositional distribution of extracts and the most compounds in the extracts belonged to ONSCl, ONS, ONCl and ON classes. The pretreatment using H 2 O 2 promoted the generation of species from O and ON classes and inhibited the generation of Cl-containing compounds for the following NaClO oxidation process. [ABSTRACT FROM AUTHOR]

• PCA and HCA were used to mine effective information from molecules in coals. • ISCAD was proven an effective approach for the determination of heteroatom distribution. • The details in molecular structure of four low-rank coals were revealed. Four low-rank coals, Zhaotong lignite, Dayan lignite, Wucaiwan sub-bituminous coal and Shenfu sub-bituminous coal were sequentially dissolved in cyclohexane, acetone and methanol at 300 °C. An Orbitrap mass spectrometry coupled with an atmospheric pressure chemical ionization ion source was used to analyze the 12 thermal dissolution (TD) extracts from coals to obtain and compare the molecular distribution of soluble organic matter. Two statistical methods, principal component analysis and hierarchical clustering analysis, were used to mine the effective information from a large number of mass spectral data. The statistical results showed that the degree of coalification had greater effects on the structure and composition of TD extracts compared to the solvent. In-source collision-activated dissociation further elucidated the characteristics of molecular structure and revealed that most of O atoms distribute on alky chains. [ABSTRACT FROM AUTHOR]

• Ni-Mg 2 Si/AP is active for catalyzing AR hydrogenation and >C ar O cleavage. • Oxydibenzene was completely converted to cyclohexane at 150oC. • Oxydibenzene conversion is 91.2 % over Ni-Mg 2 Si/AP even recycled 4 times. Ni-Mg 2 Si/attapulgite powder (AP) was prepared by thermally decomposing nickel tetracarbonyl onto the as-synthesized Mg 2 Si/AP by impregnating Mg 2 Si onto AP in CCl 4. Its catalytic performance was evaluated by the catalytic hydroconversion (CHC) of oxydibenzene (ODB) in n -hexane under different reaction conditions. Both ODB conversion and cyclohexane selectivity are 100 % by the CHC of ODB over Ni-Mg 2 Si/AP under 3 MPa of initial hydrogen pressure at 240 °C for 4 h. However, almost no ODB was converted without Ni-Mg 2 Si/AP under the same conditions. The results show that Ni-Mg 2 Si/AP could activate H 2 to biatomic active hydrogen (H⋯H) and H−, resulting in the hydrogenation of aromatic rings (ARs) and the hydrocracking of >C ar O bridged bonds (COBBs), respectively. Additionally, the catalyst was also successfully applied in the CHC of extraction residue (ER) from Piliqing subbituminous coal (PSBC) in n -hexane. The group components of the soluble portion (SP) from CHC and non-CHC (NCHC) (SP CHC and SP NCHC) of ER were analyzed with a gas chromatograph/mass spectrometer. The yield (36.4 %) of SP CHC is significantly higher than that (1.8 %) of SP NCHC. More alkyl-substituted arenols (ASAs), anisoles, and methoxy-substitued cresols exist in SP NCHC , while SP CHC contains more normal alkanes (NAs), non-substituted cycloalkanes, alkylcyclohexanes, tetralins, and octahydroanthracenes. NAs are predominant in SP CHC , while ASAs are the most abundant in SP NCHC , indicating that the CHC facilitates the hydrocracking COBBs and hydrogenating ARs. ODB conversion is as high as 91.2 % after recycling 4 times. Therefore, the catalyst might be potential to produce coal-derived chemicals and clean liquid fuels to facilitate coal efficient conversions owing to its high activity, difunctionality, stability, and good recyclability. [ABSTRACT FROM AUTHOR]