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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]

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]

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]