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To investigate the molecular composition of soluble organic species in Baiyinhua lignite (BL) and their evolution profiles during pyrolysis, BL was firstly pyrolyzed in a fixed-bed reactor, affording gaseous products, tars and chars, then BL and its chars were thermally dissolved in supercritical methanol affording soluble portions (SPs). The composition and structural characteristics of the SPs and tars were analyzed with a gas chromatograph/mass spectrometer. The results indicate that most of the soluble organic species can be released from BL below 500 °C during pyrolysis. Abundant soluble long-chain aliphatic hydrocarbons and carboxylic acids wrap around the aromatic nucleus in BL. According to the difference between the composition and structural characteristics of the SPs and tars, the evolution profiles of the soluble organic species from BL pyrolysis were discussed in detail. [ABSTRACT FROM AUTHOR]

In this paper, two typical Chinese lignites, Shengli lignite (SL) and Xiaolongtan lignite (XL), with different geologic ages were firstly thermal dissolved in sub- and supercritical benzene and ethanol, then soluble organic species were analyzed with Fourier transform infrared spectroscopy (FTIR), gas chromatograph/mass spectrometer (GC/MS) and atmospheric solids analysis probe/time of flight mass spectrometer (ASAP/TOF-MS). The soluble organic species yield of XL in benzene is close to that of SL in the temperature investigated, whereas the soluble organic species yield of XL in ethanol is obviously higher than that of SL at high temperature region. Obvious difference exists in the molecular composition of the soluble organic species between SL and XL. The soluble organic species of XL contain more free aliphatics but less arenes than those of SL. The arenes in the soluble organic species of XL are mainly composed of the derivatives of benzene and naphthalene, while those from SL are dominated with condensed arenes and polycyclic biphenyls. Furthermore, the free oxygen-containing organic species in SL and XL are dominated with ketones and phenols, respectively. Additionally, ASAP/TOF-MS analysis indicates that the molecular weight of soluble organic species from SL is higher than that from XL. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe/NC catalyst shows good activity and stability for cleaving C-O bonds in lignite. • Fe-N and Fe/Fe 3 C species in the catalyst were crucial to the catalytic activity. • Active hydrogen species were hydrogen radicals generated from H 2 and isopropanol. • The hydrocracking products have higher H/C ratio and heating values than lignite. • Catalytic hydrocracking promoted producing phenols via the cleavage of C-O bonds. Cleaving C-O bridged bonds of lignite via catalytic hydrocracking (CHC) is an effective method to produce chemicals and clean fuels. Herein, a nitrogen-doped carbon supported Fe catalyst was developed by using a one-pot method for CHC of Xilinguole lignite (XL) and its related model compounds. The doped nitrogen enhanced the interaction between Fe and N species to form Fe-N sites and favored forming smaller Fe/Fe 3 C nanocrystals, which played a crucial role in CHC performance. Toluene and phenol were produced from CHC of benzyl phenyl ether (BPE) with high yield and selectivity at 250 °C over the optimal catalyst with 4% Fe, without hydrogenation products. The Fe-based catalyst activated both H 2 and isopropanol to generate hydrogen radicals for cleaving C-O bridged bonds. The CHC of XL under different temperature and time showed that the yields of oil, asphaltene and preasphaltene were obviously promoted under 325 °C, 1 MPa, and 6 h, and they had much higher H/C ratio but remarkably lower O/C ratio, resulting in much higher heating values (28.19–36.90 MJ/kg) than XL. Phenols were the major group component with relative content of 53.6 wt% in oil from CHC, and the asphaltene and preasphaltene from CHC had obviously lower molecular weights, which could attributed to depolymerization of C-O bridged bonds in the XL macromolecular structures over the catalyst. [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]

Thermal dissolution (TD) plays an important role in obtaining soluble components from low-rank coals. Characterization of the TD product is essential for both optimization of TD conditions and in-depth understanding of molecular structures in coal that is crucial for the refining processes. In-source collision-activated dissociation (ISCAD) combined with high-resolution mass spectrometry (MS) was employed in this study to analyze four TD products of a low-rank coal obtained by using cyclohexane, acetone, methanol and ethanol as solvents. ISCAD-MS allows the evaluation of distributions of oxygen and nitrogen atoms located within aromatic cores or on alkyl chains based on the abundances of heteroatom-containing precursor ions and fragment ions. In addition, ISCAD-MS can evaluate the abundance of multi-core compounds based on the change of average double bond equivalent value upon fragmentation. These structural details advance the current understanding of the TD products at the molecular level. [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]

Detailed characterization of organic components in low-rank coals is essential for the utilization of coals in clean, effective and value-added ways. Two kinds of low-rank coals were subjected to sequential thermal dissolution in the order of cyclohexane, acetone, and methanol to obtain six soluble portions (SPs) from the coals. Two gas chromatographic systems, gas chromatography/mass spectrometry (GC/MS) and comprehensive two dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOF MS), were applied to the characterization of the SPs. Compared to GC/MS, a routine analytical technique for complex mixtures, GC × GC/TOF MS improves the separating power, overcomes the co-elution, and reveals more structural details in complex mixtures like coals. Low-polar compounds like aliphatic hydrocarbons and arenes tended to be extracted by cyclohexane. High content of polar alcohols and phenols were identified in the SPs of methanol. Acetone could enrich nitrogen-containing organic compounds (NCOCs) due to hydrogen bond of N–H⋯O between NCOCs and acetone. Additionally, a series of low-concentration species including some isomers in the SPs were only identified by GC × GC/TOF MS. Distributions of various classes of compounds on the two-dimensional total ion chromatograms plot were discussed according to the separation mechanism of the two columns. Detailed analysis of biomarkers was also exhibited and discussed. [ABSTRACT FROM AUTHOR]

Lignite is rich in oxygen-containing species (OCSs) and able to load Ni via ion exchange to prepare Ni/C catalyst. However, the OCSs usually exists in the form of organic salts, which can reduce the capacity of Ni ion exchange. In this paper, Shengli lignite (SL) was treated with HCl and HCl/HF to selectively remove the organic salts and insoluble minerals, respectively, and the modified lignite was oxidized by H 2 O 2 to further increase the carboxyl content. The treated lignite was used to prepare Ni/C catalyst and the activity for biomass volatile reforming was evaluated. The results show that demineralization (DM) caused the corrosion of pore structure of SL and gave a Ni/C catalyst with a low specific surface area (SSA) of 222.1 m 2 /g. Oxidation with H 2 O 2 further destroyed the structure of DMSL and provided a Ni/C with the lowest SSA of 141.1 m 2 /g. Acid wash (AW) with HCl resulted in the increase of ion exchange capacity of SL and gave a Ni/C catalyst with larger SSA, higher loading, lower particle size and well dispersion of Ni particle in comparison with SL and DMSL. H 2 O 2 treatment of AWSL significantly increased the amount of carboxyl group to 3.8 mmol/g and gave a Ni/C with the largest SSA of 291.1 m 2 /g, highest Ni loading of 17.3% and smallest Ni crystallite size of 3.4 nm, as well as most active for corncob volatile reforming. [ABSTRACT FROM AUTHOR]

Shengli lignite (SL) was oxidized and depolymerized in aqueous sodium hypochlorite under mild conditions followed by sequential extraction with ethoxyethane and ethyl acetate. The extracts were analyzed by Fourier transform infrared spectroscopy, gas chromatograph/mass spectrometry (GC/MS), time-of-flight mass spectrometry (TOF-MS) equipped with electrospray ionization (ESI), and direct analysis in real time (DART) to understand the structural features of SL. In total, 130, 272, and 818 compounds were identified by GC/MS, ESI-MS, and DART-MS, respectively, and the corresponding molecular mass distributions are between 70 and 322, 114 and 664, 113 and 753 u , respectively. GC/MS detected molecules with low molecular mass and polarity, and the major species include aliphatic acids, benzene polycarboxylic acids, chloro-substituted species and nitrogen-containing compounds. A large number of heteroatom-containing compounds (oxygen, nitrogen and sulfur) with relatively high molecular mass and unsaturation degree were determined using ESI-MS. As an ambient ionization technique, DART speeded up the analysis time with little or no sample pretreatment. Compared to the other two MS techniques, DART-MS broadened the measurement range, and O x N 5 , and O x N 6 classes were only detected by DART-MS. [ABSTRACT FROM AUTHOR]

Highlights: [•] LRMC alkanolysis includes nucleophilic attack, hydrogen transfer and bond cleavage. [•] Reactivities of the LRMCs toward alkanolysis are: BOB>anisole>PEB>ODB. [•] For the same LRMC, ethanolysis proceeds much easier than methanolysis. [Copyright &y& Elsevier]

Highlights: [•] SL was pretreated with H2O2 and then oxidized in NaOCl aqueous solution. [•] The pretreatment significantly increased the yields of soluble species. [•] The pretreatment enhanced the formation of compounds with m/z 300 to 500. [•] The formation of chloro-substituted alkanoic acids was inhibited by the pretreatment. [•] Increase in yields of soluble species is ascribed to introduction of −COOH and −OH. [Copyright &y& Elsevier]

Abstract: Structural features of Shengli lignite (SL) were investigated through ruthenium ion-catalyzed oxidation and oxidations in aqueous hydrogen peroxide (AHPO) and sodium hypochlorite (ASHC) under mild conditions. The results suggest that SL is rich in condensed aromatic species and hydroxyl-, methoxy-, and/or methyl-substituted benzene rings, and –CH2CH2– is a dominant bridged linkage connecting aromatic rings in SL. Aliphatic linkages connecting three aromatic rings also exist in SL. Most of the organic matter in SL was converted into soluble fractions in either AHPO or ASHC. The products from SL oxidation in AHPO are rich in hydroxyl- and/or methoxyl-substituted benzoic acids, alkanoic acids (AAs), and long-chain alkanedioic acids (ADAs), whereas those from SL oxidation in ASHC are mainly composed of benzene carboxylic acids, chloro-substituted short-chain AAs and ADAs. The nitrogen- or sulfur-containing species produced from SL oxidation provide important information on structural features of organic nitrogen and sulfur species in SL. [Copyright &y& Elsevier]

[Display omitted] • Synthetic hollow ZSM-5 (HSZ5) possess higher selectivity for toluene and m/p-xylene. • None-modifier catalysts keep high stability after 7 cycle reactions. • 11HSZ5 exhibits hierarchical meso -microporesity to rich BTEXN at 600 °C. • xHSZ5 show low coke resistance during lignite pyrolysis. Light aromatics could be produced by catalytic fast pyrolysis (CFP) of lignite over HZSM-5 with shape selectivity and accessible active sites. However, the catalytic reactivity in the center crystal has not been fully exploited. In this work, the different hollow hierarchical porosity-tunable ZSM-5 were synthesized using polyethylene glycol as a soft template by a steam-assisted crystallization process. Compared with commercial HZSM-5, the synthesized HZSM-5 exhibited higher selectivity for alkylbenzene (toluene and m/p-xylene) with the yield of 9.91 mg/g (7.31 mg/g over commercial HZSM-5). The hollow HZSM-5 with pore-size fine-tuning were favorable to control the tiny different intermediates for shape-selective of benzene and alkylbenzene in CFP. In addition, the unmodified synthetic hollow catalysts also kept highly stability after seven cycle experiments due to the enhancement of molecules diffusion in crystal center, especially the alkylbenzene yield was sustained at approximately 7.38 mg/g during cycle experiments. The work provides a great prospect to promote the formation of alkyl aromatics in CFP. [ABSTRACT FROM AUTHOR]

• Sulfated HZSM-5 zeolite was prepared by dealumination, realumination and sulfation. • The introduced extra-framework Al affected the textural-acid properties of catalysts. • Sulfation of catalyst after re-introduced extra-framework Al enhanced LAs production. • The highest LAs and lowest coke yield were produced over SO 4 2−/DHZ5-A. Sulfated HZSM-5 zeolite prepared by dealumination, realumination and sulfation was used as the active mesoporous materials to promote the formation of light aromatics during catalytic reforming of volatiles from Shengli lignite pyrolysis. The results show that HCl-dealumination significantly increased the total pore volume (especially mesopores) and average pore size while reducing acid strength and amount of acid sites. The incorporation of the extra-framework Al species to HZSM-5 combined with SO 4 2− to form superacidic surface sulfate complex exhibited an increase in the yield of light aromatics and a decrease in the yield of coke in comparison with that of original HZSM-5. Among the modified catalysts, SO 4 2−/DHZ5-A (introduced the calcined Al 2 O 3 after HCl-dealumination and modified with (NH 4) 2 SO 4) with the acidity enhancement by sulfation obtained the maximum light aromatics yield of 27.3 mg/g and the lowest coke yield of 2.7%. The relationship between the physic-chemical properties of catalysts and the product distribution was proposed to understand the formation of light aromatics. [ABSTRACT FROM AUTHOR]