Huolinguole lignite was sequentially extracted with carbon disulfide, ethyl acetate, methanol and acetone. All of the extracts were analyzed using a time-of-flight-mass spectrometry (TOF-MS) equipped with an atmospheric pressure photoionization (APPI) ion source. Toluene or 1,4-difluorobenzene was chosen as dopant for APPI. The results indicated that both dopants could well ionize compounds which cannot be ionized by APPI without dopant. Toluene induced higher ionization efficiency than 1,4-difluorobenzene. Some compounds in the extracts were identified as dimers, which might be formed via molecular association. Heteroatoms were identified in all of the associated molecules. Molecular weight distributions under three APPI ionization modes were similar. Compounds with molecular weight from 200 Da to 500 Da occupied 60% of all the products and around 10% of the products had molecular weight over 500 Da.Complex molecules in coal (as shown on the left of the figure) were analyzed by atmospheric pressure photoionization mass spectrometry (APPI-MS) with the introduction of a commonly used dopant, toluene, or a new dopant, 1,4-difluorobenzene.Download high-res image (77KB)Download full-size image

Humic acids obtained from a Chinese lignite via alkali treatment were analyzed using Fourier transform infrared spectroscopy and Orbitrap mass spectrometry coupled with an electrospray ion source (ESI-Orbitrap-MS). Raw coal and the corresponding residue were characterized via scanning electron microscopy and energy dispersive spectrometry. Over 4700 heteroatom-containing compounds with wide distributions of molecular mass and unsaturation degree were detected via the ESI-Orbitrap-MS, and around 60 percent of the detected species were found to be oxygen-containing compounds. In addition, van Krevelen diagram and double-bond equivalent (DBE) plot were introduced to provide more structural details of the compounds. For the species only containing C, H, and O (HACHO), condensed aromatic compounds with a DBE value over 20 only contained 1 or 2 oxygen atoms. Carboxyl- and hydroxyl-containing aliphatic compounds (CHCACs) were predominant in HACHO with 5 or 6 oxygen atoms. Both the CHCACs and aromatic carboxylic acids or phenols were grouped into clusters in the van Krevelen diagram to be recognized. The introduction of a nitrogen atom to the HACHO species was based on the structures of the HACHO species, which is also indicated by the van Krevelen diagram.

•Two organic fluorines were identified in a Chinese anthracite using mass spectrometry.•Fingerprint of heteroatom-containing compounds was characterized.•Higher polarity of acetone at supercritical state may induce a higher degree of decomposition of the anthracite.

Glycerol, a liquid matrix material for matrix-assisted laser desorption ionization mass spectrometry, was irradiated by a tunable pulsed infrared laser at wavelengths of 2.80 μ.m, 2.94 μ.m, 3.10 μ.m and 3.50 μ.m, covering the OH and CH stretch vibrations. A fast photography system was introduced to analyze the dynamic process of plume propagation induced by laser ablation up to 1000 μ.s of the delay time. Propagation distance of the plume front was measured and the corresponding velocities were calculated; they varied with the wavelength and decreased with the delay time. At the tunable wavelength of the peak of the OH absorption (3.0 μ.m), theoretical calculations indicate that energy deposition from the pulsed laser is in the regime of stress confinement. The mode of energy deposition depends on the wavelength of the OH vibration and its distance from the absorption maxima. However, stages after a 10 μ.s delay at various wavelengths show a certain similarity in the distance of plume propagation, which can be well fitted by a drag model.

•GC/MS characterized molecules with low molecular weight and polarity.•ESI was proven an effective approach for the ionization of polar species over 500 u.•DART-MS speeded up the analysis and broadened the measurement range.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 OxN5, and OxN6 classes were only detected by DART-MS.

•Rapid and accurate characterization of bio-oil was carried out using ASAP-TOF-MS.•Ambient ionization well analyzed bio-oil with viscosity and heterogeneity.•Compounds that are not revealed by GC/MS were well characterized.•Difference of DBE distribution for bio-oil was obtained according to solvent polarity.Bio-oil from pyrolysis of rice husk (RHBO) was investigated using a time-of-flight mass spectrometer equipped with an atmospheric solids analysis probe ion source to afford rapid and accurate characterization of molecular information. RHBO was sequentially extracted with n-hexane, tetrachloromethane, benzene, dichloromethane, trichloromethane and ethyl acetate in order of increasing solvent polarity to acquire extracts E1 to E6. Heteroatomic species, especially oxygen-containing compounds, in the extracts were well characterized and statistically compared. Solvents with low polarity inclined to extract species with relative low molecular mass and low polarity from RHBO. There were amounts of lignin monomers identified in the extracts and most of them contained 1 ∼ 4 oxygen atoms, which was consistent with the acidity of bio-oil due to the existence of phenolic OH inside. Species with molecular mass over 500 Da were detected with around 5% of relative content, which could not be revealed by other analytical methods such as gas chromatography/mass spectrometry.

•Two-thirds of identified species in the coal tar using GC/MS were hydrocarbons.•In-situ analysis of heteroatomic species in the coal tar was realized by ASAP-MS.•Orbitrap MS highly extended the measurement range in both mass weight and degree of unsaturation.A high-temperature coal tar (HTCT) was extracted by petroleum ether (PE) and the extract (denoted by PE-HTCT) was characterized using three mass spectrometers to obtain and compare molecular compositional information. Gas chromatography/mass spectrometry detected molecules with low molecular weight and polarity such as hydrocarbons. A time-of-flight MS coupled with an atmospheric solids analysis probe ion source realized rapid and in-situ analysis of compounds with mid-polarity in PE-HTCT without sample pretreatment. An electrospray ionization (ESI) Orbitrap MS was used to characterize heteroatom-containing compounds in PE-HTCT. Most heteroatomic species identified by ESI-Orbitrap MS contained oxygen, nitrogen, or both atoms, and the total percentage of both Oo and Nn species was approximate 13%. Ketene and furan derivatives were identified in Oo class, as well as aliphatic amine compounds, azoles, aniline and pyridine derivatives for Nn class. The combination of three mass spectrometers gave a detailed characterization of coal tar and provided a full view of the corresponding constituents.

Microstructure, interfacial resistance, and activation energy for composite cathodes consisting of 50 wt% (La0.85Sr0.15)0.9MnO3-δ (LSM) and 50 wt% Sm0.2Ce0.8O1.90 (SDC) were studied for intermediate-temperature solid oxide fuel cells based on SDC electrolytes. Microstructure and interfacial resistance were greatly influenced by the characteristics of starting powder and temperatures sintering the electrodes. Optimum sintering temperatures were 1100 and 950 °C, respectively, for electrodes with SDC prepared using oxalate coprecipitation technique (OCP) and glycine-nitrate process (GNP). Area-specific resistances determined using impedance spectroscopy were 0.47 and 0.92 Ω cm2 at 800 °C for LSM-SDC/OCP and LSM-SDC/GNP, respectively. The high electrochemical performance is attributed to small grain size, high porosity, and high in-plane electrical conductivity of composite cathode, demonstrating the dramatic effects of microstructure on electrode performance. To increase the electrode performance, it is critical to enhance the diffusion rate of oxygen species.

Zhundong subbituminous coal pretreated with aqueous H2O2 was oxidized by aqueous NaOCl and sequentially extracted with diethyl ether (DEE) and ethyl acetate (EA) to afford DEE- and EA-extractable fractions and residue. Both extracts were esterified with CH2N2 and analyzed using high performance liquid Chromatography/mass spectrometry equipped with electrospray ionization (ESI) or atmospheric pressure photoionization (APPI) ion source. Molecular mass of 60% compounds in the esterified extracts ranged between 200 and 600 Da and more than 20% of the esterified extracts had molecular mass over 600 Da. Toluene and toluene/anisole (vol./vol. = 95/5) were used as dopants for APPI. Low- and non-polar compounds in the esterified extracts were well analyzed using APPI/MS. Compared to toluene/anisole mixture, toluene greatly increased ionization efficiency of APPI. More molecular associations were detected by ESI than by APPI. Heteroatoms were identified in most of the associated species.•APPI was used to analyze esterified extracts from the oxidation of a Chinese coal.•Adding toluene as dopant the greatly increased ionization efficiency of APPI•More dimers with heteroatoms were identified with ESI/MS than with APPI/MS.

•ASAP was applied to analyze CRMCs, exploring a new application field.•The ionization mechanism of produced M+ and [M+H]+ for CRMCs were investigated.•The ASAP/MS fragmentation pathways for selected CRMCs were proposed.An atmospheric pressure solids analysis probe (ASAP) was mounted on a commercial atmospheric pressure chemical ionization source with simple modifications. A series of coal-related model compounds (CRMCs) were analyzed using a time-of-flight mass spectrometry equipped with the ASAP ion source. The ionization mechanism and fragmentation pathways for CRMCs were investigated. The temperature of desolvation gas played a crucial role to the response signal, especially for the association behavior of CRMCs. With a fixed desolvation gas temperature, radical cation (M+) or protonated molecule ([M+H]+) was the predominant ion generated by corona discharge of ASAP depending on the temperature of drying gas. Fragment ions were produced from bridged bond breaking of the precursor ions, rearrangement reactions and loss of neutral fragments such as H2O, CH2O, CO, CH3OH and CO2. The fragmentation pathways can offer a better understanding of fundamental mechanism of chemical bond breaking for coal derivatives and further explore the application of coal directional conversion.