Chemical Structural Parameters Research Articles

Prediction of the First-Pass Metabolism of a Drug After Oral Intake Based on Structural Parameters and Physicochemical Properties.

The oral first-pass metabolism is a crucial factor that plays a key role in a drug's pharmacokinetic profile. Prediction of the oral first-pass metabolism based on chemical structural parameters can be useful in the drug-design process. Developing an orally administered drug with an acceptable pharmacokinetic profile is necessary to reduce the cost and time associated with evaluating the extent of the first-pass metabolism of a candidate compound in preclinical studies. The aim of this study is to estimate the first-pass metabolism of an orally administered drug. A set of compounds with reported first-pass metabolism data were collected. Moreover, human intestinal absorption percentage and oral bioavailability data were extracted from the literature to propose a classification system that split the drugs up based on their first-pass metabolism extents. Various structural parameters were calculated for each compound. The relations of the structural and physicochemical values of each compound to the class the compound belongs to were obtained using logistic regression. Initial analysis showed that compounds with logD7.4>1 or a rugosity factor of > 1.5 are more likely to have high first-pass metabolism. Four different models that can predict the oral first-pass metabolism with acceptable error were introduced. The overall accuracies of the models were in the range of 72% (for models with simple descriptors) to 78% (for models with complex descriptors). Although the models with simple descriptors have lower accuracies compared to complex models, they are more interpretable and easier for researchers to utilize. A novel classification of drugs based on the extent of the oral first-pass metabolism was introduced, and mechanistic models were developedto assign candidate compounds to the appropriate proposed classes.

Modeling lignin extraction with ionic liquids using machine learning approach

Lignin, next to cellulose, is the second most common natural biopolymer on Earth, containing a third of the organic carbon in the biosphere. For many years, lignin was perceived as waste when obtaining cellulose and hemicellulose and used as a biofuel for the production of bioenergy. However, recently, lignin has been considered a renewable raw material for the production of chemicals and materials to replace petrochemical resources. In this context, an increasing demand for high-quality lignin is to be expected. It is, therefore, essential to optimize the technological processes of obtaining it from natural sources, such as biomass. In this work, an investigation of the use of machine learning-based quantitative structure-property relationship (QSPR) modeling for the preliminary processing of lignin recovery from herbaceous biomass using ionic liquids (ILs) is described. Training of the models using experimental data collected from original publications on the topic is assumed, and molecular descriptors of the ionic liquids are used to represent structural information. The study explores the impact of both ILs' chemical structure and process parameters on the efficiency of lignin recovery from different bio sources. The findings give an insight into the extraction process and could serve as a foundation for further design of efficient and selective processes for lignin recovery using ionic liquids, which can have significant implications for producing biofuels, chemicals, and materials.

Experimental research on the influence of acid on the chemical and pore structure evolution characteristics of Wenjiaba tectonic coal.

The chemical and pore structures of coal play a crucial role in determining the content of free gas in coal reservoirs. This study focuses on investigating the impact of acidification transformation on the micro-physical and chemical structure characteristics of coal samples collected from Wenjiaba No. 1 Mine in Guizhou. The research involves a semi-quantitative analysis of the chemical structure parameters and crystal structure of coal samples before and after acidification using Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) experiments. Additionally, the evolution characteristics of the pore structure are characterized through high-pressure mercury injection (HP-MIP), low-temperature nitrogen adsorption (LT-N2A), and scanning electron microscopy (SEM). The experimental findings reveal that the acid solution modifies the structural features of coal samples, weakening certain vibrational structures and altering the chemical composition. Specifically, the asymmetric vibration structure of aliphatic CH2, the asymmetric vibration of aliphatic CH3, and the symmetric vibration of CH2 are affected. This leads to a decrease in the contents of -OH and -NH functional groups while increasing aromatic structures. The crystal structure of coal samples primarily dissolves transversely after acidification, affecting intergranular spacing and average height. Acid treatment corrodes mineral particles within coal sample cracks, augmenting porosity, average pore diameter, and the ratio of macro-pores to transitional pores. Moreover, acidification increases fracture width and texture, enhancing the connectivity of the fracture structure in coal samples. These findings provide theoretical insights for optimizing coalbed methane (CBM) extraction and gas control strategies.

CPD model prediction of oil sand pyrolysis based on structural parameters from 13C NMR and FTIR measurements

Here, carbon-13 nuclear magnetic resonance spectroscopy (13C NMR) and Fourier transform infrared spectroscopy (FTIR) techniques were used to study the chemical structure characteristics of oil sand and its pyrolysis oil. The FTIR results showed that the values of the CH2/CH3 ratio, A-factor, and DOC1 of the pyrolysis oil decreased during the pyrolysis process, while the C-factor showed a maximum value with increasing pyrolysis temperature. The 13C NMR results showed that methylides and methylides were mainly contributed to oil production. The aliphatic chain in the pyrolysis oil has little alterations during pyrolysis, while the extent of aromatic ring substitution increases from 0.46 to 0.58. Furthermore, a correlation was obtained between the chemical structure of oil and the pyrolysis product yields of oil sand. Moreover, using chemical structure parameters investigated with FTIR and 13C NMR and kinetic parameters based on the thermogravimetric data, the chemical percolation devolatilization (CPD) model was applied to simulate the pyrolysis of oil sand. The results showed that the simulated results for tar and light gas were in good agreement with the experimental data, while those for char underpredicted the experimental data. Overall, the CPD model can effectively predict the pyrolysis of oil sand.

Coal-Derived Humic Substances: Insight into Chemical Structure Parameters and Biomedical Properties.

An investigation was carried out on humic substances (HSs) isolated from the coal of the Kansk-Achinsk basin (Krasnoyarsk Territory, Russia). The coal HSs demonstrate the main parameters of molecular structure inherent to this class of natural compounds. An assessment was performed for the chemical, microbiological, and pharmacological safety parameters, as well as the biological efficacy. The HS sample meets the safety requirements in microbiological purity, toxic metals content (lead, cadmium, mercury, arsenic), and radionuclides. The presence of 11 essential elements was determined. The absence of general, systemic toxicity, cytotoxicity, and allergenic properties was demonstrated. The coal HS sample was classified as a Class V hazard (low danger substances). High antioxidant and antiradical activities and immunotropic and cytoprotective properties were identified. The ability of the HS to inhibit hydroxyl radicals and superoxide anion radicals was revealed. Pronounced actoprotective and nootropic activities were also demonstrated in vivo. Intragastric administration of the HS sample resulted in the improvement of physical parameters in mice as assessed by the "swim exhaustion" test. Furthermore, intragastric administration in mice with cholinergic dysfunction led to a higher ability of animals with scopolamine-induced amnesia to form conditioned reflexes. These findings suggest that the studied HS sample is a safe and effective natural substance, making it suitable for use as a dietary bioactive supplement.

Experimental study on changes in components and pore characteristics of acidified coal treated by organic solvents

Chemical solvents could change coal components and effectively enhance conductivity of coal reservoir, which is beneficial to efficient methane extraction. Relationship between coal chemical structure parameters and main functional groups variations affected by acidification and tetrahydrofuran (THF) is investigated through infrared spectroscopy tests and curve peak fitting. Meanwhile, variations in fractal dimensionality and pore structure characteristics are studied by adopting low-temperature nitrogen adsorption tests and Frenkel-Halsey-Hill (FHH) fractal model. Main results are: (1) After extracting raw coal and acidified coal using THF with varying concentrations, absorbance of aromatic hydrocarbon –CH surface and aromatic methyl bond become weaker. While the proportion of substituted aromatic hydrocarbons increases in acidified coal than in raw coal. Acidification treatment could reduce strength of C-O-C absorption peak. Proportion of CH2 and CH3 in raw coal decreases with increasing THF concentration, indicating that THF could react with aliphatic structure to reduce CH2 and CH3 content. Extraction with THF dissolves aromatic structure, lowering C = C content in coal to different degrees. (2) Acidification pretreatment could produce more micropores in coal samples. Micropore contents of acidified coal after THF extraction are all lower than coal sample S, while transition pores and mesopores contents are both higher than those in coal sample S. (3) Fractal dimension D1 of raw coal indicates a relatively linear relationship with specific surface area, while the D1 of acidified coal is less correlated with specific surface area. The factor D2 shows a linear relationship with average pore size. After treatment of THF, average pore size of raw coal increases with D2, while that of acidified coal varies in different degrees with uneven distribution of pore sizes.

High entropy BaFe12-x(Ti/Mn/Ga/In)xO19 (x = 1–7) oxides: Correlation of the composition, entropy state, magnetic characteristics, and terahertz properties

The BaFe12-x (Ti/Mn/Ga/In)xO19 (x = 1–7) high-entropy oxides (HEOs) were obtained by solid-phase synthesis. The correlation of the chemical composition (the level of the Fe replacement), structural parameters, magnetic characteristics, and terahertz (THz) properties was investigated. All studied samples were single-phase (SG: P63/mmc). Lattice parameters showed a monotonic increasing trend with an increase of (x). The key role in increasing the lattice parameters of HEOs may belong to the influence of In3+ ions, which are much larger in size than Fe3+ ions. As one of the possible reason for explanation of the lattice parameters behavior we hypothesized that partial charge transformation of the Mn3+ state to the Mn2+ state takes place in order to maintain electrical neutrality. Other cations (Ti/Ga/In) have stable oxidation state. The anisotropic nature of the increase in lattice parameters was demonstrated. No strong correlation between chemical composition and microstructural parameters of the investigated HEOs was observed. The magnetic characteristics of the BaFe12-x (Ti/Mn/Ga/In)xO19 (x = 1–7) HEOs were investigated at broad intervals of magnetic fields and temperatures. The behavior of the magnetic characteristics was shown to be the result of the magnetic structure frustration. In addition, terahertz electrodynamic properties were studied by measuring spectra of complex dielectric permittivity at frequencies 0.2–1.2 THz in the temperature interval 20–300 K. The spectra indicate the presence of a higher-frequency infrared phonon resonance, whose damping decreases with cooling, as well as an excitation below 0.2 THz that freezes out at low temperatures, the origin of which is associated with the polycrystalline nature of the materials.

Experimental investigation of hydrocarbon-ion interaction in water-oil emulsions: A new insight into asphaltene structure and chemistry

Emulsification has been proved as one of the mechanisms contributing to improving oil recovery. Regarding the amphiphilic nature of the asphaltene and other polar hydrocarbons, their role should be understood. This research aims to investigate the chemistry and structure of the asphaltene molecules in the emulsions generated by the oil and ion-tuned water. The static bottle tests, containing the aqueous, emulsion, and bulk oil phases, were generated to study the emulsification. To have a mechanistic insight into the participation of asphaltene molecules in the emulsion phase, two oil samples of crude oil and asphaltene-rich toluene were used to generate the emulsions. After extracting the asphaltene from the bulk phases, the analytical techniques of Nuclear Magnetic Resonance (NMR), Fourier transform infrared (FTIR), and Energy-dispersive X-ray (EDX) were employed to study the asphaltene structural parameters, functional groups, and elemental content, respectively. Based on the NMR technique, the asphaltenes with smaller aromatic cores and shorter aliphatic chains, which contain polar functional groups have more tendency to adsorb onto the emulsion phase. It was shown that the magnesium and calcium ions have stronger electrostatic interactions with the asphaltene, leading to more attraction of the asphaltenes in the emulsion phase. In contrast, the sulfate ions showed a weaker attraction force to adsorb the asphaltenes in the emulsion phase. Based on the EDX spectroscopy, the heteroatom (oxygen, nitrogen, and sulfur) contents of the crude asphaltene is more than the bulk one, representing more affinity of the polar asphaltenes toward the emulsion phase. According to the FTIR spectroscopy of the bulk oil, while the aromatic hydrocarbons have a lower affinity toward the emulsion phase, the longer alkanes have more affinity to adsorb onto the emulsion phase. It should be mentioned that the chemistry and structural parameters of the bulk asphaltenes in the emulsions, which were generated by crude oil and asphaltene-rich toluene, were different. This observation indicated that the chemistry of the asphaltenes participating in the emulsion phase is influenced by the presence of other amphiphilic hydrocarbons. In this study, it was shown that chemical functional groups and structural parameters of asphaltene affect the emulsification process. Hence, studying the chemistry of asphaltene and other polar hydrocarbons is a vital step for the formulation of optimum ion-tuned water.

Insights into photo-induced excited state behaviors for 2-[4-(Di-tert-butyl-amino)-phenyl]-5-(5-fluoro-benzooxazol-2-yl)-benzofuran-6-ol: Solvent effects

Inspired by distinguished white emitters characteristics and potential fluorescence probe performance, we mainly focus on exploring photo-induced behaviors of 2-[4-(Di-tert-butyl-amino)-phenyl]-5-(5-fluoro-benzooxazol-2-yl)-benzofuran-6-ol (DPFB) fluorophore. By comparing changes of chemical structure parameters and variations of infrared (IR) spectrum, we confirm hydrogen bond should be strengthened after photoexcitation. Combined with charge recombination caused by photoexcitation in different solvents, we propose nonpolar solvents are favorable to excited-state dynamic behavior. By searching transition state (TS) form along with excited state reaction path as well as constructing energy profiles, we clearly reveal the solvent polarity dependent excited state intramolecular proton transfer (ESIPT) mechanism for DPFB fluorophore.

METHODOLOGY OF OBTAINING CHROMIUM CARBONYL COMPLEXES AND DEVICES USED IN OBTAINING THEM

The development of modern technology and the long-term processing of materials and constructions used in high temperature conditions make great demands. It is very important to obtain hard-melting metals that meet these requirements. In nature, the scarcity of hard-to-melt metals and their high cost force us to find other more efficient ways. One such solution is the application of hard- -melt metals in the form of thin layers or coatings on metals or structures. For to this purpose, carbonyl compounds of hard-to-melt metals are widely used in technology recently. Carbonyl compounds have important properties, one of which is that they act as raw materials for obtaining coatings and layers through thermal decomposition. However, some difficulties arise in obtaining chromium coatings based on chromium carbonyl complexes with organic ligands. In order to overcome such difficulties, the synthesis methodology of two chromium-based complex compounds with easy volatility and low decomposition temperature, which are used in the production of corrosion-resistant coatings, and the temperature range in their decomposition limits, physical chemical structure parameters have been determined. The research found that both chromium carbonyl complexes obtained by synthesis form chromium coatings with high adhesion on the metal carrier and increase their corrosion resistance. Chromium carbonyl complexes can serve as technologically favorable raw materials for obtaining the necessary chromium coating during the decomposition of groups at a very low temperature range (100-150 C) without creating additional pressure. Both synthesized complex compounds are raw materials for obtaining corrosion-resistant coatings on weld seams of 09Г2С steel. The use of these complexes as active fillers in abrasive metallurgy has also been determined. Keywords: Chromium, solvent, toluene, mesethylene, infrared spectrum, chromium carbonyl, complex, melting, decomposition, coating, heating, solution.

Local Geometry of Tetrahedrally Coordinated Boron Correlates with 11B NMR Chemical Shifts in Borosilicate Minerals

Chemical shifts from the 11B nuclear magnetic resonance (NMR) spectra of crystalline borosilicate minerals with highly ordered, tetrahedrally coordinated boron atoms (B) linearly correlate with the local geometric parameters related to the B–O–T angles (T denotes a tetrahedrally coordinated atom) obtained from single-crystal X-ray diffraction. The correlations between the 11B NMR chemical shifts and structural parameters are similar in functional form to the well-known correlations of 29Si and 27Al NMR chemical shifts with structural features of silicates and aluminosilicates, respectively. These correlations enable the use of 11B NMR chemical shifts to elucidate the local geometry of tetrahedrally coordinated B and aid in establishing B ordering among the crystallographic T-sites within crystalline borosilicates.

Correlation between the composition, structural parameters and magnetic properties of spinel-based functional nanocomposites

The “soft/soft” (CoFe 2O4)x/Ni0.4Cu0.2Zn0.4Fe2O4)y nanocomposites (NCs), as a function of the phase ratio, have been synthesized via the green sol–gel method using 6 dates. The correlation between chemical composition, structural parameters and magnetic properties was investigated. The average crystallite size (Dmax) of the products was found to be within the range of 24.6-41.1 nm. It was observed that an increase in the CoFe 2O4 content leads to an increase in the most probable size of the coarse fraction and a decrease in the most probable grain size of the fine fraction. As the (Ni0.4Cu0.2Zn0.4)Fe2O4 content increases, the average size of the fine and coarse fractions decreases. The magnetic properties were investigated in a wide magnetic field range (80 kOe) at 300 and 10 K. The maximum magnetization saturation or Ms (∼124.3 emu/g at 10 K and ∼81.2 emu/g at 300 K) was observed for the sample with the ratio 1/2 that was ∼30% higher than Ms for the pure (Ni0.4Cu0.2Zn0.4)Fe2O4 ferrite at 10 K (∼86.9 emu/g) and ∼35% higher than at 300 K (∼52.8 emu/g). This fact clearly demonstrates the presence of a synergetic effect in the NCs. The dominance of low-temperature Ms values was explained by the lack of thermal energy of the disordered spin. The presence of a synergetic effect in the (CoFe 2O4)x/Ni0.4Cu0.2Zn0.4Fe2O4)y NCs can be observed due to a strong coupling between the two magnetic phases, according to careful analysis of the correlation between the chemical composition, structural parameters and magnetic properties.

Developing high-Q × f value MgNb2–xTaxO6(0≤x≤0.8) columbite ceramics and clarifying the impact mechanism of dielectric loss: Crystal structure, Raman vibrations, microstructure, lattice defects, chemical bond characteristics, structural parameters, and microwave dielectric properties in-depth studies

With the increasing frequency of wireless mobile communication, dielectric materials with higher Q × f are required to enhance the signal strength of microwave passive devices and thus compensate for the rapid attenuation of high-frequency signals during propagation. In order to improve the Q × f of the MgNb2O6 system and study the internal mechanism between the structure and microwave dielectric properties, Ta5+ ion is introduced to design and fabricate MgNb2−xTaxO6 (0 ≤ x ≤ 0.8) ceramics by the solid-state reaction method. The single columbite phase and dense structure are observed throughout the entire composition range. All elements (Mg, Nb, Ta, and O) can be detected by X-ray photoelectron spectroscopy. Insights from the Raman spectroscopy and group theoretical analysis reveal that the Ag(2) and Ag(3) modes located at ∼ 905 cm−1 dominate the Raman vibration. In addition, the ɛr depends on the polarizability reflected by the C–M equation and Raman shift. The τf closely relates to the bond energy of the Nb/Ta–O bond and restoring force characterized by average octahedral distortion of [Nb/TaO6]. Notably, the crucial factors for the huge improvement of Q × f are clarified deeply, in terms of the lower internal strain, the reduced ordering-induced domain size, and the chemical bond valence closer to the ionic valence state, which promotes the stability of crystal structure. Moreover, the introduction of lower electronegative ions enhances the ability of electrons to compensate for oxygen vacancies, thereby reducing the dielectric loss caused by the conductance. Excellent microwave properties (ɛr = 19.2, Q × f = 170,000 GHz, and τf = −55.6 ppm °C–1) are achieved in MgNb1.4Ta0.6O6 ceramic, specifically a nearly 40% increase in the Q × f. This work has enriched the theory associated with low dielectric loss and provided the MgNb1.4Ta0.6O6 ceramic with a pretty high-Q × f for the application in the design of the 5G/6G wireless communication devices.

Sn-Co co-substituted SrSnxCoxFe12-2xO19 strontium hexaferrites: Correlation between chemical composition, magnetic and electrical properties

M-type strontium hexaferrites attract great attention due to the scientific importance and practical significance. It was observed the correlation between chemical composition, structural parameters, magnetic and electrical properties in heterovalent double substituted Sr hexaferrites. As substituents were used Co2+ and Sn4+ ions. X-ray diffraction data is used to compute a variety of parameters, including lattice parameters, and size of crystallite, in addition to validating purity of the materials. All investigated samples were single phase and characterized by the P63/mmc space group. Increase of the substituent concentration leads to the increase of the lattice parameters that correlated well with average ionic radii of the Fe3+, Co2+ and Sn4+. The average size of a crystallite was between 31 and 45 nm. Magnetic parameters were obtained from field dependences of the specific magnetization It was observed non-linear dependence in magnetic properties as function of the chemical composition. Increase of the sn-Co concentration leads to increase of the DC electrical resistivity. The dielectric constant is reduced while DC electrical resistivity increased from 5.94 to 11.7 × 109 Ohm cm, suggesting that materials can be employed in microwave devices because of their high resistivity and minimal dielectric constant.

Thermal maturity and chemical structure evolution of lump long-flame coal during superheated water vapor–based in situ pyrolysis

Oil and gas products can be successfully obtained from low-rank coal using superheated water vapor in situ pyrolysis technology, and investigating the pyrolysis properties of coal during this process is crucial. Herein, the in situ pyrolysis of lump long flame coal with superheated water vapor using a proprietary superheated water vapor pyrolysis system was simulated. The vitrinite reflectance (Ro) and functional groups of coal samples were analyzed using a microscope photometry and Fourier transform infrared spectroscopy. Moreover, the relationship between the chemical structural parameters and vitrinite reflectance during different thermal maturation processes was examined. The results indicate that the vitrinite reflectance increased from 1.01% for raw coal to 2.2% at 550 °C as the pyrolysis temperature increased. The ranges of the critical temperature for the removal of aliphatic structures, C–O, CO, –OH, and aromatic structures from the coal were 271°C-506 °C, 333°C-550 °C, 220°C-550 °C, RT–333 °C, and 333°C-550 °C, respectively. As Ro increased, the aromaticity and condensation both increased linearly and then decreased; the CH2/CH3 ratio first decreased and then increased; the C-factor exhibited negative exponential reduction. Artificial thermal maturation was more effective than natural thermal maturation in promoting the evolution of the aliphatic structure but less effective in promoting the condensation of aromatic rings. Both types of thermal maturation have the same effect on the evolution of aromaticity and C-factor.

Evolution of mechanical properties of kerogen with thermal maturity

Kerogen is the most abundant form of naturally occurring organic matter in organic-rich shale, and it can affect the macro-mechanical characteristics of shale reservoirs during the whole shale thermal evolution process. However, the magnitude and mechanism of this effect are not clear. Here, a relatively low-maturity kerogen isolated from an organic-rich shale was used to prepare a series of kerogen samples of different maturities in an artificial pyrolysis experiment. Raman spectroscopy and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy were used to determine changes in the chemical structures of the kerogen samples, and in situ nanoindentation analysis was employed to characterize the evolution of their mechanical properties. Raman spectral analyses indicate that Raman band separation (RBS) is very sensitive to thermal maturity, increasing with maturity and displaying a strong linear correlation with mechanical properties of kerogen such as hardness and Young's modulus. Based on the solid-state 13C NMR and nanoindentation analysis, the evolution of kerogen mechanical properties with maturity can be divided into two stages: oil-generation wet-gas stage (corresponding to 0.7%–2.5% EasyRo), and dry-gas stage (2.5%–4.5% EasyRo). In the former, kerogen exhibits a soft nature with relatively low hardness and Young's modulus, possibly attributable to its relatively large proportion of aliphatic carbon and long-chain alkanes. When maturity reaches the gas stage, kerogen becomes increasingly stiff due to the markedly increased proportion of aromatic and bridgehead carbon. Considering the strong positive correlation between mechanical parameters and chemical-structure parameters (RBS, and aromatic and bridgehead carbon ratios) of kerogen during the overall thermal evolution process, we suggest that the stiffening of kerogen may result from the decreasing content of aliphatic chains and increasing aromatic carbon. This study will be beneficial to the development of rock mechanical models that are critical for accurately evaluating borehole stability and optimizing hydraulic fracture design.

Aquatic arsenic removal with a Zr-MOF constructed via in situ nitroso coupling

Assembly of hexanuclear Zr-oxo clusters via in situ covalent coupling of nitroso groups afforded a metal–organic framework (MOF) with fcu topology. The MOF, namely SUM-8, emerged as an excellent adsorbent for aquatic arsenic removal in terms of adsorptive efficiency, capacity, selectivity, and cyclability, on accounts of its chemical stability and structural parameters suitable for arsenate diffusion/accommodation.

Mechanistic Study on the Impact of the Occurrence of Various Basic Mineral Species on Spontaneous Combustion Propensity of Alkali‐Rich Low‐Rank Coal

AbstractSpontaneous combustion of low‐rank coal, especially alkali‐rich coal, is a key issue that determines the safety of storage and transportation. To understand the role of different forms of Alkali and alkaline earth metals (AAEMs) on coal spontaneous combustion, AAEMs in raw coal were sequentially eluted by water, ammonium acetate (NH4OAc) and hydrochloric acid (HCl) solution. The occurrence forms and mineralogical characteristics of AAEMs in raw coal and its derived coal samples were investigated. Further, the spontaneous combustion tendency of raw coal and derived coal samples was measured by programmed heating process and the chemical structure parameters were characterized by thermogravimetric analysis and differential scanning calorimetry (TGA‐DSC) and in situ infrared spectroscopy. The results show that demineralization mitigates the spontaneous combustion tendency by the increasing the ignition temperature, confirming the enhancement of inherent mineral on low‐temperature oxidation. In situ infrared spectroscopy results suggest that acid‐soluble and ion‐exchangeable AAEMs have greater catalytic impact on the oxidation reaction of coal than water‐soluble AAEMs. Specifically, the complete removal of AAEMs by acid‐washing treatment has the most obvious effect on the change of oxygen‐containing functional groups, which greatly reduces the generation rate of carboxylic acid, ester and anhydride groups during the low temperature oxidation. Moreover, calcium elements including ion‐exchangeable calcium and HCl‐soluble calcium can promote the oxidation capacity of coal at low‐temperature, which were verified by loaded coal samples.

Thermal evolution of chemical structure and mechanism of oil sands bitumen

Oil sands bitumen (OSB) is the key component of extracted oil sands, thus further investigation of the mechanism of OSB pyrolysis reaction would be helpful for the development and application of oil sands pyrolysis process. First, chemical structure parameters and thermogravimetric (TG) behavior of OSB were experimentally investigated by 13C NMR spectroscopy and TG analysis, respectively, to initially evaluate the correlation between chemical structure parameters and pyrolytic behavior. Further, the ATR–FTIR spectroscopy technology was used to experimentally characterize and calculate the structural parameters of OSB at different pyrolysis final temperatures, and the main thermal evolution rules of different functional groups during the pyrolysis reaction were obtained. Based on this result and by using the model fitting method, the pyrolysis of OSB was found to be a parallel reaction. Moreover, the kinetic calculation results obtained by Straink method and distributed activated energy model method also supported this result. The correlation between chemical structure parameters and activation energy was analyzed, and it was found that the degree of aromatization Y-factor could be used to characterize the pyrolysis reaction activity. Finally, this study proposed a simplified mechanistic model of chemical structure evolution during OSB pyrolysis.

Control of chemical structure on the characteristics of micropore structure in medium-rank coals

The formation and evolution of micropore was controlled by molecular structure to a certain extent. To study the influence of chemical structure on micropore structure, a well characterized sample set of coals covering a vitrinite reflectance (Ro,max) interval from 1.08% to 1.80% was selected from the Xishan coalfield, China. CO2 isothermal adsorption experiments at 273.15 K were used to characterize micropore structure in coals, and 13C nuclear magnetic resonance (13C NMR), FTIR and Raman spectrum were employed to obtain the chemical structural parameters of those coal samples. The relationship between structural parameters and micropore structure showed that micropore volume increased with increasing aromatic carbon (fa’), aromaticity (I) and the degree of condensation of aromatic ring (DOC), which demonstrated that micropore volume was mainly controlled by the aromatic part of the coal samples when Ro,max ranging from 1.21% to 1.80%. Moreover, the ZCD-2 sample (Ro,max = 1.21%) has the lowest micropore volume, which may be caused by the lower value of DOC or blocking of asphaltene in the second coalification jump. The micropore volume increases with increasing band position difference of D peak and G peak (G-D) and AD/AG, which suggests that the degree of order and more ordered rings (≥ 6 rings) mainly control the micropore formation. The findings help to understand the mechanism by which chemical structure controls the evolution of micropores, and further provide mechanistic insights of gas sorption and diffusion.