Macromolecular Network Structure Research Articles

Simulations on coal water slurry gasification by molecular dynamics method with ReaxFF.

Coal water slurry (CWS) is a new type of liquid coal product with low pollution, which is mainly used in the chemical industry to produce syngas (CO + H2). It is of great significance to study the microscopic mechanism of CWS gasification reaction for improving the efficiency of coal gasification. In this paper, the method of molecular dynamics based on reaction force fields (ReaxFF-MD) is used to study the gasification process of CWS/O2 system at different temperatures. The results show that, in the range of 1600-2400 K, the macromolecular network structure of lignite is decomposed into a large number of small molecular structures and a small number of light tar free radical fragments, and the types and quantities of reaction products increased rapidly. At 2400-4000 K, the free radical fragments of light tar are further decomposed and reacted with gasification agents, but the types and quantities of reaction products have little change. At 3600 K, a full gasification reaction occurred in the system, and the content of syngas is the highest. The model was established and optimized by Materials Studio (MS) software. Based on ReaxFF-MD method, Lammps software was used to simulate the gasification process of CWS/O2 system, and the reaction force field files containing C, H, O, N, and S element were used. By calculating the activation energy of gasification reaction, the rationality of the model and calculation method was illustrated. The post-processing of the results was implemented using OVITO, ChemDraw software, and self-programmed Python scripts.

Composition Distribution of the Thermal Soluble Organics from Naomaohu Lignite and Structural Characteristics of the Corresponding Insoluble Portions.

With cyclohexane (CH), benzene (BE), and ethyl acetate (EA) as solvents, Naomaohu lignite (NL, a typical oil-rich, low-rank coal) from Hami, Xinjiang, was thermally dissolved (TD) to obtain three types of soluble organics (NLCH, NLBE, and NLEA) and the corresponding insoluble portions (NLCH-R, NLBE-R, and NLEA-R). Ultimate analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG), and gas chromatography-mass spectrometry (GC/MS) were used to characterize NL and its soluble and insoluble portions. Results showed that, compared with NL, the C element in NLCH-R, NLBE-R, and NLEA-R increased, while the O element decreased significantly, indicating that thermal dissolution is a carbon enrichment process and an effective deoxidation method. The GC/MS results showed that oxygen-containing organic compounds (OCOCs) are dominant in NLCH, NLBE, and NLEA. NLCH is mainly composed of ketones (11.90%) and esters (19.04%), while NLBE and NLEA are composed of alcohols (12.18% and 2.42%, respectively) and esters (66.09% and 84.08%, respectively), with alkyl and aromatic acid esters as the main components. Among them, EA exhibits significant selective destruction for oxygen-containing functional groups in NL. XPS, FTIR, and TG-DTG results showed that thermal dissolution can not only affect the macromolecular network structure of NL, but also improve its pyrolysis reactivity. In short, thermal dissolution can effectively obtain oxygen-containing organic compounds from NL.

Microstructure and durability of rapid repair mortar with self-emulsifying waterborne epoxy polymer

Due to the low hydration rate of ordinary Portland cement (OPC), it cannot meet the requirements of rapid repair, especially in negative temperature environments. Simultaneously, facing the harsh marine environment, repair materials urgently need high durability. In this paper, a self-emulsifying waterborne epoxy polymer (WEP) suitable for cement systems was combined with sulfoaluminate cement (SAC) to prepare repair materials. The effect of the WEP on the development of microstructure, auto-drying shrinkage and durability was investigated by nuclear magnetic resonance, XRD and SEM methods. Results showed that a continuous interpenetration polymer network (IPN) was intricately woven within the multiphase composites, using the macromolecular network structure formed by —OH groups in WEP and Ca2+ and Al3+ in cement as a bridge. The resistance to chloride migration and water absorption exhibited an increase followed by a decrease. In particular, the resistance to chloride migration was improved by 45 %. Similar trends were observed for the carbonation resistance. Due to the lower porosity and capillary pressure caused by IPN, leading to a decrease in auto-drying shrinkage. Nevertheless, the larger percentage of capillary pores in a mortar with a P/C of 15 % increased the auto-drying shrinkage. The WEP decreased the availability of pores of critical diameter (14 nm) of mortar exposed to water freezing, leading to an increase in the freeze-thaw resistance. The change in P/C hardly affected the resistance to sulfate attack. Under −10°C, at 2 hours, the compressive strength of CSA-based mortar satisfied the load requirements for vehicular operations. This research provides theoretical and practical implications for the repair work of large-scale projects serving in harsh environments.

Early Detection and Monitoring of Anastomotic Leaks via Naked Eye-Readable, Non-Electronic Macromolecular Network Sensors.

Anastomotic leakage (AL) is the leaking of non-sterile gastrointestinal contents into a patient's abdominal cavity. AL is one of the most dreaded complications following gastrointestinal surgery, with mortality rates reaching up to 27%. The current diagnostic methods for anastomotic leaks are limited in sensitivity and specificity. Since the timing of detection directly impacts patient outcomes, developing new, fast, and simple methods for early leak detection is crucial. Here, a naked eye-readable, electronic-free macromolecular network drain fluid sensor is introduced for continuous monitoring and early detection of AL at the patient's bedside. The sensor array comprises three different macromolecular network sensing elements, each tailored for selectivity toward the three major digestive enzymes found in the drainage fluid during a developing AL. Upon digestion of the macromolecular network structure by the respective digestive enzymes, the sensor produces an optical shift discernible to the naked eye. The diagnostic efficacy and clinical applicability of these sensors are demonstrated using clinical samples from 32 patients, yielding a Receiver Operating Characteristic Area Under the Curve (ROC AUC) of 1.0. This work has the potential to significantly contribute to improved patient outcomes through continuous monitoring and early, low-cost, and reliable AL detection.

Preparation of reed fibers reinforced graft-modified starch-based adhesives based on quantum mechanical simulation and molecular dynamics simulation

Starch is a biomass polymer material with a high yield and comprehensive source. It is used as a raw material for preparing adhesives because of its highly active hydroxyl group. However, poor adhesion and water resistance hinder the application of starch-based adhesives (SBAs). Based on this, the starch was modified through graft copolymerization with itaconic acid as a cross-linking agent, methyl methacrylate and methyl acrylate as copolymers. Additionally, reed fibers were synergistically modified with polydopamine deposition to prepare an environmentally friendly SBA used in plywood production. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H NMR), X-ray diffraction (XRD), and thermogravimetric analysis (TG) demonstrate that copolymerization of methyl methacrylate and methyl acrylate with starch improves the shear strength, water resistance, and thermal stability of the SBA. Compared to unmodified starch, the modified SBA exhibits a 129 % increase in dry strength and achieves a wet strength of 1.36 MPa. Fukui function, Frontier orbit theory, and molecular dynamics simulation have shown that itaconic acid promotes the copolymerization of starch and acrylate monomers. The modified starch has fewer hydrogen bonds, less order, and a denser macromolecular network structure, which provides a reference for studying the molecular interaction mechanisms of SBAs.

The Mechanism of Ozone Oxidation of Coal and the Revelation of Coal Macromolecular Structure by Oxidation Products.

Ozone was injected into a coal-water suspension, and an HRTEM test was carried out on the separated oxidation products. The results show that from the perspective of visualization the macromolecular network structure of coal contains a large number of graphite-like structures. However, the chemical reaction mechanism between the coal surface and O3 is not clear, and the microscopic formation mechanism of oxygen-containing functional groups in carbon quantum dots has not been explained. As a result, the reaction process between O3 and methylene on the coal surface was studied by the DFT method. We found that OH• generated by O3 in water can oxidize two adjacent carbon atoms in methylene into double bonds (C=C), and finally, aldehydes and carboxylic acids were generated. By calculation of thermodynamic parameters ΔG and ΔH, it is found that all reactions are spontaneous exothermic processes. The above chemical reaction is based on the physical adsorption of OH• with Ar-(CH2)6-Ar and O3 with Ar-CH2-CH=CH-(CH2)3-Ar. The calculated adsorption energies of the two systems are -9.41 and -12.55 kcal/mol, respectively. Then, the charge transfer and atomic orbital interaction before and after adsorption are analyzed from the perspectives of Mulliken charge, density of states, deformation density, and total charge density. The results show that the electrostatic attraction is the main driving force of adsorption. The ether bond (C-O-C) in coal is finally oxidized to an ester group (RCOOR'), the hydroxyl group (CH2-CH-OH) on the aliphatic chain is oxidized to a carbonyl group (CH2-C=O), and the benzene with two OH• forms phenol hydroxyl and one molecule of water. Finally, the coal and the corresponding coal-based carbon quantum dots were investigated by infrared spectroscopy; the difference in functional groups before and after oxidation was clarified, and the result was in good agreement with the simulation.

Microstructure and phase evolution behavior of SiZrBC ceramic precursors synthesized via sol–gel method

ZrB2–SiC ceramics were successfully prepared via sol–gel method using phenyltrichlorosilane, borane dimethyl sulfide, and zirconium tetrachloride in stoichiometric amounts as the raw materials. The macromolecular network structure formed after the sol–gel process was investigated via Fourier transform infrared (FT–IR) spectroscopy. The phase evolution of the ZrB2–SiC ceramics were analyzed by FT–IR spectroscopy, X–ray diffraction, and transmission electron microscopy, whereas morphological and elemental analyses were performed using scanning electron microscopy. In particular, the change in phase composition was monitored after the pyrolysis from 1400 to 1500 ​°C, and the heat treatment of BZ6 precursor at 1500 ​°C enabled one to produce the ZrB2–SiC ceramic with a homogeneous crystal phase distribution. Therefore, the controllable microstructure adjustment of the ceramic phase composition could be achieved and a new way was paved for the structural and functional applications of ultra–high–temperature ceramics (UHTCs) series.

Polymer precursor synthesis of novel ZrC–SiC ultrahigh-temperature ceramics and modulation of their molecular structure

In this study, ZrC–SiC composite ceramics were prepared with varying Zr/Si molar ratios using sol–gel method. Composites were characterized by Fourier-transform infrared spectroscopy (FT–IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS). FT–IR analysis confirmed macromolecular network structure of composites, in which the precursor is composed of polyvinyl butyral (PVB) as main chain, silane molecules are interlinked via –OH moieties in PVB side chains, and Zr atoms are crosslinked with Si in corresponding proportion. Ceramic precursor begins to decompose at a temperature exceeding 1300 °C and is completely transformed into ZrC–SiC composite ceramics with corresponding Zr/Si molar ratio at 1600 °C. Raman spectroscopy and TEM results reveal that after annealing at 1600 °C, ZrC powder uniformly covers surface of SiC ceramics, and high-crystallinity graphite carbon covers ZrC powder.

Multifunctional carboxymethyl cellulose sodium encapsulated phosphorus-enriched biochar composites: Multistage adsorption of heavy metals and controllable release of soil fertilization

Water and soil heavy metal contamination induced by wastewater irrigation endanger human health. To improve the long-term heavy metal removal performance in the complicated aqueous/soil system, a novel carboxymethyl cellulose sodium (CMC-Na) encapsulated phosphorus (P)-enriched biochar (CMC@MBC) was synthesized. The maximum adsorption capacities of the unmodified biochar for Pb(II), Cd(II), and Ni(II) were increased by 822, 464, and 256 mg/g, respectively. The CMC-Na encapsulation introduced abundant carboxymethyl groups and enables CMC@MBC a strong anti-pH interference ability. The sewage treatment result revealed that CMC@MBC functioned admirably with prolonged sewage flushing. The long-term effectiveness of CMC@MBC against heavy metals might be explained by a multistage adsorption process: immediate adsorption by the CMC-Na coating, fast adsorption at the interface of CMC-Na and P-enriched biochar (MBC), and delayed adsorption by the P compound progressively released from MBC. Heavy metal speciation analysis indicates that the contributions of different adsorption mechanisms vary with heavy metals. The macromolecular spatial network structure of CMC-Na could be a good cover for preventing P leaching, making CMC@MBC a great slow-release fertilizer (SRF) with a cumulative P release ratio of 61 % after 28 days of application. This work suggests that CMC@MBC is a low-cost and high-efficiency adsorbent and phosphorus SRF.

Mechanism of aliphatic hydrogen on the caking property of 1/3 coking coal during rapid preheating

It is of significance to reveal the mechanism of rapid preheating to enhance the caking property of coking coal and expand high-quality coking coal resources. In this study, a 1/3 coking coal was preheated at two low and one rapid rates, then raw coal and heat-treated samples were comprehensively analyzed. The results revealed that the aliphatic H in coal formed volatiles at the early stage of pyrolysis (≤ 380 °C) under low-rate preheating. In the thermoplastic stage, the bonding phase was confirmed to be formed by a part of aliphatic H. The decreases amount of volatile and hydrogen contents and H/C and O/C atomic ratios of rapidly preheated coals were less than those of low-rate preheated coals, indicating that its thermal decomposition reaction degree was lower. This was considered to be the basis for keeping G values of rapidly preheated coals from decreasing. The aliphatic H concentration and CH2/CH3 ratios of rapidly preheated coals were higher and lower than those of raw coal respectively, which contributed to the fact that their G values were basically close to or higher (∼349–401 °C) than that of raw coal. Rapid preheating weakened the consumption of aliphatic H by volatiles formed during low-rate heating. Moreover, it forced weak bonds in the molecular of coal to break, such as bridge bonds and intermolecular forces that connect structural units. The breaking of bridge bonds between alkyl side chains or cycloalkanes and aromatic groups enhanced hydrogen supply. The weakening of intermolecular force resulted in loose macromolecular network structure and enhanced molecular dynamic properties. These evolutions of coal molecular structure strengthened the combination of hydrogen and free radicals and generated more bonding phases. Finally, a mechanism which provided a new explanation for the rapid preheating to alter the molecules structure and enhance the caking property of coking coal was proposed, and it will be significant valuable to enlarge the utilization of weakly-caking coal in coking process.

(AlCrMg)x(PO4)y/MgO composite: A new thermal protection and insulation material up to 2400 °C

A (AlCrMg)x(PO4)y/MgO composite(APMC) was prepared based on the acid–base reaction between MgO and chromium aluminum phosphate solution for thermal protection and insulation applications at ultrahigh-temperatures up to 2400 °C. The compositions, formation mechanisms, microstructure, mechanical properties, thermal conductivity and ablation resistance of the composite were systematically investigated. The results show that the (AlCrMg)x(PO4)y/MgO composite can be consolidated in different shapes at room temperature. The compressive strength of the as-prepared porous composites is higher than 20 MPa due to the macromolecular network structure, and it can be further improved to 42 MPa via thermal treatment. After ablation by an oxyacetylene flame at 2400 ± 70 °C for 60 s, the mass and line ablation rates of the composite were 0.0195 g/s and 0.43 × 10−3 mm/s, respectively, which are comparable to those of ultrahigh-temperature ceramics. The excellent ablation resistance can be attributed to the in situ formation of a dense protective layer composed of spinel MgCr2O4 and MgO phases. Interestingly, during ablation at 2400 °C the back-side temperature of the 15 mm-thick sample was lower than 130 °C, suggesting outstanding thermal insulation performance. The temperature gradient leads to the formation of a gradated porous structure which reduces the overall thermal conductivity of the composite.

Biodegradable Films Prepared from Pulp Lignocellulose Adhesives of Urea Formaldehyde Resin Modified by Biosulfonate.

Traditional low-density polyethylene (LDPE) film causes environmental pollution; there is a pressing need to make new bio-based polymers for alternative products, to meet agricultural production needs and for sustainable ecological development. In this study, urea-formaldehyde resin (UF) was modified with polyvinyl alcohol (PVA) and 1–2.5% bio-based sulfonate (BBS). The influence of BBS inducing on the functional groups, microstructure, and thermal behavior was evaluated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). A biodegradable film was prepared with modified UF resin as adhesive and pulp lignocellulose as raw material. The biodegradable mulch film samples were tested for biodegradability, water retention, and cooling soil temperature characters using LDPE and no mulching (NM) as a control. The results showed that with the increase of BBS content, the viscosity and reactivity of modified PUF resin increased, and the free formaldehyde content decreased. A 2%BBS modified PUF resin (2.0BBS/PUF) accelerated the curing process of the PUF resin, formed a flexible macromolecular network structure, and enhanced the toughness of the resin. The biodegradable mulch prepared with PUF, BBS, and 2.0BBS/PUF as adhesives had good water retention. BBS modification increased the degradation rate of mulch by 17.53% compared to the PUF. Three biodegradable films compared with LDPE and NM significantly reduced the soil temperature under summer cucumber cultivation, and the 2.0BBS/PUF coating had the lowest diurnal temperature difference, which provided a suitable soil environment for crop growth.

A New Kinetic Modeling Approach for Predicting the Lifetime of ATH-Filled Silane Cross-Linked Polyethylene in a Nuclear Environment.

This study focuses on the degradation of a silane cross-linked polyethylene (Si-XLPE) matrix filled with three different contents of aluminum tri-hydrate (ATH): 0, 25, and 50 phr. These three materials were subjected to radiochemical ageing at three different dose rates (8.5, 77.8, and 400 Gy·h−1) in air at low temperatures close to ambient (47, 47, and 21 °C, respectively). Changes due to radio-thermal ageing were investigated according to both a multi-scale and a multi-technique approach. In particular, the changes in the chemical composition, the macromolecular network structure, and the crystallinity of the Si-XLPE matrix were monitored by FTIR spectroscopy, swelling measurements in xylene, differential scanning calorimetry, and density measurements. A more pronounced degradation of the Si-XLPE matrix located in the immediate vicinity of the ATH fillers was clearly highlighted by the swelling measurements. A very fast radiolytic decomposition of the covalent bonds initially formed at the ATH/Si-XLPE interface was proposed to explain the higher concentration of chain scissions. If, as expected, the changes in the elastic properties of the three materials under study are mainly driven by the crystallinity of the Si-XLPE matrix, in contrast, the changes in their fracture properties are also significantly impacted by the degradation of the interfacial region. As an example, the lifetime was found to be approximately halved for the two composite materials compared to the unfilled Si-XLPE matrix under the harshest ageing conditions (i.e., under 400 Gy·h−1 at 21 °C). The radio-thermal oxidation kinetic model previously developed for the unfilled Si-XLPE matrix was extended to the two composite materials by taking into account both the diluting effect of the ATH fillers (i.e., the ATH content) and the interfacial degradation.

New Advances in the Kinetic Modeling of Thermal Oxidation of Epoxy-Diamine Networks

This article deals with the thermal oxidation mechanisms and kinetics of epoxy-diamine (EPO-DA) networks used as composite matrices reinforced with carbon fibers in the aeronautical field. The first part of this article is devoted to a detailed presentation of the new analytical kinetic model. The so-called “closed-loop” mechanistic scheme, developed in the last 3 decades in our laboratory in order to accurately describe the thermal oxidation kinetics of saturated hydrocarbon polymers, is recalled. Its main characteristics are also briefly recalled. Then, the system of differential equations derived from this oxidation mechanism is analytically solved without resorting to the usual simplifying assumptions that seriously degrade the reliability of all kinetic models. On the contrary, the generalization of the proportionalities observed between the steady concentrations of the different reactive species (i.e., hydroperoxides and alkyl and peroxy radicals) to the entire course of thermal oxidation gives a series of much sounder equations. From this basis, the kinetic model is completed by considering new structure/property relationships in order to predict the consequences of thermal oxidation on the thermomechanical properties, in particular on the glass transition temperature (Tg). To reach this second objective, the two main mechanisms responsible for the alteration of the macromolecular network structure are recalled: chain scissions and crosslinking. Like any other chemical species, their kinetics are directly expressed from the oxidation mechanistic scheme using the classical concepts of chemical kinetics. The second part of this article is devoted to the checking of the kinetic model reliability. It is shown that this latter accurately simulates the experimental curves of carbonyl build-up and Tg decrease versus time of exposure determined in our laboratory for three EPO-DA networks under study, exposed in a wide variety of thermal oxidative environments. The values determined by inverse solving method for the different model parameters are discussed and their temperature dependence are elucidated. Finally, an end-of-life criterion is proposed for predicting the lifetime of EPO-DA networks involving a predominant chain scission process.

Phosvitin-wheat gluten complex catalyzed by transglutaminase in the presence of Na2SO3: Formation, cross-link behavior and emulsifying properties

Phosvitin (PSV) is considered as a good emulsifier, although it has a low proportion of hydrophobic regions and steric hindrance. Wheat gluten (WG) possesses excellent hydrophobicity and macromolecular network structure. In this work, WG was subjected to a series of Na2SO3 solution, followed by cross-linking with PSV under transglutaminase (TGase) catalyzation. The results showed that Na2SO3 could break disulfide bonds of WG and increase its solubility from 7.33% to 42.82% with 1200 mg/L of Na2SO3. Correspondingly, the cross-linking degree was significantly enhanced. Compared to PSV, the cross-linked PSV-WG exhibited a higher surface hydrophobicity and thermal stability, with a lower zeta potential and apparent viscosity. The emulsifying activity of PSV-WG reached 17.42, 20.63 and 20.28 m2/g with Na2SO3 concentration of 300, 600 and 900 mg/L, which were all higher than that of PSV (15.19 m2/g). This work provided a novel strategy to elevate emulsifying properties of PSV by cross-link reaction.

Experimental investigation on the effect of organic solvents on gas development of coalbed methane reservoir

CBM reservoirs are extremely vulnerable to damage due to their complex pore structure. So, changing pore structures in CBM reservoirs is of vital importance for reducing reservoirs damage. Organic solvents have been considered as additives into fracturing fluids to enhance production because they can enhance the pore connectivity and loosening macromolecular network structure. It is thus of great interests to investigate how organic solvents (ethanol and ethylene glycol ether) change micropore structures and fluid distribution. In this study, samples were selected from different wells completed in No. 3 coal seam, Zhaozhuang minefield. Low-pressure nitrogen adsorption (LP-N2GA) experiments were conducted on coal samples to evaluate the changes in pore-structure parameters including specific surface area (SSA), pore diameter, and pore volume. NMR experiments were conducted on coal samples to evaluate the changes in fluid distribution. Analyzing the LP-N2GA results suggests ethylene glycol ether and ethanol can effectively increase SSA, pore diameter, and opening degree of pores in coal samples. Comparative analysis of NMR results indicates that ethylene glycol ether consistently reduces the irreducible water saturation (Swir) in samples. The average value of Swir of raw samples is 0.8670 and the average value of Swir of samples treated with ethylene glycol ether value is 0.7644. Considering the pore-structure alterations, this study demonstrates that ethylene glycol ether is more preferable for enhancing recovery from CBM reservoirs compared with ethanol.

A hydrogel-based in vitro assay for the fast prediction of antibiotic accumulation in Gram-negative bacteria.

The pipeline of antibiotics has been for decades on an alarmingly low level. Considering the steadily emerging antibiotic resistance, novel tools are needed for early and easy identification of effective anti-infective compounds. In Gram-negative bacteria, the uptake of anti-infectives is especially limited. We here present a surprisingly simple in vitro model of the Gram-negative bacterial envelope, based on 20% (w/v) potato starch gel, printed on polycarbonate 96-well filter membranes. Rapid permeability measurements across this polysaccharide hydrogel allowed to correctly predict either high or low accumulation for all 16 tested anti-infectives in living Escherichia coli. Freeze-fracture TEM supports that the macromolecular network structure of the starch hydrogel may represent a useful surrogate of the Gram-negative bacterial envelope. A random forest analysis of in vitro data revealed molecular mass, minimum projection area, and rigidity as the most critical physicochemical parameters for hydrogel permeability, in agreement with reported structural features needed for uptake into Gram-negative bacteria. Correlating our dataset of 27 antibiotics from different structural classes to reported MIC values of nine clinically relevant pathogens allowed to distinguish active from nonactive compounds based on their low in vitro permeability specifically for Gram-negatives. The model may help to identify poorly permeable antimicrobial candidates before testing them on living bacteria.

Oxidation of Zhundong subbituminous coal by Fe2+/H2O2 system under mild conditions

Oxidation of coal under mild conditions is effective not only to understand the macromolecular network structure of coal but also to produce useful chemicals, allowing more efficient application of coal resources. In this work, the mild oxidation of Zhundong subbituminous coal (ZS) by Fe2+/H2O2 system was carried out under various conditions, including [Fe2+]/[H2O2] molar ratio, temperature, H2O2 concentration and oxidation time. The liquid oxidation products were analyzed using gas chromatography/mass spectrometry (GC/MS), and the chemical structure changes were studied using Fourier transform infrared spectroscopy (FTIR). The results suggest that the oxidation efficiency of ZS with H2O2 is enhanced with the aid of Fe2+. The optimum conditions were determined to be [Fe2+]/[H2O2] molar ratio of 0.00453, H2O2 concentration of 3mol/L, 60 oC and 4 h according to the oxidation conversion rate. In total, 25 compounds were identified, which could be categorized as six group components. Most of them are valuedadded chemicals, and the content of benzene carboxylic acids is the highest among them, making up 29.99% of all group components in total relative content (TRC). -CH2- should be primary bridge connecting the aromatic rings, and alkylene chains linking three aromatic rings are abundant in ZS.

Synergistic Extraction and Characterization of Fulvic Acid by Microwave and Hydrogen Peroxide-Glacial Acetic Acid to Oxidize Low-Rank Lignite.

Fulvic acid (FA) has important properties and is used widely in agriculture, industry, medicine, and other fields. However, there is a lack of environmentally friendly and efficient extraction methods for coal-based FA and its molecular structural characterization. In this study, FA was extracted cleanly and efficiently from low-rank lignite via the innovative method of microwave combined with hydrogen peroxide and glacial acetic acid, followed by purification by the sulfuric acid–acetone method. The molecular structures of FA were precisely characterized by UV–vis spectroscopy, infrared (IR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography–mass spectrometry (GC–MS). The results showed that the microwave combined with hydrogen peroxide–glacial acetic acid method had stronger oxidative degradation ability compared with the conventional method. Under optimized conditions, the yield of FA reached 60.97%. During the oxidation process, the macromolecular network structure of coal was destroyed, resulting in the production of many oxygen-containing functional groups. According to the IR and UV–vis spectra, there were abundant oxygen-containing functional groups such as hydroxyl, carboxyl, carbonyl, and quinone groups in the molecular structure of FA. Determination of the total acid group content in the oxygen-containing functional groups of FA showed that the content of carboxyl groups was much higher than that of phenolic hydroxyl groups. The 1H NMR showed that there were hydrogen atoms present as part of carboxyl, aromatic, phenolic hydroxyl, and aliphatic groups in FA. The (GC–MS) results suggested that FA is a mixture of dozens of complex compounds, including alkanes, alcohols, esters, etc.

Controlling mechanism of coal chemical structure on biological gas production characteristics

To find the effect of coal chemical structure on biogas production, Lignite B was collected and extracted with nitrogen methylpyrrolidone (NMP), acetone and 0.60 mol/L NaOH. Simultaneously, methanogenic bacteria were enriched, and gas production experiments involving solvent extraction from residual coal and secondary gas production experiments involving coal were performed. The characteristics of biogas production, microcrystalline structure and coal chemical structure were analyzed. The results showed that the biogas production capacity of residual coal extracted by different solvents differed. The biogas production capacity of residual coal extracted by 0.60 mol/L NaOH was severely inhibited. The biogas production capacity of residual coal extracted by NMP and acetone was enhanced compared with that of raw coal. In contrast, primary residual coal still exhibits potential for methane production, but the methane production efficiency was reduced. Changes in the microcrystalline structure and functional groups of residual coal showed that solvent extraction increases the spacing and stacking height of the aromatic lamellae of coal, reduces the hydroxyl, methyl, methylene and aromatic hydrocarbon levels in coal, loosens the macromolecular network structure of coal, and enhances the connectivity of pores and fissures, thus allowing methane-producing bacteria to enter the coal mass and create favorable conditions for gas production through interactions between the two. X-ray photoelectron spectroscopy measurements showed that the secondary gas production increased the C content on the coal surface, decreased the O content and the O/C ratio, thus promoting the consumption of oxygen-containing functional groups on the coal surface to further produce gas.