Contents Of Hydroxyl Research Articles

Achievement of biochar photocatalytic performance by synergistic oxidation of sulfuric acid/hydrogen peroxide: Towards revealing the mechanism of synergistic oxidation on photocatalytic performance

The oxygen-containing functional groups of biochar have great potential in tailoring photochemical properties, but the content of oxygen-containing functional groups of pristine biochar is insufficient to support photocatalytic reactions. In this study, a synergistic oxidation of H2SO4 and H2O2 was innovatively proposed to prepare biochar photocatalysts (OGPC400). The results showed that the synergistic oxidation of H2SO4 and H2O2 increased the contents of hydroxyl and carboxyl groups of biochar with the degree of oxidation, and the total concentration of acidic functional groups was about 4 mmol/g higher than that of the oxidation with H2SO4 or H2O2 alone, which was attributed to the synergistic oxidation to promote the conversion of CH and C-OH on the benzene ring. The achievement of electron exchange among hydroxyl and carboxyl groups and internal electron transfer within biochar by the benzene ring as a medium resulted in 100 % degradation of rhodamine b (RhB) and 25 times reaction rate constant higher than that of pristine biochar, as compared to only 45 % or 37 % degradation by oxidation with H2SO4 or H2O2 alone. The exciting results confirmed the positive availability of H2SO4 and H2O2 synergistic oxidation on biochar photocatalysts, which is expected to be applied in environmental remediation.

Pore Morphology and Oxidation Behaviour of Deep-Loaded Granular Coal at High Initial Temperatures

ABSTRACT As coal mining proceeds deeper, fragmented coal is subjected to high geostress and elevated thermal environments, causing changes in its micro-physical properties and spontaneous combustion (SC) risks. Deep mining operations entail significant risks of coal fires. In order to investigate the effects of high stress and high thermal environments on the microstructural and physicochemical damage of fragmented coal, and to elucidate the mechanisms influencing oxidation behavior, we conducted experiments including low-temperature nitrogen adsorption, synchronous thermal analysis, and in-situ diffuse reflectance spectroscopy. These experiments aimed to explore the pore morphology and oxidation characteristics of high initial temperature unloading granular coal (HITU-GC) unloading conditions. The results indicate that with increasing initial temperature, characteristic point temperatures initially rise and then decrease, while both the mass loss and heat release during the low-temperature oxidation stage decrease. After pressure-unloading composite treatment, the oxidation process accelerates with more intense reactions, resulting in an overall increase in heat release. The pore shapes of HITU-GC show no significant difference compared to the original coal, mainly comprising non-rigid aggregates of micropores, platy or layered matrix particles, including numerous slit-shaped pores. The coal surface also exhibits ink bottle-shaped pores and cone-shaped pores. Higher pre-oxidation temperatures correlate with higher specific surface areas. Higher stress levels from pressurized unloading correlate with lower specific surface areas. The specific surface area of sample O60-P16 is reduced by 0.879 m2/g compared to sample O60-P0. Pressurized unloading treatment disrupts mesoporous pores. Following thermal environment and pressure-unloading, the coal’s aromatic hydrocarbon content decreases, while the contents of hydroxyl, aliphatic hydrocarbons, and oxygen-containing functional groups (FG) all increase. Sample O60-P4 shows the highest content of active FG. While thermal environments enhance coal oxidation activity, pressure-unloading treatment increases the extent of coal surface fragmentation. The synergistic effect of both significantly increases the SC risk of coal. This study provides a theoretical basis for controlling thermal hazards associated with high-initial-temperature unloading fragmented coal in deep goaf areas.

Experimental study on the mechanism of coal spontaneous combustion inhibition by degradation of white-rot fungus

To investigate the mechanism of inhibition of spontaneous combustion of coal by degradation of white-rot fungus, the changes of macroscopic oxidizing characteristics and microstructure of the degraded coal were investigated by the programmed temperature-raising test and the in situ Fourier-transform infrared spectroscopy experiments. The difference in gas production between the degraded coal and the blank samples indicated that the degradation inhibited the oxidation process of coal, and the intensity of the inhibition effect was different at different oxidation stages. The strongest inhibition effect was found in the accelerated oxidation stage, i.e. 80–140 °C. To further analyze the micro-mechanism of the degradation of Phanerochaete chrysosporium affecting the spontaneous combustion of coal, the relative contents of active functional groups in coal samples were compared. The results showed that the degradation affected the relative contents of hydroxyl, aliphatic hydrocarbon, and oxygenated functional groups in coal. Among them, the most significant changes of –OH and –CO- were observed at 80–140 °C. Thus, it was analyzed that Phanerochaete chrysosporium could degrade the macromolecular structure of coal by generating biological enzymes to reduce the number of oxidizable functional groups such as –OH, –CH2, –CH3, –CO-, and so on, thus reducing the risk of spontaneous combustion of coal.

Effects of oxygen loading on the red-luminescence of non-bridging oxygen hole centers in γ-irradiated silica glasses

Ultra-high purity Corning 7980 and Corning 7979 silica glasses, respectively with high and low contents of hydroxyl and hydrogen, were specifically selected to investigate the effects of O2 loading on the 1.9 eV red luminescence of the gamma-ray induced non-bridging oxygen hole center (NBOHC), whose luminescence intensity is beneficial not only to predict the laser damage of silica but also to the targeted improvements in the preparation-treatment processes of silica. The UV trasmittance spectra, the UV excitation spectra, the visible emission spectra and the red emission lifetime decay curves were determined for these two types of the gamma-ray irradiated silica glasses before and after O2 loading. The content ratios of Si dangling bond (Si-E′) to NBOHC in silica glasses before and after O2 loading are estimated. The formation precursors and other related defects for NBOHC, such as Si-E′, Si-O-Si bond, Si-O-H bond, peroxy radical and linkage, oxygen-deficient centers ODC(I) and ODC(II), etc, are discussed. The bandwidths of the excitation and emission spectra before and after O2 loading are compared at the lower energy side of the spectra. The average emission lifetimes and especially the decay curves of the red luminescence before and after O2 loading are analyzed. There appear two types of NBOHCs with and without neighbouring hydrogen interaction at room temperature, respectively corresponding to the shorter and longer lifetime components. After O2 loading, the shorter lifetime component disappears and becomes the longer one, indicating that the hydrogen-bonded NBOHC is altered into the non-bonded. It is suggested that the analysis of the shorter and longer lifetime components of the red luminescence can be utilized in the laser damage prediction as well as the preparation and treatment processes of silica.

Study on the influence of different-voltage plasma breakdowns on functional group structures in coal

Promoting gas desorption is the key to improving gas extraction efficiency, physical discharge-based plasma carries massive joule heat, and inevitably affects the structures of functional groups in coal, which has a certain impact on the adsorption and desorption of gas, but existing literature lacks in-depth research on this. This study explores the changes of functional groups on GHS high metamorphic anthracite and HL low metamorphic bituminous coal samples under different breakdown voltages (BVs), from 15.3 kV to 17.3 kV, which serves as the key to determining the amount of energy injected into plasma channels. This study also explains the influence of BV on functional groups in coal from the perspective of electrical parameters such as voltage, current waveform and deposited energy. For two kinds of coal samples, the results reveal the following: (1) With the breakdown voltage increases, the coal is more likely to be polarized and the pre-breakdown period is shorter; accordingly, the coal can be broken down more easily. (2) The peak current increases linearly with the rise of BV, and the energy conversion efficiency jumps first and then tends to stabilize; (3) The plasma-induced oxidation reaction degree of the coal surface gradually strengthens as the BV rises, because more energy is used for reactions on the coal surface. Specifically, the higher the BV is, the faster the contents of hydroxyl and oxygen-containing functional groups decline, and the faster the aliphatic hydrocarbons in the coal decompose.

A functional lignin for heavy metal ions adsorption and wound care dressing

Recently, the application of lignin activation by demethylation to improve reactivity and enrich multiple functions has intensively attracted attention. However, it is still challenge up to now due to the low reactivity and complexity of lignin structure. Here, an effective demethylation way was explored by microwave-assisted method for substantially enhancing the hydroxyl (-OH) content and retaining the structure of lignin. Then, the optimum demethylated lignin was used to removal heavy metal ions and promote wound healing, respectively. In detail, for microwave-assisted demethylated poplar lignin (M-DPOL), the contents of phenolic (Ar-OH) and total hydroxyl (Tot-OH) groups reached the maximum for 60 min at 90 °C in DMF with 7.38 and 9.13 mmol/g, respectively. After demethylation, with this M-DPOL as lignin-based adsorbent, the maximum adsorption capacity (Qmax) for Pb2+ ions reached 104.16 mg/g. Based on the isotherm, kinetic and thermodynamic models analyses, the chemisorption occurred in monolayer on the surface of M-DPOL, and all adsorption processes were endothermic and spontaneous. Meanwhile, M-DPOL as a wound dressing had excellent antioxidant property, outstanding bactericidal activity and remarkable biocompatibility, suggesting that it did not interfere with cell proliferation. Besides, the wounded rats treated with M-DPOL significantly promoted its formation of re-epithelialization and wound healing of full-thickness skin defects. Overall, microwave-assisted method of demethylated lignin can offer great advantages for heavy metal ions removal and wound care dressing, which facilitates high value application of lignin.

Nanolignin-based high internal phase emulsions for efficient protection of curcumin against UV degradation

As an emulsifier, lignin exhibits excellent UV resistance on drug-loaded emulsion systems for drug delivery. However, due to the structural variation and complexity of lignins from various origins, their UV shielding performance varies with the techniques for lignin extraction, which impacts properties and the protection efficiency of lignin-based HIPEs (high internal phase emulsions). In this work, lignin nanoparticles, prepared from three lignin preparations of Eucalyptus, were used in HIPEs delivery systems to protect curcumin from degradation by UV radiation. Structures of the lignin preparations were characterized using 2D HSQC (heteronuclear single-quantum coherence) NMR (nuclear magnetic resonance), 31P NMR, and GPC (gel permeation chromatography). The residual curcumin level after 36 h UV exposure in the nanolignin-based HIPEs was over 72 %, much higher than that (< 10 % after 24 h UV exposure) in the oil phase without lignin, indicating that the nanolignin-based HIPEs with enhanced UV shielding ability protect curcumin better. Of the three lignin preparations, AL (alkali lignin), with the lowest molecular weight, highest contents of phenolic hydroxyl and carboxyl groups, and highest S/G ratio, displayed the best anti-UV radiation ability and the most uniform nanoparticle size.

Simultaneous strengthening and toughening lignin/cellulose nanofibril composite films: Effects from flexible hydrogen bonds

Inspired by the lignin-cellulose network in natural wood, we developed a strategy to produce cellulose nanofibril (CNF) composite films using lignin nanoparticles (LNPs) with varied contents of phenolic hydroxyl (Ph-OH) groups as a reinforcing agent. Regulated LNPs with lower molecular weight, higher Ph-OH content, and uniform morphology were successfully prepared by phenolation and anti-solvent precipitation. CNFs mixed with phenolated LNPs of high Ph-OH content (8.23 mmol/g) exhibited a higher tensile strength (∼190 MPa), increased toughness (∼15 MJ/m3), and enhanced UV-blocking ability (∼99 %) compared to lignin-free CNFs and CNF composites with lower Ph-OH content. Thus, hydrogen bonds between Ph-OH groups on lignin and hydroxyl groups on CNFs are vital for enhancing the mechanical strength of composite films. Similar enhanced mechanical properties were found by adding phenolated LNPs into polyvinyl alcohol as a fortifier. This study provides novel insights into producing lignin-reinforced cellulose composite films with UV shielding, thermal stability, and biodegradability.

Room-temperature hydrogen storage performance of metal-organic framework/graphene oxide composites by molecular simulations

Metal-organic framework/graphene oxide (MOF/GO) composites have been regarded as potential room-temperature hydrogen storage materials recently. In this work, the influence of MOF structural properties, GO functional group contents and different amounts of doped lithium (Li+) on hydrogen storage performance of different MOF/GO composites were investigated by grand canonical Monte Carlo (GCMC) simulations. It is found that MOF/GO composites based on small-pore MOFs exhibit enhanced hydrogen storage capacity, whereas MOF/GO based on large-pore MOFs show decreased hydrogen storage capacity, which can be ascribed to the novel pores at MOF/GO interface that favors the enhanced hydrogen storage performance due to the increased pore volume/surface area. By integrating the small-pore MOF-1 with GO, the hydrogen storage capacity was enhanced from 9.88 mg/go up to 11.48 mg/g. However, the interfacial pores are smaller compared with those in large-pore MOFs, resulting in significantly reduced pore volume/surface area as well as hydrogen storage capacities of large-pore MOF/GO composite. Moreover, with the increased contents of hydroxyl, epoxy groups as well as carboxyl group modification, the pore volumes and specific surface areas of MOF/GO are decreased, resulting in reduced hydrogen storage performance. Furthermore, the room-temperature hydrogen storage capacities of Li+ doped MOF/GO was improved with increased Li+ at low loading and decrease with the increased Li+ amounts at high loading. This is due to that the introduced Li+ effectively increases the accessible hydrogen adsorption sites at low Li+ loading, which eventually favors the hydrogen adsorption capacity. However, high Li+ loading causes ion aggregation that reduces the accessible hydrogen adsorption sites, leading to decreased hydrogen storage capacities. MOF-5/GO composites with moderate Li+ doping achieved the optimum hydrogen storage capacities of approximately 29 mg/g.

Effects of ultrasound-assisted Fenton treatment on structure and hypolipidemic activity of apricot polysaccharides

In order to improve the hypolipidemic activity of apricot polysaccharide, the methods of modifying polysaccharide were preliminarily screened, and the modification process conditions were further optimized by response surface methodology. Subsequently, the structure characterization and hypolipidemic activity of polysaccharide obtained by ultrasound-assisted Fenton treatment (EAP-UF) were studied. The results of Box-Behnken design indicated that under the optimal conditions of ultrasound-assisted Fenton degradation, the binding rate of sodium taurocholate and sodium glycocholate were 62.10% and 59.87%, respectively. Furthermore, the molecular weight, particle size, PDI value and roughness of EAP-UF decreased obviously, while the contents of hydroxyl, carbonyl carboxyl and rhamnose increased obviously. What's more, EAP-UF could significantly reduce the content of fat accumulation, triglyceride and total cholesterol in Caenorhabditis elegans. Taken together, ultrasound-assisted Fenton treatment is an effective method to enhance the hypolipidemic activity of polysaccharides.

Effect of Oxygen-Containing Groups on Electrochemical and Marine Electric Field Response Properties of Carbon Fiber Electrode

Electric field response of carbon fiber sensor in sea water can be tuned up through modification of molecules or groups on its surface, which plays an important role in its high sensitivity and stability. Herein, high performance carbon fiber electrodes with different oxygen-containing functional groups were prepared by electrochemical oxidation coupled with electrochemical reduction, and their electric field response and electrochemical performances of electrodes are investigated. The results show that the electrochemical oxidation and reduction obviously alter the dominant contents of carbonyl, hydroxyl and carboxyl groups. Among them, carbonyl group has positive effects for paired carbon fiber electrode on its electrode potential stability and its distortion rate of electric field response curves, hydroxyl group makes the paired carbon fiber electrode more sensitive to weak electric field. Carboxyl group has negative effects on the electrode potential stability due to its high activity, but its larger specific capacitance and smaller charge transfer resistance are simultaneously obtained. The detailed relationship between the dominant oxygen-containing carbon fiber electrode and its electric field response is first reported systematically, and it will shed some light on the design of fast-stable and highly sensitive marine electric field electrodes.

Study on gas production mechanism of medium- and low-rank coals excited by the external DC electric field

This study aims to further explain abnormal phenomena occurring during coal and gas outbursts and grasp the gas production effect of the micro-structure on outburst coal surface under the action of the electric field. To this end, in this study, an experimental system for gas production of coal excited by the external DC electric field was established. Then, gas production experiments were performed on medium- and low-rank coals excited by the different-strength electric fields to reveal the relationships between gas production and coal rank and excitation voltage. Subsequently, the variations of functional groups and chemical bonds on coal sample surface after the external DC electric field excitation (EFE) were measured and analyzed through Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). According to the results of the gas production experiment, gases produced by medium- and low-rank coals under EFE include CH4, CO and CO2, and the gas production volume rises with the increase in excitation voltage. The results of FTIR analysis show that the contents of hydroxyl, aliphatic hydrocarbons and oxygen-containing functional groups of medium- and low-rank coals decrease to varying extents after EFE. The results of XPS analysis disclose that the structure of C element on the surface of medium- and low-rank coals changes after EFE. Therefore, the CO, CH4 and CO2 produced by medium- and low-rank coals during EFE come from the breakage of chemical bonds and the falling-off of functional groups. The research results provide theoretical support for revealing the mechanism of coal rock dynamic disasters and exploring methods for the monitoring and pre-warning of these disasters.

Influence of torrefaction on yields and characteristics of densified solid biofuel

Torrefaction is a mild thermal pretreatment for enhancing the combustion property of biomass to be properly applied to biomass or co-firing power plants. The present research investigated mass yields, fuel characteristics and hydrophobicity of rubber wood pellet torrefied at different temperatures and residence times. Proximate and ultimate analyses, the enhancement factor of higher heating value, energy yield, lignocellulosic components and Fourier transform infrared spectroscopy (FT-IR) of torrefied samples were performed to evaluate the influence of the process parameters and compared to those of the untreated ones. The non-condensable and condensable products were analyzed by GC and GC-MS. The results showed that the torrefaction severity index (TSI) correlated sufficiently with the properties of torrefied biomass and was more sensitive to torrefaction temperature than residence time. The increase in the TSI value resulted in an increase in heating value but a decrease in energy yield. The energy density increased by 14% at 260 °C and reached up to 35% at torrefaction temperature of 300 °C. FT-IR analysis revealed that the contents of hydroxyl and carbonyl groups appeared in torrefied wood pellets were decreased and increased, respectively, due to the torrefaction process. Furthermore, the hydrophobicity of torrefied pellets can be significantly improved as torrefaction temperature increases. The non-condensable gaseous products were mostly composed of CO2, CO, and traces of CH4. While the organic compounds found in condensable liquid products were acids, ketones, furans and phenols.

First-principles realistic prediction of gas adsorption on two-dimensional Vanadium Carbide (MXene)

Gas adsorption capability of some polar and nonpolar analytes on the surface of the two-dimensional, 2D, V2CTx MXene is investigated using first-principles density functional calculations. Also, the effects of surface functionalization on the electronic properties and gas adsorption of V2C MXene are discussed. Results show that, oxygen and hydroxyl surface groups as the main contributors provide the active sites for gas adsorption. Released adsorption energy suggests that gas sensor capability of the V2CTx MXenes can be enhanced in the presence of water molecule as well as high (low) contents of oxygen and hydroxyl (fluorine) surface functional groups. Among the studied analytes, the V2CTx with all three surface termination contents shows the highest response toward the CH3NH2. Remarkably the V2C(OH)0.33F0.05O0.61 plus H2O molecule, S3, can interact chemically (physically) with the H2 (CH4) gas molecule. Furthermore, C2H5OH, C3H6O and CH3OH analytes are adsorbed physically on the MXene with all three surface contents. Remarkably, the S3 exhibits the lowest and highest work function, when the H2 and H2S molecules are absorbed, respectively. The numerical results may be useful to engineer and design gas sensors and nano-devices based on 2D MXenes.

Effect and Mechanism of Microwave Heating on the Functional Properties of Whey Protein Isolate

In this study, maillard reaction was used to modify whey protein isolate (WPI) with microwave assistance. The effects of microwave power, microwave heating time, pH, and mass ratio of lactose to whey powder on the functional properties of whey protein maillard reaction products (WPI-MRPs) were systematically investigated by using emulsification and antioxidant activity as the main indexes. The process was optimized, the secondary structure and amino acid composition during microwave treatment were also analyzed in details. The optimized microwave heating conditions are as follows: pH8.5, whey protein-lactose mass ratio 5:5, microwave heating time 7 min. The emulsification activity index, emulsifying stability index and DPPH free radical scavenging rate of the obtained MRPs was 0.35 m2/g, 88.39 min and 6.60%, respectively. The infrared spectroscopy data indicated that microwave heating could promote the maillard reaction process, during the process increases in the contents of hydroxyl and carbonyl groups were observed, and complex maillard intermediates and aldehydes and ketones were produced. Meanwhile, transformation of the protein secondary structure from a compact to a loose “swelling” structure could be also promoted. During the transformation, most of the tightly ordered structure firstly transforms into a loosely ordered structure, and then into a loosely disordered state, accompanied by a small part of the tight ordered structure changed to each other after a long time heating. In addition, amino acid analysis further confirmed that the reaction would result in a decrease in total amino acids content due to participation of free amino acids in WPI during maillard reaction.

Study on pyrolysis characteristics of lump coal in the context of underground coal gasification

Coal reaction in dry distillation zone, as an essential step in underground coal gasification (UCG), is of great significance to be studied about its characteristics in a comprehensive way. This study simulated the pyrolysis process of lump coal in UCG tunnel in a laboratory. Lump coal samples were heated in nitrogen environment at 200–600 °C. The functional groups, pore structure, and microcrystalline structure of coal samples were analyzed by Fourier transform infrared spectrometer, scanning electron microscope, and X-ray diffractometer. The results showed that, as final pyrolysis temperature increased, the contents of hydroxyl, aliphatic, and aromatic groups all showed decreasing trends. The escalation of CHar/CC and CH2/CH3 implied that the condensation degree of aromatic structure and the branching degree of fatty chain increased. With the temperature increasing, volatile substances such as CO2 and CH4 were released. Coal samples had higher porosity and gradually turned hollowed. The d002 (Interlinear Spacing of Microcrystalline) of the coal sample decreased, Lc (final stacking height) increased and Lc/d002 (stacking layer numbers) decreased, indicating that the crystal structure of coal samples tended to be more disordered.

Preparation of hydrochar with high adsorption performance for methylene blue by co-hydrothermal carbonization of polyvinyl chloride and bamboo

Polyvinyl chloride (PVC) was blended into bamboo powder during co-hydrothermal carbonization (Co-HTC) to understand the effects on the physicochemical properties and adsorbing ability of hydrochar. The properties of hydrochar were characterized by Zeta potential, elemental analyses, BET, FTIR, XPS, Boehm titration and SEM. The addition of PVC into bamboo in Co-HTC decreased the BET area, and pore volume and radius of hydrochar, but increased the contents of surface hydroxyl and carboxyl groups. The adsorption ability of hydrochar produced by addition of PVC at 473 K over methylene blue (MB) increased significantly. The main adsorption mechanism was electrostatic attraction by –N(CH3)2+ of MB and carboxylate of hydrochar, and hydrogen-bonding interaction through N atom of phenothiazine in MB and C–OH of hydrochar. Thus, Co-HTC offers a facile, green and economical alternative for conversion of waste into high-value adsorbents.

Evaluation of the spontaneous combustion of soaked coal based on a temperature-programmed test system and in-situ FTIR

To explore the influence of long-term water immersion on the spontaneous combustion characteristics of coal, temperature-programmed test system and In-situ Fourier transform infrared spectroscopy (In-situ FTIR) were used. Differences in gas production of soaked coal and raw coal showed that the process of long-term water immersion played a different role before and after critical temperature. In the stage of surface oxidation, moisture could inhibit the spontaneous combustion of coal, when the critical temperature point was exceeded, it played a promoting role instead. As an explanation in support of the above arguments, the relative contents of active functional groups in raw and soaked coal were compared, which indicated that the process of water immersion could affect relative contents of hydroxyl, aromatic hydrocarbon, aliphatic hydrocarbon and oxygen-containing functional groups, giving rise to an acceleration in the reaction process of coal oxygen and exhibiting higher tendencies toward spontaneous combustion. A practical consequence of this finding is the soaking mechanism should not be neglected in any precautionary or preventive measures to avoid potential spontaneous combustion in overlying goaf of shallowly buried and close distance coal seams.

Comparative studies on lignin structures in normal and tension wood of Populus × euramericana cv. “74/76”

Tension wood is a type of defect of wood, however, it has some especial character and structure. In this study, cellulase lignin structures in normal and tension wood of Poplar 107 (Populus × euramericana cv. ‘74/76’) were compared using ultraviolet (UV), Fourier transform infrared (FT-IR), Raman and magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and elemental analysis. The results showed that the lignins in both normal and tension wood were dominated by syringyl units, followed by guaiacyl and p-hydroxyphenyl units. The FT-IR result presented that the relative intensity of syringyl units in normal and tension wood were 0.87 and 0.90. The contents of aliphatic hydroxyl, methoxyl, condensed phenolic hydroxyl and carboxyl of lignin in tension wood were higher than those of phenolic hydroxyl groups and β-5. The contents of β-O-4, β-β and β-1 in tension wood were similar with those in normal wood. The average per-C9-unit formulae of the lignin in normal and tension wood of Poplar 107 were C9H7.21O1.79 (OH)1.17_x0001_(OCH3)1.55 and C9H7.23O1.76(OH)1.25_x0001_(OCH3)1.62, respectively.

Synergistic Inhibitory Effect of Free Radical Scavenger/Inorganic Salt Compound Inhibitor on Spontaneous Combustion of Coal

ABSTRACT From the aspects of isolating oxygen, lowering temperature and terminating free radical chain reaction, an inorganic salt inhibitor and a radical scavenger were combined to form a compound inhibitor for preventing of coal spontaneous combustion. A long-flame coal with easy self-ignition was chosen to study the inhibitory performance of different inhibitors using inhibition performance tests and by characterizing reactive functional groups and performing thermal analysis. The experimental results show that the compound inhibitor has a coordinated inhibitory effect throughout the whole process of coal spontaneous combustion, with physical and chemical double inhibition effect. Compared with the raw coal, the amount of CO released from the coal sample treated by the compound inhibitor was reduced by 88.7% at 128°C, and the inhibition rate reached 82.5% at 100°C. The inhibition ratio is higher than 80% during the initial weight loss stage and the oxygen absorption and weight increase stage. The compound inhibitor plays an inhibitory role by reducing the contents of hydroxyl, methyl, methylene groups and active components containing carbonyl groups in the coal, wherein, the relative content of a carbonyl compounds decreased obviously. During the initial weight loss stage, the water retention due to inorganic salts physically isolated oxygen and cooled the coal. During the oxygen adsorption and mass gain stage, free radicals were released from the compound inhibitor and captured both oxygen free radicals and carbon free radicals via chemical inhibition. N,N-Dibenzylhydroxylamine (DBHA) contains multiple absorption sites that can simultaneously capture multiple free radicals in coal. Butylated hydroxyl toluene (BHT) reacts with free oxygen-containing functional groups to form stable compounds, which interrupts the formation paths for ketones and aldehydes. Moreover, the inhibition mechanism of the compound inhibitor on coal spontaneous combustion was also explored.