Spontaneous Tendency Research Articles

Re-directing nanomedicines to the spleen: A potential technology for peripheral immunomodulation.

Modulation of peripheral immune cells in the spleen plays a key role in many life-threatening conditions such as stroke. Immune cell changes can lead to the excessive release of pro-inflammatory cytokines into the circulation and preferential loss of innate immune cells which can further exacerbate tissue damage and predispose patients to infectious complications. Reversing these processes represents an attractive treatment strategy and has shown to have beneficial effects in animal models of ischemic stroke, sepsis, traumatic brain injury (TBI) as well as myocardial infraction (MI). However, systemic interventions are often challenging to deliver due to the non-selective broad range of action of many treatments. More selective targeted treatment approaches are therefore desirable. The spleen is considered a natural filtration site for many nanomaterials due to the spontaneous tendency of this organ to filter blood-borne molecules. This selective targeting of nanomaterials to the spleen therefore offers considerable potential in the management of many conditions affected by peripheral inflammation. In this review, we will explore the key nanomaterials-related parameters that mediate splenic targeting and how these could influence the actual localization and function of nanomaterials once in the spleen. We aim to emphasize the potential of utilising nanomaterials as selective tools for peripheral immunomodulation to accelerate clinical translation.

Interaction Study of Oxygen and Iron-Sulfur Clusters Based on the Density Functional Theory

For the petrochemical industry, the spontaneous burning of iron sulfide compounds has been a major issue. In this study, XRD characterization of samples of iron sulfide compounds with spontaneous combustion tendency revealed that amorphous FeS was the primary constituent of the samples. A molecular simulation was used to build an amorphous FeS cluster model, and the density functional theory was used to examine the adsorption and reactivity characteristics of Fe4S4 clusters with O2. Different adsorption structures are generated by considering different adsorption sites and the electronic characteristics of each adsorption structure are evaluated. The results show that O2 prefers to adsorb around Fe atoms and has repulsion with S atoms, and the adsorption energy is maximum when two O atoms are co-adsorbed around Fe atoms, which is 198.13 kJ/mol. After adsorption charge, oxygen is in the superoxide state. The calculation of the reaction path divides the reaction process into different stages and considers different reaction routes. A thorough evaluation of the energy barriers and reaction energies of the two exothermic reactions leads to the conclusion that reaction path 1 is the optimal reaction path, and the reaction can release a total of 582.76 kJ/mol of heat. According to calculations, dimeric sulfur S2 must absorb a large part amount of energy in order to conduct the oxidation process. However, because S2 is present in the Fe4S4 reaction system, it may start the oxidation reaction by absorbing heat from the system and releasing 470.94 kJ/mol of heat. As a result, we conclude that this spontaneous exothermic reaction is a major cause of iron sulfide compounds spontaneous combustion. The thermal oxidation of the dimeric sulfur S2 generated in the reaction system releases heat that aggregates with the heat from the Fe4S4 cluster’s oxidation reaction system, eventually causing spontaneous combustion as a result of the heat’s continual buildup. In this study, we explore the reason for the extremely easy oxidation and spontaneous burning of iron sulfide compounds from a microscopic perspective to provide a theoretical foundation for the prevention and control of iron sulfide compound spontaneous combustion in the petrochemical sector.

Study on the combustion characteristics of bituminous coal modified by typical inorganic acids

Acid fracturing technology is applied to increase the permeability of coal seams to promote gas extraction, but the effects of acid solutions on coal combustion cannot be ignored. This paper focuses on HF, HCl, and HNO3. The Bagchi method determines the mechanism function of each nonisothermal TG stage of acidified coal. Combining FTIR, TG-DTA, and KTA, this paper studies the combustion performance of acidified coal from the perspectives of the coal molecular structure evolution, combustion phenomenon, and kinetics. The results show that inorganic acids can destroy C=O in coal, resulting in the carbonyl groups in the HF, HCl, and HNO3 samples decreasing to 21%, 35%, and 0% of that in the RAW samples, respectively. Inorganic acid significantly enhances the reaction rate and thermal effect of combustion stage and improves the comprehensive combustion performance of coal, and the effect is in the order of HF > HNO3>HCl. Inorganic acids change the most likely mechanism function of initial weight loss stage. The oxidation increase of the HNO3 sample is greater than the corrosion weight loss, resulting in a corrosion ratio of −1.74%. HF and HCl reduce the activation energy of oxidation weight gain stage and increase the spontaneous combustion tendency of coal samples.

Spontaneous combustion characteristics and mechanism of water-immersed and air-dried brown coal

ABSTRACT To reveal the influential laws and mechanism of water immersion on the spontaneous combustion traits of lignite in the low-temperature oxidation stage. Raw coal (HL), water-immersed for 30 days (HL-S30), 90 days (HL-S90) and 150 days (HL-S150), were taken as the research objects. The pore evolution characteristics and functional group migration law of coal were explored by Scanning Electron Microscopy (SEM), Low-temperature Nitrogen Adsorption Test (LNAT) and Fourier Transform Infrared Spectroscopy (FTIR). The low-temperature oxidation procedure was simulated by Programmed Heating Test (PHT), and the gas release characteristics, exothermicity and ultimate spontaneous combustion parameters of the relic coal were compared. These findings demonstrated that the discriminant indexes of spontaneous combustion tendency of four specimens change periodically with temperature, but generally the spontaneous combustion intensity of HL-S30 and HL-S150 is greater than HL, and HL-S90 is the least. The micro reasons for increasing oxidation activity of HL-S30 and HL-S150 are as follows: the number of micropores of water-immersed coal is almost 3 ~ 4 times that of HL, and the pores expanded with immersion which helps to enhance the adsorption of oxygen; the content of broken aromatic hydrocarbon -C = C- reached 50%, the total amount of hydroxy -OH decreased to 2/3 of HL, while the content of carboxyl -COOH and ether-oxygen bond -C-O- of active group doubled which are beneficial to accelerate the process of free radical chain reaction, and promote the gas release and the temperature of residual coal to reach the ignition point. The research findings enrich the basic theory of spontaneous combustion traits of water-impregnated coal, which help reduce the fire accidents and hidden dangers in actual production.

Experimental investigation of erosion effect on microstructure and oxidation characteristics of long-flame coal

To study the effect of erosion on coal microstructure and its oxidation characteristics, eroded coals were prepared by eroding coal samples in an acidic aqueous solution for 30 days, 90 days and 180 days, respectively. The microcrystalline structure, pore structure and active groups distribution of coal samples were studied using X-ray diffractometer, low-temperature N2 adsorption and infrared spectra. Temperature-programmed experiment was used to analyze the oxidation characteristics of raw coal and eroded coals. The results reflected that the number of aromatic layers and coalification degree of eroded coal are reduced compared with raw coal. The average pore diameter increases, which promotes oxygen transportation in coal pores. Under the erosion effects, the content of active groups such as hydroxyl (–OH), methylene (–CH2), and methyl (–CH3) in coal increases. Eroded coals, especially the coal eroded for 180-day demonstrate more oxygen consumption and CO production than raw coal during the oxidation process, and their apparent activation energies decrease. Besides, the enhancement mechanism of eroded coal's oxidation activity is expounded from the aspects of the increase of active sites and the improvement of pore structure. In brief, erosion effect increases the spontaneous combustion tendency of coal.

Mechanochemical effect of spontaneous combustion of sulfide ore

Spontaneous combustion of sulfide ore is a typical disaster in mining, which can cause a series of environmental and safety problems. In order to reveal the mechanical activation’s influence on the spontaneous combustion of sulfide ore during the mining process, the changes in the microstructure of sulfide minerals and their spontaneous combustion kinetics before and after activation were studied in this paper. The most probable mechanism function, apparent activation energy, and pre-exponential factor were derived using the Malek and Friedman methods, respectively. The results showed that mechanical activation leads to aggregation of mineral particles, defect generation in crystals, reduction in crystallize size, and increase in lattice distortion rate, which result in samples more actively. In the process of oxidation and spontaneous combustion, the main products were Fe2O3 and SO2 gas. And the mechanochemical effect will cause the reaction rate to become faster and lead the reaction to move toward low temperature. The mechanochemical effect will also lead to chemical reactions at low temperatures, causing some ore samples to be oxidized without changing the samples’ reaction mechanism functions. After mechanical force, the average apparent activation energy decreased by 26.27 kJ/mol, 32.73 kJ/mol, 27.01 kJ/mol, and 35.30 kJ/mol, respectively, and the sample’s spontaneous combustion tendency increased. In addition, ore samples’ active surface and grain boundary area increased under the mechanical forces, the lattice was distorted and dislocated, and a sub-stable amorphous phase was formed. In this process, the mechanical energy was partially converted into energy storage in the solid material, significantly increasing reactivity.

Study on the effect of coal microscopic pore structure to its spontaneous combustion tendency

Coal is a porous medium. Due to the large number of pores in coal and the pore size on its surface, usually ranging from millimeter to nanometer, it is difficult to measure and analyze the microscopic pore structure of coal. In order to investigate the effect of the microscopic pore structure of coal on its spontaneous combustion tendency, coal samples from different coal mines of the Kailuan Group were selected as the research objects, and the data of the microscopic pore distribution of three different coal samples were measured by using mercury injection apparatus. The regression analysis of microscopic pore data of coal samples obtained in the mercury injection experiment shows that the correlation coefficients of the regression curves are all greater than 0.94 and the fitting degree is good, indicating that there is a good correlation between the pressure, mercury intake and pore size of the coal samples, indicating that the fractal dimension of pore distribution is very effective. The fractal dimension is generally between 2 and 3, indicating that the microscopic pores of coal samples have good fractal characteristics and meet the fractal theory to describe the distribution characteristics of microscopic pores in porous media. Through the simulation system of natural combustion of coal, the simulation experiment of temperature rise oxidation of different coal samples (gas coal, fat coal, and coke coal) was carried out, and the curve of the concentration of gas products CO and CO2 in the process of temperature rise and oxidation of coal samples was drawn in the experiment. The experimental results show the relationship between the distribution structure of coal pores and its spontaneous combustion tendency, and the coal with a good distribution dimension has a stronger combustion tendency

Thermodynamics of Imidazolium-Based Ionic Liquids for Inhibiting the Spontaneous Combustion of Sulfide Ore

Spontaneous combustion of sulfide ore is one of the most common disasters in the process of ore mining, storage, and transportation, which can lead to a series of safety and environmental problems, thus affecting sustainable development in society. In this paper, four imidazolium-based ionic liquids: [BMIM][I], [BMIM][BF4], [EMIM][BF4], and [BMIM][NO3], were selected for inhibition experiments with sulfide ores to reveal the inhibition performance of ionic liquids against spontaneous combustion. The results show that the main products from the reaction were Fe2O3 and SO2, produced during the process of oxidation and spontaneous combustion and that the reaction moves towards a higher temperature under the action of ionic liquid, indicating that ionic liquids have a significant inhibition effect on the spontaneous combustion of sulfide ore. At the same temperature, the apparent activation energies of the samples treated with ionic liquids were all greater than those of the control samples, indicating that imidazolium-based ionic liquids can effectively reduce the spontaneous combustion tendency of sulfide ores. In addition, compared with other ionic liquids, [BMIM][NO3] had a more pronounced inhibition effect, with the activation energies of both ore samples maximally increased by 8.4% and 10.2% after [BMIM][NO3] treatment. This is due to the ability of [BMIM][NO3] to better isolate the samples from oxygen in the air and reduce the effective collisions between active molecules, thus inhibiting and retarding the spontaneous combustion of sulfide ores.

Reducing the tendency for chronometric counting in duration discrimination tasks

Chronometric counting is a prevalent issue in the study of human time perception as it reduces the construct validity of tasks and can conceal existing timing deficits. Several methods have been proposed to prevent counting strategies, but the factors promoting those strategies in specific tasks are largely uninvestigated. Here, we modified a classical two-interval duration discrimination task in two aspects that could affect the tendency to apply counting strategies. We removed the pause between the two intervals and changed the task instructions: Participants decided whether a short event occurred in the first or in the second half of a reference duration. In Experiment 1, both classical and modified task versions were performed under timing conditions, in which participants were asked not to count, and counting conditions, in which counting was explicitly instructed. The task modifications led to (i) a general decrease in judgment precision, (ii) a shift of the point of subjective equality, and (iii) a counting-related increase in reaction times, suggesting enhanced cognitive effort of counting during the modified task version. Precision in the two task versions was not differently affected by instructed counting. Experiment 2 demonstrates that—in the absence of any counting-related instructions—participants are less likely to engage in spontaneous counting in the modified task version. These results enhance our understanding of the two-interval duration discrimination task and demonstrate that the modifications tested here—although they do not significantly reduce the effectiveness of instructed counting—can diminish the spontaneous tendency to adopt counting strategies.

Effects of curcumin and γ-oryzanol solid dispersion on the brain of middle-aged rats.

Oxidative stress is one of the major factors that contributes to brain deterioration in the elderly. Oxidation causes molecular alterations, structural damage, and brain dysfunction, which includes cognitive impairment. Memory loss can begin in middle-aged individuals, so prevention of brain deterioration before aging is important. Several studies have reported that curcumin and γ-oryzanol exhibits anti-oxidant and anti-inflammatory properties. However, curcumin and γ-oryzanol exhibit low aqueous solubility. Thus, a solid dispersion technique was used to prepare curcumin and γ-oryzanol to enhance their solubility and stability. This study aims to evaluate the effects and mechanisms of γ-oryzanol solid dispersion (GOSD) and curcumin solid dispersion (CURSD) on learning and memory in six groups of male rats (n=5/group). Group one was the adult control consisting of 6-week old male rats, and the remaining five groups consisted of 42-week (middle-aged) male rats. The groups were labeled as the control group, the GO group (GOSD 10 mg/kg·BW), the Cur group (CURSD 50 mg/kg·BW), the GO-LCur group (GOSD 10 mg/kg·BW plus CURSD 25 mg/kg·BW), and the GO-HCur group (GOSD 10 mg/kg·BW plus CURSD 50 mg/kg·BW). Substances were administrated by oral gavage once daily for 42 consecutive days. The GO-HCur group exhibited significantly increased learning and memory performance in a Morris water maze and in reacting to a spontaneous tendency novel object test. The rats also exhibited decreased levels of lipid peroxidation, increased superoxide dismutase levels, glutathione peroxidase levels, catalase activity, and enhanced c-Fos expression both in the hippocampus and prefrontal cortex. The results indicated that GOSD 10 mg/kg plus CURSD 50 mg/kg was able to enhance learning and memory performance in the middle-aged rats.

Study of Butylated Hydroxytoluene Inhibiting the Coal Oxidation at Low Temperature: Combining Experiments and Quantum Chemical Calculations.

In order to cut off the chain reaction in the process of coal oxidation at low temperature (COLT), butylated hydroxytoluene (BHT) was used as an inhibitor to explore its inhibition effect and mechanism. In this paper, in situ Fourier transform infrared spectroscopy, electron paramagnetic resonance, and gas production of COLT experiments were conducted to compare the inhibited coal sample (BHT-Coal) with the raw coal. The results showed that BHT can effectively inhibit the formation of active free radicals, reduce the content of active alkoxy, carbonyl, and hydroxyl groups, increase the production temperature of CO, CO2, and C2H4, and reduce the concentration. The crossing point temperature increased from 132.3 to 157.4 °C, indicating that BHT can reduce the spontaneous combustion tendency of the raw coal. To explore the inhibition mechanism of BHT on COLT, five typical active free-radical models were established, and their active sites, active bonds, and thermodynamic parameters were calculated according to the density functional theory. The results showed that the highly active H atoms of the phenolic hydroxyl group in BHT can combine with active free radicals to generate stable compounds, and the activation energy of each reaction is small, which can occur under normal temperature and pressure. The inhibition mechanism of BHT is to reduce the concentration of the free radicals, so as to weaken the chain reaction strength during the COLT. This study provides a reference for the development and utilization of inhibitors.

Decision-Making and Life Satisfaction: The Role of General Decision-Making Styles and Maximizing Tendency as Predictors

However, research that focused on testing the role of decision-making on life satisfaction was still limited, even though almost every aspect of human life involves decision-making, and the results could determine one's life situation. There were prior studies that attempted to explore the relationships between life satisfaction and decision-making; however, the results were not conclusive. Therefore, the research aimed to test the relationship between decision-making styles and life satisfaction. Convenience sampling was used in data collection, and 154 university students participated in the research. It used a cross-sectional survey design to test the research hypothesis. The survey consisted of research information, informed consent, demographic, and measuring instrument for research variables. Decision-making styles are measured using General Decision-Making Styles and Maximizing Scale. Life satisfaction was measured using the Satisfaction with Life Scale. The result of multiple linear regression analysis shows that rational decision-making style and tendency to satisfice significantly predict higher levels of life satisfaction, while spontaneous decision-making style and tendency to maximize predict lower levels of life satisfaction. On the other hand, intuitive, dependent, and avoidant decision-making styles do not significantly predict life satisfaction. The implication and direction for future research are discussed.

Risk identification of coal spontaneous combustion based on COWA modified G1 combination weighting cloud model

To realize the scientific judgment of spontaneous combustion risk in the coal mine, the spontaneous combustion influence factors were analyzed from the three aspects of coal spontaneous combustion tendency, air leakage, and oxygen supply, heat storage and heat dissipation. And the basis for the evaluation of t spontaneous combustion grade was constructed. Combination ordered weighted averaging (COWA) calculation was introduced to optimizes G1 subjective weighting, and a COWA modified G1 combined weighting cloud model was proposed to identify the spontaneous combustion risk in the coal mine. Finally, the rationality of the model was verified with actual cases. The research results show that the spontaneous combustion risk level in the Lingquan coal mine is relatively safe, which is consistent with the actual situation. And the spontaneous combustion tendency of coal is the leading factor affecting spontaneous combustion risk.

Effect of Water Evaporation on the Inhibition of Spontaneous Coal Combustion.

Spontaneous coal combustion is the primary cause of coal mine fires. During the production process, spontaneous coal combustion in the goaf is often affected by air leakage, which weakens or annuls the effect of inhibitors and leads to secondary oxidation. However, the action mechanism of inhibitors on secondary oxidation spontaneous coal combustion remains unclear. Thus, this study analyzes the influence of moisture evaporation on the performance of a high-water-content physical inhibitor (HWPI) using the Carbolite temperature-programmed experiment, differential scanning calorimetry, scanning electron microscopy, and a MINI MR test. The results demonstrate that as the moisture content of the inhibitor decreased, after being treated with the HWPI and drying for 24 h, the concentrations of O2, CO, and CO2 were found to be lower than the gas concentration of raw coal, which showed that although the moisture content is reduced, the treated coal sample still has a lower spontaneous combustion tendency than the raw coal. The apparent activation energy was reduced, and the heat absorption per unit time decreased, which eventually weakened or annulled the effect of the HWPI. Future research should further improve existing inhibitor types to reduce the impact of secondary oxidation on spontaneous coal combustion caused by water evaporation.

Study on spontaneous combustion laws and fire prevention measures of coal remains during water drainage in water soaked goaf

ABSTRACT After the water release in the waterlogged mining area, the residual coal is prone to spontaneous combustion after being air-dried. To investigate the law of spontaneous combustion of residual coal in water immersed goaf during drainage, experimental studies, field observations and numerical simulations were used to analyze the effect of drainage on the spontaneous combustion characteristics of residual coal. Nitrogen injection parameters were optimized based on the results of the study. The experimental results show that: the spontaneous combustion tendency of soaked coal is enhanced compared with that of raw coal, and the spontaneous combustion tendency of soaked coal in goaf is stronger than that of the laboratory prepared soaked coal, because the immersion time of field-immersed coal is longer than that of laboratory-prepared coal samples. The simulation results of oxygen concentration and pressure distribution during goaf drainage show that: compared with that without drainage, the pressure in goaf decreased by 270 Pa, the air leakage in the goaf increased, the area of oxidation zone expanded by 5.2 times, and the possibility of spontaneous combustion of residual coal increased. Injecting nitrogen during the drainage was proposed to suppress the oxidation of the residual coal. The effect of nitrogen injection was measured on site and numerically simulated. After nitrogen injection were taken, the pressure dropped by 130 Pa after water release and the area of oxidation zone expanded by 1.5 times, indicating that nitrogen injection measures can effectively suppress the water-gas replacement. In addition, for this flooded goaf, the optimized nitrogen injection rate is 600 m3/h. This study provides an important reference for the prevention and control of spontaneous combustion hazards of residual coal in the short-distance composite coal seam during drainage of water immersed goaf.

Prediction of spontaneous combustion tendency of coal based on acetaldehyde release

ABSTRACT Acetaldehyde is one of the crucial gases with odor released during the early stage of spontaneous combustion of coal, and it is essential for predicting the spontaneous combustion tendency of coal. In this study, we systematically investigated the effects of coal metamorphic degree, coal temperature, coal particle size, and oxygen concentration on the release of acetaldehyde using three coal samples with different metamorphic degrees and a combination of oxidation and warming processes as well as gas and liquid chromatography. The results showed that with the increase in temperature, the amount of acetaldehyde released first increased and then stabilized or slightly decreased. The amount of acetaldehyde released at low temperatures was linearly related to oxygen consumption. The higher the degree of coal deterioration, the lower the amount of acetaldehyde released. As the particle size decreased, the amount of acetaldehyde released increased and then decreased. Finally, four warning levels were established based on the concentrations and trends of acetaldehyde together with other index gases.

Facile Fabrication of a Foamed Ag3CuS2 Film as an Efficient Self-Supporting Electrocatalyst for Ammonia Electrolysis Producing Hydrogen.

Ammonia (NH3) is one of the hydrogen carriers that has received extensive attention due to its high hydrogen content and carbon-free nature. The ammonia electro-oxidation reaction (AOR) and the liquid AOR (LAOR) are integral parts of an ammonia-based energy system. The exploration of low-cost and efficient electrocatalysts for the AOR and LAOR is very important but very difficult. In this work, a novel self-supporting AOR and LAOR bifunctional electrocatalyst of a Ag3CuS2 film is synthesized by a simple hydrothermal method. The Ag3CuS2 film without a substrate shows efficient catalytic activity and enhanced stability for NH3 electrolysis in both aqueous ammonia solution and liquid ammonia, including an onset potential of 0.7 V for the AOR and an onset potential of 0.4 V for the LAOR. The density functional theory calculations prove that compared to Cu atoms, Ag atoms with appropriate charge density on the surface of Ag3CuS2 are more electrocatalytically active for NH3 splitting, including the low energy barrier in the rate-determining *NH3 dehydrogenation step and the spontaneous tendency in the N2 desorption process. Overall, the foamed Ag3CuS2 film is one of prospective low-cost and stable electrocatalysts for the AOR and LAOR, and the self-supporting strategy without a substrate provides more perspectives to tailor more meaningful and powerful electrocatalysts.

Effects of intrinsic properties, particle size and specific surface area on WOP and spontaneous combustion susceptibility of coal

This study examines the effects of intrinsic properties, particle size, and specific surface area (SSA) of coal on spontaneous combustion. Moreover, it analyzes the underlying mechanism of spontaneous combustion from particle size, SSA and gas adsorption perspectives. The susceptibility of coal to spontaneous combustion is studied by wet-oxidation potential (WOP) method. Coal residues left after the WOP experiment are analyzed for change in structural and compositional behaviour. The study revealed an inverse relationship between the particle size and SSA of coal. Spontaneous combustion susceptibility increased with increase in volatile matter and decreased with increase in fixed carbon content of coal. The optimum moisture content of coal resulting maximum spontaneous combustion tendency is determined 6%. Decrease in particle size and increase in SSA augmented the spontaneous combustion propensity of coal. With decrease in coal particle size from 425 to 850 to < 38 µm, the mean D50 value decreased by 27 times, the mean SSA increased by 42 times and coal spontaneous combustion susceptibility increased almost by 2 times. Critical coal particle size is determined 38–74 µm (D50 = 50.56 µm), below which no appreciable change in oxidation rate is observed. Moreover, two models are developed to predict the spontaneous combustion susceptibility of coal based on particle size (D50) and SSA.

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.

Experimental study on the evolutionary characteristics of silicified coal functional groups during oxidation/pyrolysis

ABSTRACT In order to study the influence of silicification on coal components and the spontaneous combustion of silicified coal and its functional group change characteristics, the coal components of silicified coal and nonsilicified coal were analyzed by proximate analyzer; the oxygen absorption capacity of silicified coal and nonsilicified coal was tested by coal spontaneous combustion tendency tester, the oxygen absorption of coal at room temperature can directly reflect the degree of spontaneous combustion of coal and the generation of related gases in the reaction process of low temperature and oxygen of silicified coal and nonsilicified coal was measured by temperature programmed experimental device; In situ diffuse reflectance Fourier transform infrared spectrometer was used to test silicified coal and nonsilicified coal in nitrogen and air atmosphere. The evolution characteristics of different chemical bonds in the process of coal oxidation were studied. The surface active group changes of two different coal samples under different gas conditions were obtained, and the oxidative spontaneous combustion characteristics of silicified coal were microscopically proved. The results show that the oxygen absorption of silicified coal is higher than that of nonsilicified coal. During the reaction of silicified coal with oxygen, with the increase of coal temperature, the amount of oxidation gas and pyrolysis gas, oxygen consumption rate and exothermic intensity are higher than those of nonsilicified coal; the changes of related functional groups were mainly manifested in the hydroxyl groups at the peak positions of 3697–3625 cm−1 and 3624–3610 cm−1, the methyl and methylene groups at the peaks of 2975–2915 cm−1 and 2870–2845 cm−1, the aromatic ring C = C double bond at the position of 1604–1599 cm−1, the aromatics and the oxygen-containing functional groups at the spectral segment of 3060–3032 cm−1. Thus, the transformation rules of the related microstructure of silicified and nonsilicified coal under two gas atmospheres were obtained. This study has key significance for revealing the characteristics of silicified coal oxidation at lower temperature.