Reaction Mechanism Function Research Articles

Pyrolysis kinetic analysis and model constructions of different ranks of coal and validation by GA–BP neural networks

In the current steel industry, environmental pressures are mounting. If the reducing gases generated from coal pyrolysis can be utilized for reducing iron ore, the goal of low-carbon production with controllable costs can be achieved. However, the release of volatile content in coal has a significant impact on the pyrolysis process and final products. Therefore, in this study, the pyrolysis characteristics and gaseous products of four types of coal with different volatile matter content was investigated by thermogravimetry-mass spectrometry (TG-MS) technology. The results showed that coals with higher volatile matter content demonstrated stronger reactivity during pyrolysis. As the volatile matter content in coal increased, the starting temperature for releasing the reducing gases decreased, leading to a significant increase in the released gas volume. In addition, the three kinetic factors were calculated by isoconversional method, distribution of the activation energy model (DAEM) and Coats-Redfern (CR) method respectively, and the pyrolysis reaction mechanism function suitable for all coal types was reconstructed based on common solid reaction models. Finally, a predictive model based on a GA-improved back-propagation neural network (BPNN) was developed, which useing 21 input parameters to predict the TG curves, activation energy (E), lnA and mechanism function (fα) and achieving R2 values above 0.95. This study contributes to a comprehensive understanding of the pyrolysis mechanism of coals with different volatile matter content, providing scientific guidance for effective utilization.

Kinetic analysis of PA4 thermal degradation: Thermal stability with respect to crystallinity

Polyamide 4 (PA4) has garnered considerable attention due to its fully bio-based origin and biodegradability as a high-performance polyamide. Nevertheless, thermal degradation during the melting process impedes thermal processing, thereby constraining its potential for engineering plastics applications. To clarify the thermal degradation reactions of PA4 amidst intricate physical and chemical transformations, establishing a theoretical foundation for the thermal stability modification, we conducted a comprehensive analysis of PA4 thermal degradation coupled with crystallization, considering kinetics and reaction mechanisms. Calculation of reaction activation energies and mechanism functions revealed that PA4 pyrolysis is a two-stage compound process, with distinct degradation mechanisms attributed to the crystalline and amorphous regions. Additionally, the thermal degradation mechanism of the PA4-CaCl2 composite system at varying crystallinity levels was illustrated. The incorporation of Ca strengthens intermolecular forces in the samples, leading to an increased overall stability. Simultaneously, a notable alteration in the reaction mechanism was observed in the crystalline zone lacking the Ca phase.

Synergistic Effects and Kinetic Analysis in Co-Pyrolysis of Peanut Shells and Polypropylene.

The impact of COVID-19 has boosted growth in the takeaway and medical industries but has also generated a large amount of plastic waste. Peanut shells (PS) are produced in large quantities and are challenging to recycle in China. Co-pyrolysis of peanut shells (PS) and polypropylene (PP) is an effective method for processing plastic waste and energy mitigation. Thermogravimetric analysis was conducted on PS, PP, and their blends (PS-PP) at different heating rates (10, 20, 30 °C·min-1). The results illustrated that the co-pyrolysis process of PS-PP was divided into two distinct decomposition stages. The first stage (170-400 °C) was predominantly linked to PS decomposition. The second stage (400-520 °C) resulted from the combinations of PS and PP's thermal degradations, with the most contribution from PP degradation. With the increase in heating rate, thermogravimetric hysteresis appeared. Kinetic analysis indicated that the co-pyrolysis process reduced the individual pyrolysis activation energy, especially in the second stage, with a correlation coefficient (R2) generally maintained above 0.95. The multi-level reaction mechanism function model can effectively reveal the co-pyrolysis process mechanism. PS proved to be high-quality biomass for co-pyrolysis with PP, and all mixtures exhibited synergistic effects at a mixing ratio of 1:1 (PS1-PP1). This study accomplished effective waste utilization and optimized energy consumption. It holds significance in determining the interaction mechanism of mixed samples in the co-pyrolysis process.

Kinetic Analysis of the Reaction of Micrometer-Sized Al-Mg Alloy Particles in a Water Vapor Atmosphere.

This study investigated the reaction mechanism of aluminum-magnesium (Al-Mg) alloy particles with water (Al-Mg/H2O) through thermogravimetric analysis-differential scanning calorimetry experiments and kinetic analysis using isoconversional methods and the master plot technique to determine the reaction mechanism function, with the aim of providing insights to support metal powder/water ramjet engine design and combustion characteristics. The results showed that the Al-Mg/H2O reaction occurred in two distinct stages, with stage 1 primarily involving the reaction of Mg elements in the L(Al-Mg) alloy with water while Al played a leading role in stage 2. Notably, the reaction temperatures of Al-Mg particles were significantly lower than those for either Al or Mg particles alone in a water vapor environment. Additionally, the activation energy of stage 1 was lower than that for the individual Al and Mg particles and decreased with increasing Mg content in stage 2. Furthermore, the concentration of Mg in the alloy was found to have a major influence on the reaction mechanism, which followed a random nucleation and growth model. Overall, this work elucidated an alternating endothermic and exothermic staged reaction process for Al-Mg/H2O dominated first by Mg and then Al with kinetic insights providing theoretical support for optimizing Al-Mg alloy compositions for improved ignition and combustion performance in metal powder/water ramjet engines.

Non-isothermal kinetics and thermodynamics analysis of vanadium-titanium magnetite

Thermodynamic calculations and thermal analysis tests were performed to investigate the thermodynamic and kinetic behaviors of the carbothermal reduction of vanadium-titanium magnetite w(C)/w(O) and basicity on the carbothermal reduction process of vanadium-titanium magnetite based on the HIsmelt process. Thermodynamic analysis showed that the addition of basicity promoted the reduction of vanadium-titanium magnetite, and the reaction onset temperature gradually increased with the decrease of the valence states of the elements V, Ti and Fe in the product. Increasing the amount of carbon assigned to the system gradually increased the mass fractions of metal Fe and Fe3C and raised the mass fractions of Ti, V and their low valence compounds at equilibrium. Increasing the basicity had less effect on the Fe, V and Ti fractions of the equilibrium system. The results of kinetic tests showed that the maximum reduction degree and maximum reaction rate of the reduction reaction by increasing w(C)/w(O) and basicity increased, the apparent activation energy and the finger front factor decreased, and the reaction mechanism function of the non-isothermal kinetic reduction process was f(α) = (3/2)(1−α)4/3[(1−α)−1/3−1] −1 belonging to the three-dimensional Z-L-T diffusion model.

Effects of CaO addition on the reactivity and reaction kinetics of coke

ABSTRACTIn recent years, researches have shown that highly reactive coke for blast furnace ironmaking not only reduces fuel ratio but also reduces carbon emissions. Therefore, the research on developing high reactivity coke has received unprecedented attention. In this work, CaO was added into coals with different degrees of metamorphism to caking coke to study the effect of CaO amount on the non-isothermal gasification reaction behavior of coke. Results showed that the reactivity is significantly improved as the mass of added calcium oxide accounting for less than 0.4% of the dry coal mass. However, CaO exerted little effect on the micro-strength and structural strength of coke. The analysis of Mercury intrusion porosimetry of coke samples demonstrates that the addition of CaO increased the porosity of coke, resulting in the contact area with CO2, leading further to an increase in coke reactivity. At different heating rates, as the amount of CaO added increased, both the initial reaction temperature and the corresponding temperature of the maximum reaction rate of the gasification from CO2 decreased little by little. The addition of CaO was increased from 0% to 0.6%, the activation energy of the reaction was decreased by 16.41 kJ/mol. The kinetic model of the gasification of coke by CO2 conforms to the unreacted shrinking core model. The reaction mechanism function is converted from f(α) = 3(1-α)2/3 to f(α) = 2(1-α)1/2 (α means carbon conversion ratio), indicating that the addition of CaO accelerates the dissolution rate of coke by CO2.

Effects of Overload on Thermal Decomposition Kinetics of Cross-Linked Polyethylene Copper Wires.

During an overload fault in an energized wire, the hot metal core modifies the structure of the insulation material. Therefore, understanding the thermal decomposition kinetics of the insulation materials of the overloaded wire is essential for fire prevention and control. This study investigates the thermal decomposition process of new and overloaded cross-linked polyethylene (XLPE) copper wires using thermogravimetry-Fourier-transform infrared spectroscopy and cone calorimetry. The thermal decomposition onset temperature and activation energy of the overloaded XLPE insulation materials were reduced by approximately 15 K and 20 kJ mol-1, respectively, and its reaction mechanism function changed from D-ZLT3 to A2 (0 < α < 0.5). The FTIR shows that the major spectral components produced during the pyrolysis of the XLPE insulation material are C-H stretching, H2O, CO2, C-H scissor vibrations, and C=O and C=C stretching. Additionally, the four functional groups in the PE chains produced the spectral components in the following decreasing order of wavenumber: C-H stretching > CO2 > C-H scissor vibration > C=O and C=C stretching.

Exploration of Pyrolysis Behaviors of Waste Plastics (Polypropylene Plastic/Polyethylene Plastic/Polystyrene Plastic): Macro-Thermal Kinetics and Micro-Pyrolysis Mechanism

Pyrolysis is a promising technology used to recycle both the energy and chemicals in plastics. Three types of plastics, polyethylene plastic (PE), polypropylene plastic (PP) and polystyrene plastic (PS) were investigated using thermogravimetry–mass spectrometry (TG–MS) and reactive force field molecular dynamics (ReaxFF-MD) simulation. The thermogravimetric analysis showed that all three plastics lost weight during the pyrolysis in one step. The thermal decomposition stability is PS &lt; PP &lt; PE. The activation energies and reaction mechanism function of the three plastics were determined by the Kissinger and CR methods. Meanwhile, the ReaxFF-MD combined with density functional theory (DFT) was used to calculate the kinetics, as well as explore the pyrolysis mechanism. The calculated kinetic results agree well with the experimental methods. The common pyrolysis reaction process follows the dissociation sequence of the polymer to polymeric monomer and, then, to the gas molecules. Based on the bond length between the monomers and the bond dissociation energy for different plastics, the required energy for polymer dissociation is PS &lt; PP &lt; PE, which microscopically explains the macro-activation energy sequence and thermal stability. Moreover, due to the retention of aromatic rings in its monomers, PS almost completely converts into oil.

Kinetics and Combustion Behavior of Atomized Zn-Mg Alloy Powder.

Using pyrolants instead of warhead charges can release red light and thick smoke for target practice to highlight the safety of the impact point and dud disposal. In order to find the ideal material, the combustion and kinetic properties of two Zn-Mg alloys at critical proportions were investigated. Thermogravimetry/differential scanning calorimetry (TG/DSC) experiments in pure oxygen were conducted with atomized Zn-Mg alloy powder in the ratio of 7:3 and the ratio of 8:2 with three particle diameters under different heating rates. The kinetic parameters of the six materials were obtained by ASTM E698 and Ozawa-Flynn-Wall (OFW) methods, indicating that the activation energy (Eα) of the 7:3 Zn-Mg alloy powder was lower than that of the 8:2 Zn-Mg alloy powder when the particle size distributions are similar. By the method of nonlinear multivariate regression, the oxidation reaction of Zn-Mg alloy powder was divided into two steps. The proportion of mass gain of the first-step reaction of 7:3 Zn-Mg alloy powder was 0.462-0.518, and the proportion of mass gain of the first-step reaction of 8:2 Zn-Mg alloy powder was 0.138-0.228. Reaction mechanism functions of the two-step reaction of Zn-Mg alloy oxidation were derived as f(α) = (1 - α)n(1 + kcat·α). The results of combustion experiments showed that the pyrolants composed of 7:3 alloy can burn stably to produce satisfactory smoke and light signals, while the pyrolants composed of 8:2 alloy cannot achieve this. The 7:3 Zn-Mg alloy powder is an ideal ingredient for pyrotechnic compositions.

Analysis of the Thermal Behavior Characteristics and Dynamics of Coal Under High Primary Temperature Conditions in Deep Mines

ABSTRACT The exposure to spontaneous combustion of coal subjected to high ground temperatures increases as the depth of mine excavation increases. To research the oxidative heat release characteristics of deep coal, a study was carried out to characterize the oxidation kinetics and thermal effects on coal in deep thermal environments; deep coals (heat-treated coals) in 30°C (T30), 45°C (T45) and 60°C (T60) environments were prepared using a simultaneous thermal analysis, and the thermal weight characteristics (TG) and thermal release characteristics (DSC) of heat-treated coals were tested by simulating coal samples in different deep thermal environments; the thermal effects of heat-treated coals were analyzed by oxidation kinetic theory. The findings indicated that the characteristic point temperature of the coal gradually reduces (T60 has the lowest oxidation characteristic temperature) as the heat treatment temperature increases, and the maximum mass loss (63.76%) during thermal treatment coal oxidation occurs in the combustion stage. The oxidation reaction mechanism function for the low-temperature oxidation phases of the deep coal conforms to the Z-L-T equation with a three-dimensional diffusion reaction mechanism. As the temperature of the thermal environment is increased, the apparent activation energy of the coal decreases and the exothermic heat increases. This increases the tendency for oxidation of the deep coal, making it more amenable to spontaneous combustion as the ambient temperature at depth rises. The results contribute to a theoretical framework for monitoring and preventing coal spontaneous combustion fires in deep mine excavations.

Insight into nettle straw pyrolysis: Multicomponent kinetics, gas emissions and machine learning models

This study aimed to comprehensively investigate the pyrolysis process of nettle straw by analyzing its multicomponent kinetics modeling, kinetics and thermodynamic parameters, pyrolysis performance, reaction mechanisms, gas emissions, correlation and statistical analysis, as well as feasibility for industrial application. The average apparent activation energies for pseudo-hemicellulose (PS-HEC), cellulose (PS-CEL) and lignin (PS-LIG) were estimated as 147.41, 182.66, and 197.12 kJ/mol, respectively, using four model-free methods: Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Starink, and Tang. The pyrolysis reaction mechanisms were best described by diffusional and order-based models, with reaction mechanism functions of f(α) = [3/2(1-α)2/3]/[1-(1-α)1/3], f(α) = (1-α)1.5, and f(α) = (1-α)3 for PS-HEC, PS-CEL, and PS-LIG, respectively. TGA-FTIR analysis revealed that the gas emissions during nettle straw pyrolysis followed the order of CO > CO2 > C-O(H) > H2O > SO2 > CO > CH4 > NH3 > HCN. Best learning rate and artificial neural network (ANN) structure model were optimized. The optimal learning rate and ANN model structure were 0.0013 and ANN (5 *9 *1), respectively. NS has the potential to serve as a viable alternative to biofuel due to its certain energy, low price, abundant reserves, good pyrolysis performance, high volatile content, and low nitrogen and sulfur levels.

Co-pyrolysis of oil-based drill cuttings and pinewood sawdust: Thermal behavior, synergistic effect, artificial neural network and empirical reaction model

Evaluation of pyrolysis characteristics is essential to convert the waste into various high-value products. In this study, the co-pyrolysis of oil-based drill cuttings (OBDC) and pinewood sawdust (PS) was conducted to analyze the thermal behavior, synergistic effect, and reaction mechanism. Results showed that co-pyrolysis of OBDC and PS had a positive synergistic effect, and the more the percentage of PS in the blend, the stronger the synergistic effect. The pyrolysis characteristic index D increased from 6.50 × 10-05 to 47.38 × 10-05. The apparent activation energy during the co-pyrolysis of OBDC and PS (mass ratio in 1:1) was evaluated using two model-free methods (FWO and KAS) which were 101.38 kJ/mol and 97.51 kJ/mol, respectively. The pre-exponential factors analysis found that the solid phase surface reaction occurred in the co-pyrolysis at the conversion rate of 0.05–0.35; and the co-pyrolysis underwent a complex reaction at the conversion rate above 0.35. The artificial neural network (ANN) with Logsig-Tansig transfer function and neurons number 11 × 12 × 1 had the best prediction effect on co-pyrolysis. The reaction mechanism function (f(α)) of the co-pyrolysis of OBDC and PS was (1 − α)6.2778α2.3848[−ln(1 − α)]0.3570, indicating that co-pyrolysis was the combined effects of reaction order, accelerating, and nuclei growth and diffusion mechanism.

A Novel Eco-Friendly Circular Approach to Comprehensive Utilizing Bittern Waste and Oyster Shell

Efficient waste management, especially in relation to swaste reuse, has become a pressing societal issue. The waste bittern generated during salt production and discarded oyster shells present formidable environmental challenges and a waste of resources for some coastal regions. Therefore, this work developed a two-stage circular process for the environmentally friendly and efficient utilization of both waste materials. In the first stage, CO2 gas and an organic extraction phase comprising Tri(octyl-decyl)amine (R3N) and isoamyl alcohol were introduced into the waste bittern to obtain MgCO3·3H2O (s). The second stage involved reacting the reacted organic extraction phase with oyster shell powders to produce CaCl2·2H2O (s) and CO2 (g) and regenerate R3N. This work focused on investigating the yield of MgCO3·3H2O and the regeneration ratio of R3N, which are crucial indicators for the two stages involved in the process. The results indicate that, under optimal operating conditions, a maximum yield of 87% for MgCO3·3H2O was achieved, and the regeneration ratio of R3N reached 97%. Furthermore, the reaction mechanism and thermodynamic functions of the R3N regeneration process were elucidated as a crucial element in achieving a circular process. The findings of this work offer a sustainable solution to environmental pollution from waste bittern and oyster shells, and provide a promising avenue for green chemical production.

Pyrolysis and Oxidative Thermal Decomposition Investigations of Tennis Ball Rubber Wastes through Kinetic and Thermodynamic Evaluations

Thermal decomposition of tennis ball rubber (TBR) wastes in nitrogen and air has been studied through thermogravimetric analysis. The samples were thermally decomposed from room temperature to 950 K at heating rates of 3 to 20 K/min with a purging flow of 30 cm3/min. The degradation features and specific temperatures for two purging gases are thus compared according to the nonisothermal results. Kinetic analyses of two thermal decomposition processes have been isoconversionally performed using differential or integral methods. The activation energy as a function of mass conversion has been thus obtained over the entire decomposition range, varying from 116.7 to 723.3 kJ/mol for pyrolysis and 98.2 to 383.6 kJ/mol for oxidative thermal decomposition. The iterative Flynn-Wall-Ozawa method combined with the linear compensation effect relationship has been proposed for determining the pre-exponential factor and reaction mechanism function, resulting in chemical order reaction models of f(α) = (1 - α)5.7 and f(α) = (1 - α)5.8 for describing pyrolysis and the oxidative thermal degradation of TBR wastes, respectively. With these kinetic parameters, very satisfactory matching against experimental data has been obtained for both gases. Additionally, the thermodynamic parameters, such as the changes of entropy, enthalpy and Gibbs free energy, over the whole thermal degradation processes have also been evaluated.

Pyrolysis and co-pyrolysis of Egyptian olive pomace, sawdust, and their blends: Thermal decomposition, kinetics, synergistic effect, and thermodynamic analysis

The pyrolysis and co-pyrolysis kinetics of two Egyptian olive-pomace (Kroneiki and Shamlali), wood dust, and their blends were investigated by advanced isoconversional model-free methods (Vyazovkin and Senum-Yang) and model-fitting methods (Coats and Redfern integral method) using different integrated reaction mechanisms g(α) through TGA/DTG, and DTA techniques. Master Plot's method was applied to determine the best reaction mechanisms for the pyrolysis of the tested materials. The synergistic effect of co-pyrolysis on kinetics and the role of biomass were examined. The average values of activation energy estimated from VYA and SY kinetic methods, respectively, for KROP, SHOP, FSSD, Blend (1), and Blend (2) were 90.57 and 85.67 kJ/mol, 70.05 and 65.26 kJ/mol, 131.66 and 126.71 kJ/mol, 66.73 and 62.09 kJ/mol, and 113.12 and 108.21 kJ/mol. The co-pyrolysis of KROP, SHOP, and FSSD at a heating rate of 10 °C/min showed the best synergistic pyrolysis performance. The diffusional reaction mechanisms are the most likely reactions to describe the pyrolysis process of the first conversion stage (α = 0.1–0.5), while the reaction mechanism C8 and the reaction order model (F4) are the most likely reactions to describe the second stage (α = 0.5–0.9) pyrolysis process. The higher ΔH and ΔS values for the FSSD and Blend (2) signify that these materials consumed more energy during the pyrolysis process, while the lower ΔH and ΔS values for the KROP, SHOP, and Blend (1) showed the opposite. A blending ratio of 50% KROP, 25% SHOP, and 25% FSSD showed the best performance at a heating rate of 10 °C/min. The obtained kinetics parameters and the solution of the master plots method were validated by solving the Coats and Redfern integral method based on the reaction mechanism function g(α) that showed the best fit in the master plots method.

A combined kinetic analysis for thermal characteristics and reaction mechanism based on non-isothermal experiments: The case of poly(vinyl alcohol) pyrolysis

This work aims to implement one efficient combined kinetic approach for determining thermal kinetic triplets and elucidating reaction mechanism for poly(vinyl alcohol). Thermogravimetric pyrolysis profiles were acquired in inert nitrogen atmosphere with 5, 10, 15, and 20 K/min heating rates, and its thermal decomposition behavior was characterized in details. With respect to two main stages identified in whole pyrolysis process, their activation energies varying with conversion extents were computed by applying several model free methods, including FWO, KAS, FR, and advanced isoconversion approaches. Subsequently, the linear CR and non-linear masterplots model fitting methods were to severely figure out the appropriate reaction mechanism functions. Of particular interest is observed that F3/2 and F2 mechanism models were separately deemed to be appropriate for two stages, but they failed in giving good overlapping details with experimental data. Furthermore, a combined kinetic analysis was carefully conducted to obtain kinetics triplets, which includes model independent analysis and thoroughly considers kinetic compensation effect. Thereby, accurate reaction models were separately optimized and reconstructed for two distinct pyrolysis steps by the imported accommodation functions. This work finally provides a precise methodology to gain insight into thermal behavior and decomposition mechanism of poly(vinyl alcohol) , and improve the prediction accuracy of kinetics.

Thermodynamics and inhibition mechanism of imidazolium-based ionic liquids for inhibiting spontaneous combustion of iron sulfide

The process safety and sustainable development of the petrochemical industry have been seriously threatened by the spontaneous combustion of iron sulfide. In this paper, four kinds of ionic liquids were used to study the inhibition of spontaneous combustion of iron sulfides (FeS, FeS2). The thermodynamic characteristics, inhibition performance, and mechanism of ionic liquids on the spontaneous combustion of iron sulfide have been systematically studied. The results showed that the iron sulfide samples’ overall surface roughness and the proportion of fine particles in the samples increased after the ionic liquid treatment. In the process of oxidative spontaneous combustion, the extrapolation reaction onset temperatures of the samples treated with ionic liquids were enhanced, and the temperature at the samples’ maximum mass loss rate also was delayed. At the same time, the effect of ionic liquids in this process also changed the samples’ reaction mechanism functions, the apparent activation energies, and the mass loss rate. And in all of the experiments, the apparent activation energy of the samples treated with [BMIM][NO3] was enhanced the most by 16.74 kJ/mol, 14.8 kJ/mol, 26.49 kJ/mol, 14.23 kJ/mol, and 13.87 kJ/mol, respectively, while the mass loss rate of the samples treated with this ionic liquid also decreased the most. Therefore, [BMIM][NO3] had the best inhibiting effect among the four ionic liquids in this study. In addition, the results of molecular simulations showed that there is an adsorption process between the ionic liquid and the iron sulfide. In the adsorption process, the ionic liquid dominated the adsorption competition with oxygen molecules, which raises the iron sulfide’s activation energy of the oxidation reaction, thus inhibiting spontaneous combustion.

Insights into a co-precursor driven solid-state thermal reaction of ferrocene carboxaldehyde leading to hematite nanomaterial: a reaction kinetic study.

Thermal decomposition of a mixture of ferrocene carboxaldehyde and oxalic acid dihydrate in O2 atmosphere produced rod-like hematite nanomaterial. The decomposition reaction was complex as evident from the overlapped multistep reaction steps in the non-isothermal thermogravimetry (TG) profiles obtained in the 300-700 K range. A peak deconvolution method was applied to separate the overlapped reaction steps. The multistep TG profiles were successfully deconvoluted, which showed that the decomposition occurs in six individual steps. However, it was found that only the last three reaction steps were responsible for the production of hematite. To estimate the activation energy values for these thermal reactions, six model-free integral isoconversional methods were used. The activation energy value significantly depends on the extent of conversion in each step; however, the nature of its dependence significantly different for each step. The most probable stepwise reaction mechanism functions for the solid-state reactions were obtained using the master plot method. The reaction mechanism was found to be different for different steps. Utilizing the activation energy and reaction mechanism function, the reaction rates of decomposition for each step were determined. To substantiate the validity of the assumed kinetic models, the experimental conversion curves were compared with the constructed ones, and the agreement was quite reasonable. The conversion-dependent thermodynamic parameters were obtained utilising the estimated kinetic parameters. Role of the co-precursor in the thermal reaction of the precursor was plausibly revealed. The present study describes how the use of a co-precursor significantly enhances the thermal decomposition of the precursor, how hematite nanomaterials can be synthesized from a co-precursor driven solid state reaction at low temperatures, and how the kinetic calculations facilitate the understanding of the solid-state reaction process. This study proposes the use of a suitable combination of precursor and co-precursor for solid-state thermal synthesis of iron-based nanoparticles using organo-iron compounds as precursor and also illustrates the effective application of the thermal analysis technique to understand the decomposition reaction.

Thermogravimetric and spectroscopic analyses along with the kinetic modeling of the pyrolysis of phosphate tailings.

The present study aimed to understand the pyrolysis characteristics of phosphorus tailings and promote the resource utilization of phosphorus tailings. Thermogravimetry was combined with Fourier transform infrared spectroscopy-Raman spectroscopy-mass spectrometry (TG-FTIR-RS-MS) and kinetic models to investigate the possible reaction mechanisms during the pyrolysis of phosphorus tailings and the changes in the release characteristics of pyrolysis volatiles. The results showed that the pyrolysis process occurred in three different stages. First, small amounts of adsorbed water were removed, and organic matter in the tailings was decomposed. Second, CaMg(CO3)2 underwent thermal decomposition to produce CaCO3, MgO, and CO2. Third, CaCO3 further decomposed into CaO and CO2. Similarly, the pyrolysis kinetics were divided into three intervals based on the differences in their activation energy values. The pyrolysis reaction mechanism functions were two-dimensional diffusion (Valensi model), nucleation and growth (Avrami-Erofeev, n = 1/2), and nucleation and growth (Avrami-Erofeev, n = 1/4). The gases released during the pyrolysis of phosphate tailings were mainly CO2, F2, and HF.

Inhibition effect of imidazolium-based ionic liquids on pyrophorisity of FeS

To explore the inhibition of imidazolium-based ionic liquids on the pyrophorisity of sulfur corrosion products in oil tanks, FeS, the main component of sulfur corrosion products, was used as experimental samples in this paper. Four ionic liquids, [BMIM][I], [BMIM][BF4], [EMIM][BF4] and [BMIM][NO3], were selected to process the samples. The microstructure of the samples was characterized by a scanning electron microscope. The processes of spontaneous combustion and the changes of specific heat capacity of the sample were analyzed by TG-DSC. On this basis, the apparent activation energy, pre-exponential factor, and reaction mechanism function of the samples in the process of spontaneous combustion were obtained by the Kissinger method and the Malek method. The results show that the reaction process of the samples can be divided into four stages, and the third stage is the spontaneous combustion stage, in which the samples have a violent oxidation reaction and release a lot of heat. The ionic liquids have different degrees of inhibition effect on the pyrophorisity of FeS, among which [BMIM][I] have the most obvious inhibition effect, and the exothermic peak of the treated samples 25.7% lower than that of the untreated samples. The average activation energy of the samples treated with the four ionic liquids respectively increased by 65.28, 25.62, 35.27, and 33.88 kJ/mol, and the activation energy of the samples treated with ionic liquid [BMIM][I] showed the greatest overall improvement and the best inhibition effect.