Search Results (206)

The use of hydrogen for smelting reduction ironmaking can effectively reduce the consumption of coke, as well as the CO₂ emission. However, the dynamic mechanism of this process is not clear. In this paper, isothermal thermogravimetric analysis (TGA) was used to study the reduction process of wustite by hydrogen at 1673–1773 K. Results show that wustite can be entirely reduced, and with the increase in temperature, the reduction reaction becomes more intense, and the time required for the entire reduction decreases. The hydrogen reduction of wustite at 1673–1773 K fits the Mampel power model: f(α) = 2α^1/2. When the reactants are molten and the products are solid, the apparent activation energy of the reduction process calculated by the iso-conversional method is 9.15 kJ·mol⁻¹. Molecular dynamics simulation results show that the adsorption of hydrogen molecule on FeO surface is spontaneous. With the increase in temperature, FeO substrate becomes more active, and hydrogen molecules move more violently. The average distance between a certain hydrogen atom and its neighboring atom was analyzed statistically. The increase in temperature will increase the average bond length of hydrogen molecules, reduce their bond energy, and facilitate the adsorption of hydrogen molecules on the FeO surface. Full article

Given the depletion of conventional oil and gas resources, oil shale represents a promising alternative source of hydrocarbons that can be recovered through pyrolysis. This study examines the thermal decomposition of raw oil shale from the Tarfaya deposit and its decarbonized concentrate, studied by thermogravimetric analysis at different heating rates (5, 10, 20 and 40 °C/min). Pretreatment with acetic acid enabled the selective removal of calcite, confirmed by elemental, XRF, and XRD analyses, which revealed a relative enrichment in silica and dolomite in the oil shale concentrate. Pyrolysis of the raw shale occurs primarily between 300 and 500 °C, with a conversion rate of approximately 30%. In contrast, for the oil shale concentrate, the pyrolysis process begins at a relatively low temperature, within a wider temperature range (260–520 °C). Kinetic analysis based on Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods shows that at a conversion rate of 60%, the activation energy achieves 14.09 kJ/mol and 10.78 kJ/mol, respectively. The results indicate that the selective removal of calcite by acetic acid treatment facilitates kerogen pyrolysis by reducing mineral–organic interactions. Indeed, calcite dilutes the reactive organic fraction and can act as a physical barrier limiting heat and mass transfer within the oil shale. Its removal improves, on the one hand, the accessibility of kerogen to thermal cracking and promotes its decomposition, and on the other hand, reduces the amount of residue after pyrolysis. In addition, the kinetic analysis based on Criado master curves reveals changes in the reaction mechanism after decarbonation treatment depending on the heating rate (β). A shift from a two-dimensional Avrami–Erofeev model (A2) to a three-dimensional model (A3) was observed at a low heating rate (β = 5 °C/min), suggesting a change in nucleation and growth dynamics during kerogen decomposition. At high heating rates (10, 20 and 40 °C/min), the thermal decomposition of kerogen combines several reaction mechanisms depending on the temperature range considered. Full article

The present research article deals with the thermal degradation study of epoxy resins filled with hybrid nanostructured forms of carbon under oxidative conditions. In particular, the formulated polymer composites (denoted as HYB_0.1%_CNTs:GNs and HYB_0.5%_CNTs:GNs, respectively) consist of two kinds of fillers, namely multi-walled carbon nanotubes (CNTs) and graphene nanosheets (GNs), mixed together with two different total mass amounts: 0.1 and 0.5%. In both kinds of nanocomposites, three different CNT:GN mixing ratios were considered (5:1, 1:1, and 1:5, respectively), thus providing a total of six hybrid samples. The thermal behavior of these samples was studied by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) under flowing air, and two processes took place in distinct temperature ranges. In each step, about 50% of mass loss is detected with an exothermic effect in the corresponding DTA curve, with the second one accompanied by an intense heat release. The kinetic analysis of the two-stage oxidative thermal degradation was investigated using a model-free isoconversional approach. A non-Arrhenian behavior of the temperature function k(T) was assumed, and lifetime prediction was estimated at temperatures close to those of the possible applications. Isoconversional analysis shows nearly constant activation energies for all composites except HYB_0.1%_5:1 (from 142 to 96 kJ·mol⁻¹), while lifetime predictions indicate that thermal stability increases with graphene content at 0.1% loading (HYB_0.1%_1:5) and with CNT content at 0.5% loading (HYB_0.5%_5:1), with uncertainties below 7%. Finally, because of the π–π bond interactions between the CNTs and the GNs dispersed in the epoxy resin matrix, an effective and remarkable electrical performance was found and a correlation with both electrical and morphological properties was established. In this regard, Tunneling Atomic Force Microscopy (TUNA) proved to be particularly powerful in allowing the simultaneous mapping of topography and localized conductive networks with exceptional sensitivity to nanofiller dispersion, such as CNTs and GNs. DC conductivity increased by up to nine orders of magnitude at 0.1 wt% hybrid loading (up to 3.73 × 10⁻⁴ S/m vs. 1.06 × 10⁻¹³ S/m for CNT-only), with nanoscale TUNA currents (−1.9 to 4.5 pA) mirroring macroscopic trends, while at 0.5 wt% all hybrids reached 10⁻² S/m, indicating reduced synergy once a fully developed conductive network is established. Full article

In this study, chemiluminescence (CL) is presented as a highly sensitive, mechanistically coupled method for investigating the thermo-oxidative aging of dammar resin, a triterpenoid natural resin of central relevance to conservation science. In contrast to conventional spectroscopic techniques, CL does not primarily reflect the accumulated oxidation state; instead, it selectively detects the formation and decomposition of reactive peroxide and hydroperoxide intermediates, thereby providing an early view of the oxidative reactivity of the material. Measurements performed under inert and oxidative atmospheres provide a clear distinction between pre-existing oxidative damage and ongoing autoxidation. Correlation with Fourier-transform infrared (FTIR) spectroscopy demonstrates that oxidized functional groups are not necessarily associated with high oxidative reactivity, underscoring the functional advantage of chemiluminescence for stability assessment. The combination of dynamic CL measurements with model-free isoconversional kinetics has been shown to reveal the pronounced dependence of effective activation energy on the extent of the reaction. This α-dependence confirms the multistep nature of dammar oxidation and highlights the limitations of classical Arrhenius models. Furthermore, chemiluminescence is an effective screening tool for evaluating stabilizers and synergistic additive combinations, providing a robust basis for kinetic modeling and evidence-based decision-making in conservation science. Full article

Gypsum-based fire protection relies on thermally activated dehydration, where chemically bound water is released and evaporated, thereby providing an endothermic heat sink that delays heat penetration through assemblies. In parallel, inorganic hydrated salts are increasingly used as flame-retardant additives in gypsum-based systems to enhance heat absorption over specific temperature ranges. Fire simulation tools and performance-based fire engineering approaches require reliable kinetic data and reaction enthalpies that can be implemented as coupled thermal–chemical source terms. However, additive-specific kinetic datasets remain limited, particularly under restricted vapor exchange conditions representative of porous construction materials. This work investigates the thermal decomposition behavior and dehydration kinetics of Aluminum Trihydrate (Al(OH)₃, ATH), Magnesium Hydroxide (Mg(OH)₂, MDH), Calcium Aluminate Sulfate (3CaO·Al₂O₃·3CaSO₄·32H₂O, CAS), and Magnesium Sulfate Heptahydrate (MgSO₄·7H₂O, ESM) with emphasis on vapor-restricted conditions representative of confined porous systems. Differential scanning calorimetry (DSC) experiments were conducted at three heating rates (2, 10, and 20 K/min for MDH, CAS and ESM and 20, 40 and 60 K/min for GB-ATH) up to 600 °C using pinhole crucibles to simulate autogenous vapor pressure. The thermal analysis indicates that ATH and MDH exhibit predominantly single-step dehydration behavior, while ESM shows a complex multi-step mechanism. Although CAS presents a single dominant thermal peak in the DSC signal, the isoconversional analysis reveals a multi-stage reaction behavior, demonstrating that peak-based interpretation alone may be insufficient for such systems. Kinetic parameters were determined using both model-free (Starink) and model-fitting approaches in accordance with the recommendations of the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). All reactions were consistently described using the Avrami–Erofeev model as an effective phenomenological representation of the conversion behavior. The extracted kinetic triplets were validated through numerical simulations, showing good agreement with experimental conversion and reaction rate data. The resulting kinetic parameters and dehydration enthalpies provide a physically consistent dataset for the description of dehydration processes under restricted vapor exchange. These results support the development of thermochemical models for gypsum-based systems; however, their transferability to full-scale assemblies remains subject to validation under coupled heat- and mass-transfer conditions. Full article

The subject concerns the determination of activation energy under dynamic conditions using two theoretical isothermal models, and subsequently experimental data, with reference to the α–T relationship matrix. In recent years, the Vyazovkin method, classified as one of the isoconversional variants, has gained the greatest recognition. Comparison was made between two isothermal models of the thermal dissociation of calcite, which in chronological terms are associated with a kinetic–nucleation reaction/process (the H-CL, as a kinetic model) and a kinetic–desorption reaction/process (the V, as a thermodynamic model). A comparison of numerical values, understood as the logarithm of the reaction/process rate with respect to temperature, shows correspondence in the temperature range up to the equilibrium temperature. The H-CL model is characterized by a strong dominance of the nucleation process relative to the chemical reaction, whereas the V model exhibits a certain type of balance resulting from the course of the chemical decomposition reaction combined with the transformation of a metastable oxide into a crystalline form. It was confirmed that both models describe the same phenomenon within the transformation process, which implies that for a constant conversion degree, the proportions of the chemical reaction and the physical process vary. Pointwise with increasing temperature, the H-CL model leads to a minimum activation energy E → 0, whereas the V model reaches a negative activation energy E < 0. In both cases, the apparent activation energy summed over the process is constant, and the assigned conversion degree, treated as isoconversional, remains fixed and corresponds to the assumed activation energy of the completed reaction/process. Several simple methods for its determination under dynamic/isoconversion conditions are used. Full article

This work contributes to advancing sustainable energy and waste management strategies by investigating the thermochemical conversion of food-based biomass through pyrolysis, highlighting the role of artificial intelligence (AI) in enhancing process modelling accuracy and optimization efficiency. The main objective is to explore the potential of underutilized biomass resources like spent coffee grounds (SCGs) and DSs (date seeds) for sustainable hydrogen production. Specifically, it aims to optimize the pyrolysis process while evaluating the performance of these resources both individually and as blends. Proximate, ultimate, fibre, TGA/DTG, kinetic, thermodynamic, and Py-Micro-GC analyses were conducted for pure DS, SCG, and blends (75% DS-25% SCG, 50%DS-50%SCG, 25%DS–75%SCG). Blend 3 offered superior hydrogen yield potential but had the highest activation energy (Ea: 313.24 kJ/mol), while Blend 1 exhibited the best activation energy value (Ea: 161.75 kJ/mol). The kinetic modelling based on isoconversional methods (KAS, FWO, and Friedman) identified KAS as the most accurate. These approaches work together to provide a detailed understanding of the pyrolysis process with a particular emphasis on the integration of artificial intelligence (AI). An LSTM model trained with lignocellulosic data predicted TGA curves with exceptional accuracy (R²: 0.9996–0.9998). Full article

This study presents a comparative thermal and kinetic analysis of three benzimidazole derivatives used in the pharmaceutical field: fenbendazole, mebendazole, and flubendazole. The investigations were carried out using thermoanalytical methods, including thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), in order to evaluate thermal stability, decomposition stages, and to calculate kinetic parameters. The obtained data were processed using isoconversional methods (Ozawa–Flynn–Wall, and Friedman) and non-parametric method (NPK) to determine activation energies and degradation mechanisms. The results revealed significant differences among the three compounds regarding their thermal stability and decomposition behavior, influenced by molecular structure and aromatic substituents. Furthermore, the comparative analysis provides valuable insights for optimizing technological processes, assessing stability in pharmaceutical formulations, and expanding research on the therapeutic potential of these compounds, including in oncological studies. Overall, the study contributes to a deeper understanding of the relationship between chemical structure and thermal stability in benzimidazole derivatives. Full article

In this study, thermogravimetric analysis was employed to investigate the non-isothermal combustion behavior and kinetic characteristics of poplar biomass under air and oxy-fuel (O₂/CO₂) atmospheres. The effects of heating rate and oxygen concentration on combustion performance, gaseous emissions, and kinetic parameters were systematically analyzed. Results show that poplar biomass combustion consists of four distinct stages: moisture evaporation, devolatilization with volatile oxidation, char and fixed carbon oxidation, and final burnout. Increasing the heating rate intensifies the combustion process, shifting characteristic temperatures to higher values and significantly enhancing the comprehensive combustion index. Compared with air combustion, oxy-fuel conditions reduce ignition temperature and the temperature corresponding to the maximum combustion rate, leading to an earlier ignition and a more concentrated reaction interval. Higher oxygen concentrations further improve overall combustion performance and promote more complete carbon conversion. Gas emission analysis indicates that oxy-fuel combustion effectively suppresses NO₂ and SO₂ formation, demonstrating notable emission-reduction potential. Kinetic analysis using the Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa isoconversional methods shows that the activation energy varies with conversion degree and is generally higher under oxy-fuel atmospheres than in air. Overall, oxy-fuel combustion enhances biomass reactivity while achieving coordinated emission control through increased oxygen partial pressure and improved heat and mass transfer, supporting its practical application in biomass energy systems. Full article

Oxidation of oils is a free-radical cascade of reactions leading to the formation of undesirable odors and tastes, nutrient degradation, and potentially harmful compounds. To better understand the oxidation process, the kinetic parameters were examined depending on the degree of conversion (0 ≤ α ≤ 1) in this study. This approach provides insight into the complexity of the oxidative mechanism and allows a more reliable evaluation of the oxidative stability of nettle seed oil and its behavior during thermal treatment. A non-isothermal DSC method was applied, and kinetic parameters including the activation energy (Ea), the pre-exponential factor (A), and the reaction rate constant (k) were evaluated by applying the isoconversional Ozawa–Flynn–Wall method. Based on kinetic parameters, a simulation of oil oxidation at constant temperature (22 °C) was performed and the oil induction time was estimated. This value was compared to the ones obtained by OXITEST method. The observed conversion-dependent kinetic parameters demonstrate the complex oxidation behavior of nettle seed oil and justify the application of conversion-sensitive kinetic models to accurately describe its thermal stability. The induction period obtained under accelerated oxidation conditions suggests satisfactory oxidative stability of oil and highlights its potential suitability for nutritional and functional applications. Full article

The influence of phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH) impregnation on the pyrolysis and CO₂ gasification behavior of dairy manure was evaluated using thermogravimetric analysis (TGA), with kinetic parameters assessed through iso-conversional kinetic analysis (Frieman method). H₃PO₄ pretreatment altered early decomposition by partially removing hemicellulose and promoting the formation of thermally stable, condensed char structures. The resulting chars exhibited reduced CO₂ reactivity, as evidenced by higher gasification temperatures, lower syngas yields, and elevated activation energies, indicating hindered CO₂ diffusion and slower Boudouard reaction kinetics. In contrast, NaOH pretreatment caused only minor changes in both pyrolysis and gasification behavior. A slight reduction in pyrolysis activation energy suggested Na⁺ catalyzed bond-cleavage reactions; however, this effect did not enhance CO₂ gasification reactivity. Chars produced from NaOH-treated manure exhibited slightly higher activation energies during CO₂ gasification and syngas yields, which remained close to or slightly above those of raw manure, attributed to complex mineral interactions that diminish the catalytic influence of sodium. Overall, these findings clarify how acid and base chemical pretreatments govern char evolution and carbon-CO₂ reactivity, providing a foundation for optimizing pretreatment strategies and reactor conditions for manure conversion in CO₂-based pyrolysis and gasification systems. Full article

Rice husk biomass was investigated under O₂/CO₂ oxy-fuel conditions using Thermogravimetric analysis (TG)-derivative thermogravimetry (DTG)-mass spectrometry (MS) experiments, iso-conversional kinetic analysis, and ReaxFF reactive molecular dynamics simulations. Oxy-fuel combustion significantly enhanced combustion performance compared with air combustion. At 10 °C·min⁻¹, the ignition and burnout temperatures decreased to 235 °C and 435 °C under 70%O₂/30%CO₂, while the maximum mass loss rate increased more than fivefold and the comprehensive combustion index increased markedly. Online MS analysis showed concentrated CO₂ formation and O₂ consumption within 280–330 °C, accompanied by markedly suppressed NO_x and SO₂ emissions. Kinetic analysis revealed high apparent activation energies (525–548 kJ·mol⁻¹) at α ≈ 0.5; these values are conversion-dependent and sensitive to the iso-conversional method employed and therefore reflect relative kinetic trends rather than intrinsic Arrhenius parameters, indicating a transition from chemical control to diffusion–structure-coupled control. Molecular dynamics simulations further confirmed that moderate oxygen enrichment promotes organic backbone cleavage, whereas excessive oxygen leads to a carbon-limited regime. These results provide mechanistic insights into biomass oxy-fuel combustion and its optimization for CO₂ capture applications. Full article

Refuse-derived fuel (RDF) presents a viable strategy to concurrently address the challenges of municipal solid waste management and the need for alternative energy. In this context, the present review systematically synthesizes recent advances in RDF preparation, combustion behavior, and efficient utilization technologies. The study examines the full chain of RDF production—including waste selection, mechanical/optical/magnetic sorting, granulation, briquetting, and chemical modification—highlighting how pretreatment technologies influence fuel homogeneity, calorific value, and emissions. The thermochemical conversion characteristics of RDF are systematically analyzed, covering the mechanism differences among slow pyrolysis, fast pyrolysis, flash pyrolysis, pyrolysis mechanisms, catalytic pyrolysis, fragmentation behavior, volatile release patterns, and kinetic modeling using Arrhenius and model-free isoconversional methods (e.g., FWO). Special attention is given to co-firing and high-efficiency combustion technologies, including ultra-supercritical boilers, circulating fluidized beds, and rotary kilns, where fuel quality, ash fusion behavior, slagging, bed agglomeration, and particulate emissions determine operational compatibility. Integrating recent findings, this review identifies the key technical bottlenecks—feedstock variability, chlorine/sulfur release, heavy-metal contaminants, ash-related issues, and the need for standardized RDF quality control. Emerging solutions such as AI-assisted sorting, catalytic upgrading, optimized co-firing strategies, and advanced thermal conversion systems (oxy-fuel, chemical looping, supercritical steam cycles) are discussed within the broader context of carbon reduction and circular economy transitions. Overall, RDF represents a scalable, flexible, and high-value waste-to-energy pathway, and the review provides insights into future research directions, system optimization, and policy frameworks required to support its industrial deployment. Full article

The expansion of unconventional hydrocarbon extraction in the Vaca Muerta Formation (Argentina) has increased the generation of oil-based drill cuttings (OBDCs), a hazardous waste containing up to 20 wt% total petroleum hydrocarbons (TPHs) and trace metals. These characteristics pose risks to soil and groundwater, highlighting the need for sustainable treatment technologies that minimize environmental impacts and enable resource recovery. This study evaluates slow pyrolysis as a thermochemical route for OBDC stabilization and valorization. Representative samples were characterized through proximate, ultimate, and metal analyses, confirming a complex hydrocarbon–mineral matrix with 78.1 wt% ash, 15.9 wt% volatile matter, and 12.5 wt% TPH. Thermogravimetric analysis (10–20 °C min⁻¹), combined with isoconversional methods, identified three pseudo-components with activation energies ranging from 41.9 to 104.5 kJ mol⁻¹. Slow pyrolysis experiments in a fixed bed (400–650 °C) reduced residual TPH to below 1 wt% at temperatures ≥ 400 °C, meeting Argentine criteria for non-hazardous solids. The process also produced a condensed liquid organic fraction, supporting its potential within circular-economy strategies. Overall, the results show that slow pyrolysis is a viable and sustainable technology for reducing environmental risks from OBDC while enabling resource and energy recovery, contributing to a broader understanding of their thermochemical treatment. Full article

This study examined the thermal degradation of pulverized Musa sapientum (banana) peel waste through thermogravimetric measurements and thermokinetic modelling. For the first time, it also incorporated backpropagation deep learning to model pyrolysis traces, enabling the prediction and optimization of the process. Physicochemical characterization confirmed the material’s lignocellulosic composition. TGA was performed between 30 and 950 °C at heating rates of 5, 10, 20, and 40 °C min⁻¹, identifying a primary devolatilization range of 190 to 660 °C. The application of a backpropagation machine learning technique to the processed TGA data enabled the estimation of arbitrary constants that accurately captured the characteristic behaviour of the experimental data ($R^2~0.99$). This modelling and simulation approach achieved a significant reduction in training loss—decreasing from 35.9 to 0.07—over 47,688 epochs and 1.4 computational hours. Sensitivity analysis identified degradation temperature as the primary parameter influencing the thermochemical conversion of BP biomass. Furthermore, analyzing deconvoluted DTG traces via Criado master plots revealed that the 3D diffusion model (Jander [D3]) is the most suitable reaction model for the hemicellulose, cellulose, and lignin components, followed by the R2 and R3 geometrical contraction models. The estimated overall activation energy values obtained through the Starink (STK) and Friedman (FR) model-free isoconversional kinetic methods were 82.8 ± 3.3 kJ.mol⁻¹ and 97.6 ± 3.9 kJ.mol⁻¹, respectively. The thermodynamic parameters estimated for the pyrolysis of BP indicate that the formation of activated complexes is endothermic, endergonic, and characterized by reduced disorder, thereby establishing BP as a potential candidate material for bioenergy generation. Full article