Articoli di riviste: "Thermochemical and kinetic studies"

1

Krishnan, K., G. A. Rama Rao, K. D. Singh Mudher e V. Venugopal. "Thermochemical and kinetic studies on CeTe2O6". Journal of Alloys and Compounds 244, n. 1-2 (novembre 1996): 79–84. http://dx.doi.org/10.1016/s0925-8388(96)02435-8.

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Krishnan, K., G. A. Rama Rao, K. D. Singh Mudher e V. Venugopal. "Thermochemical and kinetic studies on ThTe2O6". Journal of Nuclear Materials 230, n. 1 (maggio 1996): 61–66. http://dx.doi.org/10.1016/0022-3115(96)80011-0.

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Lucarini, Marco, Gian Franco Pedulli, Luca Valgimigli, Riccardo Amorati e Francesco Minisci. "Thermochemical and Kinetic Studies of a Bisphenol Antioxidant". Journal of Organic Chemistry 66, n. 16 (agosto 2001): 5456–62. http://dx.doi.org/10.1021/jo015653s.

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Amorati, Riccardo, Marco Lucarini, Veronica Mugnaini, Gian Franco Pedulli, Franceso Minisci, Francesco Recupero, Francesca Fontana, Paola Astolfi e Lucedio Greci. "Hydroxylamines as Oxidation Catalysts: Thermochemical and Kinetic Studies". Journal of Organic Chemistry 68, n. 5 (marzo 2003): 1747–54. http://dx.doi.org/10.1021/jo026660z.

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Golovanova, O. F., G. V. Sitonina, V. I. Pepekin, B. L. Korsunskii e F. I. Dubovitskii. "Kinetic and thermochemical studies of N-nitro and N-nitrosomorpholine". Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 37, n. 5 (maggio 1988): 881–86. http://dx.doi.org/10.1007/bf00957051.

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Fedunik-Hofman, Larissa, Alicia Bayon e Scott W. Donne. "Kinetics of Solid-Gas Reactions and Their Application to Carbonate Looping Systems". Energies 12, n. 15 (2 agosto 2019): 2981. http://dx.doi.org/10.3390/en12152981.

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Reaction kinetics is an important field of study in chemical engineering to translate laboratory-scale studies to large-scale reactor conditions. The procedures used to determine kinetic parameters (activation energy, pre-exponential factor and the reaction model) include model-fitting, model-free and generalized methods, which have been extensively used in published literature to model solid-gas reactions. A comprehensive review of kinetic analysis methods will be presented using the example of carbonate looping, an important process applied to thermochemical energy storage and carbon capture technologies. The kinetic parameters obtained by different methods for both the calcination and carbonation reactions are compared. The experimental conditions, material properties and the kinetic method are found to strongly influence the kinetic parameters and recommendations are provided for the analysis of both reactions. Of the methods, isoconversional techniques are encouraged to arrive at non-mechanistic parameters for calcination, while for carbonation, material characterization is recommended before choosing a specific kinetic analysis method.

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Gokon, Nobuyuki, Kosuke Hayashi, Hiroki Sawaguri e Fumiya Ohashi. "Long-Term Thermal Cycling Test and Heat-Charging Kinetics of Fe-Substituted Mn2O3 for Next-Generation Concentrated Solar Power Using Thermochemical Energy Storage at High Temperatures". Energies 15, n. 13 (30 giugno 2022): 4812. http://dx.doi.org/10.3390/en15134812.

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We studied the performance in terms of the long-term cyclic thermal storage and heat-charging kinetics of Fe-substituted manganese oxide for use in thermochemical energy storage at temperatures exceeding 550 °C in a next-generation concentrated solar power system in which a gas stream containing oxygen is used for reversible thermochemical processes. The Fe-substituted Mn2O3 was evaluated from the viewpoint of its microstructural characteristics, thermodynamic phase transitions, and long-term cycling stability. A kinetic analysis of the heat-charging mode was performed at different heating rates to formulate the kinetic equation and describe the reaction mechanism by determining the appropriate reaction model. Finally, the kinetics data for the sample obtained after the long-term cycling test were compared and evaluated with those of the as-prepared sample and kinetic literature data tested under different conditions. For the long-term cycled sample, the Avrami–Erofeev reaction model (An) with n = 2 describes the behavior of the first part of the charging mode, whereas the contracting area (R2) reaction model best fits the last half of the charging mode. For the as-prepared sample, except for the early stage of the charging mode (fractional conversion < 0.2), the contracting volume (R3) reaction model fits the charging mode over a fractional conversion range of 0.2–1.0 and the first-order (F1) reaction model fits in the fractional conversion range of 0.4–1.0. The predicted kinetic equations for both the samples were in good agreement with the experimental kinetic data.

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Zhao, Wei, Xinglian Yang, Jingying Wang, Yongkang Zheng e Yue Zhou. "Evaluation of Thermodynamic and Chemical Kinetic Models for Hypersonic and High-Temperature Flow Simulation". Applied Sciences 13, n. 17 (4 settembre 2023): 9991. http://dx.doi.org/10.3390/app13179991.

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Significant thermochemical nonequilibrium effects always exist in the flow field around hypersonic vehicle at extreme flight condition. Previous studies have proposed various thermodynamic and chemical kinetic models to describe the thermochemical nonequilibrium processes in hypersonic and high-temperature flow. However, different selections from such models might lead to remarkable variations in computational burden and prediction accuracy, which is still a matter of being unclear. In the present study, different commonly studied models for calculating the thermochemical nonequilibrium are systematically evaluated. The 5-, 7- and 11-species chemical kinetic models of Dunn-Kang, Gupta and Park together with the one- and two-temperature models are employed respectively to simulate the hypersonic flows over a standard cylinder with the radius of 1 m by HyFLOW, which is a commercial software based on the numerical solution of Navier-Stokes equations. Three flight conditions of FIRE Ⅱ classical flight trajectory are employed in the study. It shows that the differences between the results of the Dunn-Kang, Gupta and Park chemical kinetic models with the same number of species are small, but the Gupta model predicts the most conservative values of the wall heat flux. When only the order of magnitude and distribution trends of the pressure and wall heat flux are concerned, the one-temperature model combined with 5-species chemical reaction model can be used for a rapid prediction. While the accurate flow solution is required, the two-temperature model conjugated with Gupta 11-species model is recommended, especially at the conditions of extremely high altitude and Mach number.

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Aworanti, Oluwafunmilayo Abiola, Oluseye Omotoso Agbede, Samuel Enahoro Agarry, Ayobami Olu Ajani, Oyetola Ogunkunle, Opeyeolu Timothy Laseinde, S. M. Ashrafur Rahman e Islam Md Rizwanul Fattah. "Decoding Anaerobic Digestion: A Holistic Analysis of Biomass Waste Technology, Process Kinetics, and Operational Variables". Energies 16, n. 8 (12 aprile 2023): 3378. http://dx.doi.org/10.3390/en16083378.

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The continual generation and discharge of waste are currently considered two of the main environmental problems worldwide. There are several waste management options that can be applied, though anaerobic digestion (AD) process technology seems to be one of the best, most reliable, and feasible technological options that have attracted remarkable attention due to its benefits, including the generation of renewable energy in the form of biogas and biomethane. There is a large amount of literature available on AD; however, with the continuous, progressive, and innovative technological development and implementation, as well as the inclusion of increasingly complex systems, it is necessary to update current knowledge on AD process technologies, process variables and their role on AD performance, and the kinetic models that are most commonly used to describe the process-reaction kinetics. This paper, therefore, reviewed the AD process technologies for treating or processing organic biomass waste with regard to its classification, the mechanisms involved in the process, process variables that affect the performance, and the process kinetics. Gazing into the future, research studies on reduced MS-AD operational cost, integrated or hybrid AD-biorefinery technology, integrated or hybrid AD-thermochemical process, novel thermochemical reactor development, nutrient recovery from integrated AD-thermochemical process, and solid and liquid residual disposal techniques are more likely to receive increased attention for AD process technology of biomass wastes.

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Ferracci, Valerio, e David M. Rowley. "Kinetic and thermochemical studies of the ClO + ClO + M ⇄ Cl2O2 + M reaction". Physical Chemistry Chemical Physics 12, n. 37 (2010): 11596. http://dx.doi.org/10.1039/c0cp00308e.

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Nayak, Suresh K., e Theodore J. Burkey. "Photosubstitution of iron carbonyl phosphine complexes: quantum yield, kinetic, and thermochemical studies". Journal of the American Chemical Society 115, n. 14 (luglio 1993): 6391–97. http://dx.doi.org/10.1021/ja00067a064.

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Karasavvas, Evgenios, Athanasios Scaltsoyiannes, Andy Antzaras, Kyriakos Fotiadis, Kyriakos Panopoulos, Angeliki Lemonidou, Spyros Voutetakis e Simira Papadopoulou. "One-Dimensional Heterogeneous Reaction Model of a Drop-Tube Carbonator Reactor for Thermochemical Energy Storage Applications". Energies 13, n. 22 (12 novembre 2020): 5905. http://dx.doi.org/10.3390/en13225905.

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Calcium looping systems constitute a promising candidate for thermochemical energy storage (TCES) applications, as evidenced by the constantly escalating scientific and industrial interest. However, the technologically feasible transition from the research scale towards industrial and highly competitive markets sets as a prerequisite the optimal design and operation of the process, especially corresponding reactors. The present study investigates for the first time the development of a detailed, one-dimensional mathematical model for the steady-state simulation of a novel drop-tube carbonator reactor as a core equipment unit in a concentrated solar power (CSP)-thermochemical energy storage integration plant. A validated kinetic mathematical model for a carbonation reaction (CaO(s) + CO2(g) → CaCO3(s)) focused on thermochemical energy storage conditions was developed and implemented for different material conditions. The fast gas–solid reaction kinetics conformed with the drop-tube reactor concept, as the latter is suitable for very fast reactions. Reaction kinetics were controlled by the reaction temperature. Varying state profiles were computed across the length of the reactor by using a mathematical model in which reactant conversions, the reaction rate, and the temperature and velocity of gas and solid phases provided crucial information on the carbonator’s performance, among other factors. Through process simulations, the model-based investigation approach revealed respective restrictions on a tailor-made reactor of 10 kWth, pointing out the necessity of detailed models as a provision for design and scale-up studies.

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Moens, Eli K. C., Yoshi W. Marien, Alessandro D. Trigilio, Kevin M. Van Geem, Paul H. M. Van Steenberge e Dagmar R. D’hooge. "Kinetic Monte Carlo Convergence Demands for Thermochemical Recycling Kinetics of Vinyl Polymers with Dominant Depropagation". Processes 11, n. 6 (26 maggio 2023): 1623. http://dx.doi.org/10.3390/pr11061623.

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As societal interest in recycling of plastics increases, modeling thermochemical recycling of vinyl polymers, e.g., via pyrolysis or reactive extrusion, becomes increasingly important. A key aspect remains the reliability of the simulation results with fewer evaluation studies regarding convergence as in the polymerization or polymer reaction engineering field. Using the coupled matrix-based Monte Carlo (CMMC) framework, tracking the unzipping of individual chains according to a general intrinsic reaction scheme consisting of fission, β-scission, and termination, it is however illustrated that similar convergence demands as in polymerization benchmark studies can be employed, i.e., threshold values for the average relative error predictions on conversion and chain length averages can be maintained. For this illustration, three theoretical feedstocks are considered as generated from CMMC polymer synthesis simulations, allowing to study the effect of the initial chain length range and the number of defects on the convergence demands. It is shown that feedstocks with a broader chain length distribution and a long tail require a larger Monte Carlo simulation volume, and that the head–head effects play a key role in the type of degradation mechanism and overall degradation rate. A minimal number of chains around 5 × 105 is needed to properly reflect the degradation kinetics. A certain degree of noise can be allowed at the higher carbon-based conversions due to the inevitable decrease in number of chains.

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Vorob’ev, A. M., N. S. Belinskaya, D. A. Afanasieva, S. B. Arkenova, T. A. Kaliev, E. B. Krivtsov, E. N. Ivashkina e N. I. Krivtsova. "Mathematical Modeling of the Vacuum Gas Oil Hydrotreatment". Kataliz v promyshlennosti 22, n. 5 (29 settembre 2022): 40–52. http://dx.doi.org/10.18412/1816-0387-2022-5-40-52.

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Thermochemical properties of molecules and thermodynamic characteristics of vacuum distillate hydrotreatment were calculated by quantumchemical methods. A kinetic model of the hydrotreatment process was developed using a formalized transformation scheme of hydrocarbons. The developed kinetic model was employed in numerical studies aimed to estimate the effect of the feedstock composition on the residual content of heteroatomic components in the product of vacuum gas oil hydrotreatment, the effect of temperature on the content of aromatic hydrocarbons, nitrogen and sulfur in the hydrotreatment product, and the effect of the hydrogen-containing gas consumption on the content of sulfur and hydrogen sulfide in the hydrotreated vacuum gas oil.

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Khiri, Dorra, Sonia Taamalli, Duy Quang Dao, Thanh-Binh Nguyen, Laurent Gasnot, Florent Louis, Ivan Černuśák e Abderrahman El Bakali. "Thermochemical and kinetic studies of hydrogen abstraction reaction from C16H10 isomers by H atoms". Computational and Theoretical Chemistry 1201 (luglio 2021): 113257. http://dx.doi.org/10.1016/j.comptc.2021.113257.

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Zickus, Michael A., Sara Koepke, Changtong Hao, Kevin Chong e Victor Ryzhov. "The thermochemical studies of protonated amine–crown ether complexes: Extension of the kinetic method". International Journal of Mass Spectrometry 312 (febbraio 2012): 173–78. http://dx.doi.org/10.1016/j.ijms.2011.05.004.

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Zhu, Qiaoqiao, Yanwei Zhang, Zhi Ying, Shujie Wang, Zhihua Wang, Junhu Zhou e Kefa Cen. "Kinetic and thermodynamic studies of the Bunsen reaction in the sulfur–iodine thermochemical process". International Journal of Hydrogen Energy 38, n. 21 (luglio 2013): 8617–24. http://dx.doi.org/10.1016/j.ijhydene.2013.04.110.

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Dinh, Viet Quoc, e Van Dinh Son Tho. "STUDY ON THERMOGRAVIMETRIC AND KINETIC OF AGRICULTURAL RESIDUES IN VIETNAM". Vietnam Journal of Science and Technology 55, n. 4 (11 agosto 2017): 436. http://dx.doi.org/10.15625/2525-2518/55/4/9027.

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Thermochemical conversion of biomass has been studied extensively over the last decades. For the design, optimization and modeling of thermochemical conversion processes, such as fixed bed pyrolysis, a sound understanding of pyrolysis is essential. In this study, the thermal degradation of different agricultural residue species as rice husk (RH), corn cob (CC) and sugarcane bagasse (SGB) has been investigated using thermo-gravimetric. The kinetic parameters of three agricultural in the inert atmosphere are also calculated by Flynn-Wall-Ozawa method (FWO) and compared with acacia wood’s one. The average activated energy of rice husk lower than activated energy of acacia wood. The average activated energy of corn cob and sugarcane bagasse are higher than the activated energy of acacia wood thermal degradation. This result has important role in the reactor design for using agricultural residue to generate power such as pyrolysis or gasification.

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Safavi, Aysan, Christiaan Richter e Runar Unnthorsson. "Mathematical Modeling and Experiments on Pyrolysis of Walnut Shells Using a Fixed-Bed Reactor". ChemEngineering 6, n. 6 (1 dicembre 2022): 93. http://dx.doi.org/10.3390/chemengineering6060093.

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Pyrolysis is a low-emission and sustainable thermochemical technique used in the production of biofuels, which can be used as an alternative to fossil fuels. Understanding the kinetic characterization of biomass pyrolysis is essential for process upscaling and optimization. There is no accepted model that can predict pyrolysis kinetics over a wide range of pyrolysis conditions and biomass types. This study investigates whether or not the classical lumped kinetic model with a three-competitive reaction scheme can accurately predict the walnut shell pyrolysis product yields. The experimental data were obtained from walnut shell pyrolysis experiments at different temperatures (300–600 °C) using a fixed-bed reactor. The chosen reaction scheme was in good agreement with our experimental data for low temperatures, where the primary degradation of biomass occurred (300 and 400 °C). However, at higher temperatures, there was less agreement with the model, indicating that some other reactions may occur at such temperatures. Hence, further studies are needed to investigate the use of detailed reaction schemes to accurately predict the char, tar, and gas yields for all types of biomass pyrolysis.

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Dumlu, Lütfiye, Asli Seyhan Ciggin, Stefan Ručman e N. Altınay Perendeci. "Pretreatment, Anaerobic Codigestion, or Both? Which Is More Suitable for the Enhancement of Methane Production from Agricultural Waste?" Molecules 26, n. 14 (9 luglio 2021): 4175. http://dx.doi.org/10.3390/molecules26144175.

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Pretreatment and codigestion are proven to be effective strategies for the enhancement of the anaerobic digestion of lignocellulosic residues. The purpose of this study is to evaluate the effects of pretreatment and codigestion on methane production and the hydrolysis rate in the anaerobic digestion of agricultural wastes (AWs). Thermal and different thermochemical pretreatments were applied on AWs. Sewage sludge (SS) was selected as a cosubstrate. Biochemical methane potential tests were performed by mixing SS with raw and pretreated AWs at different mixing ratios. Hydrolysis rates were estimated by the best fit obtained with the first-order kinetic model. As a result of the experimental and kinetic studies, the best strategy was determined to be thermochemical pretreatment with sodium hydroxide (NaOH). This strategy resulted in a maximum enhancement in the anaerobic digestion of AWs, a 56% increase in methane production, an 81.90% increase in the hydrolysis rate and a 79.63% decrease in the technical digestion time compared to raw AWs. On the other hand, anaerobic codigestion (AcoD) with SS was determined to be ineffective when it came to the enhancement of methane production and the hydrolysis rate. The most suitable mixing ratio was determined to be 80:20 (Aws/SS) for the AcoD of the studied AWs with SS in order to obtain the highest possible methane production without any antagonistic effect.

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Li, Hailong, Jiefeng Chen, Weijin Zhang, Hao Zhan, Chao He, Zequn Yang, Haoyi Peng e Lijian Leng. "Machine-learning-aided thermochemical treatment of biomass: a review". Biofuel Research Journal 10, n. 1 (1 marzo 2023): 1786–809. http://dx.doi.org/10.18331/brj2023.10.1.4.

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Thermochemical treatment is a promising technique for biomass disposal and valorization. Recently, machine learning (ML) has been extensively used to predict yields, compositions, and properties of biochar, bio-oil, syngas, and aqueous phases produced by the thermochemical treatment of biomass. ML demonstrates great potential to aid the development of thermochemical processes. The present review aims to 1) introduce the ML schemes and strategies as well as descriptors of the input and output features in thermochemical processes; 2) summarize and compare the up-to-date research in both ML-aided wet (hydrothermal carbonization/liquefaction/gasification) and dry (torrefaction/pyrolysis/gasification) thermochemical treatment of biomass (i.e., predicting the yields, compositions, and properties of oil/char/gas/aqueous phases as well as thermal conversion behavior or kinetics); and 3) identify the gaps and provide guidance for future studies concerning how to improve predictive performance, increase generalizability, aid mechanistic and application studies, and effectively share data and models in the community. The development of biomass thermochemical treatment processes is envisaged to be greatly accelerated by ML in the near future.

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Messerle, V. Е., M. N. Orynbasar e A. B. Ustimenko. "Simulation and experiment of plasma ignition of low-grade coal". Горение и плазмохимия 22, n. 1 (25 marzo 2024): 27–36. http://dx.doi.org/10.18321/cpc22(1)27-36.

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A plasma-coal burner is studied utilizing a model of plasma thermochemical preparation of coal for combustion, implemented in the PlasmaKinTherm program. For boiler start-up and coal combustion stabilization, plasma-coal burners do not require fuel oil or gas. The PlasmaKinTherm program combines thermodynamics and kinetics to describe the thermochemical preparation of fuel in the plasma-coal burner volume. The purpose of the simulation was to determine the conditions for plasma ignition of low-grade coal. A numerical study was carried out of the influence of the plasmatron power on the ignition of the air mixture (coal + air). High-ash Ekibastuz coal was used in the calculations. The distributions of temperature and velocity of gas and coal particles and concentrations of products of plasma thermochemical preparation of coal for combustion along the length of the burner were calculated. As a result of the analysis of the processes of plasma ignition of coal, their main patterns were revealed, including the shift of the maximum temperatures and velocities of the products of thermochemical preparation of coal for combustion upstream (towards the plasma torch), as well as the fact that the maximum values of temperatures and velocities of the products do not depend on power plasmatron. At the plasmatron power determined by kinetic modeling, experiments were conducted to test and validate the ignition and combustion conditions for a highly reactive two-component fuel torch. The assumptions made during the development of the mathematical model were confirmed by comparing the calculations with experimental data.

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Fuentes, Manuel, Diego Pulido, Edward Fuentealba, Alvaro Soliz, Norman Toro, Atul Sagade e Felipe M. Galleguillos Madrid. "Direct Solar Thermal Water-Splitting Using Iron and Iron Oxides at High Temperatures: A Review". Applied Sciences 14, n. 16 (12 agosto 2024): 7056. http://dx.doi.org/10.3390/app14167056.

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Green hydrogen is poised to play a crucial role in the energy-transition process in developed countries over the coming years, particularly in those countries aiming to achieve net-zero emissions. Consequently, the for green hydrogen is expected to rise significantly. This article explores the fundamental methods of producing hydrogen, focusing on the oxidation reaction within a thermochemical solar cycle for the dissociation of steam. Solar thermochemical cycles have been extensively researched, yet they remain in the development stage as research groups strive to identify optimal materials and conditions to enhance process efficiency, especially at high temperatures. The article analyses theoretical foundations drawn from exhaustive scientific studies related to the oxidation of iron in steam, the relationship with the activation energy of the corrosive process, thermodynamic aspects, and the kinetic model of a heterogeneous reaction. Additionally, it presents various mechanisms of high-temperature oxidation, pH effects, reactors, and materials (including fluidized beds). This scientific review suggests that hydrogen production via a thermochemical cycle is more efficient than production via electrochemical processes (such as electrolysis), provided the limitations of the cycle’s reduction stage can be overcome.

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Lizardo-Huerta, Juan-Carlos, Sonia Taamalli, Kanika Sood, Laurent Gasnot, Florent Louis, Abderrahman El Bakali e Luc-Sy Tran. "Thermochemical and kinetic studies of H-abstraction reaction of benzofurans and benzodioxins by H-atoms". Computational and Theoretical Chemistry 1209 (marzo 2022): 113589. http://dx.doi.org/10.1016/j.comptc.2022.113589.

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Prazhennik, Yu G., O. I. Khovavko, Yu V. Marchuk, O. V. Snigur e A. A. Nebesniy. "THEORETICAL AND EXPERIMENTAL STUDIES OF METHODS OF THERMOCHEMICAL PROCESSING OF MUNICIPAL SOLID WASTES". Energy Technologies & Resource Saving, n. 2 (17 giugno 2022): 62–71. http://dx.doi.org/10.33070/etars.2.2022.05.

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Thermodynamic analysis of thermochemical processing of MSW of Ukrainian origin is performed. The software TERRA was used for calculations, with the help of which the equilibrium indicators of the reaction products were calculated. It is shown that the accuracy of the calculation results is determined by the accuracy of the used value of the lower calorific value. Control calculations were performed for the following substances: pure carbon, glucose, cellulose, polyethylene. Thermodynamic analysis of the possibilities of thermochemical utilization was performed on the basis of studies of the composition of MSW obtained directly from landfills in Ukraine. It is shown that the adiabatic temperature significantly depends on the content of oxides — ash components — and their chemical composition. For experimental researches the laboratory installation was developed and constructed. Measurement of temperature, weight and composition of gas during researches was carried out by means of system on the basis of personal computer using the module of connection of territorial-distribution sensors I-7018 and I-7520 — isolated module of a converter of communication channel SR-232/RS-485. For the first time, a combination of thermogravity analysis with a possibility of chromatographic control of a composition of the gas phase at all stages of heat treatment was proposed for studies of MSW heat treatment. For the first time, kinetic studies of wood gasification were performed using gravimetric analysis with simultaneous determination of the gas phase composition. Bibl. 14, Fig. 4, Tab. 2.

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Marriott, Robert A., Payman Pirzadeh, Juan J. Marrugo-Hernandez e Shaunak Raval. "Hydrogen sulfide formation in oil and gas". Canadian Journal of Chemistry 94, n. 4 (aprile 2016): 406–13. http://dx.doi.org/10.1139/cjc-2015-0425.

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Hydrogen sulfide (H2S) can be a significant component of oil and gas upstream production, where H2S can be naturally generated in situ from reservoir biomass and from sulfate-containing minerals through microbial sulfate reduction and (or) thermochemical sulfate reduction. On the other hand, the technologies employed in oil and gas production, especially from unconventional resources, also can contribute to generation or delay of appearance of H2S. Steam-assisted gravity drainage and hydraulic fracturing used in production of oil sands and shale oil/gas, respectively, can potentially convert the sulfur content of the petroleum into H2S or contribute excess amounts of H2S during production. A brief overview of the different classes of chemical reactions involved in the in situ generation and release of H2S is provided in this work. Speciation calculations and reaction mechanisms are presented to explain why thermochemical sulfate reduction progresses at faster rates under low pH. New studies regarding the degradation of a hydraulic fracture fluid additive (sodium dodecly sulfate) are reported for T = 200 °C, p = 17 MPa, and high ionic strengths. The absence of an ionic strength effect on the reaction rate suggests that the rate-limiting step involves the reaction of neutral species, such as elemental sulfur. This is not the case with other thermochemical sulfate reduction studies at T > 300 °C. These two different kinetic regimes complicate the goal of extrapolating laboratory results for field-specific models for H2S production.

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Saqib, Muhammad, Eugene Arthur-Baidoo, Milan Ončák e Stephan Denifl. "Electron Attachment Studies with the Potential Radiosensitizer 2-Nitrofuran". International Journal of Molecular Sciences 21, n. 23 (24 novembre 2020): 8906. http://dx.doi.org/10.3390/ijms21238906.

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Nitrofurans belong to the class of drugs typically used as antibiotics or antimicrobials. The defining structural component is a furan ring with a nitro group attached. In the present investigation, electron attachment to 2-nitrofuran (C4H3NO3), which is considered as a potential radiosensitizer candidate for application in radiotherapy, has been studied in a crossed electron–molecular beams experiment. The present results indicate that low-energy electrons with kinetic energies of about 0–12 eV effectively decompose the molecule. In total, twelve fragment anions were detected within the detection limit of the apparatus, as well as the parent anion of 2-nitrofuran. One major resonance region of ≈0–5 eV is observed in which the most abundant anions NO2−, C4H3O−, and C4H3NO3− are detected. The experimental results are supported by ab initio calculations of electronic states in the resulting anion, thermochemical thresholds, connectivity between electronic states of the anion, and reactivity analysis in the hot ground state.

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BAŞMAN, Gökhan, Mustafa Merih ARIKAN, Cevat ARISOY e Kelami ŞEŞEN. "A KINETIC STUDY OF THERMOCHEMICALLY BORIDED AISI 316L STAINLESS STEEL". Journal of Scientific Reports-A, n. 052 (29 marzo 2023): 279–96. http://dx.doi.org/10.59313/jsr-a.1092135.

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Biomaterials are used in different parts of human body as replacement implants in medical applications. An implant material should have high biocompatibility, corrosion and wear resistance, and suitable mechanical properties in terms of safety and long-service period. There are only a few biocompatible implant materials: AISI316L stainless steel is one of the materials used in this type of applications. They have relatively poor wear resistance. Boriding being a thermochemical diffusion treatment is one of the processes to improve their wear resistance. Borides are formed by introducing boron atoms by diffusion onto a substrate surface and they are non-oxide ceramics and could be very brittle. The growth kinetics of boride layer is analyzed by measuring depth of layers as a function of boriding time within a temperature range. In this study, the effects of Ekabor-2 bath on formation mechanism and properties of boride layer in thermochemical diffusion boriding of AISI316L stainless steel were investigated. Different temperatures and durations were applied in boriding operations and hardness, optical microscopy, XRD, EPMA and SEM studies were performed to detect the properties of boride layers. It was found that thickness of boride layer increased with increasing temperature and time; the basic phase in the boride layer formed was Fe2B and FeB phase also formed. It was also found that surface hardness values of borided materials increased depending on temperature and time of boriding process; surface hardness values of borided materials are approximately 10 times higher than surface hardness values of non-borided AISI316L stainless steel and formation activation energy of boride layer is 149.3 kjmol-1.

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29

Lee, Xin Jiat, Lai Yee Lee, Suyin Gan, Suchithra Thangalazhy-Gopakumar e Hoon Kiat Ng. "Biochar potential evaluation of palm oil wastes through slow pyrolysis: Thermochemical characterization and pyrolytic kinetic studies". Bioresource Technology 236 (luglio 2017): 155–63. http://dx.doi.org/10.1016/j.biortech.2017.03.105.

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30

Feng, Yupeng, Xuhan Li, Haowen Wu, Chaoran Li, Man Zhang e Hairui Yang. "Critical Review of Ca(OH)2/CaO Thermochemical Energy Storage Materials". Energies 16, n. 7 (25 marzo 2023): 3019. http://dx.doi.org/10.3390/en16073019.

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Abstract (sommario):

Thermal energy storage is an essential technology for improving the utilization rate of solar energy and the energy efficiency of industrial processes. Heat storage and release by the dehydration and rehydration of Ca(OH)2 are hot topics in thermochemical heat storage. Previous studies have described different methods for improving the thermodynamic, kinetic, and structural stability of Ca(OH)2 to improve energy storage density, energy storage rate, and cycle stability, respectively. Here, the mechanisms and effects of different techniques on the performance improvement of Ca(OH)2 and some common problems were reviewed. Specific problems were also clarified based on the characteristics of different technologies. Finally, suggestions for the future development of Ca(OH)2 heat storage materials were provided.

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31

Chueh, William C., e Sossina M. Haile. "A thermochemical study of ceria: exploiting an old material for new modes of energy conversion and CO 2 mitigation". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, n. 1923 (28 luglio 2010): 3269–94. http://dx.doi.org/10.1098/rsta.2010.0114.

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Abstract (sommario):

We present a comprehensive thermodynamic and kinetic analysis of the suitability of cerium oxide (ceria) for thermochemical fuel production. Both portions of the two-step cycle, (i) oxygen release from the oxide at 1773 and 1873 K under inert atmosphere, and (ii) hydrogen release upon hydrolysis at 1073 K, are examined theoretically as well as experimentally. We observe gravimetric fuel productivity that is in quantitative agreement with equilibrium, thermogravimetric studies of ceria. Despite the non-stoichiometric nature of the redox cycle, in which only a portion of the cerium atoms change their oxidation state, the fuel productivity of 8.5–11.8 ml of H 2 per gram of ceria is competitive with that of other solid-state thermochemical cycles currently under investigation. The fuel production rate, which is also highly attractive, at a rate of 4.6–6.2 ml of H 2 per minute per gram of ceria, is found to be limited by a surface-reaction step rather than by ambipolar bulk diffusion of oxygen through the solid ceria. An evaluation of the thermodynamic efficiency of the ceria-based thermochemical cycle suggests that, even in the absence of heat recovery, solar-to-fuel conversion efficiencies of 16 to 19 per cent can be achieved, assuming a suitable method for obtaining an inert atmosphere for the oxygen release step.

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32

Stegenta-Dąbrowska, Sylwia, Karolina Sobieraj, Jacek A. Koziel, Jerzy Bieniek e Andrzej Białowiec. "Kinetics of Biotic and Abiotic CO Production during the Initial Phase of Biowaste Composting". Energies 13, n. 20 (19 ottobre 2020): 5451. http://dx.doi.org/10.3390/en13205451.

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Abstract (sommario):

Knowledge of kinetic parameters of CO production during biowaste composting is significantly important for the prediction of its course and estimation of total gas quantity. This allows increasing the control of the process, to minimize its negative impact on the environment and to protect the occupational safety of employees exposed to CO in the biowaste composting plant. For the first time, a full study of the influence of temperature and biowaste sterilization on the kinetics of CO production is presented. The lab-scale experiments used a mixture of green waste, dairy cattle manure, and sawdust in two variants: sterilized and non-sterilized samples. The process was carried out in controlled temperature reactors with measuring the concentrations of CO, O2, and CO2 every 12 h.CO production and k value increased with temperature. However, higher CO production was observed in biotic conditions between 10~50 °C, suggesting the biotic CO formation and 1st-order kinetics. The abiotic (thermochemical) process was more efficiently generating CO above 50 °C, described with a 0-order kinetic model. Additionally, the rate constant (k) value of CO production under biotic conditions was increasing up to a temperature of 60 °C, above which a slight decrease in CO production rate was observed at 70 °C. The presented results are the basis for further studies focused on the feasibility of (1) the mitigation and (2) valorization of CO production during the biowaste biostabilization are warranted.

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33

Yang, Jeehyun, Murthy S. Gudipati, Bryana L. Henderson e Benjamin Fleury. "High-fidelity Reaction Kinetic Modeling of Hot-Jupiter Atmospheres Incorporating Thermal and UV Photochemistry Enhanced by Metastable CO(a³Π)". Astrophysical Journal 947, n. 1 (1 aprile 2023): 26. http://dx.doi.org/10.3847/1538-4357/acbd9b.

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Abstract (sommario):

Abstract A detailed modeling of simultaneous UV-photochemical and thermochemical processes in exoplanet atmosphere-like conditions is essential for the analysis and interpretation of a vast amount of current and future spectral data from exoplanets. However, a detailed reaction kinetic model that incorporates both UV photochemistry and thermal chemistry is challenging due to the massive size of the chemical system as well as the lack of understanding of photochemistry compared to thermal-only chemistry. Here, we utilize an automatic chemical reaction mechanism generator to build a high-fidelity thermochemical reaction kinetic model later then incorporated with UV photochemistry enhanced by metastable triplet-state carbon monoxide (a3Π). Our model results show that two different photochemical reactions driven by Lyα photons (i.e., H2 + CO(a3Π) → H + HCO and CO(X1Σ+) + CO(a3Π) → C(3P) + CO2) can enhance thermal chemistry resulting in significant increases in the formation of CH4, H2O, and CO2 in H2-dominated systems with trace amounts of CO, which qualitatively matches the observations from previous experimental studies. Our model also suggests that at temperatures above 2000 K, thermal chemistry becomes the dominant process. Finally, the chemistry simulated up to 2500 K does not produce any larger species such as C3 species, benzene, or larger (i.e., PAHs). This might indicate that the photochemistry of C2 species such as C2H2 might play a key role in the formation of organic aerosols observed in a previous experimental study.

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34

Kulik, Tetiana, Nataliia Nastasiienko, Borys Palianytsia, Mykola Ilchenko e Mats Larsson. "Catalytic Pyrolysis of Lignin Model Compound (Ferulic Acid) over Alumina: Surface Complexes, Kinetics, and Mechanisms". Catalysts 11, n. 12 (10 dicembre 2021): 1508. http://dx.doi.org/10.3390/catal11121508.

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Abstract (sommario):

Studies of the thermochemical properties of the important model compound of lignin-ferulic acid (FA) and its surface complexes are substantial for developing technologies for catalytic pyrolysis of renewable biomass into biofuels and lignin-derived chemicals as well as for bio-oil upgrading. In this work, the catalytic pyrolysis of ferulic acid over alumina was studied by temperature-programmed desorption mass spectrometry (TPD MS), in situ FT-IR spectroscopy, thermogravimetric analysis, and DFT calculations. We established that both the carboxyl group and the active groups (HO and CH3O) of the aromatic ring interact with the alumina surface. We calculated the kinetic parameters of formation of the main products of catalytic pyrolysis: 4-vinylguaiacol, guaiacol, hydroxybenzene, benzene, toluene, cresol, naphthalene, and PACs. Possible methods of their forming from the related surface complexes of FA are suggested.

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35

Zelenov, Vladislav V., Elena V. Aparina, Alexander V. Loboda, Alexander S. Kukui, Alexander F. Dodonov, Sergei A. Kashtanov e Nicolai N. Aleinikov. "Mass Spectrometric Studies of Physical, Thermochemical and Reactive Properties of Xenon Fluorides, Xenon Oxides and Xenon Oxyfluorides". European Journal of Mass Spectrometry 8, n. 3 (giugno 2002): 233–46. http://dx.doi.org/10.1255/ejms.495.

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Abstract (sommario):

Using a reactor with a flowing diffusion cloud coupled to a high-resolution, low-energy electron-impact ionization mass spectrometer, mechanistic, kinetic and thermochemical characteristics of gas-phase reactions with the participation of charged and neutral xenon oxides, xenon fluorides and xenon oxyfluorides have been investigated. Ionization energies for XeF, XeF2, XeF4, XeO3, XeO4, XeOF4 molecules and appearance energies for the ions formed from these molecules were obtained. Based on experimental and reference data, the enthalpies of XeO3 and XeOF4 formation were refined and a number of binding energies in the parent and fragment ions were calculated. For electron-impact ionization, the ionization cross-sections for Xe, XeF2, XeF4 and XeOF4 proved to correlate with a semi-empirical principle of full ionization. Based on the temperature dependencies of saturated vapor pressures for XeO4, XeOF4 and XeO2F2, their enthalpies of evaporation, sublimation and melting were determined. The mechanisms of gas-phase reactions between H atoms and neutral XeF2, XeF4, XeF6, XeO4 and XeOF4 were studied.

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36

Maslennikov, G., G. Nikitina, A. Nikitin, P. Osipov e A. Ryzhkov. "Physical and numerical simulation of heat and mass transfer in the furnace of a thermogravimetric analyzer". Eurasian Journal of Mathematical and Computer Applications 12, n. 3 (settembre 2024): 61–72. http://dx.doi.org/10.32523/2306-6172-2024-12-3-61-72.

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Abstract (sommario):

A numerical study of the processes of heat and mass transfer in the furnace of a thermogravimetric analyzer was carried out, aimed at improving the accuracy of determining the kinetic characteristics of samples during their thermal transformations in different media. Validation of the model and prognostic estimates were carried out in relation to specially conducted thermogravimetric studies of the conversion of fossil and renewable carbon-containing raw materials in successive processes of decarbonization (combustion) and carbonation (mineralization of ash residue). The application of the study results allows to calculate the actual concentrations of the reagent over the sample uncontrolled by the device during pulsed switching of media and the actual temperatures of the sample during its thermochemical transformations.

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37

Fedunik-Hofman, Bayon e Donne. "Comparative Kinetic Analysis of CaCO3/CaO Reaction System for Energy Storage and Carbon Capture". Applied Sciences 9, n. 21 (29 ottobre 2019): 4601. http://dx.doi.org/10.3390/app9214601.

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Abstract (sommario):

The calcium carbonate looping cycle is an important reaction system for processes such as thermochemical energy storage and carbon capture technologies, which can be used to lower greenhouse gas emissions associated with the energy industry. Kinetic analysis of the reactions involved (calcination and carbonation) can be used to determine kinetic parameters (activation energy, pre-exponential factor, and the reaction model), which is useful to translate laboratory-scale studies to large-scale reactor conditions. A variety of methods are available and there is a lack of consensus on the kinetic parameters in published literature. In this paper, the calcination of synthesized CaCO3 is modeled using model-fitting methods under two different experimental atmospheres, including 100% CO2, which realistically reflects reactor conditions and is relatively unstudied kinetically. Results are compared with similar studies and model-free methods using a detailed, comparative methodology that has not been carried out previously. Under N2, an activation energy of 204 kJ mol-1 is obtained with the R2 (contracting area) geometric model, which is consistent with various model-fitting and isoconversional analyses. For experiments under CO2, much higher activation energies (up to 1220 kJ mol-1 with a first-order reaction model) are obtained, which has also been observed previously. The carbonation of synthesized CaO is modeled using an intrinsic chemical reaction rate model and an apparent model. Activation energies of 17.45 kJ mol-1 and 59.95 kJ mol-1 are obtained for the kinetic and diffusion control regions, respectively, which are on the lower bounds of literature results. The experimental conditions, material properties, and the kinetic method are found to strongly influence the kinetic parameters, and recommendations are provided for the analysis of both reactions.

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38

Hakhnazaryan, T. L., e H. A. Matnishyan. "The Mechanism of Formation of Structural Heterogeneitics in Polyaniline". Journal of Composites and Biodegradable Polymers 2, n. 1 (5 febbraio 2014): 2–9. http://dx.doi.org/10.12974/2311-8717.2014.02.01.1.

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Abstract (sommario):

The regularities of polyaniline formation, the influence of various additions, conditions of synthesis of the main and intermediate, including hydrolysis, products on the structure of obtained materials are studied. Making use kinetic and thermochemical methods the mechanisms of polycondensation by N-phenyl-1,4-benzoquinonodiimine, initiation macromolecules growth as result of anilines addition to electrophile quinonoimine groups of the polymer are confirmed. The chemical aspects of reactions leading to formation of structural heterogeneitics, branchings, breaching of effective conjugation, termination and sewing together of chains are analyzed.

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39

Wee, Melvin Xin Jie, Bridgid Lai Fui Chin, Agus Saptoro, Jaka Sunarso, Chew Jiuan Jing e Suzana Yusup. "Thermogravimetric analysis of face mask waste: Kinetic analysis via iso-conversional methods". MATEC Web of Conferences 377 (2023): 01003. http://dx.doi.org/10.1051/matecconf/202337701003.

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Abstract (sommario):

The surge of face mask waste in response to the global pandemic has proven to be a liability to the environment. Microfibers from plastic constituents of the face mask would cause microplastic pollution in the water bodies. Fortunately, these waste could be converted into renewable source of energy via thermochemical method, i.e. pyrolysis. However, the studies on the thermal decomposition of face masks and their kinetic mechanisms are not well-established. The aim of this paper focuses on the prospects of pyrolysis at low to high heating rates ranging from 10 °C min-1 to 100 °C min-1, to cater for the slow pyrolysis and fast pyrolysis modes. Following this, the thermal degradation behaviour of the face mask waste was studied via thermogravimetric analysis which determined the single peak temperature degradation range at 218 to 424 °C at 10 °C min-1, and maximum degradation rate was determined at 172.51 wt.% min-1 at 520 °C, with heating rate of 100 °C min-1. Flynn-Wall-Ozawa (FWO) and Starink method was employed to determine the average activation energy and average pre-exponential factor of the pyrolysis process of face mask waste. i.e., 41.31 kJ mol-1 and 0.9965, 10.43 kJ mol-1 and 0.9901 for FWO and Starink method, respectively.

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40

Shaw, Matthew G., Matthew S. Humbert, Geoffrey A. Brooks, M. Akbar Rhamdhani, Alan R. Duffy e Mark I. Pownceby. "Metal and Oxide Sublimation from Lunar Regolith: A Kinetics Study". Minerals 13, n. 1 (4 gennaio 2023): 79. http://dx.doi.org/10.3390/min13010079.

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Abstract (sommario):

When considering the extraction of metals from lunar regolith for use in space, one reductive method of interest is vacuum thermal dissociation. Given the high vacuum environment on the Moon, the sub-liquidus operation of such a process, i.e., sublimation, warrants investigation. In the current work, the kinetics of the vacuum sublimation of the more volatile major oxides found in the lunar regolith, Na2O, K2O, and FeO, are evaluated. Two distinct factors are accounted for in the current work: the change in the evaporation flux due to temperature; and the reduction in available surface area for evaporation due to sintering of the feedstock. Surface area change due to the sintering of compressed LMS-1 regolith simulant pellets was quantified via a Brunauer–Emmett–Teller analysis. The surface area of the samples was measured to vary from 3.29 m2/g in the unsintered sample, to 1.04 m2/g in the samples sintered at 800 °C, and down to 0.09 m2/g in the sample sintered at 1150 °C. Evaporation flux was calculated using the Hertz–Knudsen–Langmuir equation using saturated vapor pressures predicted from the FactSage thermochemical package and verified against Knudsen Effusion Mass Spectroscopy data from tests conducted on lunar regolith sample #12022. The combination of these studies resulted in the conclusion that no local maxima in evaporation rate below the melting point was found for the current system, as such the highest rate of sublimation was determined to be 1200 °C for all species, at temperatures of 1200 °C and above, partial melting of the material occurs. The predicted maximum rate of sublimation for the species Fe, Na, and K at 1200 °C was 0.08, 1.38, and 1.02 g/h/g of regolith, respectively. It is noted that significant variation was seen between FactSage predictions of saturated vapor pressures and the measured values. Future work generating detailed thermochemical databases to predict the behavior of complex systems similar in composition to lunar regolith would benefit the accuracy of similar kinetic studies in the future.

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Zendah, Houda, Ismail Khattech e Mohamed Jemal. "Thermochemical and kinetic studies of the acid attack of “B” type carbonate fluorapatites at different temperatures (25–55)°C". Thermochimica Acta 565 (agosto 2013): 46–51. http://dx.doi.org/10.1016/j.tca.2013.04.033.

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42

Ojolo, S. J., C. A. Osheku e M. G. Sobamowo. "Analytical Investigations of Kinetic and Heat Transfer in Slow Pyrolysis of a Biomass Particle". International Journal of Renewable Energy Development 2, n. 2 (17 giugno 2013): 105–15. http://dx.doi.org/10.14710/ijred.2.2.105-115.

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Abstract (sommario):

The utilization of biomass for heat and power generation has aroused the interest of most researchers especially those of energy .In converting solid fuel to a usable form of energy,pyrolysis plays an integral role. Understanding this very important phenomenon in the thermochemical conversion processes and representing it with appropriate mathematical models is vital in the design of pyrolysis reactors and biomass gasifiers. Therefore, this study presents analytical solutions to the kinetic and the heat transfer equations that describe the slow pyrolysis of a biomass particle. The effects of Biot number, temperature and residence time on biomass particle decomposition were studied. The results from the proposed analytical models are in good agreement with the reported experimental results. The developed analytical solutions to the heat transfer equations which have been stated to be “analytically involved” showed average percentageerror and standard deviations 0.439 and 0.103 from the experimental results respectively as compared with previous model in literature which gives average percentage error and standard deviations 0.75 and 0.106 from the experimental results respectively. This work is of great importance in the design of some pyrolysis reactors/units and in the optimal design of the biomass gasifiers.

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Voglar, Jure, e Blaž Likozar. "Screening of Metal Reduction Potential for Thermochemical Hydrogen Storage". Processes 12, n. 5 (15 maggio 2024): 1004. http://dx.doi.org/10.3390/pr12051004.

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Abstract (sommario):

The screening of all non-radioactive metals without lanthanides for thermochemical hydrogen storage was performed based on physical chemistry calculations. The thermodynamic data were collected from the NIST (National Institute of Standards and Technology) public data repository, which was followed by calculations regarding the change in enthalpy, entropy, Gibbs free energy and equilibrium reaction temperature. The results were critically evaluated based on thermodynamic parameters, viable metals were identified, and their hydrogen storage densities and energy–enthalpy ratios were evaluated. The elements viable for controlled thermochemical hydrogen storage via the reversible reduction and oxidation of metal oxides and metals are manganese (Mn), iron (Fe), molybdenum (Mo) and tungsten (W). Manganese has the largest theoretical potential for hydrogen storage with reversible reduction and oxidation of metal oxides and metals. The second candidate is iron, while the other two (Mo and W) have much lower potential. More research efforts should be dedicated to experimental testing of the identified metals (Mn, Fe, Mo and W) and their different oxides for thermochemical hydrogen storage capabilities both on laboratory and pilot scales. Ferromanganese alloy(s) might also prove itself as an efficient and affordable thermochemical hydrogen storage material. Our theoretical investigation expanded the knowledge on thermochemical hydrogen storage and is accompanied with a brief literature review revealing the lack of experimental studies, especially on oxidation of metals with water vapor occurring during the hydrogen release phase of the cycle. Consequently, accurate modelling of transport, kinetics and other phenomena during hydrogen storage and release is scarce.

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Unruh, Tobias, e Peter Vöhringer. "Thermal Isomerization of [Co(acac)2(N3)(py)] in Liquid Solution Studied by Time-Resolved Fourier-Transform Infrared Spectroscopy". Zeitschrift für Physikalische Chemie 234, n. 7-9 (27 agosto 2020): 1549–66. http://dx.doi.org/10.1515/zpch-2020-0006.

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Abstract (sommario):

AbstractThe thermally induced stereochemical interconversion between the trans and cis isomers of [Co(acac)2(N3)(py)] in liquid solution is investigated with time-resolved Fourier-transform infrared spectroscopy. The complex is synthesized stereo-selectively in its trans-form. Upon dissolution of the trans-form, the kinetic build-up of the cis-form is evidenced by the spectro-temporal evolution of the FTIR-spectrum. The individual isomer-specific component spectra are in good agreement with calculated spectra obtained from density functional theory. The rate constants of the forward and backward reactions responsible for the trans-cis isomerization equilibrium are derived from the kinetic traces in combination with existing thermochemical data from the literature. Moreover, the temperature-dependence of the rate constants are in line with Arrhenius activation energies of (122 ± 8) kJ/mol and (109 ± 8) kJ/mol for the forward and backward reactions, respectively. DFT-calculations suggest that the stereochemical rearrangement is caused by a pyridine rebound mechanism involving penta-coordinated square-pyramidal [Co(acac)2(N3)]-intermediates.

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Schröder, Detlef, e Helmut Schwarz. "Activation of methane by gaseous platinum(II) ions PtX+ (X = H, Cl, Br, CHO)". Canadian Journal of Chemistry 83, n. 11 (1 novembre 2005): 1936–40. http://dx.doi.org/10.1139/v05-217.

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Abstract (sommario):

The gas-phase reactions of methane with the platinum(II) ions PtX+ with X = H, Cl, Br, and CHO are studied by mass spectrometry. The PtX+ ions are generated by electrospray ionization of methanolic solutions of hexachloroplatinic acid and hexabromoplatinic acid, respectively. Small to moderate intramolecular kinetic isotope effects determined for the CH(D) bond activation of CH2D2 suggest that the activation of methane by gaseous PtX+ cations is subject to thermochemical control by the product channels. In addition, the PtCl2+ cation is also able to activate methane, whereas PtCl3+ is unreactive under the conditions chosen. Key words: gas-phase reactions, mass spectrometry, methane activation, platinum bromide, platinum chloride.

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Zhai, Chunjie, Fei Peng, Xiaodong Zhou e Lizhong Yang. "Pyrolysis and ignition delay time of poly(methyl methacrylate) exposed to ramped heat flux". Journal of Fire Sciences 36, n. 3 (14 febbraio 2018): 147–63. http://dx.doi.org/10.1177/0734904118757742.

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Abstract (sommario):

Usually, the constant heat flux is used in the previous studies of polymeric pyrolysis. However, the ramped heat flux may be more realistic under a fire condition. For further understandings of polymer pyrolysis in the early stage of fire, the influences of ramped heat flux on pyrolysis of poly(methyl methacrylate) were experimentally and theoretically investigated. Linearly and quadratically ramped heat fluxes were controlled by the output power of a radiative heater. Surface temperature, mass loss rate, and ignition time were experimentally obtained to explore the thermochemical stability of poly(methyl methacrylate) under ramped heat fluxes. A one-dimensional model was used to predict the pyrolysis process, where kinetic parameters were evaluated by a genetic algorithm. Finally, ignition criteria including critical surface temperature and critical mass loss rate were revisited. We observed that the two ignition criteria give similar ignition time when the heat flux increases fast.

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Vasileiadou, Agapi, e Costas Tsioptsias. "Thermochemical and Kinetic Analysis of Combustion of Plastic Wastes and Their Blends with Lignite". Applied Sciences 13, n. 14 (13 luglio 2023): 8141. http://dx.doi.org/10.3390/app13148141.

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Abstract (sommario):

The management of plastic waste is considered to be among the major environmental problems that must be urgently addressed. For various reasons, recycling of plastic waste is not always feasible. In this study, a comprehensive evaluation of a mixture of plastic wastes (of the municipal solid wastes, MSW) as potential fuel is performed. Precisely, the combustion of plastic waste and the co-combustion of plastic waste-lignite blends are studied. Thermochemical characteristics, chemical composition, and kinetic parameters are measured/estimated. The environmental impact of these samples is also evaluated in terms of CO2 maximum potential emissions and ash production. In addition, the ash quality and its risk for slagging problems are explored. The random mixture of plastic waste revealed extremely high energy content (34 MJ/kg), which is higher than some well-established liquid fuels, e.g., ethanol and lower ash content (~5 wt.%), with lower activation energy and a higher maximum rate of mass loss (~9%/min) than lignite. Besides the much lower amount of produced ash, plastic waste, despite its higher carbon content, exhibits lower CO2 maximum potential emissions (~75 g CO2/MJ). The composition of the ash produced by plastic waste and lignite is different quantitatively but qualitatively is of the same type (similar medium risk ash). The superior characteristics of plastic waste are also evident in the blends. Provided that toxic emissions are captured, the utilization of plastic waste through combustion seems to be an attractive approach for simultaneous waste management and energy production, especially for plastic waste of limited recycling potential.

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Galwey, Andrew K. "Thermal reactions involving solids: a personal view of selected features of decompositions, thermal analysis and heterogeneous catalysis". Journal of Thermal Analysis and Calorimetry 142, n. 3 (24 marzo 2020): 1123–44. http://dx.doi.org/10.1007/s10973-020-09461-w.

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Abstract (sommario):

Abstract Convinced that some recent trends in the literature concerned with reactions involving solids have been unproductive, even discouraging interest in the subject, this reviewer analyses the reasons and charts a way forward. In particular, two topics are discussed: thermal analysis and activation energy. Thermal analysis, automated collection and interpretation of kinetic data for solid(?)-state decompositions, resulted in huge numbers of publications between late 1970s and 2010. Measurements were frequently minimalistic (few, often no, confirmatory tests complemented rate data). Kinetic data interpretations were based on the Arrhenius activation model, inapplicable to these assumed, usually unconfirmed, solid-state(?) reactions. Energy distributions within crystalline reactants differ from those of ‘free-flying’ gaseous reactants, and thus, mechanistic proposals are entirely speculative. Such studies yielded little more than the reaction temperature: no meaningful insights into reaction chemistry, controls, mechanisms. Despite my several highly critical articles, these inconsequential studies continued. Overall, this now sidelined topic impacted adversely on solid-state chemistry, activation energy, E. Concurrently with the above studies, L'vov published a theoretical explanation for the magnitude of E: the Congruent Dissociative Volatilisation (CDV), thermochemical approach. This was also ignored by the ‘Thermoanalytical Community’, possibly because it assumes an initial volatilisation step: it appears that many solid-state scientists are prejudiced against mechanisms involving a phase change. The value of this novel theory (CDV) in identifying controls and mechanisms of solid-state reactions is discussed here. This review is positive: an interesting branch of main-stream chemistry remains open for exploration, expansion, explanation and exploitation!

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Saeed, Saad, Mahmood Saleem, Abdullah Durrani, Junaid Haider, Muzaffar Riaz, Sana Saeed, Muhammad Abdul Qyyum, Abdul-Sattar Nizami, Mohammad Rehan e Moonyong Lee. "Determination of Kinetic and Thermodynamic Parameters of Pyrolysis of Coal and Sugarcane Bagasse Blends Pretreated by Ionic Liquid: A Step towards Optimization of Energy Systems". Energies 14, n. 9 (29 aprile 2021): 2544. http://dx.doi.org/10.3390/en14092544.

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Abstract (sommario):

Pyrolysis behavior of ionic liquid (IL) pretreated coal and sugarcane bagasse (SCB) blends through thermogravimetric analysis (TGA) was studied. Three blends of coal and SCB having 3:1, 1:1, and 1:3 ratios by weight were treated with 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) at 150 °C for 3 h. Untreated and IL treated blends were then analyzed under pyrolytic conditions in a TGA at a constant ramp rate of 20 °C/min. Kinetic and thermodynamic parameters were evaluated using ten Coats-Redfern (CR) models to assess reaction mechanism. Results showed that the untreated blends followed a definite pattern and were proportional to the concentration of SCB in the blends. IL treated blends exhibited a higher average rate of degradation and total weight loss, indicating that IL had disrupted the cross-linking structure of coal and lignocellulosic structure of SCB. This will enhance the energy generation potential of biomass through thermochemical conversion processes. The lower activation energy (Ea) was calculated for IL treated blends, revealing facile thermal decomposition after IL treatment. Thermodynamic parameters, enthalpy change (ΔH), Gibbs free energy change (ΔG), and entropy change (ΔS), revealed that the pyrolysis reactions were endothermic. This study would help in designing optimized thermochemical conversion systems for energy generation.

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Akyürek, Zuhal. "Synergetic Effects during Co-Pyrolysis of Sheep Manure and Recycled Polyethylene Terephthalate". Polymers 13, n. 14 (19 luglio 2021): 2363. http://dx.doi.org/10.3390/polym13142363.

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Abstract (sommario):

Continuous growth in energy demand and plastic waste production are two global emerging issues that require development of clean technologies for energy recovery and solid waste disposal. Co-pyrolysis is an effective thermochemical route for upgrading waste materials to produce energy and value added products. In this study, co-pyrolysis of sheep manure (SM) and recycled polyethylene terephthalate (PET) was studied for the first time in a thermogravimetric analyzer (TGA) in the temperature range of 25–1000 °C with heating rates of 10–30–50 °C min−1 under a nitrogen atmosphere. The synergetic effects of co-pyrolysis of two different waste feedstock were investigated. The kinetic parameters are determined using the Flynn–Wall–Ozawa (FWO) model. The results revealed that the mean values of apparent activation energy for the decomposition of sheep manure into a recycled polyethylene terephthalate blend are determined to be 86.27, 241.53, and 234.51 kJ/mol, respectively. The results of the kinetic study on co-pyrolysis of sheep manure with plastics suggested that co-pyrolysis is a viable technique to produce green energy.

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