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This work examined the possibilities and limitations of model-free and model-based methods related to decrypting the kinetic complexity of multi-step thermo-oxidative degradation processes (as a testing system, a [4-(hydroxymethyl)phenoxymethyl] polystyrene resin was used), monitored by thermal analysis (TGA-DTG-DTA) techniques. It was found that isoconversional methods could successfully determine the correct number of process stages and presence of multiple reactions based on derived Ea(α) profiles and identify the negative dependence of the rate constant on the temperature. These methods could not overcome the problem that arose due to mass transfer limitations. The model-based method overcame more successfully the problem associated with mass transfer because its calculation machinery had capabilities for the correct solution of the total mass balance equation. However, a perfect fit with the experimental data was not achieved due to the dependence on the thermal history of the contribution (ctb.) of a given reaction step inside a fitting procedure cycle. On the other hand, through this approach, it was possible to estimate the rate-controlling steps of the process regarding the influence of the heating rate. It was found that for consecutive reaction mechanisms, the production of benzaldehyde and gases in high yields was controlled by the heating rate, where low heating rates were strongly recommended (≤10 K/min). Also, it was shown that the transport phenomenon may be also the rate-determining step (within the set of "intrinsic" kinetic parameters). It was also established that external heat transfer controls the overall rate, where the "pure" kinetic control regime had not been reached but was approached when lowering the temperature and size of the resin particles. [ABSTRACT FROM AUTHOR]

Thermo-chemical conversion of cigarette butt filters (CBF) waste was investigated using various thermal analysis techniques (simultaneous TG-DTG-DTA and DSC methods) at different heating rates in an inert atmosphere. Thermo- and thermophysical properties of waste material were discussed, from the point of view of chemical structure and the influence of experimental parameters on the conversion process. It was established that acetyl groups of plasticizer (triacetin) interact with cellulose acetate through dipolar interactions and hydrogen bonding's. Influence of these polar interactions can affect the position of glass transition temperature, Tg, of CBF. Based on estimated value of Tg from DSC analysis, it was found that cellulose acetate present in CBF has degree of substitution equals to 2.8, where the presence of cellulose triacetate was confirmed. It was assumed that an increase of degree of substitution leads to decline in the crystallinity. A decline of crystallinity causes the reduction of hydroxyl groups, leading to less organized chains, and whereby decreasing of inter-molecular interactions through hydrogen bonding. Based on the examination of thermophysical characteristics of the tested material, it was found that both, the heat capacity and the thermal inertia of material linearly increase with temperature, during pyrolysis progression. It was concluded that the type of bio-char produced in this process would have a large capacity to store the heat, which may depend on the formed particles size diameter and porosity. Furthermore, it was inferred that magnitude drops of thermal conductivity, κ, after Tg depends on the material fibrillation. [ABSTRACT FROM AUTHOR]

With the onset of the migrant crisis in Europe, irregular migration is becoming a significant security problem for European leaders and citizens. As a result, there has also been a change in the public opinion of European countries, because many citizens associate irregular migration with terrorism and other security problems. In line with the growing importance of irregular migration as a security problem, the research aimed to determine changes in migration trends in Serbia, that is, on the ‘Balkan route’ of migration since 2015, when the migrant crisis in Europe began. Results that can roughly indicate the profile of an irregular migrant found on the territory of the Republic of Serbia were obtained in this research, conducted between June and August 2020 on a sample of 50 irregular migrants. An irregular migrant is a person from Afghanistan, of Islamic religion, uneducated, and of a poor financial status. They want to go to Germany for money, and they cross the borders of the countries located on the ‘Balkan route’ on foot, occasionally using the services of smugglers. Additionally, they have no problems with the border police of Serbia. The conducted research can contribute to gaining new knowledge about the problem of irregular migration, primarily about the trends that are different than they were at the time of the migrant crisis in 2015. Unlike previous research, this research is unique in that it also refers to the work of the border police and the attitude of border police officers toward irregular migrants. [ABSTRACT FROM AUTHOR]

Thermo-chemical conversion via the pyrolysis of cigarette butt (CB) filters was successfully valorized and upcycled in the pre-carbonization and carbonization stages. The pre-carbonization stage (devolatilization) of the precursor material (cellulose acetate filter, r-CAcF) was analyzed by micro-scale experiments under non-isothermal conditions using TG-DTG-DTA and DSC techniques. The results of a detailed kinetic study showed that the decomposition of r-CAcF takes place via complex mechanisms, including consecutive reaction steps and two single-step reactions. Consecutive stages include the α-transition referred to as a cellulose polymorphic transformation (cellulose I → II) through crystallization mechanism changes, where a more thermodynamically ordered system was obtained. It was found that the transformation rate of cellulose I → II ('cellulose regeneration') is strongly affected by the presence of alkali metals and the deacetylation process. Two single-step reactions showed significant overlapping behavior, which involves a nucleation-controlled scission mechanism (producing levoglucosan, gaseous products, and abundant radicals) and hydrolytic decomposition of cellulose by catalytic cleavage of glycosidic bonds with the presence of an acidic catalyst. A macro-scale experiment showed that the operating temperature and heating rate had the most notable effects on the total surface area of the manufactured carbon. A substantial degree of mesoporosity with a median pore radius of 3.1695 nm was identified. The presence of macroporosity on the carbon surface and acidic surface functional groups was observed. [ABSTRACT FROM AUTHOR]

A powdered PVA/CaCO3 nanocomposite carrier was successfully fabricated for effective loading of small bioactive molecules, such as vitamin D3 (VD3). Generation of, namely, VD3/PVA/CaCO3 nanocomposite scaffold was carried out through an adsorption mechanism as a loading route of an active compound onto a powder carrier. Developed composites were characterized by structural, morphological and thermal analyses techniques, such as X-ray powder diffraction (XRPD), Fourier-transform infrared (FTIR) spectroscopy, MALDI (matrix-assisted laser desorption/ionization) – mass spectrometry (MS), Brunauer–Emmett–Teller (BET) – NLDFT (Non-local Density Functional Theory) method, scanning electron microscopy (SEM), simultaneous TG-DTG and coupled TG-MS. XRD results showed that the average crystallite size of synthesized VD3/PVA/CaCO3 amounts 32.93 nm exhibiting microstrain presence, where PVA incorporation causes non-uniform calcite lattice distortion. SEM analysis showed that VD3/PVA/CaCO3 nanocomposite scaffold contains agglomerated rhomboidal calcite particles with VD3 particles of irregular shapes attached. Fabricated VD3/PVA/CaCO3 clearly showed the existence of calcite "staircase" dendrites as the aftermath of inhibiting the effect of impurities on the growth of crystals in normal directions. It was determined that the decomposition of PVA additionally enhances the thermal stability of VD3, through the stabilization effect by acting on van der Waal's forces during polyene formation, confirmed by MALDI-TOF MS results. [ABSTRACT FROM AUTHOR]

The pyrolysis of [4-(hydroxymethyl)phenoxymethyl]polystyrene (Wang) resin was studied by dynamic simultaneous thermogravimetric analysis (TGA) and derivative thermogravimetry techniques. The studied resin is used as the most commonly polymer supports in the peptide synthesis. A developed experimental master plots (exp-MP) model is presented that can be used to describe in more detail the pyrolysis of the resin established upon 4-hydroxybenzyl alcohol (PHB) on polystyrene, occurring throughout TGA experiments. This model assumes that the Wang resin is pyrolyzed through three parallel independent reaction steps, whereby their separation was performed through deconvolution procedure of the complex conversion rate curves. The mechanistic nature of each stage of Wang resin pyrolysis was explained by applying a combination of kinetic models such as diffusion mechanism, random nucleation and subsequent growth and chemical reactions mechanisms. The kinetic triplet parameters obtained in the present paper were then compared with those available in the literature. Within this kinetic study, the fraction distribution analysis (via distributed reactivity model) was performed, enabling reliable prediction of liquid products produced during the pyrolysis of the solid support of the Wang resin. [ABSTRACT FROM AUTHOR]

The presented paper deals with the influence of the heating rate on combustion characteristics (reactivity and reactivity evaluation, ignition index (Di), burnout index (Df), the combustion performance index (S), and the combustion stability index (RW)) of the protective coronavirus face masks. Two types of commonly used face masks in different state (new and exploited) were investigated by TG-DTG analysis in an air atmosphere, directly coupled with mass spectrometry (MS). Based on the experimental results, the impact of ultimate and proximate analysis data on the evolved gas analysis (EGA) was discussed. Also, the derived values from thermo-analytical (TA) data were compared with the literature reports, related to individual constitutive face mask materials. According to the performed research, it was established that different maximal reaction rate values at various heating rates indicate the complex nature of coronavirus face mask thermo-oxidative degradation, which is stimulated with carbon oxidation reactions and volatile matter (VM) release. By detailed analysis of obtained TG-DTG profiles, it was established that process takes place through the multiple-step reaction pathways, due to many vigorous radical reactions, causes by polymers degradation. The performed research was done to evaluate the possible utilization of coronavirus waste to energy production and sustainable pandemic environmental risk reduction. [ABSTRACT FROM AUTHOR]

The aim of this study is to explain the consequences of the occurrence of enthalpy–entropy compensation (EEC) and isoequilibrium relationship during slow pyrolysis of cigarette butt filters (CBFs), consisting cellulose acetate (AC) as the main component. By using model-free and model-based kinetic methods and thermodynamic calculations, the complete reaction mechanism and extrathermodynamic issues about investigated process are completely resolved. It was established that compensation phenomenon where isoequilibrium temperature occurs is a consequence of formation of low-entropy molecular structure (cellulose II) and breaking of hydrogen bonds. Consequently, it was concluded that mechanisms which include a formation of low-entropy molecular structure and H-bonds breakage enter the changes in both enthalpy and entropy, which compensate each other. For the cellulose II generation, it was necessary to invest energy which represents use up energy. This “wasted” energy turns into work for creation of cellulose II molecular structures, whereby additional energy was provided from “local” decomposition reactions (which were identified in the established process mechanism) that arise from pyrolysis of starting material. Therefore, it was concluded that for “local reactions”, a negative ΔS° value was identified, but for the global process, the entropy change retained a positive value. Considering thermodynamic effects manifested through compensation temperature found below glass transition temperature (Tg) in the undercooling conditions, it was concluded that small amounts of plasticizers affect reduction of free volume in the glassy state. Obtained results indicated a decrease in β-relaxation mode of cellulose acetate by an abatement of the polymer free volume.Graphical abstract: The aim of this study is to explain the consequences of the occurrence of enthalpy–entropy compensation (EEC) and isoequilibrium relationship during slow pyrolysis of cigarette butt filters (CBFs), consisting cellulose acetate (AC) as the main component. By using model-free and model-based kinetic methods and thermodynamic calculations, the complete reaction mechanism and extrathermodynamic issues about investigated process are completely resolved. It was established that compensation phenomenon where isoequilibrium temperature occurs is a consequence of formation of low-entropy molecular structure (cellulose II) and breaking of hydrogen bonds. Consequently, it was concluded that mechanisms which include a formation of low-entropy molecular structure and H-bonds breakage enter the changes in both enthalpy and entropy, which compensate each other. For the cellulose II generation, it was necessary to invest energy which represents use up energy. This “wasted” energy turns into work for creation of cellulose II molecular structures, whereby additional energy was provided from “local” decomposition reactions (which were identified in the established process mechanism) that arise from pyrolysis of starting material. Therefore, it was concluded that for “local reactions”, a negative ΔS° value was identified, but for the global process, the entropy change retained a positive value. Considering thermodynamic effects manifested through compensation temperature found below glass transition temperature (Tg) in the undercooling conditions, it was concluded that small amounts of plasticizers affect reduction of free volume in the glassy state. Obtained results indicated a decrease in β-relaxation mode of cellulose acetate by an abatement of the polymer free volume. [ABSTRACT FROM AUTHOR]

• Effective thermal conversion of coal slag through multiple reactions scheme. • Process was governed by variations in melt viscosity and by the composition gradient. • Successful SiO 2 dissolution was achieved over low activation energy catalytic pathway. • At T = T iso , conversion process is freed from dependence on temperature and pressure. • Enthalpy-entropy compensation effect was identified, with "tunnel effect" phenomenon. This study provides insight into benefits of thermo-chemical conversion of coal slag as recovery process into value-added products. This research involves kinetic analysis of process conducted through non-isothermal thermal analysis measurements, with additional raw material characterization. Kinetic results showed that decomposition proceeds through two consecutive reactions steps (first one, including anorthite P 1̅ → I 1̅ phase transition, and then production of incongruent melting product (ternary system: CaO·Al 2 O 3 ·2SiO 2 (CAS 2), where viscosity of slag changes), and second one including dehydration and formation of meta-muscovite, and subsequently, thermal disruption of muscovite de-hydroxylated phase, which proceeds with breaking of octahedral Al–O bonds), and one single-step reaction (attributed to CO-reduction of hematite to magnetite). Thermodynamic results showed an existence of physically meaningful isokinetic temperature (T iso), which corresponds to active vibrational frequency of surroundings of SiO 2 reaction site, manifested through Si‒O bond weakening by catalytic reaction of freed hydroxide ion (OH−). It was concluded that at temperature T = T iso , the course of process loses its dependence on temperature and pressure, regulating changes between thermodynamic parameters, through enthalpy-entropy compensation (EEC) effect. [Display omitted] [ABSTRACT FROM AUTHOR]

The preliminary thermogravimetric studies of co-pyrolyzed low rank coals (lignites Kostolac and Kolubara) with waste materials (spent coffee ground and waste rubber granulate) in a form of blends have been performed. Thermal analysis measurements of blend samples were carried out in a nitrogen, atmosphere at three different heating rates of 10, 15, and 20 K per minute. The coal-waste blends were prepared in the percentage ratios of 90:10, 80:20, and 70:30. This work analyzed the synergy analysis for considered blends shown via descriptive parameters during co-pyrolysis process. According to the performed analysis, the presence of synergistic effect was identified, where strong interactions were also observed. For lignite-spent coffee ground blends, it was found that two factors which affect the synergy effect with coal are concentration of added biomass material and the heating rate. For lignite-tire rubber granulate blends, the blending ratio take on a decisive role for positive consequences of a synergistic effect (ratios below 30% of tire rubber granulate in coals are desirable). Also, in this work the influence of micro-scale condition parameters such as heating rate (as the experimental regulatory factor) was analyzed on the magnitude response of synergism during co-pyrolysis. [ABSTRACT FROM AUTHOR]

The issue of accumulated seashell waste has been increasingly addressed in the studies of its applicability as a secondary source of calcium carbonate. In this work, the mechanism of the thermo-oxidative degradation of two types of mollusk shells (Dosinia exoleta—DE and oyster Ostrea edulis—OE) was investigated using simultaneous thermal analysis. Physicochemical characterization of raw and calcined materials was performed by XRD and SEM techniques. Results show that increasing powder particle size and heating rate affect the degradation of investigated shells differently and have a significant contribution to released quantities of CO2. It was proposed that the calcination rate of DE powders is determined by the strain-induced collapse of CO2-deficient calcite at its interface with crystalline CaO rods-like structure, with simultaneous expulsion of CO2. A much higher CO2 concentration was identified during the degradation of OE powders, favoring the carbonation reaction and, consequently, increasing the temperature and activation energy of the investigated reaction. Under elevated CO2 concentration, the CaO aggregation step is enhanced by slower reaction kinetics at lower temperatures since both CO2 desorption and structural transformations are probably hindered. The proposed mechanism leads to a meaningful correlation between thermodynamic quantities (enthalpy–entropy compensation) in the form of an iso-kinetic relationship. [ABSTRACT FROM AUTHOR]

As representative among biomass feedstocks, Poplar fluff was chosen to analyze the pyrolysis properties of this new biofuel. Thermogravimetry under inert (argon) atmosphere at the heating rates of 5, 10, 15, and 20 °C min−1 was employed in the investigation of thermal processing of studied biomass. The determination of kinetic parameters and estimation of reaction mechanism function were done through application of the state-of-the-art NETZSCH Kinetics NEO software. With this aim, the various model-free models and model-based calculations were implemented. The obtained results showed that the most appropriate kinetic model to describe the thermal decomposition of Poplar fluff sample was n-dimensional acceleratory Avrami–Erofeev model (An) for three-step consecutive reaction mechanism. Governed reaction pathway in pyrolysis process represents fragmentation reactions which arise from levoglucosan decomposing that permits permanent gases and refractory tars, where diffusion-controlled process is involved in the sample devolatilization. The modulated and multiple-step predictions of pyrolysis process were also carried out. [ABSTRACT FROM AUTHOR]

The detailed kinetic analysis of slow pyrolysis process of apricot (Prunus armeniaca L.) kernal shells has been estimated, under non-isothermal conditions, through thermogravimetric analysis and derivative thermogravimetry. Thermal decomposition was implemented using four different heating rates (5, 10, 15, and 20 °C per minute), with consideration of how this parameter effects on the process kinetics. The higher heating rates provoke the shift of thermoanalytical curves towards more elevated temperatures. Using isoconversional differential method, the variation of activation energy, Ea, with conversion fraction, α, was detected, and pyrolysis reaction profile was discussed. After resolving the pyrolysis rate curves of individual biomass constituents, the temperature and conversion ranges of their thermal transformations were clearly identified. In the latter stage of analysis, every identified reaction step was considered through mechanistic description, which involves selection of the appropriate kinetic model function. The comparison of the results as well as discrepancies between them has been discussed. The corresponding rate-law equations related to thermal decomposition reactions of all biomass constituents present in the tested agricultural waste material have been identified. [ABSTRACT FROM AUTHOR]

Goal of this work is to establish technical feasibility and fundamentals of producing activated carbon from plane tree seeds biomass for porous materials derivation. Bio-chars produced via carbonization from plane tree seeds precursor were activated in CO2 at 750 and 850 °C, during various residence times. Their surface area and porosity were characterized by N2 adsorption at 77 K. Surface areas energy magnitudes of oxidation reaction by CO2, which are closely related to applied activation temperature. Result showed that high temperature activated carbon had higher gas adsorption as compared to activated carbon obtained from lower temperature during two-hour residence time. Breakthrough behavior was detected at 850 °C where surface reactions dominate, and it is characterized by autocatalytic kinetic model under designed conditions. Both, temperature and CO2 concentration in vicinity of solid surface effect on breakthrough time of adsorbent. Derived bio-chars are converted into high quality activated carbons, with surface area of 776.55 m²/g, where micro-pores with pore diameters less than 2 nm prevail. Produced activated carbons have properties comparable with commercially available activated carbons, which can be successfully used for removal of harmful gaseous pollutants toward air purification. [ABSTRACT FROM AUTHOR]

In order to clarify relationship between apricot kernel shell biomass slow pyrolysis mechanism and its main constituents (viz. hemicelluloses, cellulose and lignin), the reactivity effects of main constituents on pyrolysis characteristics were determined by the non-isothermal simultaneous thermal analysis. It was found that four-step (parallel) reaction model is suitable for studying the slow pyrolysis process, within the semi-global model which excludes the strong interaction between biomass constituents (pseudo-components). The application of the proposed model was allowed by the results obtained from KAS iterative isoconversional (model-free) approach. The valorization of the model was confirmed by the process optimization. The complex (cumulative) apricot kernel shell pyrolysis rate curves at different heating rates are successfully resolved into the individual decomposition rate curves (arising from thermal conversion of hemicelluloses, cellulose, and primary/secondary lignin fragments) by four-parameter Fraser–Suzuki function. Besides hemicelluloses and cellulose pyrolyses, the proposed model distinguishes primary and secondary lignin reactions, which enhance the gaseous products releasing (primarily CO and CO2 gases) and charification of the solid residue (increased the bio-char yield). [ABSTRACT FROM AUTHOR]

Simultaneous thermal analysis (TG–DTA) of low-rank coals from different annual periods (2015 and 2018) which originate from Kolubara and Nikola Tesla A (TENT A) coal-fired power plants was studied to identify their combustion characteristics and self-ignition risks. In order to investigate kinetics of thermo-oxidative degradation, model-free models including the Friedman and Kissinger–Akahira–Sunose methods were applied. In accordance with obtained kinetic results, numerical optimization of combustion process was implemented. Homogeneous and heterogeneous types of ignition were identified for the tested coals, and factors that affect their occurrence are the used heating rate and volatile matter content. From thermal susceptibility graph, it was found that the tested coals expand in a wide range of self-ignition risk, depending on their coal rank. The youngest coal (TENT A (2018)) has the largest propensity to self-ignite among high-ranking coals. It was found that less tendency of 2018 coals to show true isokinetic temperature in comparison with 2015 coals is a consequence of intraparticle diffusion limitations, and change of char properties, at higher conversion values. Gamma spectrometry analysis of coals showed that higher concentration of 40K radionuclide (which is in mineral composition) may contribute through its deposition on available sites, decreasing surface area for reaction with oxidizing species. [ABSTRACT FROM AUTHOR]

The combustion reactivity of plane tree seeds biomass feedstock was studied using the thermogravimetry. The effects of atmosphere (O2/Ar) and different oxygen concentrations (O2/Ar = 20:80% and O2/Ar = 50:50%) on the combustion characteristics were investigated. When combustion atmosphere changes from O2/Ar = 50:50% to O2/Ar = 20:80% (reducing oxygen concentrations), the burnout temperature increases by 29.50 °C for tested biomass. Obtained results demonstrate the ease of ignition of investigated lignocellulosic material for O2/Ar = 50:50% ratio compared with O2/Ar = 20:80% ratio, and the actual trend is maintained under the condition when the heating rate increases. The reducing of oxygen concentration strongly influenced the amount of final residue products, particularly at higher heating rates (beyond 10 °C min−1). Kinetic analysis applied to investigated process shows strongly dependencies of both the apparent activation energy (E) and pre-exponential factor (logA) with conversion (α), especially in devolatilization and combustion of volatiles reaction stages. Large variation in E is attributed to existence of multiple parallel reactions. In order to solve this problem, the deconvolution technique that uses Fraser–Suzuki function was applied. It was shown that Fraser–Suzuki function fits successfully kinetic rate curves of entire combustion process, assuming the best selected nth-order reaction model. [ABSTRACT FROM AUTHOR]

Slow pyrolysis characteristics of agricultural residue feedstocks (corn brakes, wheat straw, and hazelnut shell) were investigated by simultaneous thermal analysis (STA–TG–DTG–DSC), coupled with mass spectrometry (MS). Thermal decomposition of agricultural residues was divided into three stages, corresponding to removal of water, devolatilization, and formation of bio-char. It was found that differences in thermal behavior of samples are due to differences in their composition. The MS results showed that H2, CH4, H2O, CO2 (C3H8), CO, and C2H6 were the main gaseous products released during pyrolysis. It was shown that hazelnut shells could be a good combustion fuel, since during its pyrolysis at high temperature, more gaseous products compared to other systems are very favored. For hazelnut shell pyrolysis, the CO2 can be used on the large scale for the production of CO-rich syngas. [ABSTRACT FROM AUTHOR]

The traditional view that only the police are responsible for security at sports events has largely been abandoned in the sense that stewards have more important place. Hus is also recognized in the Serbian legislation, in the standards of the Law on Private Security (LPS), the Law on the Prevention of Violence and MiSRonduct at Sports Events (LPl'MSE), the Law on Public Assembly', and the international regulations of sports federations. The Council of Europe Convention on an Integrated Safety, Security and Service Approach at Football Matches and Other Sports Events - No. 21S. (CETS 21S), together with the Recommendation REC (2015) 1, and its annexes, which supersedes all previous recommendations, resolutions and statements, has also contributed to defining the role of stewards. Recommendation has become an integral part of the Convention (CETS 21S). Common to all the aforementioned regulations is that the stewarding operations can be handled by persons who have completed special training. Unlike international regulations that provide extensive training for stewards, the existing programs in Serbia envisage very few hours of training. The work of stewards would certainly be aided by the improvement of certain legal regulations governing this area. The Republic of Serbia is not yet a signatory' to the Convention (CETS 218), and it is necessaiyfor the authorities to accede to its signing and ratification in order for Serbia to adopt the newly established Eurovean standards in this field as soon as vossible. [ABSTRACT FROM AUTHOR]

During the utilization of coal in large power plants, one of the major logistical issues is related to spontaneous ignition of the coal. This characteristic of coal depends on the rank and type of the coal, the content of the moisture and volatile matter as well as particle size distribution. This paper presents the novel approach for determination of spontaneous ignition potential of the coal developed as the internal laboratory experimental method. The experimental tests were performed by thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG) of tested samples at five different heating rates: 3, 5, 7, 10 and 20 K min−1 under an air atmosphere. The TGA results were used for determination of tangent slope of the mass loss rate curves in the zone of the release of volatiles at considered heating rates for all coal samples. The linear interpolation of the data obtained by performed tangent slope analysis and heating rates provides the straight line unique for each tested sample. According to the standard method, the slope of the obtained straight line is defined as thermogravimetric index of spontaneous ignition (TG spi). In addition, a new formula for determination of TG spi index was provided. Three different coal samples were analyzed and classified according to the spontaneous ignition potential, based on the obtained values for TG spi by standard procedure and also using a newly proposed method. By varying the gradient of linear dependence of self-heating coefficient against reference temperatures (T ref,i), the mass and heat transfer limitations for different coals were discussed. [ABSTRACT FROM AUTHOR]

Slow pyrolysis (gradual heating over a wide range of temperatures) characteristics of various biomasses (corn brakes, wheat straw, and hazelnut shell) were investigated by simultaneous thermal analysis (STA-TGA-DTG-DSC), coupled with mass spectrometry. Thermal decomposition of these samples was divided into three stages corresponding to removal of water, devolatilization, and formation of bio-char. It was found that differences in thermal behavior of the samples are due to differences in their composition. The mass spectrometry results showed that H2, CH4, H2O, CO2 (C3H8), CO, and C2H6 were main gaseous products released during pyrolysis. Within the pyrolysis processes, it was found that CO2 can be used on the large scale for production of CO-rich syngas. [ABSTRACT FROM AUTHOR]

Highlights • Perspective biofuel for replacement of low energy lignites with HHV = 15.86 MJ kg−1. • Pyrolytic products were stimulated by decomposition of cellulose and lignin fractions. • Catalytic activities of mineral content and influencing the devolatilization kinetics. • The great abundance of PAH compounds was identified from carbonized material. • Promoted graphitization of bio-char where Al acts as a pulsar in acceleration process. Abstract This paper describes the pyrolysis of Poplar fluff (from Populus alba) using on-line apparatus, and carbonization process at 850 °C using the fixed bed reactor. Characteristics of pyrolysis products were examined. Elemental and chemical analyses were shown that Poplar fluff has higher energy content characterized by increased content of fibrous structure (particularly cellulose). Independent parallel reactions model very well describes devolatilization process. It was found that increased amount of extractives can significantly affect on increased release of light gaseous products, but declining hydrocarbons, mostly the alkanes. Liquid product is mainly composed of phenolics, aldehydes, acids, esters and ketones. The carbonization process produces the great abundance of polycyclic aromatic hydrocarbons (PAH's), where naphthalene is the most abundant. Mechanism for PAH's formation was suggested. This study represents the first step in a much wider and more comprehensive way in thermal conversion processes of this type of fuel. [ABSTRACT FROM AUTHOR]

Graphical abstract 2-Hydroxyethylammonium Formate Highlights • Electrical conductivity is significantly higher for 2-hydroxyethylammonium formate. • Geometrical design of anions is responsible for dielectric properties of studied PILs. • Decrease in water content influences on lowering T onset independently on heating rate. • Strong interaction between HN hydrogen atoms in cation and oxygen atoms in the anion. • Very pronounced steric hindrance of cation-anion interactions considering [2-HEAB]. Abstract Dielectric relaxation spectra of three representatives of the class of hydroxyethylammonium carboxylate protic ionic liquids (PILs), namely 2-hydroxyethylammonium formate [2-HEAF], 2-hydroxyethylammonium propionate [2-HEAP] and 2-hydroxyethylammonium butanoate [2-HEAB], were recorded over a wide frequency range (0.05 ≤ ν (GHz) ≤ 50) at 25 °C. The thermal decomposition kinetics of these ionic liquids derived from organic acids was studied by thermogravimetry (TG) using nonisothermal experiments. For the purpose of kinetic analysis, the thermal behavior of the samples was studied in the temperature interval from ambient temperature up to 420 °C at different heating rates (5, 10, 15 and 20 °C min−1). Isoconversional kinetic analysis was performed using Friedman's (FR) differential method and the integral Kissinger–Akahira–Sunose (KAS) method. The dependence of the apparent activation energy (E) on the conversion fraction (α) for the investigated decomposition processes was analyzed. It was found that the molecular structure of the involved anion significantly influences the dielectric properties of the studied PILs. It was also established that a change in the anion structure drastically affects the shape of the thermo-analytical curves. Among the considered PILs [2-HEAF] has the highest thermal stability. However, considering kinetic properties, certain deviations were observed and referred to hydrogen bonding development and steric impediment effects. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pyrolysis of five different biomasses was studied by STA-MS in dynamic conditions. • Effects of biomass species and heating rates on pyrolysis behaviors were evaluated. • Gaseous products and bio-char yields were analyzed. • Kinetic parameters are derived from substantial properties of pyrolysis rate curves. • Biomass structure plays an important role in pseudo-components decomposition. Abstract Slow pyrolysis characterization and kinetic modeling study of five different biomasses (corn brakes (CB), wheat straw (WS), hazelnut shell (HS), sawdust (Beech), and sawdust chemically treated (SDCT)) were performed in this work, using STA-MS techniques. Thermal decomposition of these samples was divided into three stages corresponding to removal of water, devolatilization, and formation of bio-char. Mass spectrometry (MS) showed that H 2 , CH 4 , H 2 O, CO 2 (C 3 H 8), CO, and C 2 H 6 were the main gaseous products released during the pyrolysis of biomasses. It was found that H 2 O, CO and CO 2 evolutions for all biomass samples arise from lignin source in biomass, followed by the cellulose, and hemicelluloses. It was established that the pseudo-component fraction estimated by the theoretical calculations is dependent on the heating rate. Using Gaussian multi-peak fitting and peak-to-peak approaches, regardless of the type of biomass, it was found that decomposition of lignin occurs independently of decomposition of remaining two pseudo-components and that there is no interaction between them. Namely, it was assumed that during pyrolysis process of biomasses, carbohydrate (hemicelluloses + cellulose)—lignin chemical structures most likely exist, where the variety of lignin structure units in different types of biomass affects on the level of energy required for its decomposition. [ABSTRACT FROM AUTHOR]

The pyrolysis process of various types of biomass (agricultural and wood by-products) in non-isothermal conditions using simultaneous thermal analyses (STA) was investigated. Devolatilization kinetics was implemented through combined application of model-free methods and DAEM (distributed activation energy model) using Gaussian distribution functions of activation energies. Results obtained were used in the curve prediction of the rate of mass loss against temperature at various heating rates by numerical optimization. The possible calculation of biomass samples behavior under pyrolytic conditions as the summation of their pseudo-components, hemicelluloses, cellulose, and lignin is also explored. The differences between experimental and calculated data are less than 3.20% offering a quality test of applicability of proposed model on the kinetic studies of a wide range of biomass samples. It seems that the most physically realistic model is the decomposition of biomass in three reactions, depending on the composition of the biomass regarding hemicelluloses, cellulose, and lignin. Kinetic model applied here may serve as a starting point to build more complex models capable of describing the thermal behavior of plant materials during thermochemical processing. [ABSTRACT FROM AUTHOR]

Proposed approach enables a reliable determination of kinetic and thermodynamic behaviors for thermal degradation of polymers. As a model polymer, poly(ethylene oxide) with average molecular weight Mv ~ 100.000 (PEO100) was used. Two-component continuous distribution kinetics best describes PEO100 thermal degradation, involving two main reactions with different values of reaction orders. Procedure enables the check of existence of true or real enthalpy-entropy compensation (EEC). It was established that in the case of random scission reaction step, the artificial EEC emerges. For second reaction step which involves β-scission reaction step (“slow” step), true (real) EEC emerges. It was found that this reaction step is responsible for occurrence of successive micro-phase transitions. These transitions are associated with significant reduction of PEO100 crystallinity through a hinder effect on polymer chains. It was concluded that these transitions are cyclic and reversible, related to the change of mechanical properties of the polymer. [ABSTRACT FROM AUTHOR]

Combustion characteristics (reactivity and reactivity evaluation, ignition index ( D i ), burn-out index ( D f ), combustion performance index ( S ) and combustion stability index ( R W )) and thermo-oxidative degradation kinetics of plane tree seeds (PTS) were investigated. Oxidation analysis shows that PTS exhibits stable and high combustion activity, where comparison of ignition and burn-out index values showed that a more developed pore structures of PTS particles exist, and higher volatile matter content is present. Results are also confirmed through derived experience constant value ( ζ ) and which were compared with other energy sources. It was established that different maximal reaction rate values at various heating rates point out the PTS complex nature, which is stimulated with carbon oxidation reactions and volatile matter release. Kinetic analysis has shown that process can be divided into two stages: devolatilization stage (280–380 °C) and char combustion stage (380–600 °C). In order to obtain a stable solid product, rich in carbon, the PTS shows good performance but with application of high-temperature processing conditions. [ABSTRACT FROM AUTHOR]

Raw and pyrolyzed samples of the plane tree seeds (PTS) were tested by various advanced analytical techniques including simultaneous TG-DSC technique, FTIR analysis, X-ray diffraction (XRD) analysis, Raman spectroscopy analysis, GC-MS (gas chromatography-mass spectrometry) analysis and scanning electron microscope analysis, for its characterization procedure and the pre-treatments in possible application in CCS. Nondestructive analytical method (XRD) showed that raw material is typical for carbon-rich material, where was identified increase in interlayer spacing within graphite structure. The XRD results of pyrolyzed sample at 850 °C showed a sudden loss in interlayer spacing. Spectroscopic analyses of pyrolyzed sample demonstrated the presence of typical aromatic structures found in amorphous carbon. Results indicate the high levels of the growth in basal planes of graphite structure in pyrolyzed sample. It was established that integrated reaction model parameters for pyrolysis of untreated PTS sample realistically describe active temperature period required for charcoal forming, under non-isothermal conditions. It was found that mechanical treatment of material results in increase in the number of chemical compounds. Micrograph showed the presence of variety of shapes and structures, where after pyrolysis, some dissipated pores were detected. One of these pores was partially blocked in some places, depending on the size of surface area. The results showed that the resulting char has very good features for further activation process, while the PTS would represent a good candidate in its application in the CCS. [ABSTRACT FROM AUTHOR]

Kaolins are used in a multiplicity of industries because of unique physical and chemical properties. Relationships between thermal and radioactivity properties are discussed in its application as a building material. Super-fine kaolin powder with particle sizes about 30 μm was analyzed. Simultaneous TGA/DTA analysis was performed on powder samples at various heating rates in an argon atmosphere. Based on investigated thermal properties, it was concluded that dehydroxylation process can vary depending on the characteristics of starting material. The maximum degree of the dehydroxylation (DT) was obtained at the lowest rate of heating (DT = 60.79% for 10 °C min−1). With an increase in the heating rate, decline in DT value was observed. Based on comprehensive testing, it was identified that the degree of dehydroxylation does not drop below 50%. It was concluded that appointed experimental conditions seem sufficient admissible for obtaining degree of dehydroxylation (DT) higher than 50%. In order to safe use of kaolin as a building material from the standpoint of radiological safety, content of natural radionuclides was determined by gamma spectrometry. [ABSTRACT FROM AUTHOR]

This work provides insight into possibilities of maximum utilization of C3-C4 energy crops for thermo-chemical conversion (slow pyrolysis) into high value biochemicals, platform chemicals, drop-in fuels and combustible gases, using coupled kinetic and thermodynamic analyses. In order to examine the kinetics of decomposition of lignocellulosic components, model-free and model-based methods faded from thermal analysis data were used. Thermodynamic compensation was used for explicatory of entropy controlled process, where conformational changes and chemical exchange directly affect the type and distribution of obtained pyrolytic products. It was shown that external variable (i.e. the heating rate/temperature) does not change either an entire reaction mechanism (mechanistic nature of MG and AD pyrolyses) or transition state, but it changes activation enthalpy and activation entropy which lead to differences in terms of heat energy consumption, pyrolysis favorability and thus rates of generation of activated complex among feedstocks. To investigate the interplay of catalysts (present in feedstocks as minerals) and reactants, selective energy transfer (SET) model was applied. The model showed an activity of catalyst with different outputs towards two reactants, lignin part of the structure in MG and 1,8-cineole in AD. It was shown that AD is more convenient for thermal conversion than MG, regarding to lower transformation energy requirement, higher reactivity, as well as much faster accumulation of products. [Display omitted] • Enthalpy-entropy compensation is a source of KCE for perennial grasses slow pyrolysis. • Pyrolysis is strongly influenced by disorder level (entropy driven) during conversion. • Pyrolysis favorability is lower for Miscanthus×giganteus -MG than for Arundo donax -AD. • AD has high reactivity accumulating more products (bio-oils and high value chemicals). • Applied selective energy transfer model shows interplay of the catalyst and reactant. [ABSTRACT FROM AUTHOR]

Kinetic and thermodynamic analysis of non-isothermal decomposition of super-fine kaolin powder was examined. It was established that the decomposition process proceeds through liberation of adsorbed water, the loss of the water of hydration and dehydroxylation process, which produces highly disordered metakaolin. By applying the distributed reactivity approaches, it was found that dehydroxylation can be described with simultaneous two-parallel reactions model. By applying the Exner-Linert statistical method on estimated Eyring plots, the true isokinetic temperature was confirmed. The appearance of entropy – enthalpy compensation (EEC) showed the direct cause-and-effect relationship between these thermodynamic observables resulting by physically real factors such as the steric factors. It was shown that the phenomenon of true compensation effect arises from conformational (geometrical) changes, which occur during metakaolin formation. [ABSTRACT FROM AUTHOR]

In this work, the thermal stability, the non‐isothermal cure kinetics and distributed reactivity model (DRM) for fiber reinforced resin matrix composite (T800H/3900‐2 prepreg) have been systematically analyzed using combined phenomenological and partially fundamental approaches. It has been shown that the proposed actual kinetic model (expressed through the three‐parameter Šesták‐Berggren (SB) model including the diffusion effects) more accurately describes the curing process than the idealized kinetic model (which includes only the autocatalytic reaction). Presence of diffusion phenomena that occur at elevated temperatures and higher values of the extent of cures were demonstrated and explained in detail, through the use of modified Williams–Landel–Ferry (WLF) equation (based on the glass transition analysis) and the Avrami crystallization theory. The DRM was demonstrated that in autocatalytic stage, the reaction of primary amine with two epoxy groups plays an important role in the overall curing process. It has been shown that condensed phase effects can lower the apparent activation energy (Ea) value of the curing process. The lifetime analysis showed that the studied T800H/3900‐2 prepreg possesses good thermal resistance, which is connected with the process including a ring‐opening addition‐type crosslinking reaction.POLYM. COMPOS., 39:201–220, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Kinetics of degradation for Aronia melanocarpa fresh fruits in argon and air atmospheres were investigated. The investigation was based on probability distributions of apparent activation energy of counterparts ( ε a ). Isoconversional analysis results indicated that the degradation process in an inert atmosphere was governed by decomposition reactions of esterified compounds. Also, based on same kinetics approach, it was assumed that in an air atmosphere, the primary compound in degradation pathways could be anthocyanins, which undergo rapid chemical reactions. A new model of reactivity demonstrated that, under inert atmospheres, expectation values for ε a occured at levels of statistical probability. These values corresponded to decomposition processes in which polyphenolic compounds might be involved. ε a values obeyed laws of binomial distribution. It was established that, for thermo-oxidative degradation, Poisson distribution represented a very successful approximation for ε a values where there was additional mechanistic complexity and the binomial distribution was no longer valid. [ABSTRACT FROM AUTHOR]

[Display omitted] • ● Thermal properties of MgCl 2 ·6H 2 O–[Ch]Cl deep eutectic solvent (DES) were investigated. • ● Multiple step DES decomposition kinetics is characterized by dehydration (charging) • ● Effect of dehydration compensatory lowers the system pressure towards MgO forming. • ● H O H•••Cl hydrogen bonds serve as energy donating system for process continuation. • ● Diffusion (D2) mechanism is guided by concentration gradient inside oxide (MgO) shell. In recent years, deep eutectic solvents (DESs) have attracted considerable attention, and they have been applied in many fields, such as dissolution and separation, electrochemistry, materials preparation, reaction, and catalysis. In this paper, a detailed thermal decomposition mechanism of DES-type II (consisting choline chloride (ChCl) and magnesium chloride hexahydrate (MgCl 2 ·6H 2 O) in a molar ratio 2:1 (MgCl 2 ·6H 2 O-[Ch]Cl)) was explained, using thermal analysis techniques. Physicochemical clarification of overall thermal decomposition mechanism and the influence of enthalpy–entropy compensation (EEC) on reactions mechanism emerging are presented for the first time, in favor of this DES type. In the kinetic analysis of the decomposition process, two approaches were used: model-free (inverse) and model-based (direct) methods. It was found that thermodynamic principles in the form of EEC are the source of kinetic compensation effect (KCE) during MgCl 2 ·6H 2 O-[Ch]Cl thermal decomposition, as a consequence of the effects of molecular interactions. Key phenomenon in the complex multiple step process represents a parallel dehydration steps of MgCl 2 ·6H 2 O in DES, leading to formation of intermediates, such as [MgCl 1 (H 2 O) 5 ]1+ and [MgCl 2 (H 2 O) 4 ]. It was established that formation of final products (Mg(OH) 2 and MgOHCl) requires a higher expenditure of energy to overcome a high potential barrier, where reaction system compensates this energy via hydrogen bonding disruption. This was confirmed by the identification of a specific 'oscillator', flagged as H O H···Cl hydrogen bond donating system of the energy ("heat bath"). All kinetic parameters and mechanisms of individual reaction steps were confirmed by numerical optimization of the process and modulated dynamic predictions. [ABSTRACT FROM AUTHOR]

• Miscanthus giganteus and Arundo donax are characterized by high volatilization. • Difference between reaction temperatures is affected by composition of energy crops. • Arundo donax has higher exergy efficiency of syngas based on CH 4 production. • Arundo donax has the lower biomass chemical exergy compared to Miscanthus giganteus. • The lower equivalance ratio produces higher exergy efficiency of the gasification. The actual paper analyses the performance of different energy crop biomasses, Miscanthus x giganteus Greef et Deu (EC-1) and Arundo donax L. (EC-2) stems, during slow pyrolysis process monitored by simultaneous TG-DTG-MS techniques, through chemical exergy analysis. In addition to considering the physical and chemical characteristics of given feedstocks for their efficient thermo-chemical conversion into pyrolytic gas, in this study, a theoretical simulation for their implementation use in the gasification process was also performed. The performed thermodynamic study with detailed exergy analysis showed that the large contribution of exergy in syngas components such as CO and H 2 originates primarily from cellulose pyrolysis of EC-1, while large exergy contribution in syngas component as CH 4 originates from lignin pyrolysis of EC-2. It was founded that the exergy efficiency of syngas for EC-1 equals 19.04%, which is lower than the exergy efficiency of syngas for EC-2 (20.46%), as a result of higher ash content in EC-1. Also, it was reported that higher carbon (C) and hydrogen (H) contents present in the EC-2 sample generate higher gaseous energy and exergy values, i.e. the increment of exergy efficiency of syngas, by both approaches (pyrolysis and gasification exergy analysis), but results in a lower biomass chemical exergy (18.28 MJ kg−1). The methodology applied to the gasification process was shown a higher exergy efficiency for EC-2 (∼36 – 42%) than for EC-1 (∼33 – 39%), dependant on the equivalence ratio (ER). [Display omitted] [ABSTRACT FROM AUTHOR]

Proposed distributed reactivity model of dehydration for seedling parts of two various maize hybrids (ZP434, ZP704) was established. Dehydration stresses were induced thermally, which is also accompanied by response of hybrids to heat stress. It was found that an increased value of activation energy counterparts within radicle dehydration of ZP434, with a high concentration of 24-epibrassinolide (24-EBL) at elevated operating temperatures, probably causes activation of diffusion mechanisms in cutin network and may increases likelihood of formation of free volumes, large enough to accommodate diffusing molecule. Many small random effects were detected and can be correlated with micro-disturbing in a space filled with water caused by thermal gradients, increasing capillary phenomena, and which can induce thermo-capillary migration. The influence of seedling content of various sugars and minerals on dehydration was also examined. Estimated distributed reactivity models indicate a dependence of reactivity on structural arrangements, due to present interactions between water molecules and chemical species within the plant. [ABSTRACT FROM AUTHOR]

In this work, plane tree seed-based activated carbons (AC) were used for possible application in carbon dioxide capture and storage (CCS) technology. After carbonization process at 850 °C, resulting preliminary AC’s were activated at various temperatures. The high levels of the growth in basal planes of graphite structure in carbonized sample were detected. Also, it was found that the samples activated at 750 and 850 °C have a lower graphitization degree and contained substantially disordered sections and defects, which are characteristic of typical amorphous porous carbons. Process modeling has shown that the CO 2 sorption can be described by multi-parametric continuous distributed reactivity model. Analysis showed the occurrence of gas reduction process, involving gibberellic acid and coenzymes which can produce the methane gas. The highly ordered arrangement of the gas molecules on the carbons was assumed. [ABSTRACT FROM AUTHOR]

• Development of the small wood pellet stove with thermal power below 10 kW. • Satisfactory agreement between model results and experimental tests was achieved. • High CO emission leads to reduction of acquired thermal power and stove efficiency. • Maintaining a high temperature is crucial for completion of CO and CO 2 oxidations. • New method for frequency factor calculation of main homogeneous combustion reaction. With the increased popularity of using wood stoves for household heating in recent years, numerous experimental research projects have been launched with the goal of generating cleaner and more efficient stove designs. This work is focused on mathematical modeling of combustion process in low-power residential heating appliance (small-scale stove) fuelled by different wood pellets (WP1-Beech (hardwood) and WP2-Pine (softwood)). Kinetic model scheme that encompasses determination of Arrhenius parameters was proposed for applied Finite rate/Eddy Dissipation approach. Types of wood pellets have been combusted on the experimental stand which is equipped with a set of temperature sensors and exhaust analyzer. A comparison of results obtained from combustion in the heating unit has been performed to find relations between established kinetics of devolatilization for various wood pellets and to determine exhaust composition, arising from oxidation reactions. Numerical modeling using computational fluid dynamics (CFD) has been performed for the char and CO oxidations to supplement the experimental results. Due to limitations on installed stove such as poor design, air supply, fume extraction, or heat exchanger can lead to excessive CO emissions or lower energy efficiency. Outcomes show that it is crucial to minimize unused stove volume and to enhance gaseous mixing for reduction of CO emissions, while maintaining sufficiently high temperatures for supporting fast oxidation reactions. Results of comparisons of conducted analyses can be useful in areas related to process optimization and improvement of combustion and devolatilization reaction conditions in the small scale heating units. [ABSTRACT FROM AUTHOR]

The on-line dynamic pyrolysis kinetics of swine manure solid samples was investigated in this paper. It has been found that the model which includes combined Friedman's isoconversional and multi-distributed reactivity approaches can best describe the pyrolysis process. Pyrolysis kinetics of swine manure samples proceeds through two major pyrolysis zones, where in first zone exists the kinetically complex reactions related to decompositions of hemicelluloses and fat/proteins, as well as decomposition reactions related to degradation of cellulose and lignin structures. Second zone includes the reactions attached to follow-up devolatilization and carbonization processes. It was found that identified high reaction orders represent the measure of complexity and multiplicity of the mechanism. It has been found that the change in reaction order ( n) values is the result of reactions that are taking place due to the instability of products, or the secondary reactions, change in apparent activation energy, and effect of varying of the pre-exponential factor values. [ABSTRACT FROM AUTHOR]

A series of silica-supported nickel catalyst precursors was synthesized with different SiO2/Ni molar ratios. Reduction of Ni catalyst precursors with different SiO2/Ni molar ratios under a hydrogen atmosphere was investigated at different heating rates. Kinetic parameters were determined using Kissinger–Akahira–Sunose isoconversional and invariant kinetic parameter methods. It was found that for all molar ratios, the apparent activation energy (Ea) is practically constant in the conversion range of 0.20 ≤ α ≤ 0.80. In the considered conversion range, following values ofEawere found: 134.5 kJ mol−1(SiO2/Ni = 0.20), 139.6 kJ mol−1(SiO2/Ni = 0.80), and 128.3 kJ mol−1(SiO2/Ni = 1.15). It was established that the reduction of Ni catalyst precursors with different SiO2/Ni molar ratios is a complex process and can be described by the Šesták–Berggren autocatalytic model. It was found that the reaction is more Langmuir–Hinshelwood type, as hydrogen dissociates rapidly on surface nuclei and the dissociated hydrogen reacts with the Ni–O active system. It was concluded that the reduction process proceeds through bulk nucleation, which is a dominant mechanism, where three-dimensional growth of crystals with polyhedron-like morphology exists. It was found that the Ni/Si ratio decreases after the reduction process. This has been explained by low Ni and higher Si surface concentrations. It has been disclosed that Ni dispersion decreases. [ABSTRACT FROM PUBLISHER]

Isoconversional analysis and accurate determination of lifetime properties for thermal and thermo-oxidative degradation processes of Aronia melanocarpa were examined. The Šesták–Berggren (SB) autocatalytic model was found as best model to describe degradation process of A. melanocarpa in inert atmosphere. It has been found that autocatalysis may occur from inevitable presence of water probably through the hydrolysis. In the case of thermo-oxidative degradation, it was found that main mechanistic scheme can be presented with two different forms of reaction mechanism function, such as n th-order reaction model (with n > 1) and SB autocatalytic model. It was determined that neochlorogenic acid represents main compound, which has a strong hydrogen-donating activity. Based on lifetime analysis, it was found that in oxidative conditions, A. melanocarpa shows greater resistance to temperature variations, which correspond to storage conditions and where degradation mechanism greatly affects stability and physico-chemical characteristics of its constituents. Industrial relevance Current research has a direct industrial application during the testing of “responses” of black chokeberry— A. melanocarpa fresh samples on the various thermal stresses in the inert and oxidative reaction conditions. Knowledge of the exact mechanism of degradation (referring to precisely defined reaction pathways) of A. melanocarpa in different reaction atmospheres enables us the targeting an exactly isolated chemical compounds in A. melanocarpa fresh samples, which are responsible for antioxidant protection of human tissue and plasma. The results presented in this paper can be guidelines for the application of industrial processes for precise allocations of these compounds and their further testing for the treatment of malignant diseases. The importance of this research also comes down to the fact that 25% of total polyphenols in chokeberry fruits are anthocyanins, which represent the powerful antioxidants in vitro. Also, the current work provides a specific approach in accurate determination of lifetime properties of A. melanocarpa samples, which is very important in terms of checking the behavior of tested fruit berry system on the temperature variations during storage periods. [ABSTRACT FROM AUTHOR]

Crystallization process of Gd 2 Ti 2 O 7 precursor's powder prepared by Pechini-type polymerized complex route has been studied under isothermal experimental conditions in an air atmosphere. It was found that the crystallization proceeds through two-parameter Šesták–Berggren (SB) autocatalytic model, in the operating temperature range of 550 °C≤ T ≤750 °C. Based on the behavior of SB parameters ( M , N ), it was found that in the lower operating temperature range, the crystallites with relatively low compactness exist, which probably disclosed low dimensionality of crystal growth from numerous nucleation sites, where the amorphous solid is produced. In the higher operating temperature region (above 750 °C), it was established that a morphological well-defined and high-dimensional particles of the formed pyrochlore phase can be expected. It was found that at T =850 °C, there is a change in the rate-determining reaction step, from autocatalytic into the contracting volume mechanism. [ABSTRACT FROM AUTHOR]

In the present study, the pyrolysis process under dynamic conditions of swine manure solids collected from rearing farm was investigated. Tested type of biomass feedstock was analyzed from the point of view of technological exploitation in order to obtain the highest possible quality and yields of bio-oil and bio-char. Furthermore, char gasification process was also examined. It was found that pyrolysis process can be described by parallel independent two-portion process model (PI-TPPM), which includes two processing state of the system (marked by processes # 1 and # 2), where process # 1 can be attributed to decomposition processes of hemicelluloses and fats/proteins, while process # 2 corresponds to pyrolyses of cellulose and lignin. Also, it was found that liquid and gas yields increase with an increase in heating rate, while approximately 40% of heavy oil yield is achieved by proposed experimental setup, which have been attained the satisfactory results for a good support in industrial extraction procedures. It was found that results associated with the presence of high reactivity at highest heating rate can be attributed to the highly porous structures formed, as we approach to the fast pyrolysis conditions. [ABSTRACT FROM AUTHOR]

Pyrolysis of pine and beech wood was investigated by isothermal thermogravimetry at five different temperatures (280, 290, 300, 310, and 320 °C) in an atmosphere of flowing nitrogen. It was found that isothermal pyrolysis of pine and beech can be described by three-dimensional diffusion mechanisms with different reaction geometry (Jander type for pine and Ginstling-Brounstein type for beech). It was established that, for both systems, values of the apparent activation energy ( E) calculated in an extrapolated temperature range coincide with values calculated by use of the classical Arrhenius equation. It was found that different values of the kinetic data and diffusion geometry of the volatile products probably result from slight changes of the structure and chemical composition of the wood which occur during pyrolysis. [ABSTRACT FROM AUTHOR]

A series of silica-supported nickel catalyst precursors was synthesized with different SiO/Ni mole ratios (0.20, 0.80 and 1.15). Non-isothermal reduction of Ni catalyst precursors was investigated by temperature-programmed reduction at four different heating rates (2, 5, 10 and 20 °C min), in a hydrogen atmosphere. Kinetic parameters ( E, A) were determined using Friedman isoconversional method. It was found that for all mole ratios, apparent activation energy is practically constant in conversion range of α = 30-70 %. In considered conversion range, the following values of apparent activation energy were found: E = 129.5 kJ mol (SiO/Ni = 0.20), E = 133.8 kJ mol (SiO/Ni = 0.80) and E = 125.0 kJ mol (SiO/Ni = 1.15). Using two special functions ( y( α) and z( α)), the kinetic model was determined. It was established that reduction of Ni catalyst precursors with different SiO/Ni mole ratios is a complex process and can be described by two-parameter Šesták-Berggren (SB) autocatalytic model. Based on established values of SB parameters for each mole ratio, the possible mechanism was discussed. It was found that for all investigated ratios, the Weibull distribution function fits very well the experimental data, in the wide range of conversions ( α = 5-95 %). Based on obtained values of Weibull shape parameter ( θ), it was found that experimentally evaluated density distribution functions of the apparent activation energies can be approximated by the unbalanced peaked normal distribution. [ABSTRACT FROM AUTHOR]

Pyrolysis process of coffee paper cup samples was investigated in a flow stream of nitrogen at different heating rates (10, 20, 30 and 40°Cmin−1), using thermo-analytical techniques. It was found that second pyrolysis stage can be described by Šesták-Berggren (SB) autocatalytic model, with mechanism function f(α)=α0.011(1−α)1.459. Based on analysis of SB kinetic exponents (designated by M and N), it was found that second pyrolysis stage is mainly controlled by chemical process, involving reactions with reaction-order (n) higher than unity. Applying specific statistical analysis, in order to obtain precise distribution of reactivity, the discrete (binomial) distribution has shown that there are two important areas of current distribution for corresponding energy outcomes, within the apparent activation energy as random variable. The first "concentration" area of energy outcomes corresponds to start of chain end depolymerization reaction forming levoglucosan at high enough temperature region, while second "concentration" area of energy outcomes includes occurrence of macro-radicals in liquid phase propagate with radical addition on unsaturated C-C bonds, with cross-linking and formation of small chemical species. It was found that further elevating of temperature (above 340°C), will leads to fact that rate of tar-forming reactions increases and formation of char decreases. [ABSTRACT FROM AUTHOR]

The non-isothermal decomposition process of commercial silver nitrate used as the precursor for the USP procedure was investigated by simultaneous TGA--DTA measurements at different heating rates, in an argon atmosphere. Detailed kinetic and thermodynamic analyses, with special emphasis on the formation of a complete mechanistic scheme of the process were performed. It was found that the process under study can be described by the acceleratory power law kinetic model (P2), in the range of the extent of conversion (α) values (0.15 ≤ α ≤ 0.85), where the value of the apparent activation energy (Ea) can be considered as the constant (141.3 kJ mol-1). The kinetic prediction analysis was shown that only the power law kinetic model (f(α) = 2α1/2) gives the value of Ea which is consistent with the value obtained from the isothermal conditions. The critical temperature (Tc) of decomposition process was determined. The resulting value of Tc was in fairly good agreement with the starting temperature of thermal decomposition of silver oxide (Ag2O). The thermodynamic functions of decomposition process are calculated by the activated complex theory and showed that the silver--oxygen bond secession can be interpreted as a "slow" stage of the decomposition process. [ABSTRACT FROM AUTHOR]

Thermal decomposition of zinc leach residue has been studied in a tubular furnace under a constant nitrogen gas flowing, at four different operating temperatures (600°C, 750°C, 950°C, and 1150°C). Using a detailed kinetic analysis, it was shown that the investigated process can be described by a two-parameter autocatalytic Šesták–Berggren reaction model. It was noted that the apparent activation energy values Eaincrease progressively with a degree of conversion, accompanied by the appearance of a convex Arrhenius dependence. This behavior is a characteristic of a system of parallel competing reactions. It was concluded that the investigated isothermal decomposition process is characterized by unusually very low preexponential factor and low values of the apparent activation energy. Based on the derived density distribution function of Eavalues, it was concluded that the isothermal decomposition process probably occurs through four reaction steps, where each step is characterized by one parallel reaction. [ABSTRACT FROM PUBLISHER]

The stochastic geometric model was applied to kinetic modeling the complex process of thermal decomposition of zinc ferrite from neutral leach residues, at different operating temperatures (600°C, 750°C, 950°C and 1150°C). Based on functional dependence of Avrami׳s constant (n) in a function of the effective activation energy (E a ), it was found that at T>950°C, the crystallization process takes place in autocatalytic stage, under the conditions where the rate of nucleation rapidly increases. It was established that the high nucleation rate can be attributed to formation of both Zn and Fe rich regions which provide a high number of heterogeneous nucleation sites. Based on the obtained final shape of the particles, it was found a strong presence of zinc, iron (present only in the form of Fe3O4 (magnetite)), magnesium (in the form of Mg2Si2O6), and also lead oxides. Thermodynamic analysis showed that the decomposition depends on the introduction of heat, and exerts a positive value of the Gibbs free energy of activation. Such a feature was expected since the ferrite system has been submitted to a forced decomposition and volatilization reactions. [ABSTRACT FROM AUTHOR]

The kinetic study of the crystallization process of the α-Fe phase from the amorphous Fe81B13Si4C2 alloy was investigated by DSC and XRD techniques. The kinetic parameters (InA, Ea of the investigated process were determined using the Kissinger and isoconversional (model-free) methods. It was established that the α-Fe crystallization process can be described by the JMA (Johnson-Mehl-Avrami) kinetic equation. In accordance with the XRD analysis and the calculated crystallization parameters (n = 4; m = 3), it was concluded that the crystallization stages of the considered process can be described by the bulk nucleation and the three-dimensional (3D) growth of nuclei. [ABSTRACT FROM AUTHOR]