Non-parametric Kinetics Research Articles

Determination of the Kinetic Parameters of Thermal Degradation and Hydrodemetallization of a Mixture of the Heavy Fraction of Low-Temperature Coal Tar and Coal Shale

The laws of thermal degradation of the mixture of the heavy fraction of low-temperature coal tar and coal shale were investigated using dynamic thermogravimetry. The kinetic characteristics of the process were determined using various methods, including the Ozawa–Flynn-Wall, Friedman, non-parametric kinetics and Šesták–Berggren methods. It is shown that coal shale initiated changes in the kinetic parameters and decomposition rate of the heavy fraction of coal tar. It was found that a 13% content of coal shale in the mixture led to the maximum rate of weight loss of the heavy fraction of coal tar. A hydrodemetallization kinetic model of the mixture of the heavy fraction of low-temperature coal tar and coal shale is proposed. The kinetic parameters of the hydrodemetallization process were determined; in addition, the rate constants at various temperatures were estimated. The study shows that the distribution of trace elements in the hydrogenate from the initial mixture and in the hydrogenate from the solid residue was characterized by relatively low values of reaction rate constants. The maximum microelement distribution rate was achieved in the hydrogenate solid residue. Energy indicators of activation processes indicated that hydrodemetallization at low temperatures is advantageous from an energy point of view.

Application of the NPK Method in the Crystallization Kinetics of High-Density Polyethylene

The Non-Parametric Kinetics (NPK) method, developed in 1998, by Serra, R., Sempere, J. and Nomen, R. has been used by them and other research groups to analyze the thermal behavior of a physical or chemical transformation and thermal stability. However, it was until 2021 that the method was applied for the first time in a cooling process for the determination of the crystallization kinetics of polypropylene, obtaining satisfactory results.
 The advantage of the NPK method is that it does not assume any model for the temperature function, nor for the conversion function to describe the crystallization kinetics. Through a mathematical process, the method provides two vectors: the vector u, which contains the information about the kinetic model, and the vector v, which contains the information about the temperature function.
 The aim of this work is to verify that the NPK method is applicable to the crystallization of high-density polyethylene by comparing the results with the most commonly used models to describe the crystallization kinetics of polymers. The fits obtained were very good and the vector u and v allow us to reproduce the original curves from DSC.

Comparative analysis of the thermal decomposition kinetics of β-cyclodextrin inclusion complexes with anabasine at different heating rates

The results of analysis of the thermal decomposition kinetics of inclusion complexes of β-cyclodextrin with the alkaloid anabasine at different heating rates are presented. The kinetic characteristics of the processes are determined based on the Friedman, Flynn–Wall–Ozawa and nonparametric kinetics methods.

Combined In Silico and Experimental Investigations of Resveratrol Encapsulation by Beta-Cyclodextrin.

The results of the computational and the physicochemical studies of the encapsulation of resveratrol with β-cyclodextrin are presented here. At first, the molecular docking experiments predicted good binding. Several MD simulations and MM-PBSA experiments confirmed the reliable binding, showing optimal kinetics and energy. As an application, resveratrol inclusion complexes with β-cyclodextrin were obtained in an aqueous alcohol medium via microwave treatment. The results of thermographic measurements of the obtained clathrates using a differential scanning calorimeter are presented, and the obtained activation energy was calculated using the Ozawa–Flynn–Wall and Friedman methods, as well as nonparametric kinetics. The effect of complexation on the kinetic parameters of thermal destruction of the β-cyclodextrin–resveratrol inclusion complex was considered. The morphology of the surface of the obtained clathrate complexes was described using a scanning electron microscope. The spectral properties of the inclusion complex were characterized by FT-IR, 1H, and 13С NMR spectroscopic data. The obtained in silico, morphological, thermogravimetric, and spectral results confirmed the formation of the resveratrol–β-cyclodextrin complex. The antioxidant activities of the inclusion complex were determined to be 12.1 μg/mL, compared to 14.3 μg/mL for free resveratrol, indicating an improvement in the bioactivity.

Solid-state stability and kinetic study of three glucocorticoid hormones: prednisolone, prednisone and cortisone

In the class of steroid hormones, glucocorticoids are belonging to the subclass of corticosteroids, consisting of numerous synthetic or naturally occurring compounds, widely used in medical practice either as replacement therapy in glucocorticoid deficiency or to suppress the immune system. Glucocorticoids are active pharmaceutical ingredients used in solid, semisolid or liquid formulations involved mainly in the treatment of different types of cancers, inflammatory and autoimmune disorders, but as well as allergies. Both thermal stability and heterogeneous degradation kinetics of prednisolone, prednisone and cortisone were investigated in dynamic inert atmosphere (dinitrogen), at five heating rates β = 7, 10, 12, 15 and 20 °C min−1 using isoconversional methods of Friedman, Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa, and later the modified non-parametric kinetic (NPK) method. The variation of apparent activation energies versus conversion degree as revealed by isoconversional methods suggested multistep degradation, which was later confirmed by the NPK method. The NPK method disclosed that all three glucocorticoids are degraded by two parallel processes, with apparent activation energies of 171.7 kJ mol−1 for prednisolone, 78.8 kJ mol−1 for prednisone and 61.8 kJ mol−1 for cortisone, respectively. The results are in good agreement with the ones suggested by isoconversional methods, and a discussion regarding the relation between the structure and apparent activation energy is presented.

Advances in new multicomponent crystal system: structure, thermal kinetic analysis, photoluminescent, and biological activity investigations

Multicomponent organic crystals based on natural metabolites or pharmaceutical active ingredients play an important role in solid state chemistry, agriculture, and pharmaceutical industry. This study reveals the synthesis of a new luminescent alkanolammonium salt of 4-nitrobenzoic acid (MMEA4NB, methylethanolammonium 4-nitrobenzoate), together with the detailed investigation of its structural motifs, thermal stability, decomposition kinetics, and validation of its plant growth regulatory activity. The new compound was obtained at room temperature in excellent yield and shorter reaction time. Thermal stability and decomposition were studied in a dynamic air atmosphere by thermogravimetry—differential thermal analysis—derivative thermogravimetric techniques. The kinetics and mechanism of the thermal decomposition reaction were evaluated under non-isothermal conditions using three different isoconversional methods Flynn–Wall and Ozawa, Friedman, and modified nonparametric kinetics method in order to obtain the activation energy. Proton transfer and hydrogen bonding in the organic salt were elucidated and confirmed by infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure revealed cation–anion heterosynthons and cation–cation homosynthon. The relation between the protonation state of the components, intermolecular interactions, and thermal stability of MMEA4NB is discussed. This study demonstrates the importance of MMEA4NB in the development of new specific luminescent plant growth regulators, possible viewers of localization and distribution in plants.

The multistep decomposition of boric acid

AbstractDue to its high potential for thermal energy storage systems (Huber, Setoodeh Jahromy, Jordan, et al, Energies. 2019;12:17) the decomposition of boric acid is of particular interest in the field of applied research. The complexity of the reaction mechanism, with its multiple partial‐overlapping reaction steps, hitherto prevented a clear identification and analysis of each stoichiometric reaction step. So far, various research teams performed different kinetic analyses of boric acid, which led to various reaction mechanisms and stoichiometric reaction steps with yet inconclusive results for process modeling. Thus, a deeper examination of the process was desirable, to validate whether a proposed reaction is reasonable or not. For this purpose, experimental data were used for a deconvolution of the reaction sequence, using the Fraser‐Suzuki function, which clearly revealed the respective single reactions. The results of the deconvolution were compared with the proposed reaction steps in consideration of the stoichiometric ratio and thereby illustrated that the decomposition of polycrystalline boric acid more likely consists of three reaction steps. In contrary to the two‐step mechanism, the three‐step mechanism showed a very good correlation (r > 99%). Based on these outcomes, kinetic analyses were performed for each reaction step, by means of the nonparametric kinetics 2 (NPK2) method with subsequent determination of kinetic parameters. Additionally, for a deeper insight into the reaction, analyzing techniques like X‐ray diffraction (XRD), scanning electron microscopy (SEM) and simultaneous thermal analysis (STA) were applied.

Solid State Stability and Kinetics of Degradation for Candesartan-Pure Compound and Pharmaceutical Formulation.

The aim of this work was to assess the impact of an excipient in a pharmaceutical formulation containing candesartan cilexetil over the decomposition of the active pharmaceutical ingredient and to comparatively investigate the kinetics of degradation during thermolysis in an oxidative atmosphere under controlled thermal stress. To achieve this, the samples were chosen as follows: pure candesartan cilexetil and a commercial tablet of 32 mg strength. As a first investigational tool, Universal attenuated total reflection Fourier transform infrared (UATR-FTIR) spectroscopy was chosen in order to confirm the purity and identity of the samples, as well as to check if any interactions took place in the tablet between candesartan cilexetil and excipients under ambient conditions. Later on, samples were investigated by thermal analysis, and the elucidation of the decomposition mechanism was achieved solely after performing an in-depth kinetic study, namely the use of the modified non-parametric kinetics (NPK) method, since other kinetic methods (American Society for Testing and Materials—ASTM E698, Friedman and Flynn–Wall–Ozawa) led to inadvertencies. The NPK method suggested that candesartan cilexetil and the tablet were degraded by the contribution of two steps, the main being represented by chemical degradation and the secondary being a physical transformation. The excipients chosen in the formulation seemed to have a stabilizing effect on the decomposition of the candesartan cilexetil that was incorporated into the tablet, relative to pure active pharmaceutical ingredient (API), since the apparent activation energy for the decomposition of the tablet was 192.5 kJ/mol, in comparison to 154.5 kJ/mol for the pure API.

Impact of Partial Pressure, Conversion, and Temperature on the Oxidation Reaction Kinetics of Cu2O to CuO in Thermochemical Energy Storage

Metal oxides are promising potential candidates for thermochemical energy storage in concentrated solar power plants. In particular, the Cu2O/CuO system is suitable because of its high energy density, applied temperature interval, and reduced cost compared to the CoO/Co3O4 system. In heterogenous gas-solid reactions, the pressure affects the kinetics significantly. To quantify this effect for oxidation of Cu2O to CuO, isothermal runs between 800 °C and 930 °C at different oxygen partial pressures (0.1, 0.2, 0.5, and 1.0 bar) were conducted with thermogravimetric analysis (TGA). Defined fractions of CuO samples (1–100 µm) were analyzed with X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and scanning electron microscopy (SEM) analysis. The kinetic analyses were performed with extended non-parametric kinetics (NPK), which is applied for the first time to consider the pressure term in the general kinetic equation in addition to the conversion and the temperature term. The results show how the oxygen partial pressure impacts the kinetics and how reparameterization of the pressure term affects the kinetic analysis of the oxidation reaction of Cu2O to CuO. The best conversion model is a two-dimensional Avrami-Erofeev model with an activation energy of 233 kJ/mol. The kinetic models for conversion, temperature, and pressure presented in this work provide one of the most important requirements for reactor designs.

NPK 2.0: Introducing tensor decompositions to the kinetic analysis of gas–solid reactions

AbstractA method for deriving kinetic models of gas–solid reactions for reactor and process design is presented. It is based on the nonparametric kinetics (NPK) method and resolves many of its shortcomings by applying tensor rank‐1 approximation methods. With this method, it is possible to derive kinetic models based on the general kinetic equation from any combination of experiments without additional a priori assumptions. The most notable improvements over the original method are that it is computationally much simpler and that it is not limited to two variables. Two algorithms for computing the rank‐1 approximation as well as a tailored initialization method are presented, and their performance is assessed. Formulae for the variance estimation of the solution values are derived to improve the accuracy of the model identification and to provide a tool for diagnosing the quality of the kinetic model. The methods effectiveness and performance are assessed by applying it to a simulated data set. A Matlab implementation is available as Supporting Information.

Relationship of nanostructure and thermo-chemical response/thermal ablation of carbon aerogels

ABSTRACTIn this work, the interfacial mass balance relations combined with the non-parametric kinetic (NPK) analysis results were used for evaluating the thermo-chemical ablation process and oxidation mechanism of carbon aerogels with various porous structure. It was found that the two-parameter model of Nomen–Sempereis was able to describe the kinetics of the oxidation reaction and to reveal the structure-dependent contribution of two main processes with chemical and physical nature. The porosity of the carbon aerogel, rather than the other microstructural features, was realized more effective on the rate of ablation.

Thermal decomposition of tricyclohexylidene triperoxide

The thermal decomposition of tricyclohexylidene triperoxide both pure and in 4% w/w solution of n-dodecane to yield mainly 16-hexadecanolide is studied applying the nonparametric kinetics method to a set of scanning calorimetry records. The apparent energies of activation obtained are 148.4 ± 0.8 and 90.9 ± 0.8 kJ mol−1, respectively. Combined kinetic models are proposed (first order + Sestak–Berggren) to describe the processes. The isothermal decomposition of the pure peroxide is studied, indicating that there is no appreciable reaction after 12 h at temperatures below 103 °C and that conversion is complete at temperatures over 137 °C.

Study of solid-state degradation of prochlorperazine and promethazine

Prochlorperazine (PCP) and promethazine (PMT) are dopamine (D2) receptor antagonists with a phenothiazinic structure that used nowadays mainly for their antiemetic properties, including for the pre- and postoperative setting. In this paper, the thermal behavior of PCP and PMT was studied, including a complete kinetic analysis for the evaluation of the degradation process in heterogenous media. Samples were analyzed using Fourier transform infrared spectroscopy, thermogravimetric analysis (TG/DTG/HF) and a preliminary kinetic analysis using the ASTM E698 kinetic method, the obtained data being later completed with an in-depth kinetic analysis according to ICTAC 2000 protocol, using the isoconversional methods of Friedman, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose, respectively, the modified nonparametric kinetics method, the latter allowing the determination of the kinetic triplet without using any approximation, but as well the separation of parallel reaction that occurs at decomposition. The results confirmed that PCP dimaleate has a better stability in comparison with PMT hydrochloride, in terms of apparent energy of activation, probably due to solid-state structure of solid and the contribution of intermolecular bondings.

Thermal degradation, kinetic analysis and evaluation of biological activity on human melanoma for artemisinin

In this paper, the bioactive compound artemisinin (ART) was evaluated by instrumental techniques, regarding its thermal stability and mechanism of decomposition, but for the biological activity as well, using in vitro techniques, namely the cytotoxic activity evaluation on two cell types (HaCaT and A375) employing the MTT proliferation method, and the antioxidant activity (AOA) using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The results of the isoconversional kinetic study first lead to an indication of complex decomposition mechanism, which was later confirmed by the modified nonparametric kinetics (NPK) method. According to the NPK method, it was shown that ART is mainly degraded by the involvement of two parallel processes, with different energetic contributions that are due to chemical and physical transformations. However, the estimated mean apparent activation energy yields similar results with all four kinetic methods, ranging between 61.3 and 68.7 kJ mol−1, confirming the low thermal stability of the compound, which can be explained by the presence of reactive functional groups, such as the peroxide one. Regarding the biological activity of ART, it was shown that it can be used to induce cell growth arrest on human melanoma cell line A375, but affecting in a smaller measure the viability of HaCaT cell line, while the AOA is negligible, in comparison with standard antioxidants.

Thermal behavior of entacapone, a catechol-O-methyltransferase inhibitor used in Parkinson’s disease

Entacapone, a selective and reversible inhibitor of catechol-O-methyltransferase, is used in the treatment of Parkinson’s disease in combination with levodopa/carbidopa to treat the symptoms of end-of-dose “wearing-off” effect. Considering that new formulations are researched constantly, proper knowledge of the active pharmaceutical ingredients is crucial in the preformulation stages. Kinetic analysis was performed using three methods: one integral—Flynn–Wall–Ozawa method, one differential—Friedman method, and modified nonparametric kinetics method (NPK). The thermoanalytical curves were registered at five different heating rates: β = 5, 7, 10, 12, and 15 °C min−1. Analysis was conducted in the dynamic air atmosphere to highlight potential thermooxidative processes. This paper deals with the investigation of solid-state stability and compatibility of binary mixture of entacapone with various pharmaceutical excipients by two instrumental techniques, such as universal attenuated total reflection Fourier transform infrared and thermal analysis (TG/DTG/HF). The excipients used in the mixture were: mannitol, silicon dioxide, talc, sorbitol, magnesium stearate, and povidone.

A higher-order generalization of the NPK-method

A novel algorithm to identify the full kinetic model of solid state reactions according to the General Kinetic Equation is presented. It is a higher-order generalization of the Non-Parametric Kinetics method (NPK-method) and allows for the simultaneous identification of the conversion, temperature and pressure dependency from any combination of measurements. As a model-free identification method, it does not rely on a-priori assumptions about the kinetic model. The result vectors can be used to identify the kinetic parameters by means of model fitting for each variable independently.The steps of the algorithm are described and its effectiveness is demonstrated by applying it to simulated datasets. The kinetic parameters could be recovered very accurately from the test data, also in the presence of noise.Overall the higher order NPK-method is a very promising approach to derive kinetic models from experimental data with a minimum of a-priori assumptions about the reaction.

Сравнительный кинетический анализ термической деструкции гидрогеля на основе полиметилвинилового эфира малеиновой кислоты сшитого полипропиленгликолем

Kinetic analysis was made applying TG/DTG/HF data in nitrogen and air atmospherefor thermal decomposition of hydrogel of polymethylvinyl maleic acid ester, linked with polypropylene glycol, at different heating rates. TG/DTG/HF data were processed according to the followingkinetic models: Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Coates-Redfern and nonparametric kinetic method (NPK) was used, to obtain the following kinetic parameters: activationenergy and pre-exponential factor.According to the attained values of activation energy, the mechanism of degradation of the hydrogel was suggested. Values of kinetic parameters attained by different methods, are compliant to eachother. Isoconversion method is one of the methods for definition of activation energy; this methoddoes not require knowledge on analytical form of conversion function, and gives the possibility todefine the activation energy against conversion degree as well.To obtain full kinetic analysis it is necessary to process the data using non-parametric kineticmethod. Non-parametric kinetics method (NPK) of Serra, Nomen and Sempere is based upon thesuggestion that reaction velocity may be expressed as multiplication of two independent functions,f (α) and k (T). Reaction model f (α) considers the dependence of conversion degree, and k (T)considers the temperature dependence.

Non-parametric kinetic analysis of autocatalytic reactions

Commonly, classical kinetic approaches using a Šesták and Berggren (SB) model, α˙=k·αm·(1−α)n, describes the behaviour of autocatalytic processes after their initiation. However, the SB model does not consider any initiation reaction. Therefore, such a model has simulation restrictions and could not predict induction times, which have relevance in process safety, i.e. in thermal explosion/runaway prevention or in curing of some thermosetting resins. Some procedures for simultaneously considering both initiation and autocatalytic propagation reactions were proposed. Perhaps one of the most traditional is the model suggested by Dien et al. in the 1990s. According to this model, two reactions are considered (A→B; A+B→2B), and a combined kinetic equation, α˙=k1·(1−α)p+k2·αm·(1−α)n, is used to describe the process. Despite of this model could be considered realistic, the dramatic different sensitivity of its parameters make the numerical fitting of experimental data a quite impossible task if sets of senseless parameters have to be avoided. The non-parametric kinetics, (NPK) method developed by our group has been used to identify and describe single processes. Nevertheless, intrinsically NPK gives information about all simultaneous transformations taking place in a process. This work exposes how the different processes appear overlapped in the results of NPK. NPK methodology has been applied to the thermal decomposition of 2,4-dinitrophenol (DNP) and the curing reactions of Araldite Standard® and diglycidyl ether of bisphenol A (DGEBA) with diethylenetriamine (DETA). In all the cases, only the first pair of vectors – u1 and v1 – has significance in the reconstruction of the original data. The straight simulation of the experimental data using u1 and v1 without requiring theoretical models gives excellent results in all of the cases, demonstrating once again the potential of NPK. However, only one function of temperature or kinetic constant can be obtained for the whole process. NPK results confirm the suggestion of Dien et al., indicating that an autocatalytic process can be properly described as the sum of a 1st order reaction (RO) and a truncated Šesták and Berggren (SB) model. However, having only one expression for the kinetic constant, the final equation has the form α˙=A·e−Ea/(R·T)·[(1−α)+γ·αm·(1−α)n]. This model enables the prediction of induction times, improving working and safety conditions.

High-Temperature Energy Storage: Kinetic Investigations of the CuO/Cu2O Reaction Cycle

Thermochemical energy storage (TCES) is considered a possibility to enhance the energy utilization efficiency of various processes. One promising field is the application of thermochemical redox systems in combination with concentrated solar power (CSP). There, reactions of metal oxides are in the focus of research, because they allow for an increase in the process temperature. The reaction system CuO/Cu2O has been reported as a suitable candidate for TCES. For proper development and modeling of combined CSP–TCES processes, reliable kinetic data are necessary. This work studies the reduction of CuO and the oxidation of Cu2O under isothermal and isokinetic conditions. The reactions are analyzed using a simultaneous thermal analysis (STA) and a lab-scale fixed-bed reactor. The reaction behavior shows significant differences between both analyses. To develop kinetic models, the non-parametric kinetic (NPK) approach is used. This model-free approach is expanded by the Arrhenius correlation to increase the app...

Investigation of thermal-induced decomposition of iodoform

This paper presents the results obtained after the investigation of thermal-induced decomposition of tri-iodo-substituted methane (iodoform), under non-isothermal conditions in dynamic oxidative atmosphere (air flow). Iodoform was obtained in our laboratory through haloform reaction, namely the halogenation of dimethyl ketone in the presence of a base, and later purified according to literature. The kinetic study for the thermodegradation was carried out by processing the data by Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and modified nonparametric kinetic (NPK) methods. All the results obtained by the employment of isoconversional methods are in good agreement; the mean apparent activation energy was around 330 kJ mol−1, by all three methods. However, since variation larger than 10 % of E a versus α was noticed, the NPK method was employed, and the separation of physical versus chemical transformations of the sample was possible. NPK method suggested that the degradation of iodoform occur in two parallel processes, the main step being a chemical degradation (n = 1/3), while the parallel process is a physical–chemical one (n = 3/5; m = 1/3).