Non-isothermal Kinetic Parameters Research Articles

Applicability of smart heat resistive polymeric material by non-isothermal thermogravimetric analysis

Homopolymer (H-Mpmi) of 3 -chloro- substituted of N-phenyl maleimide (N-Mpmi) monomer, was synthesized at 60°C in THF using benzoyl peroxide (BPO) as a free radical initiator. The average molecular weight is determined by gel permeation chromatography (GPC). Thermal analysis reveals polymer show single step degradation. The TGA and DTA curves explain its percentage weight loss with temperature at different heating rate 5°C, 10 oC and 15 oC. The non-isothermal kinetic parameters values are obtained using Kissinger method. The activation energy (ΔE*), entropy of activation (ΔS*), enthalpy of activation (ΔH*) and Gibbs free energy (ΔG) increases gradually less with increase in heating rate. Since, endothermic peak was observed in the DTA of homopolymer of meta 3- chloro- substituted of N-phenyl maleimides, H-Mpmi suggesting large amount or bulk mass loss from polymeric chain

Concentration dependence of the elastic moduli, thermal properties, and non-isothermal kinetic parameters of Yb3+ doped multicomponent tellurite glass system

The thermal properties and the kinetic parameters of TeO2–Li2O–ZnO–Nb2O5–Yb2O3 glass series have been evaluated as a function of increasing Yb2O3 content. The theoretical elastic properties and the quantitative analysis (the link between the elastic features and the changed chemical composition of the glass) have been determined by the use of bond compression and Makishima–Mackenzie models. The thermal analysis Differential Scanning Calorimetry (DSC) test was used for estimating the glass characteristics temperatures, thermal stability, and non-isothermal kinetic parameters at the heating rates (β) 10, 15, 20 and 25 K/min. The activation energies of the glass transition 〈Eg〉 and crystallization 〈Ec〉, as well as the order of the crystallization reaction (n), have been computed by different models with clear consistency and harmony between them. It was found that the characteristics temperatures of transition (Tg), softening (Ts), the onset of the crystallization (Tx) and the crystallization (Tc) increased with increasing the heating rate. Also, the results showed the higher thermal stability values (>100 K) for the understudied glass which is confirmed by KSP and ((Tc–Tg)/Tg) parameters values. Calculating of (n) showed that the crystallization started with surface nucleation and finished with bulk volume nucleation with rising Yb2O3 (mol %). The computed elastic moduli were linked with the interpretation of the thermal parameters to give a comprehensive image of the studied glass system.

Pyrolysis Kinetics of Hydrochars Produced from Brewer’s Spent Grains

The current market situation shows that large quantities of the brewer’s spent grains (BSG)—the leftovers from the beer productions—are not fully utilized as cattle feed. The untapped BSG is a promising feedstock for cheap and environmentally friendly production of carbonaceous materials in thermochemical processes like hydrothermal carbonization (HTC) or pyrolysis. The use of a singular process results in the production of inappropriate material (HTC) or insufficient economic feasibility (pyrolysis), which hinders their application on a larger scale. The coupling of both processes can create synergies and allow the mentioned obstacles to be overcome. To investigate the possibility of coupling both processes, we analyzed the thermal degradation of raw BSG and BSG-derived hydrochars and assessed the solid material yield from the singular as well as the coupled processes. This publication reports the non-isothermal kinetic parameters of pyrolytic degradation of BSG and derived hydrochars produced in three different conditions (temperature-retention time). It also contains a summary of their pyrolytic char yield at four different temperatures. The obtained KAS (Kissinger–Akahira–Sunose) average activation energy was 285, 147, 170, and 188 kJ mol−1 for BSG, HTC-180-4, HTC-220-2, and HTC-220-4, respectively. The pyrochar yield for all hydrochar cases was significantly higher than for BSG, and it increased with the severity of the HTC’s conditions. The results reveal synergies resulting from coupling both processes, both in the yield and the reduction of the thermal load of the conversion process. According to these promising results, the coupling of both conversion processes can be beneficial. Nevertheless, drying and overall energy efficiency, as well as larger scale assessment, still need to be conducted to fully confirm the concept.

Model-fitting approach to kinetic analysis of non-isothermal pyrolysis of pure and crude glycerol

The pyrolysis of pure and crude glycerol from a transesterification process of waste cooking oil to biodiesel was investigated using thermogravimetric analysis. Unlike the pure glycerol that shows a single mass drop, there were five distinct phases in the pyrolysis of crude glycerol. Pure glycerol decomposed completely within the temperature range from (133–158) to (240–279) °C depending on the heating rate. Leaving behind a small mass fraction (less than 1%) of pyrolysis residues. However, the crude glycerol is more thermally stable over the second and third decomposition phases range from (138–151) to (357–401) °C leaving a large mass fraction of residue (∼12–13%). Model fitting methods of the Direct Differential and Coats-Redfern methods were used to evaluate non-isothermal kinetic parameters in the second phase using 24 reaction models. The activation energy obtained by compensation effect of direct differential method and Coats-Redfern method were (82.611 kJ/mol and 74.890 kJ/mol) and (74.253 kJ/mol and 58.281 kJ/mol) for the pure and crude glycerol, respectively. The best reaction models obtained by the highest R2 and the master plot. The reaction order was calculated by Avrami theory, and the average value of 0.918 and 1.317 was obtained for the pure and crude glycerol, respectively.

Comparison of the kinetic behavior of crystalline cane and beet sucrose thermal decomposition

Although crystalline cane and beet sucrose are > 99.8% pure, they exhibit different thermal behavior. In general, the cane sucrose DSC curve contains a small endothermic peak before the main endothermic peak, which is not present in the beet DSC curve, leading to a lower onset temperature for thermal decomposition in cane. To compare their thermal behavior, the thermal decomposition kinetic parameters for analytical and commercial cane sucrose and commercial beet sucrose were determined. Beet sucrose had a higher activation energy than either cane source, indicating that thermal decomposition is inhibited in beet sucrose. However, the k values from isothermal experiments at a single temperature did not match the nonisothermally predicted k values, suggesting that, while useful for comparison, the nonisothermal kinetic parameters cannot be used to predict the behavior of sucrose thermal decomposition under isothermal conditions.

Synthesis, structure analysis and thermal behavior of two new complexes: Cu(NH3)4(AFT)2 and Cu(C3H6N2H4)2(AFT)2

Two new energetic complexes base on nitrogen-rich compound 4-amino-3-(5-tetrazolate)-furazan: Cu(NH3)4 (AFT)2 (1) and Cu(C3H6N2H4)2 (AFT)2 (2) were synthesized by reaction of Cu(NO3)2·3H2O with ammonia and diaminopropane. For complexes 1 and 2, they were fully characterized by EA and FT-IR. The crystal structure of complex 1 was determined by single-crystal X-ray diffraction. X-ray single-crystal diffraction analysis revealed that the complex 1 crystallized in orthorhombic crystal system. The thermal decomposition behaviors of the two complexes were studied with DSC and TG/DTG methods. The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa-Doyle's method for the main exothermic decomposition processes of the title compounds. Moreover, the entropy of activation (ΔS≠), the enthalpy of activation (ΔH≠) and the free energy of activation (ΔG≠) were calculated. The specific heat capacity (Cp) and mechanical sensitivity were also investigated.

Cocrystallization of chelating-energetic-material and metal-organic-framework with the nitrogen-rich ligand bis(tetrazole)methane

abstractTwo recently introduced concepts in the design of high-energy-density materials (HEDMs), namely Metal–organic frameworks (MOFs) and Chelating energetic material (CEM), have been applied in the synthesis of the energetic manganese (II) compound {[Mn(btm)(H2O)3]2·H2O}n (1) (H2btm = bis(tetrazole)methane), cocrystalized by a dinuclear CEM and a 1D MOF, which is characterized by elemental analysis and FTIR spectroscopy. Single-crystal X-ray diffraction analysis revealed that 1 crystallizes in the monoclinic space group P21/c. The Mn2+ was hexa-coordinated with two btm groups and three water molecules. Btm presents tridentate coordination modes. The thermal decomposition mechanism of 1 was studied by differential scanning calorimetry (DSC). The non-isothermal kinetics parameters were calculated by the Kissinger’s method and Ozawa-Doyle’s method, respectively. Sensitivity tests revealed that 1 is insensitive to mechanical stimuli.

Ethylethanolammonium 4-nitrobenzoate

The demand for corrosion inhibitors with low toxicity has increased in the last years in a wide range of sectors. Our study presents the synthesis, X-ray structure, thermal and kinetic investigation of ethylethanolammonium 4-nitrobenzoate (EEA4NB) as corrosion inhibitor for iron in 3% NaCl solution. Proton transfer and hydrogen bonding in the organic salt were elucidated and confirmed by infrared spectroscopy and single-crystal X-ray diffraction. Simultaneous TGA–DTA and heat flow analysis were used to study the thermal and kinetic behavior of EEA4NB. The results provided useful information about thermal stability and thermal decomposition. The non-isothermal kinetic parameters were estimated by using three different kinetic methods. Electrochemical corrosion measurements show corrosion inhibitor efficiency of EEA4NB for iron in 3% NaCl solution higher than 92% and a decrease of corrosion current and corrosion rate as a result of adsorption of EEA4NB molecules at the metal/solution interface.

Using DSC technique to investigate the non-isothermal gelation kinetics of the multi-crosslinked Chromium acetate (Cr3+)-Polyethyleneimine (PEI)-Polymer gel sealant

Polymer gel based on multi-crosslinking is aroused great interesting in the aspect of oil/and or gas well water shutoff and temporary plugging in well completion and workover. While the complex gelation mechanism is not well understood. Most previous studies focus on using a coarse method such as rheological techniques or simple bottle test to investigate the gelation kinetic. This work presents the first attempt to use the DSC technique to study the non-isothermal gelation kinetic of the multi-crosslinking gel system. The target polymer gel is reported in our previous study, which is a multi-crosslinked Cr3+-PEI-SPAM gel. The DSC curve shows an endotherm peak followed by an exotherm peak, indicating the multiple reactions taken place during the heating of Cr3+-PEI-SPAM gel system. The endothermic process shows that the first gelation reaction occurs between the SPAM and Cr3+. And the exothermic process can be regarded as the secondary gelation reaction between the SPAM and PEI. Non-isothermal gelation kinetic parameters were determined by Jeziorny model, Mo's model and Rate model, respectively. All results show a good linear relationship with the experimental data. The non-isothermal gelation kinetic parameters from the Jeziorny model indicate that the gelation mechanism between Cr3+-SPAM and PEI-SPAM is very different. The results of Mo's model show that the gelation process becomes difficult as the gelation progresses. Non-isothermal gelation kinetic parameters calculated from the Rate model indicate that the crosslinking between SPAM and Cr3+ is a multistage reaction including three stages, while the crosslinking between SPAM and PEI only has two stages.

Preparation and crystallization kinetics of polyesteramide based on poly(L-lactic acid)

AbstractUsing the melt polycondensation method, a polyesteramide was prepared based on poly(L-lactic acid) prepolymer and poly(ε-caprolactam) prepolymer and was characterized by Fourier transform infrared spectroscopy and 1H-NMR. Isothermal crystallization behavior at different temperatures and non-isothermal crystallization kinetics at different cooling rates were investigated by differential scanning calorimetry, and non-isothermal crystallization kinetics parameters were obtained using the Mo, Ozawa and Jeziorny methods. It was found that the increased cooling rates led to the broadening of the polyesteramide crystallization peaks and their shift toward lower temperatures. Mo and Jeziorny methods were found to be more suitable than the Ozawa method for the analysis of this system, as shown by the comparison these non-isothermal crystallization analysis methods. In addition, the values of activation energy of non-isothermal crystallization for polyesteramide obtained by the Kissinger and Takhor methods were −155.96 and −149.12 kJ/mol, respectively.

Nitrogen-rich salts of 5,5′-bistetrazole-1,1′-diolate: Syntheses, structures and properties

A series of new nitrogen-rich energetic salts containing 1H,1′H-[5,5′-bitetrazole]-1,1′-diol (BTO) anion and ethane-1,2-diaminium (1), 1-amino-1H-1,2,3-triazol-3-ium (2), 4-amino-4H-1,2,4-triazol-1-ium (3) and 4,5-diamino-4H-1,2,4-triazol-1-ium (4) cations were synthesized by direct salt formation or by metathesis strategy. The structures of energetic salts 1-4 were comprehensively characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopies and by X-ray crystallography. DSC and TGA methods were used to study thermal properties of these salts. Additionally, the non-isothermal kinetic parameters and thermodynamic parameters were calculated by utilizing the Kissinger's and Ozawa-Doyle's methods. The enthalpies of formation for all target compounds in this study were calculated, and their sensitivity to mechanical impact and friction was tested according to BAM guidelines. We found these new energetic salts exhibit good thermal stability and have typical decomposition temperatures above 230 °C, except for the salt 2. All our salts have highly-positive enthalpies of formation (311.1–473.6 kJ mol−1) and are insensitive to impact and friction stimuli (>40 J, 120 N). With a high nitrogen-rich content, high enthalpy of formation, good thermostability and very low sensitivity to impact, some of these new salts may have a potential for application in the field of environmentally friendly insensitive energetic materials.

Thermal behavior and compatibility study of dihydroxylammonium 3,4-dinitraminofurazan

ABSTRACTA large number of nitramino-featured energetic salts have been reported and some of them show promising properties. Among them, the dihydroxylammonium 3,4-dinitraminofurazan (HADNAF) is easy to synthesize and shows high calculated detonation performances and acceptable thermal stability. The non-isothermal kinetics parameters of HADNAF including the apparent activation energy (E) and pre-exponential factor (A) of the exothermic decomposition reaction, and activation entropy (ΔS≠), activation enthalpy (ΔH≠), activation Gibbs free energy (ΔG≠) at TP0 of the reaction and the critical temperature of thermal explosion (Tb) were obtained by Kissinger’s and Ozawa’s method, respectively. Additionally, the compatibility of HADNAF with other materials (e.g. TNT, RDX, HMX, B, Mg) was tested by DSC method.

The synthesis, crystal structure and thermal properties of an energetic compound: the hydrated azanium salt of 3,6-bis[(1H-1,2,3,4-tetrazol-5-yl)amino]-1,2,4,5-tetrazine.

The energetic ionic salt bis(1-aminoguanidin-2-ium) 5,5'-[1,2,4,5-tetrazine-3,6-diylbis(azanediyl)]bis(1H-1,2,3,4-tetrazol-1-ide) dihydrate, 2CH7N4+·C4H2N142-·2H2O, (I), with a high nitrogen content, has been synthesized and examined by elemental analysis, Fourier transform IR spectrometry, 1H NMR spectroscopy and single-crystal X-ray crystallography. Compound (I) crystallizes in the monoclinic space group P21/c with two water molecules. However, the water molecules are disordered about an inversion centre and were modelled as half-occupancy molecules in the structure. The crystal structure reveals a three-dimensional network of molecules linked through N-H...N, N-H...O, O-H...N and O-H...O hydrogen bonds. Thermal decomposition was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The exothermic peak temperature is 509.72 K, which indicates that hydrated salt (I) exhibits good thermal stability. Non-isothermal reaction kinetic parameters were calculated via both the Kissinger and the Ozawa methods to yield activation energies of Ek = 239.07 kJ mol-1, lgAk = 22.79 s-1 and EO = 235.38 kJ mol-1 for (I). Additionally, the thermal safety was evaluated by calculating critical temperatures and thermodynamic values, viz. TSADT, TTIT, Tb, ΔS≠, ΔH≠ and ΔG≠. The results reveal that (I) exhibits good thermal safety compared to other ion salts of 3,6-bis[(1H-1,2,3,4-tetrazol-5-yl)amino]-1,2,4,5-tetrazine (BTATz).

1D energetic metal–organic frameworks assembled with energetic combination of furazan and tetrazole

Two novel 1D Cd(II) energetic MOFs [Cd(NH2NH2)(AFT)2·0.7H2O]n (1) and [Cd(ODH)1.5(AFT)2·5H2O]n (2), combining the advantages of tetrazole-ring and furazan-ring, were successfully synthesized based on 2D energetic MOF [Cd(H2O)2(AFT)2]n (3, AFT=4-amino-3-(5-tetrazolate)-furazan, ODHNH2NHCOCONHNH2oxalyl-dihydrazide). The crystal structures were determined by single-crystal X-ray diffraction, and fully characterized by elemental analysis and FT-IR spectroscopy. The thermal stability and impact sensitivity were also investigated. For 1, 1D energetic MOF had an outstanding thermal stability (Tp>300 °C) and insensitivity (IS>24.5 J). In addition, the non-isothermal kinetics parameters, critical temperature of thermal explosion, entropy of activation, enthalpy of activation and free energy of activation were discussed in detail. For 2, it was revealed that the each Cd(II) cation is located in a unique hepta-coordination environment. Noticeably, tetrazole-ring of AFT group presents typical monodentate coordination mode, and ODH molecule presents typical tridentate and tetradentate coordination modes, featuring a one-dimensional chain structure. Therefore, the reasonable assembly strategy plays a decisive role in energetic properties of MOF-based energetic materials.

Comparison of Different Kinetic Models for Heavy Oil Oxidation Characteristic Evaluation

Despite many studies of heavy oil oxidation characteristics, kinetic mechanisms with the comparison of different kinetics models are not well understood, because of the complexities of oil components and nonisothermal oxidation processes. Moreover, it is urgent to further evaluate the feasibility and accuracy variations of different kinetic models to optimize the kinetic model for specific situations and purposes. Therefore, thermogravimetry (TG-DTG)/differential scanning calorimeter (DSC-DDSC) thermograms under different heating rates were comprehensively studied in this work to elucidate the nonisothermal oxidation behavior with the heating rate influence. Then, based on the comparison analysis of model-fitting and model-free methods, the comparisons of kinetic parameters, reaction order, and activation energy distribution were evaluated. In addition, the results indicated the nonisothermal oxidation kinetics parameters varied with the reaction orders and kinetic models. Besides, an obvious increase of ...

Evaluation of the oxidative stability of chia oil-loaded microparticles by thermal, spectroscopic and chemometric methods

Chia oil has been widely studied due to its benefits to human health, being source of important omega-3 and omega-6. Encapsulation has been studied in order to protect the oil from thermal degradation. In this work, oil from chia seeds was microencapsulated in carnauba wax and thermal stability was evaluated not only by thermal methods but also Spectroscopy and chemometric based analyses. High encapsulation efficiency of both omega-3 and -6 (up to 97%) was verified. Particles presented micrometric sizes, spherical shape and no fissures. Differential Scanning Calorimetry was applied in isothermal and non-isothermal modes and kinetic parameters were determined using the Ozawa-Flynn-Wall (OFW) method. An effective protection of the chia oil was verified by an increase in the oxidative stability in both isothermal (activation energy increased from 73.5 ± 1.5 to 91.8 ± 1.6 kJ mol−1) and non-isothermal (from 87.4 ± 2.1 to 97.3 ± 2.9 kJ mol−1) tests. Increase in the onset oxidation temperature and in the oxidation induction time were also detected. Chia oil and oil-loaded microparticles were subjected to accelerated stability test. Degradation was evaluated by the UV-Vis spectroscopy coupled to chemometry and also by the extinction coefficients, corroborating the increase in the oxidative stability.

Superior Thermostability, Good Detonation Properties, Insensitivity, and the Effect on the Thermal Decomposition of Ammonium Perchlorate for a New Solvent-Free 3D Energetic PbII -MOF.

A new solvent-free energetic MOF, [Pb(HBTI)]n (1) (H3 BTI=4,5-bis(1H-tetrazole)-1H-imidazole), has been synthesized under hydrothermal and acidic conditions. It was characterized by elemental analysis, IR, thermogravimetric, differential scanning calorimetry (DSC) and SEM. Single crystal X-ray diffraction analysis revealed that 1 features a rigid 3D framework architecture free of solvent molecules. Thermal analysis demonstrated that the thermostability of 1 was up to 325 °C. Non-isothermal kinetic and apparent thermodynamic parameters of exothermic decomposition process of 1 were determined by Kissinger's and Ozawa's methods. Through oxygen-bomb combustion calorimetry, the standard molar enthalpy of formation of 1 was determined. The calculated detonation properties (heat of detonation, detonation velocity and detonation pressure) and sensitivity tests of 1 were carried out. In addition, 1 was explored as combustion promoter to accelerate the thermal decompositions of ammonium perchlorate (AP) by differential scanning calorimetry. Experimental results indicated that 1 possesses potential application prospects in the field of explosives and propellants.

Seven-coordinated chelate [Cd(SCZ)3·H2O](HTNR)2(H2O)2: Synthesis, crystal structure and energetic properties

ABSTRACTTo deepen the study on heptacoordinate transition metal coordination complexes, a novel seven-coordinated coordination compound [Cd(SCZ)3·H2O](HTNR)2(H2O)2 (1, SCZ = semicarbazide, H2TNR = styphnic acid) was synthesized and characterized by elemental analysis and FTIR spectroscopy. Single-crystal X-ray diffraction analysis revealed that 1 crystallizes in the triclinic space group P-1. The thermal decomposition mechanism of 1 was studied by differential scanning calorimetry (DSC). The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa-Doyle's method, respectively. Sensitivity tests revealed that 1 is insensitive to mechanical stimuli. The heat of combustion was measured by oxygen bomb calorimetry and the enthalpy of formation was calculated.

Synthesis, Crystal Structure, and Properties of Energetic Copper(II) Complex based on 3,5-Dinitrobenzoic Acid and 1,5-Diaminotetrazole

Energetic copper(II) complexes based on 3,5-dinitrobenzoic acid (HDNBA) and 1,5-diaminotetrazole (DAT), Cu(DNBA)(2)(H2O)(2) (1) and Cu(DAT)(2)(DNBA)(2) (2) were synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal and powder X-ray diffraction. In both complexes, Cu-II was coordinated to a plane tetragon, by four oxygen atoms from two DNBA(-) ions and two coordinated H2O molecules for 1, and by two oxygen atoms and two nitrogen atoms from different DNBA(-) ions and DAT ligands for 2. Differential scanning calorimetry (DSC) and thermogravimetry (TG) analyses were employed to measure the thermal decomposition processes and non-isothermal kinetics parameters of the complexes. The thermal decomposition onset temperatures of 1 and 2 are 321 and 177 degrees C. The apparent activation energies of the first exothermic decomposition peaks of 1 and 2 are 247.2 and 185.2 kJmol(-1). Both 1 (35 J, > 360 N) and 2 (12.5 J, > 360 N) are less sensitive than RDX. The catalytic effects on the decomposition of ammonium perchlorate (AP) of 1 and 2 were studied by DSC. All results supported the potential applications of the energetic complexes as additives of solid rocket propellants.

Two Energetic Salts based on 5,5′-Bitetrazole-1,1′-diolate: Syntheses, Characterization, and Properties

Two salts based on 1H,1′H-5,5′-bitetrazole-1,1′-diolate (BTO) anion with pyrazole (1) and imidazole (2) cations were synthesized with metathesis reactions. Structural characterization was accomplished for them by using the element analysis, Fourier transform infrared spectroscopy (FT-IR), NMR and mass spectrum, and X-ray single crystal diffraction. Thermal analysis for the title salts were determined by means of differential scanning calorimetry (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG) as well as the calculation of non-isothermal kinetic parameters. Consequently, both salts shown acceptable thermal stabilities as the decomposition temperatures were over 200 °C. The enthalpies of formation were calculated for these salts using the measured combustion energies with a result of 70.6 kJ·mol–1 for 1 and –47.8 kJ·mol–1 for 2, respectively. Impact and friction sensitivities were also tested and the results indicated that these salts both have low sensitivities (>40 J, 120 N). The title energetic salts possess acceptable performance, they can therefore be applied in the field of energetic materials.