Activation Energy Of Thermal Decomposition Research Articles

Thermal properties and CT-DNA/BSA binding behavior of a binuclear Cu(II) complex with acylhydrazone containing naphthalene ring

A novel Cu(II) complex [Cu2L2(NO3)2] with 2-hydroxy-1-naphthaldehyde-(4’hydroxy)phenylacetyl hydrazone (C19H14N2O2·H2O, HL) was synthesized. The structure of [Cu2L2(NO3)2] was characterized by X-ray single-crystal diffraction and can be described as a distorted rectangular pyramid with binuclear coordination. IR, UV–vis and EPR spectra are used to discuss the structure of Cu(II) complex in different conditions. Magnetic properties were determined by EPR spectra and magnetic susceptibility studies, showing magnetic exchange interaction and weak antiferromagnetic exchange between two Cu(II) ions. The apparent activation energy (Ea) of thermal decomposition of compounds indicated that the thermal stability of [Cu2L2(NO3)2] is better than HL. The CT-DNA binding behavior of compounds was determined by UV–vis absorption and viscosity measurements and the results confirmed an intercalative binding mode with CT-DNA. Kb obtained was 6.24(±0.12) × 106 M−1 and 3.09(±0.006) × 106 M−1 for [Cu2L2(NO3)2] and HL, respectively, revealing that the binding ability of [Cu2L2(NO3)2] with CT-DNA was stronger. The thermogenic curves of compounds interacting with CT-DNA were monitored by microcalorimetry, showing they were all endothermic reactions with reaction within 27–42 min; interaction enthalpies (ΔH) of [Cu2L2(NO3)2] and HL were 30.3 and 4.31 kJ mol−1. Binding studies with BSA were evaluated by fluorescence spectroscopy and the same relative interactions were found comparing with the above CT-DNA experiments.

MnCo2O4 nanoparticles with excellent catalytic activity in thermal decomposition of ammonium perchlorate

MnCo2O4 spinel nanoparticles (NPs) have been prepared using Aloe vera gel solution. The characterization of prepared spinel was performed applying Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron spectroscope, scanning electron microscope and dynamic light scattering. The results manifested that the prepared nanoparticles were mainly spherical plus minor agglomeration with average size distribution between 35 and 60 nm. The catalytic activity of the prepared nanoparticles upon thermal degradation of ammonium perchlorate (AP) was evaluated applying differential scanning calorimetry and thermogravimetry instruments. MnCo2O4 nanoparticles increased the released heat of AP from 450 to 1480 J g−1 and decreased the decomposition temperature from 420 to 293 °C. The kinetic parameters obtained from Kissinger methods showed that the activation energy of AP thermal decomposition in the presence of MnCo2O4 NPs considerably decreased. Also, a mechanism has been proposed in the presence of catalyst for the process of thermal decomposition of AP.

Investigation of simultaneous formation of nano-sized CuO and ZnO on the thermal decomposition of ammonium perchlorate for composite solid propellants

Core/shell composites of CuC2O4·2H2O@AP and ZnC2O4·2H2O@AP were prepared from metal oxalates on suspended AP particles in ethanol. CuO and ZnO nano-metal oxides as the nano-catalysts were made from CuC2O4·2H2O and ZnC2O4·2H2O simultaneously by thermal decomposition of AP. The particle size of CuO nano-particles was very finer, and the ZnO particles showed a considerable growth during formation. The kinetic triplet of activation energy, frequency factor, and model of thermal decomposition of pure AP, CuC2O4·2H2O@AP, and ZnC2O4·2H2O@AP composites were estimated by applying three model-free (FWO, KAS, and Starink) and model-fitting (Starink) methods. Based on the thermal analysis, the CuC2O4@AP composite has better catalytic performance and the thermal decomposition temperature of AP decreased to about 126.44 °C.

Polymer complexes. LXX. Synthesis, spectroscopic studies, thermal properties and antimicrobial activity of metal(II) polymer complexes

The monomer 3‐allyl‐5‐(phenylazo)‐2‐thioxothiazolidine‐4‐one (HL) was prepared by the reaction of allyl rhodanine with aniline through diazo‐coupling reaction. Reaction of HL with Ni(II) or Co(II) salts gave polymer complexes (1–8) with general stoichiometries [M(HL)(Cl)2(OH2)2]n, [M(HL)(O2SO2)(OH2)2]n, [M(L)(O2NO)(H2O)2]n and [M(L)(O2CCH3)(H2O)2]n (where M = Ni(II) or Co(II)). The structures of the polymer complexes were identified using elemental analysis, infrared and electronic spectra, molar conductance, magnetic susceptibility, X‐ray diffraction and thermogravimetric analysis. The interaction between the polymer complexes and calf thymus DNA showed a hypochromism effect. HL and its polymer complexes were tested against bacterial and fungal species. Co(II) polymer complex 2 is the most effective against Klebsiella pneumoniae and is more active than penicillin. The results showed that Ni(II) polymer complex 5 is a good antibacterial agent against Staphylococcus aureus and Pseudomonas aeruginosa. Molecular docking was used to predict the binding between the monomer with the receptors of prostate cancer (PDB code: 2Q7L Hormone) and breast cancer (PDB code: 1JNX Gene regulation). Coats–Redfern and Horowitz–Metzger methods were applied for calculating the thermodynamic parameters of HL and its polymer complexes. The thermal activation energy of decomposition for HL is higher than that for the polymer complexes.

Facile synthesis of oligo(4‐methoxyphenol) in water and evaluation of its efficiency in stabilization of polypropylene

A hindered polyphenol, oligo(4‐methoxyphenol), has been first successfully synthesized via a mild biocatalytic pathway using horseradish peroxidase as catalyst in water without any additive. Then the efficiency of oligo(4‐methoxyphenol) in stabilization of polypropylene (PP) was evaluated in terms of thermal analysis and accelerated aging test. It was observed that the apparent activation energy for thermal decomposition of PP/oligo(4‐methoxyphenol) calculated by Friedman's method is higher than that of virgin PP. Oligo(4‐methoxyphenol)‐stabilized PP maintains its tensile strength even after aging at 120°C for 800 hours. Oxidation induction time and onset oxidation temperature of PP/oligo(4‐methoxyphenol) are higher than both virgin PP and PP/4‐methoxyphenol, as well as PP stabilized with commercially available 6‐di‐tert‐buty‐4‐methylphenol or 1076. These results indicate that oligo(4‐methoxyphenol) can effectively improve the thermo‐oxidative resistance of PP. Noting that oligo(4‐methoxyphenol) is synthesized via enzymatic polymerization in water under mild condition with a facile procedure, oligo(4‐methoxyphenol) is thus proposed as a new efficiency and readily available antioxidant for PP.

Boron Nitride를 함유한 열경화성 액정 에폭시의 열분해 거동

A liquid crystalline thermosetting-epoxy-based composite was fabricated using diglycidyl ether of 4,4''-biphenol, boron nitride as the filler, and sulfanilamide as the curing agent. To investigate the thermal behavior, thermogravimetric analysis was performed, and temperature differences of the sample were recorded when using 1.0-7.0 wt.% boron nitride. The activation energy for thermal decomposition was calculated using the Kissinger method and Flynn-wall method. The results showed that the activation energy was proportional to the amount of added filler.

Kinetics of biomass low-temperature pyrolysis by coats–redfern method

Energy is one of the main sources of environmental pollution. In this regard, the world scientific community seeks to reduce its negative impact on human health and nature. To do this, some of the organic raw materials, which are fuel for power plants, are gradually replaced by renewable resources, in particular - biomass. The combustion of biomass by traditional methods is accompanied by high operating costs, which leads to the conclusion that it is necessary to process it into energy-valuable products. The development of one of the most promising such directions - thermal processing - requires studying the thermophysical properties of biomass and studying its kinetics of decomposition. The aim of this work is to estimate the activation energy of thermal decomposition of biomass by the method of Coats-Redfern.

Thermal Decomposition of Hydroxylamine Nitrate Studied by Differential Scanning Calorimetry Analysis and Density Functional Theory Calculations

The thermal stability and kinetics of hydroxylamine nitrate (HAN) decomposition were studied by differential scanning calorimetry (DSC) and the thermal decomposition reaction mechanism was determined by density functional theory (DFT). With the help of parameter values from the non-isothermal DSC curves of HAN, the thermal decomposition activation energy and pre-exponential constant were obtained by the Kissinger and Ozawa methods. Then, the most probable mechanism function was calculated by the Šatava–Šesták method. Seven different paths for the thermal decomposition mechanism of HAN were formulated and DFT at the B3LYP/6-311++G(d,p) level was used to carry out the dynamics analysis. The calculated results show that the values of the activation energy calculated by the Kissinger and Ozawa methods are 67.892 and 70.412 kJ mol−1 respectively. The most probable mechanism function calculated by the Šatava–Šesták method is [Formula: see text]. The path being favoured energetically in the dynamics is in the order: Path6 > Path5 > Path4 > Path1 > Path2 > Path7 > Path3.

Modifications in the optical and thermal properties of a CR-39 polymeric detector induced by high doses of γ-radiation

Effects of γ-radiation on the optical and thermal properties of a poly allyl diglycol carbonate (PADC), a form of CR-39, polymer have been investigated. CR-39 detectors were exposed to γ-rays at very high doses ranging from 5.0 × 105 to 3.0 × 106Gy. The induced changes were analyzed using ultraviolet-visible spectroscopy (UV–VIS) in absorbance mode, and thermogravimetric analysis (TGA). The UV–visible spectra of the virgin and γ-irradiated CR-39 polymer detectors displayed a significant decreasing trend in their optical energy band gaps for indirect transitions, whereas for the direct ones showed a little change. This drop in the energy band gap with increasing dose is discussed on the basis of the gamma irradiation induced modifications in the CR-39 polymeric detector. The TGA thermograms show that the weight loss rate increased with increase in dose, which may be due to the disordered system via scission followed by crosslinking in the irradiated polymer detector. The TGA thermograms also indicated that the CR-39 detector decomposed in three/four stages for the virgin and irradiated samples. The activation energy for thermal decomposition was determined using a type of Arrhenius equation based on the TGA experimental results. These experimental results so obtained can be well used in radiation dosimetry.

Thermal studies on Arabic gum - carrageenan polysaccharides film

<p>The main objective of this work is to develop film and study the thermal characteristics of polysaccharides films at various concentration of carrageenan in the mixture by calculating activation energy of polysaccharides films. There were four (4) film samples of two polysaccharides combination; arabic gum (AG) and carrageenan (C) with different formulations; sample A, sample B, sample C and sample D prepared. Sample A film is the control sample that contained only arabic gum and distilled water (DI) with 40% weight arabic gum per volume DI water (w/v%). Meanwhile for sample B and C were prepared with concentration 40 w/v% of Arabic gum and two differents of carrageenan concentrations; 1 w/v% and 10 w/v% respectively. Polyethylene glycol 400 (PEG 400) as a plasticiser was added into sample D film. The sample films were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The major thermal transitions as well as, activation energies of the major decomposition stages were determined. Sample A and B films exhibited the highest (112.43 kJ/mol) and the lowest (102.89 kJ/mol) activation energy of thermal decomposition, respectively. The activation energies were lower at larger amounts of sulfate groups from carrageenan on the degradation reactions. The DSC trend for all samples shows two (2) major intense peaks recorded in the DSC thermograms; an endothermic transition at temperature around 100<sup>°</sup>C and followed by an exothermic transition at temperature around 300<sup>°</sup>C. The endothermic transition is due to the heat absorption for dehydration of water, H2O and the decomposition of samples process. Meanwhile, the exothermic transition is caused by the formation of H<sub>2</sub>O, CO and CH<sub>4</sub> in polysaccharide film from dehydration, depolymerisation and decomposition at the high-temperature stages.</p><p>Chemical Engineering Research Bulletin 19(2017) 80-86</p>

Green synthesis of ZnCo2O4 nanoparticles by Aloe albiflora extract and its application as catalyst on the thermal decomposition of ammonium perchlorate

ZnCo2O4 nanoparticles were prepared by green method using Aloe albiflora extract solution and characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy, and the result showed that the average particle size was <30 nm. The effect of the ZnCo2O4 nanoparticles on thermal decomposition of ammonium perchlorate (AP) was enhancing the evolved heat from 400 to 1505 J g−1 and a decrease of decomposition temperature from 420 to 310 °C. The kinetic parameters of thermal decomposition of both pure AP and catalyzed sample have been calculated by Kissinger method, and the results showed that the values of pre-exponential factor and activation energy of thermal decomposition of catalyzed sample increased with respect to that of pure AP. However, the calculated rate constant was higher in presence of ZnCo2O4 nanoparticles.

A Combined Theoretical and Experimental Study of Sarin (GB) Decomposition at High Temperatures.

Theoretical and experimental results are presented for the pyrolytic decomposition of the nerve agent sarin (GB) in the gas phase. High-level quantum chemistry calculations are performed together with a semiclassical transition-state theory for describing quantum mechanical tunneling. The experimental and theoretical results for the temperature dependence of the survival times show very good agreement, as does the calculated and measured activation energy for thermal decomposition. The combined results suggest that the thermal decomposition of GB, for temperature ranging from 350 to 500 °C, goes through a pericyclic reaction mechanism with a transition state consisting of a six-membered ring structure.

Characterization, thermal behavior, and electrical measurements of poly[4‐(2‐bromoisobutyroyl methyl)styrene

AbstractThe 4‐(2‐bromoisobutyroyl methyl)styrene [BBMS] monomer was synthesized. The homopolymer of BBMS was prepared by free radical polymerization method. The decomposition behavior of P(BBMS) was thermally investigated by thermogravimetric analysis (TGA). For thermal decomposition kinetics of poly(BBMS), Flynn–Wall–Ozawa method was applied to thermogravimetry curves. The first step, which is one of the two decomposition stages, is comprehensively related to elimination of hydrogen bromide and the other step is related to a multi‐step process. The activation energy (Ea) of thermal decomposition of the first step and 50% weight loss is 148.5 and 190.7 kJ/mol, respectively. The results showed that the side group elimination without chain breaking comprehensively proceeded at lower temperature, and at progressive temperatures subsequently the specific chain scission did so. Degradation of poly(BBMS) did not lead to depolymerization. 1H, 13C‐NMR, and FT‐IR analyses showed that the decomposition products during degradation of poly(BBMS) to 260°C were comprehensively HBr and methacrylic acid. Electrically conducting graphene‐based poly(BBMS) composites were prepared. The DC and AC electrical measurements of graphene‐based poly(BBMS) composites were carried out. The AC dielectric measurements of poly(BBMS) were investigated up to 70°C between 100 Hz and 20 kHz depending on the alternating current conductivities. The dipolar functional groups (C–O, C=O, and Br) of the BBMS segment possesses significantly affect the dielectric constant. Also, the activation energy profile of different graphene/poly(BBMS) composites were revealed by measuring DC conductivity of individual composite material.

Thermal stability and mechanical properties of hybrid materials based on nitrocellulose grafted by aminopropylisobutyl polyhedral oligomeric silsesquioxane

The need for improvement in nitrocellulose (NC) storage safety and convenience of application requires an increase in NC thermal stability and enhancement of its mechanical properties. To this aim, hybrid materials were synthesized by grafting NC with aminopropylisobutyl polyhedral oligomeric silsesquioxane (amino-POSS) using isophorone diisocyanate (IPDI) as a crosslinking agent. The structure and elemental composition of the resulting products were confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR and 29Si NMR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It was found, based on the silicon mapping using energy dispersive X-ray spectroscopy (EDS), that amino-POSS was well dispersed in NC matrix. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) studies showed that hybrid amino-POSS-NC materials have higher thermal decomposition activation energy (Ea) compared to NC control sample. According to TGA results, the temperatures of 5 % weight loss (T5 %) and 50 % weight loss (T50 %) as well as the residual masses at 240 °C (CR240 °C), were increased as a result of NC modification with amino-POSS. As can be seen from the digital and scanning electron microscopy (SEM) images, the char layers of amino-POSS-NC hybrid materials after burning in air became more compact with increasing amino-POSS content. XPS studies have shown an increased content of the graphitized carbon in the char residues of the modified samples. The results of DSC, TGA, SEM and XPS studies have directly proved the enhancement of the thermal stability of amino-POSS-NC hybrid materials. In addition, tensile strengths and Young's moduli of amino-POSS-NC hybrid materials were increased gradually with the amino-POSS content in the uniaxial tensile tests. All these results show that the proposed modification of nitrocellulose improves the safety of manufacture and use of this material.

Kinetic analysis of polydicyclopentadiene oxidation

The in situ thermal oxidation of thin unstabilized polydicyclopentadiene was studied by TGA to monitor mass gain, and DSC to characterize hydroperoxides concentration. Results were discussed using kinetic analysis, which allowed the estimation of activation energies for key reactions of the oxidation process. Activation energy for termination was shown to be higher than in hydrocarbon liquids, which was discussed from the theory of diffusion controlled reactions, and a possible link with local motions associated with sub-glassy transition. Activation energy of thermal decomposition of hydroperoxides was found lower than for model hydroperoxides, suggesting an accelerating effect of organometallic catalysts. Despite those two results that indicate a poor thermal stability of thin pDCPD films, measurements of oxygen diffusivity at several temperatures show that oxidation remains confined in a relatively thin surface layer which would allow the pDCPD properties to be preserved.

Geometrical structures, thermal properties and spectroscopic studies of Schiff base complexes: Correlation between ionic radius of metal complexes and DNA binding

A novel series of transition metal complexes of Cu(II), Co(II), Ni(II), Mn(II) and Cd(II) were prepared from Schiff base derived from 4-aminoantipyrine and quinoline-2-carbaldehyde to give 4-((quinolin-2-yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (QMP). The structural features were derived from elemental analysis, mass spectroscopy, X-ray, IR, 1H NMR, electronic spectra, molar conductance magnetic susceptibility and thermogravimetric studies. On the basis of the studies the coordination sites were proven to be through oxygen of the ring CO and nitrogen of the azomethine (HCN) group. The thermodynamic parameters were calculated using Coats–Redfern and Horowitz–Metzger methods. From the values of the thermal activation energy of decomposition (Ea) of Schiff base (QMP) and its metal complexes (1–5), it was found that the Ea value for the complex (3) is higher compared to the other complexes. The Gibbs free energy of decomposition (ΔG⁎) for Schiff base (QMP) and its metal complexes is positive value which indicates that the processes are non-spontaneous. The interaction between Schiff base (QMP) and its metal complexes and calf thymus DNA shows hypochromism effect coupled with obvious bathochromic shift. From the values of binding constant (Kb) we noted that the highest value of Kb is belong complex (3) and these indicated that the Ni(II) is highly binding with CT-DNA and these due to the lower ionic radius. Furthermore, quantum chemical parameters of Schiff base and its complexes were calculated and discussed. The antimicrobial activity of Schiff base (QMP) and its M(II) complexes were studied and compared with the standard antibacterial and antifungal drugs.

Influence of acid and alkali pre-treatments on thermal degradation behaviour of polyisocyanurate foam and its carbon morphology

The thermal degradation of polyisocyanurate foam samples were studied by TG/DTA, FTIR, and SEM. All samples with different isocyanate index (NCO/OH = 100, 200, 300) were pre-treated by H2SO4, K2CO3, and NaOH before heating. The measurements of DTG and DTA presented corresponding variability for different acidic and alkaline treatments. The activation energy of thermal decomposition was calculated based on kinetic reaction evaluation. The pronounced polyol and isocyanate regenerations were observed over degradation. Further FTIR measurements at elevated temperatures suggested the possibility of acidic hydrogen bonding catalyzation and alkaline reversible amide regeneration during degradation by chemical treatments. The morphology and growth mechanism of localized corrosion and microcrystallization were characterized based on SEM micrographs.

Fast pyrolysis of sweet sorghum bagasse in a fluidized bed reactor: Product characterization and comparison with vapors generated in analytical pyrolysis

Lignocellulosic biomass can be used as an alternative for the production of fuels and chemical feedstocks using thermochemical conversion processes, such as pyrolysis. This study aims to perform the fast pyrolysis of sweet sorghum bagasse in a fluidized bed unit, comparing the results obtained with the products from analytical pyrolysis. Furthermore, the apparent activation energy of thermal decomposition of biomass was determined using two global reaction models. The estimated values of apparent activation energy ranged from 106.2 to 203.3 kJ/mol. The main compounds identified in the vapors generated in the analytical pyrolysis were acetic acid, isoprene, methyl pyruvate, furfural, 2,3-dihydrobenzofuran, 4-hydroxy-3-methylacetophenone and 5-hydroxymethylfurfural. In the bio-oil produced in the fluidized bed unit, the main compounds identified were benzene, acetic acid, isoprene, 3-methoxypropanal, toluene, furfural, 1,1-dimethoxycyclohexane and phenol. The difference between the identified compounds could be attributed to the solvent used, the efficiency of the condensation system, the occurrence of secondary reactions during the fast pyrolysis process in the fluidized bed reactor and the polymerization after the condensation of the vapors produced.

Characterization and Thermal Stability of Acetylated Slicewood Production by Alkali-Catalyzed Esterification.

This study was compared and characterized two different alkali (potassium carbonate (PC) and potassium acetate (PA))-catalyzed acetylations of slicewood with vinyl acetate (VA) by a vapor phase reaction. The results revealed that the esterification reaction between VA and the hydroxyl groups of slicewood could be improved by using PC or PA as a catalyst. Additionally, a significant weight percent gain was obtained after VA acetylation with 5% of catalyst. Furthermore, the reactivity of the cellulose hydroxyl groups for VA acetylation was more pronounced at the C2 reactive site compared to acetylation with acetic anhydride. On the other hand, the apparent activation energy of thermal decomposition between 10% and 70% conversion is 174–183, 194–200, and 183–186 kJ/mol for unmodified slicewood and VA-acetylated slicewood with PC and PA, respectively. Accordingly, the thermal stability of the slicewood could be effectively enhanced by VA acetylation, especially for using the PC as a catalyst.

Natural resistance of raw cotton fiber to heat evidenced by the suppressed depolymerization of cellulose

Mechanically purified raw cotton fiber finds a growing range of applications in support of environmental sustainability, but its unique thermal stability, which is important in processes and utilization, is little known. This study shows that, at low temperatures (<300 °C), the accelerated dehydration of cellulose was distinct in the pyrolysis of raw cotton. Compared with scoured cotton, raw cotton exhibited an intensive accumulation of dehydrocellulose in solid products, enhanced evolution of water and carbon dioxide, and increased formation of char. The amount of the crystalline region degraded together with the amorphous region was increased in raw cotton. The activation energy of thermal decomposition for raw cotton (124 kJ/mol) determined under isothermal conditions at 200–300 °C was lower than that for scoured cotton (202 kJ/mol). Such catalyzed low-temperature thermal reactions suppressed the depolymerization of cellulose at high temperatures, which produces highly volatile levoglucosan. The levoglucosan detected in raw cotton using Py-GC/MS was two orders of magnitude less abundant than that detected in scoured cotton.