Kissenger-Akahira-Sunose Research Articles

Bioenergy potential of Wolffia arrhiza appraised through pyrolysis, kinetics, thermodynamics parameters and TG-FTIR-MS study of the evolved gases

This study evaluated the bioenergy potential of Wolffia arrhiza via pyrolysis. The biomass was collected from the pond receiving city wastewater. Oven dried powdered biomass was exposed to thermal degradation at three heating rates (10, 30 and 50° C min−1) using Thermogravimetry–Differential Scanning Calorimetry analyzer in an inert environment. Data obtained were subjected to the isoconversional models of Kissenger-Akahira-Sunose (KSA) and Flynn–Wall–Ozawa (FWO) to elucidate the reaction chemistry. Kinetic parameters including, Ea (136–172 kJmol−1) and Gibb’s free energy (171 kJmol−1) showed the remarkable bioenergy potential of the biomass. The average enthalpies indicated that the product formation is favored during pyrolysis. Advanced coupled TG-FTIR-MS analyses showed the evolved gases to contain the compounds containing CO functional groups (aldehydes, ketones), aromatic and aliphatic hydrocarbons as major pyrolytic products. This low-cost abundant biomass may be used to produce energy and chemicals in a cost-efficient and environmentally friendly way.

The effects of temperature and color value on hydrochars’ properties in hydrothermal carbonization

In order to investigate the influence of hydrothermal carbonization (HTC) on the properties of the hydrochars, sawdust with a particle size below 0.45mm was treated in an autoclave at 200–260°C. The physical and chemical characteristics of products were studied, including proximate analysis, elemental composition, fiber content, surface area, bulk density, energy yield, color value, combustion activities and pyrolysis kinetics, etc. It showed that the color of hydrochars turned blacker, greener, and bluer after HTC. The ash, carbon, hydrogen and lignin contents showed a good correlation (R2>0.96) with color coordinates. The decrement in stage 1 and increment in stage 2 of temperature intervals were attributed to the volatile matters removal and fixed carbon accumulation, improving the stability and safety of hydrochars combustion. As shown by the Kissenger–Akahira–Sunose (KAS) and Coats–Redfern calculations, the HTC process can also make the pyrolysis more stable.

Isoconversional kinetics and characteristics of combustion on hydrothermally treated biomass

Pine sawdust and its resulting hydrochars hydrothermally produced at different time were characterized by scanning electron microscope and Fourier transform infrared spectroscopy to indicate the transformation in their morphologies and chemical structure, respectively. Afterwards, a comparative study in relation to the thermal behavior and combustion characteristics for the pine sawdust and the hydrochars was investigated. The relationship between the activation energy and various conversion rates of pine sawdust and hydrochars heated at various heating rates of 10, 20 and 30 °C/min were evaluated by the methods of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The results obtained from the two methods revealed that the activation energies of hydrochars fluctuate within a narrow range when the conversion rate is 0–0.55 and then decrease drastically at the conversion rate range of 0.55–0.95, due to the decomposition of relative reactive compounds. In comparison of the two methods, the average activation energies of hydrochars obtained at 6 h and 12 h using FWO method are 112.63 and 82.83 kJ/mol, respectively, larger than 107.70 and 76.30 kJ/mol using KAS method.

Pyrolysis and kinetic analyses of Camel grass (Cymbopogon schoenanthus) for bioenergy

The aim of this work was to study the thermal degradation of grass (Cymbopogon schoenanthus) under an inert environment at three heating rates, including 10, 30, and 50°Cmin−1 in order to evaluate its bioenergy potential. Pyrolysis experiments were performed in a simultaneous Thermogravimetry–Differential Scanning Calorimetry analyzer. Thermal data were used to analyze kinetic parameters through isoconversional models of Flynn-Wall-Ozawa (FWO) and Kissenger-Akahira-Sunose (KSA) methods. The pre-exponential factors values have shown the reaction to follow first order kinetics. Activation energy values were shown to be 84–193 and 96–192kJmol−1 as calculated by KSA and FWO methods, respectively. Differences between activation energy and enthalpy of reaction values (∼5 to 6kJmol−1) showed product formation is favorable. The Gibb’s free energy (173–177kJmol−1) and High Heating Value (15.00MJkg−1) have shown the considerable bioenergy potential of this low-cost biomass.

The investigations of thermal behavior, kinetic analysis, and biological activity of trinuclear complexes prepared ONNO-type Schiff bases with nitrito and nitrato μ-bridges

By using bis-N,N′(salicylidene)-1,3-diaminopropane and reduced form of this ligand bis-N,N′(2-hydroxybenzylidene)-1,3-diaminopropane, we prepared eight trinuclear complexes in the core form of NiII–NiII–NiII and NiII–CuII–NiII. Complexes have been characterized with element analysis, IR spectroscopy and NMR spectroscopy methods and also investigated with Thermogravimetry (TG). It was observed that thermal characteristics of the complexes prepared by the reduced form of Schiff base are different from complexes prepared by the Schiff base. According to TG, two thermal reactions between 120 and 180 °C endothermic separation of coordinative dimethylformamide molecules and then around 300 °C exothermic decomposition of molecule were observed for Schiff base-prepared complexes. On the other hand, the complexes resulted from reduced Schiff base reactions were shown decomposed around 250–270 °C by exothermic thermal reaction. Kinetic parameters of decompositions were determined by isothermal and non-isothermal kinetic methods, Coats–Redfern (CR), Ozawa, Ozawa–Flynn–Wall (OFW) and Kissenger–Akahira–Sunose (KAS). Departing from these values, thermodynamic parameters were calculated and the results were interpreted. It was concluded that the complexes prepared with reduced Schiff bases are more strained structures. Biological activities of these complexes were also inspected, and antibacterial and antifungal activities were tested against four different bacterial strains (E. coli, P. aureginosa, S. aureus and E. feacalis) and a fungus species (C. albicans).

Kinetic analyses and pyrolytic behavior of Para grass (Urochloa mutica) for its bioenergy potential

The biomass of Urochloa mutica was subjected to thermal degradation analyses to understand its pyrolytic behavior for bioenergy production. Thermal degradation experiments were performed at three different heating rates, 10, 30 and 50°Cmin−1 using simultaneous thermogravimetric-differential scanning calorimetric analyzer, under an inert environment. The kinetic analyses were performed using isoconversional models of Kissenger-Akahira-Sunose (KAS) and Flynn–Wall–Ozawa (FWO). The high heating value was calculated as 15.04MJmol−1. The activation energy (E) values were shown to be ranging from 103 through 233 kJmol−1. Pre-exponential factors (A) indicated the reaction to follow first order kinetics. Gibbs free energy (ΔG) was measured to be ranging from 169 to 173kJmol−1 and 168 to 172kJmol−1, calculated by KAS and FWO methods, respectively. We have shown that Para grass biomass has considerable bioenergy potential comparable to established bioenergy crops such as switchgrass and miscanthus.

Thermogravimetric characteristics and kinetics analysis of oil cake and torrefied biomass blends

The pyrolysis characteristics and kinetics of the blends produced from the mixture of torrefied camphorwood and caster bean cake (CAS) were determined by thermogravimetric analysis. Kissenger–Akahira–Sunose (KAS) and Coats–Redferm methods were applied for kinetic analysis. The results show that torrefaction can increase the maximum decomposition rate and smooth the pyrolysis reaction at 250–330°C in the differential thermogravimetry (DTG) curves, and the additive of CAS can reduce the high maximum decomposition rate caused by torrefaction. The kinetic results suggest that the activation energy can be enhanced by torrefaction, while this can be lowered by the additive of CAS. It was found that the activation energy dropped dramatically for CAM torrefied at 300°C by Coats–Redferm method, whereas KAS method showed the contrary trend. The pre-exponential factors by Coats–Redferm method were decreased by the processes of torrefaction and co-pelletization with CAS. In consideration of heating value and activation energy, 270°C torrefaction and 30% CAS is conservatively selected as the optimum condition.

The preparation and characterization of dichlorobispyridinecopper(II) complex and its intermediates

The dichlorobispyridinecopper(II) complex, [CuPy2Cl2], and its decomposition intermediates were synthesized and characterized by MALDI-TOF MS, far-IR, reflectance UV, atomic absorption spectroscopy techniques. The thermal decomposition reactions of the [CuPy2Cl2] were investigated by differential thermal analysis (DTA)/thermogravimetry (TG) combined system. The intermediates and the final products were analyzed by high-temperature X-ray powder diffraction (HT-XRD) technique. The XRD pattern of the complex indexed as [CuPy2Cl2] (PDF: 00-014-991) has a monoclinic crystal system, P21/n (14) space group with a = 16.9673 A, b = 8.5596 A, c = 3.8479 A; α = γ = 90.00°, β = 91.98°, V = 558.51 A3 and Z = 2.00. After comparison of thermogravimetric results of the [CuPy2Cl2], the decomposition mechanism was suggested. The intermediates were prepared separately at 217 and 245 °C temperatures which were chosen from TG curve by using a tube furnace under N2 atmosphere and characterized. The spectroscopic results reveal that the structure of the intermediates to be [CuPyCl2] and [CuPy2/3Cl2] formulas (hereafter abbreviated as 2 and 3, respectively). MALDI-TOF MS spectra of the 2 and 3 show [M+H]+ (m/z = 214.978) and [M−H]+ (m/z = 185.614), [M+C2H3O]+ (m/z = 221.002) molecular ion peaks which correspond to suggested structure for 2 and 3, respectively. Also, HT-XRD results revealed that the 2 and 3 are new phases and there is no any certain information of these phases in the literature. The values of the activation energy, E a, were calculated by model-free (Kissenger–Akahira–Sunose, Flyn–Wall–Ozawa) methods for all decomposition stages.

Crystallization kinetics of overlapping phases in Se70Te15Sb15 using isoconversional methods

The crystallization kinetics of Se70Te15Sb15 chalcogenide glass was studied by Differential Scanning Calorimetry (DSC) under non-isothermal conditions. This glass was found to have a double glass transition and double overlapped crystalline phases. The overlapped crystalline phases were successfully separated using the Gaussian fit model. The activation energy, Ec, and Avrami index, n, were determined by analyzing the data using the Matausita et. al. method. A strong heating rate depending on the activation energy for the two crystalline peaks was observed. The results indicated that the transformation from amorphous to crystalline phases is a complex process involving different mechanisms of nucleation and growth. The variation of activation energy with crystalline fraction was determined by Kissenger–Akahira–Sunose (KAS) method. The obtained results of directly fitting the experimental DSC data to the calculated DSC curves indicated that the crystallization process of Se70Te15Sb15 glass cannot be satisfactorily described by the Johnson–Mehl–Avrami (JMA) model. Simulation results indicated that the Sestak–Berggren (SB) model is more suitable to describe the crystallization process for the studied glass. The crystalline phases for the two events were identified by using x-ray diffraction (XRD) and scanning electron microscopy (SEM).

Thermal behaviour and kinetics of alga Polysiphonia elongata biomass during pyrolysis

The pyrolysis characteristics and kinetics of Polysiphonia elongata were investigated using a thermogravimetric analyzer. The main decomposition of samples occurred between 225°C and 485°C at heating rates of 5–40°C/min; owing to release of 78–82% of total volatiles. The heating rate effected pyrolysis characteristics such as maximum devolatilization rate and decomposition temperature. However, total volatile matter yield was not significantly affected by heating rate. The activation energy of pyrolysis reaction was calculated by model free Friedman and Kissenger–Akahira–Sunose methods and mean values were 116.23kJ/mol and 126.48kJ/mol, respectively. A variance in the activation energy with the proceeding conversions was observed for the models applied, which shows that the pyrolysis process was composed of multi-step kinetics. The Coats–Redfern method was used to determine pre-exponential factor and reaction order. The obtained parameters were used in simulation of pyrolysis process and results were in a good agreement with experimental data.

Thermal behavior and dehydroxylation kinetics of naturally occurring sepiolite and bentonite

Sepiolite and bentonite have a wide range of industrial applications based on their physicochemical properties such as surface area, thermal behavior, chemical composition, and mineralogic composition. The thermal behavior and kinetics of naturally occurring sepiolite and bentonite were determined in order to give an idea about the potential use of naturally occurring clay minerals in possible applications. Naturally occurring sepiolite and bentonite samples were heated to the temperature that was achieved at the end of the dehydroxylation process. Mineralogic and thermal characteristics of raw and heat treated samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption/desorption analyses. Changes in the structure following heat treatment were used for the evaluation of the dehydroxylation properties of the samples. The dehydroxylation properties of the minerals are strongly affected by the crystal structure. Kinetic analyses, which were related to the dehydroxylation of naturally occurring sepiolite and bentonite, were conducted using dynamic thermogravimetry/derivative thermogravimetry analysis under nitrogen atmosphere. Flynn–Wall–Ozawa, Kissenger–Akahira–Sunose, and Friedman isoconversional methods were used to determine the activation energies of the dehydroxylation reactions of the samples. The results indicate that the activation energy of naturally occurring sepiolite showed a little variation at a particular conversion rate (0.3–0.7), while the activation energy of naturally occurring bentonite showed a significant variation within the range of variation of the conversion rate. The present study shows that the dehydroxylation reactions of naturally occurring sepiolite and bentonite were single mechanism reaction and complex mechanism reaction, respectively.

An investigation of decomposition stages of a ruthenium polypridyl complex by non-isothermal methods

Thermal properties of [cis-(dithiocyanato)(4,5-diazafluoren-9-one)(4,4′-dicarboxy-2,2′-bipyridyl)ruthenium(II)], [Ru(L 1)(L 2)(NCS)2] (where the ligands L 1 = 4,5-diazafluoren-9-one, L 2 = 4,4′-dicarboxy-2,2′-bipyridyl) have been investigated by DTA/TG/DTG measurements under inert atmosphere in the temperature range of 30–1155 °C. The mass spectroscopy technique has been used to identify the products during pyrolytic decomposition. The pyrolytic final products have been analyzed by X-ray powder diffraction technique. A decomposition mechanism has been also suggested for the cis-[Ru(L 1)(L 2)(NCS)2] complex based on the results of thermogravimetrical and mass analysis. The values of the activation energy, E* have been obtained by using model-free Kissenger–Akahira–Sunose and Flyn–Wall–Ozawa non-isothermal methods for all decomposition stages. Thirteen kinetic model equations have been tested for selecting the best reaction models. The best model equations have been determined as A2, A3, D1, and D2 which correspond to nucleation and growth mechanism for A2 and A3 and diffusion mechanism for D1 and D2. The optimized average values of E* are 31.35, 58.48, 120.85, and 120.56 kJ mol−1 calculated by using the best model equations for four decomposition stages, respectively. Also, the average Arrhenius factor, A, has been obtained as 2.21, 2.61, 2.52, and 2.21 kJ mol−1 using the best model equation for four decomposition stages, respectively. The ΔH*, ΔS*, and ΔG* functions have been calculated using the optimized values.

Azomethine-based phenol polymer: Synthesis, characterization and thermal study

Azomethine-based phenol polymer, poly-2-{[(6-aminopyridin-2-yl)imino]methyl}-phenol (PAPIMP), was synthesized through the combination of condensation reaction and oxidative polymerization. Polymer isolated from aqueous solution was characterized by UV–vis, FT-IR, NMR and TG, SEC analysis. According to the SEC chromatograms, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of PAPIMP were determined to be 33,550, 78,900gmol−1 and 2.352, respectively. Also, optical band gaps (Eg) of APIMP and PAPIMP calculated from cyclic voltammetry (CV) measurements. Also, electrical conductivities of each component measured with four-point probe technique. TG analysis showed that PAPIMP was stable up to 300°C. The thermal decomposition kinetics of PAPIMP was investigated by means of thermogravimetric analysis in dynamic nitrogen atmosphere at four different heating rates: 5, 10, 15 and 20°Cmin−1. The apparent activation energies for thermal decomposition of PAPIMP were obtained by Tang, Flynn–Wall–Ozawa (FWO), Kissenger–Akahira–Sunose (KAS) and Coats–Redfern methods (CR) were 96.97, 105.33, 97.28 and 88.60kJmol−1, respectively; the mechanism function and pre-exponential factor were determined by master plots method. The most likely decomposition process was a Dn Deceleration type in terms of the Coats–Redfern and master plots results.

Non-isothermal degradation kinetics of poly (2,2′-dihydroxybiphenyl)

Catalytic oxidative polymerization of 2,2′-dihydroxybiphenyl (DHBP) was performed by using Schiff base polymer-Cu (II) complex and hydrogen peroxide as catalyst and oxidant, respectively. According to size exclusion chromatography (SEC) analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of poly (2,2′-dihydroxybiphenyl) (PDHBP) were found to be 37,500, 90,000 g mol−1 and 2.4, respectively. The thermal degradation kinetics was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at four different heating rates: 5, 10, 15 and 20 °C min−1. The derivative thermogravimetry curves of PDHBP showed that its thermal degradation process had one weight-loss step. The apparent activation energies of thermal decomposition for PDHBP as determined by Tang, Flynn–Wall–Ozawa (FWO), Kissenger–Akahira–Sunose (KAS), Coats–Redfern (CR) and Invariant kinetic parameter (IKP) methods were 109.1, 109.0, 110.0, 108.4 and 109.8 kJ mol−1, respectively. The mechanism function and pre-exponential factor were determined by master plots and Criado–Malek–Ortega method. The most likely decomposition process was a Dn Deceleration type in terms of the CR, master plots and Criado–Malek–Ortega results.

Kinetic of thermal degradation of poly(isobornyl methacrylate)

The kinetic of the thermal degradation of poly(isobornyl methacrylate) (PIBORNMA) was investigated by thermo gravimetric (TG) analysis at different heating rates. TG curves showed that the thermal decomposition of PIBORNMA occurred in one stage. The apparent activation energies of thermal decomposition of PIBORNMA was determined by Tang, Flynn-Wall-Ozawa (FWO), Kissenger–Akahira–Sunose (KAS) and Coats-Redfern methods and the values were 80.30, 84.69, 79.81 and 84.413 kJ/mol, respectively. The mechanism function and pre-exponential factor was determined by master plots method.

The decomposition kinetics of mechanically activated alunite ore in air atmosphere by thermogravimetry

The thermal decompositions of both non-activated and mechanically activated alunite ore have been studied by thermogravimetry (TG). The ore was activated mechanically in an attritor for 15 min and amorphisation in the structure was studied by X-ray diffraction analysis. It can be verified that alunite decomposes in two steps, which are dehydration and desulphation. It was also established that the mechanical activation affected especially on the temperature range of dehydration reaction. The activation energies of dehydration and desulphation reactions have been calculated from the thermogravimetric data at heating rates of 5, 10, 15 and 20 K min −1 involving isoconversional methods of Ozawa and Kissenger–Akahira–Sunose (KAS).

Mode II fatigue under a compressive stress field: a simplified model for rolling contact fatigue : Otsuka, A. and Aoyama, M. Mixed-Mode Fatigue and Fracture Mechanical Engineering Publications Limited, Northgate Ave, Bury St Edmunds, Suffolk IP32 6BW, UK, 1993, pp 49–60

This study evaluated the bioenergy potential of Wolffia arrhiza via pyrolysis. The biomass was collected from the pond receiving city wastewater. Oven dried powdered biomass was exposed to thermal degradation at three heating rates (10, 30 and 50° C min−1) using Thermogravimetry–Differential Scanning Calorimetry analyzer in an inert environment. Data obtained were subjected to the isoconversional models of Kissenger-Akahira-Sunose (KSA) and Flynn–Wall–Ozawa (FWO) to elucidate the reaction chemistry. Kinetic parameters including, Ea (136–172 kJmol−1) and Gibb’s free energy (171 kJmol−1) showed the remarkable bioenergy potential of the biomass. The average enthalpies indicated that the product formation is favored during pyrolysis. Advanced coupled TG-FTIR-MS analyses showed the evolved gases to contain the compounds containing CO functional groups (aldehydes, ketones), aromatic and aliphatic hydrocarbons as major pyrolytic products. This low-cost abundant biomass may be used to produce energy and chemicals in a cost-efficient and environmentally friendly way.