Non-isothermal Thermogravimetric Analysis Research Articles

Comparative study on pyrolysis characteristics and kinetics of oleaginous yeast and algae

The pyrolysis processes of oleaginous yeast and algae were studied and compared using a non-isothermal thermogravimetric analyzer at heating rates of 10–50 °C/min, and the most probable mechanism function and kinetic analyses of the main stage of pyrolysis were carried out by the Popuse method, Starink method, and Fridemen method. The main pyrolysis stage of the samples could be described by the Jander equation and Z–L–T equation and the activation energy of the three biomass was 108–117, 107–121 and 93–108 kJ/mol, respectively. For the three kinds of biomass, the DTG curves were divided based on the four pseudo-components by performing Gaussian fitting which are carbohydrates, proteins, lipids, others, and the weight coefficients of them could be identified. The activation energy of each pseudo-component was obtained in the range of 58.36–140.44 kJ/mol by the Kissinger method. The four-pseudo-component model based on Gaussian fitting provides effective data for the design of oleaginous yeast and algae thermal decomposition systems and the kinetic analysis of the pyrolysis process.

Properties of flotation residual carbon from gasification fine slag

The purpose of this study was to upgrade the fine slag by a froth flotation kinetics process in order to separate and recycle the residual carbon and tailing ash simultaneously. Fine slag, a kind of solid waste, was obtained from an entrained-flow gasification unit. The carbon content of flotation residual carbon was 64.47% by weight, which is about 3 times of that of gasification fine slag. The results show that when the particle size of fractions is higher (>75 μm), the carbon content is higher, even >80%. The fine slag and flotation residual carbon were characterized by elemental and proximate analysis in order to compare the H/C, O/C, and element characteristics. The morphology of fine slag was determined by scanning electron microscopy (SEM). It was found the grinding time of 6 min can meet the crushing requirements of large particle flotation residual carbon. The grinding volume ratio of >80% is <75 μm sieving, which is a benefit for further fuel utilization. The non-isothermal thermo-gravimetric analysis (TGA) and loss on ignition (LOI) at 450 °C & 550 °C methods were used to analyze and compare the oxidation of residual carbon. In conclusion, LOI at 550 °C and non-isothermal TGA approaches can be used to determine the carbon content, which provides a reference for the determining LOI of waste-derived fuels in industries.

Nano-silica-based urea–formaldehyde composite with some derivates of coumarin as formaldehyde scavenger: hydrolytical and thermal stability

The hydrolytic stability of two nano-SiO2-based UF composites with derivates of coumarin (names as K-1 and K-2) was investigated. K-1 is 3-nitro-4-(p-tolylamino)-2H-chromen-2-one and K-2: 4-((3-nitro-2-oxo-2H-chromen-4-yl)amino)benzenesulfonamide. Two types of nano-silica-based urea–formaldehyde (UF), composite materials with a formaldehyde-to-urea (F/U) ratio of 0.8, were synthesized (UF/K-1/SiO2, and UF/K-2/SiO2). The hydrolytic stability of modified UF composite was determined by measuring the mass loss and liberated formaldehyde concentration of modified UF composite after acid hydrolysis. Obtained results showed that the hydrolytic stability of modified resins with derivates of coumarin was enhanced. The formaldehyde emission of modified UF/K-1/SiO2 composite is lower compared with UF/K-2/SiO2 composite. The thermal behavior of materials was studied by non-isothermal thermo-gravimetric analysis and differential thermal gravimetry supported by data from ATR-IR spectroscopy. The shift of temperature values for selected mass losses (T5%) to a high temperature indicates the increase in thermal stability of samples based on UF resin modified with K-2.

Structural characteristics and flammability of low-order coal pyrolysis semi-coke

This study focused on the effects of pyrolysis temperature on the structural characteristics and combustion properties of low rank coal. The combustion performance of semi-coke at different temperatures was studied by using low-temperature pyrolysis technology and non-isothermal thermogravimetric analysis. The variation of functional groups and carbon structure was quantitatively analyzed. The results show that the temperature has a significant effect on the semi-coke structure and flammability. In the middle and low temperature pyrolysis stage, the removal of water, volatile matter and functional groups is mainly carried out, and the degree of condensation and graphitization of carbon atoms is not obvious. The semi-coke performance with a pyrolysis temperature of 1023K is close to that of anthracite. The pyrolysis process is accompanied by the destruction of carbonaceous and the formation of mesopores, which affects the combustion performance. As the temperature increases, the flammability of the semi-coke is lowered, and the chemical structure of the semi-coke is a major factor affecting the flammability. The method of Coast-Redfern integration was used to calculate the kinetic parameters of the semi-coke. As the pyrolysis temperature increases, the activation energy of the combustion reaction increases, which is consistent with the trend of combustion performance change.

The kinetics of thermal decomposition of 1-alkyl-3-methylimidazolium chloride ionic liquids under isothermal and non-isothermal conditions

The thermal stability and decomposition kinetics of a series of 1-alkyl-3-methylimidazolium chloride ionic liquids with different alkyl chain lengths (ethyl, propyl, butyl, hexyl, and decyl) were investigated with isothermal and non-isothermal thermogravimetric analysis. Isothermal experiments were conducted at 100, 125, 150, 175, 200, and 225 °C in nitrogen atmosphere. Non-isothermal experiments were conducted from 25−650 °C with heating rates of 5, 10, 15, and 20 ℃/min. Under both heating modes, the ionic liquids with the longer alkyl chains were found to display lower thermal stability. The activation energies Ea determined from isothermal analysis ranged from 115-120 kJ/mol, except for the ionic liquid with the decyl chain, for which the value was higher (157 kJ/mol). The Ea determined by non-isothermal analysis were similar to the isothermal values for the ionic liquids with the ethyl and decyl chains, higher (144-154 kJ/mol) for the ionic liquids with the propyl and butyl chains, and lower (98 kJ/mol) for the ionic liquid with the hexyl chain. The pre-exponential factors ln(A) from isothermal analyses resulted in values in the range 25–29, which did not vary with reaction model. Non-isothermal analyses resulted in ln(A) values in the range 24–38, which were likewise not sensitive to reaction model. Among the models evaluated, the 3-dimensional reaction model was found to best represent both the isothermal and the non-isothermal data. No clear relationships were found between the alkyl chain length and the kinetic parameters.

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

Charcoal production from waste pequi seeds for heat and power generation

Many specialized technologies are available to convert waste biomass into secondary products that have a higher value and are more convenient to process than the original feedstock. This study evaluated the potential of waste pequi seeds to produce high-quality charcoal for subsequent gasification into low-tar producer gas for heat engine applications. We focused on the characterization of pequi seeds, the derived charcoal, and the collected bio-oil from slow pyrolysis conversion of the feedstock. Thermodynamic equilibrium calculations were conducted to assess gasification performance of the parent biomass and its charcoal. We also investigated the thermal degradation kinetics of pequi seeds through non-isothermal thermogravimetric analysis. Finally, a two-step energy-extraction analysis was performed for the carbonization of the parent biomass and further utilization of its charcoal in an integrated gasification gas-engine cycle. Slow pyrolysis of pequi seeds (2 °C min−1, 430 °C) produced up to 40% of high-grade charcoal with 60% fixed carbon, 43% of bio-oil, and 16% of light gases. The overall energy extraction efficiency was estimated as 61%, based on the higher heating value of wet pequi seeds. The investigation confirmed that waste pequi seeds could be considered a promising renewable energy source for combined heat and power generation for the Brazilian agro-food industry.

Study on co-combustion characteristics of hydrochar and anthracite coal

Non-isothermal thermogravimetric analysis was employed to study the combustion reaction behavior of three different hydrochars and one anthracite in the paper. The particle size distribution analysis, scanning electron microscopy, specific surface area and Raman spectroscopy were also used to observe and characterize physiochemical properties. The Coats-Redfern kinetic model method was used to calculate the activation energy of different combustion reactions. The results showed that the combustion of fiber reject had a more effective combustion property than the other two hydrochars. The main reason was that fiber reject had higher specific surface area and lower carbon microcrystalline structure. Meanwhile, the co-combustion of different hydrochars with coal had similar combustion trends, and with the increase of hydrochar proportion, the combustion rate was higher. The results of the kinetic calculation correspond to this conclusion. It can be found that as the proportion of the three hydrochar increased, the activation energy of two stages gradually decreased.

Kinetics of microwave radiation pulverized coal combustion based on non-isothermal thermogravimetric analysis

ABSTRACT The combustion characteristics of Yangquan (YQ) and Yungang (YG) coal samples before and after exposure to microwave radiation were studied using the non-isothermal thermogravimetric method, and the combustion rules of pulverized coal before and after microwave exposure to radiation were investigated. The results show that after microwave modification the ignition temperature (T i), burnout temperature (T j) and the temperature of maximum combustion rate (T k) of coal sample were all reduced about 10-20°C and the burnout time was shortened by 1–2 min, indicating that the provided treatment effectively improved the combustion performance of the pulverized coal. The characteristic indices C and S of the modified coal samples increased at a high heating rate (20°C/min), which suggests that the microwave modification has a stronger effect on the combustion performance of coal samples at high heating rates. As per the FT-IR spectrum curve, the absorption peak intensity of the higher activity group in the coal sample increased significantly after microwave modification. A comprehensive VR model was employed to model the kinetics of the coal combustion process. The resultant model had a correlation coefficient (R 2) of above 0.999 and root means square error (RMSE) of less than 0.018%, which indicating that the combustion behavior of the pulverized coal can be well described using the VR model. The activation energies E 1 and E 2 of M-YQ and M-YG modified via microwave treatment were decreased by 3.12 kJ·mol−1, 1.02 kJ·mol−1, 4.55 kJ·mol−1, and 8.14 kJ·mol−1 respectively, which further demonstrates that the microwave radiation can effectively accelerate reaction rate of the coal combustion per unit time.

Modelling the chemical recycling of crosslinked poly (methyl methacrylate): Kinetics of depolymerisation

Whereas increasing plastic solid waste production constitutes one of the main challenges of modern society, mainly due to the lack of suitable recycling technologies, chemical recycling represents an attractive solution for the conversion of plastic solid waste into valuable chemical intermediates. Herein, a kinetic model for the pyrolysis of a dental industry waste, ethylene glycol dimethacrylate (EGDMA) crosslinked poly (methyl methacrylate) (PMMA), is presented for the first time. Kinetics parameters and their statistical significance have been estimated from eight non-isothermal thermogravimetric analysis (TGA) experiments with heating rates varying between 5 and 50 °C·min−1 by using nonlinear regression. Our analysis indicates that the mechanism of depolymerisation of EGDMA crosslinked PMMA is likely to involve a consecutive reaction pathway involving two steps. The developed kinetic model - containing five kinetic parameters only - was able to predict well all non-isothermal TGA runs, and was validated against isothermal TGA experiments at 400 °C.

Kinetic triplet of Colombian sawmill wastes using thermogravimetric analysis

The potential of sawmill wastes as a raw material in pyrolysis process is presented in this study. Non-isothermal thermogravimetric analysis (TGA and DTG) and isoconversional methods were employed to determine triplet kinetic (activation energy, reaction model and pre-exponential factor). Through TGA and DTG, the conversion degree is described as a function of temperature for five heating rates (10, 20, 30, 40 and 50o C/min) and four model-free methods (Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Friedman, and Vyazovkin) with temperatures ranging from 25 to 1000°C were employed. Isoconversional lines were built for every method at different isoconversional degrees α∈[0,1]. The activation energy E was found as a function of α in the interval χII=[0.2,0.7] where each isoconversional methods were in agreement and the estimated error was sufficiently small. Findings show the same activation energy profile independently of the isoconversional method. In particular the total variation of E in χII was as follows: 209.909–228.238 kJ/mol (FWO); 211.235–229.277 kJ/mol (KAS); 223.050–188.512 kJ/mol (Friedman), and 211.449 kJ/mol-229.512 kJ/mol (Vyazovkin). The reaction model of the process in χII matched with a two-dimensional diffusion (D2) by using a master-plot analysis. The calculated and reported parameters are fundamental information for the pyrolysis reactor design using Sawmill wastes as feedstock.

Heterogeneous reaction kinetics for oxidation and combustion of boron

Non-isothermal thermogravimetric (TG) analysis was used to study the oxidation kinetics for 95% pure amorphous boron powder. Commercial boron powders were pre-treated with acetonitrile and water to reduce the thickness of their initial hydrated oxide layer and to achieve a narrower particle size distribution. The samples were oxidized at different heating rates in an oxygen-argon gas mixture. Boron particles comprising aggregates of finer primary particles were modeled as spheres with porous shells and solid cores. Experimental TG traces were split among particles of different sizes. The split was based on the measured particle size distribution and accounted for the fraction of the measured mass gain assigned to different powder particle size bins using the core-shell particle model. Further, the reactive shell was assumed to consist of densely packed spherical primary particles. The reaction kinetics was quantified to obtain both activation energy and pre-factor describing oxidation of the primary particles. The early stage of oxidation is well described with the activation energy of 148 ± 6 kJ/mol. The oxidation rate of boron particle of any size can be obtained considering the rate of oxidation of the primary particle and the introduced core-shell particle structure. The obtained oxidation model was extrapolated to the range of temperatures typical of boron combustion. A change in the particle morphology occurring when boron melts and the aggregates of primary particles coalesce into a single droplet was accounted for. Burn times predicted at different temperatures were close to those measured for boron particles burning in room air. Comparisons suggest that the particle surface temperature varies in the range of 3500–4500 K, approaching boron boiling point. It is concluded that the same heterogeneous kinetics governs both low-temperature oxidation of boron when the oxide film thickness is small and its full-fledged combustion occurring at much higher temperatures.

The interaction effect of catalyst and ash on diesel soot oxidation by thermogravimetric analysis

The interaction effect of catalyst and ash on commercial carbon black (Printex U, PU) oxidation is investigated using non-isothermal thermogravimetric analysis (TGA). The presence of commercial catalysts TiO2 and CeO2 decrease the start, peak and end temperatures of soot oxidation, and increase the comprehensive oxidation index. Compared with PU/TiO2 mixture, PU/CeO2 mixture has lower activation energy and higher comprehensive oxidation index because CeO2 has the higher oxygen storage and better active oxygen generation capacities. The impact of CeO2 is shown to be the most significant at 1:5 wt ratio between soot and catalyst among various ratios. Compared with pure PU, the comprehensive oxidation index for 1:5 wt ratio of PU/CeO2 increases from 0.97*10−7 %2min−2 °C−3 to 1.58*10−7 %2min−2 °C−3. The comprehensive oxidation index can further increase by adding ashes. Compared with PU/CeO2/Al2O3, PU/CeO2/MgO and PU/CeO2/CaSO4 mixtures, PU/CeO2/ZnO mixture has the maximum comprehensive oxidation index. The most significant impact of potential ash on PU/CeO2 is observed with 1:5:5 wt ratio of PU/CeO2/ZnO among soot, catalyst and ash, which has the maximum comprehensive oxidation index 2.41*10−7 %2min−2 °C−3. The comprehensive oxidation index of 1:5:5 wt ratio of PU/CeO2/ZnO increases by 148% compared with pure PU. This work is beneficial to demonstrate the interaction mechanism of the catalyst and ash on soot oxidation process under O2/N2 atmosphere.

Kinetic mechanism of magnesium production by silicothermy in argon flowing

The experiment of magnesium production was carried out by non-isothermal thermogravimetric analysis (TGA) technique under the conditions, where the reaction equilibrium was shifted by entraining the magnesium vapor into argon. The thermogravimetric (TG) of pellets made of calcined dolomite, ferrosilicon and fluorite were determined at the heating rate of 10, 15 20 and 25 ℃ min−1 in argon flowing and high temperature, respectively. Then on the basis of model-free and model-based analysis, the reaction kinetics were conducted. The results showed that the model that gave the best statistical fit of experimental data is two consecutives probably. When conversion α was less than 48.6 %, the reaction mechanism was determined by the N-Dimensional nucleation and growth, otherwise, it was the Nth order formal chemical reaction. And the conversion rate of every step could be described by independent kinetic equation and kinetic parameters. Our research will lay the research basis for the development of a new non-vacuum magnesium metallurgy technology with a lower energy consumption and more efficient.

Solvatochromism and Selective Sorption of Volatile Organic Solvents in Pyridylbenzoate Metal-Organic Frameworks

Using cobalt(II) as a metal centre with different solvent systems afforded the crystallization of isomorphous metal-organic frameworks {[Co(34pba)(44pba)]·DMF}n (1) and {[Co(34pba)(44pba)]·(C3H6O)}n (2) from mixed 4-(4-pyridyl)benzoate (44pba) and 3-(4-pyridyl)benzoate (34pba) ligands. Zinc(II) under the same reaction conditions that led to the formation of 1 formed an isostructural {[Zn(34pba)(44pba)]·DMF}n framework (3). Crystal structures of all three MOFs were elucidated and their thermal stabilities were determined. The frameworks of 1, 2, and 3 were activated under vacuum to form the desolvated forms 1d, 2d, and 3d, respectively. PXRD results showed that 1d and 2d were identical, consequently, 1d and 3d were then investigated for sorption of volatile organic compounds (VOCs) containing either chloro or amine moieties. Thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR) were used to determine the sorption capacity and selectivity for the VOCs. Some sorption products of 1d with amines became amorphous, but the crystalline framework could be recovered on desorption of the amines. Investigation of the sorption of water (H2O) and ammonia (NH3) in 1d gave rise to new phases identifiable by means of a colour change (solvatochromism). The kinetics of desorption of DMF, water and ammonia from frameworks 1d and 3d were studied using non-isothermal TGA. Activation energies for both cobalt(II) and zinc(II) frameworks are in the order NH3 &lt; H2O &lt; DMF, with values for the 1d analogue always higher than those for 3d.

Evaluation of thermal decomposition characteristics and kinetic parameters of melina wood

The evaluation of thermal decomposition characteristics and kinetic parameters of melina wood were investigated. Proximate, ultimate and calorific value analyses of the melina wood were carried out based on standards. Melina wood was subjected to multiple heating rates (5–15 °C/min) in thermogravimetric experiment. Two prominent isoconversional methods (Flynn-Wall-Ozawa and Starink) were adopted to obtain kinetic parameters from the non-isothermal thermogravimetric analysis curves. The ash, volatile matter and carbon contents of the melina were 2.15, 81.42 and 47.05%, respectively, while the calorific value was 18.72 MJ/kg. The main devolatilization stage of melina ranged from 220 °C to 350 °C while 80% weight loss was obtained below 400 °C. The activation energy varied between approximately 15 and 162 kJ/mol as a function of degree of conversion. The pre-exponential factors varied between 1.60E + 2 and 5.67 E + 12/min. The decomposition kinetic mechanism of melina is concluded to be a multi-step reaction.

Thermal degradation study of waste polyethylene terephthalate (PET) under inert and oxidative environments

Thermogravimetric analysis (TGA) of polyethylene terephthalate obtained from waste soft drink bottles (PET-SDB) was carried out under inert (nitrogen) as well as reactive (synthetic air) environments to evaluate the degradation behaviour and degradation kinetics. Non-isothermal TGA experiments at heating rates of 5, 10, 20, 40 and 50 °C/min were performed and the kinetic parameters such as activation energy (Eα) and pre-exponential factor (Aα) were determined at various extent of conversions using advance isoconversional (AIC) method. Criados’ master plot technique established F1 (first order) as possible reaction model (fα) for both inert and oxygenated non-isothermal TGA data. Under inert (N2) environment a residue accumulation of around 20% was observed whereas complete conversion of PET-SDB occurred in oxygenated environment. The activation energy values were found in the range of 203–355 kJ/mol and 145–218 kJ/mol for inert and oxygenated environment respectively. Isothermal TGA data at various temperatures were analysed for the estimation of kinetic parameters. In the considered range of conversions, the range of activation energy obtained for multiple isothermal TGA data was found in the range of 196–217 kJ/mol.

Kinetics of catalytic biomass pyrolysis using Ni-based functional materials

The pyrolysis behaviors of three types of biomass (cellulose, sawdust and straw) in three cases (no catalyst, Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4) were investigated by non-isothermal thermogravimetric analysis. The non-isothermal pyrolysis was implemented with four different heating rates: 20, 30, 40 and 50 °C/min and the yield rates of the produced gases were measured by TG-MS. For kinetic analysis, the activation energy was obtained using four isoconversional analysis methods (Flynn-Wall-Ozawa (FWO) method, Kissinger-Akahira-Sunose (KAS) method, Starink method, and the Miura distributed activation energy model (DAEM)). Ni-CaO-Ca2SiO4 and Ni-Ca2SiO4 was found to intensify the decomposition of biomass to produce more H2 and CO. The correlation R2, of all fitting lines in all cases, was above 0.9 which demonstrated that FWO, KAS, Starink methods and DAEM were suitable for calculating the activation energy of the biomass catalytic pyrolysis. Ni-CaO-Ca2SiO4 showed the obvious catalytic effects in the decrease of activation energy of biomass pyrolysis to produce additional H2 and CO from the breakage of light organic molecules.

Parametrization of a Modified Friedman Kinetic Method to Assess Vine Wood Pyrolysis Using Thermogravimetric Analysis

Common kinetic parameters were obtained for leached and non-leached samples of vine wood biomass. Both samples were considered to have different proportions of cellulose, hemicellulose, and lignin compositions as a result of the leaching process. The two samples were analyzed in terms of pyrolysis kinetic parameters using non-isothermal thermogravimetric analysis. Furthermore, the classic Friedman isoconversional method, a deconvolution procedure using the Fraser–Suzuki function, and a modified Friedman method from a previous study on the delay in conversion degree were satisfactorily applied. The observed difference when the deconvolution technique was applied suggests that the classic Friedman method is not adequate for studying the pyrolysis of individual vine wood biomass components. However, this issue was solved by studying the delay in conversion degree of both biomasses and calculating the kinetic parameters using the resulting information. This procedure was found to be useful for studying and comparing the kinetics of heterogeneous biomasses and has a sound scientific explanation, making this research a basis for future similar studies.

Investigating the effect of integrated CO2 and H2O on the reactivity and kinetics of biomass pellets oxy-steam combustion using new double parallel volumetric model (DVM)

Thermal characteristics and kinetic parameters of rice straw (RS) and sawdust (SD) raw materials were investigated under an oxidizing atmosphere using a non-isothermal thermogravimetric analysis (TGA). The effect of H2O and CO2 on the oxy-steam combustion was studied by performing the TGA experiments using a mixture of (O2/CO2/H2O/N2) at different compositions. Kinetic parameters were determined using a volumetric model (VM), random pore model (RPM), double parallel random pore model (DRPM), mixed volumetric random pore model (MVRPM) and a new proposed double parallel volumetric model (DVM). The good fit between the experimental and modeled data was obtained from the parallel and mixed models results when the fractional conversion was used in these models. While the models’ solutions didn’t fit with the experimental results when they were solved based on the conversion rate. The new proposed DVM model gave the best fit with experimental conversion (α). The ignition delayed at high concentration of H2O due to the highest specific heat of H2O that lowered the temperature of the fuel particles. The activation energy and the frequency factor of RS were lower than that of SD. The char conversion rate of SD exceeded that of RS.