Popescu Method Research Articles

Detailed investigation on the oxidation behavior and kinetic triplet of tight oil via TG-DSC-PDSC analyses

It remains some barriers for continental tight oils to enhance oil recovery owing to low or ultra-low permeability in China. Whether low temperature combustion mode (or deflagration fracturing) could be employed to expand the fracture, is an interesting but debatable topic in consideration of the not well-understood oxidation behavior and kinetic mechanism for the tight oil. This study initiated a comprehensive characterization on the oxidation behavior and kinetic triplet for the Mahu tight oil via the combination of atmospheric and pressurized thermal analyses (TG/DTG, DSC/DDSC, PDSC) and unconventional Popescu method. Threshold, peak, and end temperatures were shifted to higher temperature ranges following lower cumulative heat emission (from 13.21 to 9.15 kJ·g−1) with the heating rate increment from 5 to 15 K·min−1. Inversely, a more thorough oxidation process with higher cumulative heat releases (8.69 kJ·g−1 for LTO, 4.48 kJ·g−1 for HTO) was presented under elevated pressure condition. In order to elucidate the latent reaction mechanism, seven sequential temperature subzones were divided to acquire the most probable mechanism function G(α) and corresponding kinetic parameters. The results indicated that, owing to the high reservoir pressure, generated enormous heat in LTO stage had a significant acceleration to initiate and sustain the low temperature combustion process, which in some degree was conducive to update and expand the understanding of the low temperature in-situ combustion mode of air injection in low permeability and tight oil reservoirs via fracturing reservoir matrix.

Non-isothermal kinetic analysis of metallised burden with a metallisation ratio of 70% in a CO2 atmosphere

ABSTRACT The utilisation of metallised burden in blast furnaces has become a trend in the iron and steel industry to reduce emissions. However, whether the metallised burden can be oxidised by CO2 remains unclear. In this study, the kinetics of metallised burden with a metallisation ratio of 70% in a CO2 atmosphere were analysed. The Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose (KAS), and Popescu methods were used to calculate the kinetic parameters. The results showed that the reaction was a multistep process, and the segmented temperature point was approximately 988 K. Furthermore, the results obtained by using the KAS method showed the best fit. In the early oxidation stage, the optimal mechanism model was A2/3, in which the integral form was , and the average values E and A were 59.22 kJ/mol and 44.28 s−1, respectively. In contrast, the optimal model was R3 in the later stage, in which the integral form was , and the average values E and A were 72.31 kJ/mol and 106.99 s−1, respectively.

Valorization of groundnut shell via pyrolysis: Product distribution, thermodynamic analysis, kinetic estimation, and artificial neural network modeling

Pyrolysis of agricultural biomass is a promising technique for producing renewable energy and effectively managing solid waste. In this study, groundnut shell (GNS) was processed at 500 °C in an inert gas atmosphere with a gas flow rate and a heating rate of 10 mL/min and 10 °C/min, respectively, in a custom-designed fluidized bed pyrolytic-reactor. Under optimal operating conditions, the GNS-derived pyrolytic-oil yield was 62.8 wt.%, with the corresponding biochar (19.5 wt.%) and biogas yields (17.7 wt.%). The GC-MS analysis of the GNS-based bio-oil confirmed the presence of (trifluoromethyl)pyridin-2-amine (18.814%), 2-Fluoroformyl-3,3,4,4-tetrafluoro-1,2-oxazetidine (16.23%), 5,7-dimethyl-1H-Indazole (11.613%), N-methyl-N-nitropropan-2-amine (6.5%) and butyl piperidino sulfone (5.668%) as major components, which are used as building blocks in the biofuel, pharmaceutical, and food industries. Furthermore, a 2 × 5 × 1 artificial neural network (ANN) architecture was developed to predict the decomposition behavior of GNS at heating rates of 5, 10, and 20 °C/min, while the thermodynamic and kinetic parameters were estimated using a non-isothermal model-free method. The Popescu method predicted activation energy (Ea) of GNS biomass ranging from 111 kJ/mol to 260 kJ/mol, with changes in enthalpy (ΔH), Gibbs-free energy (ΔG), and entropy (ΔS) ranging from 106 to 254 kJ/mol, 162–241 kJ/mol, and −0.0937 to 0.0598 kJ/mol/K, respectively. The extraction of high-quality precursors from GNS pyrolysis was demonstrated in this study, as well as the usefulness of the ANN technique for thermogravimetric analysis of biomass.

Investigation of Non-Isothermal Kinetics and Thermodynamic Parameters for the Pyrolysis of Different Date Palm Parts

Using the thermalgravimetric technique, we investigated the non-isothermal combustion kinetics of abundant and low-cost date palm wastes (leaflet, rachis, fibers, and their composite) as potential biomass energy sources. The kinetic and thermodynamic parameters were determined by Flynn–Wall–Ozawa (FWO), Kissinger–Akahila–Sunose (KAS), and Starink methods. Thermogravimetric analysis results showed a major peak for the degradation of volatiles between 127–138 °C with average percentage mass loss of 68.04 ± 1.5, 65.57 ± 0.6, 62.97 ± 5.5, and 59.26 ± 3.2, for rachis, composite, leaflet, and fibers, respectively. The FWO model showed the lowest activation energy, Eα, of 157 ± 25.6, 158 ± 25.7, 164 ± 40.1, and 169 ± 51.8 kJ mol−1 for the composite, rachis, leaflet, and fibers, respectively. The positive enthalpy values confirmed an endothermic pyrolysis reaction. For all models, a minimal difference of 4.40, 5.57, 6.55, and 7.51 kJ mol−1 between activation energy and enthalpy for rachis, fibers, composite, and leaflet ensued, respectively. The KAS model was best suited to describe chemical equilibrium with average ΔG values of 90.3 ± 28.8, 99.3 ± 34.9, 178.9 ± 27.3, and 186.5 ± 38.2 kJ mol−1 for rachis, fibers, composite, and leaflet, respectively. The reaction mechanism by the Malek and Popescu methods was ((g(α)=[−ln(1−α)]14) across the conversion range of 0.1–0.9 for all heating rates. The high energy content and volatile matter combined with low energy barriers make date palm waste a potential candidate in a biorefinery.

Thermal properties of drug polymorphs: A case study with felodipine form I and form IV

Thermal decomposition kinetics and solution thermodynamics of two polymorphs, felodipine form I and form IV, were investigated. The thermal decomposition kinetics of the polymorphs, containing thermal decomposing mechanism and the kinetic parameters were studied under non-isothermal conditions using Popescu method, and the shelf life was simply calculated. The results showed that nucleation and growth (n = 3/4) of Avremi–Erofeev equation is the most probable mechanism function for form I, and the integral form is G(α) = [−ln(1 − α)]3/4; while the Mample Powel law (n = 1) is the most probable mechanism function for form IV, corresponding to G(α) = α. Notably, the individual amorphous phases of crystal felodipine form I and IV were obtained after the heating–cooling cycle of DSC tests, which were identified by TMDSC and FT-IR measurements. As the interim products before the collapse, it can be inferred that different amorphous intermediates may be the determinant for different thermal decomposition mechanisms of crystal forms I and IV. The solubility data and solution thermodynamic parameters, including enthalpy, entropy and Gibbs free energy have also been calculated by Van’t Hoff equation in ethanol aqueous. The results illustrated the polymorphic pair is enantiotropic with the transition temperature of 322.23 K and the conversion is driven by entropy.

Comparative study on thermal behaviors between micrites and thrombolites using thermogravimetric analysis

Although micrites (abiotic limestone) and thrombolites (typical biotic limestone), according to the sedimentation and biological action, can be primarily distinguished from intuitively field observation and rock slices analysis. However, further analysis of thermal decomposition unique characteristics to distinguish them has rarely been reported. Here, the comparative studies of thermal decomposition behavior between micrites and thrombolites were carefully investigated using thermogravimetric analyzer in nitrogen atmosphere at multi-heating rates of 5, 10, 20 and 30 K min−1 from 323.15 to 1273.15 K. Moreover, the mineralogical compositions were both analyzed by powder X-ray diffraction followed by the results of calcite acting as the basic constituent for further verified. The kinetic model function and kinetic parameters were calculated by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Popescu methods, respectively. The results showed that the kinetic parameter activation energy (E) of thrombolites was obviously higher than that of micrites, which suggests the former have a higher crystallinity. In addition, the results of difference significance analysis showed extremely significant differences (P < 0.01) via statistical analysis using SPSS v19.0 for the E values between micrites and thrombolites calculated by different methods. These above results further confirmed that the thermal stability and crystallinity of thrombolites were obviously higher under the inducing effects by typical microorganisms. This provided very important useful information for understanding the mechanisms of abiotic and biotic limestones formed in nature; in particular, the thermal analysis of thrombolites maybe also provides an important guiding significance for both indoor and outdoor similar studies.

Specific kinetic triplet estimation of Tahe heavy oil oxidation reaction based on non-isothermal kinetic results

Although the oxidation mechanisms and kinetics characteristics of heavy oils have been involved in enormous studies, little attention is paid to the specific kinetics triplet and activation energy distribution in detailed temperature ranges. In this study, the non-isothermal oxidation kinetics characteristics of the Tahe heavy oil, including kinetics triplet, activation energy distribution (E-α curve) and thermodynamic parameters under specific temperature subzones, were investigated by thermo-analysis techniques and Popescu method. And it indicated that six sequential temperature subzones were identified with different mechanism function, G(α), and rate constant, k(T). Besides, it can be seen from the E-α curve that the first obvious increasing peak was attributed to the negative temperature gradient region (NTGR) and the second mild peak corresponded to the initiation stage of the combustion process, between which positive temperature coefficient and negative temperature coefficient zones were located at the valley. Additionally the calculated thermodynamic parameters (△S*, △H*, △G*) indicated that the non-isothermal oxidation process for Tahe heavy oil is the non-spontaneous reaction and needs heat to occur under atmospheric pressure.

Pyrolysis of high-ash sewage sludge: Thermo-kinetic study using TGA and artificial neural networks

Pyrolysis of high-ash sewage sludge (HASS) is a considered as an effective method and a promising way for energy production from solid waste of wastewater treatment facilities. The main purpose of this work is to build knowledge on pyrolysis mechanisms, kinetics, thermos-gravimetric analysis of high-ash (44.6%) sewage sludge using model-free methods & results validation with artificial neural network (ANN). TG-DTG curves at 5,10 and 20 °C/min showed the pyrolysis zone was divided into three zone. In kinetics, E values of models ranges are; Friedman (10.6–306.2 kJ/mol), FWO (45.6–231.7 kJ/mol), KAS (41.4–232.1 kJ/mol) and Popescu (44.1–241.1 kJ/mol) respectively. ΔH and ΔG values predicted by OFW, KAS and Popescu method are in good agreement and ranged from (41–236 kJ/mol) and 53–304 kJ/mol, respectively. Negative value of ΔS showed the non-spontaneity of the process. An artificial neural network (ANN) model of 2 * 5 * 1 architecture was employed to predict the thermal decomposition of high-ash sewage sludge, showed a good agreement between the experimental values and predicted values (R2 ⩾ 0.999) are much closer to 1. Overall, the study reflected the significance of ANN model that could be used as an effective fit model to the thermogravimetric experimental data.

Comparative study on pyrolysis characteristics and kinetics of lignocellulosic biomass and seaweed

The pyrolysis characteristics and kinetics of lignocellulosic biomass (cotton stalk) and seaweed (Gracilaria lemaneiformis) were studied comparatively. Results of the thermal degradation processes showed that the pyrolysis occurence of G. lemaneiformis is easier than that of cotton stalk. However, G. lemaneiformis released less volatile components and produced more solid residues. As the heating rate increased, the maximum mass loss rates for cotton stalk were decreased, while those for G. lemaneiformis were increased. Results of the kinetic analysis by Popescu method indicated that the pyrolysis mechanism of cotton stalk is three-dimensional diffusion, which can be described by Zhuralev, Lesokin, and Tempelmen (Z–L–T) equation \((G(\alpha ) = \{ [1/(1 - \alpha )]^{1/3} - 1\}^{2} )\), whereas that of G. lemaneiformis is random nucleation and nuclei growth, which can be described by Avrami–Erofeev equation \((G(\alpha ) = [ - \ln (1 - \alpha )]^{1/4} )\). The average activation energy values (192.17 and 146.11 kJ mol−1, respectively) of cotton stalk and G. lemaneiformis obtained by Popescu method are similar with those (189.88 and 153.79 kJ mol−1, respectively) calculated by Flynn–Wall–Ozawa (FWO) method. Moreover, the average activation energy of G. lemaneiformis is lower than that of cotton stalk.

Thermogravimetric and kinetic analysis of thermal decomposition characteristics of microbial calcites induced by cyanobacteria Synechocystis sp. PCC6803

Although various complicated methods have always been made attempts, it is still well difficult to efficiently distinguish between the biogenic and abiogenic minerals in geological area up to now. In present study, the thermal decomposition unique characteristics of microbial calcites (MC), induced by cyanobacteria Synechocystis sp. PCC6803, were compared with those of chemical calcites (CC) prepared by the reaction of sodium carbonate (Na2CO3) with calcium chloride (CaCl2). Two samples were firstly analyzed by scanning electron microscope and X-ray diffraction, and were further investigated thermal decomposition behaviors using a thermogravimetric analyzer at different heating rates of 278.15, 283.15, 293.15, and 303.15 K min−1 from 323.15 to 1273.15 K, respectively, then kinetic parameters were calculated via Popescu, Kissinger–Akahira–Sunose, and Flynn–Wall–Ozawa methods, and then the kinetics mechanism functions were deduced by Popescu method. The results showed that these two kinds of precipitates were actually both calcite crystals although the surface morphologies were quite different. Whereas thermal decomposition kinetics mechanism function of MC can be described as Avrami–Erofeev equation ([−ln(1 − α)]1/3), while CC corresponded to Contracting sphere (volume) ([1 − (1 − α)]1/3), the results also showed that the average activation energy of MC and CC was 217.9 and 170.5 kJ mol−1, respectively; that is, MC has higher thermal stability, which should be originated from the inducing effects and the different precipitation conditions provided by Synechocystis sp. PCC6803. These above results provided useful information not only for efficiently distinguishing between the biogenic and abiogenic minerals in geological area, and also for better understanding the microbial mineralization.

Characteristic and kinetics of corn stalk pyrolysis in a high pressure reactor and steam gasification of its char

Pyrolysis characteristics of the corn stalk were investigated at different temperatures and pressures, with focus mainly on the releasing profiles and forming behaviors of gas. The results show that a higher pressure was conducive to the yield of H2 and CH4, and was not conducive to the generation of CO. Combustible gas components increase with the increase temperature. H2 concentration was affected significantly by temperature, was mainly released at higher temperatures (>500°C). At 700°C, the combustible gas components are up to 90% and H2 concentration is up to 51.78%. The gas components of corn stalk pyrolysis char steam gasification mainly consisted of CO and H2, 25.7% and 50.7% respectively. The calorific value of gasification gas is up to 9508.9kJ/M3. A kinetic study of the pyrolysis process of the corn stalk was investigated using a thermogravimetric analyzer. As the heating rate increased, the activity energy reduced. By using the Popescu method to determine that shrinking core model can reflect the pyrolysis process of corn stalk truly at low temperature pyrolysis, and chemical reaction model can reflect the pyrolysis process of corn stalk truly at high temperature pyrolysis. Experimental results showed that values of kinetic parameters can be successfully used to understand the degradation mechanism of solid-state reaction.

A study of coal chars combustion in O2/H2O mixtures by thermogravimetric analysis

Oxy-steam combustion is a new oxy-fuel combustion technology which involves fuels burn in pure oxygen, and the high temperature is moderated using either water or steam. In this study, FG and XS char samples were prepared in a horizontal tube furnace at 1073 K under argon atmosphere. The combustion characteristics and kinetic parameters of FG and XS char in O2/H2O atmosphere were studied using non-isothermal thermogravimetric analysis. The results indicated that replacing N2 by H2O caused the improved in the combustion reactivity and performance of FG and XS char with the identical oxygen concentration. The ignition temperature, peak temperature and burnout temperature in O2/H2O atmosphere were lower than those in O2/N2 atmosphere with the identical oxygen concentration. The activation energy values of FG and XS determined by three mode-free methods decreased with the increasing conversion level, and the activation energy of FG char was less than that of XS char at the same conversion. The kinetic mechanism function calculated result based on the combination of the Popescu method and the Coats–Redfern integral method showed the combustion of FG char in O2/H2O atmosphere followed the first-order chemical reaction kinetic.

Non-isothermal thermal decomposition kinetics of high iron gibbsite ore based on Popescu method

The thermal decomposition kinetics of high iron gibbsite ore was investigated under non-isothermal conditions. Popescu method was applied to analyzing the thermal decomposition mechanism. The results show that the most probable thermal decomposition mechanism is the three-dimensional diffusion model of Jander equation, and the mechanism code is D3. The activation energy and pre-exponential factor for thermal decomposition of high iron gibbsite ore calculated by the Popescu method are 75.36 kJ/mol and 1.51−105 s−1, respectively. The correctness of the obtained mechanism function is validated by the activation energy acquired by the iso-conversional method. Popescu method is a rational and reliable method for the analysis of the thermal decomposition mechanism of high iron gibbsite ore.

SYNTHESIS, CRYSTAL STRUCTURE, AND THERMAL DECOMPOSITION KINETICS OF HOLMIUM WITH BENZOATE AND 2, 2'-BIPYRIDINE COMPLEX

ABSTRACT The complex [Ho(BA) 3 bipy] 2 (BA=benzoate; bipy=2,2′-bipyridine) was synthesized and characterized by elemental analysis, infrared spectra, ultraviolet spectra, single-crystal X-ray diffraction, thermogravimetry and differential thermogravimetry (TG-DTG) techniques. The crystal is monoclinic with space group P 2 1 / n . The unit cell parameters are: a =14.1114(8) A, b =15.3743(9) A, c =25.8887(14) A, β=103.555(2)°. Two Ho 3+ ions are connected by four carboxylic groups through a bridging bidentate mode. The thermal decomposition behavior of the title complex under nitrogenous atmosphere was studied using the TG-DTG, and IR techniques. The non-isothermal kinetics was investigated by using the Popescu method and the integral iso-conversional non-linear method (NL-INT). The mechanism function of the first decomposition step was determined. The thermodynamic parameters (Δ G ≠ , Δ H and Δ S ≠ ) were also calculated, and kinetic parameters (activation energy E and the pre-exponential factor

Thermal kinetics and decomposition mechanism of 1-amino-1,2,3-triazolium nitrate

The thermal decomposition kinetics of 1-amino-1,2,3-triazolium nitrate(ATZ-NO3) was investigated by non-isothermal TG-DTG at various heating rates(2, 5, 10, 15 and 20 °C/min). The results show that the thermal decomposition of ATZ-NO3 consist of two stages corresponding to the losing of nitrate anion, substituent group and the splitting of triazole ring respectively. The kinetic triplets of the two stages were described by a three-step method. First, the differential Kissinger and intergral Ozawa methods were used to calculate the apparent activation energies(E) and pre-exponential factors(A) of the two decomposition stages. Second, two calculation methods(intergral Satava-Sestak and differential Achar methods) were used to obtain several probable decomposition mechanism functions. Third, three judgment methods(average, double-extrapolation and Popescu methods) were used to confirm the most probable decomposition mechanism functions. Both reaction models of the two stages were random-into-nucleation and random-growth mechanisms with n=3/2 for the first stage and n=1/3, m=3 for the second stage. The kinetic equations for the two decomposition stages of ATZ-NO3 may be expressed as \(\frac{{da}} {{dt}} = 10^{13.60} \times e^{ - \frac{{128970}} {{RT}}} (1 - a)\left[ { - \ln (1 - a)} \right]^{ - \frac{1} {2}}\) and \(\frac{{da}} {{dt}} = 10^{11.41} \times e^{ - \frac{{117370}} {{RT}}} (1 - a)\left[ { - \ln (1 - a)} \right]^{\frac{2} {3}}\). The thermodynamic parameters including Gibbs free energy of activation(ΔG ≠), entropy of activation(ΔS ≠) and enthalpy of activation(ΔH ≠), for the thermal decomposition reaction were also derived.

A Kinetic Study of Wetland Plant &lt;i&gt;Suaeda salsa&lt;/i&gt; L. Pyrolysis Using Thermogravimetric Analyzer

The Suaeda salsa L. has been discovered to be a great potential as a new kind of renewable energy. The pyrolytic characteristics and kinetics of S. salsa were investigated at heating rates of 5, 10, 20, 30°C/min under nitrogen atmosphere respectively. The most probable mechanism function was deduced using Popescu method, which is a three-dimensional diffusion function (), and n=-2/3. Activation energy and pre-exponential factors were studied through the FWO, KAS and Popescu methods. The results showed that the activation energy increase as the pyrolysis process and three stages were observed in the TG-DTG curves of S.salsa. The results showed that S.salsa as a pyrolysis feedstock has a great potential and a good prospect in bio-oil production.

Non-isothermal kinetics of styrene—butadiene—styrene asphalt combustion

The combustion characteristics of styrene—butadiene—styrene (SBS) asphalt are studied by thermogravimetric analysis (TG/DTG) at four different heating rates. According to the saturates/aromatics/resins/asphaltenes (SARA) fractionation method, the combustion process of SBS asphalt can be divided by Gaussian peak fitting into three main stages: oil content release, resin pyrolysis, and asphaltene and char combustion. When the heating rate increases, the mass losses of the oil content and resin pyrolysis increase, and less asphaltenes are formed at a higher temperature. The activation energy values are calculated by the Coats—Redfern method to be in the range 61.6 kJ/mol–142.9 kJ/mol. The Popescu method is used for the kinetic analysis, and the result shows that the three stages of asphalt combustion can be explained by the sphere phase boundary reaction model, the second order chemical reaction model, nucleation, and its subsequent growth model, respectively.

Reaction Mechanism Study on Combustion of Micro Nanometer Iron Powder

Thermogravimetric curves of micro nanometer iron powder’s combustion were studied in different heating rates that were 10K/min, 20 K/min, 30 K/min and 40 K/min, and the particle sizes of iron were 100nm and 20μm. The iron’s kinetic parameters of combustion reaction were calculated by Coats-Redfern integral, differential and Kissinger methods, then the kinetic model was determined and the most probable mechanism function was verified by Popescu method. The results show that different heating rates, particle sizes and calculations can affect kinetic parameters and reaction mechanism. The activation energy of 100nm and 20μm iron powder’s combustion is 122.48 KJ/mol and 161.64 KJ/mol respectively. The combustion reaction of micro nanometer iron powder is controlled by random nucleation and subsequent growth model which is in agreement with Avrami-Erofeev equation. Rational control for the temperature and reaction time are conducive to optimize the combustion reaction of micro nanometer iron powder.

Thermal Stability and Kinetic Analysis of &lt;i&gt;Xanthoceras sorbifolia&lt;/i&gt; Polysaccharide

Pyrolysis and kinetic analysis of Xanthoceras Sorbifolia polysaccharide were evaluated using the TG-DTG/DTA method. The results indicated that its mass loss occured in three-step process . The first step could be attributed to the expulsion of water of crystallization at 25 - 176 °C. The second step corresponded to the large scale degradation of X. Sorbifolia polysaccharide in the temperature range of 179 - 661 °C. The final step was slow degradation of residues. Heating rate had significant effects on the pyrolysis of X. Sorbifolia polysaccharide and nitrogen could improve its stability. A close value of activation energy E of the thermal degradation process has been obtained by FWO, KAS and Popescu methods. The possible kinetic model was estimated to be Jander 5 (g(α)=[1-(1-α)1/3]1/2.

Evalution of the Pyrolytic and Kinetics Characteristics of &lt;i&gt;Xanthoceras&lt;/i&gt; &lt;i&gt;sorbifolia&lt;/i&gt; Oil

The pyrolytic characteristics and kinetics of Xanthoceras sorbifolia oil were investigated at heating rates of 10, 20 and 30 °C min-1 in an inert atmosphere. The most probable mechanism function and activation energy pre-exponential factors were calculated by the Popescu, FWO and KAS methods. Three stages appeared during pyrolysis: moisture evaporation, primary devolatilization and residual decomposition. Significant differences in the average activation energy, thermal stability, final residuals and reaction rates of the X. sorbifolia oil at different heating rate were observed. Stage II of the X. sorbifolia oil could be described by the Mampel Power equation 22 (n=0.25). The average activation energy of X. sorbifolia oil was 346 kJ mol-1.