Method For Kinetic Analysis Research Articles

Insight into master plots method for kinetic analysis of lignocellulosic biomass pyrolysis

The determination of the kinetic triplet including the activation energy, frequency factor, and kinetic mechanism function is a key objective in kinetic analysis of solid-state reactions like lignocellulosic biomass pyrolysis. The master plots method is usually used to determine the kinetic mechanism function once the activation energies as a function of conversion are estimated from an isoconversional method. A critical study of the master plots method has been performed by analyzing theoretically simulated processes with varying activation energies and frequency factors. The accuracy of the resulting kinetic mechanism function calculated by the master plots method is strongly dependent on the variation degree of the frequency factor with conversion and the conversion dependency of activation energy from isoconversional methods. The utilization of the master plots method without considering the variation degree of the frequency factor with conversion may result in misestimating kinetic mechanism function.

Research on carbonization kinetic of cellulose-based materials and its application

As a renewable resource, cellulose-based material (CBM) is frequently adopted to prepare functional carbon materials, which have been extensively used in the fields of catalysis, environment protection and energy. It is important for researchers in material field to quickly obtain methods for the carbonization kinetic analysis of CBM. In this work, a framework method for quickly determining carbonization process and kinetics parameters is developed. The new framework method employed inventive initial estimation, binary tree assumption, linear programming together with rigorous experimental verification. According to TG experiment data, CBM is divided into two parts marked by free-ends of raw material (corresponding 10 % with free-end in MCC), which undergo different reaction. The results of optimized model show the isothermal TG data has a high accordance, the max Root Mean Squared Error (RMSE) of 0.01, as well as the max RMSE under constant heating rate is 0.009. Furthermore, as a demonstration of using new framework, carbonization reaction of nanocellulose (NNC) is primitively investigated.

Study on the oxidation thermal kinetics of the spontaneous combustion characteristics of water-immersed coal

Water-immersed coal is more likely to spontaneously combust than raw coal. To investigate their differences from the perspective of thermal kinetics, thermogravimetric experiments were conducted with water-immersed coal and raw coal. Thermodynamic parameters were calculated and compared with five different kinetic analysis methods. Results showed that the activation energies of water-immersed coal obtained by five methods were all reduced by more than 19 % than those of raw coal. It indicated that the energy required for the self-heating and spontaneous combustion of water-immersed coal was remarkably lower than that of raw coal. This observation was the dynamic reason why water-immersed coal was more likely to spontaneously combust than raw coal. In addition, among these kinetic methods, the Kissinger-Akahira-Sunose (KAS) method is more accurate and is highly recommended. This research provides better understanding of the spontaneous combustion mechanism of water-immersed coal and allows for kinetic parameters to be calculated more accurately.

Analysis of decay kinetics of the cytosolic calcium transient induced by oxytocin in rat myometrium smooth muscle cells.

The method of kinetic analysis of the relaxation phase of the mechanical response of the smooth muscle previously proposed by Burdyga and Kosterin was applied to study the dynamics of the decay of oxytocin-induced calcium transients in cytosol of the rat myometrium smooth muscle cell detected by a fluorescence signal generated by a calcium-sensitive probe fluo-4 using a laser scanning confocal microscope. The experimental data were well linearized in the coordinates ln [(Fm - F)/F] vs lnt (F and Fm are the current fluorescence intensity of the calcium probe and the fluorescence intensity at the maximum of the calcium transient, respectively, while t is the time). The empirical parameters n and τ were determined by which the maximal normalized relaxation rate Vn was calculated for five different ROIs (regions of interest) in the myocyte cytosol. It proved to be almost the same for all ROIs. The maximal normalized relaxation rate calculated from the fluorescence intensity was always lower than that calculated from the corresponding calcium concentration, i.e. the cytosolic Ca2+ concentration in the relaxation phase decreases faster than the corresponding fluorescence intensity. The value of the maximal normalized relaxation rate calculated both from the fluorescence intensity and from the force of oxytocin-induced contractions of isolated rat uterus longitudinal smooth muscles (according to Tsymbalyuk and Kosterin) was exactly the same. This indicates that in the relaxation phase, the decreasing curves of both the fluorescence intensity and the contraction forces coincide.

Thermal Stability of Ionic Liquids: Current Status and Prospects for Future Development

Ionic liquids (ILs) are the safest solvent in various high-temperature applications due to their non-flammable properties. In order to obtain their thermal stability properties, thermogravimetric analysis (TGA) is extensively used to analyze the kinetics of the thermal decomposition process. This review summarizes the different kinetics analysis methods and finds the isoconversional methods are superior to the Arrhenius methods in calculating the activation energy, and two tools—the compensation effect and master plots—are suggested for the calculation of the pre-exponential factor. With both parameters, the maximum operating temperature (MOT) can be calculated to predict the thermal stability in long-term runnings. The collection of thermal stability data of ILs with divergent cations and anions shows the structure of cations such as alkyl side chains, functional groups, and alkyl substituents will affect the thermal stability, but their influence is less than that of anions. To develop ILs with superior thermal stability, dicationic ILs (DILs) are recommended, and typically, [C4(MIM)2][NTf2]2 has a decomposition temperature as high as 468.1 °C. For the convenience of application, thermal stability on the decomposition temperature and thermal decomposition activation energy of 130 ILs are summarized at the end of this manuscript.

Spectral-Phase Interferometry Detection of Ochratoxin A via Aptamer-Functionalized Graphene Coated Glass.

In this work, we report a novel method of label-free detection of small molecules based on direct observation of interferometric signal change in graphene-modified glasses. The interferometric sensor chips are fabricated via a conventional wet transfer method of CVD-grown graphene onto the glass coverslips, lowering the device cost and allowing for upscaling the sensor fabrication. For the first time, we report the use of graphene functionalized by the aptamer as the bioreceptor, in conjunction with Spectral-Phase Interferometry (SPI) for detection of ochratoxin A (OTA). In a direct assay with an OTA-specific aptamer, we demonstrated a quick and significant change of the optical signal in response to the maximum tolerable level of OTA concentration. The sensor regeneration is possible in urea solution. The developed platform enables a direct method of kinetic analysis of small molecules using a low-cost optical chip with a graphene-aptamer sensing layer.

Thermal decomposition of β-cyclodextrin and its inclusion complex with vitamin E

Thermogravimetric kinetic investigation of β-cyclodextrin and its inclusion complex with vitamin E has been carried out. The activation energy and pre-exponential factor of their thermal decomposition have been determined based on the kinetic analysis methods known as the Freeman–Carroll, Sharp–Wentworth, Achar and Coats–Redfern ones.

Video-based calcification assay: A novel method for kinetic analysis of osteogenesis in live cultures

Traditional methods of quantifying osteoblast calcification in culture require the use of calcium sensitive dyes, such as Arsenazo III or Alizarin Red S, which have been successfully used for decades to assess osteogenesis. Because these dyes elicit a colorimetric change when reacted with a cell lysate and are cytotoxic to live cells, they forfeit the ability to trace calcification longitudinally over time. Here, we demonstrate that image analysis and quantification of calcification can be performed from a series of time-lapse images acquired from videos. This method capitalizes on the unique facet of the mineralized extracellular matrix to appear black when viewed with phase contrast optics. This appearance of calcified areas had been previously documented to be characteristic to the formation of bone nodules in vitro. Due to this distinguishable appearance, extracting the information corresponding to calcification through segmentation allowed us to threshold only the pixels that comprise the mineralized areas in the image. Ultimately, this method can be used to quantify calcification yield, rates and kinetics facilitating the analyses of bone-supportive properties of growth factors and morphogens as well as of adverse effects elicited by toxicants. It may also be used on images that were acquired manually.•The method is less error-prone than absorption-based assays since it takes longitudinal measurements from the same cultures•It is cost effective as it foregoes the use of calcium-sensitive dyes•It is automatable and amenable to high-throughput and thus allows the concurrent quantification of multiple parameters of differentiation

Curing Reaction Kinetics of the EHTPB-Based PBX Binder System and Its Mechanical Properties

In this research, differential scanning calorimetry (DSC) was employed to compare the curing reaction kinetics of the epoxidized hydroxyl terminated polybutadiene-isophorone diisocyanate (EHTPB-IPDI) and hydroxyl terminated polybutadiene-isophorone diisocyanate (HTPB-IPDI) binder systems. Glass transition temperature (Tg) and mechanical properties of the EHTPB-IPDI and HTPB-IPDI binder systems were determined using the DSC method and a universal testing machine, respectively. For the EHTPB-IPDI binder system, the change of viscosity during the curing process in the presence of dibutyltin silicate (DBTDL) and tin 2-ethylhexanoate (TECH) catalysts was studied, and the activation energy was estimated. The results show that the activation energies (Ea) of the curing reaction of the EHTPB-IPDI and HTPB-IPDI binder systems are 53.8 and 59.1 kJ·mol−1, respectively. While their average initial curing temperatures of the two systems are 178.2 and 189.5 °C, respectively. The EHTPB-IPDI binder system exhibits a higher reactivity. Compared with the HTPB-IPDI binder system, the Tg of the EHTPB-IPDI binder system is increased by 5 °C. Its tensile strength and tear strength are increased by 12% and 17%, respectively, while its elongation at break is reduced by 10%. Epoxy groups and isocyanates react to form oxazolidinones, thereby improving the mechanical properties and thermal stability of polyurethane materials. These differences indicate that the EHTPB-IPDI binder system has better thermal stability and mechanical properties. During the EHTPB-IPDI binder system’s curing process, the DBTDL catalyst may ensure a higher viscosity growth rate, indicating a better catalytic effect, consistent with the prediction results obtained using the non-isothermal kinetic analysis method.

Fire Retardancy and Thermal Degradation Kinetics of Epoxy Composites Containing Polyaminopropylphenylsilsesquioxane

Polyaminopropylphenylsilsesquioxane (PA) was proved to be an effective fire retardant for epoxy resin (EP) by cone calorimeter measurements, since a significant peak heat release rate (PHRR) reduction of 42% was achieved from the EP/PA fire retardant epoxy (FREP) system relative to the pure EP. The thermal degradation behavior was investigated by thermogravimetric analysis (TGA) and the fire-retardant mechanism of the FREP system was studied by kinetics analysis methods, including the Kissinger method and the Flynn-Wall-Ozawa method. The calculated results of the Kissinger method showed that the activation energy of the FREP was slightly lower than that of pure EP. The Flynn-Wall-Ozawa method further revealed that the addition of the fire retardant PA increased the activation energies of FREP thermal degradation in the final stage, which illustrated that PA promoted the thermal degradation of EP in the early and middle stages and subsequently, stabilized the char residues and improved the fire retardancy of FREP in the thermal degradation process.

Evaluation of the Validity of Model-Fitting and Model-Free Methods for Kinetic Analysis of Nonisothermal Pyrolysis of Siberian Fir Bark

The kinetic parameters of the pyrolysis of Siberian fir bark were estimated by thermogravimetric analysis. The thermochemical conversion of the bark biomass was performed at heating rates of 5, 10, and 20 deg/min in an inert (argon) medium. The results of thermogravimetric and differential thermogravimetric analyses were studied by model-fitting (Arrhenius and Coats–Redfern) and model-free (Friedman and Ozawa–Flynn–Wall) kinetic methods. The most reliable values of the activation energy were obtained by the model-free Ozawa–Flynn–Wall and Friedman methods (159 and 156 kJ/mol, respectively). It was shown that using these kinetic models enables one to determine more accurate temperature ranges of decomposition of biomass components under pyrolysis conditions.

Frequency domain analysis to extract dynamic response characteristics for oxygen uptake during transitions to moderate- and heavy-intensity exercises.

At the onset of an exercise transition, exponential modeling to calculate a time constant (τ) is the conventional method to analyze pulmonary oxygen uptake (V̇O2p) kinetics for moderate and heavy exercises. A new frequency domain analysis technique, mean normalized gain (MNG), has been used to analyze V̇O2p kinetics during moderate exercise, but has not been evaluated for its ability to detect differences in kinetics between moderate and heavy exercises. This study tested the hypothesis that MNG would detect smaller amplitude V̇O2p responses in the heavy-exercise domain compared with moderate-exercise domain. Eight young healthy adults (3 female; age: 27 ± 6 yr; peak V̇O2p: 43 ± 6 mL·min-1·kg-1; means ± SD) performed three bouts of pseudorandom binary sequence (PRBS) exercise for frequency analysis, with the work rate (WR) changing between 25 W and 90% ventilatory threshold (VT; L → MPRBS), 25 W and 50% of the difference between VT and peak V̇O2p (Δ50%; L → HPRBS), and VT to Δ50% (VT → HPRBS). Step exercise tests with equivalent changes in WR to the PRBS tests were performed to facilitate the comparison between MNG and τ. MNG was the highest for L → MPRBS (59 ± 7%), then L → HPRBS (52 ± 6%), and the lowest for VT → HPRBS (38 ± 7%, F(2,14) = 129.755, P < 0.001) exercise conditions indicating slower kinetics with increasing exercise intensity that correlated strongly in repeated measures with τ from step transitions (rrm = -0.893). These results indicate that frequency domain analysis and MNG reliably detect differences in V̇O2p kinetics observed across exercise intensity domains.NEW & NOTEWORTHY Mean normalized gain is able to detect differences in V̇O2p kinetics between moderate-, heavy-, and heavy-intensity exercises from a raised WR within the same individuals. This new method of kinetic analysis may be advantageous compared with conventional V̇O2p curve fitting, as it is less sensitive to breath-by-breath noise, it can provide useful information from a single exercise testing session, and it can be applied to nonconstant work rate exercise situations.

Investigation of sewage sludge and peanut shells co‐combustion using thermogravimetric analysis and artificial neural network

To solve the problems of energy shortage and waste accumulation, the method of co-combustion of sewage sludge (SS) and peanut shells (PS) was proposed. SS-PS co-combustion characteristics in air were investigated using artificial neural networks (ANN) and thermogravimetric analyses (TGA). The proportion of PS in the mixture was 10%-50%. The temperature range of PS combustion (160-560°C) is lower than that of PS combustion (170-600°C). Activation energy was estimated from two non-isothermal kinetic analysis methods: Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The kinetic mechanism of the combustion process was determined by using the master-plots method. Multiple ANN models were established to predict TG data of SS-PS co-combustion. The best prediction model (ANN21) was obtained. The results showed a good overlap between the predicted and experimental TG data. The ANN model and the master-plots method are the main innovations of this study. This study can promote the utilization and reduction of solid waste, and give guidance for the large-scale application of SS-PS co-combustion.

Major Improvements in Robustness and Efficiency during the Screening of Novel Enzyme Effectors by the 3-Point Kinetics Assay.

The throughput level currently reached by automatic liquid handling and assay monitoring techniques is expected to facilitate the discovery of new modulators of enzyme activity. Judicious and dependable ways to interpret vast amounts of information are, however, required to effectively answer this challenge. Here, the 3-point method of kinetic analysis is proposed as a means to significantly increase the hit success rates and decrease the number of falsely identified compounds (false positives). In this post-Michaelis-Menten approach, each screened reaction is probed in three different occasions, none of which necessarily coincide with the initial period of constant velocity. Enzymology principles rather than subjective criteria are applied to identify unwanted outliers such as assay artifacts, and then to accurately distinguish true enzyme modulation effects from false positives. The exclusion and selection criteria are defined based on the 3-point reaction coordinates, whose relative positions along the time-courses may change from well to well or from plate to plate, if necessary. The robustness and efficiency of the new method is illustrated during a small drug repurposing screening of potential modulators of the deubiquinating activity of ataxin-3, a protein implicated in Machado-Joseph disease. Apparently, intractable Z factors are drastically enhanced after (1) eliminating spurious results, (2) improving the normalization method, and (3) increasing the assay resilience to systematic and random variability. Numerical simulations further demonstrate that the 3-point analysis is highly sensitive to specific, catalytic, and slow-onset modulation effects that are particularly difficult to detect by typical endpoint assays.

Investigating the Kinetics, Mechanism, and Activation Energy of Limestone Calcination Using Isothermal Analysis Methods

In the current research, isothermal experiments of kinetic analysis were performed at different temperatures (800–1050 °C) and particle sizes (885 to 10,763 μm) to investigate the calcination kinetics of high-purity limestone. Thermal analyses were carried out in a zirconia crucible, 1 cm in height, for different temperatures and particle sizes. The reaction rate coefficients were varied in the 2.2 × 10−5-1.62 × 10−3-m0.6.s−1 range. Moreover, various isothermal kinetic analysis methods were applied to assess the decomposition mechanism and the calcination function governing the process. The modified shrinking core model was found as the best representation of the high-purity limestone kinetic data. The activation energy was evaluated using the Arrhenius curve, and an average value of 86 kJ.mol−1 was obtained.

Thermodynamics, kinetics, gas emissions and artificial neural network modeling of co-pyrolysis of sewage sludge and peanut shell

The co-pyrolysis characteristics of sewage sludge (SS) and peanut shell (PS) under nitrogen atmosphere were studied by thermogravimetric – Fourier transform infrared spectrometry (TG-FTIR) and artificial neural network (ANN). The proportion of PS in the experimental samples is 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%. The experiments were performed at three heating rates of 5 °C/min, 7 °C/min and 10 °C/min. The variation of sample mass with temperature and gas emission were detected in this paper. SS and PS in the co-pyrolysis experiment have a synergistic effect in terms of mass loss at 335 °C ∼ 500 °C. Gases generated by pyrolysis of the mixture of SS and PS include H2O, CH4, CO2, CO, phenol and NH3. The functional groups detected in the experiment include CO and C O. Apparent activation energy E was obtained by two non-isothermal kinetic analysis methods (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose). The artificial neural network method was used to predict the relationship between the mass loss of pyrolysis experiments and the change of temperature. The best ANN model (ANN21) for predicting SS and PS pyrolysis was identified.

Isothermal by Design: Comparison with an Established Isothermal Nucleation Kinetics Analysis Method

AbstractThe nucleation kinetics of the alpha form of p‐aminobenzoic acid from ethanolic and aqueous solutions is examined through a comparative examination of temperature‐jump and anti‐solvent drown‐out isothermal crystallization methodologies. Analysis of the data reveals the measured induction times, and the calculated effective interfacial tensions as a function of the supersaturation show broadly equivalent behavior for the aqueous‐ethanol mixed‐solvent drown‐out and temperature‐jump ethanol solution systems, confirming the comparability of the two methodologies. The results also demonstrate poorer agreement with the temperature‐jump pure aqueous system, highlighting the importance of the strength of solvation/desolvation as the key rate‐limiting process for the overall nucleation behavior.

The thermal degradation mechanism and kinetic analysis of hydrogenated bisphenol-A polycarbonate

Hydrogenated bisphenol-A polycarbonate (PHBPA) was successfully synthesized from dimethyl carbonate (DMC) and hydrogenated bisphenol-A (HBPA) by the method of two-step polycondensation. The chemical structure and the molecular weight of PHBPA was identified by 1H-NMR spectra and gel permeation chromatography (GPC), respectively. In order to analyze the thermal degradation mechanism of PHBPA, a non-isothermal pyrolysis process was conducted and the violate products were detected using Fourier-transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC-MS). There were some reactions occurred during the pyrolysis including decarboxylation, disproportionation of the C–H transfer and β–H transfer, and the Fries rearrangement. In addition, the well-known Flynne–Walle–Ozawa (FWO) and Coats–Redfern kinetic analysis methods were used to calculate the values of activation energy and pre-exponential factors. Furthermore, isothermal pyrolysis experiments were performed and revealed that the reaction of decarboxylation occurred at 225 °C. This decarboxylation suggests that the molecular chain of PHBPA does not easily grow to a high-molecular-weight polymer.

Long-term Thermo-oxidative Degradation Modeling of a Carbon Fiber Reinforced Polyimide Composite: Multistep Degradation Behaviors and Kinetics

This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide (CFRPI) composite for modeling of the long-term degradation process. The degradation behaviors were revealed through off-gas products analysis, and the overall kinetic interpretation was achieved from study of the mass-loss curves recorded under dynamic conditions. It was found that thermo-oxidative degradation of the CFRPI composite was a multistep process, which included four main reaction steps. Since most kinetic analysis methods were derived from simple reactions described by a single kinetic triplet, they cannot be applied reliably to such a process. Therefore, we firstly separated the four overlapped reaction steps by peak fitting of derivative thermogravimetric curves using Frasier-Suzuki equation considering the asymmetrical nature of kinetic curves, and subsequently analyzed each individual reaction employing Friedman method and experimental master-plots method. Four sets of kinetic triplets were determined to characterize the entire degradation process. The validity of four corresponding kinetic triplets was confirmed by perfect simulation of mass-loss curves recorded at both dynamic conditions used in kinetic analysis and entirely different isothermal conditions. Finally, modeling of long-term aging at 400 °C of the CFRPI composite was successfully achieved based on these kinetic triplets. The predicted mass loss and flexural property correlated well with experimental results. This study can serve as a basis for rapid evaluation of the long-term durability of the CFRPI composite in various application environments.

Kinetic analysis and catalytic pyrolysis of spent medicinal herb over HZSM-5 and HY

In this study, the kinetic analysis on the pyrolysis of a spent medicinal herb, namely spent Achyranthes root, is performed using a thermogravimetric analyzer and a model-free kinetic analysis method, allowing the calculation of activation energy values without the assumption of kinetic model. Owing to the structural change of lignin and elimination of hemicellulose during the decoction of raw Achyranthes root, the thermogravimetric analysis results show a large difference between the derivative thermogravimetry curves of spent and raw Achyranthes roots. The average apparent activation energy value of spent Achyranthes root, obtained from the non-isothermal thermogravimetric analysis, are found to be lower than those of raw Achyranthes root. This comes as a result of the much lower content of hemicellulose in spent Achyranthes root caused by the hemicellulose elimination from raw Achyranthes root during the decoction process. The catalytic fast pyrolysis of spent Achyranthes root over HZSM5-30 (HZSM-5 with SiO2/Al2O3 = 30) and HY30 (HY with SiO2/Al2O3 = 30) was performed using a two-stage fixed-bed reactor system. The catalytic fast pyrolysis of spent Achyranthes root over both HY30 and HZSM5-30 produced the much larger amount of aromatic hydrocarbons, compared to the non-catalytic fast pyrolysis, with a parallel decrease of oxygen-containing pyrolyzates. Owing to its robust pore structure and high acidity, it was the HZSM5-30 that produced the highest quality oil during the catalytic fast pyrolysis of spent Achyranthes root, having higher selectivity of mono-aromatic hydrocarbons compared to HY30.