Distribution Of Activation Energies Research Articles

Approaches to Biomass Kinetic Modelling: Thermochemical Biomass Conversion Processes

Modeling of biomass pyrolysis kinetics is an essential step towards reactors design for energy production. Determination of the activation energy, frequency factor, and order of the reaction is necessary for the design procedure. Coats and Redfern's work using the TGA data to estimate these parameters was the cornerstone for modeling. There are two significant problems with biomass modeling, the first is the determination of the kinetic triplet (Activation energy, Frequency factor, and the order of reaction), and the second is the quantitative analysis of products distribution. Methods used in modeling are either One-step or Multistep methods. The one-step techniques allow the determination of kinetic triplet but fail to predict the product distribution, whereas multistep processes indicate the product's distribution but challenging to estimate the parameters. Kissinger, Coats, and Redfern, KAS, FWO, Friedman are one-step methods that have been used to estimate the kinetic parameters. In this work, after testing more than 500 data points accessed from different literature sources for coal, oil shale, solid materials, and biomass pyrolysis using one-step global method, it was found that the activation energy generated by KAS or FWO methods are related as in the following equations: 𝐸𝐾𝐴𝑆 = 0.9629 ∗ 𝐸𝐹𝑊𝑂 + 8.85, with R² =0.9945 or 𝐸𝐹𝑊𝑂 = 1.0328 ∗ 𝐸𝐾𝐴𝑆 − 8.0969 with R2= 0.9945. The multistep kinetic models employed the Distributed Activation Energy Model (DAEM) using Gaussian distribution, which suffers from symmetry, other distributions such as Weibull, and logistic has been used. These multistep kinetic models account for parallel/series and complex, primary and secondary biomass reactions by force-fitting the activation energy values. The frequency factor is assumed constant for the whole range of activation energy. Network models have been used to account for heat and mass transfer (diffusional effects), where the one-step and multistep could not account for these limitations. Three network models are available, the Bio-CPD (Chemical Percolation Devolatilization) model, Bio-FLASHCHAIN, and the Bio-FGDVC (Functional Group Depolymerization Vaporization Crosslinking models). These models tried to predict the product distributions of the biomass pyrolysis process

Kinetic analysis and in-situ no support catalytic pyrolysis product distribution of Chinese herb residue

Pyrolysis is a research hotspot for realizing Chinese Herb residue (CHR) treatment and resource utilization, but there is little reported about in-situ no support catalytic pyrolysis of CHR. In this work, kinetics and no support catalytic pyrolysis characteristics of CHR were studied using a thermogravimetric analyzer and a fix-bed reactor system, respectively. Three groups: Ni-Fe, Ni-Cu and Ni-Co add into CHR and three kinetic methods: Coats-Redfern (CR) method, Flynn-Wall-Ozawa (FWO) method and Distributed Activation Energy Model(DAEM)use for calculate the activation energy, then analyses the gas, bio-oil and char of CHR pyrolysis. The results show that, catalysts can reduce the pyrolysis reaction activation energy. In FWO and DAEM model, the reaction activation energy will increase sharply if the conversion over 0.7. Compare with no catalyst group, add catalyst can restrain gas generation but good for oil production and char formation. Meanwhile, the surface of char is smoother than no catalyst. After test the char, we find that, metals of Ni, Fe, Cu and Co almost enrich in char, which may reuse as catalytic. This study may provide a feasible direction for the industrial application of CHR.

Pyrolysis of electronic waste and their mixtures: Kinetic and pyrolysate composition studies

Electronic waste (e-waste) constitutes an important component of solid waste, and recovering valuable chemicals and resources from it holds a high priority in solid waste management. The various chemical functionalities present in the organic fraction of e-waste can be converted to valuable chemicals and fuel molecules by pyrolysis process. In this study, non-isothermal pyrolysis of waste printed circuit board (PCB), waste keyboard keys (KB), and their equal composition mixture is conducted in a thermogravimetric analyzer at different heating rates. The kinetic analysis was carried out using isoconversional method of Vyazovkin and the multi-Gaussian distributed activation energy model (DAEM). The average apparent activation energies of pyrolysis of PCB, PCB: KB, and KB, determined using the Vyazovkin method, were 188.4, 167.6, and 169 kJ mol−1, respectively. The apparent activation energy determined using the DAEM varied in a wide range owing to the decomposition of multiple pseudo-components. Analytical pyrolysis coupled with gas chromatograph/mass spectrometer (Py-GC/MS) was used to identify the pyrolysates from PCB, KB, and their mixtures at 500 °C. The major pyrolysate functional groups from PCB were phenolic derivatives (36%), oxygenates (26%), and phenyl phosphates (14.4%), while KB pyrolysis yielded aromatics (52%) containing styrene as the major compound. Pyrolysis of mixtures resulted in a net increase in the selectivity to aromatics with a concomitant decrease in oxygenates suggesting dehydration and decarboxylation to be the major reactions. A significant amount of nitriles was produced from the pyrolysis of mixtures owing to the decomposition of acrylonitrile-butadiene-styrene plastic that constitutes KB.

Thermal degradation characteristics and gasification kinetics of camel manure using thermogravimetric analysis

In this work, the sustainable valorisation of camel manure has been studied using thermogravimetric analysis. The gasification tests were performed from ambient conditions to 950 °C at 10, 20, and 50 °C/min under an O2 environment. The TGA data were applied to determine the kinetics of the O2 gasification. Single-heating rate models (Arrhenius and Coats-Redfern) and multi-heating rate models (Distributed activation energy, Friedman, Flynn-Wall-Ozawa, Starink, and Kissinger-Akahira-Sunose) were applied to estimate the kinetics of the process. Between the two single-heating rate models, the Coats-Redfern method fitted best with the experimental data. Among the multi-heating rate models, the Flynn-Wall-Ozawa model fitted best with the experimental results. The kinetic parameters-frequency factor, activation energy, and order of reaction were estimated using the Flynn-Wall-Ozawa model (the best-fitting model) and the estimated kinetic parameters were used to calculate the thermodynamic properties-Gibbs free energy, enthalpy, and entropy. The information on these kinetic and thermodynamic properties can be useful for the design of gasifiers and for optimising the O2 gasification operating conditions.

Comparative study of the reaction kinetics of three residual biomasses

Kinetic analysis for the combustion of three agro-industrial biomass residues (coconut husk, corn husk, and rice husk) was carried out in order to provide information for the generation of energy from them. The analysis was performed using the results of the data obtained by thermogravimetric analysis (TGA) at three heating rates (10, 20, and 30 K/min). The biomass residues were characterized in terms of proximate analysis, elemental analysis, calorific value, lignin content, α-cellulose content, hemicellulose content, and holocellulose content. The biomass fuels were thermally degraded in an oxidative atmosphere. The results showed that the biomass thermal degradation process is comprised of the combustion of hemicellulose, cellulose, and lignin. The kinetic parameters of the distributed activation energy model indicated that the activation energy distribution for the pseudocomponents follows lignin, cellulose, and hemicellulose in descending order. The activation energy values for each set of reactions are similar between the heating rates, which suggests that it is independent of the heating rate between 10 K/min and 30 K/min. For all the biomass samples, the increased heating rate resulted in the overlap of the hemicellulose and cellulose degradation events.

Catalytic Pyrolysis Kinetic Behavior and TG-FTIR-GC-MS Analysis of Metallized Food Packaging Plastics with Different Concentrations of ZSM-5 Zeolite Catalyst.

Recently, the pyrolysis process has been adapted as a sustainable strategy to convert metallized food packaging plastics waste (MFPW) into energy products (paraffin wax, biogas, and carbon black particles) and to recover aluminum. Usually, catalysts are used in pyrolysis treatment to refine pyrolysis products and to increase their yield. In order to study the effect of a catalyst on the formulated volatile products, this work aims to study the pyrolysis behavior of MFPW in presence of catalyst, using TG-FTIR-GC–MS system. The pyrolysis experiments were conducted with ZSM-5 Zeolite catalyst with different concentrations (10, 30, and 50 wt.%) at different heating rates (5, 10, 15, 20, 25, and 30 °C/min). In addition, TG-FTIR system and GC-MS unit were used to observe and analyze the thermal and chemical degradation of the obtained volatile compounds at maximum decomposition peaks. In addition, the kinetic results of catalytic pyrolysis of ZSM-5/MFPW samples matched when model-free methods, a distributed activation energy model (DAEM), and an independent parallel reaction kinetic model (IPR) were used. The TGA-DTG results showed that addition of a catalyst did not have a significant effect on the features of the TGA-DTG curves with similar weight loss of 87–90 wt.% (without taking the weight of the catalyst into account). Meanwhile, FTIR results manifested strong presence of methane and high-intensity functional group of carboxylic acid residues, especially at high concentration of ZSM-5 and high heating rates. Likewise, GC-MS measurements showed that Benzene, Toluene, Hexane, p-Xylene, etc. compounds (main flammable liquid compounds in petroleum oil) generated catalysts exceeding 50%. Finally, pyrolysis kinetics showed that the whole activation energies of catalytic pyrolysis process of MFPW were estimated at 289 kJ/mol and 110, 350, and 174 kJ/mol for ZSM-5/MFPW samples (10, 30, and 50 wt.%, respectively), whereas DAEM and IPR approaches succeeded to simulate TGA and DTG profiles with deviations below <1.

Effects of devolatilization temperature on chemical structure and oxidation reactivity of soot sampled from a coflow diffusion ethylene flame

Devolatilization is a prerequisite for the analysis of chemical structure and oxidation reactivity of soot sampled from engine combustion or lab-scaled flames, while the effects of devolatilization temperature are not sufficiently understood. This work explores the effects of devolatilization temperature on soot chemical structure and oxidation reactivity. Virgin soot samples were collected from five positions along axis of a coflow diffusion ethylene flame using a recently developed capillary-nozzle-hybrid sampling method. Three temperatures (250, 450 and 650 °C) were selected to devolatilize virgin soot samples for further thermogravimetric (TG), Fourier transform infrared and Raman spectroscopic analyses. The results indicate that devolatilization can remove aliphatic and oxygenated groups away from soot surface, mainly below 450 °C. ID1/IG derived from deconvolution of Raman spectra presents positive correlation with nanocrystallite width, however, less sensitive to devolatilization temperature. These changes in chemical structure pose adverse impacts on soot oxidation reactivity, especially for early-stage soot. With increased degree of maturity, soot gradually shows almost overlapped TG curves under all investigated cases. The distributed activation energy model (DAEM) is used to analyze soot oxidation reactivity by decoupling two interrelated processes, i.e. low-temperature conversion and carbonaceous substances oxidation. After devolatilization, the resulted soot samples have narrow reaction temperature ranges in TG curves and higher activation energies. Among the three selected devolatilization temperatures, 650 °C can effectively remove VOF and retain reactivity features of soot sampled at different sampling positions or residence times.

Evolution of structure and oxidation reactivity from early-stage soot to mature soot sampled from a laminar coflow diffusion flame of ethylene

This work investigated the structure and oxidation reactivity of soot sampled from a laminar coflow diffusion flame of ethylene. A capillary-nozzle-hybrid sampling method was developed to extract soot from five sampling positions along flame axis, covering both early-stage and mature soot samples. The results reveal that residence time plays an important role in modifying surface functional groups. Oxygenated and aliphatic groups gradually disappear, soot structure becomes more organized. As a consequence, the rate of mass losses is impaired during thermo-chemical conversion. The derivative thermogravimetry (DTG) results show that oxidation of early-stage soot can be separated into low-temperature (low-T) conversion and carbonaceous substances oxidation processes. The former process including both volatile organic fraction (VOF) releasing and early oxidation reactions generates the first maximum mass loss rate at about 510 °C, while the latter forms the second maximum mass loss rate at about 600 °C. Recognizing that the two processes are partially merged, the distributed activation energy model (DAEM) was introduced to decouple the bimodal behavior of DTG curves. The DAEM results reveal that with increased degree of soot maturity, relative contribution from low-T conversion process decreases abruptly, and DTG curve eventually becomes unimodal and can be well simulated by considering only carbonaceous substances oxidation process.

Application of sectionalized single-step reaction approach (SSRA) and distributed activation energy model (DAEM) on the pyrolysis kinetics model of upstream oily sludge: Construction procedure and data reproducibility comparison

As the dominant hazardous waste discharged from petroleum industry, the pyrolysis features of the upstream oily sludge (UOS) were scrutinized by way of TGA/DSC. The pyrolysis kinetics model of UOS was systematically constructed by sectionalized single-step reaction approach (SSRA) and distributed activation energy model (DAEM), and the data reproducibility was further evaluated. The results showed that when the pyrolysis operation temperature interval was set from 380 K to 1170 K, two weigh loss step, two endo/exothermic regions and three significant mass-loss peak were respectively emerged in TG, DSC and DTG curves, based on which the TG curves could be sectionalized into three stages. Attributing to the ∆E/Eα¯ value of each stage was higher than 10% but lower than 20% derived from the activation energy assessment, it is not only revealed three multi-step reactions were carried out in sequence with an individual dominant single-step reaction which was sufficient for the SSRA utilization, but also displayed a well fitted by the Gaussian distribution which satisfied the requirement of DAEM implementation. Based on the five-step construction procedure introduced in this paper, pyrolysis kinetics model of UOS could be successful established and interpret as SSRA-based and DAEM-based piecewise function. The latter exhibited a better performance on the data reproduction than the former because the nRSS value of the reproduced data derived from DAEM-based model was lower than 1.86%. The higher mathematical flexibility of DAEM-based model function was the major attribution to a better data reproducibility, also, it possessed a potential ability in predicting the reaction rate at an arbitrary reaction temperature once the heating ratio was preset.

A comprehensive study on the oxidative pyrolysis of epoxy resin from fiber/epoxy composites: Product characteristics and kinetics

Thermal treatment has been the most feasible process to recycle valuable carbon fibers and obtain fuel and chemicals from waste fiber/epoxy composites. The present work studied the oxidative pyrolysis behaviors of epoxy resin from fiber/epoxy composites using a thermogravimetric apparatus and a fixed-bed reactor, respectively. The effects of various O2 concentrations on the thermal behaviors of epoxy resin were investigated and the product characteristics were analyzed. Furthermore, a multi distributed activation energy model (multi-DAEM) was first developed to determine the oxidative pyrolysis kinetics of epoxy resin under various atmospheres. Results showed that the degradation behaviors of epoxy resin were largely altered by the O2 concentrations. High O2 concentrations accelerated the primary decomposition of epoxy resin and shifted the oxidation of resin residue into lower temperatures. High contents of methylcyclohexene and phenolic derivatives were detected in liquid products. In air atmosphere, high yields of CO and CO2 were generated and distributed in several stages. The kinetic analysis indicated that the multi-DAEM method can well explain the oxidative pyrolysis behaviors of epoxy resin. A minimum six-reaction fitting process can perfectly simulate the oxidative pyrolysis of epoxy resin. The predictions for various O2 concentrations were in good agreement with the experimental tests.

Investigations on Mediterranean biomass pyrolysis ability by thermogravimetric analyses: thermal behaviour and sensitivity of kinetic parameters

A comparison of the thermal behaviours of different Mediterranean biomasses, based on the evaluation of their pyrolysis characteristic temperatures, their reactivity and kinetic parameters is presented. Parameters such as the activation energy and the pre-exponential factor of the pyrolysis reactions are determined by different methods (Kissinger, Kissinger–Akahira–Sunose [KAS], Coats–Redfern, nonlinear least-squares minimization [NLSM] and model distributed activation energy model [DAEM]). Furthermore, a sensitivity analysis of the kinetic parameters based on different methods is conducted. The comparison of this work with the literature, showed that thermal characteristic parameters determined using the thermogravimetric analysis (TGA) are often neglected and not used in biomass pyrolysis at laboratory scale. The kinetic parameters seem to be highly sensitive to the used kinetic methods. For a given biomass, such as the Aleppo pine husk residue, for example, the activation energy can vary from 65.80 to 197.08 kJ·mol -1 depending on the used method. For this biomass, the highest average activation energy (190 kJ·mol -1 ) was estimated by the KAS and DAEM methods. The Kissinger method yields to an activation energy close to that of cellulose calculated by the NLSM method. For all biomasses, the activation energy remains between 150 and 200 kJ·mol -1 except for the Coats–Redfern method, where this value is in the range of 50–100 kJ·mol -1 . Therefore, it is important to have a means of recommending the most appropriate method for the determination of kinetic parameters.

Distributed Activation Energy Modelling Using a Parabolic Heating Profile

Abstract This work investigates the thermal decomposition of forest waste for a non-linear temperature distribution inside the pyrolysis reactor. Quantitative analysis of the distributed activation energy model is explained graphically. It has been assumed that thermal profile varies according to the general parabolic equation with the initial condition (0, T 0). The approximated solution of the non-analytical integral is determined by the Laplace integral method. The integral limit for the distributed activation energy model (DAEM) is found to vary from 211 to 810 kJ·mol−1; whereas the frequency factor (the first-order reactions) for the corresponding range of the activation energy lies in the domain of 400–2000 min−1. The acceleration in the char formation has been found for the reactions other than that of the first order.

Kinetic models and distribution of activation energy in complex systems using Hopfield Neural Network

The knowledge about the thermal behavior of solids is crucial to chemically characterize the products, especially when they are applied in industries as solid fuels. The kinetic studies allow us to accurately predict the thermal processes and are of great value for industries. In complex systems, more than one reaction occurs during the thermal process and the activation energy should be considered as a distribution of the activation energy model (DAEM), or could be determined from the combination of kinetic models, instead of an average parameter for the entire event. The DAEM is equivalent to an ill-conditioned inverse problem and in this work, the Hopfield neural network (HNN) is proposed. Firstly, the HNN algorithm was investigated using simulated data, and after it was tested using experimental data of a Brazilian petroleum coke sample. The HNN results were confronted with the results from the Levenberg-Marquardt algorithm, considering the DAEM and kinetic models determination. The HNN results showed this methodology is more efficient to treat this kind of problem and additionally it was compared with isoconversional methods.

Study of pyrolysis and combustion kinetics of oil sludge

ABSTRACT In order to deal with the shortage of oil and natural gas, the supplement energies, such as oil sludge, waste plastics, waste rubber needed to be studied. The pyrolysis and combustion methods have advantages when they are chosen to treat oil sludge. The investigation of kinetics is significantly important to know the kinetic parameters and the reaction mechanisms and to provide important theoretical basis for the process design of pyrolysis and combustion to treat oil sludge. Most previous studies on pyrolysis and combustion kinetics of oil sludge regarded pyrolysis process or combustion process, and rarely split pyrolysis or combustion process to calculate kinetic parameters separately. In this work, the experiment of pyrolysis and combustion were carried out by thermal gravimetric analyzer. After splitting the pyrolysis and combustion processes into two stages, respectively, the methods of Coats-Redfern and distributed activation energy model (DAEM) were used to calculate the kinetic parameters. Based on the results of thermogravimetric analysis, the pyrolysis and combustion process can be divided into two stages. For the pyrolysis process, the first stage is mainly with the evolution of adsorbed volatile hydrocarbon and the rupture of weaker chemical bond and the second stage is the cracking of organic macromolecules. Meanwhile, in the first stage of combustion process, small molecular organic matter in dry basis oil sludge will volatilize and then burn on the surface of the crucible and the gas phase outside the crucible, and in the second stage, macromolecular organic matter will volatilize, pyrolyze and burn, and the diffusion of oxygen into the crucible will cause the fixed carbon to burn. According to the kinetic results of the pyrolysis process, the activation energy of the first stage calculated by the Coats-Redfern model are all less than 40 kJ/mol, and that of the second stage increases from 148.14 kJ/mol to 184.97 kJ/mol with the increase of the heating rate. The results of DAEM model show that with the increase of the conversion rate, the activation energy of the first stage increases from 60.82 kJ/mol to 81.05 kJ/mol, and that of the second stage increases from 120.60 kJ/mol to 237.07 kJ/mol. For the combustion process, the activation energy calculated using Coats-Redfern model decreases from 120.18 kJ/mol to 73.48 kJ/mol in the first stage, and that of the second stage is relatively low. The results of DAEM model show that with the increase of the conversion rate, the activation energy decreases from 129.53 kJ/mol to 62.36 kJ/mol in the first stage and that in the second stage is stable at about 70 kJ/mol.

Quantitative hydrocarbon generation and charge risk assessment in the NW Persian Gulf: A 3D basin modeling approach

Three-dimensional basin and petroleum system modeling was conducted to investigate hydrocarbon generation, migration, and accumulation in the Iranian sector of the NW Persian Gulf. The presented basin model was developed based on seismic and well data covering an area of about 20,000 km2 bounded by the base-Triassic and the present-day sea-floor. Hydrocarbon generation modeling uses newly developed discrete activation energy distributions for Albian source rocks. This study provides a key to the understanding of the Cretaceous-Tertiary petroleum systems and hints to the possible causes of exploration failure at few places. This can reduce future charge-related exploration risk in the region especially for the stratigraphic and combined structural-stratigraphic traps.The modeling results indicate the major role of the Zagros orogeny on controlling burial and thermal evolution as well as hydrocarbon migration and accumulation. The Zagros orogeny and following reactivation of the deep-seated faults resulted in the creation of two depressions in the region hosting the main hydrocarbon generation kitchens for the Cretaceous source rocks. The direction of hydrocarbon migration and accumulation is mainly controlled by the kinematics of the structural highs. During the Late Cretaceous to Miocene, southward deepening of the basin directed most hydrocarbon migration towards the northern part. The latest phase of the tectonic activity during the Miocene and tilting and deepening of the horizons towards the NE resulted in changing the direction of hydrocarbon migration towards the southern part. The results show that the rather young petroleum accumulations related to the Late Miocene to recent Zagros movements can hardly been understood without considering filling of former structures and re-migration due to tectonic restructuring.

Study on thermochemical characteristics properties and pyrolysis kinetics of the mixtures of waste corn stalk and pyrolusite

As an alternative energy source for fossil energy, use of biomass pyrolysis to reduce pyrolusite is of great significance for energy conservation, emission reduction and environmental protection. Kinetics and thermodynamics of reducing pyrolusite using biomass pyrolysis was studied using thermogravimetric analysis analysis. Five non-isothermal methods, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Distributed Activation Energy Model, Starink and Friedman, were employed to calculate the pyrolysis kinetics and thermodynamic parameters. The results showed that pyrolusite reduction by biomass pyrolysis can be divided into four stages: drying stage (30–175 °C), rapid pyrolysis reduction stage (175–350 °C), slow pyrolysis reduction stage (350–680 °C) and char formation stage (680–900 °C). The apparent activation energy, reaction enthalpy, Gibbs free energy and entropy change of pyrolusite reduction by biomass pyrolysis was calculated ranges from 170 to 180 kJ/mol, 164 to 174 kJ/mol, 136.97 to 137.25 kJ/mol and 45.67 to 61.91 J/mol·K, respectively. This work provides theoretical basis and practical guidance for the reduction of pyrolusite by waste corn stalk.

Thermal conversion behavior of paper mill sludge: characterization, kinetic, and thermodynamic analyses

The present paper reports the pyrolysis behavior, kinetic, and thermodynamic parameters of paper mill sludge (PMS), which is a paper manufacturing residue and cannot be re-evaluated, at three heating rates (5, 10, and 20 °C min−1) under non-isothermal conditions. Ultimate and proximate analyses of the paper mill sludge were carried out. Kinetic and thermodynamic parameters were calculated using four model-free methods; Flynn-Wall Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose (KAS), and distributed activation energy model (DAEM). High R2 values revealed that all models are compatible with TGA data. The activation energy calculated (101.01 kJ mol−1) from FWO was higher than the other three methods. Pre-exponential factor values ranged from 0.56 × 103 and 14.55 × 103 s−1 for all methods. Kinetic and thermodynamic findings will be beneficial in terms of the process design of PMS pyrolysis.

Kinetics and thermodynamics of microalgae residue oxidative pyrolysis based on double distributed activation energy model with simulated annealing method

Non-isothermal thermogravimetric analysis (TGA) at four heating rates of 10, 20, 30 and 40 K min−1 under oxidative atmosphere was employed to investigate the characteristics of microalgae residue oxidative pyrolysis. The double distributed activation energy model (DAEM) was used to analyze the oxidative pyrolysis kinetics of microalgae residue and the simulated annealing method was employed for the estimation of the model parameters. The results showed that the double DAEM could describe the kinetic experimental data of microalgae residue oxidative pyrolysis very well whilst the simulated annealing method was effective for determining the kinetic parameters of the double DAEM. The kinetic process of microalgae residue oxidative pyrolysis could be considered as two partially overlapped pseudo-sub-processes. The mean values of activation energy distributions were 179 and 259 kJ mol−1 for the first and second pseudo-sub-processes. The thermodynamic parameters of microalgae residue oxidative pyrolysis processes at the different heating rate were studied based on the obtained kinetic parameters.

Effect of the swelling degree on the non-isothermal dehydration kinetics of a poly(acrylic acid)-g-gelatine hydrogel.

The kinetics of non-isothermal dehydration of a poly(acrylic acid)-g-gelatine hydrogel swollen to different swelling degrees is investigated. The thermogravimetric curves are recorded at different heating rates in the interval from 5 K mol-1 to 20 K mol-1 within the temperature range from ambient temperature to 480 K. It is found that all kinetics curves can be described using the Weibull function. Based on the suggested kinetics model, the values of the specific rates are calculated and the values of apparent activation energies are established. Distribution functions of activation energies are obtained. The changes found in the values of Weibull function parameters, dependences of the specific rate on temperature, and apparent activation energies on temperature and the dehydration degree, as well as different activation energy distributions, are explained using the fluctuation model of a hydrogel, as a dynamically disordered system that goes through changes during the dehydration process. The presented results can have both fundamental and practical significance in the fields where the application is based on the ability of the hydrogel to conserve and slowly release water.

Kinetic analysis and pyrolysis behavior of low-value waste lignocellulosic biomass for its bioenergy potential using thermogravimetric analyzer

A substantial amount of renewable feedstocks study has been dedicated to bio-fuel and biochemical generation, preferably thermochemical conversion processes such as pyrolysis. In this work, the physicochemical study, pyrolysis behaviouer and kinetic parameters of Cascabela thevetia (SK) Delonix regia (SG) and Manilkara zapota (CK) seeds were tested in the thermogravimetric analysis (TGA) at three rates of heating (10–50 °C min−1) to estimate its bioenergy potential. Further, the kinetic constraints were investigated by using model-free approaches, namely Kissinger-Akahira Sunose (KAS), Friedman model (FM), Cots-Redfern model (CR), Distributed Activation Energy Model (DAEM), Ozawa-Flynn-Wall (OFW), and Vyazovkin method (VZ). Characterization study of applied biomass showed an attendance of extensive amount of volatile matter (73.15–75.24%), carbon content (50.12–55.02%), heating value (20.52–25.12 MJ kg−1), and lower ash content (2.20–3.15%) and nitrogen content (3.01–5.10%). Further, DSC inspection of applied biomass recognized that biomass decayed under the endothermic process during the heating process. The average activation energy for CK, SG, and SK was originated to be 157.81, 150.90, 166.28 kJ mol−1 for KAS, 164.55, 166.59, 177.05 kJ mol−1 for OFW, 168.47, 166.05, 185.22 kJ mol−1 for FM, 194.87, 157.87, 199.74 kJ mol−1 for DEAM and 168.75, 158.86, 102.28 kJ mol−1 for VZ respectively. Additionally, CR model yields 49.99, 35, 38.71 kJ mol−1 at n = 1 and 34.79, 29.18, 27.7 kJ mol−1 at n ≠ 1 for CK, SG, and SK, respectively. Finally, the variation between activation energy and enthalpy of reaction showed promising product formation. In contrast, Gibbs free energy and higher heating value (HHV) of biomass exhibited its potential for energy and fuel production.