Isoconversional Method Research Articles

Pyrolysis behavior of sewage sludge coexisted with microplastics: Kinetics, mechanism, and product characteristics

Microplastics can accumulate in the excess sludge from wastewater treatment plants through domestic wastewater. This study investigated the co-pyrolysis behavior of sewage sludge coexisting with two types of microplastics (polyethylene (PE) and polylactic acid (PLA)) and found a superior comprehensive pyrolysis performance. By calculating the difference between theoretical and experimental weight loss during the pyrolysis process, it was found that the incorporation of microplastics PE and PLA created a synergistic effect at 270°C–450 °C, which was confirmed through the Malek method analysis from a pyrolysis mechanism perspective that it could increase the random nuclei on each particle, that is, enhance the heterogeneous diffusion of volatiles. The average activation energy was reduced by 84.99 kJ/mol, as determined using three isoconversional methods: Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink. Regarding the products, the aforementioned synergistic effect led to a reduction in char retention and larger specific surface area of the biochar, while the quantities of gaseous products and bio-oil escalated. Through a thermogravimetric analyzer and Fourier transform infrared spectroscopy (TG-FTIR), an increase in aromatic hydrocarbons, alkanes, aldehydes, ethers, and esters in the gaseous products were detected. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) revealed an increase in hydrocarbons, esters, and alcohols in the bio-oil, and acids and aldehydes decreased, overall enhancing the quality of the bio-oil. This study elucidated that pyrolysis completely transformed microplastics in sludge, thus eliminating environmental risks and provided a theoretical reference for understanding the pyrolysis behavior of sludge containing microplastics.

Investigations on the effect of kaolin catalyst on the yield of various products obtained from pyrolysis of low-density polyethylene (LDPE) wastes and reaction kinetics.

The pyrolysis characteristics of low-density polyethylene (LDPE) wastes were investigated in a batch pyrolyzer in the temperature range of 550-650°C for a varying heating rate (5, 10, 15, 20, and 25°C/min) alone and using kaolin catalyst (10, 15, and 20% w/w). The yield distribution of various products under varying operating conditions was investigated, and the corresponding favourable conditions for maximum yield of pyrolytic oil (PO) were identified. The possible effect of the catalyst on pyrolysis kinetics was explored by extracting activation energies from the TGA experiments. The various model-free iso-conversion methods estimated the activation energy of 162-166kJ/mol during thermal degradation of LDPE, while it shifted to a lower range (138-145kJ/mol) on catalytic treatment. The catalytic pyrolysis with a 20% (by mass) catalyst in a batch pyrolyzer provided the maximum PO yield with the least solid residue at 600°C using a heating rate of 20°C/min, while the temperature of 600°C with 10% catalyst showed the least liquid product with more solid residue. The presence of a catalyst improved the oil quality with transparency and lower viscosity due to lighter hydrocarbons and higher aromatic content. The FTIR analysis detected various organic groups-alkanes, alkenes, cyclic, and aromatics in the oil. GC tests of gaseous products confirmed the gases like hydrogen, propane, butane, and propylene. The present study aims to provide technical know-how for the effective utilization of LDPE wastes towards clean energy sources and create a plastic-free green environment.

Assessment of isoconversional methods and peak functions for the kinetic analysis of thermogravimetric data and its application to degradation processes of organic phase change materials

Assessment of isoconversional methods and peak functions for the kinetic analysis of thermogravimetric data and its application to degradation processes of organic phase change materials

Determination of the apparent activation energy surface from isothermal data of char combustion and gasification

In this paper, the apparent activation energy (AAE) surface was determined by using isothermal data of char combustion and gasification and the apparent Arrhenius equations where the activation parameters depended on temperature and conversion. The dependence of the logarithm of the reaction rate on temperature and conversion was described by the empirical polynomial to increase the accuracy of fitting and the AAE was calculated by the isoconversional method and the fitting of reaction rate and conversion. The AAE surfaces determined for the four examples of char combustion and gasification varied considerably and differently from each other with temperature and conversion. This provides new information for a better understanding of these processes and their kinetic models.

Monitoring in-situ dissolution of polystyrene-acrylonitrile (SAN) via calorimetry and spectroscopy

Dissolution/precipitation recycling is an environmentally friendly solution that could be potentially implemented for ABS recycling. In this paper, a set of useful calorimetric, spectroscopic, and rheological techniques and methods are presented to monitor in-situ the dissolution of the ABS matrix: poly(styrene-acrylonitrile) (SAN). In line with the Hansen solubility parameters, methyl ethyl ketone (MEK) has been selected to be a suitable solvent for SAN dissolution. Thermodynamic and kinetic aspects of the dissolution process were investigated by using calorimetry and in-situ ATR-FTIR spectroscopy. Through an isoconversional method, the effective activation energy and the main steps involved in the dissolution process were determined. A rheological characterization of the solution SAN-MEK was also performed to provide further information on the rheological behavior.

Unveiling the impact of nitrocellulose-enveloped nCuO on the thermal characteristics of ammonium nitrate-based solid composite propellants utilizing polyurethane/nitrocellulose blend binders

ABSTRACT This study investigates the combined effects of coated nano copper oxide (NC@nCuO) and polyurethane (PU) modification on the thermal degradation kinetics and combustion properties of ammonium nitrate-based solid composite propellant. Nitrocellulose (NC) is used as a coating for nCuO, forming a core-shell structure, and as a binder in a PU/NC blend. Surface modification of ammonium nitrate was achieved through repeated spray coating. The formulations underwent thorough thermal characterization using thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses. TG analysis showed a significant decrease in thermal degradation temperature due to AN modification with NC@nCuO and the use of PU/NC as a binder. Isoconversional kinetic methods (it-KAS, it-FWO, and VYA/CE) based on DSC tests were used to predict kinetic parameters, revealing a substantial impact of NC-coated nCuO and PU modification on the reactivity of the propellant, reducing the activation energy from 125 kJ/mol (reference) to 99 kJ/mol (nCuO) and 94 kJ/mol (NC@nCuO). Additionally, combustion tests were conducted. The results showed that the introduction of nCuO reduces the ignition delay by 5.25 ms and the combustion duration by 0.06 ms, while NC@nCuO further reduces these by 8.17 ms and 0.12 ms, respectively. Additionally, there is a 23% and 65% increase in flame intensity relative to the reference formulation after the incorporation of nCuO and NC@nCuO, repectively.

Co-pyrolysis of Sewage Sludge with Distillation Residue: Kinetics Analysis via Iso-conversional Methods

Co-pyrolysis of Sewage Sludge with Distillation Residue: Kinetics Analysis via Iso-conversional Methods

Investigation of kinetics, reaction mechanisms, thermodynamics, and synergetic effects in co-pyrolysis of wood sawdust and linear low-density polyethylene using the thermogravimetric approach.

This study focused on investigating thermal degradation behaviors, kinetics, reaction mechanisms, synergistic effects, and thermodynamic parameters of wood sawdust (WSD), linear low-density polyethylene (LLDPE), and their blends (LW1:3, LW1:1, and LW3:1) during co-pyrolysis in a thermogravimetric analyzer (TGA). Thermal behavior exhibited a LW1:3 blend (25 wt.% LLDPE) showing significant mass loss at lower temperatures (150 to 300°C) compared to the individual feedstocks, such as 150 to 400°C and 300 to 520°C for WSD and LLDPE, respectively. The iso-conversional methods (KAS, FWO, and FM) were used to determine the kinetic parameters (Ea and A), and the activation energy drop was highest for the LW1:3 blend. According to the master plots, the third-order reaction (O3), nucleation (P2/3), and diffusional model (D4) were the predominant reaction mechanisms for the co-pyrolysis of the LW1:3, LW1:1, and LW3:1 blend, respectively. The thermodynamic parameters demonstrate that a small amount of plastic addition into WSD can improve the reactivity of the blend, shorten the reaction time, and cause less energy-intensive reactions. The values of ΔH, ΔG, and ΔS also confirmed the co-pyrolysis process's spontaneity and endothermic nature. The Fourier transforms infrared spectrometer (FTIR) spectra of raw feedstock, blends, and their biochar revealed some of the peaks were shifted, the intensity was reduced, and disappearance can happen when the temperature was increased. Using the experimental and theoretical/predicted activation energies, the parity chart illustrates the synergistic effects of co-pyrolysis of different blends, and the LW1:3 blend has a favorable synergistic impact. These results could be helpful in process optimization and designing an effective reactor system for co-pyrolysis.

Cross-Linking Reaction of Bio-Based Epoxy Systems: An Investigation into Cure Kinetics.

The cure kinetics of various epoxy resin mixtures, comprising a bisphenol epoxy, two epoxy modifiers, and two hardening agents derived from cardanol technology, were investigated through differential scanning calorimetry (DSC). The development of these mixtures aimed to achieve epoxy materials with a substantial bio-content up to 50% for potential automotive applications, aligning with the 2019 European Regulation on climate neutrality and CO2 emission. The Friedman isoconversional method was employed to determine key kinetic parameters, such as activation energy and pre-exponential factor, providing insights into the cross-linking process and the Kamal-Sourour model was used to describe and predict the kinetics of the chemical reactions. This empirical approach was implemented to forecast the curing process for the specific oven curing cycle utilised. Additionally, tensile tests revealed promising results showcasing materials' viability against conventional counterparts. Overall, this investigation offers a comprehensive understanding of the cure kinetics, mechanical behaviour, and thermal properties of the novel epoxy-novolac blends, contributing to the development of high-performance materials for sustainable automotive applications.

Thermokinetics and reactive mechanism of lead azide (LA) in atmosphere/temperature mixed environment

To establish the influence of atmospheric and temperature factors on the stability of LA, a combined environmental stress testing device was designed to simulate reaction characteristics. Morphological characterization methods of SEM and FTIR were carried out to explore the changes of crystal structure, as the pyrolysis behavior of LA under the combined environmental stress was investigated by DSC with two isoconversional kinetic methods and thermal safety software (TSS). The research indicates that CO2 and H2O react with LA to generate basic lead carbonate in the air atmosphere, together with the stimulation of thermal stress, the synergistic effect formed microvoids to erode the crystal structure of LA. The microvoid effect reduced the apparent activation energy (Ea) from 156.47 to 29.52 kJ/mol as the order of degradation of thermal stability of LA was Air > N2 > CO2, which demonstrated that CO2 and N2 atmosphere have a particular protective effect for LA storage, transportation, and application. The pyrolysis reaction mechanism model of LA under the combined environment factors testing was the same as the original LA through the calculation of TSS, thereby the findings could contribute to a better understanding of available boundary conditions for LA.

Deciphering the role of FI catalyst’s C3 substituent on the non-isothermal crystallization kinetics of nascent disentangled UHMWPE

UH1 - UH4 were accessed using tetra-fluorinated phenoxy-imine catalysts (FI catalysts) with linear (allyl, n-propyl, 1-propenyl) or more steric demanding (isopropyl) C3 substituents ortho to the phenoxy-oxygen atom. To get a better understanding of the non-isothermal crystallization kinetics of these nascent ultra-high molecular weight polyethylenes (UHMWPEs), their thermo-rheological properties are investigated. Through the application of annealing-crystallization-melting thermal analysis and isoconversional method, it is verified that the samples are nascent disentangled UHMWPEs with higher crystallization rates compared to the commercial UHMWPE (CUH). The molar fraction of nascent entangled crystals and/or degree of supercooling have a significant influence on the non-isothermal crystallization kinetics of nascent disentangled UHMWPEs. Finally, under a lower supercooling, the electron-donating property and steric hindrance of C3 substituent strongly affect the synthesis and architecture of polyolefin which in turn has a specific non-isothermal crystallization kinetics.

Exploring the curing kinetics of Acrolein-Pentaerythritol resin: Impact of molecular weight and molecular weight distribution on cure behavior

Curing kinetics are crucial for designing and optimizing the process parameters of a resin. This study examines the non-isothermal curing kinetics of acrolein-pentaerythritol (APE) resins, focusing on the impact of molecular weight (MW) and molecular weight distribution (MWD) on their cure behavior. Kinetic parameters were determined using isoconversional and combined kinetic analysis methods through microcalorimeter measurements. The findings suggest that the cure process follows the nucleation and growth models (Avrami−Erofeev equation), with an activation energy of 72.2 kJ/mol. A comparison of two APE resins with different molecular weights and molecular weight distributions reveals that higher MW components expedite the initial curing reaction but impede the main curing process, leading to extended curing durations. This study provides valuable insights into the curing kinetics of APE resin and the influence of MW and MWD, contributing to the reliable and reproducible production of composite parts.

Thermal stability, preformulation, and kinetic degradation studies for gestrinone

AbstractGestrinone is an active pharmaceutical ingredient used in the treatment of endometriosis as capsules, with ongoing evaluation for intravaginal administration, while also having been studied for its potential antitumoral effects. The purpose of this study was to determine the compatibility of gestrinone with four excipients used in the development of solid pharmaceutical formulations (α-lactose monohydrate, magnesium stearate, starch, and talc) and to obtain a fully characterized thermoanalytical profile of gestrinone with the help of kinetic analysis. Preformulation studies were carried out on 1:1 mass/mass binary mixtures between gestrinone and each excipient by instrumental screening under ambient conditions using ATR-FTIR spectroscopy investigations, and later by studying the effect of thermal treatment over the samples (TG/DTG/DSC). The obtained results suggest that under ambient conditions, no chemical interactions take place between the active pharmaceutical ingredient and selected excipients, whereas under thermal stress incompatibilities are observed in all systems. The mechanism of decomposition was preliminary evaluated by the ASTM E698 and later completed by the isoconversional methods of Friedman, Kissinger–Akahira–Sunose, and Flynn–Wall–Ozawa, which suggest similar mean activation energies. The mechanism of decomposition was elucidated in the last part of the study, by employing the modified NPK method. This method suggests that gestrinone is thermally degraded by the contribution of two individual processes, both consisting of superimposed physical transformations and chemical degradations.

Synergistic effect of TiO2 nanoparticles and poly (ethylene-co-vinyl acetate) on the morphology and crystallization behavior of polylactic acid

The impact of adding ethylene vinyl acetate copolymer (EVA 80) and 1 wt% TiO2 nanoparticles on the morphology and crystallization behavior of poly(lactic acid) blends was investigated using DSC, SEM, and POM. Thermal analysis revealed the enhancement of crystallinity of PLA in the presence of TiO2 and higher EVA 80 content in the blend. The PLA and EVA 80 components showed compatibility, as evidenced by the shift of the glass transition temperatures of the PLA phase in the blend to lower values compared to neat PLA. The lower temperature shift of the cold crystallization of the PLA and the formation of the small spherulites of the PLA in the blends indicated that the EVA 80 and TiO2 act as a nucleating agent for crystallization. The non-isothermal crystallization parameters of the composites were evaluated using Avrami's modified model, the MO approach, and Friedman’s isoconversional method. The Avrami’s modified rate constant (K) and the effective activation energy values significantly increased with the incorporation of EVA 80 and TiO2 nanoparticles. Furthermore, the thermogravimetric analysis (TGA) showed improved thermal stability of PLA by adding EVA 80 and TiO2.

Pyrolysis kinetic analysis and model constructions of different ranks of coal and validation by GA–BP neural networks

In the current steel industry, environmental pressures are mounting. If the reducing gases generated from coal pyrolysis can be utilized for reducing iron ore, the goal of low-carbon production with controllable costs can be achieved. However, the release of volatile content in coal has a significant impact on the pyrolysis process and final products. Therefore, in this study, the pyrolysis characteristics and gaseous products of four types of coal with different volatile matter content was investigated by thermogravimetry-mass spectrometry (TG-MS) technology. The results showed that coals with higher volatile matter content demonstrated stronger reactivity during pyrolysis. As the volatile matter content in coal increased, the starting temperature for releasing the reducing gases decreased, leading to a significant increase in the released gas volume. In addition, the three kinetic factors were calculated by isoconversional method, distribution of the activation energy model (DAEM) and Coats-Redfern (CR) method respectively, and the pyrolysis reaction mechanism function suitable for all coal types was reconstructed based on common solid reaction models. Finally, a predictive model based on a GA-improved back-propagation neural network (BPNN) was developed, which useing 21 input parameters to predict the TG curves, activation energy (E), lnA and mechanism function (fα) and achieving R2 values above 0.95. This study contributes to a comprehensive understanding of the pyrolysis mechanism of coals with different volatile matter content, providing scientific guidance for effective utilization.

Experimental and kinetic study of PET pyrolysis under fast and slow heating rates using a visualized Macro TGA

A visualized macro thermogravimetric analyzer was utilized to gather data on sample weight, temperature, and image signals of centimeter-scale PET. The PET was subjected to both fast (above 300 K/min) and slow (below 25 K/min) heating rates. The experimental findings revealed that weight loss mainly occurred at different temperature ranges under fast (above 610 °C) and slow (400–520 °C) heating rates. The isoconversional method (ICM) and the distributed activation energy model (DAEM), both assuming single-step reactions, were employed separately to predict the conversion and rate of PET pyrolysis. However, the prediction error was considerable. To address this issue, a discrete distributed activation energy model (DDAEM) was developed, incorporating both single-step and double-step parallel reactions. The DDAEM yielded a prediction error within 10 %, which is better than ICM and DDAEM. Furthermore, all three models (ICM, DAEM, and DDAEM) indicated significant discrepancies in activation energies between fast and slow heating rates.

Effect of ethanolysis on the structure evolution, pyrolysis kinetics, and volatile products of waste poplar sawdust

Ethanolysis had been the promising approach for the deoxygenation of waste poplar sawdust (WPS), and its effect of structure variation and pyrolysis behaviors on the WPS was investigated in present research. The decreasing of C–O chemical bonds and the increasing of C content was typical phenomenon during the ethanolysis of WPS. The pyrolysis behaviors of sample were performed by thermogravimetric analyzer at three different heating rates. The pyrolysis kinetics and thermodynamics of WPS, residue230 (R230), and residue260 (R260) were well determined on the basic of three model-free iso-conversional methods. Average activation energy derived from the Kissinger-Akahira-Sunose (KAS) method of R260 displayed the high value (445.06 kJ/mol), followed by 224.88 kJ/mol for R230, then 200.68 kJ/mol for WPS. Thermodynamics data suggested that R260 required more total energy consumption for the breakage of chemical bonds. Additionally, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) results showed that the highest relative content of volatile products compound derived from the flash pyrolysis of R230 and R260 was 47.12 % (d-Allose) and 38.69 % (Phenols), respectively, and RC value of arenes significantly increased to 15.82 % after ethanolysis. The findings would significantly contribute to the valuable utilization of waste biomass and its residues.

Pyrolysis of high-density polyethylene: Degradation behaviors, kinetics, and product characteristics

Pyrolysis is a promising technology for converting plastic waste into valuable raw materials while offering a potential solution to the global plastic pollution crisis. In this study, the thermal pyrolysis of high-density polyethylene (HDPE) is investigated in a drop tube reactor under nearly isothermal conditions. The impact of reaction temperature and gas/volatile residence time on carbon conversion and product distribution is examined across a range of 500–900 °C and 3.6–32.2 s, respectively. Non-condensable gas products detected by online mass spectrometry are H2, CH4, C2H4, C2H6, C3H6, and C3H8. At elevated temperatures and prolonged residence time, H2 yield reaches as high as 8.6 wt% of the initial HDPE mass due to intensified cracking reactions of C2–C3 hydrocarbons and long-chain aliphatic compounds. Consequently, pyrolysis tars consist mainly of polycyclic aromatic hydrocarbons (PAHs) with 5–7 rings, accompanied by visible coke deposition within the reactor. HDPE decomposition to volatiles is an endothermic process and it is complete at a temperature between 492 °C and 525 °C, depending on the heating rate employed, from non-isothermal thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) measurements. The thermal degradation of HDPE pellets follows the two-dimensional nucleation growth model for conversion levels up to 0.8 with an apparent activation energy of 259–270 kJ/mol and a pre-exponential factor of 4.83 × 1017–1.37 × 1019 min−1, determined from various isoconversional methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink, along with Criado's master plots. These findings provide valuable insights into optimizing process parameters and refining reactor design for pyrolysis, which can be integrated with gasification and reforming processes to enhance hydrogen production on a larger scale.

Effect of the accelerated aging process on the thermal decomposition of LiAlH4-based composite solid propellants

In the present work, a study was carried out on the effect of the accelerated aging process on the thermal decomposition of two composite solid propellants based on ammonium perchlorate (AP) and hydroxy‑terminated polybutadiene (HTPB). The first one (CP1) was enriched with aluminum (Al) powders, while the second (CP2) contained a mixture of aluminum and lithium alanate (LiAlH4) as a high-energy fuel additive. The thermal properties of the investigated propellant samples were determined using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The obtained results clearly demonstrated the effect of the aging process on the thermal degradation of the aged samples compared to the unaged ones, by shifting the temperature peaks of their main decomposition step to lower temperatures with a decrease in their DSC heat release. In addition, the residual unburnt propellant was increased, particularly for the complex metal hydride-based propellant. Kinetic modeling of the main thermal degradation phase, applying two advanced isoconversional methods, revealed a significant decrease in activation energy for the aged samples. Furthermore, the three-dimensional diffusion model involved during the investigated decomposition phase of the unaged samples was changed to a random nucleation model after 60 days of aging time.

Fabrication of Polycaprolactone-Based Polyurethanes with Enhanced Thermal Stability.

The benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO2 nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO2 NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO2 NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO2 NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO2 NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO2 NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO2 NPs on the thermal stability and aging resistance of PU.