Mean Activation Energy Research Articles

Bioenergy potential from Ecuadorian lignocellulosic biomass: Physicochemical characterization, thermal analysis and pyrolysis kinetics

Lignocellulosic biomass offers a sustainable and renewable method for producing high-quality fuels and value-added chemicals. In this study, residues from peach palm (top, inner sheath, and meristem), sugarcane (top), and pineapple (mother plant) were characterized based on their physicochemical properties and thermal degradation behavior to estimate their bioenergy potential. The biomass residue kinetic constraints were analyzed using three isoconversional models: the Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and differential Friedman (DF) models. Physicochemical characterization showed the peach palm top's notably high cellulose content of 35.71 ± 0.47 % wt. Calorific values of the residues ranged from 13.73 ± 0.08 to 16.91 ± 0.90 MJ kg−1. X-ray diffraction analysis indicated the carbonaceous and crystalline nature of the biomass residues. Mean activation energy values ranged from 105.02 to 370.10 kJ mol−1 for KAS, 111.50–360.99 kJ mol−1 for FWO, and 108.60–360.27 kJ mol−1 for DF. Finally, thermodynamic analysis revealed the endothermic nature of the pyrolysis process across the entire conversion range for the samples. Overall, these samples demonstrate major potential as feedstock for biorefineries and the development of Ecuador's circular economy.

Kinetics, mechanisms and release of nitrogen-containing components during pyrolysis of Chlorella with potassium hydroxide addition

Pyrolysis integrated with KOH activation is the most frequently used and efficient method for microalgae to produce N-doped porous biochar. However, the effects of KOH to the pyrolysis process of microalgae are still unclear. Thus, the pyrolysis behavior, kinetics and the release of volatiles especially the nitrogen-containing components during Chlorella pyrolysis with KOH addition were investigated in this study. Results showed that KOH significantly changed the pyrolysis behavior by lowering the initial decomposition temperature and reducing the weight mean activation energy. KOH reacted with the solid matrix even at room temperature. CO2 was the dominant gas product, the release of which was postponed by KOH addition. KOH inspired the release of NH3 to lower temperatures (< 400 °C) while the reverse for HNCO. With the increase of KOH, the formation of hydrocarbons in volatiles shifted to higher temperatures while the yield of acids dramatically reduced and even vanished. The release of nitrogen-containing components was greatly inhibited at 600 °C by converting nitrogen in the feedstock to harmless N2. This study provided insights into the pyrolysis mechanisms of microalgae over KOH for biochar production and the essential environmental impact during the process.

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.

Unlocking biosolid pyrolysis: Towards tailored biochar with different surface properties

To develop a thorough understanding of the thermal decomposition process of biosolids and the qualities of biosolid-derived biochar, this study performs a thermogravimetric analysis (TGA) of biosolids and examines the properties of biosolid-derived biochar produced from varying temperatures of pyrolysis. The pyrolysis of biosolid is conducted under varying heating rates (10, 15, 20 and 25 °C/min) until reaching the maximum temperature of 900 °C. The kinetic triplet (kinetic model, activation energy, and frequency factor) at the corresponding conversion point is determined by analysing the TGA results of the biosolids. The thermal degradation of hydrated compounds shows activation energies ranging from 80 to 100 kJ/mol, whereas the thermal decomposition of organic matter in biosolids exhibits activation energies ranging from 120 to 497 kJ/mol. As the temperature increases, the thermal reactions transition from simple surface reactions with frequency factors below 109 s−1 to more complex reactions with frequency factors above 109 s−1. The distributed activation energy model (DAEM) is established using the approximated temperature function and the activation energy distribution functions. The DAEM shows the mean activation energies of 93–128 kJ/mol, 279–287 kJ/mol and 359–377 kJ/mol for activation energy distribution peaks. The standard deviations of the mean activation energies are 30–64 kJ/mol, 23–30 kJ/mol and 23–41 kJ/mol, respectively. As the pyrolysis temperature is raised from 700 °C to 900 °C, both the specific surface area and micropore volume of biosolid-derived biochar increase, from 48.25 m2/g to 65.74 m2/g and 0.0313 cm3/g to 0.0369 cm3/g, respectively. The findings of this study demonstrate biosolid pyrolysis kinetics, which is essential for establishing a pyrolysis facility for biosolid management and producing biosolid-derived biochar with varying qualities.

Non‐isothermal Thermogravimetric Analysis of Peltophorum pterocarpum and Evaluation of Kinetic Triplet

AbstractThe primary focus of the twenty‐first century has been on developing new and cleaner fuels from renewable sources. The increasing availability of renewable energy sources in environment, such as lignocellulosic biomass derived from agricultural and forest residues, has created a plethora of opportunities for biofuel production. For this purpose, the search for appropriate waste biomass source and the design of suitable reactors are very essential, where the latter requires the knowledge of kinetic triplets. These requirements paved the way to the novelty of the present work as a selection of a rarely used biomass source, that is, Peltophorum pterocarpum, and its non‐isothermal thermogravimetric analysis for the evaluation of kinetic triplet of the process. The range of temperature is 298–1173 K attained at heating rates of 10–55 K min−1. Kinetics were estimated using differential Friedman method (DFM), distributed activation energy method (DAEM), Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), and Starink (STK) models. Mean activation energy (kJ mol−1) and pre‐exponential factor (min−1) of pyrolysis process by five models were 183.68 and 1.24 × 1017 for DAEM, 194.28 and 3.08 × 1021 for DFM, 183.68 and 4.40 × 1016 for KAS, 184.12 and 2.12 × 1014 for OFW, and 183.93 and 3.56 × 1016 for STK. Average values of changes in Gibbs free energy, enthalpy, and entropy by five models are 174 kJ mol−1, 178 kJ mol−1, and 0.007 kJ mol−1 K−1, respectively. Criado's master plots revealed distinct reaction pathways during the process for different conversion levels.

Exploring Li-Ion Transport Properties of Li3TiCl6: A Machine Learning Molecular Dynamics Study

We performed large-scale molecular dynamics simulations based on a machine-learning force field (MLFF) to investigate the Li-ion transport mechanism in cation-disordered Li3TiCl6 cathode at six different temperatures, ranging from 25°C to 100°C. In this work, deep neural network method and data generated by ab − initio molecular dynamics (AIMD) simulations were deployed to build a high-fidelity MLFF. Radial distribution functions, Li-ion mean square displacements (MSD), diffusion coefficients, ionic conductivity, activation energy, and crystallographic direction-dependent migration barriers were calculated and compared with corresponding AIMD and experimental data to benchmark the accuracy of the MLFF. From MSD analysis, we captured both the self and distinct parts of Li-ion dynamics. The latter reveals that the Li-ions are involved in anti-correlation motion that was rarely reported for solid-state materials. Similarly, the self and distinct parts of Li-ion dynamics were used to determine Haven’s ratio to describe the Li-ion transport mechanism in Li3TiCl6. Obtained trajectory from molecular dynamics infers that the Li-ion transportation is mainly through interstitial hopping which was confirmed by intra- and inter-layer Li-ion displacement with respect to simulation time. Ionic conductivity (1.06 mS/cm) and activation energy (0.29eV) calculated by our simulation are highly comparable with that of experimental values. Overall, the combination of machine-learning methods and AIMD simulations explains the intricate electrochemical properties of the Li3TiCl6 cathode with remarkably reduced computational time. Thus, our work strongly suggests that the deep neural network-based MLFF could be a promising method for large-scale complex materials.

Hydrochars derived via wet torrefaction of empty fruit bunches: Effect of temperature and time, comparison to oil palm trunks counterpart, and their pyrolysis behavior

In this study, hydrochars derived from the wet torrefaction of empty fruit bunches (EFB) were characterized and compared to those of oil palm trunks (OPT). Then, the kinetics modelling of EFB-derived hydrochars was evaluated and compared with the Distributed Activation Energy Model (DAEM) under logistics distribution via thermogravimetric analysis (TGA) under pyrolytic conditions at different heating rates. Bench-scale pyrolysis of EFB-derived hydrochars were also performed and characterized. This study elucidates the effect of prolonged residence time (3–72 hours) at different temperatures (180–220 °C) on the wet torrefaction of EFB, and comparison to OPT provides an understanding of wet torrefaction mechanisms. The pyrolysis kinetics of EFB-derived hydrochars provide insights into their pyrolysis behavior and their potential in pyrolytic application. Increased temperature and residence time enhanced the higher heating value (HHV) of the hydrochars at the expense of low mass yield. Hydrochars obtained at 220 °C and 72 hours had the highest HHV at 27.4 ± 0.5 MJ kg−1 with a mass yield of 38.3 ± 2 wt%. EFB-derived hydrochars had a higher mass yield than OPT-derived hydrochars. The van Krevelen diagram revealed that dehydration was the primary reaction pathway for EFB and OPT-derived hydrochars. SEM showed the formation of secondary deposits on both EFB and OPT hydrochars. EFB-derived hydrochars obtained at 220 °C and 72 hours had the highest mean activation energy (E0) with a distribution of activation energy (σ) from 176.7 to 181.7 kJ mol−1 and 43.4–49.9 kJ mol−1, respectively. The increased mean and distribution of activation energies were attributed to the lignin-dense structure of the hydrochars. The kinetic parameters of the hydrochars were also independent of heating rates at low heating rates (< 20 °C min−1). The thermal stability of the pyrochars obtained from EFB-derived hydrochars enabled their applications in fields such as carbon support, activated carbon, water purification process, or carbon sequestration.

Mathematical modeling of thin-layer drying kinetics and moisture diffusivity study of apple slices using infrared conveyor-belt dryer.

The drying features of apples at different infrared drying settings were investigated. The drying time, moisture-effective diffusion, and activation energy of infrared dried apples were measured experimentally and statistically as a function of slice thicknesses, radiation intensity, and air velocity. The infrared intensity of 0.225, 0.130, and 0.341W/cm2 , slice thicknesses of 6, 4, and 2mm, and airflow of 0.5, 1.0, and 1.5m/s were used to dry apple slices. The data shows that the drying time reduced as IR increased, but airflow and slice thickness increased. Eight statistical factors were used to compare 11 alternative mathematical drying models. The experimentally acquired drying curves were matched to the thin-layer drying equations. According to the calculations, the Midilli etal. equation had the greatest (efficiency and R2 ) and lowest (χ2 , sum of squared errors, standard error of estimate, standard error, standard deviation of difference) values. As a result, this equation is the best for modeling the drying curves of apple slices across all drying circumstances. The optimum moisture diffusivity value varied from 2.59 to 9.07 × 10-10 m2 /s. The mean activation energy was determined to be 19.02-29.83kJ/mol under various experimental conditions.

Kinetic study of sesame stalk pyrolysis by thermogravimetric analysis

Sesame stalk is a promising agricultural residue for generating renewable bioenergy, but still remains undeveloped on account of the lack of reliable pyrolysis kinetic information. The novelty of present work lies in that it gives the first thorough examination of kinetic and thermodynamic parameters for pyrolysis of sesame stalk. Non-isothermal pyrolysis experiments in N2 via thermogravimetric analysis were conducted at 5–20 K/min with temperatures programmed from 350 to 900 K. Experimental results indicate that pyrolysis of sesame stalk seems to occur in multi-stage reactions, model-free kinetic analysis methods, including differential Friedman, integral Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Vyazovkin-Dollimore methods, are isoconversionally attempted to perform kinetic analysis of two-stage sesame stalk pyrolysis, respectively resulting in the mean activation energy of 136, 125, 128 and 125 kJ/mol for stage I and 140, 146, 150 and 146 kJ/mol for stage II. The master-plots method and differential composite method are integrated for determining pyrolysis mechanism, and the Ginstling−Brounshtein model is found to be the most appropriate and verified very well by experimental results. The averaged pre-exponential factors for two stages are determined to be 2.80 × 108 and 1.04 × 109 min−1, respectively. Besides, thermodynamic parameters in terms of ΔH, ΔG and ΔS are also evaluated for the whole pyrolysis process. The findings acquired from this study suggest sesame stalk is a promising biomass for sustainable bioenergy generation and kinetic and thermodynamic information is of significance for advancing the design of a sesame stalk pyrolysis reactor.

The exploration of pyrolysis characteristics, kinetics and product distribution of Bermuda grass via TG, Py-PIMS and Shuffled Complex Evolution

The pyrolysis behaviors of biomass play an important role in understanding energy utilization. The pyrolysis characteristics, kinetics and product distribution of Bermuda grass were investigated based on thermogravimetric (TG), pyrolysis with photoionization mass spectrometry (Py-PIMS) and Shuffled Complex Evolution algorithm (SCE). The temperature range for weight loss is 450–850 K and the pyrolysis process can be classified into two regions based on the variation of activation energy, with conversion rates of 0.10–0.40 (Region Ⅰ) and 0.40–0.75 (Region Ⅱ). According to the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahria-Sunose (KAS) methods, the mean activation energy values for Region Ⅰ are 126.70 kJ/mol and 124.20 kJ/mol, respectively. while the values for Region Ⅱ are 161.70 kJ/mol and 159.90 kJ/mol, respectively. Then, a three-component parallel reaction model based on the SCE algorithm was proposed and the pyrolysis kinetic parameters were optimized. The results showed the predicted values using the optimized kinetic parameters are well agreeable with experimental data, which shows that the optimized kinetic parameters and the three-component parallel reaction model may be applicable to the Bermuda grass pyrolysis. Moreover, the Py-PIMS results confirmed that the fast pyrolysis products of Bermuda grass included furan derivatives, ketones, cyclopentanones, phenols, aromatic hydrocarbons, acids and esters.

Characterization, kinetics and thermodynamic evaluation of struvite produced using ferrochrome slag as a magnesium source

There is limited data on studies that have focused on the kinetics, thermodynamics, and characterization of struvite crystallization from alternative magnesium sources. This study focused on thermal analysis of struvite (produced using ferrochrome slag as a magnesium source) and the results indicated that the residual quantities of struvite were lower than the theoretical mass loss of struvite of 51.42%. When using ferrochrome slag (FCS) as the magnesium source, 47.9%, 47.4%, and 46.9% losses in mass were observed for heating rates of 5°C/min; 10°C/min and 15°C/min respectively. The mean activation energies for struvite produced using FCS were deduced using isoconversional kinetic methods and ranged from 49.81to 56.20 kJ/mol which is very similar to the activation energies deduced using MgCl2. The study also focused on the surface morphology, and particle size of the final product at different pH and N:P ratios. The final particle size distribution of the product was significantly influenced by the solution pH. To improve the crystal growth kinetics for both MgCl2 and FCS, a high ratio of N:P molar ratios should be adopted. The product's highest median particle size was obtained using FCS as the magnesium source at a low pH. Median particle size increased with decrease in pH, at a pH of 7.5 the recorded median particle size was 96 µm whilst, the lowest was 31 µm at a pH of 9.5. The highest percent of fines (<10 µm) was recorded at a pH of 9.5 using FCS as magnesium source in the metastable region of struvite precipitation whereas at a pH of 7.5 no fines (<10 µm) were recorded. SEM images confirmed that the struvite underwent morphological changes when prepared with FCS in comparison to that produced using MgCl2. The surface morphology of the finished product demonstrated the presence of irregular shaped particles, due to presence of impurities. The kinetic data showed that struvite precipitation was limited by the chemical reaction step. Model fitting was used to determine the reaction control mechanism and the average activation energies obtained by four model free methods were FWO (56.2), KAS (51.67) Starink (49.61) and Tang (49.81) kJ/mol, indicating that the FWO method was the least accurate method. The thermodynamic data indicated that the thermal degradation of struvite crystals has a high degree of disorder, and the process is endothermic, irreversible, and non-spontaneous.

Insights into optimal gas-ash-energy nexus: Oxy-steam combustion of spent pot lining

Altering the atmosphere type may boost the physicochemical drivers of the combustion, thus contributing to the circularity and sustainable management of hazardous wastes. This study aimed to compare the combustions of spent pot lining (SPL) in the oxy-steam and air atmospheres. The SPL combustion with 21% (Oxy21), 30% (Oxy30), and 40% (Oxy40) O2 in the oxy-steam atmosphere improved the performance indices. Weighted mean activation energy (Em) fell from 148.36 kJ/mol in the air atmosphere to 118.04 kJ/mol in Oxy21, with the lowest Em value occurring in Oxy30 (referred to as energy-saving pathway). With the temperature rise, the pattern of fluorine distributions in the air atmosphere (the oxy-steam atmosphere) exhibited 65.60 → 92.27% (65.87 → 9.08%) of fluorine in bottom ash, 7.33 → 31.84% (22.31 → 72.83%) in off-gas, and 0.4 → 2.56% (11.82 → 22.22%) in fly ash. The increased O2 concentration slightly affected the combustion characteristic indices and fluorine distributions. Steam appeared to enhance the pore expansion. The advance decomposition of Na3AlF6, the new emergence of NaAlO2, and the disappearance of CaF2 characterized the oxy-steam combustion of SPL. The gas-ash-energy nexus was jointly optimized via artificial neural network. The oxy-steam combustion destroyed the stability of both soluble and insoluble fluorine, thus greatly releasing fluorine-bearing gas.

Numerical Solution of nth Order DAEM for Kinetic Study of Lignocellulosic Biomass Pyrolysis

The aim of the present study was to explore the most optimal configuration to numerically solve Distributed Activation Energy Models (DAEMs). DAEMs are useful in obtaining the kinetic parameters in non-isothermal kinetic studies using a thermogravimetry analyzer (TGA). Compared to other kinetic models, DAEMs provide an additional kinetic parameter that quantifies the extent of the reaction (σ) for each reaction’s mean activation energy (E ̅). Although DAEMs are efficacious in kinetic studies, solving DAEMs numerically is challenging. The DAEM equation includes double integration with respect to activation energy and temperature, which involves various numerical discretizations. Previously, many researchers utilized a DAEM to explicate complex reactions such as lignocellulosic biomass pyrolysis. However, most of them have yet to propose a numerical approach to solve DAEMs. Therefore, by exploring multiple numerical calculation configurations, here we present a general structure to numerically solve nth order and first-order DAEMs. The exploration includes determining the optimal integration limit of activation energy and the discretization of activation energy and temperature integration. From the investigation, we came up with a configuration that limits the integration of activation energy from E ̅-3σ to E ̅+3σ. Meanwhile, the number of integration points for temperature and activation energy must be 51 and 21, respectively. By using this configuration, DAEM can be utilized optimally in kinetic studies.

Co-pyrolysis of biomass and polyethylene: Insights into characteristics, kinetic and evolution paths of the reaction process

Investigation on the distribution and mechanism of co-pyrolysis products is vital to the directional control and high-value utilization of agriculture solid wastes. Co-pyrolysis, devolatilization, kinetics characteristics, and evolution paths of corn stalk (CS) and low-density-polyethylene (LDPE) were investigated via thermogravimetric experiments. The co-pyrolysis behaviors could be separated into two stages: firstly, the degradation of CS (150– 400 °C); secondly, the degradation of CS (400– 550 °C). The devolatilization index (DI) increased with the addition of LDPE. Furthermore, a combination of devolatilization chemical analysis with product analysis to analyze the intrinsic mechanism during co-pyrolysis. The results indicated that the yield of alkanes and olefin in gas products increased with the addition of LDPE. Additionally, LDPE pyrolysis maybe abstract hydrogen from CS pyrolysis and evolved into hydrogen, methane, and ethylene. Further, the co-pyrolysis kinetic parameters were computed by using model-free isoconversion methods, which showed promotion of CS pyrolysis and the reduced activation energy. All the activation energy were declined, which indicated a “bidirectional positive effect” during co-pyrolysis. The mean activation energy of P-cellulose (P-CE), P-hemicellulose (P-HM), P-lignin (P-LG), and LDPE decreased by 23.49 %, 12.89 %, 15.36 %, and 27.82 %, respectively. This study further proves the hydrogen donor transfer pathway in the co-pyrolysis process of CS and LDPE, providing theoretical support for the resource utilization of agricultural solid waste.

Mechanistic insights into co-pyrolysis of waste tires and waste lubricating oil: Kinetics and thermal behavior study

ABSTRACT The co-pyrolysis of waste tires (WT) with waste lubricating oil (WLO) can significantly improve the quality of products. The co-pyrolysis behavior of WT and WLO was investigated by using thermogravimetric analyzer. Three isoconversional methods, Flynn–Wall–Ozawa, Friedman and Kissinger–Akahira–Sunose, were used to calculate the activation energy of the mixture at the heating rates of 5, 10, 15, and 20K/min. The obtained data were used to determine the kinetic model and thermodynamic parameters. The results showed that WLO promoted the pyrolysis of WT. The synergistic effect was shown in the reduction of the activation energy of the mixture by 10%. The mean activation energy of the main decomposition stage is 90.8 kJ/mol. Moreover, the thermodynamic stability of reaction was determined by the calculation of change in entropy, Gibbs free energy, and enthalpy. The value of pre-exponential factor is 2.48 × 107/min, which means that the co-pyrolysis reaction is not a complex interface reaction. Among all the models, the 3D diffusion model best fits the co-pyrolysis mechanism judging by Malek master plot method. The reaction function was also determined. This study will provide basic knowledge into the co-processing of WT and WLO for predicting the performance of reactor and simulating the process.

Application of distributed activation energy model to predict hydrothermal carbonization kinetics of lignocellulosic biomass

Hydrothermal carbonization (HTC) has been established as one of the most promising techniques for producing biofuels from high moisture containing organic samples such as, biomass. However, limited progress is observed in terms of the kinetic modeling of this process. Existing kinetic models involve mechanistic and experimental shortcomings due to the nature of the non-isothermal and isothermal subsequent steps involved in the process. To address these limitations, a distributed activation energy model (DAEM) was applied to predict HTC kinetics of lignocellulosic biomass. The DAEM considered the non-isothermal temperature profile of the reactor to account for the considerable devolatilization taking place during the transient step of heating. A micro-kinetic reactor was fabricated to facilitate kinetic experiments to estimate the DAEM parameters- mean activation energy, standard deviation, and pre-exponential factor. These parameters were found to be 96.03 kJ mol−1, 3 kJ mol−1, and 5 × 108s − 1 respectively, based on experiments at final HTC temperatures of 190 °C and 210 °C for lignocellulosic biomass. Furthermore, the parameters were used to accurately predict HTC kinetics at 230 °C using the estimated parameters at 190 °C and 210 °C. The obtained results would be valuable inputs for reactor design and large-scale simulations for HTC of lignocellulosic biomass.

Thermogravimetric kinetic-based computation of raw and pretreated coconut husk powder lignocellulosic composition

Lignocellulosic biomass is one of the potential sources for biofuel production. Coconut husk, one of the abundant lignocellulosic biomass in Indonesia, can be explored for such a process. This work evaluated compositions of raw and pretreated coconut husk powder using modeling and computation of thermogravimetry analysis data. Lignocellulose compositions and distributed activation energy model employing kinetic parameters were successfully obtained with the fit quality values of 0.1–0.35 %, and R-squared values (R2) equal 1. By this method, raw coconut husk powder was found to contain 30 % hemicellulose, 38.86 % cellulose, and 34.96 % lignin. The mean activation energy (E0) was 141–163, 173–181, and 200–230 kJ/mol for hemicellulose, cellulose, and lignin respectively. Meanwhile, the standard deviation activation energy (σ) was 4.8–7.5, 1.76–3.75, and 19–28 kJ/mol for hemicellulose, cellulose, and lignin respectively. The pre-exponential factor (A) values ranged from 1.20 × 1011 to 5.00 × 1013 s−1 where those of hemicellulose, cellulose, and lignin, respectively appeared in ascending order.

Insights into co-pyrolysis of polyethylene terephthalate and polyamide 6 mixture through experiments, kinetic modeling and machine learning

The non-isothermal pyrolysis of polyethylene terephthalate (PET), polyamide 6 (PA6), and their mixtures was studied in a thermogravimetric analyzer at different heating rates. Temperature of maximum decomposition (Tmax) decreased by 25–45 °C and 35–55 °C for the PET:PA6 mixtures (3:1, 1:1, 1:3) compared to PET and PA6, respectively. The kinetic analysis was initially carried out using isoconversional method. However, the dependency of activation energy on conversion was observed for the co-pyrolysis of PET and PA6 that suggested the occurrence of multi-step reactions in the mixtures. Distributed activation energy model (DAEM) was used in this study to describe the multistep reactions occurring during pyrolysis of PET:PA6 mixtures. In this work, a four-parallel reaction DAEM was developed to describe the pyrolysis kinetics of PET:PA6 mixtures. The apparent mean activation energies (Eo) for PET, PA6, and mixtures varied in the range of 244–255, 140–215, and 138–255 kJ mol−1, respectively. The mass loss profiles of PET and PA6 mixtures were also modeled using artificial neural network (ANN). Out of 155 ANN models, the best prediction was made by ANN511 with R2 greater than 0.997 for both test and unseen data. The interaction effects observed through TGA experiments and subsequent kinetic analysis were further assessed in terms of product composition using analytical pyrolysis coupled with gas chromatograph/mass spectrometer (Py-GC/MS). Co-pyrolysis of PET and PA6 resulted in the formation of new aromatic compounds with nitrogen-containing functional groups, which were not detected when PET or PA6 were pyrolyzed individually.

Fast Na+ ion dynamics in the Nb5+ bearing NaSICON Na3+x−zNbzZr2−zSi2+xP1−xO12 as probed by 23Na NMR and conductivity spectroscopy

NaSICON-type (Na superionic conductor, Na1+yZr2SiyP3−yO12, 0 < y < 3) represent a class of fast Na+ ion conductors with bulk ion conductivities in the mS range near room temperature. Starting from Na3Zr2(SiO4)2(PO4), i.e., from y = 2, we investigated the change in ion transport parameter when x in Na3+xZr2Si2+xP1−xO12 is increased from 0 to 0.4 and Nb5+ is substituted for Zr4+ according to Na3+x−zNbzZr2−zSi2+xP1−xO12 (z = 0.04). The later might be beneficial also to change the transport properties in or near the grain boundary regions of our polycrystalline samples. To detect such changes, we used low-temperature conductivity and electric modulus spectroscopy to differentiate between the total and the bulk (intragrain) electrical responses. However, the main purpose of the present study is to corroborate the extraordinarily high bulk ionic conductivity of approximately 7.3 mS cm−1 (x = 0.4 and z = 0.04, room temperature) by diffusion-controlled 23Na NMR spin-lattice relaxation measurements. Indeed, such experiments directly sense the 23Na spin-fluctuations at the nuclear sites as a result of the fast intragrain motional processes. Both methods, nuclear and non-nuclear, point to a mean activation energy of 0.3 eV for Na+ exchange among the multiple sites in the NaSICON framework. In addition, NMR reveals local barriers characterized by activation energies as low as 0.1 eV. Altogether, from a dynamic point of view, Na3.36Nb0.04Zr1.96Si2.4P0.6O12 turned out to be indeed a very promising candidate for the breakneck development of Na-based all-solid-state battery applications.

Kinetics and thermodynamics investigation of pyrolysis of butyl rubber tube waste

Pyrolysis of butyl rubber tube waste was performed under an inert nitrogen gas environment for temperature ranging between 25 and 1,000 °C, by varying the heating rates (5, 10, 20, 35, and 55 °C min&lt;sup&gt;−1&lt;/sup&gt;). Five different iso-conversional approaches, namely, Differential Friedman, Ozawa-Flynn-Wall, Kissinger-Akahira-Sunuse, Distributed activation, and Starink, were employed to investigate the kinetics and thermodynamic parameters. The mean activation energy (&lt;i&gt;E&lt;/i&gt;&lt;i&gt;&lt;sub&gt;α&lt;/sub&gt;&lt;/i&gt;), and pre-exponential factor (&lt;i&gt;k&lt;sub&gt;o&lt;/sub&gt;&lt;/i&gt;) varied between 222.67 and 244.73 kJ mol&lt;sup&gt;-1&lt;/sup&gt; and 6.82×10&lt;sup&gt;21&lt;/sup&gt; and 2.73×10&lt;sup&gt;24&lt;/sup&gt; s&lt;sup&gt;-1 &lt;/sup&gt;respectively, for all iso-conversional approaches. From the kinetic investigation, a strong correlation co-efficient (R&lt;sup&gt;2&lt;/sup&gt;&amp;gt;0.97) was ascertained in the conversion range of up to α=0.8 for all the iso-conversational approaches. By thermodynamic analysis, the mean values of change in enthalpy and change in Gibbs free energy were 217.06-239.13 kJ mol&lt;sup&gt;-1 &lt;/sup&gt;and 185.12-218.11, kJ mol&lt;sup&gt;-1&lt;/sup&gt;, respectively. From the master plot analysis, diffusion model (D3), and several reaction order models (F1, F2, F3, and F5) were predicted throughout the conversion (0.1 to 0.8) limit at 20 °C min&lt;sup&gt;-1&lt;/sup&gt; for the pyrolysis of BRT.