Values Of Pre-exponential Factor Research Articles

Study of conduction mechanisms of InSeSb nano-chalcogenide alloys

The electrical conduction mechanisms for bulk samples of In0.1Se0.9−x Sb x (x = 0, 0.04, 0.08 and 0.12) nano-chalcogenide system, synthesized by the melt-quenching technique are investigated through current–voltage (I–V) characteristics. For the detailed study of conduction mechanism pellets of bulk samples are prepared. A thorough examination of electrical conductivity is done in the temperature range of 295–318 K and 0–50 V voltage range. From I–V measurements it is observed that samples are showing ohmic nature at lower field and non-ohmic nature at relatively higher field values. The temperature dependence of DC conductivity is analyzed using the Arrhenius relationship which is found to increase with Sb content. The value of activation energy and pre-exponential factor are calculated, which revealed that the conduction is due to the hopping of charge carriers among the localized states. Different parameters of Mott’s variable range hopping such as degree of disorder T 0, density of localized states N(E F), hopping distance (R hop), and hopping energy (W) are calculated. For the high field conduction process Poole–Frenkel, and Schottky processes are studied.

Multistep kinetic analysis of additive-enhanced plastic degradation

In the realm of non-isothermal degradation kinetics, the utilization of multi-heating rate data has unveiled a fascinating distributed apparent activation energy (Eα) profile when employing isoconversional methods. The advanced isoconversional method (AIC) emerges as a reliable tool, offering Eα values that evolve as chemical reactions progresses. This phenomenon finds its roots in the complex solid-state degradation of plastics, where long-chain hydrocarbons undergo intricate transformations into smaller components through a web of parallel and sequential reactions under the influence of heat. To comprehensively characterize this multifaceted kinetic process, variable pre-exponential factor (A) values were calculated, considering all available heating rate data, in conjunction with the isoconversional principle. These factors complement the changing Eα values, providing crucial insights into the evolving material transformations throughout the reaction. Remarkably, our investigation revealed that in the initial degradation stage, centered around the breakdown of Brominated Flame Retardant (BFR), the reaction follows a contracting spherical model (R3). Transitioning to the subsequent stage, the polymer material undergoes degradation following the diffusion model D4. The incorporation of the isoconversional principle and Criados' masterplot technique effectively facilitates the precise determination of all three kinetic parameters. The process layout we present holds considerable promise for advancing the understanding and control of complex kinetic phenomena.

Catalytic pyrolysis of pine needles using metal functionalized spent adsorbent derived catalysts: Kinetics, thermodynamics and prediction modelling using artificial neural network (ANN) approach

The current study was indented towards the evaluation of synergism of spent aluminum hydroxide nanoparticle (AHNP) adsorbent derived catalysts in the degradation of pine (Pinus roxburghii) needles through kinetics and thermodynamics analysis. Distinct kinetic (such as activation energy and pre-exponential factors) and thermodynamic (such as entropy, enthalpy, and Gibbs free energy) parameters were estimated through isoconversional (OFA and KAS) models. The study also aimed to envisage the reaction mechanism for all the distinct processes via Criado z master plots. Results illustrated the significant impact of all the different AHNP-derived catalysts in easing up the biomass degradation process. The KAS method evaluated the average activation energy for non-catalytic degradation as 130.01 kJ/mol, while the values changed to 120.95, 121.69, 125.99, 148.47 and 127.37 kJ/mol for Ni/AO, Fe/AO, Cu/AO, Zn/AO and Mo/AO catalyzed degradation, respectively. Amongst all, nickel (Ni/AO) and iron-doped (Fe/AO) catalysts brought the highest reduction in activation energy owing to the provision of strong acidic sites, high specific surface area, and better metal dispersion; subsequently leading to the increased rate of molecular scission and cracking reactions. Values of pre-exponential factor and thermodynamic parameter also displayed the positive impact of catalysts in terms of lowering down the molecular collisions, enthalpy, and disorderness of the system. Furthermore, artificial neural network (ANN) was also employed for the prediction of the biomass degradation where high regression (∼0.99) as well as low mean squared error (<10−5) illustrated the accurate prediction of complex biomass degradation by the ANN technique. Thus, the waste AHNP-derived catalysts have significant potential to be employed for the catalytic pyrolysis of pine needles together with aiding the cost-competitiveness, environmental sustainability, and renewability of the process.

Non-isothermal kinetics of the organocatalytic ring-opening polymerization of ε-caprolactone with metal-free α‑hydroxy acids: Eco-friendly and facile synthesis process

Metal-free and green α‑hydroxy acids (AHA) such as l-malic (MA), DL-mandelic acid (MDL), and citric acid (CA) were successfully and effectively utilized as an effective initiator for the solvent-free ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The performance of AHAs in the polymerization of ε-CL was completely and powerfully investigated via the non-isothermal differential scanning calorimetry (DSC). The proceed of ROP of ε-CL with AHAs could be real-time monitored by the obtained polymerization exotherms at different heating rates. The polymerization exotherms obtained from the ROP of ε-CL with CA occurred at a lower temperature range than MA, and MDA, respectively. From the kinetics study, the average activation energy (Ea) values for the ROP of ε-CL with CA (38.0 ± 1.8 kJ mol−1) were lower than MA (45.2 ± 3.6 kJ mol−1) and MDA (48.8 ± 6.2 kJ mol−1). Using the first-order model fitting, the values of pre-exponential factor (lnA0) for the ROP of ε-CL with CA, MA, and MDA were 7.0 ± 0.3, 8.5 ± 0.2, and 8.9 ± 0.3, respectively. The effectiveness of AHAs in the synthesis of PCL was clarified by conducting a larger-scale (4.0000 g) polymerization using conventional heating and microwave (MW) irradiation methods. From conventional heating, the green AHAs produced PCL with the number average molecular weight (Mn) and dispersity (Đ) values in the range of 5.18 × 103 - 1.43 × 104 g mol−1 and 1.14–2.02, respectively. The irradiation by MW could enhance the synthesis of PCL by reducing the synthesis time. By using the MW power of 450 W and irradiation time of 30 min, the PLC was obtained from the ROP of ε-CL with MA and MDA initiators, and the Mn of the obtained PCL from MW heating was 4.28 × 103 - 8.45 × 103 g mol−1. The mechanism for the ROP of ε-CL with all AHAs was proposed through the activated monomer mechanism.

Metal chlorides and ammonium persulfate hydrothermal carbonization for enhanced pyrolysis behavior and biochar properties

To elucidate the impact of a modified reaction medium on the hydrothermal carbonization (HTC) coupled pyrolysis process, a two-stage conversion of rice straw (RS) was investigated in the present work. RS was initially treated hydrothermally in a conventional medium (water) and a modified reaction medium (metal chlorides and ammonium persulfate AP), followed by an upgrade of the obtained hydrochar via pyrolysis. The characteristics of the modified hydrochar and the pyrolysis biochar were examined. It was shown that a modified reaction medium promoted a higher mass yield of hydrochar. Compared to conventional hydrochar, modified hydrochar exhibited higher ash and fixed carbon content, and lower carbon and oxygen content. Furthermore, the pyrolysis behavior of modified hydrochar was more complex. Not only the DTG curve entirely different was, but the values of activation energy and pre-exponential factor also significantly increased. Ultimately, the modified medium enhanced the adsorption capacity of the HTC coupled pyrolysis biochar. Among them, B-HTC-AP had the highest SBET (544.83 m²/g) and the largest pore volume (0.4644 cm³/g). The TC adsorption capacity of B-HTC-AP reached 187.31 mg/g. The pseudo-second-order kinetic model and the Freundlich isotherm model provided a better description of the TC adsorption process on B-HTC-AP. Possible adsorption mechanisms of B-HTC-AP could encompass pore filling, electron transfer, hydrogen bonding, and π-π interactions. Therefore, the use of a modified reaction medium in the two-stage process could be an effective strategy for upgrading biomass.

Study on non-isothermal pyrolysis of Azadirachta Indica for kinetic triplets and thermodynamics evaluation

Exploring kinetics and thermodynamics of biomass pyrolysis process is imperative for optimizing the process. This study employs various model-free iso‐conversional methods and a model-fitting method to investigate the kinetics and thermodynamics of non-isothermal pyrolysis of Azadirachta indica biomass under four distinct heating rates of 10, 20, 30 and 40 °C/min. Average values of activation energy and pre-exponential factor ranged from 187.613 to 196.635 kJ/mol and 5.068×1014 − 1.178×1022 min−1, respectively, indicating an endothermic and complex nature of reaction. Integral master plots proved superior in revealing the reaction mechanism, although Criado's master plot unveiled a combination of reaction models, aligning with the intricate degradation mechanisms of biopolymers. The average enthalpy change, Gibbs free energy change and entropy change values spanned from 182.425 to 191.638 kJ/mol, from 167.288 to 173.742 kJ/mol and from 0.014 to 0.039 kJ/mol·K, respectively.

Kinetics and thermodynamic parameters of palm empty fruit bunch pyrolysis promoted by calcium-rich wastes from coastal-marine residue

Kinetics and thermodynamics of palm empty fruit bunch (PEFB) pyrolysis have been determined in the presence of catalyst from clam shell (Anadara sp.) (CS) using thermogravimetric analysis. PEFB pyrolysis occurred in three stages (moisture and volatile removal, cellulose and hemicellulose, and lignin decomposition), with maximum degradation occurring at 200–400 °C. Activation energy calculated using the iso-conversional method varied from 89.80 to 169.63 kJ/mol for Friedman, 66.25–119.79 kJ/mol for FWO, 53.33–96.44 kJ/mol for KAS, and 50.90–92.04 kJ/mol for Starink. Pre-exponential factor values ranged from 104–1017 and 104–1014 s−1 for non-catalytic and catalytic pyrolysis. The thermodynamic parameters values varied from 47.28 to 99.44 kJ/mol for enthalpy, from 98.23 to 151.62 kJ/mol for Gibbs free energy, and from −0.0858 to −0.0808 kJ/mol for entropy. The reaction mechanism is dominantly second-order and complex. The analysis revealed that PEFB and CaO catalyst from CS are efficient biomass and effective catalyst for bioenergy production.

Errata and comments on “thermal decomposition of ammonium perchlorate—A TGA–FTIR–MS study: part I” [Thermochim. Acta 610 (2015) 57–68

Some errata were noticed in the calculated pre-exponential factor (A) data represented in the TGA and kinetic analysis section of the paper “Thermal decomposition of ammonium perchlorate—A TGA–FTIR–MS study: part I” [Thermochim. Acta 610 (2015) 57–68]. In the discussion, we analyse what went wrong during the determination of the pre-exponential factor and subsequently identify the correct values. The correct value of pre-exponential factor (A) for the decomposition of 250 to 300 µm size AP particles during the LTD and HTD stages is found to be 5.70 × 109 min−1 and 2.70 × 109 min−1, respectively.

Improving biomass fuel obtained from Brazil nut residues via torrefaction: A case of kinetic and thermodynamic study

The residues of Brazil nuts (Bertholletia excelsa) were evaluated, in their natural state and in torrefied form, for their energy potential after pyrolysis. Samples of shells (BNS) and husks (BNH) were torrefied at 220, 260 and 300 ºC for 30 and 60 min, and were characterized for their chemical and energetic composition. It was also determined which samples showed, simultaneously, the lowest hemicellulose content and the highest cellulose content after torrefaction via analysis of the decomposition profile at 10 ºC/min under pyrolysis. The evolution of gases such as H2O, CO2 and/or C3H8, and CH4 was observed by simulated pyrolysis on a microscale in a thermogravimetric analyzer coupled to a mass spectrometer (TGA-MS). In addition, the kinetics of the pyrolysis of untorrefied and torrefied samples were evaluated using the Flynn-Wall-Ozawa (FWO) and Vyazovkin (VYZ) models in order to obtain the activation energy, pre-exponential factor and thermodynamic parameters. The predominant reaction mechanism was determined by Criado Master-plot method. The mean value of the activation energies ranged from 132.24 to 134.95 kJ/mol for BNS, from 135.53 to 138.47 kJ/mol for ST263, from 149.10 to 150.96 kJ/mol for BNH and from 145.83 to 148.14 kJ/mol for HT263. It was found that D2 and D4 diffusion mechanisms are prevalent in the decomposition of untorrefied samples, while torrefied samples were better adjusted to the F1/A2/A3/A4 overlapping nucleation models. High pre-exponential factor values indicated the presence of multiple intermolecular collisional reactions. The thermodynamic parameters evaluated, as well as the variations in enthalpy, Gibbs free energy and entropy, indicated that the evaluated process is endothermic, though requires little energy. As a whole, in view of the optimized parameters and elevation of the thermal stability of the material, the results demonstrate good potential for the use of Brazil nut shells and husks torrefied at 260 ºC for 30 min as biochar. In addition, pyrolyzed Brazil nut residues also have great potential in the production of bio-oil and biogas, in view of the high content of volatile matter released during the decomposition of the hemicellulose and lignin.

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.

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.

Kinetics and mechanism of oxidizing roasting of sulfide copper-cobalt ore

The aim of the study was to examine the chemistry, kinetics and mechanism of oxidizing roasting of a typical sample of sulfide copper-cobalt ore. The research object was sulfide copper-cobalt ore with the following main minerals: pyrite, pyrrhotite, chalcopyrite, sphalerite, tremolite, silicon dioxide, talc, siderite and calcite. The methodology involved high-temperature X-ray phase analysis (100–900°C), thermogravimetry, differential scanning calorimetry and mass spectrometry of the released gas (30–1100°C, heating rate – 5–20°C·min-1, air flow rate – 30 cm3·min-1). The chemistry, kinetics and mechanism of oxidizing roasting of sulfide copper-cobalt ore with a particle size of &lt;0.1 mm were studied. It was found that the process can be represented as a set of seven elementary reactions: five exothermic reactions (at 398–445, 394–488, 440–498, 433–549 and 451–562°C), corresponding to the intense combustion of iron, copper and zinc sulfides, and two endothermic reactions (at 651–664 and 743–927°C), associated with the decomposition of residual copper and iron sulfates. Kinetic analysis (Kissinger and Augis-Bennett methods, identification of the reaction model by reference function and iterative optimization) of differential scanning calorimetry data in connection with the above reactions showed that the limiting stage of the latter is nucleation and crystal growth. The values of activation energy, pre-exponential factor and Avrami parameter ranged between 140–459 kJ·mol-1, 1.41·104–3.49·1031 with-1 and 1.0–1.7, respectively. It was established that crystallization of the products of elementary reactions is accompanied by an increase in the number of nuclei; new phase nuclei can be formed both on the surface and in the bulk of ore particles. The crystal growth is one-dimensional and is controlled by a chemical reaction at the interphase boundary or by diffusion of reagents. The results obtained can be applied in the practice of oxidizing roasting of sulfide ores and concentrates.

Assessing the potential of the invasive grass Cenchrus echinatus for bioenergy production: A study of its physicochemical properties, pyrolysis kinetics and thermodynamics

The current study aims to investigate the physicochemical properties and pyrolysis characteristics (kinetic triplet and thermodynamic parameters) of the invasive grass Cenchrus echinatus to assess its bioenergy potential. A thermogravimetric analyzer was employed to obtain the pyrolysis behavior of the grass under slow non-isothermal conditions. First, a multi-component deconvolution analysis of differential thermogravimetry (DTG) curves using the Fraser–Suzuki function was performed, aiming to quantify the individual devolatilization reactions of hemicellulose (P–HC), cellulose (P–CL), and lignin (P–LG). The survey of the activation energy employing four isoconversional methods (Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Starink) indicated the following devolatilization order: P–LG (329.9 − 376.7 kJ mol−1) > P–CL (178.4 − 188.2 kJ mol−1) > P–HC (157.8 − 161.2 kJ mol−1). With values of pre-exponential factors from 1.1 × 1015 to 1.4 × 1031 min−1, as estimated from the kinetic compensation effect, it was deduced that the chemical reactions with simpler nature are predominant. With the method of integral master plot, a geometrical contraction mechanism matched the devolatilization of P–CL, and an nth-order-based reaction model matched the devolatilizations of P–HC and P–LG. Besides, the thermodynamic study suggested that the conversion process is endothermic (ΔH≠ = 153.4 to 245.2 kJ mol−1) and nonspontaneous (ΔG≠ = 146.8 to 174.4 kJ mol−1). With the three kinetic triplets, one overall rate expression for the pyrolysis of invasive grass C. echinatus was established. The simulation results were then compared to experimental kinetic curves, and the agreement was deemed satisfactory. The outcomes from this research recommend the C. echinatus as a promising feedstock for bioenergy production and are decisive for scheming large-scale pyrolysis reactors for this invasive grass.

Kinetics of solid-state oxidation of iron, copper and zinc sulfide mixture

The kinetics of solid-state oxidation by air of iron, copper and zinc sulfide natural mixture, which is typical of the pyritic copper ores, is investigated. Using the high-temperature X-ray powder diffraction, thermogravimetry and differential scanning calorimetry, it was found that the process can be represented by five exothermic elementary reactions, corresponding to intensive burning of iron, copper and zinc sulfides, and two endothermic ones, associated with decomposition of copper and iron sulfates. Kinetic analysis is performed by Kissinger and Augis–Bennett methods, the model-free function mechanism was determined from y(α) master plots and iterative optimization of the kinetic parameters. The limiting steps of these reactions are nucleation and crystal growth, and the values of activation energy, pre-exponential factor and Avrami exponent are in the ranges of 140–459 kJ·mol–1, 1.41·104–3.49·1031 s–1, and 1.0–1.7, respectively. Crystallization is followed by an increase in the number of nuclei, which may be formed both at the interface and in the bulk of the ore particles, and crystal growth is one-dimensional and controlled by a chemical reaction at the phase boundary or diffusion. The results of the work can contribute to the development of theoretical ideas about the physicochemical transformations of pyritic ores and concentrates during pyrometallurgical operations.

Thermal degradation of KN90 gauze mask rope waste: Thermogravimetric and thermodynamic analyses, kinetic modeling and volatile products

Pyrolysis is a promising thermal conversion method to dispose medical wastes. The pyrolysis behaviors, kinetics, thermodynamics and volatile products of KN90 gauze mask rope waste in nitrogen are studied under current study. The results indicate that two stages (stage 1: 0 ≤ α < 0.65 and stage 2: 0.65 ≤ α ≤ 1) mainly constitute the pyrolysis process of KN90 gauze mask rope waste in nitrogen. The average values of activation energy for stage 1, stage 2 and the entire pyrolysis process are 254.79 kJ/mol, 340.96 kJ/mol and 285.21 kJ/mol, respectively. The thermal degradation in stage 2 can be regarded as one-step reaction. The average value of pre-exponential factor for stage 2 is 1.17 × 1024 min−1 g(α)=(1-α)−2-1 can be adopted to characterize the thermal degradation in stage 2. The kinetic parameters for stage 2 can be adopted to well predict the conversion rate of stage 2. The variations of thermodynamic parameters suggest that the pyrolysis of KN90 gauze mask rope waste in nitrogen occurs more easily with the progress of thermal degradation. The total yield for the volatile products from most to least is alkanes > carbon dioxide > aromatic compounds > olefins > compounds containing carbonyl groups > alkynes > alcohols and water vapor. The possible chemical reactions to generate the specific volatile products are proposed.

Exploring the potential of fish waste (Sardinella fimbriata) through pyrolysis: A study of kinetics and thermodynamics using isoconversional methods

The growing global demand for fish has led to an increase in fish waste (FW) production, necessitating efficient waste management strategies. Pyrolysis is a promising way to convert fish waste into high-value products. To achieve optimal waste mass reduction and gain insights into the pyrolysis process, estimating kinetic parameters is essential. This study investigated the pyrolysis of FW, Sardinella fimbriata, a previously unexplored waste source, using a thermogravimetric analyser. The study determined an average activation energy value of 84–124 kJ/mol using model-free isoconversional methods including Flynn-Wall–Ozawa, Kissinger–Akahira–Sunose, and Starink, whereas pre-exponential factor values were predicted to be between 102 and 1011 s−1. Further analysis using Criado's reduced master-plot approach showed that the experimental curves for pyrolysis coincided with many different theoretical plots for reaction mechanisms, with a concentration on reaction-order models. The analysis of thermodynamic parameters showed positive values of enthalpy change and Gibbs energy change for S. fimbriata FW pyrolysis, suggesting that the process is endothermic and non-spontaneous, while negative values of entropy change were observed across all conversion degrees as a result of the breakdown of complex organic molecules into simpler compounds. This study provides insights into the feasibility of thermal processes and offers new guidance for FW waste management and resource recovery, expanding the understanding of pyrolysis kinetics and thermodynamics for fish waste treatment.

Facile synthesis, structural, optical and optoelectrical characterizations of promising novel InSbS3 thin films for photovoltaic applications

This work aims to prepare InSbS3 thin films using the spray pyrolysis procedure at various thicknesses t = 192, 265, 341, and 448 nm. The formation of the InSbS3 films was confirmed by the X-ray diffraction measurements that displayed orthorhombic structure of the InSbS3 films. On the other hand, Williamson-Hall (W–H) relation were used to assess the structural parameters for the spray deposited InSbS3 films. This method depicts the enhancement in the average grain size of the InSbS3 layers caused by growing the film thickness. On the other hand, the Tauc's relationship was applied to derive the direct energy gap of the as deposited and annealed InSbS3 films which reduced from 1.79 to 1.46 eV by raising the film thickness. Further, the optical dielectric constants of the novel InSbS3 films were boosted as the film thickness. Moreover, by extending the film thickness, we note an enhancement in the non-linear optical parameters χ(1) , χ(3) and n2 of the InSbS3 films. Moreover, the electrical conductivity of spray deposited InSbS3 films has been improved by increasing the film thickness. The hot probe procedure indicated that the spray deposited InSbS3 films are p-type semiconductors. The electrical results show that as the film thickness increases, the activation energy of the InSbS3 films decreases and the pre-exponential factor values are enlarged.

Pyro–catalytic co–pyrolysis of Delonix regia and butyl rubber tube: Kinetic modelling and thermodynamic insights

The target of the proposed work was to compute the kinetic modelling (KM) and thermodynamic insights (TI) for the pyro-catalytic co-pyrolysis (PCCP) of Delonix regia (DR) and Butyl rubber tube (BRT). For PCCP of DR and BRT (1:1 co-feed), three different types of catalysts were utilized: zeolite (Na–Y), noble metal on activated carbon (10 wt % Pt/C), and metal oxide (1:1 wt % TiO2–ZnO) catalysts of loading between 30 and 10 wt %. For computing KM and TI, several iso-conversional models such as Friedman (FM), Flynn–Wall– Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink (STK), and Distributed Activation Energy Method (DAEM) were applied. At DR:BRT:Na-Y (1:1:10 wt %), the FWO model ascertained the lowest average values of activation energy Eα (kJ/mol) and pre-exponential factor A (s−1) as 180 and 5.95E+16, respectively whereas ΔH (kJ/mol) and ΔG (kJ/mol) as 175 and 180 for TI correspondingly.

Development of a Hybridized Model for Determining the Degree of Polymerization of Power Transformers

Power transformers have been described as an important equipment of electrical switchyard in which its failure results in long hours of outage. Some of the existing models for determining the Degree of Polymerization (DP) of power transformers were based on singular parameter which is not sufficient for the assessment of power transformers’ lifespan. This research paper therefore developed a hybridized model for determining the degree of polymerization of power transformers. The study employed the use 2-Furaldehyde (2FAL) content values of 0.5 ppm to 10ppm in determining the DP value and simulation was carried out using MATLAB. The result was compared with existing DP model for effectiveness of the Hybridized DP model. The developed model yielded a DP range of 247 ≤ DP ≤ 1184 based on a constant hotspot temperature of 110 0 C and the values of activation energy and pre-exponential factors used. The results from this research presented a better method of determining the Degree of Polymerization of power transformer compared to the existing method. Therefore, the Hybridized DP model developed is more sufficient for the evaluation of lifespan of power transformers. Keywords: Power Transformers, Electrical Switchyard, Lifespan, Degree of Polymerization, Statistical Tools, Power Failure, Outages. DOI: 10.7176/ISDE/12-6-04 Publication date: October 31 st 2022

BaCoO3−δ perovskite-type oxygen carrier for chemical looping air separation, part Ⅰ: Determination of oxygen non-stoichiometry and cyclic stability of oxygen carrier

Chemical looping air separation (CLAS) is a cost-effective high-temperature air separation technology, and finding suitable oxygen carriers with high oxygen selectivity and capacity is of vital importance to it. Perovskite-type oxides have been extensively studied as oxygen carriers due to their high oxygen selectivity. In this work, BaCoO3-δ perovskite oxide with large oxygen capacity was proposed as an excellent oxygen carrier for CLAS. BaCoO3-δ perovskite powder was synthesized through a sol–gel method, and the determination of oxygen non-stoichiometry and cyclic stability of BaCoO3-δ was investigated via thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Results indicated that the oxygen non-stoichiometry of BaCoO3-δ was a function of temperature and oxygen partial pressure, and the empirical formula was determined by linear fitting in the range of δ less than 0.5. The standard enthalpy change and standard entropy change of the oxygen desorption reaction were 169.43 kJ/mol and 156.19 kJ/(mol·K) at δ of 0.38, which increased to 292.58 kJ/mol and 298.81 kJ/(mol·K) at δ of 0.47, respectively. The oxygen desorption amount and desorption rate of BaCoO3-δ remained extremely stable during 50 cycles at 875℃, with an oxygen capacity of approximately 0.018 g O2/g BaCoO3 of each cycle. The kinetics of the oxygen desorption process of BaCoO3-δ perovskite was described using the 3-D diffusion Jander model, and the obtained values of apparent activation energy (Ea) and pre-exponential factor (A) were 209.79 kJ/mol and 1.93E06, respectively. Further results indicated that BaCoO3-δ demonstrated a hexagonal perovskite phase, the desorbed oxygen was provided by lattice oxygen in perovskite, the crystal structure remained stable during cycles, and the micro-morphology slightly changed after 50 cycles.