Values Of Pre-exponential Factor Research Articles

Influence of particle size and density of pelleted samples of forest fuel on thermokinetic characteristics of pyrolysis and oxidation

This paper presents the results of experimental studies of thermokinetic characteristics of pyrolysis and oxidation of pine needles, taking into account the influence of particle size and density of forest fuel in pelleted samples. The sample densities range within 206-955 kg/m3 (i.e. from typical sample densities to average ones for pressed pelleted samples), and the component particle sizes amount to 60-140 ?m. The range of studied temperatures is 20-1000??. The particle size and density of the material are found to be important parameters that significantly affect the kinetics of pyrolysis. According to the results of measurements, the activation energy of needles pyrolysis is within the range of 22.8-113.8 kJ/mol, and that of oxidation corresponds to 134.7-211 kJ/mol. Three intervals with significantly different values of activation energy and pre-exponential factor are distinguished in the studied temperature range. Approximation expressions are formulated for the activation energies of pyrolysis and oxidation as functions of forest fuel particle sizes, sample density and temperature.

LiCl-promoted-dehydration of fructose-based carbohydrates into 5-hydroxymethylfurfural in isopropanol.

The carbohydrate-derived 5-hydroxymethylfurfural (HMF) is one of the most versatile intermediate chemicals, and is promising to bridge the growing gap between the supply and demand of energy and chemicals. Developing a low-cost catalytic system will be helpful to the production of HMF in industry. Herein, the commercially available lithium chloride (LiCl) and isopropanol (i-PrOH) are used to construct a cost-effective and low-toxic system, viz., LiCl/i-PrOH, for the preparation of HMF from fructose-based carbohydrates, achieving ∼80% of HMF yield under the optimum conditions. The excellent promotion effect of LiCl on fructose conversion in i-PrOH could be attributed to the synergistic effect of LiCl with i-PrOH through the LiCl-promoted and i-PrOH-aided dehydration process, and the co-operation of LiCl and i-PrOH for stabilizing the as-formed HMF by hydrogen/coordination bonds, giving a low activation energy of 68.68 kJ mol−1 with a pre-exponential factor value of 1.2 × 104 min−1. The LiCl/i-PrOH system is a substrate-tolerant and scalable catalytic system, fructose (scaled up 10 times), sucrose, and inulin also give 73.6%, 30.3%, and 70.3% HMF yield, respectively. Moreover, this system could be reused 8 times without significant loss of activity. The readily available and low-toxic LiCl, the sustainable solvent (i-PrOH), the renewable starting materials, and the mild reaction conditions make this system promising and sustainable for the industrial production of HMF in future.

Thermal degradation characteristics, kinetics, thermodynamic, and reaction mechanism analysis of pistachio shell pyrolysis for its bioenergy potential

The research work aims to estimate the bioenergy potential of pistachio shell and study its degradation kinetics which is necessary for the efficient design and optimization of thermochemical processes for bioenergy generation. Initial characterizations (proximate, ultimate, higher heating value, and compositional analysis), kinetic study, and thermodynamic analysis accompanied by reaction mechanism are investigated. Physicochemical characterization results confirmed high volatile matter (~ 79.8 wt%) and high heating value (16.85 MJ/kg) of pistachio shell. Thermogravimetric analysis (TGA) is performed at four different heating rates of 10, 20, 30, and 40 °C/min under nitrogen gas flow rate from ambient temperature to 900 °C. TGA results show the three-stage pyrolysis reaction which involves removal of moisture and light volatiles, degradation of cellulose and hemicellulose, and decomposition of lignin. The result also reveals that maximum degradation occurred in the temperature range of 200–400 °C. For calculating the kinetic (activation energy and pre-exponential factor) and thermodynamic parameters (enthalpy, entropy, and Gibbs free energy), different iso-conversional models, i.e. Flynn-wall-Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Friedman, are employed which gives the average value of activation energy as 168.86, 165.80, 166.29, and 190.10 kJ/mol, respectively and the pre-exponential factor values lie in the range of 107-1021 s−1. The average values of Gibbs free energy calculated for FWO, KAS, Starink, and Friedman methods are 182.09, 182.15, 182.13, and 181.42 kJ/mol, respectively. Criado method and Z plot are showing complex reaction mechanism. The results of kinetics and thermodynamic study reveal pistachio shell is an efficient biomass for bioenergy production.

Empirical correction of kinetic model for polymer thermal reaction process based on first order reaction kinetics

• A thermal reaction kinetic model in integral form is derived. • Correction methods are provided to compensate the variation of reaction rate. • The value of pre-exponential factor not need to be determined. • The model shows good fitting and has a very wide adaptability. Based on the theory of first-order reaction kinetics, a thermal reaction kinetic model in integral form has been derive. To make the model more applicable, the effects of time and the conversion degree on the reaction rate parameters were considered. Two types of undetermined functions were used to compensate for the intrinsic variation of the reaction rate, and two types of correction methods are provided. The model was explained and verified using published experimental data of different polymer thermal reaction systems, and its effectiveness and wide adaptability were confirmed. For the given kinetic model, only one parameter needs to be determined. The proposed empirical model is expected to be used in the numerical simulation of polymer thermal reaction process.

Modeling of Metalized Food Packaging Plastics Pyrolysis Kinetics Using an Independent Parallel Reactions Kinetic Model.

Recently, a pyrolysis process has been adapted as an emerging technology to convert metalized food packaging plastics waste (MFPWs) into energy products with a high economic benefit. In order to upscale this technology, the knowledge of the pyrolysis kinetic of MFPWs is needed and studying these parameters using free methods is not sufficient to describe the last stages of pyrolysis. For a better understanding of MFPWs pyrolysis kinetics, independent parallel reactions (IPR) kinetic model and its modification model (MIPR) were used in the present research to describe the kinetic parameters of MFPWs pyrolysis at different heating rates (5–30 °C min−1). The IPR and MIPR models were built according to thermogravimetric (TG)-Fourier-transform infrared spectroscopy (FTIR)-gas chromatography−mass spectrometry (GC-MS) results of three different types of MFPWs (coffee, chips, and chocolate) and their mixture. The accuracy of the developed kinetic models was evaluated by comparing the conformity of the DTG experimental results to the data calculated using IPR and MIPR models. The results showed that the dependence of the pre-exponential factor on the heating rate (as in the case of MIPR model) led to better conformity results with high predictability of kinetic parameters with an average deviation of 2.35% (with an improvement of 73%, when compared to the IPR model). Additionally, the values of activation energy and pre-exponential factor were calculated using the MIPR model and estimated at 294 kJ mol−1 and 5.77 × 1017 kJ mol−1 (for the mixed MFPW sample), respectively. Finally, GC-MS results illustrated that pentane (13.8%) and 2,4-dimethyl-1-heptene isopropylcyclobutane (44.31%) represent the main compounds in the released volatile products at the maximum decomposition temperature.

Effect of ash removal on structure and pyrolysis/gasification reactivity of a Chinese bituminous coal

In this study, the effect of ash removal on Shenfu bituminous coal was investigated. The coal was pretreated by hydrofluoric acid (HF) pickling, and the raw/pretreated coal chars were prepared at 900 °C in a fixed bed reactor. The structure of coal and char were detected by Fourier transform infrared (FTIR) and Raman spectroscopy. The reactivity was tested in a thermogravimetric analyzer, including coal pyrolysis and char gasification. The reaction kinetics was analyzed through the Coats–Redfern method, master plots, the model-free and model-fitting method. The results show that the HF pickling can remove silicon from coal efficiently, and the macromolecular framework of coal is quite stable according to FTIR. The Raman parameters imply some carbonaceous structure on coal surface changed. For slow pyrolysis of coal, the effect of heating rate is considered. The changes of pyrolysis characteristics and kinetics are insignificant. For char gasification, the reactivity under isothermal and non-isothermal condition are discussed with an emphasis in different residence time of devolatilization process. In kinetic control region (low temperature), the activation energy (Ea) is very close (about 240 kJ/mol) for all chars. With the temperature increases, the reactivity of raw coal char is more easily suffered by diffusion. The random pore model is more suitable for the ash-free coal char, and the char with long residence time has a larger value of structural parameter ψ and smaller value of pre-exponential factor A. The Ea calculated by model-fitting and model-free method were in good agreement.

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

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

Изучение кинетических особенностей синтеза анилина на Ni-содержащем сверхсшитом полистироле

This paper presents a study of the kinetics of catalytic hydrogenation of nitrobenzene to aniline in the presence of Ni-containing catalysts based on super-crosslinked polystyrene. Aniline hydrogenation is a complex multi-stage process accompanied by the formation of a large number of both intermediate and by-products, including azobenzene, azoxybenzene, nitrosobenzene, phenylhydroxylamine and other substances. Therefor the study of the process kinetics is an important scientific and technical task necessary to increase the yield of the target product — aniline. The hydrogenation reaction of nitrobenzene was carried out in a six-cell high-pressure reactor Parr instruments, Series 5000. The products were analyzed by chromatography using a gas chromatograph Kristallux-4000M (Russia, Meta–Chrom). The effect of temperature, pressure, and concentration of the catalyst was studied; optimal reaction conditions were selected that ensure the maximum yield of aniline. Investigation of the effect of the nitrobenzene initial concentration on the rate of its transformation shows that increase of catalyst to nitrobenzene ratio from 0.2 to 0.6 kg (Cat)/kg (NB) leads to a linear increase in the rate of transformation of nitrobenzene from 0.0002 kg (NB) / (kg (Cat)*s ) to 0.0028 kg(NB)/(kg(Cat)*s), a further increase in the ratio of catalyst concentration to nitrobenzene concentration to 1.2 kg (Cat)/kg(NB) leads to stabilization of the nitrobenzene transformation rate at the level of 0.003 kg(NB)/(kg(Cat)*s). An increase in the temperature of the reaction from 90 to 160 °C contributes to a significant increase in the nitrobenzene transformation rate. The constructed dependences made it possible to calculate the apparent activation energy of the process, which amounted to be 50.4 kJ/mol and the preexponential factor, which amounted to be 15821.1 1/s. The applicability of the Langmuir–Henschelwood model to describe the basic kinetic laws of the reaction of catalytic nitrobenzene hydrogenation with the formation of aniline is studied. Numerical methods in the Matlab software allows to determine the values of preexponential factors and activation energies of the nitrobenzene hydrogenation processes, adsorption of nitrobenzene and adsorption of hydrogen, which made it possible to establish the optimal area of nitrobenzene hydrogenation process of hydrogenation of Pн2 = 15–18 atm, C(NB) = 1.2 kg(NB)/kg(Cat), t =115–120 °C providing maximum speed.

Kinetics and physical analyses for pyrolyzed Egyptian agricultural and woody biomasses: effect of microwave drying

This paper investigates microwave drying effect as a pretreatment method on the kinetic parameters of four torrefied biomasses. The considered biomasses are rice straw, rice husk, sugarcane, and cotton stalks. Dried samples (microwave or oven-dried) were then torrefied under isothermal conditions in a thermogravimetric analyzer (TGA) at two different temperatures of (250 and 300 °C). Two simple kinetics methods were applied including direct Arrhenius (DA) and Coats and Redfern (CR). The physical structure of rice straw and cotton stalks as a function of drying method and torrefaction temperature has been studied using Brunauer–Emmett–Teller (BET) surface area technique. Results revealed that microwave drying increased both the activation energy and the pre-exponential factor for both rice straw and sugarcane regardless of the torrefaction temperature, while the opposite occurred for rice husk. In the case of cotton stalks, microwave drying increased the kinetic parameters at 250 °C and decreased them at 300 °C. The activation energy and pre-exponential factor values obtained from CR method were larger than the ones from DA method. The 300 °C torrefied, conventionally dried rice straw has the lowest activation energy and pre-exponential factor and the largest peak width indicating wide range of reactivity. While microwave dried sugarcane, torrefied at 250 °C, is the hardest one to react. All microwave dried samples require more heat to decompose regardless of the torrefaction temperature. Microwave drying increased the surface area, mean pore diameter, and pore volume for rice straw, while the opposite occurred for cotton stalks due to its woody nature.

Compatibility and thermal decomposition behavior of an epoxy resin with some energetic compounds

ABSTRACT For developing a new explosive formulation, a compatibility of polymeric binder with energetic compound is of most important in the pre-formulation stage. In this article, differential scanning calorimetry (DSC) method, according to STANAG 4147, was used to examine compatibility of diglycidyl ether of bisphenol A (DGEBA) with selected explosive compounds especially 1,3,5-trinitro-1,3,5-triazinane (RDX), l,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6,8,10,12 hexanitrohexaazaisowurtzitane (CL-20). Furthermore, the thermal decomposition behavior of the binary mixture was also studied by thermogravimetry. Results show that the epoxy resin (ER) possessed a good compatibility with both HMX and CL-20, while it showed a bad compatibility with RDX, according to STATNG 4147. The kinetics for the thermal decomposition reaction was also investigated through the Kissinger method using peak temperature obtained from DSC curves at different heating rates. The apparent activation energy for the RDX/ER, HMX/ER and CL-20/ER samples was obtained around 273.9, 299.3 and 166.3 kJ mol−1 with pre-exponential factor (A) value of 1.8 × 1029, 1.9 × 1028 and 9.3 × 1016 s−1, respectively.

CO2 mineralization by burnt oil shale and cement bypass dust: effect of operating temperature and pre-treatment

The alkaline wastes such as burnt oil shale (BOS) and cement bypass dust (BPD) generally contain free lime and portlandite which make them suitable sorbent materials for CO2 trapping via mineral carbonation technique of carbon capture and sequestration. In order to study the reaction kinetics and effect of operating parameters on carbonation processes of such alkaline wastes for future industrial sized scale-ups, as well as to identify the effects on carbonation capacity when these sorbents undergo pre-treatment and are exposed to different temperatures, BOS and BPD as sorbents in CO2 mineralization process have been investigated with thermal analysis methods in the current work. Results indicate that selected types of BOS and BPD could be used as binders in the CO2 mineralization systems, binding reasonably good amount of CO2 already in the early stage of the carbonation process which later slows down as the rate of CaO carbonation becomes mainly diffusion controlled. Increased process temperature and hydration as pre-treatment improve the CO2 binding ability, while the effect of milling has been found to be staggering and not as significant as the effect of hydration and temperature rise. The appropriate kinetic mechanism functions were determined, and the kinetic parameters—activation energy (Ea) and pre-exponential factor (A) values were calculated for all the samples. The Ea values of hydrated samples are lower for BOS samples compared to non-hydrated samples. It was shown that activation by hydration enables to reach the same CO2 uptake levels at lower temperatures, thereby making the mineralization process more energy efficient and thus lowering the costs.

Kinetic Modeling of Citrullus Lanatus (Watermelon) Peel Using Thermo Gravimetric Analysis

AbstractThis work aims at the kinetic studies of the hydrochar produced from hydrothermal carbonization of citrulluslanatus(watermelon) peel. The hydrochar was prepared at optimized conditions regarding Carbon content, High Heating Value and Yield at experimental conditions of 210 °C and 1 h operation. The Watermelon peel hydrocharkineticswereinvestigated at heating rates of 5 °C${\text{mi}}{{\text{n}}^{ - 1}}$, 10 °C${\text{mi}}{{\text{n}}^{ - 1}}$, 15 °C${\text{mi}}{{\text{n}}^{ - 1}}$, & 20 °C${\text{mi}}{{\text{n}}^{ - 1}}$, through thermogravimetric analysis. Two iso-conversional models were applied to compute the kinetic parameters and pyrolysis behavior of hydrochar. The kinetic study using Kissinger-Akahira-Sunose (KAS) model revealed that for a conversion range of 0.1 to 0.8,the activation energy was observed to be in the range of 146 to 220 kJ/mol. Similarly, the activation energies estimated through Flynn-Wall-Ozawa (FWO) model also gave a similar range of kinetic energies from 147 to 219 kJ/mol. Moreover, higher pre-exponential factor values explained the convoluted structure of biomass. The regression coefficient (${R^{2\,}}$) for both the models is high and they have shown similar activation energies which confirms that the best reaction mechanism is predicted. This research helps in establishing an economical and efficient technology for producing clean bioenergy and useful chemicals.

Cone Calorimeter and Thermogravimetric Analysis of Glass Phenolic Composites Used in Aircraft Applications

The increasing use of composite materials in aircraft cabins and structures poses significant challenges in order to maintain and improve the fire safety of aviation. In this work, the flammability characteristics of a commercial glass-fibre reinforced phenolic composite (GFRP) used for aircraft cabin partitions and furnishing are investigated experimentally. Thermogravimetric analysis under inert atmosphere at several heating rates provided information on the thermal decomposition process. The degradation process is modelled with one and two-step mechanisms using the Ozawa–Flynn–Wall iso-conversional method and the GPYRO numerical code which utilizes a genetic algorithm optimization scheme. The estimated activation energy and pre-exponential factor values, especially in the two-step case (77.18 and 104.69 kJ/mol and 2.60 × 106 and 3.19 × 106 min−1 for the first and the second step respectively), recover reasonably well the conversion degree and its derivative. Tests with a cone calorimeter (CC), performed at different incident heat fluxes, provided information on the reaction to fire characteristics of the material and the influence of the heat flux on the combustion process. In general, combustion proceeds in two stages, flaming and smoldering combustion. The CC results assisted by scanning electron microscopy photos provide information on the charring characteristics of the material. The critical heat flux for ignition and the corresponding ignition temperature are estimated, correlating heat fluxes with time to ignition. Thermally thin and thick models are considered, as well as a modified technique bridging the gap between these limit cases and therefore valid for thermally thin and thick but also intermediate conditions (more pertinent in the present case). The results for this latter approach are $$\dot{q}^{\prime\prime}_{ig,cr}$$ ~ 20 kW/m2 and Tig = 469°C, providing also complementing information on thermophysical properties, such as thermal diffusivity, α = 1.23 × 10−7 m2/s, thermal conductivity, k = 0.325 W/(m K) and specific heat capacity, c = 1.330 kJ/(kg K). This work provides information on the reaction to fire characteristics of GFRP, but also on physical and flammability properties in a form suitable to be used in numerical codes, for the prediction of fire and evacuation scenarios. The influence of the reinforcement structure on the fire behaviour of the composite is also illustrated and discussed.

Thermal Degradation and Kinetic Study of Cassava Rhizome for Torrefaction Application

Thermal decomposition kinetics of cassava rhizome (CR) is an important key in the torrefaction process. Kinetic analysis of the cassava rhizome torrefaction was investigated using a thermogravimetric analyser in which CR weight loss is measured under nitrogen atmosphere from ambient temperature to 973K at 5, 10, 20, and 30 K·min−1. Two model-free iso-conversional methods, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) have been used to determine activation energies as a function of the extent of degradation. In this work, the CR particles were separated into 3 study groups, 0.125-0.425 mm, 0.425-0.850, and 0.850-2 mm. The average activation energies calculated by using the methods are relatively similar for all three-particle size samples. The average activation energy values calculated by FWO method were 170.509, 172.593, and 130.149 kJ·mol−1, respectively. These data were comparable to KAS method in which the average activation energy numbers were 170.647, 177.276, and 128.620 kJ·mol−1. Both methods indicated that the activation energy was relatively constant until the conversion of 0.5. The pre-exponential factor values from FWO and KAS ranged 4.87E+17 s−1 and 7.28E+14 s−1, respectively. The experimental results show that kinetic parameters from both methods are suitable and effective to help describe the thermal degradation of the cassava rhizome.

An improved model for the kinetics of non-oxidative hydrothermal process

Hydrothermal processing as a post-treatment technology for sludge has attracted great interest globally as it could reduce the amount of sludge considerably. This experimental study developed a comprehensive kinetic model of cellulose degradation via non-oxidative hydrothermal processing at various temperatures (ranges 180–260 °C). Values of activation energies and pre-exponential factors were determined using chemical oxygen demand (COD)-based lumped concentrations. In this study, a new reaction pathway between solid, soluble matter and gaseous products was proposed which not only enables prediction of solid phase degradation but also can predict the formation of various types of products (in liquid and gas phase) during the reaction time. The results show that the reaction rate of cellulose to liquid products (k1=2.7×109exp(−102810RT)) were fast compared to that of for liquid products to gaseous products (k2=4.4×103exp(−64629RT)). Moreover, the model infers that the major part of solid degradation leads to the formation of the gaseous product with the reaction rate constant of k3=5.7exp(−12905RT). The proposed model can provide an opportunity to predict the performance of the non-oxidative hydrothermal processing of organic solid waste.

Kinetics of pyrolysis of wood biomass under isothermal conditions

The paper discusses the results of a kinetic study of the pyrolysis of woody biomass (ordinary oak wood – Quercus robur) under static conditions at temperatures of 673, 773 and 873 K. In experiments, biomass samples weighing about 1.4 g were kept in a heating furnace for a certain period, after which their residual weight was measured and the degree of decomposition achieved was determined. A total of 7 series of experiments were performed: two series each at temperatures of 673 and 873 K and three series at a temperature of 773 K. The obtained results were analyzed in the framework of a single-stage chemical reaction (one-step global model), leading to a loss of the initial mass. It was established that from the phenomenological point of view, the pyrolysis of woody biomass under experimental conditions corresponds to the sigmoidal reaction model by Avarami–Erofeev with an exponent n ranging from 0.508 to 0.985. The use of the results of the first series of experiments led to an activation energy value of 57.2 kJ/mol and a pre-exponential factor value of 38 s–1. The other series of experiments gave an activation energy value of 64.9 kJ/mol and a preexponential factor value of 130 s–1. It is shown that the use of these values of the activation energy and the preexponential factor leads to agreement of the calculated values of the degree of decomposition of the studied biomass samples with the experimental ones in the range of values of the degree of decomposition from 0 to 1. The data presented in this work contribute to a more complete understanding of the kinetics of pyrolysis of biomass, which is necessary for the development of effective equipment for the thermochemical processing of vegetable raw materials.

Torrefaction of Leucaena Leucocephala under isothermal conditions using the Coats–Redfern method: kinetics and surface morphological analysis

The effects of temperature and holding times on the torrefaction of Leucaena Leucocephala (Leucaena) were elucidated via a novel isothermal decomposition approach. The torrefaction was performed in a fixed-bed reactor at temperature ranged from 200 to 300 °C for 20, 40 and 60 min. The effects of both torrefaction temperature and holding time were studied quantitatively and qualitatively by evaluating the distribution product yields and surface morphological changes. Quantitatively, the mass yield decreased with increasing temperature for all tested holding times, while the liquid and gas yields increased steadily due to the release of volatiles from the biomass decomposition. Qualitatively, significant morphological changes on Leucaena due to torrefaction were evidently captured via SEM imaging analysis. For torrefaction temperatures from 200 to 260 °C, the raw and torrefied Leucaena showed that pore evolution process had become evident. However, for torrefaction temperatures from 280 to 300 °C, the torrefied Leucaena revealed that the internal structure of torrefied Leucaena underwent pore development process. The pore development was noticeably observed for all temperatures. The values of activation energy (Ea) and pre-exponential factor (ln A) for the torrefaction were calculated based on the Coats–Redfern method for first order reaction. The values of Ea and ln A for 20, 40 and 60 min were found to be 39.75, 40.10 and 42.31 kJ/mol, and 3.92, 4.14 and 4.67. As a conclusion, the torrefaction of Leucaena from 200 to 300 °C for 20 min holding time is more reactive as compared to that at higher holding time.

Pyrolysis characteristics of soil humic substances using TG-FTIR-MS combined with kinetic models

The incorporation and cycling of pyrogenic organic matter in soil is a potential carbon sink, while the pyrolysis behaviors of soil organic matter are still lacking. Pyrolysis characteristics of soil fulvic acid (FA) and humic acid (HA) were investigated using thermogravimetry combined with Fourier transform infrared spectrometer-mass spectrometer (TG-FTIR-MS) and kinetic models. Four reaction stages corresponding to four pseudo-components were distinguished for both FA and HA. FA exhibited greater transformation contributions of hemicellulose-like and cellulose-like pseudo-components, while HA exhibited greater transformation contributions of lignin-like pseudo-components. Compared to HA, higher levels of heat-resistant aromatic compounds, phenolic groups, and carboxylic groups were recognized in FA. Values of both activation energy (Ea, 246.13–661.40 kJ·mol−1) and pre-exponential factor (lnA, 53.49–107.16 min−1) of FA were greater than corresponding Ea (241.74–466.70 kJ·mol−1) and lnA (51.99–74.36 min−1) values of HA determined by Flynn-Wall-Ozawa method and Distributed Activation Energy Model. The main pyrolysis reaction mechanisms of both FA and HA closely matched with the order-based model corresponding to 2nd and 3rd order random nucleation on an individual particle. The evolved gas species of H2, CH4, H2O, and CO2 were dominant for FA and HA pyrolysis. Generally, the total H2/CO2 and CH4/H2O releases were relatively larger for FA and HA pyrolysis, respectively. TG-FTIR-MS is shown to be an effective method to provide valuable and qualitative analysis of the gaseous volatile species evolved during HS pyrolysis. Findings from this systematic study of soil organic matter responding to pyrolysis will be critical for predicting the changes of soil systems or carbon cycle affected by future climate and fire regimes.

Barium calcium titanate solid solution: Non-isothermal kinetic analysis of Ca2+ incorporation into BaTiO3

This paper investigates the non-isothermal kinetic analysis of Ca2+ incorporation into BaTiO3 in Ba0.85Ca0.15TiO3 (BCT15) lead-free ferroelectric material, prepared via the solid-state reaction method, using differential scanning calorimetry (DSC) technique at multiple heating rates. The X-ray diffraction technique (XRD) has demonstrated the formation of pure cubic BaTiO3 phase when the BCT15 precursors were calcined at 1000 °C. Incorporation kinetics was analyzed by Freidman, Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) isoconversional methods. The results indicate that the incorporation process was carried out through a single-step. The kinetic parameters were determined through the combined kinetic analysis method. It was established that the incorporation mechanism follow perfectly the Avrami-Erofeev (A3) kinetic model. The values of activation energy (Ea) and preexponential factor (A) were found to be 388 kJ/mol and 4.1 × 1017 min−1, respectively. The obtained kinetic parameters are critical to better understand and optimize the incorporation process for BCT15 preparation with suitable and promising properties.

Kinetics Properties and Thermal Behavior of Pine Sawdust and Municipal Solid Waste

Waste resulting from economic activities has been an integral part of every human society. Effective waste management is considered to be consistent with improved quality of life through removal of potential hazards of uncontrolled disposal. Recent years has witnessed a number of sustainable energy recovery technologies developed to divert solid waste destined for landfills. Waste management is a global problem and therefore development of energy recovery technologies and at the same time serving dual purpose in its reduction has become a priority in recent years. The present study reports kinetics properties and thermal behavior of pine sawdust and municipal solid waste (MSW) using thermogravimetric analysis (TGA) and thus providing theoretical basis for development of energy recovery technologies. Results of this study have shown that the activation energy of both MSW and pine sawdust varies with temperature. The analysis of pine sawdust shows that it has activation energy (Ea) values of 26.19 kJ/mol., 87.46 kJ/mol. and 54.46 kJ/mol. At respective temperature ranges between 350 – 400K, 550 – 650K and 700 800K. MSW has activation energy between 72.91 kJ/mol. and 139.1 kJ/mol. at temperature ranges between 700 – 900 K and 500 – 600 K respectively. The estimated value of pre-exponential factor for pine sawdust was determined to have the values of 2.46 x 104, 1.6 x 1010 and 5.32 x 1016 (s-1) with temperature ranges between 350 – 400 K, 550 – 650 K and 700 800 K respectively. Municipal solid waste has the values of 3.01 x 1012 and 7.31 x 103 (s-1) with a temperature range of 500 – 600 K and 700 – 900 K respectively. From these findings, it has been determined that MSW and pine sawdust available in Arusha and Kilimanjaro possess energy recovery potentials.