Distribution Of Activation Energies Research Articles

Insights into pyrolytic feedstock potential of date palm industry wastes: Kinetic study and product characterization

This paper aims to study the pyrolysis characteristics of primary residues from industrial date palm processing, namely Fruit stalks pruning (FSP) and Date Palm petiole (DPP) biomasses, and evaluate their potential as a raw material for the pyrolysis process. TG-DTG analyses were performed on the raw material FSP and DPP to inspect the thermal degradation of samples at a range of heating rates within an inert atmosphere. Kinetic parameters, such as activation energy and pre-exponential factor for pyrolysis of (FSP) and (DPP), were calculated by the Distributed Activation Energy Model. As for the kinematic parameters obtained, the activation energy ranged from 110.92 to 120.08 kJ/mol for FSP and from 113.90 to 132.39 kJ/mol for DPP. Pyrolysis experiments were performed using a fixed bed reactor at a heating rate of 15 °C/min−1. The maximum liquid product yield was acquired at 500 °C. For the syngas production, the highest yield was obtained at 600 °C. The highest production of bio-char at a low temperature of 450 °C, and it decreased considerably with rising temperature. Evaluation of the kinetic parameters with physicochemical analysis illustrates the promising bio-energy potential of the two studied biomasses.

An improved parallel reaction model applied to coal pyrolysis

The modeling of pyrolysis can help to understand, predict and optimize many industrial processes. This paper proposes an improved parallel reaction model which tackles the issues of precision and rationality of the popular DAEM (distributed activation energy model). The model was established by optimizing the parameters of sub-reactions, which were estimated via analyzing TG-MS-FTIR (thermogravimetry-mass spectrum-Fourier transform infrared) data of a bituminous coal. The pyrolysis of coal was divided into six sub-reactions corresponding to the primary and secondary pyrolysis at different temperature intervals; including the decomposition of peroxides and carboxylic acids at low temperature, the formation of aliphatic hydrocarbons, aromatics and phenols at medium temperature, and the secondary reactions of aldehydes, ketones and alcohols at high temperature. As heating rate increased, the reaction temperature shifted towards the high region while the overlap of sub-reactions became deeper. The proposed parallel reaction model is bound to provide more accurate predictions of coal pyrolysis and sheds light on the quantitative prediction of fast pyrolysis.

Study on the Mechanism and Kinetics of Waste Polypropylene Cracking Oxidation over the Mn2O3/HY Catalyst by TG–MS and In Situ FTIR

The low temperature and high efficiency cracking oxidation of organic solid waste over the bifunctional catalyst with both acidity and oxidizing property is an environmentally attractive technology. In this study, the reaction mechanism and kinetics behavior of waste polypropylene (PP) during catalytic cracking oxidation processes were investigated utilizing thermo-gravimetry (TG), differential scanning calorimetry, TG–mass spectrometric, and in situ Fourier transform infrared (in situ FTIR) spectroscopy. PP was cracked into low-molecular weight organic substances (ester, ketone, etc.) over acid sites, which were further oxidized to CO2 and H2O over oxygen vacancy in the Mn2O3/HY catalyst. The kinetics of catalytic cracking oxidation of pure PP and PP over different model catalysts was analyzed by Gauss-Peak function and the distributed activation energy model (DAEM). The catalytic oxygenation apparent activation energy (E) values of pure PP and PP over Mn2O3, HY, and Mn2O3/HY catalysts were 130–190 kJ/mol, 200–618, 108–228, and 41–99 kJ/mol, respectively. DAEM expressed appropriately the various changing trends of E in the reaction process. This theoretical basis of the catalytic cracking oxidation process of polymers would provide a reference for the design and optimization of the reactor and application upgrade of engineering.

Evaluation of Hot Workability of Nickel-Based Superalloy Using Activation Energy Map and Processing Maps.

The stress-strain curves for nickel-based superalloy were obtained from isothermal hot compression tests at a wide range of deformation temperatures and strain rates. The material constants and deformation activation energy of the investigated superalloy were calculated. The accuracy of the constitutive equation describing the hot deformation behavior of this material was confirmed by the correlation coefficient for the linear regression. The distribution of deformation activation energy Q as a function of strain rate and temperature for nickel-based superalloy was presented. The processing maps were generated upon the basis of Prasad stability criterion for true strains ranging from 0.2 to 1 at the deformation temperatures range of 900–1150 °C, and strain rates range of 0.01–100 s−1. Based on the flow stress curves analysis, deformation activation energy map, and processing maps for different true strains, the undesirable and potentially favorable hot deformation parameters were determined. The microstructural observations confirmed the above optimization results for the hot workability of the investigated superalloy. Besides, the numerical simulation and industrial forging tests were performed in order to verify the obtained results.

Kinetic modeling of Indian lignites pyrolysis in the context of underground coal gasification (UCG)

Pyrolysis is an important step in combustion and gasification of any solid fuel. In this work, we have studied the kinetics of the pyrolysis of three Indian lignite samples via thermogravimetric experiments and mathematical modeling. Applicability of various kinetic models viz. the single global reaction model, the consecutive reaction model and the distributed activation energy model (DAEM) are evaluated. The kinetic parameters of the models were estimated based on the experimental data. Kinetics of the evolution of the volatile matter was studied independently by using a specially designed fixed-bed reactor and the relevant kinetic parameters were estimated.

Microalgae pyrolysis under isothermal and non-isothermal conditions

The present work analyzes and compares the non-isothermal and isothermal pyrolysis processes of two different kinds of microalgae: Spirulina platensis and Chlorella pyrenoidosa. The non-isothermal pyrolysis process is carried out in a Thermogravimetric Analyzer (TGA), whereas a macro-TGA bubbling fluidized bed reactor is used for the isothermal pyrolysis reaction. The simplified Distributed Activation Energy Model (DAEM) is employed to derive the kinetic parameters of the reaction in the TGA, i.e., the pre-exponential factor and the activation energy. A consecutive reaction, first-order pyrolysis model with three competitive pseudo-components for the released pyrolysis vapors is proposed to evaluate the isothermal pyrolysis experiments conducted in a macro-TGA bubbling fluidized bed. The fluidized bed experimental setup allows measuring the real-time mass evolution during the microalgae pyrolysis process, which could be used to obtain the kinetic parameters of the different reactions of which the consecutive reaction model is comprised. The activation energies of the reactions using this isothermal pyrolysis model are in good agreement, both qualitatively and quantitatively, with those obtained from the non-isothermal pyrolysis measurements run in the TGA. A quantitative comparison reveals that the TGA measurements could be employed to provide a useful first estimation of the activation energy of the isothermal pyrolysis process in the bubbling fluidized bed. Qualitatively, the Differential Thermogravimetric (DTG) curves obtained from the thermogravimetric analysis revealed the presence of three peaks in the Chlorella pyrenoidosa DTG curve and two peaks in the Spirulina platensis DTG curve, which is in agreement with the number of pseudo-component reactions in the isothermal pyrolysis model. This indicates the capability of the non-isothermal pyrolysis tests in a TGA to predict the number of reactions required to characterize the isothermal pyrolysis process.

Thermal effects of asphalt SARA fractions, kinetic parameter calculation using isoconversional method and distribution models

To discuss the thermal decomposition mechanism of asphalt materials, the kinetic parameters were calculated and their distribution models were established based on differential scanning calorimetry (DSC) test results of saturates, aromatics, resins and asphaltenes (SARA) fractions in asphalt. Results indicate that the thermal decomposition processes of SARA fractions are accompanied by complicated endothermic and exothermic reactions, and the exothermic reactions are predominant. The DSC curve is shifted to higher temperature when the heating rate is elevated, and the thermal effects, reaction progress and decomposition rate are increased simultaneously. Also, the Friedman–Reich–Levi (FRL) isoconversional method is suitable to calculate the kinetic parameters during the thermal decomposition of SARA fractions. The conversion ratio (α) of each SARA fraction shows obvious effects on the calculated activation energy (E). As the α of each SARA fraction is increased, the calculated E of saturates is more accurate at a lower α at the decomposition stages 1 and 3, but is always accurate at stage 2. Additionally, the calculated E is more accurate at the lower and higher α than that at the middle α at the two decomposition stages of aromatics. The calculated E of resins is fluctuated between 99 and 112 kJ mol−1, and its accuracy is satisfactory. The calculated E of asphaltenes is changed between 8 and 80 kJ mol−1, and is more accurate at the lower and higher α than that at the middle α. Finally, the distributed activation energy models of each SARA fraction are established to provide an insight into thermal decomposition mechanism of asphalt materials.

Organic matter variation within Upper and Lower Bakken shales of the Williston Basin by extracting kerogen pyrogram information

Activation energy distribution from kerogen kinetics study contains some integral characteristics of the host source rock thermal history over geological time scales. Extracting relevant information from pyrogram is critical for reconstruction of source rock maturation and hydrocarbon generation histories. In this study, in order to improve understanding of the Bakken shale source rock, we present a new quantitative kinetic model by inversion of Rock-Eval pyrograms of the Bakken Formation in Williston Basin. A group of core samples from both Upper and Lower Members of the Bakken Formation were collected for estimating transformation ratio (TR) and pyrolysis analysis, and an inversion method with different kinetic statistic parameters was designed and conducted using the source rock Tmax-Hydrogen Index covariation combined with different burial histories. The analysis of Rock-Eval results on Williston Basin samples from both Canada and US sides demonstrate basin-wide organic matter characteristics of Upper and Lower Bakken and identify variation of hydrocarbon generation histories. The Upper and Lower Bakken shales have different kerogen type characteristics based on activation energy distributions derived from Tmax-HI pair relationship, which suggest variance of the preserved algal materials for Upper and Lower Bakken. The modeling results by the thermal history analysis with the Rock-Eval dataset indicate a higher remanent generable kerogen in Lower Bakken shale, and the thermal maturity results will be valuable for integrated assessment of the hydrocarbon systems of Williston Basin accurately.

Kinetic Analysis of Algae Gasification by Distributed Activation Energy Model

Conversion of algal biomass into energy products via gasification has attracted increasing research interests. A basic understanding of the gasification kinetics of algal biomass is of fundamental importance. Distributed activation energy model (DAEM), which provides the information of energy barrier distribution during the gasification process, is a promising tool to study the kinetic process of algae gasification. In this study, DAEM model was used to investigate Chlorella vulgaris and Spirulina gasification. The activation energy of Chlorella vulgaris gasification was in the range from 370 to 650 kJ mol−1. The range of activation energy for Spirulina gasification was a bit wider, spanning from 330 to 670 kJ mol−1. The distribution of activation energy for both Chlorella vulgaris and Spirulina showed that 500 kJ mol−1 had the most components, and these components were gasified at around 300 °C. The DAEM algorithm was validated by the conversion and conversion rate from experimental measurement, demonstrating that DAEM is accurate to describe the kinetics of algal biomass gasification.

Characterization of Cornstalk and Bituminous Coal Based on Kinetic and Thermodynamic Parameter for Co-pyrolysis

The pyrolysis characteristic of bituminous coal (BC) and raw cornstalk (RC) were investigated through thermogravimetric analysis from environment temperature to 900 °C with 5, 15 and 25 °C/min. The distributed activation energy model (DAEM) was applied to estimate the kinetic parameters of samples. The average activation energy (E a) of BC, RC and the blended sample (mBC/mRC=6/4) were 304.56, 207.77 and 226.26 kJ/mol, respectively. The heat energies of the experiment to be needed was lower than that of calculation during co-pyrolysis, comparing with the theoretical calculation E a. To further researcher the thermal behavior during co-pyrolysis, the closeness of change in Enthalpy (ΔH) values vs. E a values for the blend indicated that activated complex formation may be favored because of lower potential energy barrier. Moreover, Gibbs free energy (ΔG) for the blend varied from 108.40 to 275.93 kJ/mol, the pyrolysis process was converted to disordered-state from ordered-state, considering the changes of Entropies (ΔS) loss.

Alkaline pyrolysis of anaerobic digestion residue with selective hydrogen production

Hydrogen (H2) production from biomass has attracted the research attention as it is renewable and clean. This work investigates the alkaline pyrolysis (AP) of corn stover digestate (CSD) with sodium hydroxide (NaOH) to promote the production of H2 and suppress carbon dioxide (CO2) at moderate conditions. It is observed that the H2 production is affected by the mass ratio of CSD to NaOH and reaction temperature. The H2 yield is enhanced from 1:1 to 1:2 ratio of CSD to NaOH (10.9–25.9 mmol g−1) with the purity of 81.21–84.98% at 500 °C, whereas a slight increase in H2 production at 1:3 ratio of CSD to NaOH is observed which may attribute to the mass transfer matter. The possible mechanism of AP is identified. Through the thermogravimetric analysis (TGA), distributed activation energy model (DAEM) was applied which evidences the catalytic ability of NaOH via the reduced activation energies.

Thermal behaviour, kinetics and fast pyrolysis of Cynodon dactylon grass using Py-GC/MS and Py-FTIR analyser

Cynodon dactylon (DG) is a biological resource available in abundance across the world; and has the capability to yield sustainable renewable fuels and fine chemicals. The present study explored the bioenergy potential of DG biomass by evaluating its physicochemical properties, pyrolysis characteristics, and kinetic behaviouer with thermodynamic analysis (TD) for the first time. The physicochemical outcome established its bioenergy potential towards sustainable energy production. The thermal decomposition study of DG biomass was carried out in a thermogravimetric analyser (TGA) at dynamic heating rates (10, 30 and 50 °C min−1), under nitrogen atmosphere while Py-GC–MS was executed to understand the pyrolysis behaviour. The thermal decomposition profile of the DG biomass established multistage degradation, which is linked to the diverse components in its structure. The average apparent kinetic energy was found to be 208.89, 220.43, 211.90, 213.66, 214.28 and 192.30 kJ mol−1 for Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), Friedman (FM), Starink (ST), Distributed Activation Energy Model (DEAM), and Vyazovkin (VZ). Py-GC–MS results revealed that formation of phenolics, aromatic hydrocarbons and ketones in the temperature range 450–650 °C were increased while formation of cyclopentanones, acids, esters and other oxygenated compounds were reduced. Finally, Py-FTIR study confirmed that the majority of functional groups generated in the range of 4 −15 s.

A modified DAEM: To study the bioenergy potential of invasive Staghorn Sumac through pyrolysis, ANN, TGA, kinetic modeling, FTIR and GC–MS analysis

Biomass is deemed to be an important contributor to satisfy our energy, chemicals and material requirements throughout the world. The present study aimed to study the bioenergy potential of Staghorn Sumac (SS) through modified distributed activation energy model (DAEM), kinetic models, thermogravimetric analyzer, elemental analyzer, Fourier transform infrared spectrometry (FTIR) and gas chromatography-mass spectrometry (GC–MS). Pyrolysis experiments were carried out at the different heating rates of 10, 20, 30 and 40 °C min−1 to study kinetics. The average activation energy values achieved through DAEM, KAS, FWO and Starink models were 160, 167, 169, and 168 kJ mol−1, respectively. Additionally, an Artificial Neural Network (ANN) model was equated with modified DAEM. Moreover, The composition of evolved gas compound measured by a gas chromatography coupled with mass spectroscopy showed that bio-oil mainly consisted of 82.33% acid, 6.37% aldehyde and ketone, 4.96% amid, 2.76% ester, 2.07% aromatic and alcohols, and 1.52% other groups. This study has revealed the remarkable potentials of Staghorn Sumac for clean bioenergy production.

On the characteristic heating and pyrolysis time of thermally small biomass particles in a bubbling fluidized bed reactor

Abstract Pyrolysis of crushed olive stone particles in a lab scale Bubbling Fluidized Bed (BFB) reactor was investigated. The time evolution of the pyrolysis conversion degree of the olive stone particles, while moving freely in the BFB, was determined from the evolution of the mass of olive stones remaining in the bed, measured by a precision scale holding the whole reactor installation. The experimental measurements of the pyrolysis conversion degree were employed to validate a simple model combining heat transfer and chemical kinetics, which is valid for thermally small particles. The model combines the Lumped Capacitance Method (LCM) and the simplified Distributed Activation Energy Model (DAEM) to account for heat transfer and pyrolysis chemical kinetics, respectively. The estimations of the combined LCM-DAEM model for the pyrolysis conversion degree were found to be in good agreement with the experimental measurements for the pyrolysis of olive kernels in a BFB operated at various bed temperatures, fluidizing gas velocities, and biomass particle size ranges. From the combined LCM-DAEM model, the characteristic heating time and the pyrolysis time of the olive stone particles were derived, obtaining a direct relation between these two parameters for constant values of the bed temperature.

Biomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western Himalaya.

The origin, transport pathway, and spatial variability of total organic carbon (OC) in the western Himalayan glaciers are poorly understood compared to those of black carbon (BC) and dust, but it is critically important to evaluate the climatic role of OC in the region. By applying the distribution of OC activation energy; 14C activity; and radiogenic isotopes of 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb in glacial debris and atmospheric particulate matter (PM10 size fraction), we demonstrate that 98.3 ± 1.6 and 1.7 ± 1.6% of OC in western Himalayan glaciers are derived from biomass and petrogenic sources, respectively. The δ13C and N/C composition indicates that the biomass is a complex mixture of C3 vegetation and autochthonous photoautotrophic input modified by heterotrophic microbial activity. The data set reveals that the studied western Himalayan glacier has negligible contributions from fossil-fuel-derived particles, which contrasts to the central and eastern Himalayan glaciers that have significant contributions from fossil fuel sources. We show that this spatial variability of OC sources relates to regional differences in air mass transport pathways and precipitation regimes over the Himalaya. Moreover, our observation suggests that biomass-derived carbon could be the only primary driver of carbon-induced glacier melting in the western Himalaya.

Thermal degradation kinetics of a lignin particle-reinforced phenolic foam

In the present work, the thermal degradation kinetics of a phenolic (PF) and lignin particle-reinforced phenolic (LRPF) foam and the lignin used as the reinforcement (LR) were studied. The activation energies of the degradation processes were obtained using a discrete distributed activation energy model (discrete DAEM) and the Vyazovkin model-free kinetic (MFK) method. The discrete DAEM was validated by comparing the predicted values with the data obtained at 8 °C min−1. Heating ramps of 6 and 12 °C min−1were used to calculate the kinetic parameters through the model. The effect of the reinforcement on the kinetics of the LRPF was studied by comparison with the results obtained for the PF. For reactions with non-zero mass fractions, the activation energies of the PF were in the range between 79.9 and 177.6 kJ mol−1, and the activation energy for the LRPF ranged from 91 to 187 kJ mol−1. For the LR, the activation energy values were in a narrower range than for the foams: 150–187 kJ mol−1. The degradation process of the LRPF was modified due to the use of LR: the range of activation energy for LRPF was between the ranges for the PF and LR. The activation energy dependence on conversion was also calculated using the Vyazovkin method and compared with the DAEM results; no compensation effect for the kinetic parameters was found.

Relaxation of internal friction and shear viscosity in Zr57Nb5Al10Cu15.4Ni12.6 metallic glass

Relaxation of internal friction of Zr57Nb5Al10Cu15.4Ni12.6 metallic glass was investigated by mechanical spectroscopy. The stress relaxation of internal friction with different aging temperature was described by Kohlrausch-Williams-Watts (KWW) equation. The shear viscosity behavior during linear heating can be interpreted as a result of the local irreversible structural relaxation with distributed activation energies. The results show that the dynamic heterogeneity and the atomic mobility are stimulated by the increasing annealing temperature.

Kinetic analysis of morphologies and crystal planes of nanostructured CeO2 catalysts on soot oxidation

Soot oxidation is a triple-phase reaction system involved in solid soot, solid catalyst and gaseous oxidant, which makes its kinetic behavior difficult to be determined. Herein, we report the kinetic behavior of crystal planes on the CeO2 catalysts with various morphologies for soot oxidation. We establish a kinetic model of crystal planes of CeO2 in soot oxidation by means of the distributed activation energy model (DAEM). Through analyzing the distribution function of apparent activation energies (f (Ea)) under loose contact condition, we discover that the Ea of the exposed (1 0 0), (1 1 1) planes and non-catalytic gaseous O2 on soot oxidation distributes in the range of 60–100, 100–150, and 150–250 kJ mol−1, respectively. Our findings show that compared with other catalysts, CeO2 nanocubes exhibit the higher intrinsic activity (turnover frequency, TOF) under loose contact condition, because of the higher f (Ea) value of abundant active exposed (1 0 0) planes located at the lower Ea range. Our work develops a methodology of kinetic analysis to investigate the soot oxidation reaction, which could be potentially extended to other complex oxidation systems.

Gas-pressurized torrefaction of biomass wastes: The effect of varied pressure on pyrolysis kinetics and mechanism of torrefied biomass

A novel gas-pressurized (GP) torrefaction of biomass waste was proposed in our recent work to deeply upgrade the biomass under the pressure of 5 MPa prior to their subsequent use in thermo-conversion technologies such as pyrolysis, combustion and gasification. However, the effect of varying pressure on the GP torrefaction process and the thermochemical behaviour of the torrefied biomass were not clear. In this work, the effect of varying torrefaction pressure on the pyrolysis kinetics and mechanism of GP torrefied biomass was studied in detail. It was revealed that the activation energy (Ea) of the GP torrefied biomass ranged from 195 to 198 kJ mol−1 increasing with torrefaction pressure, and their activation energy distributions were invariably wider compared to raw and torrefied biomass produced by atmospheric pressure torrefaction. The carbon and fixed carbon content, aromaticity, and crystallinity of the GP torrefied biomass were promoted by increasing the torrefaction pressure. On the other hand, the porosity of the GP torrefied biomass was reduced by elevated pressure. These are the reasons for the Ea increase of the GP torrefied biomass under elevated pressure. The presented kinetics and mechanism study provide a deep understanding of the novel GP torrefaction method.

Combustion kinetics and mechanism of biomass pellet

The effect mechanism of biomass pelletization on the property of bio-char, combustion kinetics and mechanism of pellet remain unclear. Therefore, in this work combustion behavior and kinetics of typical biomass pellets were investigated using TGA and Distributed Activation Energy Model. The bio-chars, from the pellets and raw biomasses, were also characterized in detail, to deeply understand the combustion mechanism of biomass pellet. The results showed that the activation energies of devolatilization stage of the pellet combustion were 118.1–230.2 kJ/mol, higher than that of raw biomasses, however, the activation energy decreased to 201.4–222.4 kJ/mol, for char combustion stage of pellet combustion, lower than the raw biomass. The compact physical structure of the biomass pellet caused by pelletization suppressed the mass and heat diffusion and thus enhanced the activation energy of devolatilization stage. The pelletization also suppressed the deoxygention, polymerization and aromatization reactions during the devolatilization stage, which caused higher reactivity of the pellet char than raw biomass char. This was the main reason for the lower activation energy of the pellet char combustion stage. Thus, the controlling factor of biomass pellet combustion is mass and heat diffusion for devolatilization stage, on the contrary, it was chemical reactions for char combustion stage.