FWO Methods Research Articles

Pyrolysis of corn cob: physico-chemical characterization, thermal decomposition behavior and kinetic analysis

Abstract Bioenergy out of lignocellulosic biomass, especially from agricultural crop residues, is making massive inroads in our quest for sustainable environment. In the present study, detailed physico-chemical characterization, thermal degradation characteristics, and kinetics of pyrolysis of corn cob are reported. Thermogravimetric experiments were performed at different heating rates, such as, 10, 20, and 30 °C/min in an inert atmosphere. Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves inferred the thermal behavior characteristics of corn cob. Significant content of cellulose and hemicellulose put together (76.23%) suggested tremendous potential of corn cob to give enhanced yield of bio-oil through pyrolysis. Maximum mass loss of 61.92% for corn cob was observed in the temperature range of 180–360 °C. The kinetic parameters for pyrolysis of corn cob were determined by employing model-free isoconversional methods like, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Starink. Activation energy from FWO (62.44 kJ/mol) and Starink (61.74 kJ/mol) method for pyrolysis of corn cob was found to be in close proximity. The results revealed prospective bioenergy potential of corn cob as a feedstock for pyrolysis process.

Synthesis, characterization, and thermal decomposition kinetics of copper hydroxide sulfate (Cu4(SO4)(OH)6) synthesized by chemical precipitation method

AbstractIn this study, copper hydroxide sulfate (Cu4(OH)6SO4) was synthesized by chemical precipitation using CuSO4 as the precursor material and the first time borax as basic precipitating agent. The synthesized samples were characterized using XRD, FTIR, and SEM. The decomposition kinetics of Cu4(OH)6SO4 were examined by the thermoanalytical procedures. It was obtained from TG‐DTG data that Cu4(OH)6SO4 has two‐region decomposition at elevated temperatures. Kinetic parameters of these regions were calculated by using both the model‐fitting and model‐free methods. In the decomposition of copper hydroxy sulfate, the mean activation energy for first region was calculated as 90.88 kJ mol−1 from KAS method and 91.47 kJ mol−1 from FWO method. The mean activation energy for the second region was 207.20 kJ mol−1 from KAS and 213.34 kJ mol−1 from FWO. The activation energies for first and second regions were obtained from Ortega method as 56.3 and 198.3 kJ mol−1, respectively.

Study of thermal degradation behavior and kinetics of ABS/PC blend

Abstract This work investigated kinetics and thermal degradation of acrylonitrile butadiene styrene and polycarbonate (ABS/PC) blend using thermogravimetric analysis in the range of 25 to 520°C. For thermal degradation of blend, activation energy (E a ) and pre-exponential factor (A) were calculated under various heating rates as 5, 10, 15 and 20°C/min using iso-conversional model-free methods (Kissinger, Flynn-Wall- Ozawa and Friedman). Mass loss of the blend as a function of temperature was plotted as thermogravimetric curve (TG) while derivative values of mass loss were drawn as derivative thermogravimetric (DTG) curve. Using Kissinger method, E a was 51.4 kJ/mol, while values calculated from FWO and Friedman method were 86–161 and 30–251 kJ/mol respectively. Results showed increasing trend of E a with higher conversion values indicating different degradation mechanisms at the initial and final stages of the experiment. Thermodynamic parameters such as enthalpy change (ΔH), Gibbs free energy (ΔG) and entropy change (ΔS) were also calculated.

Development and assessment of Moringa oleifera (Sahajana) leaves filler/epoxy composites: Characterization, barrier properties and in situ determination of activation energy

AbstractThis study concerns with investigation and analysis of hugely available, cost effective filler, obtained by grinding the Moringa oleifera leaves and its reinforcement in epoxy composites for semi‐structural applications. In this work, this novel filler is characterized by compositional analysis, FTIR, AFM, SEM, XRD, and TGA, along with the calculation of activation energy from two integral methods. To understand the interfacial surface chemistry of the fiber, X‐ray photoelectron spectroscopy (XPS) is also carried out. The size of filler was kept at 300 to 500 μm, and composites were prepared with five different loadings ranging from 5% to 25% using hand layup method of fabrication. The effect of varying loadings of filler on water uptake, mechanical, morphological, and thermal properties of its epoxy composites has been evaluated. Composites possess improved water resistance, tensile and flexural strengths in comparison with neat epoxy for an optimum loading of 20%, that is, 37 MPa. FWO and KAS methods are used to calculate the apparent activation energy of fillers. The apparent activation energy calculated from these methods comes to be 220 and 222 kJ/mol. The crystallinity index comes to be 55% which is comparable with other fibers. Approximately 12% increment in tensile strength and 10% in flexural strength takes place compared with neat epoxy at optimum fiber loading of 20%.

Thermal behaviors and kinetic analysis of two natural kaolinite samples selected from Qingshuihe region in Inner Mongolia in China

The thermal characteristic behaviors of two kaolinite samples selected from Qingshuihe region in Inner Mongolia in China were studied through thermogravimetry, derivative thermogravimetry, and differential scanning calorimetry (TG–DTG–DSC), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The activation energies of dehydroxylation for the two kaolinite samples (determined as Kaol-1 and Kaol-2) were calculated based on KAS and FWO methods. The XRD results indicated that Kaol-1 and Kaol-2 both were determined as kaolinite, and a small amount of quartz, but the Kaol-2 presented many amorphous organic matters. The TG–DSC results displayed the adsorbed water desorption and dehydroxylation with the temperature increased from 200 to 1100 °C. The dehydroxylation is followed as the intensities decrease in the bands at 3690 cm−1, 3620 cm−1 and 914.0 cm−1 attributing to the stretching mode of inner surface hydroxyls, and which disappeared when the temperature reached at 600 °C. The endothermic peak temperature of dehydroxylation for Kaol-2 presented higher than that of Kaol-1, which may be attributed to present of amorphous organic matter and was in agreement with the XRD data. The maximum endothermic temperature of dehydroxylation increased both for Kaol-1 and Kaol-2 with the increase in heating rate, which was attributed to more sufficient decomposition as the decrease in heating rate. The thermal kinetic analysis indicated that the dehydroxylation reaction of Kaol-1 should be a single kinetic mechanism, but the E of Kaol-2 decreased as α increasing from 0.2 to 0.5 and then gradually increased with the increase of α. The average E of dehydroxylation for Kaol-2 both was lower than that of Kaol-1 based on Kissenger–Akahira–Sunose and Flynn–Wall–Ozawa methods, which was attributed to the relatively higher organic carbon content in Kaol-2.

Kinetic Modeling of Pyrolysis and Combustion of High-Density Polyethylene-Based Polymer Mixtures

In this study, the pyrolysis and combustion of a binary mixture of most waste polymers (HDPE and PC) were investigated using MCC measurements at different heating rates of 0.25, 0.5, 1, 1.5 K/s. The non-isothermal kinetic analysis of mixture was conducted for equally mass fraction ratio of 50% HDPE and 50% PC, as well as for individual polymers. The activation energy was calculated by the isoconversional methods (Friedman, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa). The estimated activation energy on the conversion equals to 0.1-0.95. The Friedman method being more sensitive, as is shown by the variation of decomposition of PC and the first stage for a blend of HDPE/PC. As the equations used in FWO and KAS methods are derived assuming constant activation energy, which produces systematic errors in the estimation of Ea, so they have the same profile but FWO always is higher than KAS.

Thermal decomposition kinetics analysis of the oil sludge using model-based method and model-free method

Oil sludge (OS) is one of the main waste in the petrochemical industry, and serious consequences can result from the improper disposal of this waste. Pyrolysis is an effective method to dispose of OS and to recover the high heating value combustibles from it. The pyrolysis of three OS samples was carried out in a nitrogen atmosphere at heating rates of 5°C/min, 10°C/min, and 20°C/min, respectively. The TG-DTG/DSC-DDSC curves show that the thermal decomposition of OS has been divided into 5 stages, and each stage has unique thermal decomposition characteristics. Two model-free methods were used to calculate the apparent activation energy at a conversion rate from 0.05 to 0.95, and based on 10 solid-state mechanisms of thermal decomposition, the model-based method was used to fit the thermal decomposition mechanisms exposed to the three heating rates. The results show that the high heating rate is beneficial for the pyrolysis of OS. The apparent activation energy varies irregularly with the conversion rate, and the apparent activation energy error calculated by the FWO method is smaller. For the three samples, OS-1, OS-2 and OS-3, the average apparent activation energies calculated by the FWO method are 40.39kJ/mol, 38.01kJ/mol, and 85.53kJ/mol, respectively. The mechanism function of OS thermal decomposition changed, and the process of thermal decomposition should be described by a three-step thermal decomposition model. During 140.48–331.88°C, the fitting correlation coefficients of the two-dimensional phase interfacial reaction mechanism under the three heating rates were all above 0.99. During 400.00–556.57°C, the fitting result of the three-dimensional nucleation and growth mechanism is better than fitting results of other models. During 583.82–676.60°C, the two-dimensional diffusion mechanism has a good fitting regression. Significantly, model-based method and model-free method provide effective and reliable thermal decomposition kinetics parameters and models as a theoretical support for optimization of OS industrial pyrolysis and treatment of OS.

Cadmium removal from aqueous solution by jackfruit seed bio-adsorbent

In this present study, jackfruit bio-adsorbent was synthesized and utilized as cost effective for the removal of cadmium from aqueous solution. Jackfruit bio-adsorbent was characterized using emission scanning electron microscope, energy dispersive X-ray spectroscopy, thermal gravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffractive spectroscopy and inductively coupled plasma optical emissions spectrometer techniques. Effects of different parameters such as solution pH, dosage of adsorbent, stirring speed and concentration of cadmium removal were evaluated and optimized. The maximum adsorption was achieved at speed of 120 rpm, pH 7.6, 60 mg adsorbent dose and contact time for 1 h, the optimum adsorption efficiency of about 97.12% was observed even at lower adsorbent dosing of 60 mg. Activation energy of the jackfruit bio-adsorbent was also being evaluated, which was observed 130.69 kJ/mol using FWO method which attributed to a chemisorptions adsorption process.

Study on Thermal Degradation and Kinetic of Microencapsulated Red Phosphorus (MRP)/High Density Polyethylene (HDPE) Composite

Thermal degradation of the composite constituted by high density polyethylene (HDPE) and microencapsulated red phosphorus (MRP) were studied using thermogravimetric (TG) data obtained at different heating rates. The kinetic models and parameters of the thermal degradation of MRP/HDPE composite were evaluated by FWO, KAS and IKP method. It indicates that the activation energy E of 4 % MRP/HDPE composite is higher than HDPE for three methods. MRP could improve the thermal stability and slow down the thermal degradation of HDPE. With adding MRP, the degradation mechanism of HDPE is changed and the degradation rate decreases.

Investigating Catalytic Properties of Nanoferrites for Both AP and Nano-AP Based Composite Solid Propellant

ABSTRACT In this paper, the comparison studies of nanoferrites catalytic efficiency for thermal behavior of AP and nano-AP (NAP)-based CSPs were investigated. A co-precipitation procedure was used for the preparation of nanoferrites (CuNiF, CoMnF, and NiZnF) and NAP was synthesized using a non-aqueous method. XRD, FTIR, and SEM instruments were utilized for characterization of nanoferrites and NAP. The catalytic efficiency of nanoferrites on the thermal behavior of AP- and NAP-based CSPs was investigated by using TG-DSC technique. The KAS, FWO, and Starink methods were applied to estimate activation energies of AP- and NAP-based CSPs samples. Nanoferrites showed good catalytic efficiency on AP- and NAP-based CSPs that reduced the decomposition temperature and activation energy of AP- and NAP-based CSPs. The NAP-based CSPs with nanoferrites is more precious than AP-based CSPs with nanoferrites.

Analysis of Activation Energy of Epoxy Resin Insulated Transformer Based on Dynamic Method

Epoxy resin insulation transformer is a typical dry-type insulation equipment in power system. The insulation performance diagnosis of such equipment is the current research focus. This paper analyses the basic principles of two typical dynamic methods, FWO method and Kissinger method, and introduces the specific application methods of the two methods in the calculation of the activation energy of epoxy resin insulated transformers, which proves the effectiveness of the method. This article provides theoretical basis and example verification for insulation aging diagnosis of dry-type transformers based on quantitative characterization of activation energy.

Thermal kinetics involved during the solid-state synthesis of Cr2AlC MAX phase

The formation of nanolaminated Cr2AlC MAX phase by using solid-state synthesis route has been investigated through thermal analysis technique. The mixture of chromium (Cr), aluminum (Al) and graphite (C) in 2:1.4:1 was subjected to differential thermal analysis in an argon atmosphere and heated up to 1250 °C, at multiple heating rates (10, 20, 30, 40 °C min−1). Two endothermic peaks (~ 666 °C and ~ 1053 °C) are observed during the synthesis of Cr2AlC MAX phase. The formation of Cr2AlC is also confirmed through XRD, FESEM, HR-TEM and SAED analysis. The kinetic triplets (activation energy, pre-exponential factor and reaction mechanism) involved during the synthesis of Cr2AlC were estimated. The activation energy and reaction mechanism were determined by using iso-conversional model-free methods (KAS, FWO and FR methods) and integral master plot method, respectively. The results indicated that F2 (second-order) reaction mechanism dominates the formation of Cr2AlC MAX phase.

Synergistic effects of catalytic co-pyrolysis of macroalgae with waste plastics

This study unveiled the synergistic effects of catalytic co-pyrolysis of the macroalgae (Enteromorpha prolifera) and waste plastics (HDPE) for enhanced biofuels production. Results revealed that catalytic co-pyrolysis of macroalgae (seaweeds) and waste plastics lowered greatly the high contents of the acids, oxygenates and nitrogen-containing compounds in the seaweed bio-oils, while the aromatics and light hydrocarbons contents of the bio-oils were significantly increased, owing to blending of seaweeds with co-feeding element of high hydrogen content. Results also unveiled that the existence of the co-pyrolysis synergy inhibited catalytic coking and reduced solid residues’ formation. Also, the addition of HZSM-5 catalyst further improved the reaction activity, yields and selectivity of aliphatic hydrocarbons than aromatics, and reduced the activation energy without changing the reaction mechanisms. This significant reduction in activation energy can be easily observed in the results of non-isothermal kinetic analyses performed using the TGA data via five different methods: Friedman, FWO, Vyazovkin, KAS and DAEM methods, as a single kinetics-evaluation model lacks the flexibility to account for different types of materials without further modifications to reaction scheme. The FTIR-spectra of the catalytic co-pyrolysis oils were consistent with the results of the GC/MS analysis of the oils from catalytic-co-pyrolysis.

Study on the Pyrolysis Characteristics and thermal Kinetics of Tea

The pyrolysis characteristics of tea under nitrogen atmosphere were investigated, and the heating rate was 5, 10, 15, 20, 25 °C/min. The Kissinger and FWO methods were used to calculate the pyrolysis activation energy of tea. The results showed that the pyrolysis of tea can be divided into three pyrolysis stages: dehydration stage, rapid pyrolysis stage and carbonization stage. As the heating rate increasing, the peak temperature of the maximum pyrolysis rate shifts to the higher temperature, and the conversion rate increased at the peak of the maximum pyrolysis rate. The average value of pyrolysis activation energy of tea was 193.59 kJ/mol.

Thermal decomposition aspects and kinetics of pyrolysis of garlic stalk

ABSTRACT Agricultural crop residues are at the center stage of biomass utilization in view of their huge potential in the production of bio-oil and in turn bio-based chemicals. The present investigation aims to study comprehensive physico-chemical characteristics, thermal decomposition behavior, and kinetics of pyrolysis of garlic stalk using thermogravimetric analyzer at four heating rates (5, 10, 15, and 20°C/min). High volatile matter (71.2%) together high carbon (43.1%) content indicates prospective potential of garlic stalk for deriving bioenergy from pyrolysis process. Thermogravimetric analysis showed that the major mass loss in the form of devolatilization of volatile matter in garlic stalk was found to occur in the temperature range of 220 to 420°C. Model-free (FWO and KAS) and model-based (Coats-Redfern) methods were used to determine the kinetic parameters. The activation energy (94.54 kJ/mol) obtained from FWO was found to be in very good agreement with activation energy (95.11 kJ/mol) obtained from KAS method, which substantiates reliability of the obtained results. Further, Coats-Redfern method was used to determine the pre-exponential factor using the activation energy obtained from KAS and FWO methods. The experimental data for pyrolysis of garlic stalk was found to fit best with the contracting volume model (G3) from among various models.

The selective chlorination of nickel and copper from low-grade nickel-copper sulfide-oxide ore: Mechanism and kinetics

On account of the complex occurrence of valuable metals in a large amount of low-grade nickel sulfide ore, obstacles have been caused by using the existing metallurgical method. Therefore, we are reporting a new selective chlorination roasting and water leaching process to treat complex nickel sulfide ore. Anhydrous aluminum chloride was firstly used as the solid chlorination agent to sulfide ore. The chlorination mechanism for metals in nickel-copper sulfide ore were determined by thermodynamic calculation and experiment. The thermodynamic analysis showed that the predominant matter contributing to the chlorination of talc, lizardite, and magnetite were AlCl3 (both solid or gas) and the generated HCl, however, the chlorination of metal sulfide (pentlandite, chalcopyrite, and pyrite) were mostly contributed by the generated Cl2. The effect of roasting temperature, the roasting time, the mass ratio of AlCl3 to the ore, the content of O2 in the roasting atmosphere and the particle size of ore were investigated. The orthogonal experiments results showed that the optimal conditions of the chlorination roasting process were the roasting time of 3 h, the roasting temperature of 450 °C, the mass ratio of AlCl3 to ore of 1.5:1, the content of O2 of 20%, and particle size of the ore of 96–80 μm, under this condition, an extraction rate of nickel, copper, iron, and magnesium of 91.6%, 88.5%, 28.4%, and 16.4% was obtained. The chlorination mechanism is that, in the chlorination roasting process, nickel and copper were transferred into their corresponding metal chlorides, while most of the iron and magnesium were transferred into ferric oxide and magnesia-alumina silicates, respectively. TAK (thermal analytic kinetics) were used to clarify the chlorination kinetics, the results showed that the apparent activation energy calculated from DSC data was 70.4 kJ·mol−1, while calculated from TG data was 86.5 kJ·mol−1 (average) by using the FWO method, one of the most probable mechanism function of the chlorination process was G(α)=0.8701[1-(1-α)0.8701] (integral form) and f(α)=(1-α)1.8701 (differential form). The chlorination selectivity for metals could give guidance to the extraction of metals (especially for valuable metals) either in nickel sulfide ore or other minerals with a complex metal occurrence.

Thermal degradation of corn starch based biodegradable plastic plates and determination of kinetic parameters by isoconversional methods using thermogravimetric analyzer

Oil shortage and awareness of environment pollution leads to the extensive use of biodegradable starch-based materials against synthetic plastics. The accumulated wastes of these plastics takes more time for natural recycling and the process is complex. Therefore the best option of recycling would be to convert these polymers into a source of energy by pyrolysis. So to understand the pyrolytic behaviour, kinetics of such waste plastics is studied by using thermogravimetric analysis at different heating rates of 10 °C, 20 °C, 40 °C, 60 °C, 80 °C and 100 °C in nitrogen atmosphere followed by characterization of the pyrolysis products. The kinetic parameters are obtained for two major stages of decomposition in two different temperature ranges 250–620 °C and 620–855 °C by iso-conversional methods such as Friedman, Coats-Redfern, FWO and Kissinger methods. The regression coefficient data (>0.9) of kinetic plots obtained for different methods best fits to the kinetic equation. Empirical formula of the compound is determined by ultimate analysis is CH2.214S0.0018O0.6910. Proximate analysis gives the idea of volatile component which is74.33%. The range of average value of activation energy is 120.7013 kJ/mol to 140.7707 kJ/mol for the biodegradable plastic plate with different conversion (0.1–0.6) and (0.1–0.3) respectively at two different temperatures. The pyrolysis products obtained using a semi-batch reactor are characterized to know their composition and other properties.

Thermogravimetric analysis and kinetics characteristics of typical grains

We investigated the thermal decomposition behaviors of two typical grains, rice and corn, using a thermogravimetric analyzer at different heating rates. The pyrolysis process of rice and corn both can be divided into three stages, and the most possible pyrolysis mechanism of both rice and corn during devolatilization is a three-dimensional diffusion reaction, which can be represented by the Zhuravlev equation (G(α) = [(1 − α)(−1/3) − 1]2). Corn had a higher initial degradation temperature and end temperature as well as a higher mass loss in the second stage than rice. The average Ea of rice determined by Kissinger, FWO and Friedman method was 143.6 kJ mol−1, 161.6 kJ mol−1 and 148.7 kJ mol−1, respectively. The average Ea of corn determined by Kissinger, FWO and Friedman method was 166.1 kJ mol−1, 146.3 kJ mol−1 and 170.4 kJ mol−1, respectively. A lower Ea of rice than corn also indicates that rice is easier to be pyrolyzed. The predicted values using the kinetic parameters calculated show a good agreement with the experimental data at all the four heating rates. The results presented herein could provide guidance for storage of grains.

Pyrolysis of oleaginous yeast biomass from wastewater treatment: Kinetics analysis and biocrude characterization

Pyrolysis of Trichosporon fermentans biomass, a type of oleaginous yeast from the fermentation of refined soybean oil wastewater, was studied in the present work. Based on the TG/DTG curves, the activation energy values for the thermal decomposition of Trichosporon fermentans biomass were evaluated by the KAS method (111.69 kJ/mol) and FWO method (116.93 kJ/mol), respectively. The pyrolysis behavior was represented by considering the parallel degradation of four components, namely carbohydrates, proteins, lipids, and others, and the fitting degree of the simulated curve was over 0.99. According to the FTIR spectra of the end-products, the increasing hydrocarbons at a temperature around 400 °C indicated the lipid degradation. Biocrude oil was collected from a fixed bed reactor and the chemical composition was characterized by GC-TOF/MS. The yield of hydrocarbons in the bio-oil was identified as being over 28% when the pyrolysis temperature was higher than 500 °C, whilst the content of nitrogen compounds was less than 18%. The fractional yield distributions of the end-products at different pyrolysis temperatures were compared and the maximum yield of bio-oil was achieved (around 42%) at 500 °C. This study proposed a cost-effective and environmentally friendly method for the preparation of biofuel from oleaginous yeast pyrolysis.

Thermal kinetics and reactive mechanism of cellulose nitrate decomposition by traditional multi kinetics and modeling calculation under isothermal and non-isothermal conditions

Cellulose nitrate, also known as nitrocellulose (NC), is a highly flammable energetic cellulose derivatives formed by exposing cellulose to nitric acid, whose producing procedure has been greatly employed in daily life and military area. In this study, to explore its pyrolysis and combustion kinetics, NC samples were subjected to isothermal and non-isothermal DSC experiments. The isothermal experiments were carried at 150, 155, 160, and 165 °C, while the non-isothermal experiments were taken at 2, 4, 8, and 10 °C min−1 for heating rates. By model fitting methods, several classical reaction models with high fitting degree were obtained. The model corresponding to isothermal conditions was f(α) = 4(1 − α)[−ln(1 − α)]3/4, while for non-isothermal conditions the model was identified as f(α) = (1 − α)3. The variation of activation energy with conversion was calculated by model free methods including FR, KAS, FWO, and advanced Vyazovkin methods. Finally, based on the results of kinetic analysis, the adjustment function was introduced and the accurate reaction mechanism functions of NC were identified for isothermal and non-isothermal conditions, respectively. This study has a high guiding significance for the thermal decomposition and combustion kinetics of NC under isothermal and non-isothermal heating conditions.