Study Of Thermal Decomposition Research Articles

The Study of Thermal Decomposition of Rice Husk in Silica Production: The Effect of Hydrochloric Acid Leaching

The effect of hydrochloric acid leaching on thermal decomposition process and morphology of the rice husk in silica production have been investigated. Amorphous silica can be obtained by thermal decomposition of rice husk in acid solution. The aim of this study is to investigate the stages of thermal decomposition of rice husk and its morphology. In this work, thermal decomposition of rice husk has been investigated in neutral and acid solution (hydrocloric acid 1%v/v, 3%v/v). The thermal decomposition study was performed at 225°c, 450°c, 700°c. The thermal behavior were investigated using DSC while the microstructure and properties of rice husk were characterized by SEM, FTIR, XRD. The results showed that the pre-treatment of the rice husk with acid leaching accelerated thermal decomposition of organic components at slight lower temperature as showed by differential scanning calorimetry (DSC) and scanning electron microscope (SEM) analysis. This knowledge may provide better insight in order to obtain high grade amorphous silica.

Thermal behavior, compatibility study and safety assessment of diammonium 5,5′-bistetrazole-1,1′-diolate (ABTOX)

Thermal decomposition study of diammonium 5,5′-bistetrazole-1,1′-diolate (ABTOX) was investigated by using DSC. The result showed that ABTOX is less thermal sensitive than TKX-50. The kinetic parameters (E = 139.82 kJ mol−1 and lgA = 12.75 s−1) for thermal decomposition reaction of ABTOX were obtained. The compatibility of ABTOX with 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaza-isowurtzitane (CL-20), 3-nitro-1,2,4-triazol-5-one (NTO), 1,1-diamino-2,2-dinitroethene (FOX-7), 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), aluminum powder (Al), Estane-TPU-5702 and two kinds of fluoropolymers (F-2311 and F-2603) were evaluated by using DSC. The results showed that CL-20/ABTOX, FOX-7/ABTOX and F-2603/ABTOX were exhibiting good compatibility and RDX/ABTOX and Al/ABTOX had moderate compatibility. In addition, the compatibility of ABTOX with Estane-TPU-5702 and F-2311 was not good. HMX/ABTOX, NTO/ABTOX and LLM-105/ABTOX had poor compatibility. Furthermore, the self-accelerating decomposition temperature was calculated to be 152 °C and 150 °C in commercial wooden and PE cylinder, respectively.

Bioenergy potential of red macroalgae Gelidium floridanum by pyrolysis: Evaluation of kinetic triplet and thermodynamics parameters

The aim of this study was to investigate the bioenergy potential of red macroalgae GF by evaluating its biofuel physicochemical characteristics, and conducting a kinetic study and thermodynamic analysis of pyrolysis for the first time. The thermal decomposition study was performed at low heating rates (5, 10, 20 and 30 °C min−1) under N2 atmosphere. The thermal behavior of GF pyrolysis indicated the presence of three different decomposition stages, which are associated with different components in its structure and consequently influence the kinetic and thermodynamic parameters. The kinetic triplet obtained for GF provided a suitable description of experimental thermal behavior. The thermodynamic parameters demonstrated that GF is as a new promising feedstock for bioenergy and presented a similar potential to well-known bioenergy feedstock.

Valorisation of biomass pellets to renewable fuel and chemicals using pyrolysis: characterisation of pyrolysis products and its application

ABSTRACTThe pyrolysis of biomass (agro and garden waste) pellets in the temperature range of 200–600°C is studied in the present work. The pyrolysis of biomass pellets in a batch reactor generates mainly CO2 and CO gases at 300°C and H2 gas along with C1-C3 hydrocarbons at 600°C. The yield of non-condensable gases, liquid products and biochar was 30, 38 wt.% (30 wt.% bio-oil, 8 wt.% water), and 32 wt.%, respectively. The MS analysis of the bio-oil depicted the presence of light oxygenates, furans, anhydrosugars, and phenolic compounds. The biochar showed porous and macrostructure with various surface functional groups. A kinetic study of thermal decomposition of biomass pellets was performed along with a reaction mechanism of the product formation during the pyrolysis. Net energy return calculations depicted that the pyrolysis system can be self-sustained. The present study demonstrates the possible conversion of biomass pellets into useful products such as acids, aldehydes, phenolic compounds and carbonaceous char.

Synthesis, characterization and the use of organotin(IV) dithiocarbamate complexes as precursor to tin sulfide nanoparticles by heat up approach

The reactions of dimethyltin(IV)chloride with different N-alkyl-N-phenyl dithiocarbamate ligands in 1 mol equivalence yielded complexes of the type [(CH3)2SnL1L3] (1) and [(CH3)2SnL2L3] (2), where (alkyl = methyl (L1), ethyl= (L2) and butyl (L3). The complexes were characterized using spectroscopic techniques (FTIR, 1H, 13C and 119Sn), and elemental analysis. The crystal structure of complex (1) was also reported. The geometry of the complex is octahedral around the tin ion; two dithiocarbamates acted as bidentate chelating ligands through the sulfur atoms at the opposite ends to the tin atom of the organotin group. The dithiocarbamato ligands showed unequal distances to the tin center, resulting in asymmetrical unit and distortion of the expected octahedral geometry. Thermal decomposition studies of all the complexes (using TGA/DTG under nitrogen) indicated different decomposition pathways and the formation of tin sulfide (SnS, with Herzenbergite structure) as final residues. However, the thermolysis of these complexes using the heat-up method at a temperature below 300 °C and in the presence of a capping agent (oleylamine) afforded a different phase of tin sulfide (SnS2, with Berndtite structure). The as-synthesized nanoparticles (NPs), represented as SnS2 (1) and SnS2 (2) for the tin sulfides synthesized using complexes (1) and (2) respectively, were characterized using XRD, TEM and UV spectrophotometry. The average particles sizes of both SnS2 NPs were found to be approximately 2.0 nm, which agrees well with the calculated size from the XRD peak (001) obtained as 2.34 nm for SnS2 (1) and 2.94 nm for SnS2 (2). The optical properties showed that both types of nanoparticles exhibited a blue shift in their band gap energy with respect to their bulk.

Radicalic cleavage pathway and DNA docking studies of novel chemotherapic platinum agent of 5,6-di-2-ithienyl-2,3-dihydropyrazine

A new Pt(II) complex of the general formula ([PtCl2(L)]·H2O), where L is 5,6-di-2-thienyl-2,3-dihydropyrazine is synthesized as a potential antitumor agent and its structure is elucidated using a variety of physical and chemical procedures. DNA attaching ability of the complex is studied spectroscopically. UV and fluorometric titration, viscometric measurements and thermal decomposition studies agreed that two binding mode of actions, covalent and non-covalent bindings, are possible simultaneously. DNA helix cleavage studies clearly indicated OH• radical pathway in the presence of the reducing agent. Quantum mechanical calculations are carried out to call the minimum energy structures of the ligand and the complex, and to determine the FTIR, 1H NMR and UV–Vis spectra using the density functional theory (DFT) at the B3LYP/LANL2DZ level of theory. Calculated geometrical parameters for the complex indicated a square-planar structure around the metallic center through the dithiopyridyl ring and two chlorine atoms. The minimum energy structure of the complex obtained from DFT conformational analysis is used in docking studies to investigate complex-DNA binding mechanisms. The complex interacts with DNA through three different mechanisms, namely, intercalation, covalent and electrostatic interaction. The most stable mode of interaction with lowest binding energy (–333.6 kcal/mol) was intercalation mode. Comparisons between theoretical and experimental findings are performed and a good agreement is obtained.

Получение изоцианатов на примере бутилизоцианата термолизом карбаматов

Butyl isocyanate is widely distributed as a precursor for the production of a number of biologically active substances: fungicides, preservatives, insecticides, personal care products, etc. Nowadays, there are a number of methods for the preparation of isocyanates, which can be divided into liquid phase and gas phase. One of the perspective methods for the production of isocyanates is the thermolysis of carbamate and/or the actions of various reaction activating agents, accompanied by the elimination of alcohol, but this process is reversible, which greatly complicates its use in industry. The paper presents the results of studies of non-catalytic thermal decomposition of N-alkylcarbamates with the formation of alkylisocyanates on the example of butylisocyanate in the gas phase, flow reactor in a wide temperature range (200 to 450 °C). In addition, a series of experiments was carried out using a catalyst, dibutyltin dilaurate, in order to reduce the thermolysis temperature and increase the yield of the final product. To implement the isocyanate production process, an experimental laboratory setup, consisting of a gas flow meter (argon) regulator, a packed column (for heating) and a sorption solution tank, was developed and tested. The thermolysis of N-n-butylcarbamate was carried out in two variations: the preparation of an individual n-butylisocyanate and the passage of reaction products through a sorption solution linking the n-butyl isocyanate to N-n-butyl-N '-(1-phenylethyl)urea, which allows to estimate the yield of the target n-butylisocyanate without additional losses. The analysis of the obtained substances was carried out by high performance liquid chromatography with a UV detector (target product) and a mass detector (analysis of by-products). According to the results of research, a modification of the laboratory facility was proposed, as well as n-butylisocyanate was obtained with a yield of 49% on the basis of a new technique.

Thermal decomposition kinetics of a coumarin based copolymer: Poly(3-benzoyl coumarin-7-yl-methacrylate:0.54-co-methyl methacrylate:0.46)

In present study, thermal decomposition studies of a copolymer based the coumarin containing monomer 3-benzoyl coumarin-7-yl-methacrylate (BCMA) and methyl methacrylate [poly(BCMA:0.54-co-MMA:0.46)] were performed by thermogravimetric analysis (TGA). The temperature for maximum rate losses was increased from 384.81 °C to 407.45 °C with the increasing in heating rate from 5 °C/min to 20°C/min. The thermal decomposition activation energies of copolymer in the conversion range of 9% - 21% were resulted to be 212.98 kJ/mol and 210.30 kJ/mol by Kissinger’s and Flynn–Wall–Ozawa methods, respectively. The study of kinetic equations such as Coats-Redfern, Tang, Madhusudanan and Van-Krevelen methods exhibited that the thermal decomposition process of the studied copolymer was followed with a D3 mechanism, a three-dimensional diffusion type deceleration solid state mechanism, at the optimum heating rate of 20 °C/min.

Thermal decomposition of solid benzoyl peroxide using Advanced Reactive System Screening Tool: Effect of concentration, confinement and selected acids and bases

Benzoyl peroxide (BPO) is one of the most commonly used industrial organic peroxides; however, thermal decomposition of BPO is self-accelerating and can cause fires and explosions; therefore, thermal behavior of BPO decomposition needs to be understood clearly. In this paper, the experimental study of thermal decomposition of solid benzoyl peroxide (BPO) was conducted using the Advanced Reactive System Screening Tool (ARSST). The “onset” temperatures of 75% BPO and 98% BPO were determined to be 98 °C and 79 °C. The confinement tests showed that adding initial pressure can decrease the “onset” temperature, as well as increase the maximum self-heating rate, maximum pressure rise rate, and maximum temperature. Isothermal aging tests were conducted to study the effect of induction. A higher isothermal temperature shortened the induction time. The results showed that BPO can decompose at 75 °C if held at this temperature for a period of time, and the “onset” temperature in isothermal tests can be much lower than that measured in dynamic screening tests. In addition, effect of selected acids and bases on BPO thermal decomposition were investigated. All the additives had little impact on the BPO decomposition reaction under the tested conditions. Further experiments are needed to investigate the thermal hazards of mixtures. Our research is the first in the literature to study BPO decomposition using ARSST and the results provide useful information to characterize hazardous decomposition, and design safe measures during drying, storage, and transportation of BPO.

A study on catalytic depolymerization of a typical perhydrous coal for improving tar yield

Catalytic depolymerization proposed by our team was used on the thermal decomposition study of a typical perhydrous coal for improving the tar yield. The products from the coal catalytic depolymerization with or without a small amount of ZnCl2 or CoCl2 catalysts were investigated and compared. The composition of the tar and the structure of the coal char were characterized by a comprehensive two-dimensional gas chromatography coupled with mass spectrometric detection (GC × GCMS), thermogravimetric analysis (TGA), Raman spectrum and Elemental analysis, respectively. Compared with 8.21% of tar yield generated from the depolymerization of the raw coal, the tar yield increased to 9.19% and 10.02% when ZnCl2 and CoCl2 catalysts were added, respectively. The light fractions of tar also increased from 81.71% to 84.02% and 84.51%, respectively. Meanwhile, the yield of the aromatic ring components (> 3 fused benzene rings) and the ratio of aromatic rings with six or more fused benzene rings in the tar decreased. Further analysis reflected that the addition of catalysts in the catalytic depolymerization process could facilitate the cracking of more Cal-O bonds and precipitate the reaction start at lower temperature, which finally increases the volatiles released during the depolymerization stage.

Thermogravimetric Analysis of Rubber for Forensic Purposes: A Case Report

The main objective of this study was to determine the inorganic elemental components and thermal behavior of rubber samples collected from crime scenes and to compare them with a control sample. Thermal decomposition study revealed that decomposition temperature of rubber samples by TGA collected from crime scene exhibit 1 and 2 were consistent with decomposition temperature of control rubber sample exhibit 3. The DSC analysis showed that the decomposition temperature of the rubber samples exhibits 1 and 2 were 378.3 and 377.1 0C, respectively, consistent with that of the control sample exhibit 3 (378.8 0C). The micro-XRF analysis showed that elemental composition of rubber samples exhibits 1 and exhibit 2 matched with that of control sample exhibit 3. Thermal analysis was shown to be an important tool for characterizing the thermal behavior of rubber samples. Rubber samples collected from the scene of the crime with the rubber sample from the suspect’s vehicle can prove very valuable objective evidence.

Group 10 metal complexes of dithiocarbamates derived from primary anilines: Synthesis, characterization, computational and antimicrobial studies

Dithiocarbamate ligands obtained from primary amines, namely N-phenylaniline, 4-methylaniline and 4-ethylaniline, and represented as L1, L2 and L3 respectively, have been used to prepare some Ni(II), Pd(II) and Pt(II) complexes. The complexes were characterized by NMR, FTIR spectroscopy and elemental analysis. The spectroscopic data showed that the ligands were chelated to the metal ions in a bidentate mode. The complexes [Pt(L1)2], [Pt(L3)2], and [Pd(L1)2] were further characterized by single crystal X-ray analysis and distorted square planar geometries were confirmed in all cases. The magnetic susceptibility measurements of the nickel complexes suggest a square planar geometry for the diamagnetic compounds. Thermal decomposition studies of the complexes gave their respective metal sulfides as residues. Geometry optimization and harmonic frequency calculations of the ligands and the complexes were carried out using density functional theory (DFT). Molecular electrostatic potential energy calculations were used to support the coordination through the dithio-sulfur groups of the three dithiocarbamate ligands. Non-covalent interaction (NCI) theory analysis was used to reveal the different intra and intermolecular interactions in the hydrogen bonded structures of the platinum and palladium complexes. Antimicrobial screening, conducted using selected microbes, showed that the complexes gave moderate to very active antimicrobial activities against Gram negative (Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa), Gram positive (Bacillus cereus and Staphylococcus aureus) and fungi (Candida albicans and Aspergillus flavus) organisms at a concentration of at 50 μg/mL. However, the [Pt(L3)2] complex gave the best antimicrobial properties with an inhibitory zone range of 8–26 mm.

An experimental and kinetic study of thermal decomposition of phenanthrene.

Polycyclic aromatic hydrocarbons (PAHs) have enormous potential hazards. It is necessary for China to propose more internationally stricter standards for PAHs, in order to improve the country's pollutant prevention and control policy system, and ultimately, provide institutional guarantees for implementing PAH emissions prevention and control. In this study, phenanthrene, a typical PAHs generated during municipal solid waste (MSW) to energy system, was applied as a model compound to study the thermal degradation mechanism during the combustion process. Combustion kinetics for the three major gaseous products, including hydrogen, methane, and carbon dioxide, were determined. Experimental results indicated that hydrogen was promoted compared to methane and carbon dioxide during the combustion of phenanthrene, especially in high oxygen concentrations. The apparent activation energy (Ea) of 8.299-11.51, 13.10-23.07, and 9.368-15.29 kJ/mol, pre-exponential factor (A) of 0.219-1.579, 5.034-10.12, and 6.553-15.51 s-1, and the reaction order (n) of 1.160-1.234, 1.059-1.305, and 1.636-1.774 were obtained for hydrogen, methane, and carbon dioxide, respectively. Research on combustion behavior of phenanthrene and reaction kinetics provides the theoretical basis for the high-temperature removal of PAHs as byproducts during the combustion of MSW in oxygen-rich atmosphere.

Study of GaN-Based Thermal Decomposition in Hydrogen Atmospheres for Substrate-Reclamation Processing.

This study investigates the thermal decomposition behavior of GaN-based epilayers on patterned sapphire substrates (GaN-epi/PSSs) in a quartz furnace tube under a hydrogen atmosphere. The GaN-epi/PSS was decomposed under different hydrogen flow rates at 1200 °C, confirming that the hydrogen flow rate influences the decomposition reaction of the GaN-based epilayer. The GaN was completely removed and the thermal decomposition process yielded gallium oxyhydroxide (GaO2H) nanostructures. When observed by transmission electron microscopy (TEM), the GaO2H nanostructures appeared as aggregates of many nanograins sized 2–5 nm. The orientation relationship, microstructure, and formation mechanism of the GaO2H nanostructures were also investigated.

Numerical simulation and experimental study of thermal decomposition of cumene hydroperoxide in closed pressure vessel

Cumene hydroperoxide (CHP) is prone to thermal decomposition in chemical industry, but there are few reports on the related phenomena in the reactor when decomposition occurs. In order to reveal the complex phenomena of fluid-solid coupled heat transfer, two-phase flow and multi-phase chemical reaction in the CHP decomposition, computational fluid dynamics (CFD) approach was applied to simulate the decomposition of CHP with different mass in a closed pressure vessel. Based on a known reaction scheme and the kinetics evaluated from differential scanning calorimeter (DSC) results, a comprehensive CFD model of CHP decomposition was created. As a result, detailed information on the reaction course was obtained, and distribution of temperature, pressure, reaction rate, and flow velocity in the vessel were also investigated. Finally, closed pressure vessel tests (CPVT) were conducted to verify the validity of the CFD model. This work is conducive to deeply understand the thermal decomposition and reactive hazards assessment of CHP.

Numerical and experimental studies on decomposition and vent of di-tertbutyl peroxide in pressure vessel

Abstract Study of thermal decomposition and vent of di-tertbutyl peroxide (DTBP) is beneficial for accidents prevention in chemical engineering. In order to deep understand the thermal decomposition and vent behaviors of DTBP in a pressure vessel, both computational fluid dynamics (CFD) simulation and pressure vessel tests (PVT) were carried out. Based on the DTBP decomposition kinetics evaluated from differential scanning calorimeter (DSC) experiments, CFD numerical simulation was performed to reveal the fluid dynamic behaviors, temperature profile and flow field during the thermal decomposition and vent processes. PVT experiments were conducted to validate the numerical model. The results showed that the simulated and experimental data were in good agreement, thereby proving the validity of the numerical model and the DTBP decomposition kinetic model.

Study on Thermal Kinetics of nano Al/micro MnO2 Thermite System

In order to explore the thermal kinetics of nano Al-micro MnO2 thermite system, the Al/MnO2 thermite sample was mixed by the ultrasonic dispersion method. On the basis of the study of thermal decomposition of MnO2 powder, the thermal performance of the sample was study by simultaneous thermal analysis technique at the temperature range from room temperature to 1000°C, which could found the thermite reaction occurred in 650-660°C before the melting of Al, which belongs to solid state reactions with the 350 J/g heat releasing. Besides, the microstructure changes of the thermite during reaction were observed by field emission scanning electron microscope (FE-SEM). Based on the TG-DSC test with multiple heating rates and using of the activation energy calculated by Kissniger method, it could be proved the sample had good stability and safety performance.

Study on Thermal Chemical Reaction of Al/MnO2 Thermite

To explore the reaction characteristics and mechanism of Al/MnO2 thermite, selecting the high purity micron grade Al and MnO2 powder, the Al/MnO2 thermite sample was mixed by the ultrasonic dispersion method. On the basis of the study of thermal decomposition of MnO2 powder, the thermal performance of the sample was study by simultaneous thermal analysis technique at the temperature range from room temperature to 900°C, and the reaction products were analyzed by X-ray diffraction (XRD). The microstructure changes of the thermite during reaction were observed by field emission scanning electron microscope (FE-SEM). The results showed that the MnO2 has two processes of thermal decomposition during the temperature rising, and the reaction products were Mn2O3 and Mn3O4, and the onset temperature were 498.3°C and 781.5°C, the heat release were - 197.1J/g and -57.4 J/g, respectively. Al/MnO2 thermite reaction contained a variety of chemical reactions, including two thermal decompositions and thermite reactions. The Al powder melted at 648.9°C. The thermite reaction was started at 547.8°C, and the peak temperature was at about 590.3°C. The measured heat release was 323.9 J/g. Thermite reaction process coincides with the first thermal decomposition of MnO2. And the heat release of thermite reaction completely covered the endothermic decomposition.

Potassium alum thermal decomposition study under non-reductive and reductive conditions

Potassium sulfate (K2SO4) is a very important compound, mostly used as nutrient for plant growth. Potassium sulfate production can be accomplished through the Mannheim process. For potassium bearing silicate minerals, such as glauconite, one alternative is acid leaching followed by selective precipitation and thermal decomposition of potassium alum (KAl(SO4)2). This chemical process is responsible for the formation of soluble K2SO4 and insoluble Al2O3, which can be later separated after solubilization in water and filtration. In this pyrometallurgical reaction, the temperature control is very important. Through the addition of a reducing agent, the decomposition temperature could be significantly reduced. In the present work, the thermal behavior of synthetic samples of hydrated potassium alum (KAl(SO4)2·12H2O) is appreciated through thermogravimetric analysis (TGA), both in the absence as well as in the presence of a reducing agent (charcoal) under inert atmosphere (nitrogen) and dynamic analysis. The addition of a stoichiometric amount of the reducing agent stimulated considerably the decomposition, which started at a lower temperature in comparison with the pure alum sample. Based on the XRD characterization of selected samples, it is suggested that the decomposition process should happen in at least two stages, with Al2(SO4)3 as one of the intermediate reagents. After full decomposition, only Al2O3 and K2SO4 have been identified, as expected based on thermodynamic simulations. Finally, it was demonstrated that the K2SO4 formed could be totally transferred to aqueous solution after a solubilization carried out at 363K for two hours; the remaining solid was characterized as pure aluminum oxide (Al2O3).

Thermal decomposition study and pyrolysis kinetics of coal and agricultural residues under non-isothermal conditions

In this work thermal decomposition along with pyrolysis kinetics of two coals namely Chamalang Coal (CC) and Dukki Coal (DC) and four agricultural residues i.e. Rice Husk (RH), Corn Husk (CH), Sunflower Disc (SD) and Falsa Stick (FS) were investigated under non-isothermal conditions. Four different parameters were used to evaluate the reactivity of fuels. These were peak temperature, average rate of weight loss, maximum rate of weight loss and pyrolysis factor. All these parameters were evaluated at four heating rates 10, 20, 30 and 40 °C/min. The average rates of weight loss were found higher in devolatilization region compared with char formation region of degradation. It was found from reactivity analysis that the fuels could be ranked in following order of reactivity CH > FS > RH > SD > DC > CC. It was observed that increasing heating rate shifted the reaction zone to higher temperature and increased the peak temperatures, rate of average and maximum weight loss that increased the reactivity and pyrolysis factor. Coals showed low reactivities and high activation energies compared to agricultural residues. The activation energy has been estimated using Friedman differential isoconversional model and it was found that the activation energy varied with fractional conversion. The estimated average values of activation energy (kJ/mol) for CC, DC, RH, CH, SD, and FS were found to be 134.54, 129.81, 109.43, 98.24, 113.25, and 103.64 respectively.