Detailed kinetic modeling of pyrolysis of tetrabromobisphenol A

The thermal degradation of 4,4′-isopropylidenebis(2,6-dibromophenol), commonly known as tetrabromobisphenol A (TBBA), was studied by means of a semi-detailed kinetic model. TBBA is a widely adopted flame retardant. It decomposes in a temperature range between 200 °C and 500 °C, forming gaseous mixtures of HBr and harmful compounds such as bromine-containing phenols, the precursors of brominated dibenzo-p-dioxins (PBDDs) and dibenzofurans (PBDFs). These thermochemical characteristics constitute a significant risk of environmental contamination right throughout TBBA's whole life cycle. A kinetic model based on about 60 components (real and lumped species and radicals) and about 900 reactions satisfactorily reproduces the main aspects of TBBA degradation and volatilization. The model was validated by comparison with several thermogravimetric analyses, both isothermal and dynamic at 10 °C/min. The vaporization of pure TBBA, the formation of hydrogen bromide and of carbonaceous residue were all correctly predicted in quantitative terms right across the entire temperature range. Compared to conventional one-step global apparent degradation models, the proposed model spans much larger operating ranges, especially in predicting the gas phase products distribution. The results are encouraging and confirm the validity of the detailed kinetic model.     

Kinetic study of the pyrolysis and combustion of tomato plant

A kinetic study of the thermal decomposition of tomato plant has been carried out under different conditions by TG and TG–MS. A total of 24 experiments were performed in a nitrogen atmosphere (pyrolysis runs) and also in an oxidative atmosphere with two different oxygen concentrations (10% and 20% oxygen in nitrogen). Dynamic runs and dynamic + isothermal runs have been carried out to obtain many data of decomposition under different operating conditions.A scheme of five independent reactions for pseudocomponents has been proposed for the pyrolysis process, although only three fractions have probed to be significant, comparing the weight fractions of volatiles evolved with the hemicellulose, cellulose and lignin content of the plant. For the combustion runs, four new reactions have been added: two competitive oxidation reactions for the cellulose and lignin, and two combustion reactions of the carbonaceous residue obtained from pyrolysis. The kinetic parametres have been calculated by integration of the differential equations and minimizing the differences between the experimental and calculated values. It is important to emphasize that the same set of parameters has been proposed for the pyrolysis and combustion runs, and which do not depend on either the heating rate in dynamic runs or whether the run is carried out in a dynamic or isothermal mode. The influence of the oxygen pressure has been also discussed.     

Kinetic study of the pyrolysis of neoprene

Kinetics of neoprene thermal decomposition has been performed under dynamic conditions at different heating rates, between 5 and 80 °C/min in a TG apparatus. The same kinetic model has been applied simultaneously to runs performed at different heating rates and different atmospheres allowing a good correlation of the weight loss data. A mechanism based on three independent reactions has been used to model the thermal decomposition. The first reaction is of an order close to two, and the other two reactions are of order below one, similar to other plastic materials. Different alternatives for the mathematical treatment for fitting TG data were considered. The accuracy of the calculated kinetic parameters was studied by means of a sensibility analysis.     

Pyrolysis of textile wastes: I. Kinetics and yields

Thermal behavior of textile waste was studied by thermogravimetry at different heating rates and also by semi-batch pyrolysis. It was shown that the onset temperature of mass loss is within 104–156 °C and the final reaction temperature is within 423–500 °C. The average mass loss is 89.5%. There are three DTG peaks located at the temperature ranges of 135–309, 276–394 and 374–500 °C, respectively. The first two might be associated with either with decomposition of the hemicellulose and cellulose or with different processes of cellulose decomposition. The third peak is possibly associated to a synthetic polymer. At a temperature of 460 °C, the expected amount of volatiles of this waste is within 85–89%. The kinetic parameters of the individual degradation processes were determined by using a parallel model. Their dependence on the heating rate was also established. The pyrolysis rate is considered as the sum of the three reaction rates. The pyrolysis in a batch reactor at 700 °C and nitrogen flow of 60 ml/min produces 72 wt.% of oil, 13.5 wt.% of gas and 12.5 wt.% of char. The kinetic parameters of the first peak do not vary with heating rate, while those of the second and the third peak increase and decrease, respectively, with an increasing heating rate, proving the existence of complex reaction mechanisms for both cases.     

Are novel aryl phosphates competitors for bisphenol A bis(diphenyl phosphate) in halogen-free flame-retarded polycarbonate/acrylonitrile–butadiene–styrene blends?

The reactivity of the flame retardant and its decomposition temperature control the condensed-phase action in bisphenol A polycarbonate/acrylonitrile–butadiene–styrene/polytetrafluoroethylene (PC/ABS_PTFE) blends. Thus, to increase charring in the condensed phase of PC/ABS_PTFE + aryl phosphate, two halogen-free flame retardants were synthesized: 3,3,5-trimethylcyclohexylbisphenol bis(diphenyl phosphate) (TMC-BDP) and bisphenol A bis(diethyl phosphate) (BEP). Their performance is compared to bisphenol A bis(diphenyl phosphate) (BDP) in PC/ABS_PTFE blend. The comprehensive study was carried out using thermogravimetry (TG); TG coupled with Fourier transform infrared spectrometer (TG-FTIR); the Underwriters Laboratory burning chamber (UL 94); limiting oxygen index (LOI); cone calorimeter at different irradiations; tensile, bending and heat distortion temperature tests; as well as rheological studies and differential scanning calorimeter (DSC). With respect to pyrolysis, TMC-BDP works as well as BDP in the PC/ABS_PTFE blend by enhancing the cross-linking of PC, whereas BEP shows worse performance because it prefers cross-linking with itself rather than with PC. As to its fire behavior, PC/ABS_PTFE + TMC-BDP presents results very similar to PC/ABS_PTFE + BDP; the blend PC/ABS_PTFE + BEP shows lower flame inhibition and higher total heat evolved (THE). The UL 94 for the materials with TMC-BDP and BDP improved from HB to V0 for specimens of 3.2 mm thickness compared to PC/ABS_PTFE and PC/ABS_PTFE + BEP; the LOI increased from around 24% up to around 28%, respectively. BEP works as the strongest plasticizer in PC/ABS_PTFE, whereas the blends with TMC-BDP and BDP present the same rheological properties. PC/ABS_PTFE + TMC-BDP exhibits the best mechanical properties among all flame-retarded blends.     

An investigation on the solid state pyrolytic decomposition of bimetallic oxalate precursors of Ca,Sr and Ba with cobalt: A mechanistic approach

The mixed metal oxalate precursors, calcium(II)bis(oxalato)cobaltate(II)hydrate (COC), strontium(II)bis(oxalato)cobaltate(II)pentahydrate (SOC) and barium(II)bis(oxalato)cobaltate(II)octahydrate (BOC) have been synthesized and their thermal stability was investigated. The complexes were characterized by elemental analysis, IR spectral and X-ray powder diffraction studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound COC decomposed mainly to CaC₂O₄ and Co₃O₄ at 340 °C, and a mixture of CaCO₃ and Co₃O₄ identified at 510 °C. A mixture of CaCO₃ and Ca₃Co₂O₆ along with the oxides and carbides of both the cobalt and calcium were attributed at 1000 °C as end products. DSC study in nitrogen ascertained the formation of a mixture of CaO and CoO along with a trace of carbon at 550 °C. The mixture species, SrC₂O₄, CoC₂O₄ and Co₃O₄ were generated at 255 °C in case of SOC in air, which ultimately changed to CoSrO₃, SrCO₃ and oxides of strontium and cobalt at 1000 °C. The several mixture species also generated as intermediate at 332 and 532 °C. The DSC study in nitrogen indicated the formation of CoSrO_x (0.5 < x < 1) as end product. In case of BOC in air, a mixture of BaCoO₂, BaO, CoO and carbides are identified as end product at 1000 °C through the generation of several intermediate species at 350 and 530 °C. A mixture of BaO and CoO is identified as end product in DSC study in nitrogen. The kinetic parameters have been evaluated for all the dehydration and decomposition steps of all the three compounds using four non-mechanistic equations. Using seven mechanistic equations, the kind of dominance of kinetic control mechanism of the dehydration and decomposition steps are also inferred. The kinetic parameters, ΔH and ΔS of all the steps are explored from the DSC studies. Some of the decomposition products are identified by IR and X-ray powder diffraction studies.     

Non-isothermal decomposition kinetics,thermal behavior and computational detonation properties on 4-amino-1,2,4-triazol-5-one (ATO)

The thermal behavior of 4-amino-1,2,4-triazol-5-one (ATO) was studied under non-isothermal condition by DSC method in a sealed cell of stainless steel. The melting enthalpy and melting entropy of ATO are 21.34 ± 0.49 kJ mol⁻¹ and 46.54 ± 0.30 J mol⁻¹ K⁻¹, respectively. The kinetic parameters were obtained from the analysis of DSC curves by Kissinger method, Ozawa method, the differential method and the integral method. The main exothermic decomposition reaction mechanism of ATO is classified as nucleation and growth, and the kinetic parameters of the reaction are E_a = 119.50 kJ mol⁻¹ and A = 10^9.03 s⁻¹. The gas products and condensed phase products of the thermal decomposition of ATO were studied on two simultaneous devices of the fast thermolysis reaction cell (gas reaction cell) in situ in conjunction with rapid scan transform infrared spectroscopy (RSFT-IR) and the solid reaction cell in situ. The heat of formation (HOF) for ATO was evaluated by G3 theory. The detonation velocity (D) and detonation pressure (P) were estimated by using the well-known Kamlet–Jacobs equation, based on the theoretical HOF and the determined crystal density.     

Structure characteristics contributing to flame retardancy in diazo modified novolac resins

The physical characteristics of two modified novolac resins (carbonyl phenyl azo novolac resin; CPAN and 4-(4-hydroxyphenyl azo) benzyl ester novolac resin; HPDEN) bearing nitrogen and aromatic functional groups by diazo-coupling or esterification in the branch structure of phenol novolac resin were examined. Presence of the modifiers raised the phenolic decomposition temperature (5% weight loss) from 300 °C (pure Phenolic) to 330 °C and 380 °C, while the char residue increased from 45% to 56% and 68%, respectively. The kinetics for thermal degradation energies (E_a) also rose from 151 kJ/mol K to 254 kJ/mol K (CPAN) and 273 kJ/mol K (HPDEN). The retarded decomposition kinetics is attributed both to the increase of crosslink densities and high aromatic content in the derivative resins. On the other hand, the diazo-coupling or phenyl diazenyl ester produces non-combustible gases (N₂, CO₂ and CO) during formation of aromatic char which dilute the ambient oxygen gas. Both the production of gases and the retarded kinetics due to cross-linking are definitive for the improved flame resistance.     

Thermodynamic properties of 4-amino-3-furazanecarboxamidoxime

4-Amino-3-furazanecarboxamidoxime (AAOF) is an important precursor for synthesizing new furazano (furoxano) energetic compounds. Its thermal behaviour was studied under a non-isothermal condition by DSC methods. The results of this study show that there are one melting process and two exothermic decomposition processes. Its kinetic parameters of the intense exothermic decomposition process are obtained from analysis of the DSC curves. The apparent activation energy (E_a), pre-exponential factor (A) and the mechanism function (f(α)) were (146 ± 18) kJ · mol⁻¹, (10^10.9±1.8) s⁻¹ and (1 − α)², respectively. The specific molar heat capacity (C_p,m) of AAOF was determined by a continuous C_p mode of micro-calorimeter. The self-accelerating decomposition temperature (T_SADT), thermal ignition temperature (T_TIT) and critical temperatures of thermal explosion (T_b) were obtained to evaluate its thermal safety.     

In situ atom trapping of Bi on W-coated slotted quartz tube flame atomic absorption spectrometry and interference studies

Analytical performances of metal coated slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS) and slotted quartz tube in situ atom trapping flame atomic absorption spectrometry (SQT-AT-FAAS) systems were evaluated for determination of Bi. Non-volatile elements such as Mo, Zr, W and Ta were tried as coating materials. It was observed that W-coated SQT gave the best sensitivity for the determination of Bi for SQT-FAAS and SQT-AT-FAAS. The parameters for W-coated SQT-FAAS and W-coated SQT-AT-FAAS were optimized. Sensitivity of FAAS for Bi was improved as 4.0 fold by W-coated SQT-FAAS while 613 fold enhancement in sensitivity was achieved by W-coated SQT-AT-FAAS using 5.0 min trapping with respect to conventional FAAS. MIBK was selected as organic solvent for the re-atomization of Bi from the trapping surface. Limit of detection values for W-coated SQT-FAAS and W-coated SQT-AT-FAAS was obtained as 0.14 μg mL^− 1 and 0.51 ng mL^− 1, respectively. Linear calibration plot was obtained in the range of 2.5–25.0 ng mL^− 1 for W-coated SQT-AT-FAAS. Accuracy of the W-coated SQT-AT-FAAS system was checked by analyzing a standard reference material, NIST 1643e.     

Application of Design of Experiment (DoE) for Parameters Optimization in Compression Moulding for Flax Reinforced Biocomposites

Lately, widespread research on polymer composites that consist of natural fiber as reinforcement have been widely discussed. In this work, an attempt on optimizing the hot press forming process parameters using Response Surface Methodology (RSM) have been made to improve the mechanical properties of the woven flax/PLA composites. Three independent process variables, including moulding temperature, time and pressure were studied. Through the Box Behnken approach, a set of experiment runs based on various combination of compression moulding via Minitab 16 were established. As a results the optimum value for the variables of compression moulding technique parameters were 200 °C, 3 min and 30 bar in order to yield 48.902 kJ/m^-2ofimpact strength.     

Pyrolysis of biocollagenic wastes of vegetable tanning. Optimization and kinetic study

Three solid wastes generated from the vegetable tanning of bovine skin in the Leather Industry (shavings, trimmings and buffing dust) were mixed together in the same proportions in which they were produced and the mixture was then used as a pyrolysis precursor for this research study. The optimal pyrolysis conditions for obtaining energy from the generated fractions (char, tar and gas fraction), and the preparation of activated carbons from the carbonaceous material (char), were established. The final conditions were chosen from two different points of view, the thermogravimetric results (TG/DTG) obtained at different heating rates (2–20 °C/min) and an optimization of the pyrolysis parameters by means of experiments carried out in a conventional furnace. The pyrolysis conditions finally selected were: heating rate (5 °C/min), final temperature (750 °C), and time at final temperature (60 min) and inert gas flow (N₂ 150 ml/min). The carbonaceous material (char) obtained exhibits good properties as a solid fuel due to its high calorific value and relatively low ash content. It also shows suitable characteristics as a precursor for the preparation of activated carbons. The condensable fraction has a predominantly phenolic nature and contains significant amounts of nitrogen compounds (nitriles, diketopiperazines, etc.), alkanes, alkenes, acids and esters, derived from the decomposition of tannins and collagen, with possible industrial applications in the preparation of chemical products. The gaseous phase is rich in carbon monoxide and carbon dioxide, and also contains a certain amount of methane and hydrogen. The syngas content increases with the pyrolysis temperature. A kinetic study of the pyrolysis was carried out using a model of independent reactions. The variation in the heating rate produced a slight shift to higher temperatures of the decomposition peaks, although this did not significantly affect either the kinetic parameters of the degradation processes or the percentage weight losses.     

Kinetic spectrophotometric determination of hyoscine butylbromide in pure form and in pharmaceutical formulations

A simple and sensitive kinetic method was described for the determination of hyoscine butylbromide in pharmaceutical preparations. The method is based upon a kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 15 min. The absorbance of the colored manganate ion was measured at 610 nm. The absorbance–concentration plot was rectilinear over the range of 1.0–10 μg mL^?1 (r = 0.9999) and detection limit of 0.092 μg mL^?1. The concentration of hyoscine butylbromide was calculated using the corresponding calibration equation for the fixed-time method. The determination of hyoscine butylbromide by the fixed-concentration and rate constant methods is also feasible with the calibration equations obtained but the fixed-time method has been found to be more applicable. The different experimental parameters affecting the development and stability of the colors were carefully studied and optimized. The proposed method was applied to the determination of hyoscine butylbromide in pharmaceutical formulations. The results obtained were in good agreement with those obtained using the official British Pharmacopeial method (2004).     

Kinetics of thermal and photolytic degradation of decabromodiphenyl ether (BDE 209) in backcoated textile samples

Kinetics of the thermal and photolytic degradation of decabromodiphenyl ether (DBE 209) was studied using HPLC. Samples lost an amount of ∼8.4% (w/w), 24% (w/w), 39.4% (w/w) and 28.5% of the amount of DBE 209 originally present in the samples due to ageing at 25, 60, 90 °C and UV exposure, respectively. The thermal and photolytic release was found to follow the first order kinetics with rate constants estimated to be 3.6 × 10⁻³, 1.03 × 10⁻², 3.6 × 10⁻² and 3.94 × 10⁻² day⁻¹, respectively. Ageing of the textile samples enhanced the release of the DBE 209 from the backcoated textile. Photodegradation of BDE 209 into lower congeners of brominated flame retardants was also observed for the UV-aged samples.Migration of DBE 209 from the backcoated textile into biological fluids was studied using Head-over-Heels and contact-Blotting test for unaged, thermally and UV aged samples. The presence of biological fluids (sweat, saliva and juice) was found to enhance the migration of DBE 209 compared to water. Migration of BDE 209 into artificial biological fluids is significantly increased for samples previously exposed to UV radiation or thermally aged. An increase from 0.6% (w/w) to a maximum of 2% (w/w) of the amount of BDE 209 migrated into artificial biological fluids due to ageing conditions in the presence of biological fluid was recorded.     

Preconcentration procedure trace amounts of palladium using modified multiwalled carbon nanotubes sorbent prior to flame atomic absorption spectrometry: 1st Nano Update

A method for preconcentration of palladium at trace level on modified multiwalled carbon nanotubes columns and determination by flame atomic absorption spectrometry (FAAS) has been developed. Multiwalled carbon nanotubes (MWCNTs) were oxidized with concentrated HNO₃ and the oxidized multiwalled carbon nanotubes were modified with 5-(4′-dimethylamino benzyliden)-rhodanine, and then were used as a solid sorbent for preconcentration of Pd(II) ions. Factors influencing sorption and desorption of Pd(II) ions were investigated. The sorption of Pd(II) ions was quantitative in the pH range of 1.0–4.5, whereas quantitative desorption occurs with 3.0 mL 0.4 mol L^?1 thiourea. The amount of eluted palladium was measured using flame atomic absorption spectrometry. The effects of experimental parameters, including sample flow rate, eluent flow rate, and eluent concentration were investigated. The effect of coexisting ions showed no interference from most ions tested. The proposed method permitted a large enrichment factor (about 200). The relative standard deviation of the method was ±2.73% (for eight replicate determination of 2.0 μg mL^?1 of Pd(II)) and the limit of detection was 0.3 ng mL^?1. The method was applied to the determination of Pd(II) in water, road dust, and standard samples.     

A simple method of electrochemical lithium intercalation within graphite from a propylene carbonate-based solution

Electrochemical lithium intercalation within graphite from 1 mol dm^− 3 solution of LiClO₄ in propylene carbonate (PC) was investigated at 25 and − 15 °C. Lithium ions were intercalated into and de-intercalated from graphite reversibly at − 15 °C despite the use of pure PC as the solvent. However, ceaseless solvent decomposition and intense exfoliation of graphene layers occurred at 25 °C. The results of the Raman spectroscopic analysis indicated that the interaction between PC molecules and lithium ions became weaker at − 15 °C by chemical exchange effects, which suggested that the thermodynamic stability of the solvated lithium ions was an important factor that determined the formation of a solid electrolyte interface (SEI) in PC-based solutions. Charge–discharge analysis revealed that the nature of the SEI formed at − 15 °C in 1 mol dm^− 3 of LiClO₄ in PC was significantly different from that formed at 25 °C in 1 mol dm^− 3 of LiClO₄ in PC containing vinylene carbonate, 3.27 mol kg^− 1 of LiClO₄ in PC, and 1 mol dm^− 3 of LiClO₄ in ethylene carbonate.     

Electrochemical kinetic study of surface layer growth on natural pyrite in acid medium

This paper presents electrochemical experiments on natural pyrite that combine potentiostatic and voltammetric techniques. X-ray microanalysis is used as an auxiliary technique. The layer growth on pyrite surface is conducted in a wide range of pH and potential range: 3.4 ≤ pH ≤ 5.9 with E = 0.80 V (versus SHE), and 0.80 V ≤ E ≤ 1.00 V with pH 4.5 (versus SHE) in acetic acid–acetate buffer. This work is unique for two reasons: (1) phenomenological model about layer growth is applied and mathematical-physic consistence is verified and (2) Meyer's hypotheses of chemical mechanism are used to explain kinetic parameters of the phenomenological model.     

Characterization of the different fractions obtained from the pyrolysis of rope industry waste

A study of the possibilities of pyrolysis for recovering wastes of the rope's industry has been carried out. The pyrolysis of this lignocellulosic residue started at 250 °C, with the main region of decomposition occurring at temperatures between 300 and 350 °C. As the reaction temperature increased, the yields of pyrolyzed gas and oil increased, yielding 22 wt.% of a carbonaceous residue, 50 wt.% tars and a gas fraction at 800 °C. The chemical composition and textural characterization of the chars obtained at various temperatures confirmed that even if most decomposition occurs at 400 °C, there are some pyrolytic reactions still going on above 550 °C. The different pyrolysis fractions were analyzed by GC–MS; the produced oil was rich in hydrocarbons and alcohols. On the other hand, the gas fraction is mainly composed of CO₂, CO and CH₄. Finally, the carbonaceous solid residue (char) displayed porous features, with a more developed porous structure as the pyrolysis temperature increased.     

Pyrolysis and combustion kinetics of microcapsules containing carbon nanofibers by thermal analysis–mass spectrometry

The thermal properties of microcapsules containing carbon nanofibers (CNFs) suspended in ethyl phenylacetate (EPA) were investigated by thermogravimetric analysis coupled with mass spectrometry (TGA–MS). The pyrolysis of these microcapsules consisted of two stages. During the first one (100–150 °C), the emissions of aromatic compounds coming from the decomposition of EPA were identified. In the second one (150–290 °C), NH₂–CO coming from primary amide decomposition was mainly detected.A multiple-step model was used to predict the thermal decomposition of the synthesized microcapsules under both inert and oxidant atmospheres. Furthermore, pyrolysis and combustion kinetic parameters such as pre-exponential factor and activation energy of these microcapsules were estimated by nonlinear regression. An excellent agreement between experimental and predicted data was observed and confirmed from the statistical point of view.     

Detailed kinetic computations and experiments for the choice of a fuel–oxidiser couple for hybrid propulsion

The choice of a solid reducer for hybrid propulsion is generally based on the quantity of gaseous combustible it can produce (expressed indirectly by the regression rate). For this reason, the studies focus on the use of additives or on the design of grain while the kinetic aspect is rarely of interest despite the chemistry drives the phenomena (chemical induction delay, heat absorption, and chemical composition). One-step mechanisms are first considered in this paper to quantify the effect of operating conditions on high density polyethylene (HDPE), polymethylmethacrylate (PMMA) and hydroxyl termination polybutadiene (HTPB). Then the chemical composition of pyrolysis products is determined for a large range of operating conditions with highly detailed mechanism for HDPE (1014 species and 7541 reactions). The heating rate applied to the reducer is investigated (from 1 K s⁻¹ to 10⁷ K s⁻¹). Ethylene is found to be the major pyrolysis product. The timescale found over 1250 K and 11.11 bar is in agreement with the requirements of hybrid propulsion. The calculated data are compared to experimental ones. Finally, a short combustion study with detailed chemistry (over 700 species and 3000 reactions) is proposed because it impacts directly on the pyrolysis through the generated heat flux. It allows considering the oxidiser decomposition (hydrogen peroxide (H₂O₂) and nitrous oxide (N₂O)). Pure oxygen (O₂) is considered as reference data. The effect of atmosphere (inert or oxidative) on the pyrolysis is shown. The kinetic computations of N₂O combustion give higher flame temperatures than for H₂O₂. Ignition times, below a few milliseconds, are obtained for all the reducers over 1250 K. Finally, the HDPE/H₂O₂ and HTPB/N₂O couples are found to be the most interesting.