TG Curves Research Articles

New insights into the non-isothermal oxidation of tight oil: Experimental study and theoretical prediction

A better understanding of the influence factor investigation and oxidation behavior prediction for the crude oil could supply valuable insights into the reactivity of crude oil and feasibility of air injection process. In this study, non-isothermal oxidation experiments have been conducted via thermal analyses (thermogravimetry/differential scanning calorimetry/pressurized differential scanning calorimetry, TG/DSC/PDSC) with different heating rates (5, 10, and 15 °C/min) and experimental pressures (1, 3, and 5 MPa) in order to investigate the influences on oxidation behaviors, exothermic characteristics, and kinetic parameters of typical tight oil. In addition, the distributed activation energy method (DAEM) was employed to determine accurate kinetic parameters for whole oxidation process and to further predict the oxidation behavior with the reconstruction of TG and conversion curves. The results showed that, heating-rate increment would lead to inadequate oxidation process with more reaction occurrence in a shorter time. Inversely, more rapid heat release, higher exothermic peaks with lower temperature ranges were detected in PDSC curves, indicating high pressure in actual oil reservoir would strengthen the oxidation progress with more heat generation to enhance oil recovery. Then, based on specific activation energy distribution and DAEM, the calculated TG and conversion curves presented a satisfactory fitting relation with experimental data, demonstrating a reasonable prediction of oxidation behavior and kinetic characteristic for the crude oil under specific heating-rate. The understandings in this study not only provided new insights on the verification of obtained kinetic parameters, but also the accurate prediction of crude oil oxidation behavior.

Kinetic parameters of thermal destruction of the copolymer of polyethylene glycol fumarate with acrylic acid in inert medium

Thermal decomposition of the copolymer of polyethylene glycol fumarate with acrylic acid (p-EGF:AA) of two different compositions synthesized earlier was studied in the present work. TG and DTG curves prove that decomposition takes place in several stages. According to thermogravimetric curves it has been found out that for the copolymer with higher content of acrylic acid the decomposition of the copolymer’s sample is started at higher temperatures. It has been shown the shift of the temperature of decomposition’s start to the higher area with the increase of heating rate which is necessary for the detorsion of macromolecular coil. Experimental data processed using graphical methods of Kissinger–Akahira–Sunose and Friedman allowed us to calculate the activation energy of the thermal decomposition process. It has been established that the copolymer with the composition of 21.03:78.97 mass.% has lower meaning of activation energy than the one with the composition of 68.96:31.04 mass.%. As a result of calculation one can see that the meanings found out using these methods depend slightly on conversion. Using Achar-Brindley-Sharp method and the method of invariant kinetic parameters the kinetic triplet of the decomposition process has been found which was used to build the calculated curve. The dependences of g(α) on α using these parameters showed a satisfactory agreement of calculated curves with the experimental ones. One can conclude that the decomposition process of the copolymer of polyethylene glycol fumarate with acrylic acid is well described with of D3 (three-dimensional diffusion) model.

Different Sequential Chemical Treatments Used to Obtain Bleached Cellulose from Orange Bagasse

ABSTRACT The development of efficient pretreatments is widely used in biobased products aiming to add value to the residue. In this study, orange bagasse is investigated for cellulose extraction under moderate chemical sequential extraction conditions. Three pretreatments are evaluated: alkaline treatment, organosolv, and residue insoluble alcohol. Then, all pretreated samples are bleached. The results are analyzed by chemical composition, Fourier transformed infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. In general, similar results are observed for all bleaching samples, independently of the pretreatment. A similar cellulose amount is observed among the samples. When compared only to the pretreatments, alkaline shows to be a more effective way of presenting a higher crystallinity index. Hemicellulose and lignin are mostly removed after pretreatment. FTIR and XRD indicated that the pretreatment seems to be more effective in the first step. TG curves presented a more homogeneous pattern due to cellulose removal showing three steps for pre-treatment and two steps for bleached samples. The obtained cellulose has numerous potential applications, and a suitable route can be selected according to available reagents.

Evaluation of Structural and Optical Properties of Nanocrystalline Cubic Y2O3 Phase Materials via Combustion Method Using Different Fuels

In this work, we have carried out combustion synthesis of nanocrystalline Y2O3 materials using hexamine, polyethylene glycol(200) (PEG(200)), and ethylene glycol (EG) as fuels. In addition, the impact of mechanical stirring of commercial Y2O3 powder with various dilutions of PEG(200) with distilled water as a solvent was also examined. The as-prepared combustion product of the hexamine is significantly different from other fuels (PEG(200) and EG). The annealed combustion products crystallize in the pure cubic Y2O3 phase. The combustion product of PEG(200) reveals a maximum weight loss of ∼46% at 800 °C in the TG curve. The UV–vis-NIR features of different samples show quite interesting results. The Eg values obtained from the Tauc plots are found in the range of 5.48 to 5.71 eV for the different samples. The observed strong FTIR band at 560 ∼ 415 cm−1is owing to the vibrational Y–O bond in the present series samples. The Raman spectra show the highest intensity peak at wavenumber 374 cm−1is owing to the Fg vibrational mode of the Y2O3phase. Agglomerated nature of nanoparticles is seen in the Y2O3 phase samples obtained from EG and hexamine as fuels. The PEG-derived Y2O3 nanomaterials exhibit rather a high reflectance in the NIR region quite comparable to the NIR tendency of the mechanically stirred Y2O3 samples. Thus, the present processed nanocrystalline Y2O3 materials are efficient for solar reflective pigment application in the NIR industry.

"COMPARATIVE ISOCONVERSIONAL THERMAL ANALYSIS AND DEGRADATION KINETICS OF SALVIA SPINOSA (KANOCHA) SEED HYDROGEL AND ITS ACETATES: A POTENTIAL MATRIX FOR SUSTAINED DRUG RELEASE"

The present study deals with the isolation and modification of Salvia spinosa hydrogel (SSH) to investigate its thermal degradation profile. The SSH was modified chemically to its acetylated derivative (ASSH-1–4) with DS 1.05-2.79. After characterization by Fourier transform infrared (FTIR) and solid-state CP/MAS 13C-NMR spectroscopic techniques, both SSH and ASSH-4 were subjected to thermogravimetric analyses (TG) by the isoconversional method, i.e., the Flynn-Waal-Ozawa (FWO) and the Kissinger methods. TG curves showed that both SSH and ASSH-4 exhibited two-step degradation. The energy of activation (Ea) for each degradation step was calculated by fitting thermal degradation data to the FWO method, revealing greater stability of ASSH-4 than that of SSH. Analysis by Kissinger’s method revealed the second and one and a half order of thermal degradation (n) for SSH and ASSH-4, which also evidenced that ASSH-4 is more stable than SSH. The values of the thermodynamic triplet (ΔH, ΔG and ΔS) were calculated from thermal data. Positive values were found for ΔG, which showed the non-spontaneous nature of thermal degradation of SSH and ASSH-4. The values of integral procedural decomposition temperature (IPDT) and intrinsic thermal stability (ITS) for SSH and ASSH-4 were found comparatively greater than those of many other commercially available materials of the same kind, which revealed the higher stability of both materials. SSH, as a benign polysaccharide-based material, was also assessed for its utility in drug release studies, taking caffeine as a model drug. The SSH matrix-based tablet formulation (SSHC) showed a sustained release behavior of the drug in preliminary studies.

Preoperative platelet distribution width-to-platelet ratio combined with serum thyroglobulin may be objective and popularizable indicators in predicting papillary thyroid carcinoma.

ObjectivesThe incidence of papillary thyroid carcinoma (PTC) has increased more rapidly than that of any other cancer type in China. Early indicators with high sensitivity and specificity during diagnosis are required. To date, there has been a paucity of studies investigating the relationship between preoperative platelet distribution width‐to‐platelet count ratio (PPR) and PTC. This study thus aimed to assess the diagnostic value of PPR combined with serum thyroglobulin (Tg) in patients with PTC.MethodsA total of 1001 participants were included in our study. 876 patients who underwent surgery for nodular goiter were divided into the PTC group or benign thyroid nodule (BTN) group according to pathology reports, and 125 healthy controls (HCs) were included. Preoperative hemogram parameters and serum Tg levels were compared among three groups. Receiver operating characteristic (ROC) curve was used to evaluate the value of PPR combined with serum Tg for diagnosing PTC.ResultsPlatelet distribution width (PDW) and PPR levels were higher in the PTC group than in the BTN and HC groups (both p < 0.05) but did not significantly differ between the BTN and HC groups. PDW and PPR levels significantly differed in the presence/absence of lymph node metastasis, the presence/absence of capsule invasion (p = 0.005), and TNM stages (p < 0.001). Multivariable analyses indicated that high serum Tg levels [adjusted odds ratio (OR), 1.007; 95% confidence interval (CI), 1.004–1.009; p < 0.001], high neutrophil‐to‐lymphocyte ratio (NLR,adjusted OR, 1.928; 95% CI, 1.619–2.295; p < 0.001), and high PPR (adjusted OR, 1.378; 95% CI, 1.268–1.497; p < 0.001) were independent risk factors for PTC. In ROC analysis, the areas under the curves (AUCs) of serum Tg, PDW, PPR, and NLR for predicting PTC were 0.603, 0.610, 0.706, and 0.685, respectively. PPR combined with serum Tg (PPR + Tg) had a higher diagnostic value (AUC, 0.738; sensitivity, 60%; specificity, 74.7%) compared with PDW + Tg (AUC, 0.656; sensitivity, 64.4%; specificity, 59.9%) and NLR + Tg (AUC, 0.714; sensitivity, 61.6%; specificity, 71.1%).ConclusionsPreoperative PPR combined with serum Tg may be objective and popularizable indicators for effective predicting PTC.

Investigation of the thermal behavior of Mg(NO3)2·6H2O and its application for the regeneration of HNO3 and MgO

The nitric acid pressure leaching (the NAPL) process has caught people’s attention owing to the increasing demand for nickel and cobalt, and the gradual depletion of nickel sulfide. In this process, iron, aluminum, nickel, and cobalt are separated successively by MgO. Therefore, a large amount of Mg(NO3)2·6H2O is generated, which is an important carrier to achieving the cycling of HNO3 and MgO via pyrolysis. However, the thermal behavior data of Mg(NO3)2·6H2O are insufficient. Hence, related experiments were carried out, which indicated four stages in this process with the absorption energy of 212.85 kJ/mol. Moreover, the hypotheses 3(Mg(NO3)2·nH2O) → Mg3(OH)4(NO3)2 + 4HNO3 (n = 4/3, the coexistence of Mg(NO3)2·2H2O and Mg(NO3)2) determining the most possible route to form Mg3(OH)4(NO3)2 was confirmed. The four–step model (A → B → C → D → E) showed a strong correlation with TG curves and can be described appropriately with the Fn, Fn, An, and An models, respectively. The molecular dynamic simulation revealed that dehydration and decomposition process include melting, dehydration, formation of anhydrous magnesium nitrate, and pyrolysis. Finally, a novel technical route for HNO3 and MgO regeneration was proposed with the natural gas consuming about 8.52 × 10-3 Nm3 per mole of Mg(NO3)2·6H2O.

Hybrid polymer-oxide materials formed by non-stationary electrolysis as catalysts for hydrogen peroxide decomposition

ABSTRACT Hybrid polymer-oxide materials based on transition metal oxides and polyvinylpyrrolidone have been obtained by non-stationary electrolysis on the surface of steel support. The elemental and phase compositions of the developed hybrid polymer-oxide materials have been investigated by XRF and XRD. The main phases are MoO3, MoO2, Mo18O52, Fe2O3, FeMoO4, NiMoO4, and CoMoO4. Using FT-IR spectroscopy, the incorporation of cobalt, nickel, iron, and molybdenum oxides into the structure of the polymer matrix has been proved. The surface morphology and surface height of the obtained hybrid polymer-oxide materials were reconstructed by electron microscopy and optical profilometry. Their thermal behavior was studied by comparing the DSC–TG curves of pure polyvinylpyrrolidone and the obtained hybrid polymer-oxide materials. The study of the catalytic activity in the hydrogen peroxide decomposition model reaction by the gasometric method showed that the developed hybrid polymer-oxide materials have high catalytic activity, and the presence of a polymer matrix leads to an increase in the catalytic activity of oxide phases in comparison with an oxide material of a similar composition in the absence of polymer. The study of the antibacterial activity of the obtained hybrid polymer-oxide materials showed their high efficiency against Staphylococcus aureus and Escherichia coli.

Thermal behaviour of kaolinitic raw materials from San Jos\xe9 (Oruro, Bolivia)

Kaolin is widespread as a result of the alteration in the San José Sn-Ag deposit located in Oruro, Bolivia. This study presents a chemical, mineralogical and thermal characterization of the San José kaolinitic deposit, which is necessary to determine their optimal applications. Mineral phases of these white silty kaolinitic materials were determined by X-ray diffraction (XRD) and are quartz, kaolinite, K-feldspar, muscovite, illite and minor halloysite, dickite, plagioclase, jarosite, rutile, alunite and gypsum. The fraction < 63 µm contains 20–27 mass% of kaolinite. Differential thermal analysis (DTA) shows an endothermic peak at 520 °C associated with the dehydroxylation of kaolinite and an exothermic peak at ~ 980 °C related to the crystallization of mullite. TG curves show a total mass loss up to 1300 °C of about 8 mass%. The dilatometric curves show a shrinkage at about 890 °C produced by the collapse of metakaolinite into a spinel-like structure, and another shrinkage starts at 1010 °C, at the beginning of the sintering, when the spinel-like phase is transformed to mullite and amorphous SiO2. Lightness L* is 80–92, but only the mined materials have b* < 4, suitable for paper filling applications.

Synthesis of macromolecular brush and its thermal degradation studies

The di-1,2-propanediol ester of fumaric acid (Diol) is synthesized and polymerized to yield the macromolecular brush (PDiol). The structure of monomers and their polymer is confirmed by Fourier transform infrared spectroscopy (FTIR) studies. The PDiol material shows the number average molecular weight (Mn ) as 951 g/mol, weight average molecular weight (Mw ) as 4,378 g/mol, and a polydispersity index (PDI) of 4.6. The hydroxyl value for PDiol is 471 (mg KOH/g). The thermal degradation property of the brush is investigated using thermogravimetric analysis (TGA). The cyclic intra and inter loops are formed while annealing at a temperature of around 200 °C. Using the TG curves recorded at different heating rates and by applying advanced isoconversional methods by model-free kinetics, the apparent activation energy for the thermal degradation (Ea-D) at different reaction extents (α) are calculated and discussed. Advanced methods are also used to refine the apparent activation energy data. The Ea-D values for PDiol range from 100 to 155 kJ/mol. For a lifetime of 20,000 h, the 20% degraded PDiol can withstand a temperature of 39 °C.

A novel coal gangue thermal stabilizer and its effect on thermal stability and mechanical properties of poly(vinyl chloride)

AbstractNontoxic and efficient coal gangue thermal stabilizer (Y‐CG) was prepared by cheap and readily available calcium oxide, coal gangue (CG) and stearic acid(SA). The proposed mechanism of Y‐CG thermal stability was studied by XRD, FT‐IR, BET and thermal stability test. The results show that when the mass ratio of CG to water was 1:7, the loading of Ca(OH)2 between CG sheets reached the maximum value of 3.01 mmol/g. The hydrophobic property of the Y‐CG surface was better when modified at 75°C for 2 h with 5% SA. With 10% Y‐CG, the Congo red test showed thermal stabilization time of PVC improved up to 55.9 min and the torque rheological test showed dynamic thermal stabilization time of PVC improved up to 62.10 min. The TG curves show that Y‐CG had little effect on the onset degradation temperature of PVC. Still, Y‐CG can absorb HCl and initiate the carbonization of PVC to inhibit degradation. Compared with the commonly used thermal stabilizers, the thermal stability of Y‐CG was only slightly worse than that of hydrotalcite thermal stabilizers. The early reaction was that the strong base Ca(OH)2 in Y‐CG adsorbs HCl, and the CaCl2 was stably loaded in the CG layered structure, which avoided the adverse effects caused by strongly alkaline. The late reaction was that SA and Ca(OH)2 form weakly alkaline calcium stearate to absorb HCl. At the same time, calcium stearate can also be used as a compatibilizer to improve the compatibility between Y‐CG and PVC.

Comparative analysis of the energy content of diverse fuels performed via thermogravimetric investigations

Thermogravimetry is a well-known analysing technique in which the mass of a substance is monitored as a function of temperature variation by time, and as a sample specimen being subjected to a scheduled temperature program, in a controlled atmosphere. The method is based on measuring sensors for the mass loss, in the controlled-atmosphere furnace, and on a temperature programmer, all interfaced to a computer. It is also known as thermogravimetric analysis (TG) or derived thermogravimetric analysis (DTG). Kinetic parameters, stability, and changes in the composition are among the most important results obtained upon performing such analysis. The article focuses on three different analyses run upon three different fuels: a fossil one (coal), a classic biomass (renewable fuel), and waste poultry manure. The conclusion indicates that all three fuels illustrate important energy content, showing specific points in the TG and DTG curves, which are analysed in detail. The similarities and differences are also pointed out. Additionally, the techniques used are described, considering their implication for complex waste biomasses, which might be subject of biogas production. The technique is recommended in addition to classic thermal analysis and heating value determination.

Crystal structure, IR, TG, and magnetic properties of a thiabendazole aqua-cobalt(II) 4,4'-stilbenedicarboxylate

A new coordination polymer, [Co(SDA)(TBZH)(H2O)]n (1, SDA = trans-4,4'-stilbenedicarboxylic acid tetra-anion, TBZH = thiabendazole) has been synthesized under hydrothermal condition. The structure has been determined by X-ray diffraction, thermal gravimetric analysis (TG), infrared spectrum (IR) and Magnetic properties. The structure of 1 contains one Co(II), the metal center Co(II) is five-coordinated and through the SDA, it bridged an infinite one-dimension chain. In TG curve, there are three weight loss steps and the residual may be CoO. The static and dynamic magnetic properties of the high-spin Co(II) polymer 1 were measured, there is no SCM properties exhibited by the polymer.

Characteristics and adsorption of Cr(VI) of biochar pyrolyzed from landfill leachate sludge

Landfill leachate sludge (LLS), originated from the infiltration of rainwater through dumping sites of waste and water contained in landfills, is a specific type of sewage. Since its large amount, environmental unfriendliness and compositional instability, the sustainable management and disposal of LLS requires urgent attention. In this study, LLS disposal problem was addressed along with the removal of chromium (Cr) from water. Firstly, the thermal behaviors of LLS were investigated through TG analysis. Secondly, LLS-based biochar (SC) was prepared in a tubular furnace, and the effect of pyrolysis temperature on the yield and properties of SC was investigated. Finally, using SC900 as Cr(VI) adsorbent, the influence of various factors on Cr(VI) adsorption were investigated. BET, FTIR, and XPS analyses were performed to determine the characteristics of SC and the variation of SC before and after adsorption. Results showed that, TG curve of LLS exhibited a rapid mass loss of 54.15% between 220 and 525 °C due to the cleavage of C-O and C-C bonds with the release of large amounts of CO2. The SC yields were in the range of 10.81–22.16% when the pyrolysis temperature ranged from 400° to 900°C. The optimal pyrolysis temperature for the preparation of the SCs was determined to be 900 °C, and SC900 had a relatively high BET surface area of 83.87 m2/g. exhibited the highest Cr(VI) adsorption of 17.46 mg/g. The main oxygen-containing functional groups (-OH, C-O, CO) present in the SC played an important role to adsorbed Cr(VI) and reduced it to Cr(III) at a low pH. As a result, 76.5–85.3% of the adsorbed Cr(VI) was reduced to the less toxic Cr(III). Moreover, only 0.52% (1.56 ppm) of the adsorbed Cr (from a 300 ppm solution) leached from SC900, which indicated the high stability of the adsorbed Cr in the SC.

\\Preparation of poly(styrene-co-acrylic acid)-zinc oxide composites: Experimental and theoretical investigation of gamma radiation shielding properties

This study, it is aimed to prepare a polymer composite between styrene, acrylic acid, and ZnO and to measure the radiation shielding of the synthesized polymer composite. Firstly poly(styrene-co-acrylic acid) (P(S-co-AA)) copolymer was synthesized using the emulsion polymerization method between styrene and acrylic acid. Then, P(S-co-AA)-ZnO composites were prepared with different percentages of ZnO. For preparing these composites, the materials were mixed in a 60 °C ultrasonic bath. P(S-co-AA)-ZnO was poured into Petri dishes to form a film. When the TG curves were examined, it was not found a significant difference between the copolymer composite and the copolymer. The molecular weight of the copolymer was found to be 120000. SEM images show zinc fragments located between the polymer chains. The potential for radiation capture against gamma was determined using a NaI scintillation detector. The linear gamma attenuation coefficients for P(S-co-AA)-ZnO samples were calculated to Lambert's Beer Law and measured for 662 keV. Theoretical gamma attenuation coefficient values were calculated by multiplying the density of the composite with the mass attenuation coefficients. The absorption parameters of polymer composites are directly proportional to the increasing amount of zinc oxide. P(S-co-AA)-ZnO-15% was the best absorber at 662 keV energy compared to other polymer composites.

Structural stability of biofilms produced from silkworm cocoon fibers

Biofilms were obtained from cocoons of the silkworm, Bombyx mori, involving the removal of sericin, extraction and solubilization of fibroin fibers, dialysis of fibroin dispersions and preparation of biofilms by the casting process. Biofilm transparency was verified by UV?Vis spectroscopy and thermal stability by thermogravimetric/differential scanning calorimetry (TG/DSC). Soon after preparation, the solidification of the fibroin solution prepared from the cocoons and extracted by the Ajisawa method was monitored until the biofilm stabilized, using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) as a function of time. The results showed that there was a change in the conformation from the silk I structure (?-helix) to silk II (?-sheet). In order to improve the characterization of the biofilms obtained by the Ajisawa method and LiBr solubilization of fibroin fibers, Raman spectroscopy was used to verify the stabilization of the different possible molecular conformations for the fibers in these materials, by comparison with the cocoon spectra and those of the solid (freeze-dried precipitated by dialysis for 72 h. By comparing the Raman spectra of the biofilms in terms of the intensities of the broadened band characteristic of amide I, it was possible to assess the conformational changes in both materials based on the possible transitions between ?-sheet conformations and flexible ?-helix and ?-turn structures. The results showed a dispersion of these conformations in the biofilms generated and in the solid freeze-dried hydrogel spectrum, and the ?-sheet conformation was found to be predominant. The TG and DSC curves showed that the materials with higher ?-sheet content exhibited higher thermal stability. Thus, the data obtained further elucidated the properties of these materials that are widely used in various processes.

Catalytic pyrolysis of coconut oil with Ni/SBA-15 for the production of bio jet fuel.

Catalytic pyrolysis of vegetable oil is one of the potential routes to convert oil to drop-in biofuels, known as renewable hydrocarbons. In this paper, we explored catalytic pyrolysis of coconut oil using SBA-15 impregnated with Ni in proportions of 1% to 5% to produce sustainable aviation fuel. The catalysts were synthesized, calcined and then characterized by XRD, FTIR, SEM, and EDS. In order to better understand the behavior of this process, thermal and kinetic studies were carried out by thermogravimetry. The TG curves of vegetable oil with (10%) and without catalysts were obtained at heating rates of 5, 15 and 20 °C min−1, in the temperature range between 30 and 600 °C. The kinetic parameters were calculated by the Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS) methods. In the kinetic study, lower heat rates promoted higher conversions and the KAS model suits the process. The results calculated for the OC sample using the two kinetic models showed an increase in the Ea energy as the conversion progressed to a certain point. Catalytic pyrolysis experiments were performed in a one-stage tubular reactor at 500 °C with a catalyst loading of 10 wt% on the basis of mass of oil. The catalyst with 5% Ni showed greater presence of hydrocarbons and greater formation of water, indicating that the deoxygenation process occurred through decarbonylation. With this, the present study was successful in the development of methodologies for obtaining hydrocarbons with a composition close to that of drop-in fuels, compared to the process carried out with vegetable oil in the absence of catalysts.

Application of model-free and multivariate nonlinear regression methods for evaluation of the kinetic scheme and kinetic parameters of thermal decomposition of low density polyethylene

A sort of low density polyethylene (LDPE) was characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), thermal analysis methods (TG, DTG, DTA) in nitrogen flow at constant heating rates of 2.50, 5.00, 9.91, 14.98 and 19.92 K min−1 and at other five temperature programs, coupled TG + FTIR analysis, and DSC analysis in nitrogen flow. The kinetic analysis of TG data has been performed using an algorithm consisting of the following three successive steps: (1) the application of model-free (isoconversional) methods for evaluation of apparent activation energy dependence on the conversion degree, (2) the processing of the TG data recorded at constant heating rates to assess the possible kinetic schemes and the corresponding kinetic parameters, and (3) the selection of the kinetic scheme characteristic of the thermal decomposition of LDPE by comparing the experimental TG curves with the reconstructed ones corresponding to the temperature programs used. It has been pointed out that the overall process of thermal decomposition of LDPE consists of four successive stages with the Avrami-Erofeev kinetic models (An) - reaction order (Fn) -reaction order (Fn) - three-dimensional diffusion (D3). This kinetic scheme and corresponding kinetic parameters is suitable for prediction of thermal behavior of LDPE in some temperature programs and can be used for the design of pyrolysis reactors necessary for the conversion of LDPE waste into low molecular mass chemicals, which can be used as raw materials for chemical and petrochemical industry.

Kinetic Analysis for the Catalytic Pyrolysis of Polypropylene over Low Cost Mineral Catalysts

A kinetic analysis of non-catalytic pyrolysis (NCP) and catalytic pyrolysis (CP) of polypropylene (PP) with different catalysts was performed using thermogravimetric analysis (TGA) and kinetic models. Three kinds of low-cost natural catalysts were used to maximize the cost-effectiveness of the process: natural zeolite (NZ), bentonite, olivine, and a mesoporous catalyst, Al-MCM-41. The decomposition temperature of PP and apparent activation energy (Ea) were obtained from the TGA results at multiple heating rates, and a model-free kinetic analysis was performed using the Flynn–Wall–Ozawa model. TGA indicated that the maximum decomposition temperature (Tmax) of the PP was shifted from 464 °C to 347 °C with Al-MCM-41 and 348 °C with bentonite, largely due to their strong acidity and large pore size. Although olivine had a large pore size, the Tmax of PP was only shifted to 456 °C, because of its low acidity. The differential TG (DTG) curve of PP over NZ revealed a two-step mechanism. The Tmax of the first peak on the DTG curve of PP with NZ was 376 °C due to the high acidity of NZ. On the other hand, that of the second peak was higher (474 °C) than the non-catalytic reaction. The Ea values at each conversion were also decreased when using the catalysts, except olivine. At &lt;0.5 conversion, the Ea obtained from the CP of PP with NZ was lower than that with the other catalysts: Al-MCM-41, bentonite, and olivine, in that order. The Ea for the CP of PP with NZ increased more rapidly, to 193 kJ/mol at 0.9 conversion, than the other catalysts.

Autocatalytic influence of different levels of arsine on the thermal stability and pyrolysis of polypropylene

In this article, the pyrolysis and thermo-degradation of 11 virgin-polypropylene (virgin-PP) with different levels of arsenic in its polymer matrix, was carried out in a discontinuous quartz reactor at 500 °C. To quantify arsine (AsH3), 4 points were sampled during the PP synthesis process and a methodology was applied by GC with 4 detectors, which simultaneously and with a single injection allowed to quantify multiple components. AsH3 in propylene varied between 0.05 and 4.73 ppm and arsenic in virgin-PP residues between 0.001 and 4.32 ppm for PP0 and PP10. These generated an increase in the melt flow index from 3.0 to 24.51 and maintained a direct relationship with an R2 of 0.9993. The origin of thermo-oxidative degradation and the beginnings of virgin-PP pyrolysis are explained by the formation to aldehyde, ketone, alcohol, carboxylic acid functional groups, CO and CO2. These species caused TG and DTG curves to have atypical behavior for PP. For example, PP10 with an arsenic content of 4.32 ppm presented 3 degradation peaks at 80, 90 and 200 °C with a mass loss ratio of 22%, 18% and 55% °C−1 respectively. During pyrolysis the highest percentage of alkanes was found in PP0 with an average value of 62.4%, and the lowest values were found in PP8 to PP10, with oscillations between 0% and 1.4%. The total concentration of oxidized species for PP0 to PP10 was 2.26%, 32.7%, 43.1%, 50.9%, 59.3%, 66.2%, 75.0%, 83.0%, 89.1% and 97.5% respectively. In an O2 atmosphere ketones and carboxylic acids were only identified in PP0 to PP5. CO2 concentrations in PP5 to PP10 were of 100%.