Thermal Degradation Process Research Articles

Investigation on prospective bioenergy from pyrolysis of macadamia nut shell waste using multicomponent Fraser-Suzuki kinetic model, kinetic triplet and thermodynamic parameters

The investigation of macadamia nut shell waste (MNSW) was conducted to elucidate its bioenergy potential through the analysis of physicochemical properties, kinetic triplet, reaction mechanism models, and thermodynamic parameters. The thermal degradation experiments were carried out using a thermogravimetric analyzer under nitrogen atmosphere at four different heating rates. The multicomponent Fraser-Suzuki kinetic model revealed that the primary decomposition stage could be successfully divided as the parallel devolatilization process of two, three, or four pseudo components. The thermal degradation process of MNSW can be divided into pseudo hemicellulose (PE-H), hemicellulose-lignin (PE-HL), hemicellulose-cellulose (PE-HC), cellulose (PE-C), and lignin (PE-L) employing the multicomponent Fraser-Suzuki kinetic model. The apparent activation energy (E) was calculated using Friedman, Ozawa-Flynn-Wall, Starink, and Kissinger-Akahira-Sunose four model-free methods. The average apparent activation energy calculated through the Starink model-free method was found to be 190.13 and 174.18 kJ/mol for PE-HL and PE-C, 143.79, 169.99, and 249.88 kJ/mol for PE-H, PE-C and PE-L, and 142.98, 157.15, 169.84, and 244.62 kJ/mol for PE-H, PE-HC, PE-C and PE-L, respectively. Evaluation of thermodynamic parameters showed that the pyrolysis process of each pseudo component was an endothermic non-spontaneous reaction independent of surface area and required additional heat and energy input. The pyrolysis process of all pseudo components was accurately characterized using order-based, nucleation, geometrical contraction, power law, and diffusional reaction mechanism models using master plots method. This work provides a theoretical basis for MNSW or other biomass wastes as attractive and environmentally friendly alternatives for bioenergy production, offering crucial insights for reactor design and improving conversion efficiency.

Pyrolysis of macadamia nut peel using multicomponent Gaussian kinetic modeling and ANN analysis

The physicochemical properties of macadamia nut peel (MNP) were explored based on pyrolysis characteristics, kinetics, thermodynamic parameters, reaction mechanism, and artificial neural network (ANN) application to evaluate its suitability and potential for pyrolytic conversion into bioenergy products. Pyrolysis experiments of MNP were performed using a thermogravimetric analyzer in a nitrogen atmosphere. The thermal degradation process of MNP can be successfully modeled into pseudo hemicellulose (PS–H1), cellulose (PS–C2), and lignin (PS-L3) using a multicomponent Gaussian kinetic model with high correlation coefficient (R2 > 0.99). The average apparent activation energy was 179.28 kJ/mol for PS-H1, 192.31 kJ/mol for PS-C2, and 129.42 kJ/mol for PS-L3 using Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Starink, and Tang four model-free methods. Master plots method was used to determine the reaction mechanism models of three pseudo components, and the pyrolysis progress can be described well using order-based and nucleation mechanism models. The thermal degradation behaviors of MNP were predicted using artificial neural network, and the best artificial neural network prediction model was ANN (3*15*1). Based on the physicochemical properties, pyrolysis characteristics, kinetics, thermodynamic parameters, reaction mechanism and ANN prediction model, MNP is suitable for pyrolytic conversion into bioenergy products.

Pyrolytic characteristics of abutilon stalk waste using TG-FTIR, Py-GC/MS, and artificial neural networks: Kinetics, thermodynamics, and gaseous products distribution

The physicochemical properties of abutilon stalk (ABUS) were investigated to assess its suitability for pyrolytic conversion into bioenergy and bio-based chemicals based on kinetic triplet state, thermodynamic parameters, decomposition mechanisms and product distributions. The pyrolysis behavior of ABUS was studied using a thermogravimetric analyzer at five heating rates in a nitrogen atmosphere. The Gaussian deconvolution function indicated that the pyrolysis process of ABUS can be successfully modeled as four parallel devolatilization events (R2 > 0.99), divided into the devolatilization of pseudo drying (PO-D), hemicellulose (PO-H), cellulose (PO-C), and lignin (PO-L), respectively. The average apparent activation energies were 34.89 kJ/mol for PO-D, 163.02 kJ/mol for PO-H, 169.55 kJ/mol for PO-C, and 107.51 kJ/mol for PO-L using four model-free methods (Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Starink, and Tang). The pyrolysis process was accurately predicted using diffusional, power law, geometrical contraction, and order-based reaction mechanism models. Thermal degradation process for each devolatilization event was successfully reconstructed using combined kinetics (R2 > 0.96), providing a useful theoretical basis and mathematical model for predicting the pyrolysis behavior of ABUS. The volatile products produced by ABUS pyrolysis were characterized using an integrated TGA-FTIR and Py-GC/MS system, confirming the proportion of high-energy compounds (benzenes, phenols, ketones, alcohols, aldehydes, acids, esters, hydrocarbons and their derivatives, N-heterocyclic substances, and N-containing compounds) and gas emission levels (CO > CH4 > C-O > H2O > CO2 > CO > C-O(H) > HCN > NH3 > SO2). Artificial neural network (ANN) was used to predict the pyrolysis behaviors of ABUS, and the best ANN model was ANN (5 *11 *1) with high R2 of 0.99998. Based on the kinetics, thermodynamics, and gaseous products distribution, ABUS has great application potential as raw material for bioenergy production.

Conductive nano-Al/polyaniline composites prepared via mechanical milling

The conductive nano-Al/polyaniline composites were prepared by the milling method in the solid state. Here, aluminum nanostructures were prepared in two different mechanical methods, wire drawing and wire milling in the presence of lubricant oil. The effects of the preparation methods on the structures and morphologies of aluminum nanostructures were investigated by XRD and FESEM. The results show that the shape and size of aluminum nanoparticles in the preparation by the wire drawing method are significantly different than the wire milling method. The aluminum nanostructures were prepared by milling method have flake-like nanosheets while the wire drawing method leads to the formation of spherical ultrafine nanoparticles, which particles size are in the range of 30–60 nm. Then, polyaniline was produced using a solid-state polymerization process by the chemical reaction between aniline hydrochloride and potassium peroxydisulfate. Finally, nano-Al/polyaniline composites were prepared by mechanical milling at room temperature. The quantitative analysis was carried out with the materials analysis using diffraction (MAUD) method and weight fraction for aluminum and PANI were calculated 6.66% and 93.34%, respectively. Electrical conductivity measurements show the conductivity (1.2 × 10−2 S cm−1 at 25 °C) for polyaniline emeraldine salt and (1.02 × 10−3 S cm−1 at 25 °C) in nanocomposite respectively. The results show that by adding aluminum nanoparticles to the polymer the conductivity of nanocomposite (Al/PANI-ES) is lower than that for pure (PANI-ES). Thermogravimetry and differential thermal analysis curves show pure (PANI-ES) and nanocomposite (Al/PANI-ES) have a similar thermal degradation process. The total weight loss in TG curve of pure PANI-ES, in the temperature range 45–800 °C is 46.28% but, total weight loss observed in nanocomposite is 38.67%. Therefore, nanocomposite has higher thermal stability than that of the pure PANI-ES.

Facile preparation of ladder aluminosilsesquioxanes with high flame retardancy for polycarbonate

A ladder aluminosilsesquioxanes (Al-L-PPSQ) was synthesized using AlCl3 as an auxiliary catalyst. The chemical structure of Al-L-PPSQ was confirmed by FTIR, 1H, 13C, 29Si-NMR, and MALDI-TOF MS. The well characterized Al-L-PPSQ was used for flame retardant polycarbonate (PC), and the PC/Al-L-PPSQ composite with 6 wt.% Al-L-PPSQ reached UL-94 V-0 rating (1.6 mm), with an oxygen index of 36.6 % and a decrease of 61.2 % in p-HRR. The smoke release of composite materials has also decreased. By analyzing the condensed and gaseous products during the thermal degradation process of PC/Al-L-PPSQ composite materials, it is demonstrated that Al-L-PPSQ can promote the early decomposition of PC into carbon and quickly form a stable and dense char layer to protect the internal substrate during combustion, thereby improving the flame retardancy of PC.

Carbothermic Reduction of Copper Slag in the Presence of Borax

ABSTRACT The low temperature carbothermic reduction of copper slag with charcoal in the presence of borax followed by leaching with H2SO4 was investigated in this study. The copper slag sample was characterized using the XRD. Thermogravimetry was used to study the thermal degradation processes of copper slag. The standard Gibbs free energy at each reaction temperature was calculated using the HSC Chemistry® software. In the reduction experiments, the effects of charcoal and borax, as well as the reduction temperature and time, were investigated in order to identify the mechanism of enhanced reduction. The degree of metal dissolution was investigated in the leaching experiments in relation to leaching time and acid concentration. According to the results of the mineralogical analysis, the primary phases in the copper slag were fayalite, and magnetite. The HSC Chemistry results on equilibrium phase composition show that the carbothermic reduction of magnetite at various temperatures proceeded stepwise as Fe3O4 → FeO → Fe. Meanwhile, fayalite was first catalyzed at low temperature of 300°C before being reduced to metallic phase at 545oC. Thermochemical calculations, phase characterization and experimental results demonstrate that using borax in carbothermic reduction can accelerate phase transformation, lower the temperature of fayalite reduction, and improve the extraction of Co, Cu, and Fe at 850°C.

Polypropylene nanocomposites produced by in‐situ grafting of maleic anhydride using different mixing procedures

AbstractNanocomposites (NC) of polypropylene (PP) and organophilic montmorillonite (oMt) are produced by reactive mixing with simultaneous grafting of maleic anhydride (MA) onto PP using organic peroxide as initiator. Five different strategies of incorporating reactants and clay into a laboratory mixer are used. The structure of composites is examined by FT‐IR spectroscopy, x‐ray diffraction and scanning electron microscopy. Rotational rheometry, thermogravimetry and oxygen permeability are used to evaluate properties. The preparation method has a remarkable influence on NC's structure. Simultaneous addition of peroxide and MA to molten PP followed by incorporation of clay 20 minutes later produces the best degree of clay exfoliation/disaggregation. The NCs obtained using this procedure are highly transparent and have very thin tactoids with interlayer spacing more than 50% larger than the original oMt. The incorporation of just 2 wt% of clay gives place to more than 30% reduction in PP oxygen permeability. Additionally, the temperature at the maximum thermal degradation rate in nitrogen reduces in about 60°C while the temperature at which the thermal degradation process begins is not affected.Highlights Highly intercalated/exfoliated PP/oMt nanocomposites are synthesized Reactive mixing procedure affects the quality of nanocomposite's structure A initial period of grafting before clay addition is the most effective method Highly transparent materials with small tactoids of d001>4 nm is generated PP oxygen permeability is highly reduced by the use of just 2 wt% of nanoclay

Thermal degradation of 3D printing processed polylactide samples by means of vibrational spectroscopy

In the present study, we utilized the fused deposition modeling technique (FDM) to prepare polylactide (PLA) samples and evaluate in real time their thermal degradation by means of vibrational spectroscopy. The FDM method is probably the most popular technology among 3D printing technologies due to the inexpensive and flexible extrusion systems used for the handling of several thermoplastic materials. Nevertheless, a thermal degradation phenomenon of the 3D-printed thermoplastic PLA samples occurs, which is an inevitable issue for long-term reliability of the material leading to poor product properties. We recorded the Fourier transform infrared spectra in real-time mode to monitor the thermal degradation kinetics of PLA samples at a specific temperature below the glass transition point and explore the induced structural alterations. The absorbance of specific spectral features was used to evaluate the concentration reduction of PLA functional groups during the thermal degradation process. The kinetics of the thermal degradation was estimated by means of the absorbance of the C-COO band which reflects the scission of the ester linkage due to degradation process. The kinetic rate constant was found Kt = 2.30 × 10−3 s−1. The results reported in this work were analyzed and discussed in view of relevant data reported for PLA samples prepared with traditional mechanical processing.

Effect of electrothermopolarization on thermal properties of compositions based on polypropylene and MnO2

Information about the internal structure can also be obtained by studying the thermal properties of composites with low molecular weight additives in the low and high temperature range.In this work, by studying the thermophysical properties of PP-based MnO2 composites after exposure to an electric field, we will look at how the additive changes the properties and determine the processes of thermal degradation after aging. Differential thermal analysis (DTA) or thermospectroscopy method is based on measuring the thermal effect when heating or cooling the test substance depending on the temperature. This method makes it possible to quantify the temperature of various transitions with high accuracy. Also that polymer and polymer composite aging relate to the high local anisotropy of force field due to sharp difference of intramolecular and intermolecular interaction forces. By derivatographic method polypropylene films (PP) exposed to electrothermoplarization filled by MnO2 to the extent of 0.5 and 1vol.% have been investigated. By electrothermoplarization E=7×106V/m as a result of aging PP matrix crystals part amorphism is taken place and thermal stability. It is established that electric intensity leads as to the complete amorphism of PP+0.5vol.%MnO2 composition so the complete depolymerization followed by volatilization of formed intermediate products to the extent of 100%.

Flammability and combustion behavior of the polyester/cotton blended fabric via an independent flame-retardation for two components strategy

Polyester/cotton (Terylene/cotton, T/C) blended fabrics are universally applied in clothing and household textiles due to the combination of excellent moisture absorption properties from cotton and dimensional stability from polyester, but high flammability and combustion resulting from the “scaffolding effect” become a major obstacle. Herein, we developed a novel flame-retarding T/C blended fabric to inhibit the “scaffolding effect” via independent flame-retardation for two components strategy, in which the copolymerized flame retardant of the polyester fibers and the cotton fibers were blended, and then halogen-free ammonium vinyl phosphonate (AMVP) was grafted onto the cotton component. The flammability and combustion behavior of the flame-retarding T/C blended fabric were assessed, and the mechanism of the flame retardant was analyzed. The results indicated that the limiting oxygen index (LOI) of the treated blended fabric could be increased to 37.2 %, which had excellent self-extinguishing property. The peak heat release rate (PHRR) and total heat release (THR) values of treated blended fabrics were severally reduced by 54.3 % and 66.5 % in comparison with the blended fabrics without grafted of AMVP. Furthermore, the combustible products of blended fabric generated during the thermal degradation process were effectively decreased in the gas phase due to the independent flame retardant char-formation of two components inhibited the “scaffolding effect”. This study offers a new flame retardant strategy for the fabrication of blended fabrics.

Resolving 3D microstructure evolution of ceramifiable composites at elevated temperatures using in-situ X-ray computed tomography

Ceramifiable polymer composites suffers significant microstructure change during the polymer-to-ceramic conversion as the environmental temperature increases. The present study employs in-situ X-ray computed tomography (XCT) to reveal the microstructure evolution of high-silica/boron-phenolic composites modified with B4C and talc (B4C-talc_HSF/BPR) in three dimensions as the composites is heated to 1000 °C. The cracks are classified based on their locations, and the temporal sequence of their formation is identified. The evolution of internal pore distribution is reconstructed and analyzed quantitatively. Furthermore, the 3D deformation fields of composites during in-situ heating were calculated using digital volume correlation. It is found that the equivalent strain along the thickness direction shows a multi-stage behavior corresponding to the thermal degradation and ceramization transformation processes. The findings provide a 3D visualization of crack propagation and deformation during the polymer-to-ceramic conversion process, which can provide a foundation for further developments in material design.

Fabrication of electrospun nanofiber from a blend of PVC and PHB

Abstract In this work, the fabrication process of electrospun nanofibers from a blend of polyhydroxy butyrate (PHB) and polyvinyl chloride (PVC) has been investigated. PVC/PHB nanofibers have been fabricated from solutions using different PVC and PHB ratios. The influence of technical parameters of the electrospinning process on the fabrication, morphology, and diameter of nanofibers has been evaluated. The chemical structure and thermal properties of PVC/PHB have been studied. The results show that the diameter of PVC/PHB nanofibers increases as the PHB content increases. In addition, the optimal technical parameters of the electrospinning process for each PVC and PHB ratio are different. Infrared spectroscopy analysis revealed an enhancement of the crystalline phase of the polymer composite with increasing PHB content. The thermal properties of PVC/PHB nanofibers were evaluated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The change in PHB ratios leads to a change in the glass transition temperature of PVC/PHB nanofibers. The thermal degradation process of PVC/PHB includes two steps. Increasing the PHB content leads to an enhancement in the mechanical strength of PVC/PHB nanofiber mats; however, it also results in a reduction in tensile elongation. Based on the results of structural, morphological, interaction analysis, and mechanical properties of PVC/PHB nanofibers, this study contributes to the optimization of the fabrication of nanofibers from PVC and PHB. PVC/PHB nanofibers have the potential to be used for air filtration applications.

Prediction of entire thermal degradation process of polymethyl methacrylate infiltrated with kerosene by a modified artificial neural network

AbstractPredicting the entire thermal degradation process of solid combustibles infiltrated with flammable liquids is a challenge at present. In the current study, a novel artificial neural network (ANN) framework containing data preprocessing, data normalization and data transformation is proposed to predict the entire thermal degradation process of polymethyl methacrylate infiltrated with kerosene at three scenarios: (1) fixed kerosene mass fraction with various heating rates, (2) fixed heating rate with various kerosene mass fractions, and (3) various kerosene mass fractions with various heating rates. The entire thermal degradation process of scenario (1) can be accurately predicted using the ANN with 2‐4‐2‐1 topology. Using the data transformation formula exp(x1(1 + x2) to generate a new input variable based on temperature and kerosene mass fraction, a new ANN with 3‐4‐2‐1 topology can accurately predict the entire thermal degradation process of scenario (2). Two new input variables are generated using the data transformation formula 1/(1 + log((1 + x1)(1 + x2))) based on two data sets: (1) kerosene mass fraction and temperature, and (2) heating rate and temperature. The new ANN with 5‐4‐2‐1 topology can accurately predict the entire thermal degradation process at all three scenarios. The new ANN with Levenberg–Marquardt training function and Tanh activation function possesses the best prediction performance.Highlights Data preprocessing can significantly improve the prediction accuracy of ANN. ANN with a suitable hidden layer structure has high prediction accuracy. The new ANN can predict the entire pyrolysis process in various scenarios. ANN with LM and Tanh has the highest prediction accuracy.

Co-production of pigment and high value-added bacterial nanocellulose from Suaeda salsa biomass with improved efficiency of enzymatic saccharification and fermentation

This study evaluated the co-production of pigment and bacterial nanocellulose (BNC) from S. salsa biomass. The extraction of the beet red pigment reduced the salts and flavonoids contents by 82.7%–100%, promoting the efficiencies of enzymatic saccharification of the biomass and the fermentation of BNC from the hydrolysate. SEM analysis revealed that the extraction process disrupted the lignocellulosic fiber structure, and the chemical analysis revealed the lessened cellulase inhibitors, consequently facilitating enzymatic saccharification for 10.4 times. BNC producing strains were found to be hyper-sensitive to NaCl stress, produced up to 400.4% more BNC from the hydrolysate after the extraction. The fermentation results of BNC indicated that the LDU-A strain yielded 2.116 g/L and 0.539 g/L in ES-M and NES-M, respectively. In comparison to the control, the yield in ES-M increased by approximately 20.0%, while the enhancement in NES-M was more significant, reaching 292.6%. After conducting a comprehensive characterization of BNC derived from S. salsa through Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA), the average fiber diameter distribution of these four BNC materials ranges from 22.23 to 33.03 nanometers, with a crystallinity range of 77%–90%. Additionally, they exhibit a consistent trend during the thermal degradation process, further emphasizing their stability in high-temperature environments and similar thermal properties. Our study found an efficient co-production approach of pigment and BNC from S. salsa biomass. Pigment extraction made biomass more physically and chemically digestible to cellulase, and significantly improved BNC productivity and quality.

Kinetic modeling of thermal degradation of TDI/MDI-based flexible polyurethane foam under nitrogen and air atmospheres with Shuffled Complex Evolution algorithm: Insights from TG-FTIR analysis

This study investigates the thermal degradation mechanisms and kinetics of TDI/MDI-based flexible polyurethane foam (FPUF) under nitrogen and air atmospheres, employing thermogravimetric (TG) analysis in conjunction with TG-FTIR technique. The information gleaned from these analysis is used to construct kinetic model based on model-free approaches coupled with the Shuffled Complex Evolution optimization algorithm. The results uncovered the five-step complex thermal degradation process of TDI/MDI-based FPUF compared to TDI-based or MDI-based polyurethane in both atmospheres. In nitrogen atmosphere, this involve the dissociation of TDI- and MDI-based urethane bonds, breakage of recombined urea bonds, random chain scission of polyol, and further degradation of incompletely pyrolyzed solid products. In air atmosphere, the process emcompasses dissociation of TDI- and MDI-based urethane linkages, accelerated oxidation of polyol chains, consumption of urea groups, and combustion of partially oxidized intermediates. This work also emphasizes the limitations of solely relying on TG tests for kinetic modeling, necessitating the integration of TG tests and TG-FTIR technique to obtain a comprehensive understanding of degradation mechanisms. The significance of the acquired insights lies in their potential to reshape the design of thermo-chemical reactors, resulting in heightened resource recovery, diminished environmental impact, and a stride towards a circular economy within the polyurethane industry.

Flame-retardant and antibacterial flexible polyurethane foams with high resilience based on a P/N/Si-containing system

In this work, the coatings used phosphorylated chitosan (PCS) and GP-108 via the dip-coating method presented exceptional flame retardancy and antibacterial properties for flexible polyurethane foams (FPUF). PCS/GP@FPUF with 35% weight gain of PCS/GP can receive the UL-94 V-0 rating and obtain a 32% reduction of peak heat release rate value compared with that of FPUF, and it remains relatively dense char residues. The effective heat of combustion of PCS/GP@FPUF is 21.6 kJ/g, presenting a 22% decrease compared with that of FPUF. Meanwhile, the PCS/GP coatings mainly have the condensed-phase flame-retardant mechanism associated with the analysis of char residues and the volatile products released through the thermal degradation process. X-ray photoelectron spectroscopy results confirm that the char residues of PCS/GP@FPUF consist of highly-graphitized carbon and it formed P-N-Si synergistic char layers. In addition, the antibacterial rates of PCS/GP@FPUF against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are 99.99%, and the incorporation of GP-108 does not influence the antibacterial properties of PCS. Importantly, the resiliency of FPUFs has been slightly influenced. Briefly, the flame-retardant and antibacterial FPUFs with wonderful resiliency are hopeful to be applied as filler materials for vehicle seats and obtain longer service lives.

Hardening mechanism of waste polyolefin mixtures in the presence of modified bentonite clay

The aim of the work is to obtain and study polymer composite materials based on mixtures of secondary polyolefins and modified polydisperse bentonite clay. The formation features of the structure of mixtures of waste polyolefins in the presence of this-type filler are studied. The data on the changes in the mechanical strength of mixed composites, as well as the results of physico-chemical studies are presented. Mixtures based on waste polymers in the presence of highly dispersed particles of modified polydisperse bentonite are characterized by the improvement of the strength of composites due to increased interfacial interaction in them and by the formation of structure uniformity of the material. This to some extent compensates for the loss of cohesive strength of secondary polymers due to thermal degradation processes. The following conclusions are made: at the phase boundaries, the molecular mobility of polymer chains decreases, which leads to changing the crystallization conditions and to appearing a nonequilibrium stress state; introducing bentonite increases crystalline due to the initiation of physico-chemical interaction; the strength grows due to increased interfacial interaction and structure uniformity; the formation mechanism of a complex of properties of composites consists of two-level adsorption – a modifier on filler particles and active polymer groups on the modified filler surface.

Kinetic Analysis of Thermal Decomposition of Polyvinyl Chloride at Various Oxygen Concentrations

PVC plastic products are common combustible substances seen in fires, but their thermal degradation behavior under different oxygen concentrations has not been adequately studied. The thermal degradation behavior of PVC materials in atmospheres with different oxygen concentrations was analyzed via thermogravimetric–Fourier transform infrared spectroscopy (TG-FTIR). The TG results show that the thermal degradation process of PVC under a non-oxygenated atmosphere occurred in two stages, and the activation energies of the two stages were 130–175 KJ mol−1 and 230–320 KJ mol−1, respectively; under the oxygenated atmosphere, the thermal degradation process occurred in three stages. The activation energies of the three stages were 130–175 KJ mol−1, 145–510 KJ mol−1 and 75–190 KJ mol−1, respectively. And the reaction mechanism of the second stage of thermal degradation was changed from D-ZLT3 to En by the higher oxygen concentration. Infrared spectroscopy (FTIR) was used to analyze the pyrolysis process of PVC in the non-oxygenated atmosphere, and the eight major components were as follows, in descending order according to amount released: C-H stretching > HCl > C-Cl stretching > H2O > CO2 > C-H bending > C-H aliphatic bending > CH2. For the reaction of PVC at an oxygen concentration of 7%, the nine major components, in descending order according to amount released, were as follows: CO2 > HCl > H2O > CO > C-H stretching > C-Cl stretching > C-H aliphatic bending > C-H bending > CH2. For PVC reactions at oxygen concentrations of 14% and 21%, the five major components, in descending order according to amount released, were CO2 > HCl > CO > C-Cl stretching > H2O.

Thermal Degradation Kinetics of Vacuum Residues in the Presence of Chrysotile Supported Ni-Ti Catalyst

For the first time, thermal decomposition of vacuum residue and a mixture of vacuum residue with binary nanocatalysts based on leached and non-leached chrysotile with applied active metals was studied using the thermogravimetry method. It is shown that the thermokinetic parameters of decomposition of vacuum residue and its mixture with binary nanocatalyst are different. The phase composition of the binary nanocatalyst was established through X-ray phase analysis (XRD): (Mg3Si2O5 (OH), NiO and Ti (SO4)2). The quantitative content of elements on the chrysotile surface was determined using X-ray fluorescence analysis: (Ni (4.88%), Ti (7.29%), Si (24.93%), Mg (7.83%), Fe (0.69%) and S (3.89%)). Using atomic emission spectral analysis, the gross quantitative content of supported metals on chrysotile was determined: Ni (4.85%) and Ti (4.86%). A transmission electron microscope showed the presence of finely dispersed particles adsorbed on the surface of and possibly inside chrysotile nanotubes with sizes ranging from 5 to 70 nm. The acidity of the nanocatalyst obtained from the leached active-metal-supported chrysotile was 267 μmol/g and the specific surface area of the nanocatalyst was 54 m2/g. The Ozawa–Flynn–Wall (OFW) method was used to calculate the kinetic parameters of the thermal degradation of vacuum residue and the mixture of vacuum residue with nanocatalysts. Using the isoconversion method, the average values of activation energies and the pre-exponential factor were calculated: 147.55 kJ/mol and 3.37·1016 min−1 for the initial vacuum residue; 118.69 kJ/mol and 1.54·1018 min−1 for the mixture of vacuum residue with nanocatalyst obtained from non-leached chrysotile with applied metals; 82.83 kJ/mol and 2.15·1019 min−1 for the mixture of vacuum residue with nanocatalyst obtained from leached chrysotile with applied metals. The kinetic parameters obtained can be used in modeling and designing the processes of thermal degradation and hydroforming of heavy hydrocarbon raw materials.

Effect of Nanoparticle and Carbon Nanotube Additives on Thermal Stability of Hydrocarbon-Based Drilling Fluids

The article presents the results of experimental study on the effect of additives of silicon oxide nanoparticles, as well as single-walled and multi-walled carbon nanotubes on the colloidal stability and thermal degradation process of hydrocarbon-based drilling fluids. Such a comprehensive study of hydrocarbon-based drilling fluids was carried out for the first time. The effect of the concentration and size of silicon oxide nanoparticles, as well as the type and concentration of nanotubes on the colloidal stability of drilling fluids during thermal aging tests at different temperatures, was investigated. The nanoparticle size varied from 18 to 70 nm, and the concentration ranged from 0.25 to 2 wt.%. Single-walled and multi-walled nanotubes were studied, whose concentration varied from 0.01 to 0.5 wt.%. The thermal aging temperature varied from 30 to 150 °C. According to the results of the investigation, it was shown that the temperature stability of hydrocarbon-based drilling fluids can be significantly improved by adding the above substances. At the same time, it was shown that the use of single-walled nanotubes for thermal stabilization of drilling fluids was several times more effective than the use of multi-walled nanotubes, and tens of times more effective than the use of spherical silicon oxide nanoparticles.