Pyrolysis Behavior Research Articles

Effect of N-heterocyclic carbenes-Pt catalytic system and crosslinking networks on the pyrolytic behavior of liquid silicone rubber

Liquid silicone rubber (LSR) exhibits excellent thermal stability and has been selected for use in a variety of applications where thermal stability, chemical resistance and fire-retardant are required. The enhancement of the organic-to-inorganic conversion of LSR to improve their flame-retardant properties represents a significant area of research. The thermal stability of the platinum catalysts and the crosslinked network structure of the LSR have a considerable influence on the organic-to-organic conversion behavior of LSR. The present study demonstrates the efficacy of N-heterocyclic carbene (NHC) ligand-modified Karstedt's catalysts as catalysts for the curing of LSR by hydrosilylation at room temperature and for the organic-to-inorganic conversion of LSR at elevated temperatures. The catalyst was employed in the preparation of three LSRs with varying network structures, utilizing four polysiloxanes with differing degrees of functionality. The pyrolytic behavior and organic-to-organic conversion rate of these LSRs were investigated using a thermogravimetric analyzer (TG) coupled with a Fourier transform infrared spectrometer (FTIR). The findings indicated that LSRs with the highest crosslink density exhibited the highest organic-to-inorganic conversion rate; however, they demonstrated the lowest fire-resistance. The anomalous behavior has been subjected to further analysis with respect to the mechanical properties of the LSRs and the characteristics of their network structure. LSR coatings with enhanced hardness and fire-resistance are then produced by combining the advantageous properties of both LSRs in a layer-by-layer (LBL) assembly.

Study on the cracking process of epoxy resin under oxygen and water atmosphere based on ReaxFF force field

Amino-cured epoxy resins are widely used in the electrical and electronic industry for their excellent properties. To investigate the mechanism of the effect of O2 and H2O on the pyrolysis behavior of epoxy resin, in this paper, the cross-linked structure of bisphenol A type epoxy resin cured by adducts of diethylenetriamine and butyl glycidyl ether is modeled based on the ReaxFF force field, and the thermal decomposition processes at different temperatures and gas atmospheres were simulated and the pathways of the small molecule products were clarified. The results show that epoxy resin will produce small molecule gas products, such as H2, CO, H2O, OH, CH2O, and free radicals, in the process of pyrolysis; the presence of amino groups also generates nitrogen-containing radicals, such as CN, CH2N, and C2H4N; as the reaction temperature increases, the rate of pyrolysis reaction will be accelerated. The same temperature in oxygen and water atmospheres can accelerate the breakage of epoxy resin main chain by promoting the breakage of carbon and oxygen bonds and, at the same time, promote the generation of small molecule gases, such as H2 and CO.

Thermokinetics and reactive mechanism of lead azide (LA) in atmosphere/temperature mixed environment

To establish the influence of atmospheric and temperature factors on the stability of LA, a combined environmental stress testing device was designed to simulate reaction characteristics. Morphological characterization methods of SEM and FTIR were carried out to explore the changes of crystal structure, as the pyrolysis behavior of LA under the combined environmental stress was investigated by DSC with two isoconversional kinetic methods and thermal safety software (TSS). The research indicates that CO2 and H2O react with LA to generate basic lead carbonate in the air atmosphere, together with the stimulation of thermal stress, the synergistic effect formed microvoids to erode the crystal structure of LA. The microvoid effect reduced the apparent activation energy (Ea) from 156.47 to 29.52 kJ/mol as the order of degradation of thermal stability of LA was Air > N2 > CO2, which demonstrated that CO2 and N2 atmosphere have a particular protective effect for LA storage, transportation, and application. The pyrolysis reaction mechanism model of LA under the combined environment factors testing was the same as the original LA through the calculation of TSS, thereby the findings could contribute to a better understanding of available boundary conditions for LA.

Pyrolysis behaviour and synergistic effect in co-pyrolysis of wheat straw and polyethylene terephthalate: A study on product distribution and oil characterization

Renewable lignocellulosic biomass is a favorable energy resource since its co-pyrolysis with hydrogen-rich plastics can produce high-yield and high-quality biofuel. In contrast to earlier co-pyrolysis research that concentrated on increasing product yield, this study comprehends the synergistic effects of two distinct feedstocks that were not considered earlier. This work focuses on co-pyrolyzing wheat straw (WS) with non-reusable polyethylene terephthalate (PET) for the production of pyrolysis oil. WS and PET were blended in different ratios (100/0, 80/20, 60/40, 40/60, 20/80, and 0/100), and pyrolysis experiments were conducted in a fixed-bed reactor under different temperatures to assess their synergistic effect on oil yield. Synergy rates of up to 7.78 % were achieved on yield for the blends of plastic and biomass at a temperature of 500 °C. In comparison to individual biomass or plastics, co-pyrolyzing PET-biomass blends demonstrated good process interaction and promoted the yields of value-added products. The heating value of the pyrolysis oils was in the range of 16.45–28.64 MJ/kg, which depends on the amount of plastic present in the feedstock. The physical analysis of the oils shows that they can be used for heat production by direct combustion in boilers or furnaces. The correlation between WS and PET was validated with the aid of Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS result demonstrated the presence of different compounds such as O-H compounds, esters, carbonyl group elements, acids, hydrocarbons, aromatics, and nitrogenated compounds in the pyrolysis oil, which differed based on the proportions of PET in the feedstock. The increased hydrocarbon and reduced oxygen percentages in the pyrolysis oil were implicitly caused by enhanced hydrocarbon pool mechanisms, in which the breakdown of PET may be supplied as a hydrogen donor. Overall, waste lignocellulosic biomass and plastics can be used to produce biofuels, which helps reduce the amount of solid waste that ends up in landfills. This study also revealed that future research should be focused on the reaction mechanisms of WS and PET co-pyrolysis in order to examine the synergistic interactions.

A comparative study on the slow pyrolysis of Miscanthus (Miscanthus×giganteus Greef et Deu.) cultivated on agricultural and contaminated soils: Assessment of distribution of final products

This study aims to investigate the slow pyrolysis behavior of uncontaminated (MSC-I - reference) and heavy metals contaminated (MSC-R) samples with heavy metals from the tailings of a Pb-Zn-Cu flotation mine, consisting of whole stems of Miscanthus. Physicochemical properties of raw materials were investigated through instrumental characterization techniques (Atomic Absorption Spectrometry (AAS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD)), while the pyrolysis process was monitored by simultaneous thermal analysis techniques (thermogravimetry (TG) – derivative thermogravimetry (DTG)), coupled with Mass spectrometry (MS), for evolved gas analysis. After determination of the lignocellulose content (cellulose, hemicellulose, and lignin) and extractive of the MSC-I and MSC-R samples, it was found that Pb, Zn, Fe, and Mn in MSC-R lead to very fast decomposition of extractive fraction, which facilitates their distribution in formed bio-char, together with lignin char-participation, acting catalytically. It was established that a much greater fraction of extractives decomposition products and non-volatile heavy metals are incorporated in MSC-R bio-char increasing its yield (23 %), compared to MSC-I bio-char yield (21.5 %). It was identified that MSC-R has increased production of H2, CO, and CO2, while decreased production of CH4, influenced by Fe (Fe has a significant positive effect on CO2 evaluation during MSC-R pyrolysis, enhancing decarboxylation process). It was established that CH4 reforming reactions catalyzed by iron additionally affect methane reduction, and increase production of H2, compared to the reference sample. Isoconversional kinetic analysis showed that pyrolysis reactions profile was strongly conditioned by the presence of heavy metals, such as Cd, Pb, and Zn, because they affect the modification of biomass lignocellulosic structure. Also, it was found that small amounts of Cd present in MSC-R can increase pyrolysis activation energy of three pseudo-components, and inhibit their deoxygenation, thus increasing yield of bio-char.

Coupling kinetic modeling with artificial neural networks to predict the kinetic parameters of pine needle pyrolysis

The pyrolysis behavior of biomass is critical for industrial process design, yet the complexity of pyrolysis models makes this task challenging. This paper introduces an innovative hybrid model to quantify the pyrolysis potential of pine needles, predicting the entire process of their pyrolysis behavior. Through experimental analyses and kinetic parameter calculations of pine needle pyrolysis, the study employs a kinetic model with a chemical reaction mechanism. Additionally, it introduces an improved dung beetle optimization algorithm to accurately capture the primary trends in pine needle pyrolysis. The developed artificial neural network model incorporates meta-heuristic algorithms to address process error factors. Validation is based on experimental data from TG at three different heating rates. The results demonstrate that the hybrid model exhibits strong predictive performance compared to the standalone model, with coefficients of determination (R²) of 0.9999 and 0.999 for predicting the conversion degree and conversion rate of untrained data, respectively. Additionally, the standard errors of prediction (SEP) are 0.249% and 0.449% for predicting the conversion degree and conversion rate of untrained data, respectively.

Pyrolysis process and products characteristics of glass fiber reinforced epoxy resin from waste wind turbine blades

The installed wind power capacity has reached up to 906 GW globally meaning the usage of wind turbine blades (WTBs) with around 9.06 Mt. The waste WTBs with a rapid growth was estimated to be 72.0 kt in 2022 based on the projected lifetime of 20 years. The recycling of fibers reinforced thermoset polymer from waste WTBs has become a knotty environmental issue. This work aimed at studying the pyrolysis behaviors of a glass fibers reinforced epoxy resin materials from a waste WTBs, and revealing the impacts of pyrolysis atmosphere and temperature on the pyrolysis products. It was found that the black glass fibers with deposited carbon and the clean glass fibers were obtained by pyrolysis in N2 and air, respectively. Both pyrolysis in N2 and air produced the pyrolysis oil and gas with similar compositions. The preferable strength of fibers and yield of oil could be obtained at applicable pyrolysis temperature of 450 °C. The oil yields were 13.17 wt.-% and 11.93 wt.-% by pyrolyzing at 450 °C in N2 and air, respectively. The analysis of pyrolysis pathway suggested that the oxygen promoted the decomposition of epoxy resin into small molecules of gases by pyrolysis in air. The utilization of recycled products gas was also discussed. The findings of this work could provide some suggestions to explore a route with low cost to recycling the waste WTBs by pyrolysis.

Effects of atmosphere and stepwise pyrolysis on the pyrolysis behavior, product characteristics, and N/S migration mechanism of vancomycin fermentation residue

Vancomycin fermentation residue (VFR) urgently needs proper treatment due to its complex and hazardous nature. Pyrolysis is a promising treatment method, while the product characteristics of VFR pyrolysis remain unclear. Therefore, the influence of different atmospheres and stepwise pyrolysis (including one-stage reaction in N2 or CO2 and two-stage reaction in N2) on pyrolysis behavior, product characteristics, and N/S migration mechanism during VFR pyrolysis were investigated for the first time in this work. The results showed that VFR mainly decomposed at 180–600 °C, forming non-condensable gas, bio-oil, and biochar. The main released gases included CO2, H2O, NH3, HCN, SO2, and H2S, whereas the N-containing pollutant gas, notably NH3, should be focused due to its high emission (>10 %). Bio-oil was rich in N-containing compounds with a content exceeding 46 %, mainly consisting of Indolizne (9.2–11.5 %), 5H-1-Pyrindine (5.0–9.9 %), and Indole (8.4–9.0 %), and 9-Octadecenamide, (Z)- (1.8–10.1 %). Moreover, the effects of different conditions on the product characteristics were as follows: For the one-stage reaction, compared to N2, the CO2 atmosphere promoted the formation of alcohols (intended product, increasing 2.2–14.6 %), whereas the two-stage reaction in N2 inhibited alcohol production (decreasing 1.1–2.5 %). At CO2 condition, the harmless temperature of VFR reduced from 600 °C (pyrolysis in N2) to 400 °C. Both CO2 (increasing 0.6–1.5 %) and the two-stage reaction in N2 (increasing 0.4–1.0 %) retained more N in the solid. Kinetics showed that the pyrolysis process of VFR conformed to diffusion models and reaction order models (F2/D1/F3/D1 for N2 and F2/D2/F3/D1 for CO2). The VFR transformed to the chemicals and fuels mainly through the deamination, desulfurization, dehydration, decarboxylation, and dehydrogenation reactions. This work provides guidance for harmless disposal and resource utilization during VFR pyrolysis.

Study on detailed reaction pathways of sulfur-containing alkali lignin during supercritical water gasification for hydrogen production

This work was focused on the evolution process of alkali lignin with a macromolecular structure in supercritical water gasification reactions. Using Quantum chemistry calculations and molecular dynamics simulations, the effects of different factors on the reaction process were studied, and the detailed pathways of main products were obtained. The results indicate that the presence of sulfur significantly inhibits the pyrolysis behavior of alkali lignin macromolecular structures. Sulfur significantly impacts the morphology of the intermediate molecular fragments of products containing 5–10 carbon atoms. Sulfur also has a significant inhibitory effect on the ring opening reaction of the benzene ring. Still, its effect on the final gas product distribution is not significant from a microscopic perspective. In addition, high temperature has a significant impact on improving the gasification efficiency of alkali lignin, while the scale of the reaction system has no significant effect on the distribution of gas products. This study will provide theoretical guidance for further improving the supercritical water gasification efficiency of lignin.

Investigation on pyrolysis behavior and kinetic analysis of banana tree bark and coal blends in blast furnace injection

Investigation on pyrolysis behavior and kinetic analysis of banana tree bark and coal blends in blast furnace injection

Predicting the entire pyrolysis process of representative charring material infiltrated with kerosene using an improved artificial neural network

It is crucial to predict the entire pyrolysis process of charring materials infiltrated with flammable liquids to provide guidance for reducing the fire hazards and implementing numerical simulations of fire accidents caused by the leakage of flammable liquids. In the present study, pyrolysis data obtained from the thermogravimetric experiments were preprocessed using linear interpolation and data normalization methods. The processed data set was then used to train the artificial neural network (ANN) framework to predict the pyrolysis behaviors of typical charring material (Mongolian Scots pine) infiltrated with typical flammable liquid (kerosene) under three different conditions: (1) pyrolysis at a constant mass fraction of kerosene with multiple heating rates; (2) pyrolysis at multiple mass fractions of kerosene with a constant heating rate; and (3) pyrolysis at multiple mass fractions of kerosene and multiple heating rates. The ANN, with the double hidden layer structure (6−3), was capable to well predict the entire pyrolysis behaviors of Mongolian Scots pine under all the three scenarios. Besides, five data transformation function (multiplication, exponential function with base e, logarithmic function with base e, square root, and exponentiation function) were applied to the present three input variables (temperature, mass fraction of kerosene, and heating rate) to generate new input variables in order to extract more characteristics among the pyrolysis data. Therein, the ANN utilizing the data transformation functions of multiplication and exponential function with base e exhibited the best predictive ability. Among the three input variables in the ANN (temperature, mass fraction of kerosene, and heating rate), temperature was identified as the most sensitive one to the prediction performance, followed by mass fraction of kerosene, with heating rate being the least sensitive.

Insight into carbon structures and pyrolysis behaviors of coal from the 13C CP/MAS NMR spectra

Carbon structures play an important role in the pyrolysis behavior of coal. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy is a powerful nondestructive technique for characterizing the carbon skeleton structures in coal. In this study, the carbon type distribution, lattice parameters, and chemical bond concentrations of six coal samples with different Vdaf values were investigated using 13C CP/MAS NMR spectra. Typical TGA and Py-GC-MS methods were utilized to obtain information on weight loss and pyrolysis products of the coals. The aromaticity of coal was determined by an adjustment of the apparent area ratio in the 13C CP/MAS NMR spectra, which shows promising potential for predicting key temperatures, characteristic index, and tar quality in coal pyrolysis. Results from the carbon fractions indicated that the total concentrations of chemical bonds in coal are approximately 150 mmol/g, with more Car−Car and Car−H bonds present in highly mature coal samples, and fewer Cal−Cal, Cal−H, and CO bonds. The breaking behaviors of chemical bonds during coal pyrolysis depend on a combination of temperature and concentration. The breakage of Cal−Cal bond contributes significantly to the pyrolytic weight loss of coal, accompanied by the decrease of Cal−H bonds along with the removal of aliphatic groups. Furthermore, as coal maturity increases, tar from fast pyrolysis contains more polycyclic aromatic hydrocarbons with a higher average molecular weight. The average number of aromatic rings in tar components is notably lower than that of aromatic clusters in coal. These results will contribute to a better understanding of the relationship between coal structure and reactivity, and may provide valuable insights for the efficient and clean utilization of coal.

Pyrolysis conversion of multi-layer packaging waste under a CO2 atmosphere: Thermo-kinetic study, evolved products analysis and artificial neural networks modeling

Packaging waste such as beverage carton forms a significant part of municipal solid waste and its pyrolysis behavior, kinetics, and thermodynamics were studied. A four-stage decomposition process was revealed: dehydration below 200 ℃, paperboard degradation at 200–400 ℃, polyethylene devolatilization at 400–550 ℃, and inorganic decomposition at 550–900 ℃. The evolved products included furans and acetic acid during stage II, followed by the presence of 2-butene and 1-pentene in the subsequent stage. Apparent activation energy (Ea) were determined using model-free models, revealing a notable level of comparability among these results. The average Ea was 123.6 kJ/mol within α range of 0.10–0.60, increasing to 233.3 kJ/mol beyond that range. The most probable reaction mechanism was determined, with the one-dimensional model proving more reliable. An artificial neural network model was developed to predict the thermal degradation. The selected topology of 5*15*1 displayed a robust ability to predict the thermal data.

Study on pyrolysis behavior and reaction mechanism estimation of fireproof sealant with TG/FTIR analysis

Study on pyrolysis behavior and reaction mechanism estimation of fireproof sealant with TG/FTIR analysis

Innovative green preparation of activated carbon by combining microwave pyrolysis and self-activation: Pyrolysis behavior, carbon characteristics and arsenic adsorption properties

Self-activation technology offers an eco-friendly strategy to produce activated carbons. This research attempted to enhance the production efficiency of self-activation by introducing microwave heating. Activated carbons were prepared as arsenic adsorbents from bamboo shoot shells (BSS) by combining microwave pyrolysis and self-activation. Microwave pyrolysis showed a faster thermal decomposition rate and lower pyrolysis temperature range than conventional pyrolysis, and H2O and CO2 from pyrolysis acted as activator. Besides, the prediction models of specific surface area (SSA), micropore volume (MPV) and As(V) adsorption capacity (qe) with high accuracy were established using response surface methodology. Based on the qe values, the optimum preparation condition was 1018 °C for 39 min under a microwave power of 1625 W. The activated carbon exhibited satisfactory As(V) adsorption capacity of 4.79 mg/g, with a total pore volume of 0.702 cm3/g and a SSA of 1330 m2/g. This work significantly improved self-activation technology's production efficiency and reduced the arsenic adsorbent's production cost. Furthermore, it also provided a promising strategy for green preparation of activated carbons from biomass resources.

An experimental investigation of the pyrolysis behaviour of pine wood with different fire-retardant additives

An experimental investigation of the pyrolysis behaviour of pine wood with different fire-retardant additives

Thermal Degradation and Chemical Analysis of Flame-Retardant-Treated Jute Fabrics.

Jute is an inherent lignocellulosic fiber, consisting of hemicellulose, α-cellulose, and lignin. Industrial ventilation, automotive composites, upholstery, carpets, military uniforms, hospital furnishings, and curtains necessitate the integration of flame-retardance properties into jute fibers. In this investigation, seven weave-structured jute fabrics were treated using an organophosphorus-based flame-retardant (FR) chemical (ITOFLAM CPN) and a crosslinking agent (KNITTEX CHN) by the pad-dry-cure method. The thermal stability, degradation and pyrolysis behavior of jute was measured using a thermogravimetric analyzer (TGA). Surface morphology and element distribution were scrutinized utilizing a scanning electron microscope (SEM) and an energy-dispersive spectrometer (EDS). The ATR-FTIR (Attenuated Total Reflection-Fourier Transform Infrared Spectrometer) technique has been employed for analyzing the composition of chemicals in the jute fabrics. According to the protocols specified in ISO 14184-1, free formaldehyde detection was carried out on the jute fabrics. The flame-retardance property was significantly improved on all of the jute fabrics after FR treatment. FTIR and SEM-EDS studies revealed the presence of FR chemical deposition on the surface of the jute fabrics. TGA analysis indicated that the fabrics treated with FR exhibited premature degradation, leading to the generation of more char compared to untreated samples. The jute fabrics specifically demonstrated a notable enhancement in residual mass, exceeding 50% after FR treatment. However, it is noteworthy that the FR-treated fabrics exhibited an elevated level of free formaldehyde content, surpassing the permissible limit of formaldehyde in textiles intended for direct skin contact. The residual mass loss percentage after ten washes of FR-treated fabrics remained in a range from 32% to 36%. Twill weave designed fabrics (FRD4 and FRD5) clearly showed a lower thermal degradation temperature than the other weaves used in this study.

2D CFD modeling for pyrolysis of a large biomass particle: Effect of L/D ratio, internal convection and shrinkage

A transient 2D kinetic-heat transfer model for the pyrolysis of a large biomass particle, incorporating, primary and secondary reaction kinetics, internal convection and shrinkage in particles was developed and validated with experimental results. The RMS errors between the predicted and experimental temperature and residual mass fraction were estimated to be small - 0.020, 0.017, 0.011, 0.018 and 0.024, 0.022, 0.016, 0.025 at reactor temperatures of 573, 623, 673, 723 K, respectively. The pyrolysis behaviour was explained by the computed spatial distributions of velocity, pressure, temperature and residual mass fraction within the biomass particle. At a high L/D (∼5), two symmetric hot spots were formed near the two axial flat edges after 400 s, which formed a single dumbbell-shaped in the axial central core after 600 s and existed for a long time of 1500 s. It merged into a single spherical hot spot at the centre after a long reaction time. For a low L/D (∼1), however, an elliptical-shaped hot spot formed after 400 s changes to a spherical hot spot at the particle centre after 500 s. Uniformity in temperature inside the particle was attained much earlier at a smaller L/D ratio.

Molecular simulation on inhomogeneous microaggregation and pyrolysis mechanics of supercritical methylcyclohexane

Affected by the microaggregation of supercritical fluids, supercritical pyrolysis of hydrocarbon fuels shows unique product distributions and pathways. In this work, the role of inhomogeneous microaggregation during supercritical pyrolysis are clarified via computational method, with the benchmark of methylcyclohexane. Characteristic pyrolysis behaviors under supercritical conditions are intimately revealed and characterized through collective variable-driven hyperdynamics (CVHD) simulations. Liquid-like atoms, which representing the inhomogeneity of supercritical fluids are described by the trained machine-learning classifier, then proposed as the specific reason for the increase in the variety and frequency of bimolecular reactions. In addition, the intrinsic pyrolysis mechanism has also been confirmed to regulate the inhomogeneity effect on reactions through comparisons between different hydrocarbons.

Pyrolysis Behavior of Waste Printed Circuit Boards in a Vertical Fixed Bed

Pyrolysis Behavior of Waste Printed Circuit Boards in a Vertical Fixed Bed