Search Results (177)

Rapid economic growth has led to an increase in the use of multilayer plastic packaging, which involves complex polymer compositions and hinders recycling. This study investigated the catalytic pyrolysis of plastic packaging waste in a 3000 cm³ semibatch reactor, aiming to optimize kerosene-like hydrocarbon production. The temperature (420–500 °C), N₂ flow rate (25–125 mL/min), and catalyst loading (5–20 wt.%) were examined individually and in combination with activated carbon and an Fe-doped dolomite (Fe/DM) catalyst. Central composite design (CCD) and response surface methodology (RSM) were used to identify the optimal conditions and synergistic effects. Pyrolysis product analysis involved simulation distillation gas chromatography (Sim-DGC), gas chromatography/mass spectrometry (GC/MS), and Fourier transform infrared (FT-IR) spectroscopy. The optimal conditions (440 °C, 50 mL/min N₂ flow, catalyst loading of 10 wt.% using a 5 wt.% Fe-doped dolomite-activated carbon 0.6:0.4 mass/molar ratio) yielded the highest pyrolysis oil (79.6 ± 0.35 wt.%) and kerosene-like fraction (22.3 ± 0.22 wt.%). The positive synergistic effect of Fe/DM and activated carbon (0.6:0.4) enhanced the catalytic activity, promoting long-chain polymer degradation into mid-range hydrocarbons, with secondary cracking yielding smaller hydrocarbons. The pore structure and acid sites of the catalyst improved the conversion of intermediate hydrocarbons into aliphatic compounds (C₅–C₁₅), increasing kerosene-like hydrocarbon production. Full article

The emergence of plastics as an essential item in modern society has led to the problem of accumulating plastic waste. Accordingly, research is being conducted around the world to reduce the production of new plastics and develop technologies to recycle waste plastics. Among the existing waste plastic recycling technologies, oil production is possible through pyrolysis, but the pyrolysis oil produced in this way has a wide carbon range (more than C5–C25), and a very high olefin content (the presence of aromatic compounds), and the resulting high calorific value of pyrolysis oil is limited in its application range. In the case of oil obtained by pyrolyzing waste plastic containing Cl, there is a concern about corrosion in the reactor. Accordingly, it is possible to diversify the range of use of pyrolysis oil produced by suppressing corrosion through Cl removal as well as oil upgrading through cracking. Therefore, this study used red mud mixed with a series of adsorbents for Cl removal and pyrolysis oil upgrade. The adsorbent was physically mixed with a binder (kaolin or methylcellulose) and activated carbon, and the results before and after the reaction were confirmed through basic characteristic analysis. Full article

Pyrolysis is an important methodology for achieving efficient and clean utilization of coal. Lump coal pyrolysis demonstrates distinct advantages over pulverized coal processing, particularly in enhanced gas yield and superior coke quality. As a critical parameter in lump coal pyrolysis, particle size significantly influences heat transfer and mass transfer during pyrolysis, yet its governing mechanisms remain insufficiently explored. This research systematically investigates pyrolysis characteristics of the low-rank coal from Ordos, Inner Mongolia, across graded particle sizes (2–5 mm, 5–10 mm, 10–20 mm, and 20–30 mm) through pyrolysis experiments. Real-time central temperature monitoring of coal bed coupled with advanced characterization techniques—including X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), gas chromatography (GC), and GC–mass spectrometry (GC-MS)—reveals particle-size-dependent pyrolysis mechanisms. Key findings demonstrate that the larger particles enhance bed-scale convective heat transfer, accelerating temperature propagation from reactor walls to the coal center. However, excessive sizes cause significant intra-particle thermal gradients, impeding core pyrolysis. The 10–20 mm group emerges as optimal—balancing these effects to achieve uniform thermal attainment, evidenced by 20.99 vol% peak hydrogen yield and maximum char graphitization. Tar yield first demonstrates a tendency to rise and then decline, peaking at 14.66 wt.% for 5–10 mm particles. This behavior reflects competing mechanisms: enlarging particle size can improve bed permeability (reducing tar residence time and secondary reactions), but it can also inhibit volatile release and intensify thermal cracking of tar in oversized coal blocks. The BET analysis result reveals elevated specific surface area and pore volume with increasing particle size, except for the 10–20 mm group, showing abrupt porosity reduction—attributed to pore collapse caused by intense polycondensation reactions. Contrasting previous studies predominantly focused on less than 2 mm pulverized coal, this research selects large-size (from 2 mm to 30 mm) lump coal to clarify the effect of particle size on coal pyrolysis, providing critical guidance for industrial-scale lump coal pyrolysis optimization. Full article

Government regulations have required consumer products—electrical and electronic components, toys, furniture, clothing, and cars— to meet ever-increasing flame resistance standards, and industry has met these norms by adding brominated fire retardants. However, end-of-life treatment and up-cycling of these plastics is challenging as the brominated compounds are endocrine disruptors, bioaccumulators, and persist in the environment. Pyrolysis, catalytic cracking, or combustion, to recover its fuel value, produces toxic brominated dibenzodioxins and dibenzofurans Here, we demonstrated the efficacy of a solvothermal treatment that extracts up to 99% of the bromine from high-impact polystyrene (HIPS) and polystyrene (PS) in electrical and electronic waste (e-waste). The process operated between 160 °C and 230 °C with ethylene glycol or triethylene glycol as the solvent and NaOH or KOH as the extraction agent (0.5 M to 2 M). The reaction rates depended on the particle size: 60 mm plastic chunks took up to between 4 and 24 h to react while fibers 3 mm in diameter reacted in less than 5 min. Full article

Fast microwave pyrolysis technology can effectively convert brown coal into hydrogen-rich syngas. However, the unique pyrolysis behaviour of brown coal under microwave conditions is not fully understood in comparison with conventional pyrolysis. This study used Victorian brown coal as a raw material to conduct pyrolysis experiments under conventional and microwave heating methods. The results demonstrate that the microwave-assisted pyrolysis of Victorian brown coal can selectively crack polar functional groups, enhancing H₂ and CO production via radical-driven secondary reactions and gasification, while conventional heating favours the formation of tar containing phenols and fewer aromatic compounds. The result is a high-quality syngas (75.03 vol.%) with a hydrogen yield of 10.28 (mmol Gas/g Coal (daf)) at 700 °C under microwave heating, offering a scalable route for valorising low-rank coals. Full article

This study employed a two-stage fixed-bed pyrolysis-reforming reactor to investigate H₂ production behaviors from municipal solid waste (MSW) and biomass with their self-derived catalysts under different operating parameters. The self-derived catalysts are prepared by mechanically mixing pyrolysis-derived chars with CaO and iron powders. The main results are as follows: (1) The higher oxygen content in biomass facilitates oxidative dehydrogenation reactions, enabling in situ generation of H₂O, which results in a higher H₂/CO ratio for biomass compared to MSW under steam-free conditions. (2) There are optimal values for the reforming temperature and steam-to-feedstock ratio (S/F) to achieve best performance. In the presence of steam, MSW generally exhibits superior H₂ and syngas production performance to biomass; (3) Both MSW char (MSWC)- and biomass char (BC)-based catalysts showed satisfied H₂ production and tar cracking performance at 850–900 °C, and the MSWC-based catalyst demonstrated better catalytic activity than the BC-based catalyst due to its higher contents of several active metals. In addition, the iron powder can be recycled easily, proving the effectiveness of the self-derived convenient and cheap catalysts. Full article

Tetrafluoroethylene (TFE), as a key basic chemical raw material, has an irreplaceable position in strategic emerging industries involving high-end materials, electronics, chemicals, and pharmaceuticals. Currently, TFE is industrially produced via the vapor cracking of difluoromonochloromethane (R22). However, there is a gap between China and the developed countries in the high-end tetrafluoroethylene monomer, the purity of tetrafluoroethylene monomer is difficult to reach the high purity requirement of 99.999%, and the content of the key impurities that determine the nature of the functional materials is high, which leads to a series of problems of instability in the performance of the high-end and special products and high media loss. To enhance the purity of TFE monomers produced by the pyrolysis reactor of R22 and water vapor, the fluid dynamics simulations of the reactor model were conducted using Ansys Fluent. The reactor model was initially constructed using Space Claim, followed by mesh generation with Fluent Meshing and other relevant configurations. Both cold-state and thermal-state simulations were performed. The cold-state simulation analyzed the effects of temperature, flow velocity, and turbulence models on the turbulent gas flow and mixing processes within the reactor model. The thermal-state simulation examined the impacts of reaction process variations on internal temperature, turbulence, component distribution, and outlet component concentrations during the actual reaction process. Finally, the inlet flow rate and structure of the reactor were optimized. The results indicated that the optimal inlet flow rates for R22 and water vapor were 0.2–0.3 kg/s and 0.4–0.5 kg/s, respectively. In practical production, the internal fluid mixing achieved an optimal value after modifying the inlet structure to a T shape. This study provides new insights into the pyrolysis reaction and lays the foundation for further improving the purity of TFE monomers. Full article

Louise Nevelson’s Erol Beker Chapel of the Good Shepherd (1977) is a sculptural environment consisting of wooden sculptures painted a monochromatic white color. The paints show signs of degradation including cracking, chipping, peeling, and the formation of blisters and powdery efflorescence. A significant amount of pentaerythritol (PER) detected during a former analysis was concluded to originate from an alkyd paint. We show that the PER originates from the PVAc paint on the sculptures, which we have determined to be an intumescent, fire-retardant (IFR) coating. IFR paints and coatings are functional materials designed specifically to delay the combustion of their substrate. At least one other sculpture by Louise Nevelson is known to have been painted with an IFR coating. Our analyses by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), pyrolysis–gas chromatography/mass spectrometry (Py-GCMS), and cross-section microscopy show the presence and distribution of common IFR additives including PER, dicyandiamide, melamine, inositol, ethylenediamine, and phosphates. These are present throughout the PVAc paint and are enriched in the powdery efflorescence. In addition, the degradation behavior of the paint is typical for IFR coating systems that have been exposed to uncontrolled environmental conditions and especially high humidity events. Full article

The generation of pyrolysis liquids and gases with poor quality is a limiting factor for the development of the recycling process of fiber-reinforced plastic waste. In this article, the life cycle assessment (LCA) of an advanced two-step pyrolysis process to recycle glass fiber-reinforced polyamide waste is presented. First, the solid waste is pyrolyzed by heating up at 3 °C/min to 500 °C in a tank reactor. The generated volatiles are subsequently thermally cracked at 900 °C in a tubular packed bed reactor. The process is able to reclaim the glass fibers similarly to the conventional one reactor pyrolysis, while producing liquids and gases with better properties. The large quantity of oxygenated pyrolysis oils generated in the conventional pyrolysis are cracked into gaseous hydrocarbons, CO, CO₂ and a minor aqueous liquid. The pyrolysis gases become the main product of the process, presenting an interesting composition of hydrogen (39.9 vol.%), methane (22.5 vol.%), carbon monoxide (19.5 vol.%) and ethylene (10.8 vol.%). The LCA shows that advanced pyrolysis demonstrates better environmental performance than conventional pyrolysis, avoiding fossil resource scarcity and reducing global warming by half and human carcinogenic toxicity by one third. Full article

In this study, Kerogen conversion and oil production laboratory modeling results in Bazhenov formation source rock samples (Western Siberia, Russia) are presented. Two samples from one well with a similar composition and immature type II kerogen, which were accumulated in the same deep-sea conditions, were used for this investigation. Hydrous pyrolysis was performed under 300 °C, with liquid products and a sample portion collected every 12 h to study kerogen parameters via pyrolysis and the synthetic-oil composition via GC–MS. The transformation of pyrolytic parameters was similar to the natural trend previously determined for Bazhenov source rocks with different maturities. The synthetic oils’ normal alkane composition and biomarker parameters transformed with time. Sedimentary conditions and lithology biomarker parameters presumed to be constant (Pr/Ph, Ph/C18, H29/H30, and DBT/Phen) changed depending on the heating duration. The oil maturation increased slightly. Differences between the samples were detected in hydrocarbon generation endurance (5 and 8 days), n-alkane composition, and C27/C29 and DBT/Phen. A hypothesis about the influence of kerogen variability and mineral matrix on oil production was made. This paper provides the basis for more detailed and accurate investigation of the factors affecting kerogen cracking and hydrocarbon formation. Full article

In recent years, vast amounts of plastic waste have been released into the environment worldwide, posing a severe threat to human health and ecosystems. Despite the partial success of traditional plastic waste management technologies, their limitations underscore the need for innovative approaches. This review provides a comprehensive overview of recent advancements in chemical and biological technologies for converting and utilizing plastic waste. Key topics include the technical parameters, characteristics, processes, and reaction mechanisms underlying these emerging technologies. Additionally, the review highlights the importance of conducting economic analyses and life cycle assessments of these emerging technologies, offering valuable insights and establishing a robust foundation for future research. By leveraging the literature from the last five years, this review explores innovative chemical approaches, such as hydrolysis, hydrogenolysis, alcoholysis, ammonolysis, pyrolysis, and photolysis, which break down high-molecular-weight macromolecules into oligomers or small molecules by cracking or depolymerizing specific chemical groups within plastic molecules. It also examines innovative biological methods, including microbial enzymatic degradation, which employs microorganisms or enzymes to convert high-molecular-weight macromolecules into oligomers or small molecules through degradation and assimilation mechanisms. The review concludes by discussing future research directions focused on addressing the technological, economic, and scalability challenges of emerging plastic waste management technologies, with a strong commitment to promoting sustainable solutions and achieving lasting environmental impact. Full article

Biomass offers a renewable pathway for sustainable infrastructure, particularly in bio-oil production from biomass through processes such as fast pyrolysis to be used as an alternative to asphalt binders. This review explores biomass sources, production techniques, and the role of bio-oil in addressing the demand for eco-friendly materials in the pavement construction industry. The review also examines the upgrading processes of bio-oil, its physical and chemical properties, and its application in producing bio-modified asphalt binder (BMA). The use of bio-oils in asphalt binders not only reduces the carbon footprint but also promotes the utilization of renewable resources, contributing to a more sustainable pavement industry. Additionally, bio-oil incorporation enhances asphalt binder performance by improving rutting resistance at high temperatures and stiffness at low temperatures, while reducing susceptibility to low-temperature cracking. Challenges include variability in high-temperature performance and moisture sensitivity. Based on the findings of this comprehensive review, future research directions should focus on optimizing production processes, broadening biomass feedstocks, and mitigating moisture issues to align bio-oil properties with asphalt binder specifications. Full article

Novel Ni/SBA-15 catalysts were synthesised and their activity in the dry reforming of methane process was assessed. These materials were prepared into extrudates shaped like pellets and tested in a pyrolysis pilot plant fitted with a catalytic reactor for sewage sludge pyrolysis tar removal. The Ni/SBA-15 catalyst pellets remained highly active and stable throughout the test’s duration, converting 100% tar in the hot gas to smaller non-condensable gases, thereby increasing the pyrolysis gas fraction and eliminating the problematic tar in the vapour stream. Catalyst characterisation with Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), and Thermogravimetric Analysis (TGA) confirmed that both the Ni/SBA-15-powered catalyst and the pellets were resistant to sintering and carbon deposition and remained highly active even with relatively high-level sulphur in the feed stream. The Ni/SBA-15 catalyst extrudates were prepared by mixing the powdered catalyst with varied amounts of colloidal silica binder and fixed amounts of methyl cellulose and water. The highest mechanical strength of the extrudates was determined to be of those obtained with 36% of the inorganic binder. The physical properties and catalytic activity of Ni/SBA-15 pellets with 36% colloidal silica were compared with the original powdered Ni/SBA-15 catalyst to assess the binder inhibitory effect, if any. The results confirmed that colloidal silica binder did not inhibit the desired catalyst properties and performance in the reaction. Instead, enhanced catalytic performance was observed. Full article

To reach agreed-on climate goals, it is necessary to develop new energy carriers and industrial materials that are carbon-neutral. To combat global warming and keep Earth’s temperature from increasing by 1.5 °C, some of these solutions need to be carbon-negative. This study fulfills this criterion by producing clean hydrogen and biocarbon suitable for the metallurgic industry through the thermal decomposition of methane using biocarbon as a catalyst. Five different biomass samples were used to prepare biocarbons at a pyrolysis temperature of 1000 °C with a holding time of 90 min. When methane was cracked at 1100 °C with a holding time of 90 min, the highest hydrogen production was 105 mol/kg biocarbon, achieved using birch bark. The lowest hydrogen yield, of 68 mol/kg biocarbon, was achieved with steam-explosion pellets. All the biocarbons showed substantial carbon deposition from cracked methane on their surfaces, with the highest deposition on birch bark and spruce wood biocarbons of 42% relative to the biocarbon start weight. The carbon deposition increased with the decomposition temperature, the methane share in the purge gas and the holding time. The steam-explosion pellets, after deactivation, had a CO₂ reactivity that was comparable to coke, a reducing agent that is commonly used in manganese-producing industries. About 90% of the potassium and sodium were removed from the biocarbon during catalytic decomposition of methane performed at 1100 °C. The alkali removal was calculated relative to the biocarbon produced under the same conditions, but with 100% N₂ purge instead of CH₄. After catalytic decomposition, the surface area of the biocarbon was reduced by 11–34%, depending on the biocarbon type. Full article

The fabrication of metal oxide semiconductor heterostructures is a major way to enhance their properties in photocatalytic and antibacterial applications. In the present work, ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂O₃ are chosen to create the heterostructure of thin films using the spray pyrolysis method. This paper compares the experimental results of the structural and morphological properties of the prepared thin layers using XRD, Raman and SEM. The X-ray diffraction shows that the obtained thin film heterostructures crystallize in a hexagonal phase of ZnO, a cubic phase of In₂O₃ and a tetragonal structure of SnO₂, with all of the preceding phases positioned on the rhombohedral phase of the hematite α-Fe₂O₃. In addition, the SEM study provided the morphology and surface structure and confirmed the presence of a highly folded, rough, uneven surface with imperfections of 20 and 65 nm for In₂O₃/α-Fe₂O₃ and SnO₂/α-Fe₂O₃. The photoactivity of the prepared materials was tested via the photocatalytic degradation of methylene blue (MB) dye. Consequently, our findings demonstrate that the cracked surface improves the rapid absorption of contaminants and allows water to easily pass through the surface of the thin layers. Finally, the antibacterial abilities of ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂O₃ thin films were investigated by using the agar well-diffusion technique, comparing the results to the Gram-negative of Pseudomonas aeruginosa and Gram-positive of Bacillus subtilis, and these thin films were found to have high antibacterial activity. Full article