Vapor Decomposition Research Articles

Upcycling Plastic Waste into Valuable Carbon Nanomaterials

AbstractThe global issue of plastic waste accumulation is now widely acknowledged as a significant environmental challenge that affects all aspects of life, economies, and natural ecosystems worldwide. Hence, it is crucial to develop sustainable solutions to traditional disposal methods. One promising solution involves upcycling plastic waste into valuable carbon nanomaterials such as carbon nanotubes, graphene, and carbon nanofibers, among others. This critical review provides an overview of the problems associated with plastics, including their various types and properties, as well as their significant impact on the environment and the methods currently employed for waste management. Furthermore, it delves into recent advancements in upcycling plastic waste into carbon nanomaterials through four state‐of‐the‐art methods with the potential for scaling up and enabling industrial applications: thermal decomposition, flash joule heating (FJH), chemical vapor decomposition (CVD), and stepwise conversion. For each method, highly influential and seminal papers were selected, and their research approaches and observed results were thoroughly analysed. This upcycling approach transforms plastic waste into valuable resources, promoting a waste‐to‐value concept that reduces environmental impact and supports the circular economy. By creating new materials from discarded plastics, it addresses waste management challenges while generating economic value.

Additive effect of silicone resin on direct current arc quenching performance of a model electric fuse: electrical resistivity and thermal diffusivity of high-temperature Cu/SiO2 vapor mixed with C2H6SiO vapor decomposition

Concerning DC fuses equipped with silica sand (SiO2) as an arc quenching material, the authors have proposed an additive installation of silicone resin (C2H6SiO) on a fuse-element surface to improve the limitation and interruption ability of high DC. This paper describes the additive effect of the silicone resin on the transient resistance of the arc that has formed during the DC interrupting process in a model fuse, based on the measurement result that the arc resistance markedly rises with the silicone mass coated on the fuse element. This phenomenon is subsequently explained as resulting from a thermal diffusivity of high-temperature C2H6SiO/SiO2/Cu vapor. In other words, the mixing of C2H6SiO decomposition vapor into the arc can promote vapor temperature decay through the higher thermal diffusivity, resulting in a rapid increase in the electrical resistivity of the vapor during the DC interrupting process.

Fe Species Supported on Blue-TiO2/WO3 Nanocomposite as Catalyst for the Decomposition of Toluene Vapor under White Light-Emitting Diode Lighting

Fe Species Supported on Blue-TiO₂/WO₃ Nanocomposite as Catalyst for the Decomposition of Toluene Vapor under White Light-Emitting Diode Lighting

Laser-induced fluorescence detection of nitroxyl (HNO) formed from the thermal decomposition of hydroxylammonium nitrate vapor

The decomposition of the ionic liquid hydroxylammonium nitrate (HAN) produces gas phase products which have utility in spacecraft propulsion systems. Among the various gas phase species generated from HAN decomposition is the nitroxyl (HNO) radical, a highly reactive molecule with implications in both chemical and electric propulsion applications. The work described here used a laser-induced fluorescence platform to directly detect the relative density of the HNO radical formed by passing HAN vapor through heated porous disks of varying composition. The use of heated porous 316-stainless steel and aluminum disks showed significant HNO density production and is attributed to a surface hydrogen abstraction mechanism. There was also evidence of surface modification to the metal disks which resulted in a shift in the HNO density temperature profiles. The results reported demonstrate that use of a heated porous material can easily generate a molecular vapor at moderate temperatures for combustion and electric propulsion applications.

On the formation of ammonia from the thermal decomposition of hydroxylammonium nitrate vapor

The ionic liquid hydroxylammonium nitrate (HAN) is a promising propellant for various types of spacecraft propulsion systems. With respect to combustion and plasma-based electric propulsion, the thermal decomposition of HAN into gas phase species provides a convenient feed gas supply. While the decomposition of HAN in the liquid phase has been extensively studied, little is known about the decomposition chemistry of HAN vapor interacting with heated surfaces. The ability to decompose HAN vapor on a reactive surface could provide a means to control the feed gas composition and enhance the performance of spacecraft propulsion systems.In this initial qualitative study, HAN was vaporized and thermally decomposed using porous 316-stainless-steel and quartz disks under vacuum conditions. Decomposition products with low vapor pressures would condense on an in-line quartz tube which was subsequently collected and analyzed with Raman spectroscopy, NMR spectroscopy, and FT-IR spectroscopy. At temperatures above 440 K the 316-stainless-steel system produced significant quantities of ammonia which reacted with vaporized nitric acid to form ammonium nitrate. Temperatures below 440 K yielded partial HAN decomposition which resulted in a binary mixture of HAN and ammonium nitrate. The degree to which HAN was consumed was determined by analysis of the 1008 cm−1N-OH asymmetric Raman band of HAN and the 1049 cm−1 symmetric stretching Raman band of the nitrate ion, NO3−. The quartz system yielded significantly different results with no ammonium nitrate detected at temperatures above 440 K. Reformed HAN was the primary product detected at lower temperatures. The difference in reported measurements and visual observations highlights the distinct differences in HAN vapor decomposition chemistry from the two materials examined.

Chemical upcycling of PVC-containing plastic wastes by thermal degradation and catalysis in a chlorine-rich environment

Chlorine (Cl)-containing chemicals, including hydrogen chloride, generated during thermal degradation of polyvinyl chloride (PVC) and corresponding mixture impede the chemical recycling of PVC-containing plastic wastes. While upgrading plastic-derived vapors, the presence of Cl-containing chemicals may deactivate the catalysts. Accordingly, herein, catalytic upgrading of pyrolysis vapor prepared from a mixture of PVC and polyolefins is performed using a fixed-bed reactor comprising zeolites. Among the H-forms of zeolites (namely, ZSM-5, Y, β, and chabazite) used in this study, a higher yield of gas products composed of hydrocarbons with lower carbon numbers is obtained using H-ZSM-5, thus indicating further decomposition of the pyrolysis vapor to C1–C4 hydrocarbons on it. Although the formation of aromatic compounds is better on H-ZSM-5, product distributions can be adjusted by further modifying the acidic properties via the alteration of the Si/Al molar ratio, and maximum yields of C1–C4 compounds (60.8%) and olefins (64.7%) are achieved using a Si/Al molar ratio of 50. Additionally, metal ion exchange on H-ZSM-5 is conducted, and upgrading of PVC-containing waste-derived vapor to aromatic chemicals and small hydrocarbon molecules was successfully performed using Co-substituted H-ZSM-5. It reveals that the highest yield of gas products on 1.74 wt% cobalt (Co)-substituted H-ZSM-5 is acquired via the selection of an appropriate metal and metal ion concentration adjustment. Nevertheless, introduction of excess Co into the H-ZSM-5 surface decreases the cracking activity, thereby implying that highly distributed Co is required to achieve excellent cracking activity. The addition of Co also adjusted the acid types of H-ZSM-5, and more Lewis acid sites compared to Brønsted acid sites selectively produced olefins and naphthenes over paraffins and aromatics. The proposed approach can be a feasible process to produce valuable petroleum-replacing chemicals from Cl-containing mixed plastic wastes, contributing to the closed loops for upcycling plastic wastes.

Does Sendivogius’ Alchemy Cancel the Celebration of the 250th Anniversary of the Discovery of Oxygen?

Abstract Most chemistry textbooks claim that oxygen was discovered almost simultaneously by Carl Scheele and Joseph Priestley about 250 years ago. Priestley obtained oxygen by heating mercuric oxide (1774), and Scheele -by heating NaNO3, as well as by dissolving pyrolusite in sulfuric acid (1772). The name “oxygen” was given a few years later (1779) by Antoine Lavoisier. This great scientist, often accused of taking advantage of the discoveries of others, conducted experiments related to the decomposition of water vapour over heated iron, as well as the synthesis of water from hydrogen and oxygen. His work was of great importance because it revealed the elemental nature of oxygen and its role in the processes of combustion and respiration. The present article draws attention to the prehistory of the “oxygen theory”. It emphasises the natural philosophy of a forgotten alchemist, healer, and diplomat - Michael Sendivogius (1566-1636) - who popularised his belief that the substance (“Water of life that does not wet the hands”) obtained by heating the “Central Salt” (nitre, KNO3) is part of the air. It is the “secret food of life” used invisibly by every living thing.

Advanced Composite for sp3‐Carbon‐Based Gas Sensing Application from Gold Organometallic Single Nanolayering on Diamondoids

AbstractThe assembly of hybrid materials combining a pure sp3‐C platform from nano‐and microcrystals of molecularly‐defined nanometer‐sized functionalized diamondoids (nanodiamonds) coated with a gold transition metal nanolayer is conducted from the gas phase, following a two‐steps vapor phase dry construction process. By using first the controlled vapor phase self‐assembly of primary phosphine diamantane derivatives, followed by a chemical vapor decomposition of a suited gold organometallic complex the synthesis of the nanocomposite Au@H2P–DiamOH 2 is achieved. The gold deposit surface analysis reveals the formation of a Au–P covalent bonding, which excludes the formation of phosphine oxide, as confirmed at higher depth into the nanocomposite by Hard X‐ray Photoelectron Spectroscopy analysis (HaXPES). The thickness d of the gold layers deposited onto the surface of diamondoids is estimated to be around d = 0.8 ± 10% nm from XPS data, which allows combining the composite Au@H2P–DiamOH 2 with ITO interdigitated electrodes, to produce a long‐life, highly stable and reproducible, n‐type behavior sensor for ammonia detection. A relative response (RR) of 150% at 30 ppm and a limit of detection of 6 ppm are measured at room temperature (20 to 25 °C) and at 45% of relative humidity.

Synthesis of LiPON Solid Electrolyte Films by Thermal Evaporation of Lithium Orthophosphate

Lithium phosphorus-oxynitride (LiPON) films were deposited by the method of anodic evaporation of Li3PO4 in the nitrogen plasma of a low-pressure arc. A method for adjusting the degree of decomposition of vapors is proposed based on a change in the frequency of interaction of electrons with vapors at a constant heating power of the anode-crucible. The conditions ensuring the formation of films with a homogeneous microstructure and ionic conductivity (1–2) × 10−6 S/cm at a deposition rate of 8 nm/min have been determined. It is shown that the degree of vapor dissociation critically affects the morphology of the films and the magnitude of their ionic conductivity. The results of cyclic tests of LiPON films deposited by anodic evaporation in a low-pressure arc are presented.

Interface engineering and impedance matching strategy to develop core@shell urchin-like NiO/Ni@carbon nanotubes nanocomposites for microwave absorption

It is well recognized that interfacial effect and/or impedance matching play a great impact on microwave absorption. Herein, we proposed a facile strategy to take full advantage of interface engineering and impedance matching for boosting microwave absorption performance (MAPs). Three-dimensional (3D) hierarchical urchin-like core@shell structured NiO/Ni@CNTs multicomponent nanocomposites (MCNCs) were elaborately constructed and produced in high efficiency through a facile continuous chemical bath deposition, thermal treatment, and catalytic chemical vapor decomposition process. By controlling the pyrolysis time, the NiO/Ni@CNTs urchin-like MCNCs with different lengths and aggregation degrees of CNTs could be selectively synthesized. The obtained results revealed that the enhanced CNT contents provided abundant interfaces and effectively aggrandized their interfacial effects, which resulted in improved polarization loss, conductivity loss, and comprehensive MAPs. Impressively, the interfaces and impedance matching in the designed NiO/Ni@CNTs urchin-like MCNCs could be optimized by regulating the pyrolysis temperature, which further improved the comprehensive MAPs. And the designed NiO/Ni@CNTs urchin-like MCNCs could simultaneously display strong absorption capabilities, broad absorption bandwidths, and thin matching thicknesses. Therefore, our findings not only provided a simple and universal approach to produce core@shell structured magnetic carbon-based urchin-like MCNCs but also presented an interface engineering and impedance matching strategy to develop the tunable, strong absorption, broadband, lightweight high-efficiency microwave absorbers.

Direct current arc quenching performance of a model electric fuse equipped with SiO2 sand and additive silicone resin as an arc quenching medium: the effect of a vaporized silicone decomposition mixture on transient arc resistance

Most high-power electric fuses installed in DC distributions of automobiles employ silica sand (chemical formula SiO2) as arc quenching material to implement the limitation and subsequent interruption of high direct currents. This paper on arc quenching material describes the effects of the addition of silicone resin (chemical formula C2H6SiO) on SiO2 sand, based on the resistance of an arc discharge in SiO2 vapor mixed with silicone resin vapor. The measurement results obtained for the fuse operation of a model electric fuse show that the addition of silicone resin, e.g. an even coating of silicone resin on the surface of a Cu fuse element, attains a shorter arc quenching time. This phenomenon is subsequently explained based on the rise effect of an arc column resistance achieved by mixing with silicone vapor decomposition. The chemical compositions of high-temperature SiO2 vapor mixed with C2H6SiO vapor decomposition are evaluated to show the predominant chemical species at 30 000 K–5000 K for several C2H6SiO vapor concentrations, . The results obtained for of 10%–50% reveal that a H atom originating from C2H6SiO is present at high molar fractions above 0.1 over a wide temperature range of 12 000 K–5000 K. Further evaluations of the electrical resistivity for the high-temperature vapor show that mixing with C2H6SiO vapor contributes to a rise in at temperatures of 10 000 K–6000 K. A contribution analysis of the reveals that the rise effect of the is accomplished chiefly by the presence of a H atom that has dissociated from C2H6SiO.

Low-temperature Synthesis of Carbon Nanofibers/graphite Felt Composites Under Contactless Induction Heating

In this report induction heating was used for the catalytic chemical vapor decomposition synthesis of carbon nanofibers (CNFs) on Ni-based catalyst. The CNFs were produced with a high yield at a relatively low temperature compared to that observed for conventional heating through convection and conduction. The process also occurred in the absence of secondary toxic organic compounds, formed through side reaction in the high temperature gas-phase or through decomposition on the hot wall of reactor as encountered with traditional Joule heating mode. The improved CNFs yield under induction heating was attributed to the high reaction temperature control thanks to the high temperature regulation rate provided by the induction heating coil. The local heating of the nickel nanoparticles by the electromagnetic field could also contribute to the improvement of the CNFs yield. The results obtained indicate that inductive heating mode could be of great interest for improving the heat transfer in catalytic processes and also to reduce the problem of gradient temperature occurring inside the catalyst bed during the operating of highly exothermic or endothermic processes. It is expected that such electricity-driven heating mode could have contributed in an efficient way toward the electrification of different catalytic processes in order to reduce the associated carbon footprint.

ZnFe2O4 nanoparticles with iron-rich surfaces for enhanced photocatalytic water vapor splitting

Photocatalytic water splitting has emerged as a promising avenue for the utilization of solar energy to produce hydrogen. To advance the development of photocatalytic hydrogen production, the optimization and design of novel photocatalysts is a crucial task. In this study, ZnFe2O4 nanoparticles with iron-rich surfaces were synthesized through alkali treatment and employed in photocatalytic water vapor decomposition. The alkali-treated ZnFe2O4 displayed superior photocatalytic activity, with the optimized sample exhibiting an impressive H2 generation rate of 61.9 μmol·g−1 after 5 h of irradiation, which is significantly higher than the untreated ZnFe2O4 sample (15.9 μmol·g−1). This enhanced performance is attributed to the improved separation of photogenerated carriers and the improved adsorption of water molecules on the iron-rich ZnFe2O4 surface. This research may provide a valuable guide for the design of highly active ternary oxide/sulfide semiconductor photocatalysts for water vapor splitting.

High-temperature thermal decomposition of triphenyl phosphate vapor in an inert medium: Flow reactor pyrolysis, quantum chemical calculations, and kinetic modeling

High-temperature thermal decomposition of triphenyl phosphate vapor in an inert medium: Flow reactor pyrolysis, quantum chemical calculations, and kinetic modeling

Photocatalytic Removal of Toluene Vapour Pollutant from the Air Using Titanium Dioxide Nanoparticles Supported on the Natural Zeolite.

The emission of volatile organic compounds (VOCs) in industrial and urban areas has adverse effects on the environment and human health. Toluene, the main pollutant among the VOCs, has wide applications in different industries such as plastics, adhesives, silicone sealant, paint, etc. This study aimed to remove of toluene from the air by using TiO2 nanoparticles supported on the natural zeolite using the photo-catalytic process. This is an experimental study that was conducted in 2017 in the Chemical Agents Laboratory of the Occupational Health Engineering Department at Jundishapur University in Ahvaz. Toluene vapour decomposition was carried out using UV/ZE, UV/TiO2, and UV/TiO2-ZE under continuous flows conditions. The effects of toluene initial concentration, retention time, and nanocomposite surface weight on toluene vapour decomposition were also investigated. When UV/TiO2 and UV/TiO2-ZE systems are performed, increasing the initial toluene concentration reduces the efficiency of photocatalytic decomposition. The SEM images of TiO2-ZE catalyst show that zeolite pores were occupied by titanium dioxide nanoparticles. Moreover, the combination of titanium dioxide nanoparticles and zeolite has an incremental effect on toluene decomposition. Increasing retention time raises toluene decomposition, and the increased nanocomposite surface weight raises decomposition to the maximum level (70%) at 33.68 mg/cm2 weight and then decreases. The increasing toluene decomposition rate by using the TiO2-ZE nanocomposite can be due to the incremental effect of absorption and photocatalytic decomposition.

Photocatalytic Decomposition of Ethanol Vapour by Anodic TiO2 Nanotube Arrays Modified by Metal Nanoparticles

Photocatalytic Decomposition of Ethanol Vapour by Anodic TiO2 Nanotube Arrays Modified by Metal Nanoparticles

Comprehensive analysis of hydrogen production from various water types using plasma: Water vapour decomposition in the presence of ammonia and novel reaction kinetics analysis

The interest in nonthermal discharge plasma has recently increased over the last few decades due to the ability to generate new radicals at atmospheric pressure. This paper presents a comprehensive analysis of the dissociation processes and reaction rates of various water vapour samples by dielectric barrier discharge plasma (DBD). The influence of water contamination and the presence of ammonia (NH3) on hydrogen production from water vapour was investigated. A novel reaction rate expression was proposed to fit the plasma-water vapour experiment results. The hydrogen production and conversion rate of pure reverse osmosis (RO) water samples showed greater results than the contaminated water samples in all experiments at different tested bubbling temperatures. The higher conversion rate was obtained from RO water combined with 1%NH3 at a bubbling temperature of 50 °C and was 1.17%. The water contamination influenced the generated DBD plasma micro discharges, consequently decreasing the electron collisions, leading to lower water vapour conversion into constituent elements H2 and O2. It was also found that the influence of ammonia on the water vapour decomposition was related to the NH3 concentration. Moreover, the reaction rate showed good agreement with the experimental results. It was observed that the energy efficiencies were obtained at an operating temperature of 50 °C for pure RO, GTW, and CTW water samples enhanced by adding 1%NH3, for example, the RO energy efficiency value at a bubbling temperature of 50 °C increased from 0.133% to 1.15% because of more hydrogen was generated. It implies that the water vapour decomposition processes are influenced by the following parameters: input gas temperature, reaction time, plasma power, oven or reactor heating temperature, the separation method, sampling method, and sampling collection time.

Temperature Dependence of Thermal Conductivity of Giant-Scale Supported Monolayer Graphene.

Past work has focused on the thermal properties of microscale/nanoscale suspended/supported graphene. However, for the thermal design of graphene-based devices, the thermal properties of giant-scale (~mm) graphene, which reflects the effect of grains, must also be investigated and are critical. In this work, the thermal conductivity variation with temperature of giant-scale chemical vapor decomposition (CVD) graphene supported by poly(methyl methacrylate) (PMMA) is characterized using the differential transient electrothermal technique (diff-TET). Compared to the commonly used optothermal Raman technique, diff-TET employs joule heating as the heating source, a situation under which the temperature difference between optical phonons and acoustic phonons is eased. The thermal conductivity of single-layer graphene (SLG) supported by PMMA was measured as 743 ± 167 W/(m·K) and 287 ± 63 W/(m·K) at 296 K and 125 K, respectively. As temperature decreased from 296 K to 275 K, the thermal conductivity of graphene was decreased by 36.5%, which can be partly explained by compressive strain buildup in graphene due to the thermal expansion mismatch.

Effective Decomposition of Water Vapor in Radio-Frequency Plasma with Carbon Deposition on Vessel Wall

Effective Decomposition of Water Vapor in Radio-Frequency Plasma with Carbon Deposition on Vessel Wall

In situ synthesis of highly stable FeCo alloy encapsulated in carbon from ethanol

– FeCo alloy nanoparticles encapsulated in carbon were synthesized in situ via chemical vapor decomposition using ethanol as carbon precursor at temperatures of 400, 500, 600 and 700 °C. The study was carried out in order to obtain a material with high chemical and thermal resistance. The materials were characterized by X-Ray Diffractometry (XRD), Magnetometry, Mössbauer Spectroscopy (ME), Raman Spectroscopy, Thermogravimetric Analysis (TGA), Temperature Programmed Reduction (TPR-H2), Temperature Programmed Desorption (TPD-NH3 and TPD-CO2), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Gas Chromatography (GC). The results indicated that an increase in the synthesis temperature directly influences the amount of carbon deposited on the alloy and, consequently, on its encapsulation. The increase in the synthesis temperature also provided chemical stability against pH variations between 3 and 11, greater resistance against oxidation, greater thermal stability, as well as an increase in the graphitization degree. SEM and TEM images confirmed the presence of carbon nanotubes whose organization is greater for the sample synthesized at higher temperature; the tip of nanotubes showed the encapsulated FeCo alloy nanoparticle. Methylene blue (MB) adsorption was performed as a model to evaluate the encapsulation degree for the alloy, which is favored at higher temperatures.