Decomposition Of Ethylene Research Articles

Mechanistic Insights on Coverage-Dependent Selectivity Limitations in Vinyl Acetate Synthesis.

Developing improved catalysts for sustainable chemical processes often involves understanding atomistic origins of catalytic activity, selectivity, and stability. Using density functional theory and steady-state kinetic analyses, we probe the elementary steps that form decomposition products that limit selectivity in vinyl acetate (VA) synthesis on Pd surfaces covered with acetate species. Acetate formation and coupling with ethylene control the VA formation catalytic cycle and steady-state coverage, but acetate and ethylene can separately decompose to form CO2. Both decompositions involve initial C-H activations at acetate vacancies, followed by additional C-H activations and eventual C-O formations and C-C cleavages involving reactions with molecular oxygen. Acetate decomposition paths with non-oxidative kinetically-relevant steps exhibit similar free energy barriers to oxidative paths. In contrast, the non-oxidative ethylene path involving an ethylidyne intermediate exhibits a much lower barrier than paths with oxidative kinetically-relevant steps. Ethylene decomposition is very facile at low coverages but is more coverage-sensitive, leading to similar decomposition and VA formation barriers at coverages accessible at steady state, which is consistent with moderate VA selectivity in measurements and ethylene vs. acetate decomposition contributions assessed from regressed kinetic parameters. These insights provide a detailed framework for describing VA synthesis rates and selectivity on metallic catalyst surfaces.

Investigation on the effect of carbon powder structural characteristics derived from ethylene decomposition on powder explosion

Investigation on the effect of carbon powder structural characteristics derived from ethylene decomposition on powder explosion

Enhanced photocatalytic oxidation of gaseous acetaldehyde using Fe-grafted ZnO nanocomposites in a continuous flow reactor

The purification of indoor air is a crucial application of photocatalysis, emphasizing the urgent need for more efficient photocatalytic systems. While photocatalytic oxidation of volatile organic compounds (VOCs) has been extensively studied in the liquid phase, effective removal of VOCs in the gaseous state in indoor air remains a significant challenge. This study focuses on the continuous gas-phase oxidation of gaseous acetaldehyde using ZnO and different weight percentage of Fe-grafted ZnO catalysts under light irradiation. The surface analysis using XPS and HR-TEM confirmed the presence of Fe(III) species, and UV–Vis-DRS analysis demonstrated a shift in the absorption edge towards the visible region. Real-time gas FTIR monitoring of acetaldehyde oxidation revealed that the 0.7% Fe(III)-grafted ZnO composite catalyst achieved a higher removal efficiency (74%) compared to bare ZnO and other Fe(III)-grafted ZnO ratios. The enhanced photocatalytic efficiency of acetaldehyde by Fe(III)-grafted ZnO supports indicated direct interfacial charge transfer (IFCT) from ZnO to Fe(III) species. Additionally, the Fe(III) cluster effectively improved the separation of electrons and holes, preventing their recombination and accelerating O₂ activation to generate O₂•⁻ radicals, which lead to high photocatalytic performance. The 0.7% Fe(III)-grafted ZnO also maintained its performance over a prolonged period of 360 min, showing excellent structural stability and durability across multiple cycles. This study highlights the possible synergistic effect of the ZnO and Fe systems, offering a new perspective on the photocatalytic decomposition of gaseous acetaldehyde in indoor environments.

Biodegradable coating constructed from carboxycellulose nanofibers for high photocatalytic decomposition of ethylene and synergistic antibacterial what of perishable fruits

Postharvest fruits, especially climacteric fruits, are prone to ethylene ripening, browning and aging, microbial growth accelerated decay and other problems in natural environment. Herein, a carboxylated cellulose nanofibers/phytic acid‑titanium dioxide nanoparticles (CPT) biodegradable coating with “photocatalytic antibacterial barrier” structure，was developed by homogeneous dispersion of phytic acid(PA) complexed titanium dioxide nanoparticles (TNPs) in carboxylated cellulose nanofibers(CCNF). The CPT coating achieves effective dispersion and efficient utilization of TNPs through the complexation of PA. The coating ethylene clearance rate of CPT up to 70.89 %. Meanwhile, the coating exhibits excellent antibacterial (99.67 %), UV resistance, gas barrier. It was found that the CPT coating delays fruit ripening caused by ethylene, which effectively maintaining the quality of respiratory climacteric fruits and non- climacteric fruits, extending the shelf life of perishable fruit by up to 9 days. In particular, the coating is virtually biodegradable in soil after 21 days, which offers the possibility of replacing non-biodegradable multifunctional coatings in food packaging.

Molecular simulations and deep neural networks‐based interpretable machine learning modelling of reverse adsorptive MOFs for ethane/ethylene separation

AbstractThe thermal decomposition of ethane (C2H6) and the steam cracking of fossil fuels are the main sources of ethylene (C2H4). However, it usually contains 5%–9% of C2H6 residue, which must be reduced to ensure its utilization during polymerization. C2H6 and C2H4 have comparable kinetic diameters and boiling points (C2H6: 4.44, 184.55 K; C2H4: 4.16, 169.42 K), which makes the separation process very difficult. This contribution employs a methodology that integrates machine learning (ML) with Monte Carlo simulations to evaluate the ddmof database to develop a predictive model for separating ethane (C2H6) and ethylene (C2H4). The ML model's input is the metal–organic frameworks (MOFs) chemical and structural descriptors. The grand canonical Monte Carlo (GCMC) simulations in RASPA software were carried out to calculate the equilibrium adsorption of ethane and ethylene. Different ML models such as random forest, decision tree, and deep neural network models have been tested to estimate the selectivity and ethane uptake from the MOF data being generated. Interpretable ML model using SHapley Additive exPlanations (SHAP) is developed for the better understanding of the impact of the parameters on selectivity and ethane uptake. A user‐friendly graphical user interface (GUI) is presented, allowing users to predict the ethane uptake and selectivity of MOFs simply by entering the values of chemical and structural descriptors.

Decomposition behavior of supercritical ethylene under ultra-high temperature and ultra-high pressure

The gas-phase raw materials in many industrial scenarios currently exist in the reactor in a supercritical state. Unlike gas phase molecules, the supercritical molecules usually exhibited dynamic motion patterns in the system, which made them more susceptible to decomposition. Previous researches mainly focused on low-temperature and low-pressure systems, and few research on decomposition behavior of supercritical molecules under ultra-high temperature and ultra-high pressure were studied. This study focused on the decomposition behavior of supercritical ethylene under ultra-high temperature and ultra-high pressure, the effect of triggering conditions on supercritical ethylene decomposition was investigated. In addition, the temperature and pressure change curves during ethylene decomposition were analyzed to obtain evolution time nodes to determine energy accumulation in supercritical states. Moreover, the gas product distribution and derived explosive carbon were characterized for better evaluating the consequences of supercritical ethylene decomposition. This article aimed to provide theoretical basis and data guidance for energy utilization and conversion in ethylene supercritical systems.

TiO2 for efficient photocatalytic decomposition of acetaldehyde: An investigation of the effects of annealing temperature, humidity, and binder

<scp>TiO₂</scp> for efficient photocatalytic decomposition of acetaldehyde: An investigation of the effects of annealing temperature, humidity, and binder

Compound-specific, intra-molecular, and clumped 13C fractionations in the thermal generation and decomposition of ethane and propane: A DFT and kinetic investigation

The distribution of stable isotopes in organic compounds within geochemical systems reflects the reactions they undergo, which are often kinetically governed and can be elucidated through quantification based on first principles: employing quantum chemical simulations to derive energy barriers and kinetic isotope effects (KIEs), followed by kinetic calculations using these parameters. In this paper, the distribution of 13C in hydrocarbon gases during the thermal generation and decomposition of ethane and propane has been addressed. The work is based on abundant and systematic isotopic data, including the compound- and position-specific 13C compositions, recent improvements in kinetic networks in hydrocarbon generation, and state-of-the-art quantum chemical methods that can process organic geochemical systems involving solid phases. Density Functional Theory computations validate the carbonium path of hydrocarbon generation and the free-radical path of their decomposition under geological conditions. The first step of each path (alkyl sidechain protonation for generation and hydrogen abstraction for decomposition) is the rate-limiting step and determines the 13C fractionations of gaseous hydrocarbons, with the reaction rate constrained by the concentration or accessibility of the active species (hydrated protons and surface free radicals in the two paths, respectively). Alkyl protonation has normal 13C KIEs, but hydrogen abstraction on the surfaces of solid organic matter has inverse ones (substituting 12C by 13C accelerates the reaction). These inverse KIEs explain three isotopic phenomena in gaseous hydrocarbons in their late thermal evolution: 1) the depletion of 13C in ethane and propane accompanied by their decreased fraction in hydrocarbon gases (isotope “rollover”); 2) the reversed 13C sequence with carbon number (δ13Cmethane > δ13Cethane > δ13Cpropane); and 3) the depletion of 13C in the center carbon atoms of residual propane. Isotopic fractionation between gaseous hydrocarbons upon generation is evaluated using the Successive Random Chain-Scission model. The covariation of δ13C in alkanes shows a depletion in CH4 compared with the values expected from the reciprocal of the carbon numbers, indicating that this deviation may be intrinsic instead of mixing with microbial methane. The comparison of intramolecular 13C fractionation of propane between computational and observed data suggests the contribution of isoprenoids at the beginning of the generation, in addition to isotopic homogenization between the center and end carbon atoms through the ring closure of intermediate cations. The 13C–13C clumping exhibits a weak KIE in both the generation and decomposition of ethane; the clumping is essentially stochastically governed. This work demonstrates how first-principle calculations can provide significant insights into the details of geochemical reactions governing the isotopic distributions.

Coating of expanded polystyrene spheres by TiO2 and SiO2–TiO2 thin films

Expanded polystyrene spheres (EPS) were coated by SiO2–TiO2 or TiO2 for application as a fluidized bed in the photocatalytic reactor. Silica coating was realized by the sol–gel process carried out in a vacuum evaporator at 60–70 °C. The most uniform and thin layer of silica coating was obtained by the Stöber method based on the hydrolysis of tetraethyl orthosilicate (TEOS) catalysed by an ammonia solution. Effective TiO2 coating was obtained by the immersion of EPS in the titania aqueous suspension and evaporation of water in a vacuum evaporator. Heating of EPS spheres coated by SiO2, TiO2 or SiO2–TiO2 at the temperatures of 120–140 °C resulted in a shrinkage of their volume. For the thick layer coating, a strong corrugation of EPS surface was observed. The photocatalytic tests showed, that highly corrugated surface of coated EPS slowed down ethylene decomposition, whereas a thin layer coating of both, SiO2 and TiO2 was advantageous.Graphical abstract

Mechanistic aspects of Pd-catalyzed ethylene decomposition in vinyl acetate synthesis

Vinyl acetate has a broad range of applications in the market. However, the side reactions of ethylene decomposition and CO2 formation have a significant effect on the selectivity of vinyl acetate synthesis. In this study, a comprehensive reaction network was calculated by the density functional theory (DFT) method to understand the mechanism of the side reactions. The DFT results indicated that the C-H bond is easier to break than C-C bond except for CCH species during ethylene decomposition on the Pd (100) surface. The introduction of Au on the alloy surface inhibits the decomposition of ethylene, which improves the selectivity of the reaction. The adsorbed O atom inhibits the first three dehydrogenation of ethylene but promotes the CCH species dehydrogenation. The pathway for the decomposition of ethylene is: CH2CH2 → CHCH2 → CHCH → CCH → C+CH, and the C-C bond cleavage of CCH is identified as the rate-determining step. The rate-determining step for CO2 formation is the combination of carbon and oxygen atoms to produce CO, and the alloy surface presents a high energy barrier, hindering CO2 production. This study presents a further mechanistic insight into ethylene decomposition and CO2 formation, which has implications for the control of side reactions in vinyl acetate synthesis.

Estimating the Anti-Viral Performance of Photocatalytic Materials: The Correlation between Air Purification Efficiency and Severe Acute Respiratory Syndrome Coronavirus 2 Inactivation

The coronavirus disease 2019 pandemic has increased the demand for anti-viral products. Photocatalytic materials are used to develop coatings and air purifiers that inactivate severe acute respiratory syndrome coronavirus 2. However, the methods for evaluating the anti-viral performance of photocatalytic materials are time-consuming. To address this problem, herein, we propose a screening test for the anti-viral performance of photocatalytic materials based on the ‘acetaldehyde decomposition test’—an air purification efficiency test used to evaluate the decomposition performance of photocatalytic materials. This test is suitable for screening multiple samples and conditions in a short period. The temporal variation in the acetaldehyde concentration was approximated using an exponential function, similar to the temporal variation in the viral infection values. Thereafter, the slope of the regression line for the acetaldehyde concentration over time was used as an indicator in the screening tests. When the anti-viral performance and acetaldehyde decomposition tests were conducted on the same photocatalytic material, a correlation was observed between the slopes of the regression lines. Overall, the proposed screening test shows good potential for evaluating the anti-viral performance of photocatalytic materials.

Surface exposure engineering on LaMnO3@Co2MnO4 for high-efficiency ethane catalytic combustion

Higher specific surface area and abundant surface oxygen vacancies are considered to be essential to the catalytic combustion. Herein, we elaborately fabricated an innovative catalyst on the basis of LaMnO3@Co2MnO4 under a controllable selective dissolution (SD) treatment for ethane catalytic combustion. La element in perovskite could effectively protect the spinel system as a sacrifice, with MnO2 covering on the spinel surface, thereby enhancing the activity and stability. In combination with XPS, in-situ DRIFT and various characterization results, this acid corrosion could provide induce better reducibility, larger specific surface area, higher Mn4+ and Co3+content and more oxygen vacancies, which played a significant role in promoting the adsorption, activation and decomposition of ethane. Among all as-prepared catalysts, the optimal performance for catalytic ethane combustion was achieved on LMO@CMO-10 catalyst. The T90 of LMO@CMO-10 was 341 °C under space velocity of 80,000 mL·g−1·h−1. This work not only fabricated the catalyst system with higher specific surface area and more oxygen vacancy by SD method, but also provided a potential strategy for the preparation of highly active catalysts.

Potential of 2-ethylhexyl nitrate (EHN) and di-tert-butyl peroxide (DTBP) to enhance the cetane number of ethanol, a detailed chemical kinetic study

Ethanol is one of the most promising renewable liquid fuels to decarbonize the internal combustion engine due to its high production capacity, reasonable cost and low carbon intensity. At the same time, diesel engines are preferred over other powertrain technologies in most hard-to-electrify applications, such as heavy-duty, off-road, marine and rail. However, ethanol’s properties are not suitable for modern diesel engines with ignitability being the main technical barrier for ethanol compression-ignition combustion. Cetane improvers, such as 2-ethylhexyl nitrate (EHN) or di-tert-butyl peroxide (DTBP) may be a solution to enable diesel-like ethanol combustion, but the potential of those additives to increase the cetane number of ethanol is still unclear.In this investigation, detailed chemical kinetic simulations were performed to better understand the mechanisms by which EHN and DTBP affect the ignition reactivity of ethanol. Sub-models of EHN and DTBP chemistry were merged with a chemical kinetic mechanism for ethanol and validated against experimental data. Rate of production analyses and sensitivity analyses were performed to better understand the reactions and species that control the autoignition of ethanol additized with EHN or DTBP. The formation and accumulation of acetaldehyde from ethanol-derived radicals is the bottleneck for ignition, since the remaining ethanol acts as a sink of the OH radicals required for the decomposition of acetaldehyde. A simple model to predict the derived cetane number of fuel blends is proposed and used to estimate the effectiveness of EHN and DTBP in improving the reactivity of ethanol. EHN works better as an additive as compared to DTBP, as it speeds up the main decomposition reactions of the fuel by providing the necessary OH radicals as compared to CH3 provided by DTBP.

Enhanced Degradation of Ethylene in Thermo-Photocatalytic Process Using TiO2/Nickel Foam.

The photocatalytic decomposition of ethylene was performed under UV-LED irradiation in the presence of nanocrystalline TiO2 (anatase, 15 nm) supported on porous nickel foam. The process was conducted in a high-temperature chamber with regulated temperature from ambient to 125 °C, under a flow of reacted gas (ethylene in synthetic air, 50 ppm, flow rate of 20 mL/min), with simultaneous FTIR measurements of the sample surface. Ethylene was decomposed with a higher efficiency at elevated temperatures, with a maximum of 28% at 100-125 °C. The nickel foam used as support for TiO2 enhanced ethylene decomposition at a temperature of 50 °C. However, at 50 °C, the stability of ethylene decomposition was not maintained in the following reaction run, but it was at 100 °C. Photocatalytic measurements conducted in the presence of certain radical scavengers indicated that a higher efficiency of ethylene decomposition was obtained due to the improved separation of charge carriers and the increased formation of superoxide anionic radicals, which were formed at the interface of the thermally activated nickel foam and TiO2.

Molecular simulation of CO production and adsorption in a coal-kaolinite composite gangue slit model.

To reveal the mechanism of CO gas generation and adsorption in coal gangue slits at the microscopic level, a new composite kaolinite-coal-kaolinite (KCK) slit model was constructed by combining the Hongqingliang (HQL) coal molecular model and the Bish kaolinite model to characterize the crack structure of the gangue. It is compared with the kaolinite model (TriK) commonly used in gangue research. Molecular dynamics was used to study the production of CO in different oxygen environments and variation in the adsorption amount, adsorption sites and diffusion coefficient in the temperature range from 293.15 K to 333.15 K. The results indicate that CO mainly comes from the decomposition of ether and phenol in organic structures, and the lower the oxygen concentration, the lesser the CO production time. The KCK model has a higher average adsorption capacity and weaker diffusion capacity mainly due to the additional adsorption sites provided by the carbon-containing structural layer, and CO is mainly adsorbed near the oxygen-containing functional groups. Although kaolinite exhibits bonding adsorption on the Al-O plane, its adsorption site is limited to the surface. The slit model with the carbon structure can better reflect the complex conditions of gas motion in the gangue, thus providing a reference to determine the spontaneous combustion conditions of the gangue hill via the index gas.

Boosting effect of single-atom Sn on catalytic activity of Ni towards synthesis of carbon nanofibers from ethylene

Nickel and its alloys are widely used for the synthesis of carbon nanofibers via catalytic chemical vapor deposition of various hydrocarbons. In the present research, a series of Ni-Sn alloys with tin loading varied in a range from 0.1 to 25.0 at% were prepared and characterized. Alloying of nickel with a small amount of tin was found to accelerate significantly the catalytic process of ethylene decomposition accompanied by carbon deposition. For the NiSn(0.25) sample, the carbon yield reaches 195 g/gcat after 30 min at 550 °C. At the highest Sn loading (25.0 at%), the process is completely suppressed. A new mechanism explaining the observed interaction of ethylene with Ni-Sn alloys was proposed. Single-atom Sn species are responsible for the increased catalytic activity. A single-atom Ni-Sn alloy is considered an efficient catalyst with enhanced stability for the production of carbon nanofibers.

Detonation decomposition of hydrocarbons to produce hydrogen

Detonation decomposition of methane, ethane, propane, butane, propylene and ethylene in their mixtures with oxygen was conducted in a pulsed gas detonation device (PGDD) with a goal of obtaining gaseous hydrogen, H2. Chemical reactions occurring behind the detonation front were elaborated for mixtures differing in the oxygen content. The upper concentration limits of detonation corresponding to minimal oxygen contents (maximal fuel contents), at which detonation is still possible, were determined. It was shown that, in order to maximize the hydrogen yield, 15% of acetylene, C2H2, should be added to methane. The productivity of a PGDD device with a barrel of a diameter of 26 mm and a length of 2 m is 3.60, 3.67, 4.25, 4.39, 4.61 and 5.76 kg h−1 of hydrogen when processing methane, ethylene, ethane, propylene, propane and butane, respectively. Upon detonation of mixtures based on ethylene, propylene and butane, along with hydrogen, nanoscale detonation carbon (NDC) is generated at a rate of 6.9, 6.5 and 5.2 kg h−1, respectively. NDC can be used as an additive to metals and polymers to modify their properties. The obtained results are discussed together with data on the production of hydrogen and NDC by detonation decomposition of acetylene previously obtained by the authors.

Effect of Cu on Performance of Self-Dispersing Ni-Catalyst in Production of Carbon Nanofibers from Ethylene

The development of effective catalysts for the pyrolysis of light hydrocarbons with the production of carbon nanomaterials represents a relevant direction. In the present work, the influence of copper addition on performance of a self-dispersed Ni-catalyst and structural features of the obtained carbon nanofibers (CNFs) was studied. The precursors of Ni and Ni-Cu catalysts were prepared by activation of metal powders in a planetary mill. During contact with the C2H4/H2 reaction mixture, a rapid disintegration of the catalysts with the formation of active particles catalyzing the growth of CNFs has occurred. The kinetics of CNF accumulation during ethylene decomposition on Ni- and Ni-Cu catalysts was studied. The effect of temperature on catalytic performance was explored and it was shown that introduction of copper promotes 1.5–2-fold increase in CNFs yield in the range of 525–600 °C; the maximum CNFs yield (100 g/gcat and above, for 30-min reaction) is reached on Ni-Cu-catalyst at 575–600 °C. A comparative analysis of the morphology and structure of CNF was carried out using electron microscopy methods. The growth mechanism of carbon filaments in the shape of “railway crossties” on large nickel crystals (d &gt; 250 nm) was proposed. It was found that the addition of copper leads to a decrease in the bulk density of the carbon product from 40–60 to 25–30 g/L (at T = 550–600 °C). According to the low-temperature nitrogen adsorption data, specific surface area (SSA) of CNF samples (at T &lt; 600 °C) lies in the range of 110–140 m2/g, regardless of the catalyst composition; at T = 600 °C the introduction of copper contributed to an increase in the specific surface of CNF by 100 m2/g.

Effects of Plant-Based Extract Mixture on Alcohol Metabolism and Hangover Improvement in Humans: A Randomized, Double-Blind, Paralleled, Placebo-Controlled Clinical Trial.

Hangovers are uncomfortable physiological symptoms after alcohol consumption caused by acetaldehyde, a toxic substance in which alcohol is metabolized by alcohol dehydrogenase (ADH). Rapid alcohol and acetaldehyde decomposition are essential to alleviate alcohol handling symptoms. This study investigated the effects of HY_IPA combined with Mesembryanthemum crystallinum, Pueraria lobata flower, and Artemisia indica on alleviating hangovers. A randomized, double-blind, parallel-group, placebo-controlled clinical study was conducted on 80 individuals with hangover symptoms. Alcohol intake was 0.9 g/bw with 40% whiskey, adjusted proportionately to body weight. The Acute Hangover Scale total score was 5.24 ± 5.78 and 18.54 ± 18.50 in the HY_ IPA and placebo groups, respectively (p < 0.0001). All nine indicators of the hangover symptom questionnaire were significantly improved in the HY_IPA group (p < 0.01). Blood alcohol and acetaldehyde concentrations rapidly decreased from 30 min in the HY_IPA group (p < 0.05). ADH and acetaldehyde dehydrogenase (ALDH) activities in the blood of the HY_IPA group were significantly higher than those in the placebo group at 0, 1, and 2 h after alcohol consumption (p < 0.01). The rapid hangover relief was due to increased ADH and ALDH. Therefore, HY_IPA effectively relieves hangover symptoms by decomposing alcohol and acetaldehyde when consumed before alcohol consumption.

The Superiority of TiO2 Supported on Nickel Foam over Ni-Doped TiO2 in the Photothermal Decomposition of Acetaldehyde.

Acetaldehyde decomposition was performed under heating at a temperature range of 25-125 °C and UV irradiation on TiO2 doped by metallic Ni powder and TiO2 supported on nickel foam. The process was carried out in a high-temperature reaction chamber, "The Praying MantisTM", with simultaneous in situ FTIR measurements and UV irradiation. Ni powder was added to TiO2 in the quantity of 0.5 to 5.0 wt%. The photothermal measurements of acetaldehyde decomposition indicated that the highest yield of acetaldehyde conversion on TiO2 and UV irradiation was obtained at 75 °C. The doping of nickel to TiO2 did not increase its photocatalytic activity. Contrary to that, the application of nickel foam as a support for TiO2 appeared to be highly advantageous because it increased the decomposition of acetaldehyde from 31 to 52% at 25 °C, and then to 85% at 100 °C in comparison with TiO2 itself. At the same time, the mineralization of acetaldehyde to CO2 doubled in the presence of nickel foam. However, oxidized nickel foam used as support for TiO2 was detrimental. Most likely, different mechanisms of electron transfer between Ni-TiO2 and NiO-TiO2 occurred. The application of nickel foam greatly enhanced the separation of free carriers in TiO2. As a consequence, high yields from the photocatalytic reactions were obtained.