Catalytic Oxidation Of Ethylene Research Articles

Redox-induced controllable engineering of MnO2-MnxCo3-xO4 interface to boost catalytic oxidation of ethane

Multicomponent oxides are intriguing materials in heterogeneous catalysis, and the interface between various components often plays an essential role in oxidations. However, the underlying principles of how the hetero-interface affects the catalytic process remain largely unexplored. Here we report a unique structure design of MnCoOx catalysts by chemical reduction, specifically for ethane oxidation. Part of the Mn ions incorporates with Co oxides to form spinel MnxCo3-xO4, while the rests stay as MnO2 domains to create the MnO2-MnxCo3-xO4 interface. MnCoOx with Mn/Co ratio of 0.5 exhibits an excellent activity and stability up to 1000 h under humid conditions. The synergistic effects between MnO2 and MnxCo3-xO4 are elucidated, in which the C2H6 tends to be adsorbed on the interfacial Co sites and subsequently break the C-H bonds on the reactive lattice O of MnO2 layer. Findings from this study provide valuable insights for the rational design of efficient catalysts for alkane combustion.

Influence of Water on the Catalytic Oxidation of Ethane on IrO2(110)

Influence of Water on the Catalytic Oxidation of Ethane on IrO₂(110)

Efficient Catalytic Oxidation of Ethylene at 0 °C on an in Situ Carbon Modified Pt Catalyst Supported on SBA-15.

The design of efficient catalysts for catalytic ethylene (C2H4) oxidation is of crucial importance for extending the shelf life of fruits and vegetables. Herein, a carbon modified SBA-15 supported Pt catalyst (Pt/CSBA-15) was prepared in situ by a facile solid phase grinding-infiltration-inert atmosphere calcination method. Characterization results reveal that in the Pt/CSBA-15 catalysts thin carbon layers are successfully formed in the hexagonal pores of SBA-15. Additionally, Pt particles are well dispersed in the channels of SBA-15, and Pt/CSBA-15 has a smaller Pt particle size than the catalyst without carbon modification (i.e., Pt/SBA-15). O2 is more feasibly adsorbed and activated on small-sized Pt particles, and in situ formed carbon species enhance the hydrophobicity of catalysts. As a result, both 3Pt/CSBA-15 and 5Pt/CSBA-15 are able to maintain 100% conversion of 50 ppm of C2H4 for more than 7 h at 0 °C. 3Pt/CSBA-15 even achieves 81.5% C2H4 conversion and 71.6% CO2 yield after 20 h, exhibiting much more prominent catalytic performances than 3Pt/SBA-15. DFT calculations and in situ FTIR measurements confirm that small-sized Pt particles possess strong O2 affinity to promote O2 adsorption, and in situ formed hydrophobic carbon layers efficiently suppress competitive H2O adsorption. Such a unique one-step catalyst preparation method for regulating the size of metal particles and the hydrophobicity of catalysts can be perfectly utilized to develop simple and efficient hydrophobic catalysts applied in low-temperature oxidation of C2H4.

Enhanced moisture resistance and catalytic stability of ethylene oxidation at room temperature by the ultrasmall MnOx cluster/Pt hetero-junction

Ethylene elimination can effectively inhibit the rapid aging of fruits and vegetables in storage and transportation. Improving the low-temperature activity, moisture resistance, and stability of Pt based catalysts is a challenge for catalytic oxidation of ethylene which is an effective elimination method. Herein, we constructed ultrasmall MnOx cluster (< 1 nm) on Pt particles via an alloy in situ transformation strategy, which created a large number of MnOx/Pt interfaces. Among all of the samples, 1.89Pt2.20Mn/TiO2 showed the highest catalytic activity in the oxidation of ethylene at a space velocity of 20,000 mL/(g h): T50% = 34 oC and T90% = 43 oC, specific reaction rate at 35 oC = 33.0 µmol/(gPt s), and turnover frequency at 35 oC = 6.5 × 10–3 s−1. In addition, Pt2.20Mn/TiO2 also exhibited better water resistance and stability than Pt/TiO2. The results of XPS, H2O-TPD, C2H4-TPD, in situ DRIFTS, and H218O isotopic tracing characterization revealed that the MnOx/Pt interfacial sites accelerated desorption of CO2 and enhanced the activation of surface active oxygen species (O2 to O22−). Meanwhile, the numerous interfaces provide more active sites for ethylene adsorption and activation, reducing the inhibitory effect of adsorbed water on ethylene adsorption. It was concluded that the prohibited CO2 adsorption, and increased adsorbed oxygen species were responsible for the excellent catalytic performance and good stability of 1.89Pt2.20Mn/TiO2, while the more active sites for ethylene adsorption and activation were responsible for the good water resistance of 1.89Pt2.20Mn/TiO2.

Morphology-steered synthesis of Ce-MnO2 catalysts for catalytic oxidation of ethane at low temperature

Ce-MnO2 catalysts with nanosheets-stacked flower-like architecture were prepared by hydrothermal method, and Ce0.5Mn1 sample exhibited excellent catalytic performance for ethane combustion, with T90 at 310 °C. The apparent activation energy of the Ce0.5Mn1 sample (70.7 kJ mol−1) was comparatively lower than that of pure MnO2 (112.4 kJ mol−1). The formation of CeMn solid solution reduced the sizes of the Ce-MnO2 crystallites, affording higher SBET. Electron transfer and redistribution in the CeMn solid solution enhanced the activation of surface oxygen (OA) and generated more oxygen vacancies. The increasing OA species and highly mobile lattice oxygen boosted the oxidation of ethane. Also, the Ce0.5Mn1 catalyst exhibited enhanced H2O resistance with an ethane conversion over 95 % at 350 °C. Moreover, the morphologies of the CexMn1 catalysts were significantly influenced by Ce doping. Variations in Ce3+ amount significantly altered the thickness of the nanosheets, and the structure displayed more surface defects with considerable active sites. This work provides insights into the design of a promising MnO2-based catalyst for the mitigation of light alkanes.

Promotion Effects of Ce-Doping on Catalytic Oxidation of Ethane over Pt/CexTi1−xO2

The catalytic oxidation of VOCs is widely acknowledged as the most available technology to reduce air pollution. Among the catalysts for VOCs, 1 wt%-Pt/TiO2 catalysts using metal as a doping element have shown amazing potential in many fields. However, achieving high catalytic performance at relatively low temperatures based on the activation of molecules is still a formidable challenge owing to the catalytic activity being highly dependent on temperature. Here, the role of the rare earth metal Ce in the catalytic oxidation of ethane was studied by preparing Pt/CexTi1−xO2 (x = 0, 0.002, 0.005, 0.01, 0.02, and 0.05) catalysts. When the Ce/(Ce+Ti) molar ratio was 0.01, Pt/Ce0.01Ti0.99O2 achieved 90% ethane conversion at 436 °C. This reaction temperature is 15% lower than that for Pt/TiO2. The characterization results show that the doping of Ce caused lattice expansion of TiO2 and its distortion brought about by oxygen vacancies. Additionally, the appropriate amount of Ce-doping can alter the interaction between the active component Pt and the carrier TiO2, thereby improving the activity and concentration of the active surface lattice oxygen species of the catalyst. These results provide a foundation for the design of the catalytic oxidation of VOCs under mild operating conditions.

Surface-Modified CeO2-Octahedron-Supported Pt Nanoparticles as Ethylene Scavengers for Fruit Preservation

Catalytic oxidation of ethylene associated with the preservation of fruits and vegetables (F&V) at low temperatures remains challenging. To address this issue, CeO2-octahedron-supported Pt catalysts were synthesized and modified by capacitively coupled plasma for efficient catalytic oxidation of C2H4. After the plasma treatment, CeO2 with rich oxygen vacancies was created, which acted as a support to facilitate the regulation of the size and dispersion of Pt nanoparticles. Compared with Pt/pristine CeO2, the Pt/plasma-modified CeO2 catalyst (Pt/CeO2-P) showed significantly higher reactivity. More than 99.9% of ethylene conversion induced by Pt/CeO2-P could be sustained longer than 50 h at 25 °C, and 30 min even at 0 °C. Thus, Pt/CeO2 interface engineering by plasma modification technology is particularly promising for low-temperature catalytic oxidation of ethylene. Moreover, a comprehensive characterization was conducted to elucidate the reaction pathway and oxidation mechanism. From the preservation test using bananas as fruit samples, it was found that Pt/CeO2-P delayed postharvest deterioration and ripening of bananas due to the excellent ethylene scavenging effect created by the catalyst, thus demonstrating the great potential applications in F&V preservation.

Insights into coverage-affected selective catalytic oxidation of ethylene on Ag(111) from comprehensive microkinetic analyses

A full kinetic simulation under industrial conditions was conducted based on DFT coverage-dependent modeling.

Synchronously constructing the optimal redox-acidity of sulfate and RuOx Co-modified CeO2 for catalytic combustion of chlorinated VOCs

CeO2-based catalysts are highly active but easily deactivated for the catalytic combustion of chlorinated VOCs (CVOCs), and enhanced redox and acidity are also considered to be effective strategies. However, the screening of practicable modifiers and their preparation method to achieve the promotion and balancing of redox-acidity is still desired. In this work, sulfate and RuOx were simultaneously introduced into CeO2 by a simple co-precipitation method, and the optimal redox-acidity was constructed. The catalytic combustion of 1,2-dichloroethane (DCE) indicated that 2.5Ru-CeO2-S0.05 presented an outstanding oxidation activity and selectivity of chlorinated byproducts and superior cycle and long-term stability (at least 60 h at 280 °C), even in the presence of 5 % H2O. A series of control experiments, such as the introduction methods, the precursors and contents of Ru and sulfate, and their property characterization revealed that the bulk doping of Ru mainly contributed to the promoted activity and durability through more exposed Ce3+/4+ and oxygen vacancies and the rapid removal ability of the inorganic chlorine species via a semi-Deacon reaction pathway, as well as to the formation of chlorinated byproducts. Meanwhile, the synchronous introduction of sulfate as Brønsted acid sites efficiently inhibited these chlorinated byproducts, while its retained redox ability and the enhanced Lewis acid sites owing to the strong electron withdrawing of the sulfate also further promoted DCE oxidation. Moreover, 2.5Ru-CeO2-S0.05 showed a high activity and excellent durability for the catalytic oxidation of ethylene, vinyl chloride and their mixtures with 1,2-DCE. This work provided a demonstration for balancing the oxidation performance and acidity of CeO2-based catalysts, which contributed to the development of applicable catalysts for catalytic oxidation of CVOCs under actual working conditions.

Optimization of ethylene dichloride (EDC) and ethane concentrations to maximize catalytic ethylene oxide production rate and yield: Experimental study and modeling

Simultaneous optimization of EDC and ethane concentrations to maximize ethylene oxide production rate (rEO) over a commercial catalyst at 17.4 bar, 213–240 °C and in the GHSV range of 3000–5000 h−1 was done in this study. The feed composition and operating conditions were chosen similar to those in the industry, so that the findings are practical. EDC and ethane concentrations in the feed are merged into a practical parameter referred to as equivalent EDC (EDCeq) in this study which is indicative of the chlorinating power of the gas mixture. It was noticed that the higher the temperature, the higher the optimum EDCeq to maximize rEO. Although rEO had a decreasing trend versus EDCeq for 213 °C, it showed a maximum with EDCeq for 225 and 240 °C. While CO2 production rate (rCO2) monotonically decreased with EDCeq, EO selectivity experienced an upward trend with EDCeq, approaching a horizontal asymptote.

Simulación del proceso de producción de óxido de etileno en el simulador ChemCAD®

Ethylene oxide is an important industrial chemical compound used as an intermediate in the production of glycols and other plastics. In the present work, the process of ethylene oxide (EO) production from the catalytic oxidation of ethylene was simulated using the ChemCAD® simulator. Heat curves were obtained for each of the shell and tube heat exchangers used, while the flow rate and composition of the most important streams involved in the production process were determined. A sensitivity study was also carried out to establish the influence of a decrease in the feed temperature of the wash water to the absorbers on the amount of EO to be obtained in the distillation column. 22,163.5 kg/h of EO is obtained from the top of the distillation column with a purity of 98.29 %. The wash water should be fed to the absorbers at a temperature of 5 ºC to maximise the amount of EO to be obtained in the distillation column.

Auger- and photoelectron coincidences of molecular O2 adsorbed on Ag(111)

The oxygen on Ag(111) system has been investigated with Auger electron–photoelectron coincidence spectroscopy (APECS). The coincidence spectra between O 1s core level photoelectrons and O KLL Auger electrons have been studied together with Ag3d/AgM4,5NN coincidences. We also describe the electron–electron coincidence spectrometer setup, CoESCA, consisting of two angle resolved time-of-flight spectrometers at a synchrotron light source. Contributions from molecular oxygen and chemisorbed oxygen are assigned using the coincidence data, conclusions are drawn primarily from the O 1s/O KLL data. The data acquisition and treatment procedure are also outlined. The chemisorbed oxygen species observed are relevant for the catalytic ethylene oxidation.

Insights into Coverage-Affected Selective Catalytic Oxidation of Ethylene on Ag(111) from Comprehensive Microkinetical Analyses

Insights into Coverage-Affected Selective Catalytic Oxidation of Ethylene on Ag(111) from Comprehensive Microkinetical Analyses

Catalytic Oxidation of Ethylene in Solutions of Palladium(II) Cationic Complexes in Binary and Ternary Aqueous Organic Solvents

Catalytic Oxidation of Ethylene in Solutions of Palladium(II) Cationic Complexes in Binary and Ternary Aqueous Organic Solvents

Effect of the Oxidation Degree of a Nickel Foil Surface on Its Catalytic Activity in the Reaction of Ethylene Oxidation

The effect of the oxidation degree of a nickel foil surface on the rate of catalytic oxidation of ethylene was studied by a pulse method at 600 and 700°C. It was shown that a reduced metallic surface demonstrated a high activity in partial ethylene oxidation, whereas a partially oxidized surface with an oxidation degree of ~24 formal O2 monolayers, in the total oxidation of C2H4. A SEM investigation has revealed that the oxidized surface was partially coated with nickel oxide nanocrystals. A further increase in the surface oxidation degree led to a continuous coverage of the Ni surface with oxide crystals and a dramatic decrease of catalytic activity. In addition, a low maximum of total ethylene oxidation was observed at 700°C in the range of surface oxidation degree of 95–135 O2 monolayers.

Catalytic ethylene oxidation by Cu–Au core–shell nanoclusters: a computational study

We have studied the catalytic activity of Cu–Au core–shell nanoclusters toward the ethylene oxidation based on periodic first-principles computations. The adsorption behaviors of O2 and C2H4 on the Cu–Au core–shell nanoclusters as well as the C2H4–O2 coadsorption were examined. We found that O2 and C2H4 are preferably bound at bridge (B) and top (T) sites with adsorption energies of − 2.09 and − 0.65 eV for Cu32–Au6 nanocluster and − 1.06 and − 0.62 eV for Au32–Cu6 nanocluster. The oxidation reaction occurs via the Langmuir–Hinshelwood (LH) mechanism which has been illustrated by employing the climbing image nudged elastic band method. The overall reaction of O2 + C2H4 → epoxide + O is exothermic by ~ 3.31 eV for Cu32–Au6 nanocluster and 2.17–2.26 eV for Au32–Cu6 nanocluster, while those are 3.76–4.24 eV and 2.91–2.73 eV for the generation of acetaldehyde. The Cu–Au core–shell nanoclusters, especially the hexagonal fcc(111)-like face of Cu32–Au6 and the square fcc(100)-like face of Au32–Cu6 core–shell nanoclusters, exhibit better catalytic properties and selectivity for the ethylene oxidation compared with the Cu and Au nanoparticles.

Kinetic conjugation effects in oxidation of C1-C2 hydrocarbons: Experiment and modeling

Oxidation of individual C1-C2 alkanes and their mixture (CH4:C2H6 = 8:1) was studied in an empty flow reactor and in the presence of two model catalysts used for oxidative coupling of methane (OCM) and oxidative transformations of C2+ alkanes, namely NaWMn/SiO2 and Ca-La/Al2O3. Ethane is much more reactive in homogeneous oxidation due to a high rate of free radical chain branching. Methane inhibits both homogeneous and catalytic oxidation of ethane, while ethane accelerates the conversion of methane. Methane reactivity is higher over the Ca-La/Al2O3 catalyst. In the presence of NaWMn/SiO2 ethane reacts faster, and the ‘conversion vs. contact time’ kinetic curves preserve an S-shape character typical for homogeneous branching chain processes. The observed features were rationalized using the numerical simulations in the framework of heterogeneous-homogeneous kinetic scheme that accounted both free-radical gas phase processes and reactions of molecular and radical species with catalytic active sites. It was shown that typical OCM catalysts play a dual role: they activate hydrocarbons by capturing H-atoms from C–H bonds and also efficiently terminate chain reactions by trapping free radicals. Consequently, over the catalyst that is more active in methane oxidation (Ca-La/Al2O3) ethane reacts slower due to the elimination of free radical chain branching and development. During the oxidation of ethane, methane – as an efficient radical scavenger – improves the selectivity to ethylene due to the inhibition of its secondary transformations (mainly to CO via HCO radicals).

Site-Selective Supramolecular Complexation Activates Catalytic Ethane Oxidation by a Nitrido-Bridged Iron Porphyrinoid Dimer.

Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 35+ , which is connected through a fourfold rotaxane, was prepared. Heterodimer 35+ catalyzed ethane oxidation in the presence of H2 O2 at a relatively low temperature. The site-selective complexation of 35+ with an additional anionic porphyrin (TPPS4- ) through π-π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 35+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS4- to 35+ enhanced the catalytic activity.

Catalytic Oxidation of Ethane to Carboxylic Acids in the Liquid Phase at Near Room Temperature at Ambient Pressure

Chemical transformation of shale gas components under mild conditions is ideal for utilizing the shale gas resource to produce high-value intermediates of chemical industries and fuel feedstocks of energy industries. Here we report that single Rh atom sites, Rh1O5 anchored in micropores of HZSM-5, can catalyze oxidation of ethane by hydrogen peroxide in aqueous solution to form acetic acid and formic acid at a temperature ≤ 50 °C at a pressure of ethane at 1.5 bar. Conversion of 1.5 bar of ethane to carboxylic acids at 50 °C in a Parr rector reaches 37% within 2 h. Acetic acid and formic acid are formed through two parallel reaction pathways with apparent activation barriers of 32.5 and 35.5 kJ/mol in the temperature range of 50–72 °C, respectively. Turnover rates for forming carboxylic acids are 0.060 acetic acid molecules on each Rh1O5 site per second (216 mol of acetic acid per mol Rh per hour) and 0.127 formic acid molecules on each Rh1O5 site per second (457 mol of formic acid per mol of Rh per hour)...

In Situ Tuning of Catalytic Activity by Thermoelectric Effect for Ethylene Oxidation

The use of the thermoelectric material BiCuSeO as a support and promoter for catalytic ethylene oxidation is reported here. The catalytic activity of a continuous and noncontinuous Pt catalyst supported on BiCuSeO was observed to be promoted significantly by an in situ generated thermoelectric Seebeck voltage by the temperature difference across the material. It has also been shown that this promotion of catalysis by the thermoelectric effect enabled the material BiCuSeO itself to be highly catalytically active for ethylene oxidation. A linear relationship between the logarithm of the reaction rate and the thermoelectric Seebeck voltage was also observed. The thermoelectric promotion of catalysis is attributed to the change of work function of the catalyst surface, accompanied by a charge transfer from the bulk to the surface that is caused by the thermoelectric effect.