Oxidation Of Ethylene Research Articles

Oxidative Deprotection of Benzyl Protecting Groups for Alcohols by an Electronically Tuned Nitroxyl-Radical Catalyst.

The oxidative deprotection of benzyl (Bn) groups using nitroxyl-radical catalyst 1 and co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA) is reported. This catalyst is highly active for the oxidation of benzylic ethers because of the electronic tuning on account of the electron-withdrawing ester groups next to the catalytically active center. This catalytic system promotes deprotections at ambient temperature and has a broad substrate scope, including substrates possessing hydrogenation-sensitive functional groups, while the deprotection hardly proceeds when using well-known nitroxyl-radical catalysts such as 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO). The 1/PIFA system also promotes the deprotection of several benzylic protecting groups, including 2-naphthylmethyl (NAP) and 4-methylbenzyl (MBn) groups. Catalyst 1 was also effective for the direct synthesis of ketones and aldehydes from Bn ethers via deprotected alcohols using an excess of the co-oxidant PIFA.

One‐pot synthesis of V doped mesoporous SiO2 catalysts for selective oxidation of ethane and propane

AbstractA series of vanadium‐doped mesoporous SiO2 catalysts were prepared using a one‐pot emulsion method. The effects of VOx species with different structures on C−H bond activation and product selectivity in ethane and propane selective oxidation were investigated using X‐ray diffraction (XRD), N2 adsorption‐desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, ultraviolet‐visible diffuse reflectance spectroscopy (UV‐Vis DRS), hydrogen temperature programmed reduction (H2‐TPR), and ammonia temperature programmed desorption (NH3‐TPD) characterizations. The results revealed that the highly dispersed isolated tetrahedral VOx species on the catalyst gradually polymerized into highly dispersed oligomeric VOx species with the increased V loading. The former is beneficial for the formation of olefins and total aldehydes during the selective oxidation of propane. Oligomeric VOx species are conducive to improving the selectivity of ethylene and acetaldehyde in the selective oxidation of ethane. The highest catalytic performances for selective oxidation of ethane and propane were obtained at a temperature of 650 °C. The conversion of ethane was 41.6 %, with a corresponding yield of ethylene and acetaldehyde of 23.6 % over a 0.5 V−SiO2 catalyst. In contrast, the propane conversion was 61.5 %, with a corresponding total yield of olefins and aldehydes of 41.3 % over a 1.0 V−SiO2 catalyst.

Using cerium modified ferric oxide as oxygen carrier for enhancement of fuel efficiency

Using oxygen carrier to relieve uneven mixing of fuel and air under harsh conditions (high temperature and short residence time) is a promising strategy to improve fuel efficiency. In this paper, a range of cerium modified ferric oxide oxygen carriers with excellent redox capability and stability was fabricated to investigate the ethylene rapid oxidation performance and the gas–solid surface reaction of ethylene and iron oxide was studied with density functional theory. The experimental results show that the oxygen carrier with the mole ratio of ferrum: cerium is 9:1 performed the best ethylene oxidation characteristic, because the addition of cerium improved oxygen vacancy capacity to enhance the oxidation for ethylene and its pyrolysis products, which was also confirmed with density functional theory study. Due to the role of both, the ethylene and its pyrolysis products were converted into carbon dioxide and water quickly and effectively (carbon dioxide yield >92%).

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.

Copper-manganese oxide catalysts prepared by solution combustion synthesis for total oxidation of VOCs

A set of Cu-Mn oxides was prepared through the simple and effective solution combustion synthesis method by varying the relative amount of copper and manganese. The physico-chemical properties of the samples were investigated through complementary techniques such as N2 physisorption at − 196 °C, XRD, HR-TEM, Raman spectroscopy, temperature programmed analyses (H2-TPR, O2-TPD, and NH3-TPD), and XPS. The prepared catalysts were tested for the total oxidation of volatile organic compounds (ethylene, propylene, and toluene). The best performances, in terms of total VOC oxidation, were achieved with a copper content ranging from 15 at% to 45 at%. The catalytic test outcomes demonstrate the beneficial effect of acidic sites, oxygen mobility, and redox ability. In particular, ethylene oxidation is mainly favored by oxygen vacancies and redox properties, while propylene and toluene oxidation is mostly enhanced by acidic sites. All the catalysts prepared can totally oxidize the examined pollutants examined below 310 °C. Moreover, the binary oxides exhibit good catalytic stability over a time-on-stream of 7 h and low water vapor inhibition (5 vol% H2O in the gas stream).

A Comparison of Ambient Air Ethylene Oxide Modeling Estimates from Facility Stack and Fugitive Emissions to Canister-Based Ambient Air Measurements in Salt Lake City

Ethylene oxide (EtO) is a colorless, flammable gas at room temperature produced by the catalytic oxidation of ethylene. EtO is widely used by medical sterilization facilities to clean medical supplies and equipment. Recent epidemiological studies showed that EtO is a more potent carcinogen than previously documented, leading the Environmental Protection Agency (EPA) to update, in December 2016, the inhalation unit risk estimate for EtO. This resulted in the identification of EtO as a potential health concern in several areas across the US, including the state of Utah. The geography surrounding Salt Lake Valley creates a bowl, which is ideal for collecting air pollution emissions. The region often experiences inversion episodes which inhibit vertical mixing and cause an accumulation of air pollutants, leading to unhealthy pollution levels. Using the EPA’s dispersion modeling software, AERMOD, this study estimated EtO concentrations through facility stack and fugitive emissions modeling results. These values were compared with those of canister-based concentrations from ambient air samples taken near a medical device sterilization facility in Salt Lake Valley. Stainless steel whole-air passivated canisters were used to collect 24 h ambient concentration samples of EtO. Eight locations surrounding a Salt Lake Valley medical device sterilization facility and four background sites were chosen to measure the ambient concentrations. Accounting for potential atmospheric impacts on EtO, measurements were sampled in winter 2022 (January–March) and summer 2022 (July–September). The modeled EtO concentrations were adjusted to account for background values associated with the winter or summer data. Then, the two methodologies were compared using a Wilcoxon signed-ranked paired test. The statistical analysis resulted in six of the eight sample locations surrounding the sterilization facility being significantly different when comparing the canister-based measurements of ambient EtO to modeled estimates. Canister-based measurements taken at sites one, three, and four were statistically greater than the modeled estimates, while sites two, five, and seven were statistically less than the modeled estimates. Also, the summer background value calculated was almost 2.5 times greater than the winter one. The results do not suggest whether one method is more or less conservative than the other. In conclusion, the five of the closest sites and site seven were statistically different when comparing measured and modeled ambient concentrations of EtO. The comparison results do not clearly indicate if a correction factor could be derived for future human exposure to cancer risk assessment modeling. However, it is reasonable that the closer to the sterilization facility, the more total EtO exposure will be realized.

Ethylene Electrooxidation to 2-Chloroethanol in Acidic Seawater with Natural Chloride Participation.

Ethylene oxidation to oxygenates via electrocatalysis is practically promising because of less energy input and CO2 output compared with traditional thermal catalysis. However, current ethylene electrooxidation reaction (EOR) is limited to alkaline and neutral electrolytes to produce acetaldehyde and ethylene glycol, significantly limiting cell energy efficiency. Here, we report for the first time an EOR to 2-chloroethanol product in a strongly acidic environment with natural seawater as an electrolyte. We demonstrate a 2-chloroethanol Faradaic efficiency (FE) of ∼70% with a low electrical energy consumption of ∼1.52 × 10-3 kWh g-1 over a commercial Pd catalyst. We establish a mechanism to evidence that 2-chloroethanol is produced at low potentials via direct interaction of adsorbed chloride anions (*Cl) with ethylene reactant because of the high coverage of *Cl during reaction. Importantly, this differs from the accepted multiple step mechanism of subsequent chlorine oxidation and ethylene chlorination reactions at high potentials. With highly active Cl- participation, the production rate for 2-chloroethanol in acidic seawater is a high 26.3 g m-2 h-1 at 1.6 V operation. Significantly, we show that this is 223 times greater than that for ethylene glycol generation in acidic freshwater. We demonstrate chloride-participated EOR in a proton exchange membrane electrolyzer that exhibits a 68% FE for 2-chloroethanol at 2.2 V operation in acidic seawater. This new understanding can be used for designing selective anode oxidation reactions in seawater under mild conditions.

SARS CoV-2 infection screening via the exhaled breath fingerprint obtained by FTIR spectroscopic gas-phase analysis. A proof of concept

The COVID-19 pandemic remains a global challenge now with the long-COVID arising. Mitigation measures focused on case counting, assessment and determination of variants and their likely targets of infection and transmission, the pursuit of drug treatments, use and enhancement of masks, social distancing, vaccination, post-infection rehabilitation, and mass screening. The latter is of utmost importance given the current scenario of infections, reinfections, and long-term health effects. Research on screening platforms has been developed to provide more sensitive, specific, and reliable tests that are accessible to the entire population and can be used to assess the prognosis of the disease as well as the subsequent health follow-up of patients with sequelae of COVID-19. Therefore, the aim of the present study was the simulation of exhaled breath of COVID-19 patients by evaluation of three identified COVID-19 indicator breath biomarkers (acetone (ACE), acetaldehyde (ACH) and nitric oxide (NO)) by gas-phase infrared spectroscopy as a proof-of-concept principle for the detection of infected patients’ exhaled breath fingerprint and subsequent follow-up. The specific fingerprints of each of the compounds and the overall fingerprint were obtained. The synthetic exhaled breath evaluation concept revealed a linearity of r = 0.99 for all compounds, and LODs of 6.42, 13.81, 9.22 ppm, and LOQs of 42.26, 52.57, 69.23 ppm for NO, ACE, and ACH, respectively. This study proves the fundamental feasibility of gas-phase infrared spectroscopy for fingerprinting lung damage biomarkers in exhaled breath of patients with COVID-19. This analysis would allow faster and cheaper screening and follow-up of infected individuals, which could improve mass screening in POC settings.

An experimental and kinetic modeling study on low-temperature oxidation of gasoline and diesel/polyoxymethylene dimethyl ether (OME3) blends

In this work, the low-temperature oxidation of polyoxymethylene dimethyl ether (OME3) with multi-component surrogates for diesel (DS:60%n-heptane/20%cyclohexane/20%toluene) and gasoline (GS:20%n-heptane/60%iso-octane/20%toluene) blends was investigated respectively using a jet-stirred reactor (JSR) with a temperature range of 500–950 K, constant fuel fraction of 0.008, residence time (τ) of 2 s and near atmospheric pressure. Two detailed multi-component kinetic mechanisms were established to describe the low-temperature oxidation characteristics and the interaction of blended fuels. Generally, the oxidation process of highly-reactive OME3 and n-heptane is inhibited, while that of inactive fuels, including iso-octane, cyclohexane and toluene, are triggered and enhanced in various degrees in the blends. The OH radical acts as a bridge between high and low reactivity components. It is of interest that n-heptane reveals a quite different low-temperature oxidation behavior in diesel (DS) and gasoline (GS) surrogate respectively. In GS, the low-temperature oxidation of n-heptane is significantly inhibited, while in DS, the inhibition is mild, mainly due to the much different low-temperature oxidation characteristics of iso-octane and cyclohexane. As for OME3, it mainly improves the reactivity of the blends in the negative temperature coefficient (NTC) process. As for low-reactivity fuels of iso-octane and toluene, their low-temperature oxidations are completely triggered and dominated by highly-reactive fuels due to their weak OH build-up ability. On the contrary, when the low-temperature oxidation of cyclohexane is triggered, its self-enhancement also plays a crucial role in addition to the promoting effect from highly-reactive fuels. Therefore, cyclohexane reveals a promoting-ignition effect on the blended fuels, while iso-octane and toluene act as an inhibiting-ignition factor in blends.

The secretome of Agaricus bisporus: Temporal dynamics of plant polysaccharides and lignin degradation

Despite substantial lignocellulose conversion during mycelial growth, previous transcriptome and proteome studies have not yet revealed how secretomes from the edible mushroom Agaricus bisporus develop and whether they modify lignin models invitro. To clarify these aspects, A.bisporus secretomes collected throughout a 15-day industrial substrate production and from axenic lab-cultures were subjected to proteomics, and tested on polysaccharides and lignin models. Secretomes (day 6-15) comprised A.bisporus endo-acting and substituent-removing glycoside hydrolases, whereas β-xylosidase and glucosidase activities gradually decreased. Laccases appeared from day 6 onwards. From day 10 onwards, many oxidoreductases were found, with numerous multicopper oxidases (MCO), aryl alcohol oxidases (AAO), glyoxal oxidases (GLOX), a manganese peroxidase (MnP), and unspecific peroxygenases (UPO). Secretomes modified dimeric lignin models, thereby catalyzing syringylglycerol-β-guaiacyl ether (SBG) cleavage, guaiacylglycerol-β-guaiacyl ether (GBG) polymerization, and non-phenolic veratrylglycerol-β-guaiacyl ether (VBG) oxidation. We explored A.bisporus secretomes and insights obtained can help to better understand biomass valorization.

Skeletal kinetic mechanism for predicting formation of non-fuel hydrocarbons and soot in ethylene flames – A CFD approach

Since existing reduced mechanisms of ethylene oxidation are either too large or lack of sufficient chemical reactions to describe aromatics formation, the study aims at developing a skeletal mechanism with extended predictive capability and lowered computational cost in computational fluid dynamics modeling of ethylene combustion. The newly assembled and refined kinetic mechanism composed of 664 species and 3582 reactions is minimized to 79 species and 538 reactions without empirically adjusting kinetic parameters. In the 1-D simulation for a premixed flame of ethylene, the ethylene-PAH mechanism generally well predicts experimental profiles of five hydrocarbons and nine aromatics. Integrated into a 2-D axisymmetric laminar finite-rate model, the ethylene-PAH mechanism reproduces experimental data of seven C2–C5 hydrocarbons, five aromatic hydrocarbons and soot in a diffusion flame of ethylene. In comparison with the 158-species (Narayanaswamy) mechanism, the newly proposed ethylene mechanism leads to a speedup of approximately 5.5 times in the 2-D laminar diffusion flame simulation and improved accuracy for predicting species formation in both premixed and nonpremixed flames. Moreover, we unveil the correlation between reaction pathways and intermediate formation from ethylene oxidation at the low temperature regime.

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.

Highly Sensitive Ethylene Sensors Based on Ultrafine Pd Nanoparticles-Decorated Porous ZnO Nanosheets and Their Application in Fruit Ripeness Detection

Ethylene is the most common ripening phytohormone in fruits, and excess ethylene can overripen the fruit. However, the in-field detection of ethylene is still limited. In this work, ultrafine Pd nanoparticles-decorated porous ZnO nanosheets (UPNP ZnO nanosheets) were conveniently synthesized through a facile solvent reduction method. The UPNP ZnO nanosheets were characterized using scanning electron microscopy, transmission electron microscopy, energy dispersive spectrum, X-ray diffraction and X-ray photoelectron spectroscopy. The ZnO nanosheets were uniformly coated with Pd nanoparticles. The size of the Pd nanoparticle was very small, with a diameter of approximately 2 nm. Due to the unique structure of the porous ZnO nanosheets and the excellent catalytic properties of the ultrafine Pd nanoparticles, the as-prepared samples showed very high sensing performance in ethylene detection. The lowest detection concentration was 10 ppb, which is the lowest detection limit to our knowledge. It has been proved that the decoration of ultrafine Pd nanoparticles can largely increase the relative percentage of chemisorbed oxygen and deficient oxygen, which are benefits for ethylene oxidation, and actually accelerate the process of the sensing reaction. Furthermore, the UPNP ZnO nanosheets can even be applied in fruit maturity detection. Using mangos as an example, our experiment revealed that the response of UPNP ZnO nanosheets to mangos at different maturity stages was quite different. This result suggests that our product has broad application prospects in monitoring fruit ripening stage.

Theoretical study of H-abstraction reactions of di-n-propyl ether oxidation by H, CH3, HO2 and OH radicals

The H-abstraction reactions from di-n-propyl ether (DPE) by radicals are significant in the DPE oxidation process. However, corresponding rate constants only rely on either analogy from alcohols or estimation from alkanes due to the lack of experimental and theoretical studies. In current work, thermochemistry and kinetics of DPE oxidation by the H, CH3, HO2 and OH radicals have been studied using the composite methods (CBS-QB3 and G4). Four H-abstraction reaction systems have been discussed, all of them occur through energy barriers of −5.4–20.5 kcal/mol. The energy barriers increase in the order α < β < γ at CBS-QB3 and G4 levels. The hydrogen-bond reactant complexes, RCβHO2, RCαOH, RCβOH and RCγOH, are identified in the entrance channel for the H-abstraction by HO2 and OH radicals. The rate constants for target reactions are calculated with the transition state theory and canonical variational transition state theory over a broad temperature range of 400–1400 K. Rate constants and branching ratios show that the H-abstraction reaction from Cα is the dominant reaction over the investigated temperature range. The total rate constants of the DPE + OH system have been fitted as follows: k = 1105 × T 3.185 exp(1720/T) (cm3 mol−1 s−1). The G4 data well reproduce the available experimental rate constant for DPE + OH system. The rate constants of H-abstraction reactions in the kinetic model of Serinyel et al. [Fuel 263 (2020) 116554] are modified based on the current calculated results to obtain a revised model. A validation for the revised model against the jet-stirred reactor (JSR) measurements from the literature are also provided, and the modified mechanism shows good performances to predict the JSR data. Reaction pathway and sensitivity analyses are performed to identify the fuel consumption paths and key reactions in oxidation process of DPE.

Diverse Site-Selective Transformation of Benzylic and Allylic Silyl Ethers via Organocatalytic Oxidation

We herein report nitroxyl-radical catalyst 1a, which recognizes the electronic properties of silyl ethers, thus enabling selective oxidation of benzylic and allylic silyl ethers, despite steric factors. A subsequent one-pot reduction accomplishes the formal deprotection to the corresponding benzylic and allylic alcohols. This catalytic system allows the direct oxidative desymmetrization of bis-benzylic and bis-allylic silyl ethers to access synthetically useful monoprotected conjugated aldehydes, which can be applied to one-pot enantioselective transformations. Mechanistic studies revealed that the highly electron-accepting oxoammonium species from 1a as well as the trifluoroacetate form of phenyl iodonium bis(trifluoroacetate) (PIFA) play key roles for the selectivity-determining hydride transfer step.

Kinetic and thermodynamic studies on direct synthesis of methyl methacrylate from methyl propionate and methanol catalyzed by highly efficient cobalt complex at mild conditions

Methyl methacrylate (MMA) typically produced from the petroleum-based ethylene or isobutene selective oxidation route is a significantly important chemical widely used in industrial manufacture. Herein, an innovative and highly efficient liquid-phase catalytic system, cobalt complex catalyzed O2-interrupted hydrogen borrowing pathways, was developed for direct synthesis of MMA from methyl propionate and methanol at mild conditions, considering the problems of poor selectivity, rapid catalyst deactivation, and formaldehyde polymerization existed in one-step aldol reaction of methyl propionate with formaldehyde at 350–380 °C. The yield and selectivity of MMA could reach up to 50.2% and 81.8% at 60 °C and 1 atm. Thermodynamic calculations and analysis for this novel transformative process were conducted to confirm the feasibility and reasonability for MMA production at low temperature (below 100 °C). On the basis of the reaction networks proposed according to the experimentally detected products, studies on the kinetic informatics of this new process were conducted. The formaldehyde oxidation, aldol condensation of methyl/t-butyl propionate with formaldehyde and transesterification of t-butyl propionate/methacrylate with methanol are first-order dependent on their reactant concentrations. While the methanol dehydrogenation and transesterification of methyl propionate/methacrylate with t-BuOK are first-order dependent on the concentration of only methanol and t-BuOK. With the understanding of kinetic behavior of these reaction steps composed, the global kinetic model was established to describe this catalytic system and the corresponding parameters including pre-exponential factor and activation energy were calculated. The oxidative dehydrogenation of methanol to formaldehyde, with the highest activation energy of 84 kJ/mol, was the kinetic-relevant step, while the aldol condensation of methyl propionate with formaldehyde showed the lowest energy of 36 kJ/mol.

Investigating the Association Reactions of HOCH2CO and HOCHCHO with O2: A Quantum Computational and Master Equation Study

Glycolaldehyde, HOCH2CHO, is an important multifunctional atmospheric trace gas formed in the oxidation of ethylene and isoprene and emitted directly from burning biomass. The initial step in the atmospheric photooxidation of HOCH2CHO yields HOCH2CO and HOCHCHO radicals; both of these radicals react rapidly with O2 in the troposphere. This study presents a comprehensive theoretical investigation of the HOCH2CO + O2 and HOCHCHO + O2 reactions using high-level quantum chemical calculations and energy-grained master equation simulations. The HOCH2CO + O2 reaction results in the formation of a HOCH2C(O)O2 radical, while the HOCHCHO + O2 reaction yields (HCO)2 + HO2. Density functional theory calculations have identified two open unimolecular pathways associated with the HOCH2C(O)O2 radical that yield HCOCOOH + OH or HCHO + CO2 + OH products; the former novel bimolecular product pathway has not been previously reported in the literature. Master equation simulations based on the potential energy surface calculated here for the HOCH2CO + O2 recombination reaction support experimental product yield data from the literature and indicate that, even at total pressures of 1 atm, the HOCH2CO + O2 reaction yields ∼11% OH at 298 K.

Ethylene Oxide Catalysis Under Commercial Conditions – A Guide for Researchers

AbstractSelective oxidation of ethylene to ethylene oxide (EO) is performed industrially over catalysts comprised of silver particles supported on α‐Al2O3. In addition to various oxy‐anion and alkali promotors, alkyl chloride species (“chloride moderators”) are continuously introduced into commercial reactors. The effect and usage of chloride moderators is a key requirement for industrial ethylene epoxidation catalysts to reach optimal selectivity. While not an exhaustive review, the aim of this perspective is to provide guidance to academic researchers on the operation of EO catalysts under commercially relevant conditions with particular focus on the importance of performance optimization.

Extremely Low Temperatures for the Synthesis of Ethylene Oxide

The partial oxidation of ethylene in a methane atmosphere by pure oxygen is the most important industrial process for the synthesis of ethylene oxide. However, due to the high reactivity and exothermicity of the reaction system, the overall production is limited by kinetic and safety issues. The shift toward mild operative conditions can support the management of undesirable side reactions, enhancing the performance of the whole process. In the future, the direct use of liquefied ethylene and oxygen-enriched air, a low-cost waste in membrane-based nitrogen production, can provide convenient sources for heat removal as well as promote the use of innovative and more sustainable solutions. This work is focused on the experimental and numerical characterization of the oxidation of ethylene/methane/nitrogen/oxygen mixtures at different operative conditions, including extremely low temperatures, and oxidant compositions. To this aim, the laminar burning velocity and flammability limits were first measured utilizing the heat flux burner and compared with detailed kinetic mechanisms and experiments retrieved from the current literature. The reported data were adopted to identify the operational limits for innovative processes, paving the way to unlocking the potential of innovative chemistry at extreme conditions. Eventually, key performance indicators accounting for kinetic and safety aspects were defined to identify the most sustainable and convenient operative conditions.

Platinum nanoparticles supported on dendritic mesoporous silica nanoparticles with tunable size as ethylene scavengers for food preservation

Platinum-loaded dendritic mesoporous silica catalysts (Pt/DMS) with the size controlled by changing the molar ratio of NaSal/CTAB (φ) were successfully prepared using an incipient impregnating method. The resulting catalysts with high specific surface areas and distinctive central-radial pore channels exhibited excellent ethylene catalytic oxidation at low temperatures, enabling the complete ethylene conversion at 25 °C for 60 h and even at 0 °C for 200 min. The φ value plays an important role in controlling the DMS support structure and Pt activity. The high efficiency of low-temperature ethylene oxidation and long-term stability for Pt/DMS are attributed to high Pt dispersion, small Pt size, high Pt0 content and the rapid CO oxidation process. As an ethylene scavenger, Pt/DMS delayed the postharvest decay, deterioration, and storage quality loss of bananas and avocados, demonstrating the significant potential of as-prepared catalysts in the applications associated with fruit and vegetable (F&V) preservation.