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Results for “Ethylene oxidation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Mechanism of Chlorine-Mediated Electrochemical Ethylene Oxidation in Saline Water

Chlorine as a redox mediator allows for the selective oxidation of ethylene to 2-chloroethanol, which converts to ethylene oxide in alkaline aqueous electrolyte. This strategy utilizes abundant saline water as an electrolyte and source of oxygen atoms for functionalization. We present a mechanistic study of ethylene oxidation in saline water using cobalt oxide nanoparticle catalysts. Electrochemical kinetic analysis and in situ X-ray absorption spectroscopy suggest that the resting state of the catalyst and the rate-determining step differ for the chlorine evolution reaction in the presence and absence of ethylene. In 0.6 M NaCl pH 8 electrolyte, which resembles seawater, the average current density was ~60 mA/cm 2 with a Faradaic efficiency of ~41% toward ethylene functionalization. The use of synthetic and natural seawater achieved Faradaic efficiencies above 70%, while the partial current toward the product remained invariant. Further conversion of the initial product 2-chloroethanol into ethylene glycol was also demonstrated. Here, we present a broader vision of harnessing saline water in electrochemical functionalization of organic molecules and coproduction of hydrogen.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Solid Electrolytes for Li–S Batteries: Solid Solutions of Poly(ethylene oxide) with Li x PON- and Li x SiPON-Based Polymers

We report here efforts to synthesize free-standing, dry polymer electrolytes that exhibit superior ionic conductivities at ambient for Li–S batteries. Co-dissolution of poly(ethylene oxide) (PEO) (M n 900k) with Li x PON and Li x SiPON polymer systems at a ratio of approximately 3:2 followed by casting provides transparent, solid-solution films 25–50 μm thick, lowering PEO crystallinity, and providing measured impedance values of 0.1–2.8 × 10 –3 S/cm at ambient. These values are much higher than simple PEO/Li + salt systems. These solid-solution polymer electrolytes (PEs) are (1) thermally stable to 100 °C; (2) offer activation energies of 0.2–0.5 eV; (3) suppress dendrite formation; and (4) enable the use of lithium anodes at current densities as high as 3.5 mAh/cm 2 . Here, galvanostatic cycling of SPAN/PEs/Li cell (SPAN = sulfurized, carbonized polyacrylonitrile) shows discharge capacities of 1000 mAh/g sulfur at 0.25C and 800 mAh/g sulfur at 1C with high coulumbic efficiency over 100 cycles.

25 ENERGY STORAGE↗
DOE OSTI2022

High voltage stable cycling of all-solid-state lithium metal batteries enabled by top-down direct fluorinated poly (ethylene oxide)-based electrolytes

Poly (ethylene oxide) (PEO)-based solid-state polymer electrolytes (SPEs) show prospects in all-solid-state lithium metal batteries. However, they suffer from low ionic conductivity at room temperature and interfacial instability with high voltage cathodes for long-term cycling. In this work, top-down fluorinated PEOs (F-PEOs) for the all-solid-state electrolytes, which are scalable and cost-effective, are developed to improve the battery performance. We demonstrate, that by enhancing the disordering of the F-PEO matrix, the SPE achieves a maximum Li + conductivity of 1.1 x 10 -4 S cm -1 at 40 °C, which is 20 times higher than the baseline. By forming robust cathode/SPE and Li/SPE interfaces, the F-PEO-based SPEs demonstrate stable cycling in the LiFePO 4 /Li and LiNi 0·8 Mn 0·1 Co 0·1 O 2 /Li (3-4.4 V, 500 cycles, capacity retention of 91.6%) based all-solid-state batteries at 40 °C. Therefore, our work highlights the significance of "disordering engineering" for energy storage materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1976

Photoionization and ion cyclotron resonance studies of the ion chemistry of ethylene oxide

The formation of the ethylene oxide molecular ion and its subsequent ion-molecule reactions leading to the products C2H5O(+) and C3H5O(+) have been studied using time-resolved photoionization mass spectroscopy, ion cyclotron resonance spectroscopy, and photoelectron spectroscopy. An examination of the effects of internal energy on reactivity shows that the ratio of C3H5O(+) to C2H5O(+) increases by an order of magnitude with a single quantum of vibrational energy. The formation of (C2H4O/+/)-asterisk in a collision-induced isomerization is found which yields a ring-opened structure by C-C bond cleavage. The relaxed ring-opened C2H4O(+) ion reacts with neutral ethylene oxide by CH2(+) transfer to yield an intermediate product ion C3H6O(+) which gives C3H5O(+) by loss of H.

Corderman, R. R.↗
NASA NTRS1972

Contamination control by use of ethylene oxide

The uses of ethylene oxide as a decontaminating agent for planetary quarantine related applications are reported. Aspects discussed include: applications and limitations, chemical and physical properties, germicidal activity, methods of applications, and effects on personnel.

Stroud, R. H.↗
NASA NTRS1998

Abundances of ethylene oxide and acetaldehyde in hot molecular cloud cores

We have searched for millimetre-wave line emission from ethylene oxide (c-C2H4O) and its structural isomer acetaldehyde (CH3CHO) in 11 molecular clouds using SEST. Ethylene oxide and acetaldehyde were detected through multiple lines in the hot cores NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2. Acetaldehyde was also detected towards G10.47+0.03, G322.2+0.6, and Orion 3'N, and one ethylene oxide line was tentatively detected in G10.47+0.03. Column densities and rotational excitation temperatures were derived using a procedure which fits the observed line intensifies by finding the minimum chi 2-value. The resulting rotational excitation temperatures of ethylene oxide and acetaldehyde are in the range 16-38 K, indicating that these species are excited in the outer, cooler parts of the hot cores or that the excitation is significantly subthermal. For an assumed source size of 20", the deduced column densities are (0.6-1)x10(14) cm-2 for ethylene oxide and (2-5)x10(14) cm-2 for acetaldehyde. The fractional abundances with respect to H2 are X[c-C2H4O]=(2-6)xl0(-10), and X[CH3CHO]=(0.8-3)x10(-9). The ratio X[CH3CHO]/X[c-C2H4O] varies between 2.6 (NGC 6334F) and 8.5 (G327.3-0.6). We also detected and analysed multiple transitions of CH3OH, CH3OCH3, C2H5OH, and HCOOH. The chemical, and possibly evolutionary, states of NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2 seem to be very similar.

Non-NASA Center↗
DOE OSTI2021

Method for direct conversion of carbon dioxide to dialkyl carbonates using ethylene oxide as feedstock

A method for co-production of high purity dimethyl carbonate and mono-ethylene glycol by applying a reactor, such as a membrane reactor and/or an adsorbent-catalytic reactor by capturing and reacting carbon dioxide with methanol and ethylene oxide. Carbon dioxide may be recovered from primary sources (utilities and industrial processes) by a membrane or solid adsorbent, and subsequently converted to an intermediate hydroxy-ethyl-methyl carbonate by reacting with ethylene oxide and methanol. For high-purity carbon dioxide (obtained by carbon capture technologies or from an ethanol fermentation process), the membrane reactor is replaced with a catalytic reactor for direct conversion of carbon dioxide to hydroxy-ethyl-methyl carbonate by reacting with ethylene oxide and methanol. The hydro-ethyl-methyl carbonate is further reacted with methanol for conversion to dimethyl carbonate. A combination of heterogeneous and homogeneous catalysts is implemented for an effective conversion of carbon dioxide. An integrated reactive distillation process using side reactors is used for facilitating catalytic reaction for production of high purity dimethyl carbonate.

Panchal, Chandrakant B.↗
DOE OSTI2021

Increasing Ionic Conductivity of Poly(ethylene oxide) by Reaction with Metallic Li

Poly(ethylene oxide) (PEO) was the first lithium-ion conducting polymer developed 50 years ago and is still the most popular electrolyte matrix for solid-state lithium metal batteries. While many studies focus on increasing PEO ionic conductivity through doping with Li salts, little work has addressed using PEO and Li directly to generate Li + -conducting species in situ. Reaction between PEO and Li leads to ionic conductivity largely from Li + , in contrast to the case of added salts where the anion contribution dominates. Herein, electrochemical impedance spectroscopy shows the ionic conductivity of PEO thin films increases up to three orders of magnitude (from 10 –7 to 10 –4 S cm –1 ) when contacted with Li at elevated temperature. This is due to the reduction of ether bonds, which produces lithium alkoxides that are responsible for Li + transport. Density functional theory analysis confirms this mechanism as thermodynamically favorable. X-ray photoelectron spectroscopy also shows the presence of organolithium species and Li 2 O, which are responsible for propagating reactions with PEO and forming an electronically insulating layer at the PEO–Li interface that halts further reaction, respectively. The underlying mechanisms of Li–polymer electrolyte reactions is clarified and new pathways for in situ Li + doping of polymer electrolytes is presented.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Influence of Added Salt on Chain Conformations in Poly(ethylene oxide) Melts: SANS Analysis with Complications

Poly(ethylene oxide) (PEO)-based electrolytes have gained increasing attention in both the rechargeable battery industry and fundamental research, but any influence of the ions on the polymer conformation is not fully understood. Small-angle neutron scattering (SANS) is a powerful means to determine single-polymer chain conformations. We conducted SANS experiments on 50:50 blends of perdeuterated PEO (dPEO) and hydrogenous PEO (hPEO) of two different molecular weights (20 and 40 kDa) doped with two different salts (LiTFSI and LiClO 4 ) at various concentrations. An additional measurement with LiI is also reported. The scattering profiles of salt-doped dPEO/hPEO blends were measured, and the incoherent scattering from dPEO and hPEO doped with salt was measured separately. A strong low q upturn was observed in some of the blends and in the pure dPEO homopolymers. The statistical segment lengths of PEO–salt mixtures were derived using a Kratky analysis. The segment length decreases modestly with increasing amounts of LiTFSI but apparently first increases then decreases with added LiClO 4 . At the highest salt concentration examined (r = [Li+]/[EO] = 0.125), a roughly 10% decrease in the statistical segment length was observed in both LiTFSI and LiClO 4 -doped PEOs, for both molecular weights. This work confirms that added salt causes a contraction of the PEO chain dimensions, but the effect appears slightly weaker than reported recently. Certain difficulties in data analysis are also discussed, including the unexplained low q scattering even in pure deuterated polymers, uncertainties in background subtraction, and inappropriate application of the Debye function.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Thin-film composite membranes based on hyperbranched poly(ethylene oxide) for CO 2 /N 2 separation

Cross-linked amorphous poly(ethylene oxide) (XLPEO) is one of the leading membrane materials for post-combustion CO 2 capture. For example, XLPEO prepared from poly(ethylene glycol) methyl ether acrylate (PEGMEA) exhibited CO 2 permeability of 570 Barrer and CO 2 /N 2 selectivity of 41 at 35 °C. However, these XLPEOs cannot be dissolved in coating solutions, making it impossible to be fabricated into thin-film composite (TFC) membranes using state-of-the-art manufacturing processes. In this study, we synthesized high molecular weight yet soluble HPEO via atom transfer radical polymerization (ATRP). These polymers were thoroughly characterized and compared with XLPEO, including thermal transitions, free volumes, and pure-gas sorption and permeation properties. A polymer with the best combination of CO 2 permeability (540 Barrer) and CO 2 /N 2 selectivity (43) was fabricated into defect-free TFC membranes with a thickness as thin as 506 ± 44 nm. When challenged with simulated flue gas containing water vapor at 35 °C for over 100 h, the membrane shows stable CO 2 permeance of 850 GPU and CO 2 /N 2 selectivity of 37, comparable to the leading commercial membranes for carbon capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗