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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Influence of ozone addition on the low-temperature oxidation of dimethyl ether in a jet-stirred reactor

The influence of ozone addition on the low-temperature oxidation of dimethyl ether (DME) was investigated experimentally in an atmospheric-pressure jet-stirred reactor, over the temperature range of 400–800 K. Detailed speciation information was obtained by employing synchrotron vacuum ultraviolet photoionization mass spectrometry. Experimental results revealed that the ozone addition had a positive influence on the production of the highly reactive intermediates. Moreover, the low-temperature reactivity of DME was significantly enhanced, which resulted in the broadening of the temperature window of fuel consumption and intermediates formation at lower temperatures. Therefore, novel experimental data of the low temperature regime (400–500 K) could be obtained. The data set of this special temperature regime yielded insights into the DME low-temperature kinetics, which were further supported with modeling analysis based on two existing DME models (Metcalfe et al., 2013; Wang et al., 2015) combined with an ozone sub-mechanism (Zhao et al., 2016). The analysis showed that temperature-sensitive reactions such as the second oxygen channel could be nearly “frozen” at this low temperature (T < 440 K). Furthermore, the production of some intermediates was found to be strongly governed by reaction pairs, such as CH 3 OCH 2 + O 2 = CH 3 OCH 2 O 2 and CH 3 OCH 2 + O 2 = 2 CH 2 O + OH for the CH 2 O formation. This finding could be useful for examining branching ratios in both models, and the analysis suggested the further modification of the branching ratios for the oxygen addition to CH 3 OCH 2 O 2 pathways and the CH 3 OCH 2 O 2 self-reactions were required. Finally, the influences of the O 3 addition in the sensitive reactions of the fuel initial low-temperature oxidation were investigated in this work. It was interesting to note that O 3 addition could change the dominating reactions in the initial low-temperature oxidation, by the addition of some O 3 -related pathways with relatively high sensitivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Regioisomer-Specific Crystallization of Diglycidyl Ether of Bisphenol F Epoxy Resin

Diglycidyl ether of bisphenol F (DGEBF) is a common industrial epoxy resin, desired for its possible replacement of the bisphenol A (BPA) analogue DGEBA due to potential health hazards of BPA. During curing, crystallization of the DGEBF resin can cause inaccurate resin-to-hardener ratios, resulting in incomplete crosslinking; therefore, understanding the crystallization of DGEBF is important for proper industrial control of the material. Here, in this work, we utilized a combination of single-crystal x-ray diffraction, Raman spectroscopy, and 1 H-NMR to investigate the crystallization of DGEBF. We observed crystallization of two DGEBF regioisomers: ortho-ortho’-DGEBF and ortho-para’-DGEBF, and report their crystal structures. Notably, para-para’-DGEBF crystallization is not observed, indicating crystallization of this regioisomer does not occur under ambient conditions. Density functional theory calculations were performed to describe the phonon modes of the ortho-ortho’- and ortho-para’-DGEBF structures, corroborating Raman signatures for the respective isomers. Using a phonon mode analysis, we identify the presence of three specific optical vibrational modes at 631.3, 344.1, and 345.6 cm -1 that are unique to the para monomer. This work offers insights into the crystallization behavior of DGEBF resins under ambient conditions and may inform potential industrial application of this material.

Neu, Jennifer [Oak Ridge National Laboratory (ORNL↗
DOE OSTI2021

Non-Boltzmann Effects in Chain Branching and Pathway Branching for Diethyl Ether Oxidation

Low-temperature (LT) engine applications have several potential benefits, including reduced emissions and increased efficiency. Attaining these benefits requires accurate kinetic modeling of LT chain branching, which depends heavily on ketohydroperoxide (KHP) decomposition. For diethyl ether (DEE), a promising biofuel, current estimates of the KHP decomposition rate constant are largely based on empirical fits to data. In this study, we investigate the most important KHP isomer in DEE LT oxidation by applying variable reaction coordinate transition state theory to the main pathway for KHP decomposition: OO bond fission to produce •OH and a keto-alkoxy radical, •OQ'O. We also use ab initio kinetics methods to investigate the decomposition of •OQ'O, where we find dominant branching to acetic acid, with the remaining flux going to CH 3 C(O)OCHO. Additionally, new time-resolved measurements of DEE and acetic acid concentrations during LT (450–600 K) DEE oxidation are obtained in a laser photolysis flow reactor coupled with multiplexed photoionization mass spectrometry. These new experimental data, along with jet-stirred reactor data in the literature, are compared with the predictions of a recent DEE mechanism (Tran et al. Proc. Comb. Inst. 2019, 37, 511-519) that was modified with the newly calculated ab initio rate constants for KHP and •OQ'O decomposition. The predictions of the modified mechanism are quite poor when compared to the experimental data; this is primarily due to the new KHP ⇌ •OQ'O + •OH rate constant, which is 1–2 orders of magnitude slower than empirical values employed in recent mechanisms. To reconcile the new KHP rate constant and the experimental data, we explore and quantify the possible role of non-Boltzmann (nB) reaction sequences. The nB reactions have a substantial effect on both the overall mechanism reactivity and the •OQ'O branching to acetic acid. We also provide guidance on the proper implementation of nB reactions in kinetic mechanisms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Quantification of Key Peroxy and Hydroperoxide Intermediates in the Low-Temperature Oxidation of Dimethyl Ether

Dimethyl ether (DME) oxidation is a model chemical system with a small number of prototypical reaction intermediates that also has practical importance for low-carbon transportation. Although it has been studied experimentally and theoretically, ambiguity remains in the relative importance of competing DME oxidation pathways in the low-temperature autoignition regime. To focus on the primary reactions in DME autoignition, we measured the time-resolved concentration of five intermediates, CH 3 OCH 2 OO (ROO), OOCH 2 OCH 2 OOH (OOQOOH), HOOCH 2 OCHO (hydroperoxymethyl formate, HPMF), CH 2 O, and CH 3 OCHO (methyl formate, MF), from photolytically initiated experiments. We performed these studies at P = 10 bar and T = 450-575 K, using a high-pressure photolysis reactor coupled to a time-of-flight mass spectrometer with tunable vacuum-ultraviolet synchrotron ionization at the Advanced Light Source. Our measurements reveal that the timescale of ROO decay and product formation is much shorter than predicted by current DME combustion models. The models also strongly underpredict the observed yields of CH 2 O and MF and do not capture the temperature dependence of OOQOOH and HPMF yields. Adding the ROO + OH $\rightarrow$ RO + HO 2 reaction to the chemical mechanism (with a rate coefficient approximated from similar reactions) improves the prediction of MF. Increasing the rate coefficients of ROO ↔ QOOH and QOOH + O 2 ↔ OOQOOH reactions brings the model predictions closer to experimental observations for OOQOOH and HPMF, while increasing the rate coefficient for the QOOH $\rightarrow$ 2 CH 2 O + OH reaction is needed to improve the predictions of formaldehyde. In conclusion, to aid future quantification of DME oxidation intermediates by photoionization mass spectrometry, we report experimentally determined ionization cross-sections for ROO, OOQOOH, and HPMF.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Kinetics and Mechanism of the Singlet Oxygen Atom Reaction with Dimethyl Ether

Here, we combine in situ laser spectroscopy, quantum chemistry, and kinetic calculations to study the reaction of a singlet oxygen atom with dimethyl ether. Infrared laser absorption spectroscopy and Faraday rotation spectroscopy are used for the detection and quantification of the reaction products OH, H 2 O, HO 2 , and CH 2 O on submillisecond time scales. Fitting temporal profiles of products with simulations using an in-house reaction mechanism allows product branching to be quantified at 30, 60, and 150 Torr. The experimentally determined product branching agrees well with master equation calculations based on electronic structure data and transition state theory. The calculations demonstrate that the dimethyl peroxide (CH 3 OOCH 3 ) generated via O-insertion into the C–O bond undergoes subsequent dissociation to CH 3 O + CH 3 O through energetically favored reactions without an intrinsic barrier. This O-insertion mechanism can be important for understanding the fate of biofuels leaking into the atmosphere and for plasma-based biofuel processing technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Quaternary Ammonium-Functionalized Poly(Arylene Ether Sulfone) Random Copolymers for Direct Air Capture

Direct air capture (DAC) is a promising tool for reducing CO 2 concentrations in the atmosphere and fighting climate change. We synthesized a series of quaternary ammonium (QA) functionalized poly(arylene ether sulfone) copolymers with varying mole fractions of charge content and demonstrated their potential as sorbents for DAC. Molecular weight analysis determined high monomer conversion was achieved in <6 h and relatively high molecular weights for all copolymer compositions. Thermal analysis revealed all polymers had degradation temperatures >240 °C and a single glass transition temperature (T g ); the T g decreased with an increase in ion exchange capacity (IEC). Fractional free volume and water uptake percentage increased and water contact angle decreased with the number of QA sites when compared to a neutral, commercially available polysulfone (Udel® P-1700 PSU). Next, the novel series of ammonium-functionalized copolymers exhibited a moisture-mediated capture and release of atmospheric CO 2 . When exposed to air containing 30% relative humidity the polymers captured CO 2 and the capacity increased with the IEC. When the relative humidity was increased to 95% the samples released the CO 2 . This study demonstrates a promising CO 2 DAC sorbent and highlights the possibility for continuous DAC with purpose-built free-standing membranes.

42 ENGINEERING↗
DOE OSTI2025

Redox-Active Crown Ether Copolymer for Selective Lithium Recovery from Spent Lithium-Ion Batteries

The increasing demand for lithium, alongside concerns over resource scarcity and supply chain risks, has driven the need for alternative lithium sources, particularly from spent lithium-ion batteries (LIBs). Here, in this work, we introduce a redox-active crown ether copolymer designed for highly selective and electrochemically reversible lithium recovery from organic LIB leachates. A lithium-selective moiety, (12-crown-4)methyl methacrylate (12C4MA), is combined with a redox-active moiety, ferrocenylpropyl methacrylamide (FPMAm), into a redox copolymer electrosorbent to replace acid-based regeneration with electrostatic repulsion. The redox response enhances lithium ingress into the polymer, doubling lithium uptake (0.58 mol Li /mol CrE ) and enabling electrochemical regeneration upon the FPMAm oxidation. Our system exhibits exclusive lithium uptake, even in complex leachates containing competing metals (e.g., iron, nickel, and cobalt) and organic degradants. Techno-economic analysis highlights high energy efficiency and competitive lithium pricing to the market value (∼$12.7 per kg Li ). Overall, our work demonstrates a scalable, electrified adsorbent platform for sustainable and chemical-free critical metal recovery.

adsorption↗
DOE OSTI2022

Porous Liquids as Electrolyte: A Case Study of Li + and Mg 2+ Ion Transport in Crown Ether-Based Type-II Porous Liquids

Here, we demonstrate crown ether (CE)-based type II porous liquid (PL) electrolytes in which CEs provide internal porosity and are capable of coordinating with Li + and Mg 2+ ions. We investigated the physicochemical properties of the PL electro-lytes with different functional groups and cavity sizes. Among the electrolytes studied, the 12-crown-4 (12C4)-based PL electrolyte exhibited the most enhanced ionic conductivity due to size match between the CE cavity and the Li + ion. Nu-clear magnetic resonance and Fourier transform infrared analyses revealed that addition of CEs reduces the Li + ion–solvent interaction, resulting in the formation of Li-CE complexes. The simulation study clearly showed that the solvated Li + and Mg 2+ ions form complexes with 12C4. The strategy described here using CE-based PLs should be applicable to the design versatile electrolytes for various metal-ion batteries.

Shin, Sun Hae Ra↗
DOE OSTI2023

Isolation of a californium(II) crown–ether complex

The actinides, from californium to nobelium (Z = 98–102), are known to have an accessible +2 oxidation state. Understanding the origin of this chemical behaviour requires characterizing Cf II materials, but investigations are hampered by the fact that they have remained dificult to isolate. This partly arises from the intrinsic challenges of manipulating this unstable element, as well as a lack of suitable reductants that do not reduce Cf III to Cf°. Here we show that a Cf II crown–ether complex, Cf(18-crown-6)I 2 , can be prepared using an Al/Hg amalgam as a reductant. Spectroscopic evidence shows that Cf III can be quantitatively reduced to Cf II , and rapid radiolytic re-oxidation in solution yields co-crystallized mixtures of Cf II and Cf III complexes without the Al/Hg amalgam. Furthermore, quantum-chemical calculations show that the Cf– ligand interactions are highly ionic and that 5f/6d mixing is absent, resulting in weak 5f→5f transitions and an absorption spectrum dominated by 5f→6d transitions.

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

Direct time-resolved detection and quantification of key reactive intermediates in diethyl ether oxidation at T = 450–600 K

High-pressure multiplexed photoionization mass spectrometry (MPIMS) with tunable vacuum ultraviolet (VUV) ionization radiation from the Lawrence Berkeley Labs Advanced Light Source is used to investigate the oxidation of diethyl ether (DEE). Kinetics and photoionization (PI) spectra are simultaneously measured for the species formed. Several stable products from DEE oxidation are identified and quantified using reference PI cross-sections. In addition, we directly detect and quantify three key chemical intermediates: peroxy (ROO˙), hydroperoxyalkyl peroxy (˙OOQOOH), and ketohydroperoxide (HOOP[double bond, length as m-dash]O, KHP). These intermediates undergo dissociative ionization (DI) into smaller fragments, making their identification by mass spectrometry challenging. Furthermore, with the aid of quantum chemical calculations, we identify the DI channels of these key chemical species and quantify their time-resolved concentrations from the overall carbon atom balance at T = 450 K and P = 7500 torr. This allows the determination of the absolute PI cross-sections of ROO˙, ˙OOQOOH, and KHP into each DI channel directly from experiment. The PI cross-sections in turn enable the quantification of ROO˙, ˙OOQOOH, and KHP from DEE oxidation over a range of experimental conditions that reveal the effects of pressure, O 2 concentration, and temperature on the competition among radical decomposition and second O 2 addition pathways.

42 ENGINEERING↗
DOE OSTI2021

Zirconium and hafnium polyhedral oligosilsesquioxane complexes – green homogeneous catalysts in the formation of bio-derived ethers via a MPV/etherification reaction cascade

The polyhedral oligosilsesquioxane complexes, {[(isobutyl) 7 Si 7 O 12 ]ZrOPr i ·(HOPr i )}2 (I), {[(cyclohexyl) 7 Si 7 O 12 ]ZrOPr i ·(HOPr i )} 2 (II), {[(isobutyl) 7 Si 7 O 12 ]HfOPr i ·(HOPr i )} 2 (III) and {[(cyclohexyl) 7 Si 7 O 12 ]HfOPr i ·(HOPr i )} 2 (IV), were synthesized in good yields from the reactions of M(OPr i ) 4 (M = Zr, Hf) with R-POSS(OH) 3 (R = isobutyl, cyclohexyl), resp. I–IV were characterized by 1 H, 13 C and 29 Si NMR spectroscopy and their dimeric solid-state structures were confirmed by X-ray analysis. I–IV catalyze the reductive etherification of 2-hydroxy- and 4-hydroxy and 2-methoxy and 4-methoxybenzaldehyde and vanillin to their respective isopropyl ethers in isopropanol as a “green” solvent and reagent. I–IV are durable and robust homogeneous catalysts operating at temperatures of 100–160 °C for days without significant loss of catalytic activity. Likewise, I–IV selectively catalyze the conversion of 5-hydroxymethylfurfural (HMF) into 2,5-bis(isopropoxymethyl)furane (BPMF), a potentially high-performance fuel additive. Similar results were achieved by using a combination of M(OPr i ) 4 and ligand R-POSS(OH) 3 as a catalyst system demonstrating the potential of this “in situ” approach for applications in biomass transformations. A tentative reaction mechanism for the reductive etherification of aldehydes catalysed by I–IV is proposed.

09 BIOMASS FUELS↗
DOE OSTI2020

The high-yield direct synthesis of dimethyl ether from CO 2 and H 2 in a dry reaction environment

Direct dimethyl ether (DME) synthesis from CO 2 and H 2 is considered a promising production route. However, this process is thermodynamically and kinetically restricted by the presence of water as a byproduct. In this study, a water-conduction membrane was incorporated into the direct DME synthesis reactor to generate a dry reaction environment. In the absence of water, the activities of the CO 2 hydrogenation catalyst (CZA) and methanol dehydration catalyst (HZSM-5) were boosted 4- and 10-fold, respectively, and single-pass CO 2 conversion of up to 73.4%, far beyond equilibrium, and DME yields of up to 54.5% were obtained. Moreover, the good protection of the catalysts against fast deactivation was demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Effect of poly[oligo(ethylene glycol) methyl ether methacrylate] side chain length on the brush swelling behavior in A/B/A–B ternary blends with polystyrene

The phase behavior of ternary blends composed of two homopolymers (A, B) and their corresponding diblock copolymer (A–B) has been widely studied, with emphasis on the volumetrically symmetric isopleth and the formation of bicontinuous microemulsions. However, almost all the previous studies employed linear polymers, and little is known about the impact of polymer architecture on the phase behavior of such ternary blends. Here, in this work, we report the self-assembly of three sets of ternary blends of polystyrene (PS) and poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA n ), with different lengths of oligo(ethylene glycol) side chains n. Small-angle X-ray scattering was used to probe the phase behavior at different compositions and temperatures. The order-to-disorder transition temperature was found to be impacted by the side chain length. It was also observed that longer side chains lead to poorer miscibility of homopolymers in the corresponding block, resulting in a more “dry-brush” like swelling behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗