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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Interface‐Controlled Redox Chemistry in Aqueous Mn 2 ⁺/MnO₂ Batteries

Manganese dioxide (MnO 2 ) deposition/dissolution (Mn 2+ /MnO 2 ) chemistry, involving a two-electron-transfer process, holds promise for safe and eco-friendly large-scale energy storage. However, challenges like electrode/electrolyte interface environment fluctuations (H + and H 2 O activity), irreversible Mn degradation, and limited understanding of degradation mechanisms hinder the reversibility of the Mn 2+ /MnO 2 conversion. This study demonstrates a vanadyl/pervanadyl (VO 2+ /VO 2 + ) redox-mediated interface designed for high-energy Mn 2+ /MnO 2 batteries. Unlike flow systems, this work uncovers, for the first time, the mechanism of a static redox-mediated interface in regulating interfacial H + and H 2 O activities. Significantly, the VO 2+ /VO 2 + chemical redox mediation targets Mn 3+ intermediates, suppressing their hydrolysis and enabling 100% Mn 2+ /MnO 2 conversion. The redox-mediated interface enhances the Mn redox electron transfer process, achieving a stable ≈95% coulombic efficiency and ultrahigh capacity of 100 mAh cm −2 with an areal energy density of 111 mWh cm −2 , outperforming flow systems. The electrode also exhibits an average specific capacity of 593 mAh g −1 , approaching the theoretical limit of 616 mAh g −1 , and a specific energy density of 721 Wh kg −1 at high MnO 2 loadings (50–150 mg cm −2 ). Furthermore, the findings highlight the critical role of interfacial redox mediation in regulating H + and H 2 O activities and underscore the significance of interface dynamics.

Xue, Xinzhe [University of California, Santa Cruz,↗
DOE OSTI2026

Spatiotemporal 4D Whole-cell Modeling of a Minimal Autotroph Reveals Central Carbon Metabolism Regulated Locally by Protein Megacomplexes via Post-translational Modifications under Light Disturbance

Photosynthetic microorganisms rely on multiple pathways in central carbon metabolism to adapt to fluctuating light and energy availability across diel cycles. Mechanistic insight into the regulatory dynamics of this adaptation requires integrating processes spanning disparate timescales, from rapid redox-dependent post-translational modifications (PTMs) to slower changes in protein expression and metabolic pathway usage. To address this complexity beyond genome-based inference and traditional modeling, we develop a whole-cell four-dimensional (3D + time) model of the marine cyanobacterium Prochlorococcus marinus MED4 that explicitly represents the spatial organization of enzymatic and molecular processes in central carbon metabolism under light perturbation. We employ a perturbation-based research design to experimentally generate time-series, multi-omics measurements that provide molecular descriptors and cryo-ET derived 3D segmented volumes as constraints for this dynamic 4D framework. The integration of experiments and modeling across defined light regimes enables quantitative validation of system-level responses and forecasting under distinct light disturbances. We test the hypothesis that light-dependent redox PTMs regulating the structural assembly of a protein megacomplex, the “dark complex,” modulate metabolic flux at a conserved regulatory node of the Calvin–Benson cycle (CBC) in cyanobacteria. Our model shows that subcellular spatial organization buffers rapid light-induced changes in thylakoid reaction rates, which are followed by redox-PTM-mediated sequestration or release of CBC enzymes in the dark complex, ultimately impacting carbon fixation dynamics within carboxysomes. Comparison with an equivalently parameterized well-mixed stochastic model demonstrates that post-translational regulation not only buffers transcriptional noise and diffusion-driven fluctuations but also stabilizes phenotypic outcomes, underscoring the importance of spatial heterogeneity in phenotypic robustness. This ability to probe adaptive, spatiotemporally resolved mechanisms in photosynthetic machinery and central carbon metabolism addresses a critical gap in genotype-to-phenotype inference and expands modeling and design capabilities for understudied or genetically intractable autotrophs such as P. marinus MED4.

Johnson, Connah G.↗
DOE OSTI2022

Triggering Anionic Redox Activity in Li 3 NbS 4 Through Cationic Disordering or Substitution

Extensive utilization of Li-ion batteries for varieties of applications necessitates ceaseless improvements of electrode materials for achieving higher energy density. Towards this goal, Li-rich layered oxides exhibiting high capacity due to cumulated cationic and anionic redox activities are under study for nearly a decade. Still, several unanswered questions remain with respect to these Li-driven anionic redox reactions in terms of the activation process and long-term consequences upon cycling. Here, the Li-rich Li 3 NbS 4 phase is focused, and synthesized as two different polymorphs, namely ordered and disordered phases. From analyses of their chemical and electrochemical properties, a crystal-electronic structure relationship is unraveled that triggers the anionic redox activity in these compounds. Moreover, through complementary theoretical calculations, the capability of cationic disorder to trigger anionic redox activity via the hybridization of cationic and non-bonding anionic energy levels is shown. This finding is further supported by the appearance of anionic redox activity by introducing the disorder through cationic substitution. Altogether, the insights derived here can help in designing new anionic redox materials with optimum performances for practical applications.

25 ENERGY STORAGE↗
DOE OSTI2019

Quantification of Anionic Redox Chemistry in a Prototype Na-Rich Layered Oxide

Harnessing anionic redox reactions is of prime importance for boosting the capacity of sodium-ion batteries (NIBs). However, quantifying the cyclability of anionic redox reactions is still challenging. Herein, we conduct a qualitative and quantitative investigation of the cationic and anionic redox reactions of a prototype Na-rich layered oxide, namely, Na 3 RuO 4 , by a combination of bulk-sensitive X-ray absorption spectroscopy and full-range mapping of resonant inelastic X-ray scattering. We unequivocally reveal that both Ru cations and oxygen anions are involved in the charge compensation process of Na 3 RuO 4 . Ru redox is highly reversible over extended electrochemical cycles, while the cyclability of lattice oxygen redox gradually decreases with the retention of only 36% after 30 cycles, which is mainly responsible for the capacity fading of Na 3 RuO 4 . Finally, our findings provide deeper insights into the complex oxygen redox mechanism, which plays a decisive role for designing high-energy Na-rich electrode materials for NIBs.

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

Cytochrome b 5 : A versatile electron carrier and regulator for plant metabolism

Cytochrome b 5 (CB5) is a small heme-binding protein, known as an electron donor delivering reducing power to the terminal enzymes involved in oxidative reactions. In plants, the CB5 protein family is substantially expanded both in its isoform numbers and cellular functions, compared to its yeast and mammalian counterparts. As an electron carrier, plant CB5 proteins function not only in fatty acid desaturation, hydroxylation and elongation, but also in the formation of specialized metabolites such as flavonoids, phenolic esters, and heteropolymer lignin. Furthermore, plant CB5s are found to interact with different non-catalytic proteins such as ethylene signaling regulator, cell death inhibitor, and sugar transporters, implicating their versatile regulatory roles in coordinating different metabolic and cellular processes, presumably in respect to the cellular redox status and/or carbon availability. Compared to the plentiful studies on biochemistry and cellular functions of mammalian CB5 proteins, the cellular and metabolic roles of plant CB5 proteins have received far less attention. This article summarizes the fragmentary information pertaining to the discovery of plant CB5 proteins, and discusses the conventional and peculiar functions that plant CB5s might play in different metabolic and cellular processes. Gaining comprehensive insight into the biological functions of CB5 proteins could offer effective biotechnological solutions to tailor plant chemodiversity and cellular responses to environment stimuli.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1984

Development of electrodes for the NASA iron/chromium

This program was directed primarily to the development of the negative (Cr3+/Cr2+) electrode for the NASA chromous/ferric Redox battery. The investigation of the effects of substrate processing and gold/lead catalyzation parameters on electrochemical performance were continued. In addition, the effects of reactant cross-mixing, acidity level, and temperature were examined for both Redox couples. Finally, the performance of optimized electrodes was tested in system hardware (1/3 square foot single cell). The major findings are discussed: (1) The recommended processing temperature for the carbon felt, as a substrate for the negative electrode, is 1650 to 1750 C, (2) The recommended gold catalyzation procedure is essentially the published NASA procedure (NASA TM-82724, Nov. 1981) based on deposition from aqueous methanol solution, with the imposition of a few controls such as temperature (25 C) and precatalyzation pH of the felt (7), (3) Experimental observations of the gold catalyzation process and subsequent electron microscopy indicate that the gold is deposited from the colloidal state, induced by contact of the solution with the carbon felt, (4) Electrodeposited lead appears to be present as a thin uniform layer over the entire surface of the carbon fibers, rather than an discrete particles, and (5) Cross-mixing of reactants (Fe-2+ in negative electrode solution or Cr-3+ in the positive electrode solution) did not appear to produce significant interference at either electrode.

Swette, L.↗
DOE OSTI2022

Realizing Two-Electron Transfer in Ni(OH) 2 Nanosheets for Energy Storage

The theoretical capacity of a given electrode material is ultimately determined by the number of electrons transferred in each redox center. The design of multi-electron transfer processes could break through the limitation of one–electron transfer and multiply the total capacity, but is difficult to achieve because multiple electron transfer processes are generally thermodynamically and kinetically more complex. In this work, we report the discovery of two-electron transfer in monolayer Ni(OH) 2 nanosheets, which contrasts with the traditional one-electron transfer found in multilayer materials. The first-principles calculations predict that the first oxidation process from Ni 2+ →Ni 3+ occurs easily, whereas the second electron transfer from Ni 3+ →Ni 4+ is strongly hindered in multilayer materials by both the interlayer hydrogen bonds and the domain H structure induced by the Jahn-Teller distortion of the Ni 3+ (t 2g 6 e g 1 ) centered octahedra. In contrast, the second electron transfer can easily occur in monolayers because all H’s are fully exposed. Experimentally, the as-prepared monolayer is found to deliver an exceptional redox capacity of ~ 576 mAh/g, nearly two times the theoretical capacity of one-electron processes. In-situ experiments demonstrate that monolayer Ni(OH) 2 can transfer two electrons and mostly transform to Ni 4+ in the charging process, while bulk Ni(OH) 2 can be partially transformed . Our work reveals a new redox reaction mechanism in atomically thin Ni(OH) 2 nanosheets, and suggests a promising path towards tuning the electron transfer numbers to multiply the capacity of the relevant energy storage materials.

25 ENERGY STORAGE↗
DOE OSTI2019

Optimization of a Lithium Ion Battery Bioleaching Process Utilizing Organic Acids Produced by Gluconobacter oxydans

Growing our global economic and environmental focus relies, in part, on our development of a sustainable system to recycle valuable metals. This endeavor to recycle these elements falls within the scope of Idaho National Laboratories (INL) mission to pursue new sustainable energy systems that are competitive. To succeed in this endeavor in not only a low-cost but environmentally safe practice, Gluconobacter oxydans was utilized for its ability to produce a bio-lixiviant known for its critical material leaching abilities. G. oxydans is a rod-shaped, gram negative, acidophilic, and obligately aerobic organism. Unlike many other aerobic organisms, it does not completely oxidize its carbon sources to water and carbon dioxide. Instead it incompletely oxidizes its substrates to aldehydes, ketones and organic acids. Because of this metabolic pathway, it was utilized in a batch reactor setting to produce sufficient amounts of a low-pH bio-lixiviant so that leaching processes could be performed on lithium ion battery cathode powders. Some of these processes included adding different molar ratios of a redox agent to the produced bio-lixiviant, alternating concentrations of lithium ion battery cathode powders, varying leaching time, and changing the temperature each leach was performed at. From this, a biohydrometallurgy process was successfully created for the leaching of cobalt from lithium ion cathode powders This project provided a multitude of laboratory and research experiences that resulted in ample opportunity for professional and personal growth. In addition to this, the INL experience fostered the development of many personal skills and business skills to assist in future career opportunities.

25 ENERGY STORAGE↗
DOE OSTI2022

Analysis of DWPF Sludge Batch 6 (Macrobatch 7): Pour Stream Glass Samples

The Defense Waste Processing Facility (DWPF) began processing Sludge Batch 6 (SB6), also referred to as Macrobatch 7 (MB7), in June 2010. SB6 is a blend of the heel of Tank 40 from Sludge Batch 5 (SB5), H-Canyon Np transfers and SB6 that was transferred to Tank 40 from Tank 51.1 SB6 was processed using Frit 418. Sludge is received into the DWPF Chemical Processing Cell (CPC) and is processed through the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator Tank (SME). The treated sludge slurry is then transferred to the Melter Feed Tank (MFT) and fed to the melter. During processing of each sludge batch, the DWPF is required to take at least one glass sample to meet the objectives of the Glass Product Control Program (GPCP) and to complete the necessary Production Records so that the final glass product may be disposed of at a Federal Repository. The DWPF requested various analyses of radioactive glass samples obtained from the melter pour stream during processing of SB6 as well as reduction/oxidation (REDOX) analysis of MFT samples to determine the impact of Argon bubbling. Sample analysis followed the Task Technical and Quality Assurance Plan (TTQAP) and an Analytical Study Plan (ASP). Four Pour Stream (PS) glass samples and two MFT slurry samples were delivered to the Savannah River National Laboratory (SRNL) from the DWPF. Table 1-1 lists the sample information for each pour stream glass sample. SB6 PS3 (S03472) was selected as the official pour stream sample for SB6 and full analysis was requested. This report details the visual observations of the as-received SB6 PS No.3 glass sample as well as results for the chemical composition, Product Consistency Test (PCT), radionuclide content, noble metals, and glass density. REDOX results will be provided for all four pour stream samples and vitrified samples of MFT-558 and MFT-568A. Where appropriate, data from other pour stream samples will be provided.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Revealing of the Activation Pathway and Cathode Electrolyte Interphase Evolution of Li-Rich 0.5Li 2 MnO 3 ·0.5LiNi 0.3 Co 0.3 Mn 0.4 O 2 Cathode by in Situ Electrochemical Quartz Crystal Microbalance

The first-cycle behavior of layered Li-rich oxides, including Li 2 MnO 3 activation and cathode electrolyte interphase (CEI) formation, significantly influences their electrochemical performance. However, the Li 2 MnO 3 activation pathway and the CEI formation process are still controversial. Here, the first-cycle properties of xLi 2 MnO 3 ·(1- x) LiNi 0.3 Co 0.3 Mn 0.4 O 2 ( x = 0, 0.5, 1) cathode materials were studied with an in situ electrochemical quartz crystal microbalance (EQCM). The results demonstrate that a synergistic effect between the layered Li 2 MnO 3 and LiNi 0.3 Co 0.3 Mn 0.4 O 2 structures can significantly affect the activation pathway of Li 1.2 Ni 0.12 Co 0.12 Mn 0.56 O 2 , leading to an extra-high capacity. It is demonstrated that Li 2 MnO 3 activation in Li-rich materials is dominated by electrochemical decomposition (oxygen redox), which is different from the activation process of pure Li 2 MnO 3 governed by chemical decomposition (Li 2 O evolution). CEI evolution is closely related to Li + extraction/insertion. Finally, the valence state variation of the metal ions (Ni, Co, Mn) in Li-rich materials can promote CEI formation. This study is of significance for understanding and designing Li-rich cathode-based batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Wavelength-Dependent Energy and Charge Transfer in MOF: A Step toward Artificial Porous Light-Harvesting System

Chromophore assemblies within well-defined porous coordination polymers, such as metal–organic frameworks (MOFs), can emulate the functionality of the antenna rings of chlorophylls in light-harvesting complexes (LHCs). The chemical, electronic, and structural diversities define MOFs as a promising platform where photogenerated excitons can be displaced to redox catalysts similar to the reaction center of the LHC. The precise positioning of the pigments and complementary redox units enables us to understand the charge/energy-transfer process within these crystalline solid compositions. In this study, we postsynthetically anchored tetraphenylporphyrinato zinc(II) (TPPZn)-derived complementary pigment within the 1D pores of 1,3,6,8-tetrakis(p-benzoicacid)pyrene (H4TBAPy)-derived NU-1000 MOF to form a high-density donor–acceptor system. The ground- and excited-state redox potentials of the donor and acceptor were chosen to facilitate an energy transfer (EnT) from the excited MOF (i.e., NU-1000*) to TPPZn and a charge transfer (CT) from excited porphyrin (i.e., TPPZn*). Thus, the processes depend on the excitation wavelength. The energy transfer process was spectroscopically probed by excitation–emission mapping: MOF emission was completely quenched at 460 nm, where the pyrene-centered emission was expected. Instead, the excited MOF efficiently transfers the energy to manifest a TPPZn-centered emission at 670 nm (k EnT ≈ 4.7 × 10 11 s–1). The excited TPPZn pigment, with a neighboring TBAPy linker, forms an artificial “special-pair”-like system driving the charge-separation process (k CT = 1.2 × 10 10 s –1 ). The findings demonstrate a synthetic MOF-based artificial LHC system where their well-defined structure will open up new possibilities as the separated charge can hop along the 1D pore channel for further mechanistic understanding and future developments.

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

Optimization of Oxygen Electrode Combined with Soluble Catalyst to Enhance the Performance of Lithium-Oxygen Battery

Lithium-air batteries possess a high theoretical energy density among the current battery technologies, and are expected to become the driving power for electric vehicles. However, the practical application of lithium air batteries is handicapped by their poor cycle life, high over-charge potential and low energy efficiency. Numerous studies have performed to improve the kinetics of the electrochemical reaction. Making a good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalyst system is under intense scrutiny. In this work, we report a rational design of air electrode, which derives from biomass and presents a three-dimensional porous carbon architecture with high specific surface and large volume expansion coefficient. Combining with a soluble catalyst, this oxygen electrode presents an ultrahigh areal specific capacity of 7.95 mAh/cm 2 and a long cycling life up to 1000 cycles with suppressed polarization (about 0.46 V). Finally, the greatly improved overall performance is due to the synergetic effect of the novel designed oxygen electrode capable of mediating the redox mediators to trigger the ORR and OER process.

25 ENERGY STORAGE↗
DOE OSTI2024

Extracellular Charge Transport in Microbial Redox Chains: Linking the Living and Non-Living Worlds

The fundamental process of electron transfer (ET) within and between molecules dictates all biological energy conversion strategies, including respiration and photosynthesis. This project resulted in a comprehensive physics-based understanding of the mechanisms and limits of redox networks that mediate and regulate electron transport through microbial metabolic pathways, with special emphasis on environmental microbes that can acquire energy by catalyzing anodic or cathodic reactions on solid-state electrodes (extracellular electron transfer, or EET). By performing electron transfer to/from electrodes, such microbes may be used as biocatalysts for converting the energy stored in diverse chemical fuels to electricity, or vice versa (microbial electrosynthesis), in renewable energy technologies.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Measuring Hydroxylammonium, Nitrate, and Nitrite Concentration with Raman Spectroscopy for 238 Pu Supply Program

Optical spectroscopy has great potential to improve the timeliness of important analytical measurements for the 238 Pu Supply Program by enabling real-time analysis of process solutions within radiochemical hot cells. Hydroxylammonium (H 3 NOH + ]), nitrate (NO 3 - ), and nitrite (NO 2 - ) are three important molecular species present in multiple aqueous streams throughout the program’s flow sheet. The concentration of each species normally goes uncharacterized during processing. However, rapid quantification may benefit the program because uncertainties in kinetic redox expressions describing hydroxylammonium (HA) and nitrite reactions with Np and Pu leads to uncertainty in process model predictions for solvent extraction runs. HA concentration is normally quantified using ion chromatography, a technique that requires diluted grab samples taken out of the hot cell and analyzed off-line. Here we evaluate Raman spectroscopy for determining the concentration of H 3 NOH + , NO 3 - , and NO 2 - in benchtop tests to determine limits of detection. We also consider the possibility of using Raman spectroscopy in both glove box and hot cell environments for rapid analysis and pinpoint additional development opportunities needed to make this application successful.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

Dual oxidation state induced oxygen vacancies in Pr substituted BiFeO3 compounds: An effective material activation strategy to enhance the magnetic and visible light-driven photocatalytic properties

Highlights: • BiFeO{sub 3} with tunable oxygen vacancy is achieved through Pr substitution. • Dual oxidation of Pr ions is found to be the origin of oxygen vacancies in BiFeO{sub 3}. • Mechanism of the observed photocatalytic activity could be due to the oxygen vacancy. - Abstract: Bi{sub 1-x}P{sub x}FeO{sub 3} (BP{sub x}FO) nanoparticulates with tunable oxygen vacancy have been synthesized via sol-gel process. Substitution induced oxygen vacancy defects in BP{sub x}FO compositions were evidenced from their X-ray photoelectron spectra, where the mechanism behind the formation of oxygen vacancy was essentially found to be the dual oxidation states of Pr (+3/+4) ions. The origin of the observed enhanced magnetic properties in BP{sub x}FO nanoparticulates is attributed to be the oxygen vacancy mediated alterations in FeOFe bond angle and the alignment of Pr-3d magnetic moments with Fe-3d magnetic moments, which is resulted the ferromagnetic exchange interactions in the BP{sub x}FO system. The observed enhanced photocatalytic activity of BP{sub x}FO compositions is attributed to the formation of defective states in the valence band due to the oxygen vacancies that favored the dispersion of band edge position with required photocatalytic redox potential as well as the acceleration of the charge separation process in these defective BP{sub x}FO systems.

36 MATERIALS SCIENCE↗
NASA NTRS2003

SNC Oxygen Fugacity Recorded in Pyroxenes and its Implications for the Oxidation State of the Martian Interior: An Experimental and Analytical Study

Knowledge of the oxidation state of a magma is critical as it is one of the parameters which controls the nature and composition of the resulting crystals. In terrestrial magmatic systems, oxygen fugacity (fo2) is known to vary by over nine orders of magnitude. With variations of this magnitude, understanding the compositional differences, phase changes, and crystallization sequence variations, caused by the magma fo2, is essential in deciphering the origin of all igneous rocks. Magmatic oxidation state is of great importance in that it reflects the degree of oxidation of the source region and can provide insight into magmatic processes, such as metasomatism, degassing, and assimilation, which may have changed them. Carmichael [1991] argues that most magmas are unlikely to have their redox states altered from those of their source region. This assumption allows for estimation of the oxidation state of planetary interiors. Conversely, it is known that the fo2 of the magma can be affected by other processes, which occur outside of the source region and therefore, the oxidation state may record those too. Processes which could overprint source region fugacities include melt dehydrogenation or other volatile loss, water or melt infiltration, or assimilation of oxidized or reduced wallrock. Understanding which of these processes is responsible for the redox state of a magma can provide crucial information regarding igneous processes and other forces active in the region. The composition of the SNC basalts and their widely varying proposed oxidation states raise some interesting questions. Do the SNC meteorites have an oxidized or reduced signature? What was the oxygen fugacity of the SNC source region at the time of melt generation? Is the fugacity calculated for the various SNC samples the fugacity of the magma source region or was it overprinted by later events? Are there different oxidation states in the Martian interior or a single one? This proposal seeks to address all of these questions.

McCanta, M. C.↗
NASA NTRS1996

Redox Disproportionation of Glucose as a Major Biosynthetic Energy Source

Previous studies have concluded that very little if any energy is required for the microbial biosynthesis of amino acids and lipids from glucose -- processes that yield almost as much ATP (adenosine triphosphate) as they consume. However, these studies did not establish the strength nor the nature of the energy source driving these biological transformations. To identify and estimate the strength of the energy source behind these processes, we calculated the free energy change due to the redox disproportionation of substrate carbon of (a) 26 redox-balanced fermentation reactions, and (b) the biosynthesis of amino acids, lipids, and nucleotides of E. coli from glucose. A plot of the negative free energy of these reactions per mmole of carbon as a function of the number of disproportionative electron transfers per mmol of carbon showed that the energy yields of these fermentations and biosyntheses were directly proportional to the degree of redox disproportionation of carbon. Since this linear relationship showed that redox disproportionation was the dominant energy source of these reactions, we were able to establish that amino acid and lipid biosynthesis obtained most of their energy from redox disproportionation (greater than 94%). In contrast nucleotide biosynthesis was not driven by redox disproportionation of carbon, and consequently depended completely on ATP for energy. This crucial and previously unrecognized role of sugars as an energy source of biosynthesis suggests that sugars were involved at the earliest stage in the origin of anabolic metabolism.

Weber, Arthur L.↗
DOE OSTI2019

Redox oxidative cracking of n -hexane with Fe-substituted barium hexaaluminates as redox catalysts

Light olefins such as ethylene and propylene are critical building blocks in the chemical industry and are currently produced mainly from steam cracking of naphtha. However, the highly endothermic nature of steam generation and the cracking reactions make this process highly energy- and CO 2 -intensive. Coke formation in the steam cracker tubes represents another obstacle. To address these challenges, we proposed a chemical looping approach to convert naphtha into olefins via a redox oxidative cracking (ROC) process. In the present work, Fe-substituted barium hexaaluminates (BaFe x Al 12– x O 19 ) were investigated as oxygen carriers, or redox catalysts, to convert n -hexane to olefins via ROC. The cyclic redox scheme facilitated by the Fe-substituted hexaaluminates allows autothermal operation and higher olefin yields relative to the endothermic steam-cracking process. While base BaFe x Al 12– x O 19 ( x = 1, 2, 3, 4, 6) oxides showed high CO x yields (8.4–55.2%) in ROC of n -hexane, 20 wt% Na 2 WO 4 promotion of BaFe 6 Al 6 O 19 (20-NaW/BaFe6) significantly inhibited CO x formation (0.6–1.2% CO x yield) while oxidizing all the H 2 produced during cracking within a temperature range of 600–700 °C and GHSV of 9000 h –1 . Benefiting from the donation of selective lattice oxygen, we report 20-NaW/BaFe6 more than doubled the olefin yield when compared to that from thermal cracking (26.0% vs. 12.8%). Moreover, decreasing the GHSV from 9000 h –1 to 2250 h –1 resulted in 8.5% increase in n -hexane conversion on an absolute basis, while maintaining nearly the same olefin selectivity. Long-term stability of the 20-NaW/BaFe6 oxygen carrier was also demonstrated within 30 cycles at 700 °C and 2250 h –1 , achieving an olefin yield in the range of 31.3–32.4% and low CO x yield of 0.6–0.7%. XPS analysis of cycled BaFe6 revealed a shift towards near-surface Ba enrichment upon redox cycling. In comparison, both as-prepared and cycled 20-NaW/BaFe6 showed suppression of near surface Ba content, indicating that Na 2 WO 4 inhibited the migration of Ba into the near-surface region during n -hexane ROC and effectively suppressed non-selective oxidation reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗