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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Numerical simulation of a low-emission gas turbine combustor using KIVA-II

A modified version of the KIVA-II code was used to obtain a multidimensional numerical solution for the turbulent two-phase chemically reacting flows inside a staged turbine combustor (STC). The STC under consideration is equipped with an advanced airblast fuel nozzle and encompasses a fuel nozzle (FN), a rich-burn (RB) zone, a converging connecting pipe, a quick-quench (QQ) zone, a diverging connecting pipe, and a lean-combustion (LC) zone. The STC was divided into two subsystems, namely, FN/RB zone and QQ/LC zones, and the numerical solutions were obtained separately for each subsystem. Preliminary data characterize the major features of the flow and temperature fields inside the STC. Information on velocity, temperature, and some critical species in the FN/RB zone is presented. In the QQ/LC zones, formation of the co- and counter-rotating bulk flow and the sandwiched-ring-shaped temperature field can be clearly seen. The calculations of the mass-weighted standard deviation and the pattern factor of temperature indicated that the mixing performance of the STC is very promising.

Yang, S. L.↗
NASA NTRS1992

Interfacial stability of CoSi2/Si structures grown by molecular beam epitaxy

The stability of CoSi2/Si interfaces was examined in this study using columnar silicide structures grown on (111) Si substrates. In the first set of experiments, Co and Si were codeposited using MBE at 800 C and the resulting columnar silicide layer was capped by epitaxial Si. Deposition of Co on the surface of the Si capping layer at 800 C results in the growth of the buried silicide columns. The buried columns grow by subsurface diffusion of the deposited Co, suppressing the formation of surface islands of CoSi2. The column sidewalls appear to be less stable than the top and bottom interfaces, resulting in preferential lateral growth and ultimately in the coalescence of the columns to form a continuous buried CoSi2 layer. In the second set of experiments, annealing of a 250 nm-thick buried columnar layer at 1000 C under a 100 nm-thick Si capping layer results in the formation of a surface layer of CoSi2 with a reduction in the sizes of the CoSi2 columns. For a sample having a thicker Si capping layer the annealing leads to Ostwald ripening producing buried equiaxed columns. The high CoSi2/Si interfacial strain could provide the driving force for the observed behavior of the buried columns under high-temperature annealing.

George, T.↗
NASA NTRS1995

Geochemical constraints on chemolithoautotrophic reactions in hydrothermal systems

Thermodynamic calculations provide the means to quantify the chemical disequilibrium inherent in the mixing of reduced hydrothermal fluids with seawater. The chemical energy available for metabolic processes in these environments can be evaluated by taking into account the pressure and temperature dependence of the apparent standard Gibbs free energies of reactions in the S-H2-H2O system together with geochemical constraints on pH, activities of aqueous sulfur species and fugacities of H2 and/or O2. Using present-day mixing of hydrothermal fluids and seawater as a starting point, it is shown that each mole of H2S entering seawater from hydrothermal fluids represents about 200,000 calories of chemical energy for metabolic systems able to catalyze H2S oxidation. Extrapolating to the early Earth, which was likely to have had an atmosphere more reduced than at present, shows that this chemical energy may have been a factor of two or so less. Nevertheless, mixing of hydrothermal fluids with seawater would have been an abundant source of chemical energy, and an inevitable consequence of the presence of an ocean on an initially hot Earth. The amount of energy available was more than enough for organic synthesis from CO2 or CO, and/or polymer formation, indicating that the vicinity of hydrothermal systems at the sea floor was an ideal location for the emergence of the first chemolithoautotrophic metabolic systems.

Shock, Everett L.↗
NASA NTRS2000

Meteors: A Delivery Mechanism of Organic Matter to The Early Earth

All potential exogenous pre-biotic matter arrived to Earth by ways of our atmosphere, where much material was ablated during a luminous phase called 1. meteors" in rarefied flows of high (up to 270) Mach number. The recent Leonid showers offered a first glimpse into the elusive physical conditions of the ablation process and atmospheric chemistry associated with high-speed meteors. Molecular emissions were detected that trace a meteor's brilliant light to a 4,300 K warm wake rather than to the meteor's head. A new theoretical approach using the direct simulation by Monte Carlo technique identified the source-region and demonstrated that the ablation process is critical in the heating of the meteor's wake. In the head of the meteor, organic carbon appears to survive flash heating and rapid cooling. The temperatures in the wake of the meteor are just right for dissociation of CO and the formation of more complex organic compounds. The resulting materials could account for the bulk of pre-biotic organic carbon on the early Earth at the time of the origin of life.

Jenniskens, Peter↗
NASA NTRS2005

Low NO(x) Combustor Development

The goal of these efforts was the development of an ultra-low emissions, lean-burn combustor for the High Speed Civil Transport. The HSCT Mach 2.4 FLADE C1 Cycle was selected as the baseline engine cycle. A preliminary compilation of performance requirements for the HSCT combustor system was developed. The emissions goals of the program, baseline engine cycle, and standard combustor performance requirements were considered in developing the compilation of performance requirements. Seven combustor system designs were developed. The development of these system designs was facilitated by the use of spreadsheet-type models which predicted performance of the combustor systems over the entire flight envelope of the HSCT. A chemical kinetic model was developed for an LPP combustor and employed to study NO(x) formation kinetics, and CO burnout. These predictions helped to define the combustor residence time. Five fuel-air mixer concepts were analyzed for use in the combustor system designs. One of the seven system designs, one using the Swirl-Jet and Cyclone Swirler fuel-air mixers, was selected for a preliminary mechanical design study.

Kastl, J. A.↗
NASA NTRS2017

Overview of SPRITE: Saturn Probe Interior and aTmosphere Explorer Concept

The Saturn PRobe Interior and aTmosphere Explorer (SPRITE) mission concept targets high-priority Planetary Science Decadal Survey science objectives. This mission concept would deliver the SPRITE entry probe into the Saturn atmosphere to obtain in situ measurements of elemental abundances and isotopic ratios, which would help distinguish the role Saturn played in the solar system formation and co-evolution of other planets. An Atmospheric Structure Investigation sensor package on the entry probe would provide in situ measurements of the pressure/temperature and wind structure below the cloud-tops, and a Quadrupole Mass Spectrometer and Tunable Laser Spectrometer suite would determine the composition of Saturn’s atmosphere. The SPRITE mission concept described in this paper uses a solar-powered carrier-relay spacecraft to deliver the battery-powered entry probe to Saturn after a 10-year Venus-Earth-Earth gravity-assist trajectory, and then relays the probe data back to Earth during the carrier-relay spacecraft Saturn flyby. A high-heritage design approach is implemented for the flight elements to minimize technical risk and enable successful return of this high-value science data.

Cuddy, Cavan↗
DOE OSTI2024

Room‐Temperature Formate Ester Transfer Hydrogenation Enables an Electrochemical/Thermal Organometallic Cascade for Methanol Synthesis from CO 2

Abstract The reduction of CO 2 to synthetic fuels is a valuable strategy for energy storage. However, the formation of energy‐dense liquid fuels such as methanol remains rare, particularly under low‐temperature and low‐pressure conditions that can be coupled to renewable electricity sources via electrochemistry. Here, a multicatalyst system pairing an electrocatalyst with a thermal organometallic catalyst is introduced, which enables the reduction of CO 2 to methanol at ambient temperature and pressure. The cascade methanol synthesis proceeds via CO 2 reduction to formate by electrocatalyst [Cp*Ir(bpy)Cl] + (Cp*=pentamethylcyclopentadienyl, bpy=2,2′‐bipyridine), Fischer esterification of formate to isopropyl formate catalyzed by trifluoromethanesulfonic acid (HOTf), and thermal transfer hydrogenation of isopropyl formate to methanol facilitated by the organometallic catalyst (H‐PNP)Ir(H) 3 (H‐PNP=HN(C 2 H 4 P i Pr 2 ) 2 ). The isopropanol solvent plays several crucial roles: activating formate ion as isopropyl formate, donating hydrogen for the reduction of formate ester to methanol via transfer hydrogenation, and lowering the barrier for transfer hydrogenation through hydrogen bonding interactions. In addition to reporting a method for room‐temperature reduction of challenging ester substrates, this work provides a prototype for pairing electrochemical and thermal organometallic reactions that will guide the design and development of multicatalyst cascades.

Fernández, Sergio [Department of Chemistry Univers↗
DOE OSTI2024

Room-Temperature Formate Ester Transfer Hydrogenation Enables an Electrochemical/Thermal Organometallic Cascade for Methanol Synthesis from CO 2

The reduction of CO 2 to synthetic fuels is a valuable strategy for energy storage. However, the formation of energy-dense liquid fuels such as methanol remains rare, particularly under low-temperature and low-pressure conditions that can be coupled to renewable electricity sources via electrochemistry. Here, in this study, a multicatalyst system pairing an electrocatalyst with a thermal organometallic catalyst is introduced, which enables the reduction of CO 2 to methanol at ambient temperature and pressure. The cascade methanol synthesis proceeds via CO 2 reduction to formate by electrocatalyst [Cp*Ir(bpy)Cl] + (Cp*=pentamethylcyclopentadienyl, bpy=2,2'-bipyridine), Fischer esterification of formate to isopropyl formate catalyzed by trifluoromethanesulfonic acid (HOTf), and thermal transfer hydrogenation of isopropyl formate to methanol facilitated by the organometallic catalyst (H-PNP)Ir(H) 3 (H-PNP=HN(C 2 H 4 P i Pr 2 ) 2 ). The isopropanol solvent plays several crucial roles: activating formate ion as isopropyl formate, donating hydrogen for the reduction of formate ester to methanol via transfer hydrogenation, and lowering the barrier for transfer hydrogenation through hydrogen bonding interactions. In addition to reporting a method for room-temperature reduction of challenging ester substrates, this work provides a prototype for pairing electrochemical and thermal organometallic reactions that will guide the design and development of multicatalyst cascades.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Hydrosilyation of CO 2 using a silatrane hydride: structural characterization of a silyl formate compound

The silatrane hydride compound, [N(CH 2 CH 2 O) 3 ]SiH, reacts with CO 2 in the presence of the [tris(2-pyridylthio)methyl]zinc hydride complex, [Tptm]ZnH, to afford the silyl formate and methoxide derivatives, [N(CH 2 CH 2 O) 3 ]SiO 2 CH and [N(CH 2 CH 2 O) 3 ]SiOCH 3 . The molecular structure of [N(CH 2 CH 2 O) 3 ]SiO 2 CH has been determined by X-ray diffraction, thereby demonstrating that the formate ligand adopts a distal conformation in which the uncoordinated oxygen atom resides with a trans-like disposition relative to silicon. In conclusion, density functional theory calculations indicate that the atrane motif of [N(CH 2 CH 2 O) 3 ]SiO 2 CH is flexible, such that the energy of the molecule changes relatively little as the Si···N distance varies over the range 2.0–3.0 Å.

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

Co-Hydrotreatment of Yellow Greases and the Water-Insoluble Fraction of Pyrolysis Oil. Part I: Experimental Design to Increase Kerosene Yield and Reduce Coke Formation

Here, this paper reports the co-hydrotreatment of Biomass Technology Group commercial pyrolysis oil water-insoluble (WIS) phase (also known as pyrolytic lignin) and yellow greases (waste cooking oil), aiming to produce sustainable aviation fuels (SAFs). We use a sulfided NiMo/Al 2 O 3 blend with 16 wt % WIS and a central composite experimental design to identify processing conditions increasing kerosene yield and reducing coke formation. The input variables were: (1) reaction temperature (320, 350, and 380 °C), (2) initial hydrogen pressure (5, 6, and 7 MPa), and (3) amount of catalyst (0.7, 1.0, and 1.3 g). The hydrotreated oily phases were distilled to obtain gasoline (<150 °C), kerosene (150–250 °C), diesel (250–350 °C), and residual oil (>350 °C). The reaction temperature is the main factor affecting the yield of gaseous, solid, and liquid products. Meanwhile, a higher initial hydrogen pressure and catalyst loading increased the yield of kerosene and other distillates and decreased the coke formation. A high temperature correlated with a lower content of oxygenates in kerosene cuts. Based on our experimental results, we propose to conduct hydrotreatment studies at 380 °C, initial H 2 pressure of 7 MPa, and 1.3 g of catalyst. Under the identified conditions, it was possible to improve the kerosene yield to more than 20 wt % and reduce the yield of coke to close to 2.0 wt %. The chemical composition and fuel properties of the gasoline, kerosene, and diesel cuts were thoroughly analyzed. The content of aromatics and phenols in the kerosene fraction produced at the conditions identified in this project exceeded the recommended values for SAFs. New strategies (such as blending and more intense hydrotreatment to remove oxygenated compounds) need to be implemented to reduce the content of these molecules in our final product.

09 BIOMASS FUELS↗
DOE OSTI2024

Linear Free Energy Relationships Associated with Hydride Transfer From [(6,6'-R 2 -bpy)Re(CO) 3 H]: A Cautionary Tale in Identifying Hydrogen Bonding Effects in the Secondary Coordination Sphere

Here, six rhenium hydride complexes, [(6,6'-R 2 -bpy)Re(CO) 3 H] (bpy = 2,2'-bipyridine, R = OEt, OMe, NHMe, Me, F, Br), were synthesized. These complexes insert CO 2 to form rhenium formate complexes of the type [(6,6'-R 2 -bpy)Re(CO) 3 {OC(O)H}]. All the rhenium formate species were characterized using X-ray crystallography, which revealed that the bpy ligand is not coplanar with the metal coordination plane containing the two nitrogen donors of the bpy ligand but tilted. A solid-state structure of [(6,6'-Me 2 -bpy)Re(CO) 3 H] determined using MicroED also featured a tilted bpy ligand. The kinetics of CO 2 insertion into complexes of the type [(6,6'-R 2 -bpy)Re(CO) 3 H] were measured experimentally and the thermodynamic hydricities of [(6,6'-R 2 -bpy)Re(CO) 3 H] species were determined using theoretical calculations. A Brønsted plot constructed using the experimentally determined rate constants for CO 2 insertion and the calculated thermodynamic hydricities for [(6,6'-R 2 -bpy)Re(CO) 3 H] revealed a linear free energy relationship (LFER) between thermodynamic and kinetic hydricity. This LFER is different to the previously determined relationship for CO 2 insertion into complexes of the type [(4,4'-R 2 -bpy)Re(CO) 3 H]. At a given thermodynamic hydricity, CO 2 insertion is faster for complexes containing a 6,6'-substituted bpy ligand. This is likely in part due to the tilting observed for systems with 6,6'-substituted bpy ligands. Notably, the 6,6'-(NHMe) 2 -bpy ligand could in principle stabilize the transition state for CO 2 insertion via hydrogen bonding. This work shows that if only the rate of CO 2 insertion into [(6,6'-(NHMe) 2 -bpy)Re(CO) 3 H] is compared to [(4,4'-R 2 -bpy)Re(CO) 3 H] systems, the increase in rate could be easily attributed to hydrogen bonding, but in fact all 6,6'-substituted systems lead to faster than expected rates.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Growth, sintering, and chemical states of Co supported on reducible CeO 2 (111) thin films: The effects of the metal coverage and the nature of the support

The growth, sintering, and interaction of cobalt with ceria were studied under ultrahigh vacuum conditions by vapor-deposition of Co onto well-defined CeOx(111) (1.5 < x < 2) thin films grown on Ru(0001). Charge transfer from Co to ceria occurs upon deposition of Co on CeO 1.96 and partially reduced CeO 1.83 at 300 K. X-ray photoelectron spectroscopy studies show that Co is oxidized to Co 2+ species at the cost of the reduction of Ce 4+ to Ce 3+ , at a lesser extent on reduced ceria. Co 2+ is the predominant species on CeO 1.96 at low Co coverages (e.g., ≤0.20 ML). The ratio of metallic Co/Co 2+ increases with the increase in the Co coverage. However, both metallic Co and Co 2+ species are present on CeO 1.83 even at low Co coverages with metallic Co as the major species. Scanning tunneling microscopy results demonstrate that Co tends to wet the CeO 1.96 surface at very low Co coverages at room temperature forming one-atomic layer high structures of Co–O–Ce. The increase in the Co coverage can cause the particle growth into three-dimensional structures. The formation of slightly flatter Co particles was observed on reduced CeO 1.83 . In comparison with other transition metals including Ni, Rh, Pt, and Au, our studies demonstrate that Co on ceria exhibits a smaller particle size and higher thermal stability, likely arising from strong metal–support interactions. The formed particles upon Co deposition at 300 K are present on the ceria surface after heating to 1000 K. The Co–ceria interface can be tuned by varying the Co metal coverage, the annealing temperature, and the nature of the ceria surface.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Directing CO 2 electroreduction pathways for selective C 2 product formation using single-site doped copper catalysts

Manipulating the selectivity-determining step in post-C–C coupling is crucial for enhancing C 2 product specificity during electrocatalytic CO 2 reduction, complementing efforts to boost rate-determining step kinetics. Here we highlight the role of single-site noble metal dopants on Cu surfaces in influencing C–O bond dissociation in an oxygen-bound selectivity-determining intermediate, steering post-C–C coupling toward ethylene versus ethanol. Integrating theoretical and experimental analyses, we demonstrate that the oxygen binding strength of the Cu surface controls the favorability of C–O bond scission, thus tuning the selectivity ratio of ethylene-to-ethanol. The Rh-doped Cu catalyst with optimal oxygen binding energy achieves a Faradaic efficiency toward ethylene of 61.2% and an ethylene-to-ethanol Faradaic efficiency ratio of 4.51 at –0.66 V versus RHE (reversible hydrogen electrode). Integrating control of both rate-determining and selectivity-determining steps further raises ethylene Faradaic efficiency to 68.8% at 1.47 A cm -2 in a tandem electrode. Our insights guide the rational design of Cu-based catalysts for selective CO 2 electroreduction to a single C 2 product.

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

Surface‐modified Ag@Ru‐P25 for photocatalytic CO 2 conversion with high selectivity over CH 4 formation at the solid–gas interface

Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO 2 reduction to solar fuels. A surface-modified Ag@Ru-P25 photocatalyst with H 2 O 2 treatment was designed in this study to convert CO 2 and H 2 O vapor into highly selective CH 4 . Ru doping followed by Ag nanoparticles (NPs) cocatalyst deposition on P25 (TiO 2 ) enhances visible light absorption and charge separation, whereas H 2 O 2 treatment modifies the surface of the photocatalyst with hydroxyl (–OH) groups and promotes CO 2 adsorption. High-resonance transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst, while thermogravimetric analysis, CO 2 adsorption isotherm, and temperature programmed desorption study were performed to examine the significance of H 2 O 2 treatment in increasing CO 2 reduction activity. The optimized Ag 1.0 @Ru 1.0 -P25 photocatalyst performed excellent CO 2 reduction activity into CO, CH 4 , and C 2 H 6 with a ~95% selectivity of CH 4 , where the activity was ~135 times higher than that of pristine TiO 2 (P25). For the first time, this work explored the effect of H 2 O 2 treatment on the photocatalyst that dramatically increases CO 2 reduction activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Anodic Conversion of Cyclohexane, Methylcyclohexane, and 2-Propanol: Towards a Regenerable Liquid-Fed Fuel Cell

Liquid Organic Hydrogen Carriers (LOHCs) are promising for hydrogen and energy storage but require endothermic catalytic dehydrogenation. An alternative approach is a regenerable liquid-fed fuel cell which spontaneously converts an organic carrier from its hydrogen-rich to hydrogen-lean form while generating electrical power. The anodic electrooxidation of cyclohexane, methylcyclohexane and 2-propanol in a high temperature polybenzimidazole/phosphoric acid (PBI/PA) PEM fuel cell was investigated along with a quantitative analysis of reaction products. Cyclohexane and methylcyclohexane were predominantly converted to CO 2 with only a trace formation of the corresponding aromatic and cyclic olefin byproducts. This near-to-complete oxidation of the fuels is in sharp contrast to previous reports of a selective conversion of cyclohexane to benzene, with no CO 2 byproducts. In experiments with 2-propanol, acetone was produced, with diisopropylether, propylene and CO 2 as only minor side products. However, the extent of CO 2 formation greatly increased at higher current densities.

25 ENERGY STORAGE↗
DOE OSTI2024

On Caprock Seal Integrity of Tuscaloosa Mudstone at Cranfield, MS (USA), CO 2 Injection Site

Saline formations deep underground are among the most promising targets for large-scale geologic carbon storage. The caprock seal integrity evaluation is an important component of commercial-scale CO 2 sequestration projects. Measurements of the porosity and permeability of mudstone samples from the NETL-supported Cranfield Project were performed using a helium porosimeter and a core flow apparatus, before and after exposure in a CO 2 -saturated brine environment. The permeability of the core samples rapidly decreased with the increase in confining pressure and did not fully recover after decompression. On the other hand, exposure to CO 2 led to an increase in the permeability by at least an order of magnitude. The porosity changes after the exposure were not substantial. The post-exposure increase in permeability was subsequently offset by its rapid decrease during the higher-pressure confinement. Extrapolation of the observed permeability trends to in situ reservoir conditions suggests that Tuscaloosa mudstone can effectively serve as a natural seal.

58 GEOSCIENCES↗
DOE OSTI2021

Enhanced Catalysis under 2D Silica: A CO Oxidation Study

Interfacially confined microenvironments have recently gained attention in catalysis, as they can be used to modulate reaction chemistry. The emergence of a 2D nanospace at the interface between a 2D material and its support can promote varying kinetic and energetic schemes based on molecular level confinement effects imposed in this reduced volume. We report on the use of a 2D oxide cover, bilayer silica, on catalytically active Pd(111) undergoing the CO oxidation reaction. We “uncover” mechanistic insights about the structure-activity relationship with and without a 2D silica overlayer using in situ IR and X-ray spectroscopy and mass spectrometry methods. We find that the CO oxidation reaction on Pd(111) benefits from confinement effects imposed on surface adsorbates under 2D silica. Finally, this interaction results in a lower and more dispersed coverage of CO adsorbates with restricted CO adsorption geometries, which promote oxygen adsorption and lay the foundation for the formation of a reactive surface oxide that produces higher CO 2 formation rates than Pd alone.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Formate-Induced Dissolution and Reprecipitation of a Copper Electrocatalyst during Electrochemical CO 2 Reduction Reaction

Catalyst size, morphology, and crystal structure play crucial roles in determining the activity and selectivity of electrochemical CO 2 reduction reactions, which are known to change during the reaction process. A comprehensive understanding of how, when, and why these parameters evolve under operational conditions is essential for developing stable, efficient, and selective catalysts. In this study, we reveal that formate, one of the reaction products, contributes to the degradation of copper catalysts through a ligand-assisted dissolution mechanism. Utilizing in situ electrochemical atomic force microscopy and ex-situ scanning and transmission electron microscopies, we observed a significant reduction in the size of copper nanoparticles, which decreased from over 30 nm to less than 10 nm in diameter within 60 min of CO 2 RR. The temporal production of formate correlated with the particle size changes. Furthermore, analysis of the electrolyte using inductively coupled plasma optical emission spectroscopy confirmed the dissolution of copper nanoparticles. Control experiments involving various reaction products (H 2 , CO, and HCOO – ) demonstrated that formate significantly promotes copper dissolution, thereby highlighting its role in the ligand-assisted dissolution mechanism of copper electrocatalysts. In conclusion, our findings provide critical insights into copper catalyst behavior during electrochemical CO 2 reduction, facilitating the design of more resilient and effective electrocatalysts.

Catalysts↗