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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The excitation and collisional deactivation of metastable N/2P/ atoms in auroras

The concentration and altitude distribution of metastable N(2P) atoms was measured in a diffuse IBC II(+) auroral arc. The dominant N(2P) source is shown to be the dissociative excitation of N2 by electron impact with a minor contribution from the dissociative recombination of N2(+) ions. The possibility that an ion-molecule process involving atomic oxygen and vibrationally excited N2(+) ions is a significant N(2P) source is examined. Values for the proportional yield of N(+), N(2P), N(2D), and N(4S) atoms from electron-impact dissociation of N2 under optically thick conditions are given.

Zipf, E. C.↗
NASA NTRS1989

Rapid deactivation of N(2D) by O - Impact on thermospheric and mesospheric odd nitrogen

One- and two-dimensional models of thermospheric odd nitrogen are used to explore the consequences of the recently measured fast quenching of N(2D) by O. A large rate coefficient for this reaction profoundly affects the odd-nitrogen chemistry by removing N(2D) as a source of NO and increasing the concentration of N(4S), which destroys NO. The model calculations show that, as the quenching rate increases, the NO and N(2D) densities decrease, while N(4S) densities increase. Comparisons with Atmosphere Explorer and Solar Mesosphere Explorer satellite observations are made. Use of the fast quenching rate in the models causes the NO peak altitude, typically observed near 110 km, to rise to 140 km.

Fesen, C. G.↗
NASA NTRS1996

Chlorine Deactivation in the Lower Stratospheric Polar Regions during late Winter: Results from UARS

Recovery from enhanced chlorine conditions in the lower stratospheric polar regions of both hemispheres is investigated using data from the Upper Atmosphere Research Satellite (UARS). Microwave Limb Sounder (MLS) measurements of ClO within the polar vortices are used to infer ClO(sub x) (ClO + 2Cl202) abundances that are then correlated with simultaneous Cryogenic Limb Array Etalon Spectrometer (CLAES) measurements of ClON02 and Halogen Occultation Experiment (HALOE) measurements of HCl obtained starting within 5 days of the end of the MLS and CLAES high-latitude observing periods in each hemisphere. Time series of vortex-averaged mixing ratios are calculated on two potential temperature surfaces (585 K and 465 K) in the lower stratosphere for approximately month-long intervals during late winter: August 17 - September 17, 1992, in the southern hemisphere and February 12 - March 16, 1993, in the northern hemisphere. The observed mixing ratios are adjusted for the effects of vertical transport using diabatic vertical velocities estimated from CLAES tracer data. In the northern hemisphere, the decrease in ClO, is balanced on both surfaces by an increase in ClON02- In the southern hemisphere, continuing polar stratospheric cloud activity prevents ClO from undergoing sustained decline until about September 3. In contrast to the northern hemisphere, there is no significant chemical change in vortex-averaged ClON02 at 465 K, and there is an apparent decrease in ClON02 at 585 K, even after the enhanced ClO abundances have started to recede. Results from the SLIMCAT chemical transport model initialized with UARS data and run with OH + ClO yields HCl + 02 as an 8% channel suggest that the primary recovery product in the south during this time period is not ClON02, but HCl. HALOE HCl mixing ratios are extrapolated back to the time of the MLS and CLAES data. At 585 K, the chlorine budget can be made to balance by extrapolating HCl back to a value of 0.6 parts per billion by volume (ppbv) at the beginning of the study period; at 465 K, the contribution from extrapolated HCl is not sufficient to offset the loss in ClOx, and there is a slight imbalance between the decrease in reactive chlorine and the change in chlorine reservoirs. The difficulty in closing the chlorine budget in the southern hemisphere may arise from complications caused by ongoing activation, incomplete photochemical assumptions, and/or inadequate data quality.

Santee, M. L.↗
DOE OSTI2020

Deactivation of Building 9206 - A Manhattan Project Era Facility

Building 9206 at the Y-12 National Security Complex was constructed in 1944 for the Manhattan Project as a predecessor to the much larger Building 9212. The purpose of Building 9206 was to perform chemical recycle, metal production, and recover of highly enriched uranium, as well as process product from the electromagnetic separation process.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Elimination of Class-9 Hazards in Lithium-ion Recycling (Final Report)

The objective of this project was based upon the FOA request to demonstrate replication of results of the innovation to different locations. The project demonstrated battery deactivation innovations on different battery formats, chemistries, and within various industrial settings. The successful deactivation process was demonstrated on mainstream applications as well as safety-outliers, such as batteries that may have a residual charge. Success of deactivation was shown through repeated observations that various treated batteries do not exhibit thermal runaway with exposure to excessive heating or nail penetration. Deactivation processing was successfully demonstrated on batteries from private industry, public transit authorities, and military formats accessed with support of the Defense Logistics Agency (DLA). Third party analysis of deactivated batteries is ongoing through use of voucher programs available through OnTo’s Made in America Phase II Battery Recycling Prize, and OnTo’s CalTestBed award; these activities support the future special permit or declassification of deactivation treated material that has a firm foundation in results from this project. The project demonstrated the potential for a service business to perform the activities of electrolyte removal and reactivity elimination from large electric vehicle batteries in a relevant environment such as a battery testing and repackaging, or public-transit electric bus service shop. This successful project provided the first description, demonstration, and basis to teach quality control and assurance of successful battery deactivation.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2020

Carbidic Mo is the sole kinetically-relevant active site for catalytic methane dehydroaromatization on Mo/H-ZSM-5

Systematic variation of Mo/Al = {0.10, 0.25, 0.35} in Mo/H-ZSM-5 catalysts effects ~20× change of Mo-to-H + ratio during methane dehydroaromatization (DHA) reactions at steady state and on deactivating catalysts. Mo and Brønsted-acid site count, respectively enumerated by ethane hydrogenolysis probe reaction and dimethyl ether chemical titration, evolve disparately during DHA catalysis, indicating the two sites reduce in number by distinct mechanisms. Here, the deactivation of Mo/H-ZSM-5 catalytic activity is uniquely attributed to the loss of active, or accessible, Mo sites, evinced by (i) the non-selective nature of deactivation (i.e. that deactivation occurs without modification of residual active sites), (ii) invariance in product distribution from Mo/H + = 0.10–2.1, and (iii) linear correspondence between Mo-catalyzed ethane hydrogenolysis rate and active site count during DHA on deactivating samples. DHA forward rate – the intrinsic kinetic descriptor of catalyst activity – normalizes by Mo content at steady state and on deactivating catalysts with Mo/Al = 0.10–0.35 for Mo-based contact times in the range τ Mo = 0.79–44 mol Mo s mol –1 C , unequivocally establishing Mo aggregates as the sole kinetically-relevant active site on Mo/H-ZSM-5. Brønsted-acid site content over a ~40× range in τ H+ = 1.4–54 mol H+ s mol –1 C has no discernable correlation with or effect on DHA rate, methane conversion, or product distribution – demonstrating H + does not catalyze any rate- or selectivity-determining steps in the benzene formation pathway and suggesting that the benefits of zeolitic acid sites are only to disperse Mo during catalyst synthesis and, conceivably, to catalyze equilibrated reaction steps.

02 PETROLEUM↗
DOE OSTI2021

Guiding the design of oxidation-resistant Fe-based single atom alloy catalysts with insights from configurational space

The high activity and selectivity of Fe-based heterogeneous catalysts toward a variety of reactions that require the breaking of strong bonds are offset in large part by their considerable instability with respect to oxidative deactivation. While it has been shown that the stability of Fe catalysts is considerably enhanced by alloying them with precious metals (even at the single-atom limit), rational design criteria for choosing such secondary metals are still missing. Since oxidative deactivation occurs due to the strong binding of oxygen to Fe and reduction by adsorbed hydrogen mitigates the deactivation, we propose here to use the binding affinity of oxygen and hydrogen adatoms as the basis for rational design. As it would also be beneficial to use cheaper secondary metals, we have scanned over a large subset of 3d–5d mid-to late transition metal single atoms and computationally determined their effect on the oxygen and hydrogen adlayer binding as a function of chemical potential and adsorbate coverage. We further determine the underlying chemical origins that are responsible for these effects and connect them to experimentally tunable quantities. Our results reveal a reliable periodic trend wherein oxygen binding is weakened greatest as one moves right and down the periodic table. Hydrogen binding shows the same trend only at high (but relevant) coverages and otherwise tends to have its binding slightly increased in all systems. Trends with secondary metal coverage are also uncovered and connected to experimentally tunable parameters.

Hensley, Alyssa↗
DOE OSTI2024

Platinum on High-Entropy Aluminate Spinels as Thermally Stable CO Oxidation Catalysts

Thermal degradation is a leading cause of automotive catalyst deactivation. Because high-entropy oxides are uniquely stabilized at high temperatures via an increase in configurational entropy, these materials may offer new mechanisms for preventing the thermal deactivation of precious metal catalysts. In this work, we evaluated platinum loaded on simple and high-entropy aluminate spinels (MAl 2 O 4 , where M = Co, Cu, Mg, Ni, or mixtures thereof) in carbon monoxide oxidation before and after aging at 800 °C. Pt supported on all simple spinels showed significant deactivation after thermal aging compared to the fresh samples, with T 90 increasing by at least 60 °C. However, Pt on high-entropy spinels had nearly the same or better activity after aging, with T 90 increasing by only 6 °C at most. During aging and reduction, copper exsolved from the spinel supports and alloyed with platinum. This interaction promoted low temperature oxidation activity, presumably through weakened CO binding, but did not prevent deactivation. On the other hand, Co, Mg, and Ni constituents promoted stronger CO bonding, as evidenced by apparent negative order kinetics and poor activity at low temperatures. High-entropy spinels, containing a variety of active metals, displayed synergetic reactant adsorption capacity and cooperative effects with supported platinum particles, which collectively prevented thermal deactivation.

CO oxidation↗
NASA NTRS2001

Fitting Vibrational Energy Parameters to Falloff Experiments: CH3 + CH3 + He (0.6-2 Torr 200-298 K)

There are many reported experiments and theoretical calculations for the combination of methyl free radicals diluted in a non-reactive 'deactivator. At high pressure the ethane (C2H6) combination product is the sole product; with decreasing pressure the chemically activated C2H6 will decompose. The falloff in the observed rate coefficient is the result of the competition between collisional stabilization of the chemically activated CA and unimolecular decomposition. The dependence of the rate coefficient on pressure, temperature and collision properties is complex and can not be calculated from first principles. The understanding of this system is not only of fundamental importance but is relevant to the recent detection of methyl free radicals in the atmospheres of Saturn - and Neptune. The temperatures of these outer planet atmospheres are in the 140-200 K region with total pressures (predominately H2 and He) less than 0.2 Torr. Experimentally determined rate coefficients have been reported for this reaction at T = 296-906 K and T = 200-408 K mostly with argon as the deactivator. At T = 200 K only the high pressure rate coefficient has been determined. Complete falloff curves over a wide temperature range (200-1600 K) with a variety of weak collider models used to simulate argon as the deactivator have also been reported by Klippenstein and Harding (KH). More recently we have reported the experimental rate coefficients in the falloff region with helium as the deactivator at 200 and 298 K. In this paper we have used the calculated falloff curves reported by KH for argon to determine the average energy transferred per collision for helium in our recently reported experiments. Collision rates were converted using Lennard Jones parameters; the temperature dependence of this conversion factor is noted. The helium experiments were consistent with a down of approximately 100 cm (exp-1); the temperature dependence was slight. The magnitude of down and its temperature dependence will be compared to other systems with similar substrate complexity and reaction energetics.

Tardy, Dwight C.↗
NASA NTRS1992

Effect of pH on subunit association and heat protection of soybean alpha-galactosidase

Soybeans contain the enzyme alpha-galactosidase, which hydrolyzes alpha-1, 6 linkages in stachyose and raffinose to give sucrose and galactose. We have found that galactose, a competitive product inhibitor of alpha-galactosidase, strongly promotes the heat stability of the tetrameric form of the enzyme at pH 4.0 and at temperatures of up to 70 degrees C for 60 min. Stachyose and raffinose also protect alpha-galactosidase from denaturation at pH 4.0 although to a lesser extent. Glucose and mannose have little effect. At pH 7.0 the enzyme is a monomer, and galactose has no effect on the heat stability of the enzyme. In the absence of heat protection of the enzyme by added sugars, a series deactivation mechanism was found to describe the deactivation data. In comparison, a unimolecular, non-first order deactivation model applies at pH 4.0, where heat protection effects were observed. At a temperature above 60 degrees C, simple deactivation is a suitable model. The results suggest that alpha-galactosidase conformation and heat stability are directly related.

Non-NASA Center↗
DOE OSTI2023

Simulating Catalysis with Realistic Pellet Geometries Using Mesoflow: A Case Study of Catalytic Propane Dehydrogenation

We present a case study of catalytic propane dehydrogenation with our open-source multiphysics solver, Mesoflow. The solver was developed to simulate reactive flow coupled to heterogeneous catalytic reactions and deactivation in the context of complex, mesoscale geometry. The method leverages cartesian block-structured adaptive mesh refinement to capture realistic catalyst microstructural features acquired directly from X-ray computed tomography data. A kinetic model for propane dehydrogenation and catalyst deactivation was developed based on temporal analysis of products (TAP) reactor experiments. The TAP reactor experiments allow for precise characterization of intrinsic kinetic reaction steps which are implemented into Mesoflow simulations to model the spatial and temporal evolution of reactants, products, and catalyst active sites. The short-term and long-term deactivation behavior is studied by using XCT data collected from fresh and aged catalyst pellets, which exhibit different microstructural features. This study employs time-splitting algorithms to connect disparate reaction and flow timescales, enabling the simulations to achieve realistic deactivation timescales on the order of minutes while the flow time-scales for small particles (100 microns) are several milliseconds. We also introduce a flexible automated python script that writes the necessary files to construct a Mesoflow simulation from user-created chemical mechanisms. We will also introduce a few new features that are added to Mesoflow such as higher order schemes, implicit chemistry integrators and the ability to run on AMD and NVIDIA graphics-processing-units.

AMReX↗
DOE OSTI2026

Direct Observation of Elusive (DTBM‐SEGPHOS)CuH Monomer Enables Mechanistic Insights Into Hydrocupration, Aggregation, and Dynamics of Alkene Functionalization Catalysis

The bulky diphosphine DTBM-SEGPHOS is widely employed in CuH-catalyzed transformations as it provides remarkably active catalyst systems. The transient (DTBM-SEGPHOS)CuH monomer (LCuH) is the often-invoked active species. However, its instability has prevented spectroscopic characterization and mechanistic elucidation, hindering mechanistic understanding. We report low-temperature NMR spectroscopic characterization of LCuH, enabling quantitative kinetic analysis of the stoichiometric hydrocupration and catalytic hydroboration of cyclopentene, as well as the structural identification of two CuH clusters. LCuH inserts cyclopentene at −43°C, reaffirming its high reactivity toward olefins. LCuH deactivates to form L 2 Cu 3 H 3 and L 2 Cu 4 H 4 clusters, in which LCuH dimerization initiates aggregation. Kinetic analysis of reactions of unactivated alkenes indicates that competing on-cycle alkene hydrocupration and LCuH dimerization impact performance, as catalyst deactivation and turnover occur on comparable timescales. Structure–activity analysis using atomistic simulations shows that the steric profile of DTBM-SEGPHOS increases the CuH dimerization barrier by ∼7.7 kcal mol−1 compared to that of SEGPHOS, rationalizing the unique ability of DTBM-SEGPHOS to stabilize a reactive monomer for hydrocupration of broader alkene substrates. These findings illustrate the fundamental design principle that steric control of aggregation governs CuH catalyst performance, explaining both the exceptional activity of (DTBM-SEGPHOS)CuH and the limitations imposed by competing deactivation.

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

Remarkable self-degradation of Cu/SAPO-34 selective catalytic reduction catalysts during storage at ambient conditions

A model Cu/SAPO-34 SCR catalyst with all Cu species maintained as isolated Cu(II) ions is synthesized herein. Following lengthy storage on the shelf under ambient conditions, this catalyst completely and irreversibly deactivates upon any heat treatments above ~100 °C. Via detailed characterizations with surface area/pore volume analysis, XRD, H 2 -TPR, and 27 Al, 29 Si and 31 P solid-state NMR, as well as continuous wave and pulsed EPR studies, it is concluded that over the course of storage, the SCR active sites [Cu(OH)] + and Brønsted acid sites ≡Si-O(H)-Al≡ are attacked by H 2 O molecules trapped in the SAPO-34 framework pores, and undergo hydrolysis to form copper hydroxide and terminal Al sites. Upon thermal treatment, these species interact with each other to form copper-aluminate-like species, leading to irreversible deactivation of this catalyst. This deactivation mechanism does not require or necessarily lead to extensive degradation (i.e., crystallinity loss) of the SAPO-34 support.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗