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At least 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Positions and Intensities in the 3v2/v2+v4 Vibrational System of 14NH3 Near 4 micron meters

Ammonia is the fourth most abundant constituent in the atmospheres of Jupiter and Saturn, after hydrogen, helium and methane. This relative abundance is attested by the presence in the infrared planetary spectra of many absorption features observed in the range of fundamental bands and also in the higher bands. Reported are experimental line positions and intensities of selected ammonia bands.

ammonia Jupiter Saturn spectroscopy planetary gass↗
NASA NTRS1994

NH(sub 3), H(sub 2)S, and the Radio Brightness Temperature Spectra of the Giant Planets

Recent radio interferometer observations of Neptune enable comparisons of the radio brightness temperature (T(sub b)) spectra of all four giant planets. The data shown are collected from many observers. Spectra of Jupiter, Saturn, and Neptune share certain gross characteristics. Ammonia is known to be an important tropospheric constituent at Jupiter and Saturn. Its signature on the Jovian spectrum is obvious, while at Saturn it is a bit more subdued. Uranus' T(sub b) spectrum does not fit the same pattern. One possible cause for the apparent ammonia depletion has been offered. That is that a superabundance of H(sub 2)S could react out most of the NH(sub 3). The presence of the H(sub 2)S was postulated as there is no direct observational evidence of H(sub 2)S, which has not yet been detected at any of the giant planets. It is merely the most likely candidate to deplete NH(sub 3).Some researchers suggest a significant H(sub 2)S superabundance at Neptune also. Some researchers suggest that this H(sub 2)S may be the major source of cm opacity in Neptune's upper troposphere, rather than the NH(sub 3) that had been suggested earlier.

hydrogen sulfide spectra opacity troposphere giant↗
NASA NTRSDate not supplied

Reactor Parametric Assessments for Alternative Propellant Nuclear Thermal Propulsion Engines

This work focuses on the implications of alternative working fluids for nuclear thermal propulsion (NTP) reactors. To perform this analysis, NASA’s Testing Reference Design (TRD) is altered using parametric studies with selected alternative propellants to determine the reactor modifications required to enable an operable system. This research investigates ammonia, water, methane, helium, and enriched diborane as feasible options to enable a specific impulse (𝐼 𝑠𝑝 ) greater than the chemical propulsion alternatives. Frozen and dissociated 𝐼 𝑠𝑝 for each propellant is shown for variable chamber temperature conditions. Geometrical sensitivities are performed to observe the impact on the neutron multiplication factor (k eff ), system mass, and HALEU loading. Control drum worth curves are included for 5- degree increments of rotation. The base TRD configuration does not enable a critical system for ammonia and enriched diborane, thus these propellants will be highlighted in the final results. Equivalent study results for hydrogen will be included as a point of comparison to the performance of the other options.

Nuclear Thermal Propulsion↗
NASA NTRSDate not supplied

Reactor Parametric Assessments for Alternative Propellant Nuclear Thermal Propulsion Engines

This work focuses on the implications of alternative working fluids for nuclear thermal propulsion (NTP) reactors. To perform this analysis, NASA’s Testing Reference Design (TRD) is altered using parametric studies with selected alternative propellants to determine the reactor modifications required to enable an operable system. This research investigates ammonia, water, methane, helium, and enriched diborane as feasible options to enable a specific impulse (Isp) greater than the chemical propulsion alternatives. Frozen and dissociated Isp for each propellant is shown for variable chamber temperature conditions. Geometrical sensitivities are performed to observe the impact on the neutron multiplication factor (keff), system mass, and HALEU loading. Control drum worth curves are included for 5- degree increments of rotation. The base TRD configuration does not enable a critical system for ammonia and enriched diborane, thus these propellants will be highlighted in the final results. Equivalent study results for hydrogen will be included as a point of comparison to the performance of the other options.

Nuclear Thermal Propulsion↗
DOE OSTI2018

Base Treatment for Uranium Immobilization at DOE's Hanford Site - 18279

Ammonia gas injection is currently being field tested for uranium remediation in the vadose zone at the Department of Energy's Hanford site in Washington State. U is a significant risk driver for the site because of its high mobility in the subsurface and the significant mass released due to Manhattan Project activities. In this research, we conducted laboratory batch experiments to evaluate the changes in mobility of U with different base treatments. Based on our current body of work, base treatment is a promising technique for U immobilization with ammonia gas being the optimal choice because (1) it increases partitioning coefficients for U and results in significant removal from the aqueous phase and (2) it does not add liquid to the vadose zone which could initially increase the flux of U into groundwater. (authors)

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

Mineral Dissolution upon Alkaline Treatment and Variable Redox Conditions

Over 200.000 kg of uranium released to vadose zone from historic leaks and improper disposal of wastes from plutonium production. U highly mobile due to presence of carbonates and oxidizing conditions with partition coefficients k{sub d} of 0.11-8 mL/g at pH 8. Ammonia (NH{sub 3}) gas injection investigated as an in situ remediation technique that will not introduce additional liquid to the subsurface. Objectives: Understand the impact of remediation with base injection on geochemical process in Hanford site vadose zone. Understand effects of different base treatments on mineral dissolution. Results: - incongruent dissolution based on mineral stoichiometry: if ratio = 1 congruent dissolution occurs, if ratio <1.0 greater leaching of Si and Al and incongruent dissolution occurs. Conclusions: incongruent dissolution occurred for both alkaline treatments and redox conditions across all minerals. By 1440 hr. all normalised Al:Si ratios were <1 representing less [Al]{sub aq} and suggesting formation of secondary Al precipitates as a function of time. [Si]{sub aq} increased and [Al]{sub aq} decreased with increasing contact time with both alkaline treatments. NaOH dissolved slightly more than NH{sub 4}OH especially for [Al]{sub aq} in all investigated minerals. No clear trend for muscovite and montmorillonite for redox conditions but slightly greater Si dissolved under anaerobic conditions for illite. Ammonia gas injection increases the pH and dissolves aluminosilicate minerals in the vadose zone. U is likely to coprecipitate with secondary minerals forming at elevated pH and as the system reequilibrates at natural neutral pH. Further, U solids may be coated with low solubility, secondary precipitates.

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

Respirator Cartridge Performance on Mixed Vapors from Hanford Tank Headspaces and Exhausters - 20427

Between 2016 and 2018, the Hanford Tank Operations Contractor - Washington River Protection Solutions (WRPS) - conducted a series of tests of air-purifying respirator (APR) chemical cartridges commonly used at Hanford tank farms to determine the period of time for which the cartridges would provide adequate performance when used in APRs and powered-air-purifying respirators (PAPRs) to protect workers when exposed to a mixture of vapors exiting tank headspaces. Although cartridge manufacturers provide service life estimating tools for individual chemical compounds, the projected performance of these cartridges on complex vapor mixtures is not available, and the adequacy of APRs for tank farm applications represents an important workforce concern. The Occupational Safety and Health Administration identifies cartridge testing as a valid approach for establishing cartridge service life. The primary function of the WRPS Cartridge Test Program was to obtain objective data to determine service lives for the APR and PAPR cartridges used at Hanford tank farms. WRPS contracted with Pacific Northwest National Laboratory to analyze the test data and offer an independent analysis of and recommendations based on respirator cartridge performance. A total of 28 APR and 10 PAPR cartridge tests were conducted between 2016 and 2018 on 12 different tank headspaces and tank farm exhauster slipstreams. Two APR cartridges from SCOTT (now 3M) and two PAPR cartridges from MSA Safety, Inc. and 3M were evaluated using a cartridge testing system specifically designed to measure and monitor test conditions and sample cartridge inlet and outlet vapor streams for important chemical compounds. Testing focused on analysis of approximately 61 tank vapor chemicals of potential concern (COPCs) that have been previously detected in tank vapors at levels above 10% of their occupational exposure limits (OELs). Each test was conducted over 16 hours of run time. Evidence of chemical breakthrough was assessed by comparing inlet and outlet COPC concentrations over the duration of each test. The breakthrough threshold was normally defined as exceeding 10% of the compounds OEL at the cartridge outlet. Ammonia breakthrough was observed in a majority of the cartridge tests and occurred earlier than breakthrough of any other chemical compound. Several other COPCs did exhibit breakthrough behavior, including mercury, 1,3-butadiene, furan, 2,5 dihydrofuran, and N-nitrosodimethylamine (NDMA), but only in a very limited number of cartridge tests and only after ammonia breakthrough had occurred. In addition, tests results suggest that breakthrough of some of these COPCs may have been affected by competition with and breakthrough of other non-COPC organics, such as ethanol and acetone, with substantially lower toxicological hazard. Comparison of cartridge manufacturers' service life estimates with the experimentally derived breakthrough times indicates that manufacturers' estimates are generally conservative, even in the presence of the complex mixed vapor streams experienced in these tests. With consideration of appropriate safety margins, these results provide valuable insights on cartridge performance to inform industrial hygiene professionals in establishing appropriate cartridge change-out schedules for APR and PAPR use in the Hanford tank farms. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Impact of Advances in Anion Exchange Membranes and Ionomers on Alkaline Fuel Cells

Abstract The operation of low‐temperature electrochemical energy conversion systems (fuel cells, electrolyzers) at high pH values is of perennial interest due to the possibility of moving away from expensive platinum group metal catalysts and reducing cost. Historically, the anion exchange membranes (AEMs) and ionomers have been hampered by performance (ionic conductivity, mechanical strength) and chemical stability issues. In this context, select developments over the past decade in alternate AEM chemistries, water management methods, and production of membrane electrode assemblies (MEAs) that have enabled a significant leap in performance of alkaline fuel cells are examined. These developments are linked to performance improvements in alkaline H 2 /O 2 fuel cells and also consider developments in alkaline fuel cells using nitrogen‐containing fuels (ammonia, hydrazine), carbon‐containing fuels (alcohols, glycols), and boron‐containing fuels (sodium borohydride, ammonia borane). Finally, current challenges and bottlenecks are identified, and potential solutions are proposed.

Chemistry↗
DOE OSTI2016

Fe 3 O 4 Nanoparticles Anchored on Carbon Serve the Dual Role of Catalyst and Magnetically Recoverable Entity in the Aerobic Oxidation of Alcohols

Carbon supported γ-Fe2O3 nanoparticle (γ-Fe2O3/C) possessing both superparamagnetism and activating molecular oxygen properties were prepared by an ammonia-assisted precipitation method. It could catalyze the selective oxidation of various benzyl alcohols with air as oxidant source, and could be easily recycled with an external magnet separation. The correlation between the intrinsic properties of γ-Fe2O3 nanoparticles and the catalytic performance was investigated with a series of characterizations. It shows that the oxidation state of γ-Fe2O3 nanoparticles were facile to be changed, which should be related to its inverse spinel type crystal structure with vacant cation sites. These γ-Fe2O3 nanoparticles should be the active sites and responsible for the high activity of γ-Fe2O3/C in the air oxidation of alcohols. The formation of γ-Fe2O3 nanoparticle was controlled by precipitation agent and carbon support. Using ammonia ethanol solution as precipitation agent, the hydrolysis rate of iron species could be decreased. The surface functional groups of carbon support could act as chelating sites for iron species, controlling the nucleation and growth of the γ-Fe2O3 nanoparticles in the preparation process. Dr. Xiang Wang gratefully acknowledges the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division for the support of this work.

alcohol oxidation↗
DOE OSTI2024

NO Reduction with CO on Low‐loaded Platinum‐group Metals (Rh, Ru, Pd, Pt, and Ir) Atomically Dispersed on Ceria

Abstract Low‐loaded platinum‐group single‐atom catalysts on CeO 2 (M 1 /CeO 2 ) were synthesized via high‐temperature atom trapping (AT) and tested for the NO+CO reaction under dry and wet conditions. The activity of these catalysts for NO+CO reaction follows the order Rh>Pd≈Ru>Pt>Ir. For Rh, Ru, and Pd single‐atom catalysts, the N 2 O byproduct is formed but not clearly observed in Ir and Pt cases, which may result from the higher reaction temperature (>200 °C) required for Pt and Ir catalysts. The presence of water can promote the activity of these M 1 /CeO 2 catalysts for the NO+CO reaction. Under wet conditions, significant NH 3 formation occurred during the reaction, which is due to the co‐existence of water‐gas‐shift reaction on these catalysts. Compared with Pt, Pd and Ir, the Rh and Ru single‐atom catalysts show higher selectivity to NH 3 species, resulting from the hydride species on the surface. Among all tested catalysts, Ru 1 /CeO 2 shows the highest production of ammonia and highest CO conversion due to excellent water‐gas‐shift activity, whereas Pd 1 /CeO 2 shows lowest ammonia production. Rh 1 /CeO 2 shows the best low temperature NO reduction activity among all tested catalysts.

Tian, Jinshu↗
DOE OSTI2021

Bioinspired Activation of N 2 on Asymmetrical Coordinated Fe Grafted 1T MoS 2 at Room Temperature

Inspired by the nitrogen fixation process on MoFe nitrogenase, asymmetrical coordinated Fe grafted onto 1T MoS 2 were successfully synthesized. The unique electron -rich structure with asymmetrical coordination made the 1T Fe 0.1 Mo 0.9 S 2 layered material actively react with water and dinitrogen at room temperature and atmosphere pressure. Subsequently, ammonia can be produced with a yield of 800 pmol (NH 4 + ) g -1 (12.5% yield in mole). The activation, fixation and reduction of dinitrogen were confirmed by isotopically labeled experiments. The location and the specific coordination environment of grafted Fe in Fe-Mo-S were further determined by X-ray absorption spectroscopy analysis. Our work demonstrates that the nitrogen fixation and reduction for ammonia at room temperature without any chemical and electrochemical assistance is distinctly different from traditional bionic -inspired nitrogen fixation process. The mechanism of the activation and reduction of N 2 was further investigated by density functional theory calculation and Raman spectra. Compared with 1T MoS 2 , the enriched electron nature and asymmetrical coordination of Fe in Fe-Mo-S materials play a critical role in the bioinspired activation of N 2 at ambient condition.

1T MoS2↗
DOE OSTI2020

Electrocatalytic Valorization into H2 and Hydrocarbons of an Aqueous Stream Derived from Hydrothermal Liquefaction

Electrocatalytic oxidation is an attractive process for valorizing the carbon and removal of nitrogen present in the aqueous waste streams at ambient conditions. Here, we evaluated the electrocatalytic oxidation as a function of applied potential over a commercial Pt electrode of aqueous waste stream generated via hydrothermal liquefaction. We validated the conversion of quantifiable carbon (e.g., carboxylic acids, alpha hydroxyacids, alcohols, ketones, amides) and unquantifiable carbon as well as nitrogen removal. The unquantifiable carbon was valorized to quantifiable short chain organic molecules (e.g., acetic). Model studies showed that carboxylic acids, alcohol and ketones converted following (non-) Kolbe chemistry. Amides and alpha hydroxyacids formed carboxylic acids that subsequently converted via (non-) Kolbe chemistry. Ammonia was oxidized into N2. The reaction rate varied for each molecule family with carboxylic acids and ammonia having the highest reaction rates. The main reaction products from the electrocatalytic oxidation at the anode were volatile, short chain hydrocarbons (i.e., olefins, paraffins) and CO generated via Kolbe chemistry, while H2 was generated at the cathode. The parallel denitrification, valorization of carbon, and H2 generation of the aqueous waste can replace and simplify the current unit operations used in a commercial hydrothermal liquefaction process. The high operation potential required to drive the electrocatalytic reaction is responsible for high operation costs; however, they can be either partially subsidized with sale of excess H2 at the current DOE goal of $2/kg H2. Thus, the present work shows how electrocatalytic oxidation can be used to valorize aqueous waste streams into volatile hydrocarbons and H2.

Electrocatalytic oxidation, Aqueous waste valoriza↗
DOE OSTI2013

Current Understanding of Cu-Exchanged Chabazite Molecular Sieves for Use as Commercial Diesel Engine DeNOx Catalysts

Selective catalytic reduction (SCR) of NOx with ammonia using metal-exchanged molecular sieves with a chabazite (CHA) structure has recently been commercialized on diesel vehicles. One of the commercialized catalysts, i.e., Cu-SSZ-13, has received much attention for both practical and fundamental studies. For the latter, the particularly well-defined structure of this zeolite is allowing long-standing issues of the catalytically active site for SCR in metal-exchanged zeolites to be addressed. In this review, recent progress is summarized with a focus on two areas. First, the technical significance of Cu-SSZ-13 as compared to other Cu-ion exchanged zeolites (e.g., Cu-ZSM-5 and Cu-beta) is highlighted. Specifically, the much enhanced hydrothermal stability for Cu-SSZ-13 compared to other zeolite catalysts is addressed via performance measurements and catalyst characterization using several techniques. The enhanced stability of Cu-SSZ-13 is rationalized in terms of the unique small pore structure of this zeolite catalyst. Second, the fundamentals of the catalytically active center; i.e., the chemical nature and locations within the SSZ-13 framework are presented with an emphasis on understanding structure-function relationships. For the SCR reaction, traditional kinetic studies are complicated by intra-particle diffusion limitations. However, a major side reaction, nonselective ammonia oxidation by oxygen, does not suffer from mass-transfer limitations at relatively low temperatures due to significantly lower reaction rates. This allows structure-function relationships that are rather well understood in terms of Cu ion locations and redox properties. Finally, some aspects of the SCR reaction mechanism are addressed on the basis of in-situ spectroscopic studies.

chabazite zeolite catalyst↗
DOE OSTI2025

Evaluation of microalgae cultivation at air-CO 2 equilibrium pH for improving carbon utilization efficiency

Microalgae are often cultivated at near-neutral pH to optimize growth. However, this results in significant CO 2 loss through outgassing in open-pond cultivation systems, leading to low CO 2 utilization efficiency and higher biomass production costs. One potential solution is algal cultivation at air-CO 2 equilibrium pH, which minimizes CO 2 outgassing but may inhibit growth due to stresses at higher pH levels. In this study, we evaluated the viability of this approach by growing Picochlorum celeri and Tetraselmis striata under outdoor relevant conditions at equilibrium pH. Compared to pH 7 cultures, biomass productivity declined by 35 % for P. celeri and 57 % for T. striata. Although CO 2 outgassing could be minimized, the significant loss in productivity led to a higher overall minimum biomass selling price (MBSP). Increased ammonia toxicity at the higher pH was found to be one of the growth-limiting factors and was mitigated by reducing ammonium fertilizer concentration. This adjustment resulted in a more moderate productivity decline of 13 % (instead of 35 %) for T. striata, and consequently, a lower MBSP was achieved. These findings suggest that equilibrium pH cultivation may be a viable method for reducing CO 2 loss without significantly compromising biomass productivity. Depending on the strain, strategies to mitigate stressors, such as ammonia toxicity, may be necessary.

09 BIOMASS FUELS↗
DOE OSTI2016

Assessment of advanced solvent-based post-combustion CO 2 capture processes using a bi-objective optimization technique

We report the optimized performance of two advanced CO 2 capture processes is compared to that of a monoethanolamine (MEA) baseline for a gas-powered CO 2 capture retrofit of an existing coal-fired facility. The advanced temperature-swing processes utilize piperazine and mixed-salt solvents. The mixed-salt treatment involves the use of ammonia for CO 2 absorption and potassium carbonate primarily to control ammonia slip. The processes are represented in terms of energy duty requirements within a modular heat integration code developed for CO 2 capture modeling and optimization. The model includes a baseload coal plant, a gas-fired subsystem containing gas turbines and a heat recovery steam generator (HRSG), and a CO 2 capture facility. A formal bi-objective optimization procedure is applied to determine the design (e.g., detailed HRSG components and pressure levels, gas turbine capacity, CO 2 capture capacity) and time-varying operations of the facility to simultaneously maximize net present value (NPV) and minimize total capital requirement (TCR), while meeting a maximum CO 2 emission intensity constraint. For a realistic scenario constructed using historical data, optimization results indicate that both advanced processes outperform MEA in both objectives, and the mixed-salt process in turn outperforms the piperazine process. Specifically, for the scenario considered, the base case mixed-salt process achieves 16% greater NPV and 14% lower TCR than the MEA process, and 10% greater NPV and 5% lower TCR than the piperazine process. A five-case sensitivity study of the mixed-salt process indicates that it is competitive with the piperazine process and consistently outperforms the MEA process.

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

Manganese concentration influences nitrogen cycling in agricultural soil

Manganese (Mn) can modulate nitrogen (N) transformations in soil, yet its role in agroecosystems remains understudied. We conducted a 51-day microcosm incubation with agricultural soils differing in long-term N history (N 0 , no added N; N 1 , added 225 kg N ha −1 for a duration of 27 years) and amended with soluble Mn at 0 (M 0 ), 50 (M 1 ), or 250 (M 2 ) mg kg −1 and Glyceria striata (Lam.) residue. In N 1 soils, Mn additions (both M 1 and M 2 ) lowered total mineral N by 25 % relative to N 1 M 0 at day 51 and reduced 51-day cumulative N₂O by 32 % (N 1 M 1 ) and 42 % (N 1 M 2 ) vs. N 1 M 0 , whereas effects in N 0 were negligible. Mn also depressed ammonia-oxidizing bacterial amoA gene transcripts at day 15 in N 1 M 2 vs. N 1 M 0 (2.5 fold change). This reduction was likely due to increased N loss via complete denitrification to N₂ through microbial pathways such as nitrate/nitrite-dependent manganese oxidation (NDMO), where bacteria directly used the added Mn 2+ to reduce nitrate (NO 3 − ) and nitrite (NO 2 − ) to N 2 or as Mn dependent-ammonia oxidation (Mnammox) where bacteria oxidized ammonium (NH 4 + ) to N 2 , using Mn oxides as electron acceptors that formed from the oxidation of the added Mn. Other contributing mechanisms may include Mn-induced N immobilization, toxicity, and changes in the microbial community. These mechanistic results indicate that background Mn availability and redox dynamics can shape nitrification–denitrification pathways under N-rich conditions. In conclusion, we highlight how native Mn pools and redox state may help explain observed variability in N losses and greenhouse gas production across agricultural soils.

Decomposition↗