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Results for “Ammonia decomposition”

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NASA NTRS1976

Study of removal of ammonia from urine vapor by dual catalyst

The feasibility of ammonia removal from urine vapor by a low temperature dual-catalyst system was investigated. The process is based on the initial catalytic oxidation of ammonia present in urine vapor to nitrogen and nitrous oxide, followed by a catalytic decomposition of the nitrous oxide formed into its elements. The most active catalysts for the oxidation of ammonia and for the decomposition of N2O, identified in screening tests, were then combined into dual catalyst systems and tested to establish their overall efficiencies for the removal of ammonia from artificial gas mixtures. Dual catalyst systems capable of ammonia removal from the artificial gas mixtures were then tested with the actual urine vapor produced by boiling untreated urine. A suitable dual catalyst bed arrangement was found that achieved the removal of ammonia and organic carbon, and recovered water of good quality from urine vapor.

Budininkas, P.↗

NASA NTRS1979

Data reduction and performance determination

Definitions, algorithms, and procedures for the reduction of monopropellant thruster measurements to performance parameters are provided. A brief discussion of acquisition and recording systems is also included. Emphasis is placed upon monopropellant hydrazine engines, and some parameters relate specifically to the catalytic decomposition of hydrazine (e.g., percent ammonia dissociation). Performance of other types of monopropellant thrusters may, however, be determined by using procedures similar to those discussed. Two appendixes are included: (1) theoretical performance of monopropellant hydrazine; and (2) calculation of rotational performance.

Source record↗

DOE OSTI2021

Hyperstoichiometric Uranium Dioxides: Rapid Synthesis and Irradiation-Induced Structural Changes

Uranium dioxide (UO 2 ), the primary fuel for commercial nuclear reactors, incorporates excess oxygen forming a series of hyperstoichiometric oxides. Thin layers of these oxides, such as UO 2.12 , form readily on the fuel surface and influence its properties, performance, and potentially geologic disposal. This work reports a rapid and straightforward combustion process in uranyl nitrate–glycine–water solutions to prepare UO 2.12 nanomaterials and thin films. We also report on the investigation of the structural changes induced in the material by irradiation. Despite the simple processing aspects, the combustion synthesis of UO 2.12 has a sophisticated chemical mechanism involving several exothermic steps. Raman spectroscopy and single-crystal X-ray diffraction (XRD) measurements reveal the formation of a complex compound containing the uranyl moiety, glycine, H 2 O, and NO 3 – groups in reactive solutions and dried combustion precursors. Combustion diagnostic methods, gas-phase mass spectroscopy, differential scanning calorimetry (DSC), and extracted activation energies from DSC measurements show that the rate-limiting step of the process is the reaction of ammonia with nitrogen oxides formed from the decomposition of glycine and uranyl nitrate, respectively. However, the exothermic decomposition of the complex compound determines the maximum temperature of the process. In situ transmission electron microscopy (TEM) imaging and electron diffraction measurements show that the decomposition of the complex compound directly produces UO 2 . The incorporation of oxygen at the cooling stage of the combustion process is responsible for the formation of UO 2.12 . Spin coating of the solutions and brief annealing at 670 K allow the deposition of uniform films of UO 2.12 with thicknesses up to 300 nm on an aluminum substrate. Irradiation of films with Ar 2+ ions (1.7 MeV energy, a fluence of up to 1 × 10 17 ions/cm 2 ) shows unusual defect-simulated grain growth and enhanced chemical mixing of UO 2.12 with the substrate due to the high uranium ion diffusion in films. As a result, the method described in this work allows the preparation of actinide oxide targets for fundamental nuclear science research and studies associated with stockpile stewardship.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2023

GaN MOCVD Growth on Native substrates for High Voltage (15-20 KV) Vertical Power Devices

This project aims to develop metalorganic chemical vapor deposition (MOCVD) homoepitaxy of GaN on native substrates with fast growth rate (15-20 μm/hr), low background doping (low-10 15 cm -3 ) and smooth surface morphology via comprehensive understanding of the crystal growth process including high quality GaN substrate development and surface preparation, impurity and native defects control, and their impacts on the breakdown field. The team successfully developed a new growth process by introducing the laser-assisted MOCVD (LA-MOCVD) process to address the limited growth rates of GaN in the traditional MOCVD process. Specifically, the use of the CO2 laser with lasing wavelength of 9.219 μm, the strong coupling between the laser beam with the ammonia (GaN MOCVD precursor) leads to efficient decomposition of NH3 which significantly increases the effective group V/III molar ratio and thus suppresses C impurity incorporation in MOCVD GaN. The reduction in C incorporation in LA-MOCVD GaN is especially prominent when the GaN growth rate is fast (> 10 μm/hr), which allows to develop thick GaN films with high crystalline quality and low controllable doping needed for vertical high power device applications. The results of this project lead to the demonstration of vertical GaN PN diodes with record breakdown voltage of ~ 8kV with high Baliga’s figure of merit.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2023

A laboratory-scale process for producing dilithium beryllium tetrafluoride (FLiBe) with dissolved uranium tetrafluoride

Flibe Energy, Incorporated (FEI)'s conceptual Lithium Fluoride Thorium Reactor (LFTR) incorporates a chemical processing facility aimed at recovering uranium and other valuable volatile radionuclides while managing harmful radionuclides from the used fuel. The fuel utilized in this reactor is a combination of dilithium beryllium tetrafluoride (Li 2 BeF 4 or FLiBe) and uranium tetrafluoride (UF 4 ), (FLiBe/U). FEI's plan involves extracting the uranium and other valuable volatile fluoride-forming radionuclides using nitrogen trifluoride (NF 3 ). To facilitate laboratory-scale testing of uranium extraction using NF 3 and address the toxicity and physical hazards associated with beryllium and beryllium fluoride (BeF 2 ), we used a two-step process to prepare the simulated fuel salt. The first step entailed thermally decomposing ammonium beryllium tetrafluoride [(NH 4 ) 2 BeF 4 ] (ABeF) through a nominal 3-step process, combined with appropriate amounts of lithium fluoride (LiF) and UF 4 , resulting in the formation of beryllium fluoride (BeF 2 ). In the second step, the mixture was repeatedly melted and frozen at the melting point of FLiBe to prepare the eutectic FLiBe with dissolved UF 4 . Although the concept appears straightforward, the production of FLiBe/U involved various challenges. These challenges included transporting the gaseous decomposition products of ABeF, hydrogen fluoride (HF) and ammonia (NH 3 ), while preventing the formation of ammonium fluoride (NH 4 F). Additionally, it was necessary to control the reaction between the higher-than-anticipated water content in the commercial ABeF with NH 3 , HF, and the condensed NH 4 F, protect UF 4 from forming an unknown black compound, select suitable structural materials to mitigate fluoride corrosion, address the risks associated with beryllium toxicity through equipment design and operational protocols, and monitor process conditions. This article provides an account of the thermal decomposition chemistry observed in the commercial ABeF, describes the FLiBe/U production apparatus, describes the experiences and process refinements developed to prepare FLiBe/U, and presents our characterizations of prepared FLiBe/U.

Ammonium beryllium fluoride thermal decomposition↗

DOE OSTI2021

Hydrogen carriers: Production, transmission, decomposition, and storage

Recognizing the potential role of liquid hydrogen carriers in overcoming the inherent limitations in transporting and storing gaseous and liquid hydrogen, a complete production and use scenario is postulated and analyzed for perspective one-way and two-way carriers. The carriers, methanol, ammonia and toluene/MCH (methylcyclohexane), are produced at commercially viable scales in a central location, transmitted by rail or pipelines for 2000 miles, and decomposed near city gates to generate fuel-cell quality hydrogen for distribution to refueling stations. In terms of the levelized cost of H 2 distributed to the stations, methanol is less expensive to produce (1.22 dollars per kg-H 2 ) than MCH (1.35 dollars per kg-H 2 ) or ammonia (2.20 dollars per kg-H 2 ). Levelized train transmission cost is smaller for methanol (0.63 dollars per kg-H 2 ) than ammonia (1.29 dollars per kg-H 2 ) or toluene/MCH system (2.07 dollars per kg-H 2 ). Levelized decomposition cost is smaller for ammonia (0.30-1.06 dollars per kg-H 2 ) than MCH (0.54-1.22 dollars per kg-H 2 ) or methanol (0.43-1.12 dollars per kg-H 2 ). Over the complete range of demand investigated, 10-350 tpd-H 2 , the levelized cost of H2 distributed to stations is aligned as methanol « ammonia ~ MCH. With pipelines at much larger scale, 6000 tpd-H 2 , the levelized cost decreases by ~1 dollar per kg-H 2 for ammonia and MCH and much less for methanol. Methanol is a particularly attractive low-risk carrier in the transition phase with lower than 50-tpd H 2 demand.

08 HYDROGEN↗

DOE OSTI2025

Evaluating the industrial potential of emerging biomass pretreatment technologies in bioethanol production and lipid recovery from transgenic sugarcane

The selection of pretreatment methods is critical to achieving high product yields during bioconversion of lignocellulosic biomass. Hydrothermal, soaking-in-aqueous ammonia, and ionic liquid pretreatment methods are viable candidates for minimizing sugar decomposition, permitting the effective hydrolysis of structural carbohydrates, and producing a fermentable substrate suitable for achieving industrial ethanol titers and yields. In this study, the effect of these three pretreatment methods on non-modified sugarcane cultivar CP88-1762 and two transgenic lipid-accumulating sugarcane lines, oilcane 1565 and oilcane 1566, were investigated and compared in terms of lipid recovery, sugar yield, and ethanol yields within the lignocellulosic biomass conversion pipeline. Fed-batch enzymatic hydrolysis at high solid loading yielded hydrolysates capable of supporting industrial bioethanol titers across all conditions. The highest sugar yields were obtained on ammonia-pretreated biomass hydrolysate (253.73 g L −1 ), followed by hydrothermally pretreated hydrolysate (213.10 g L −1 ) and ionic liquid-pretreated hydrolysate (154.20 g L −1 ). Commercially viable ethanol titers of 100.62 g L −1 , 64.47 g L −1 , and 52.95 g L −1 were achieved from ammonia, hydrothermal, and ionic liquid pretreated hydrolysate with the corresponding ethanol productivities of 2.08 g L −1 h −1 , 0.53 g L −1 h −1 , and 0.36 g L −1 h −1 . The lower acetic acid concentration in ammonia-pretreated hydrolysate may have enhanced its fermentability relative to the hydrothermal pretreatment condition, as indicated by the differences in ethanol titer and productivity. Lower sugar yields and ethanol productivities under the ionic liquid conditions likely resulted from the inhibitory effect of cholinium lysinate. Oilcane 1565 and oilcane 1566 bagasse accumulated over 16- and 3 times higher lipids than the non-modified sugarcane CP88-1762. The total fatty acid content in the oilcane samples was reduced in ammonia and ionic liquid-pretreated bagasse relative to the hydrothermal pretreatment condition. While all pretreatment techniques tested are industrially viable, the observed differences in titer, productivity, and lipid content indicate that careful selection and validation of upstream processing methods can contribute to improved economic and environmental outcomes.

09 BIOMASS FUELS↗

DOE OSTI2025

Data for "Evaluating the industrial potential of emerging biomass pretreatment technologies in bioethanol production and lipid recovery from transgenic sugarcane"

The selection of pretreatment methods is critical to achieving high product yields during bioconversion of lignocellulosic biomass. Hydrothermal, soaking-in-aqueous ammonia, and ionic liquid pretreatment methods are viable candidates for minimizing sugar decomposition, permitting the effective hydrolysis of structural carbohydrates, and producing a fermentable substrate suitable for achieving industrial ethanol titers and yields. In this study, the effect of these three pretreatment methods on non-modified sugarcane cultivar CP88-1762 and two transgenic lipid-accumulating sugarcane lines, oilcane 1565 and oilcane 1566, were investigated and compared in terms of lipid recovery, sugar yield, and ethanol yields within the lignocellulosic biomass conversion pipeline. Fed-batch enzymatic hydrolysis at high solid loading yielded hydrolysates capable of supporting industrial bioethanol titers across all conditions. The highest sugar yields were obtained on ammonia-pretreated biomass hydrolysate (253.73 g L−1), followed by hydrothermally pretreated hydrolysate (213.10 g L−1) and ionic liquid-pretreated hydrolysate (154.20 g L−1). Commercially viable ethanol titers of 100.62 g L−1, 64.47 g L−1, and 52.95 g L−1 were achieved from ammonia, hydrothermal, and ionic liquid pretreated hydrolysate with the corresponding ethanol productivities of 2.08 g L−1 h−1, 0.53 g L−1 h−1, and 0.36 g L−1 h−1. The lower acetic acid concentration in ammonia-pretreated hydrolysate may have enhanced its fermentability relative to the hydrothermal pretreatment condition, as indicated by the differences in ethanol titer and productivity. Lower sugar yields and ethanol productivities under the ionic liquid conditions likely resulted from the inhibitory effect of cholinium lysinate. Oilcane 1565 and oilcane 1566 bagasse accumulated over 16- and 3 times higher lipids than the non-modified sugarcane CP88-1762. The total fatty acid content in the oilcane samples was reduced in ammonia and ionic liquid-pretreated bagasse relative to the hydrothermal pretreatment condition. While all pretreatment techniques tested are industrially viable, the observed differences in titer, productivity, and lipid content indicate that careful selection and validation of upstream processing methods can contribute to improved economic and environmental outcomes.

biomass analytics↗

NASA NTRS1987

In-situ analysis of hydrazine decomposition products

A gas analyzer utilizing a nondispersive infrared (NDIR) detection system was used to monitor the ammonia and water vapor content of the products of a previously unused hydrazine gas generator. This provided an in-situ measurement of the generator's efficiency difficult to obtain by other means. The analyzer was easily installed in both the calibration and hydrazine systems, required no maintenance other than periodic zero adjustments, and performed well for extended periods in the operating range tested. The catalyst bed operated smoothly and repeatably during the 28 hr of testing. No major transients were observed on startup or during steady state operation. The amount of ammonia in the output stream of the gas generator was found to be a strong function of temperature at catalyst bed temperatures below 450 C. At temperatures above this, the efficiency remained nearly constant. On startup the gas generator efficiency was found to decrease with time until a steady state value was attained. Elevated catalyst bed temperatures in the periods before steady state operation was found to be responsible for this phenomenon.

Curran, Francis M.↗

NASA NTRS1987

In-situ analysis of hydrazine decomposition products

Curran, Francis M.↗

DOE OSTI2021

Role of Hydrogen-bonded Bimolecular Formic Acid–Formate Complexes for Formic Acid Decomposition on Copper: A Combined First-Principles and Microkinetic Modeling Study

Hydrogen bonding interactions alter the nanoscale reaction mechanisms of many chemistries. Yet, it remains unclear how they affect heterogeneously catalyzed decomposition of formic acid (FA), a reaction of intense interest since FA is a promising hydrogen carrier. In this work, we elucidate how hydrogen bonding affects the reaction mechanisms for FA decomposition on Cu(111) by combining first-principles density functional theory calculations to calculate reaction energetics, Latin-hypercube sampling to elucidate stable high-coverage adsorbate configurations, and coverage self-consistent mean-field microkinetic models to predict reaction kinetics. We demonstrate that hydrogen-bonded complexes of FA with formate (bimolecular FA–HCOO complexes) can play a dominant role in FA decomposition. Specifically, our first-principles calculations show that hydrogen bonding of FA with HCOO may stabilize the crucial monodentate HCOO intermediate and the transition states for HCOO decomposition, especially at low coverages. We predict that, depending on the reaction conditions, 40–80% of the reaction flux goes through pathways involving the bimolecular FA–HCOO complexes. Additionally, the active site for FA decomposition on Cu(111) involves a high coverage (~0.4 monolayers (ML)) of these complexes, which unexpectedly stabilize intermediates and transition states via van der Waals interactions. Our work provides molecular insights consistent with previous experimental observations on supported Cu/Al 2 O 3 catalysts. This paves the way toward the development of novel catalysts for FA decomposition as well as for other industrially important chemistries with intermediates capable of hydrogen bonding, such as ammonia electrooxidation and CO 2 hydrogenation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1959

Propellant Vaporization as a Criterion for Rocket-Engine Design; Experimental Performance, Vaporization and Heat-Transfer Rates with Various Propellant Combinations

Experimental combustion efficiencies of eleven propellant combinations were determined as a function of chamber length. Efficiencies were measured in terms of characteristic exhaust velocities at three chamber lengths and in terms of gas velocities. The data were obtained in a nominal 200-pound-thrust rocket engine. Injector and engine configurations were kept essentially the same to allow comparison of the performance. The data, except for those on hydrazine and ammonia-fluorine, agreed with predicted results based on the assumption that vaporization of the propellants determines the rate of combustion. Decomposition in the liquid phase may be.responsible for the anomalous behavior of hydrazine. Over-all heat-transfer rates were also measured for each combination. These rates were close to the values predicted by standard heat-transfer calculations except for the combinations using ammonia.

Clark, Bruce J.↗

DOE OSTI2025

Temperature-dependent solid electrolyte interphase reactions drive performance in lithium-mediated nitrogen reduction to ammonia

The solid electrolyte interphase (SEI) is a vital component to control mass transport and selectivity in the lithium-mediated reduction of N 2 to NH 3 (Li-N 2 R). Finding strategies that generate the optimal SEI, a complex network of organic and inorganic species, can potentially improve Li-N 2 R performance. Here, we unravel structure-property relationships of the SEI by correlating its composition with the NH 3 faradaic efficiency (FENH3). By modifying the reaction temperature, we alter electrolyte decomposition reactions and observe changes in the SEI that explain FE NH3 trends between electrolyte solvents. We quantify a complex reaction environment at elevated temperatures where SEI formation is counteracted by etching reactions. This tradeoff leads to temporal fluctuations of FE NH3 , but the maximal FE NH3 can reach up to 40%, the highest value reported for batch cells at ambient pressure, thus far. In conclusion, our work underscores the potential of novel electrolytes that steer SEI selectivity and, ultimately, improve Li-N 2 R performance.

electrocatalytic nitrogen reduction↗

DOE OSTI2020

A non-perturbative pairwise-additive analysis of charge transfer contributions to intermolecular interaction energies

Energy decomposition analysis (EDA) based on absolutely localized molecular orbitals (ALMOs) decomposes the interaction energy between molecules into physically interpretable components like geometry distortion, frozen interactions, polarization, and charge transfer (CT, also sometimes called charge delocalization) interactions. In this work, a numerically exact scheme to decompose the CT interaction energy into pairwise additive terms is introduced for the ALMO-EDA using density functional theory. Unlike perturbative pairwise charge-decomposition analysis, the new approach does not break down for strongly interacting systems, or show significant exchange–correlation functional dependence in the decomposed energy components. Both the energy lowering and the charge flow associated with CT can be decomposed. Complementary occupied–virtual orbital pairs (COVPs) that capture the dominant donor and acceptor CT orbitals are obtained for the new decomposition. It is applied to systems with different types of interactions including DNA base-pairs, borane-ammonia adducts, and transition metal hexacarbonyls. While consistent with most existing understanding of the nature of CT in these systems, we report the results also reveal some new insights into the origin of trends in donor–acceptor interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1989

Modern biofuel cells for waste recycling in life support systems

Innovative ways of treating urea in waste water reprocessing for long duration space exploration are being considered. Urea is very stable and therefore there are few effective ways for its decomposition. The feasibility of the use of the enzyme urease is to catalyze the hydrolysis of urea to ammonia and carbon dioxide is discussed, including a methodology, potential problems, the capabilities and advantages of such a system.

Chen, L.↗

DOE OSTI2020

Formic Acid: A Hydrogen-Bonding Cocatalyst for Formate Decomposition

Hydrogen bonding accelerates many catalytic reactions by orienting intermediates, stabilizing transition states, and even opening reaction pathways. However, most mechanistic studies regarding the decomposition of formic acid (FA), a promising hydrogen storage material, neglect hydrogen-bonding interactions even though FA is a strong hydrogen-bond donor and acceptor. Here, we probe the formation of bimolecular hydrogen-bonded complexes between FA and formate (FA–HCOO complexes) adsorbed on metal surfaces and how these complexes affect HCOO* decomposition. Using first-principles density functional theory (DFT) calculations on 12 close-packed (111)/(0001) and 8 open (100) surfaces of 12 transition metals—Ag, Au, Co, Cu, Ir, Ni, Os, Re, Pd, Pt, Rh, and Ru, we—show that FA–HCOO complexes are generally thermodynamically stable, even at elevated temperatures and pressures. We then illustrate that these complexes produce infrared spectroscopic signatures consistent with as yet unassigned experimental peaks. We last demonstrate that by stabilizing the dangling bond of monodentate HCOO*, these complexes significantly lower the barriers for rotation of HCOO* from a bidentate to a monodentate configuration, the rate-limiting step for HCOO* decomposition on many surfaces. FA thus acts as a cocatalyst for HCOO* decomposition. Our results may guide the community toward improved catalysts for reactions involving HCOO* such as FA decomposition, methanol steam reforming, and the water gas shift reaction. More broadly, our work highlights the ability of hydrogen bonding to modify the adsorbed structures of intermediates and lower the barriers for their reaction on heterogeneous catalysts. Lastly, this phenomenon can be relevant for other reactions involving ammonia, alcohols, and carboxylic acids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1994

Synthesis Of A Precursor Of Silicon Nitride

Promising route toward production of highly pure, finely divided, easily sinterable silicon nitride (Si3N4) involves thermal decomposition of silicon diimide {Si(NH)2} prepared by ammonolysis of Si(SCN)4 in CH3CN and purified by complete extraction of byproduct NH4SCN by use of ammonia at temperature and pressure above critical point.

Philipp, Warren H.↗

NASA NTRS1979

The role of phosphorus in the upper atmosphere of Jupiter

The reaction of elemental phosphorus and H atoms to form PH3 was observed and should be a major factor in the recycling of PH3 in the stratosphere of Jupiter. The formation of PH3 in this manner should predominate at high altitudes where, due to the very low temperatures, reactions that require higher activation energies than these atom reactions cannot occur. At lower altitudes, in the troposphere, the rapid formation of H atoms from the strong absorption of light by NH3 will contribute to phosphine production also in this same manner. Recent experiments have also shown that elemental phosphorus reacts readily with aqueous ammonia to form PH3. This reaction may also be important in the recycling of PH3 in the upper troposphere of Jupiter if water-ammonia clouds, as had been previously thought, exist. Considerations of the coloration of the Great Red Spot have been made based upon the nature of the phosphorus obtained by decomposition of the phosphine.

Howland, G. R.↗