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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Radiation chemistry in solvent extraction: FY2010 Research

This report summarizes work accomplished under the Fuel Cycle Research and Development (FCR&D) program in the area of radiation chemistry during FY 2010. The tasks assigned during FY 2010 included: • Development of techniques to measure free radical reaction kinetics in the organic phase. • Initiation of an alpha-radiolysis program • Initiation of an effort to understand dose rate effects in radiation chemistry • Continued work to characterize TALSPEAK radiation chemistry Progress made on each of these tasks is reported here. Briefly, a method was developed and used to measure the kinetics of the reactions of the •NO3 radical with solvent extraction ligands in organic solution, and the method to measure •OH radical reactions under the same conditions has been designed. Rate constants for the CMPO and DMDOHEMA reaction with •NO3 radical in organic solution are reported. Alpha-radiolysis was initiated on samples of DMDOHEMA in alkane solution using He ion beam irradiation and 211At isotope irradiation. The samples are currently being analyzed for comparison to DMDOHEMA ?-irradiations using a custom-developed mass spectrometric method. Results are also reported for the radiolytic generation of nitrous acid, in ?-irradiated nitric acid. It is shown that the yield of nitrous acid is unaffected by an order-of-magnitude change in dose rate. Finally, recent results for TALSPEAK radiolysis are reported, summarizing the effects on solvent extraction efficiency due to HDEHP irradiation, and the stable products of lactic acid and DTPA irradiation. In addition, results representing increased scope are presented for the radiation chemistry program. These include an investigation of the effect of metal complexation on radical reaction kinetics using DTPA as an example, and the production of a manuscript reporting the mechanism of Cs-7SB radiolysis. The Cs-7SB work takes advantage of recent results from a current LDRD program to understand the fundamental chemistry of nitration under radiolysis conditions. Finally, work toward understanding the chemistry of irradiated formic acid is presented. This is important because all organic compounds eventually produce formic acid under long-term irradiation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Reversible Hydrogen Storage using CO2 and a Proton-Switchable Iridium Catalyst in Aqueous Media under Mild Temperatures and Pressures

Green plants convert CO{sub 2} to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO{sub 2} and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO{sub 2}, formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong {pi}-donor, and is rationalized by theoretical and experimental studies.

08 HYDROGEN↗
DOE OSTI2025

Effect of Ambient Organic Acids on the Water Structure at ${\rm TiO}_{2}$ Interfaces

A molecular-level understanding of the effects of ambient organic compounds on the wettability of titanium dioxide ( ${\rm TiO}_{2}$ ) surfaces is relevant to many of its energy-related and environmental applications. Herein, we focus on two common atmospheric carboxylic acids, formic and acetic acid, and characterize their adsorption/ desorption at the aqueous interfaces of anatase and rutile ${\rm TiO}_{2}$ using molecular dynamics with an ab initio deep neural network potential. Our simulations show that these acids prefer to be localized in the interfacial water layers close to the ${\rm TiO}_{2}$ surface where they are stabilized by the interaction/exchange of their acid proton with a surface oxygen, rather than chemisorb at the surface Ti sites by displacing the adsorbed water. Notably, these acids make the surface of anatase hydrophobic, whereas the larger fraction of adsorbed water dissociation can offset their effect on rutile. Furthermore, these results provide a picture where carboxylic acids control the wettability of ${\rm TiO}_{2}$ largely through acid-base chemistry at the interface rather than chemisorption on the oxide surface, a finding that can help improve the design of self-cleaning surfaces and photocatalytic devices.

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

Cross-aldol condensation on missing linker sites of metal–organic framework UiO-66

Missing linkers induce coordinatively unsaturated Lewis acid-base pair sites in metal–organic frameworks such as UiO-66 (Zr). The Lewis acid-base pair is induced by replacing the benzene dicarboxylic acid linker with formic acid, which subsequently is thermally decomposed. The concentration of coordinatively unsaturated Zr 4+ cations was titrated with acetone. In parallel to their concentration, the catalytic activity increased while the selectivity for aldol condensation between furfural and acetone remained constant. The missing linkers generate a complex ensemble consisting of an (at least partly) accessible Zr 4+ cation surrounded by oxygen, catalyzing the cross-aldol condensation. As a result, density functional theory calculations, matching the experimental findings provide a more detailed understanding of the elementary steps during the condensation reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Mechanism of Methanol Synthesis on Cu through CO 2 and CO Hydrogenation

We present a comprehensive mean-field microkinetic model for the methanol synthesis and water-gas-shift (WGS) reactions that includes novel reaction intermediates, such as formic acid (HCOOH) and hydroxymethoxy (CH₃O₂) and allows for the formation of formic acid (HCOOH), formaldehyde (CH₂O), and methyl formate (HCOOCH₃) as byproducts. All input model parameters were initially derived from periodic, self-consistent, GGA-PW91 density functional theory calculations on the Cu(111) surface and subsequently fitted to published experimentalmethanol synthesis rate data, which were collected under realistic conditions on a commercial Cu/ZnO/Al₂O₃ catalyst. We find that the WGS reaction follows the carboxyl (COOH)-mediated path and that both CO and CO₂ hydrogenation pathways are active for methanol synthesis. Under typical industrial methanol synthesis conditions, CO₂ hydrogenation is responsible for ~2/3 of the methanol produced. The intermediates of the CO₂ pathway for methanol synthesis include HCOO*, HCOOH*, CH₃O₂*, CH₂O*, and CH₃O*. The formation of formate (HCOO*) from CO₂* and H* on Cu(111) does not involve an intermediate carbonate (CO₃*) species, and hydrogenation of HCOO* leads to HCOOH* instead of dioxymethylene (H₂CO₂*). The effect of CO is not only promotional; CO* is also hydrogenated in significant amounts to HCO*, CH₂O *, CH₃O*, and CH₃OH*. We considered two possibilities for CO promotion: (a) removal of OH* via COOH* to form CO₂ and hydrogen (WGS), and (b) CO-assisted hydrogenation of various surface intermediates, with HCO* being the H-donor. Only the former mechanism contributes to methanol formation, but its effect is small compared with that of direct CO hydrogenation to methanol. Overall, methanol synthesis rates are limited by methoxy (CH₃O*) formation at low CO₂/(CO+CO₂) ratios and by CH₃O* hydrogenation in CO₂-rich feeds. CH₃O* hydrogenation is the common slow step for both the CO and the CO₂ methanol synthesis routes; the relative contribution of each route is determined by their respective slow steps HCO*+H*→CH₂O*+* and HCOOH*+H*→CH₃O₂*+* as well as by feed composition and reaction conditions. An analysis of the fitted parameters for a commercial Cu/ZnO/Al₂O₃ catalyst suggests that a more open Cu surface, for example, Cu(110), Cu(100), and Cu(211) partially covered by oxygen, may provide a better model for the active site of methanol synthesis, but our studies cannot exclude a synergistic effect with the ZnO support.

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

Solvent selection for biphasic extraction of 5-hydroxymethylfurfural via multiscale modeling and experiments

We introduce a comprehensive conceptual framework for selecting solvents for reactive extraction in biphasic organic-water systems and demonstrate it for the separation of HMF (5-hydroxylmethylfurfural), a platform chemical produced in the acid-catalyzed dehydration of hexoses. We first perform in silico screening of ~2500 solvents, from the ADFCRS-2018 database using the ADF COSMO-RS implementation, and classification, based on the solvent partition coefficient. We then determine experimentally the partition coefficients for HMF, fructose, and products of HMF rehydration (levulinic acid (LA), and formic acid (FA)), the mutual water-organic solvent solubilities, and the separation factors in >50 select solvents spanning multiple homologous series at room temperature and a typical reaction temperature with in situ sampling. We find that COSMO-RS is excellent for screening purposes (typical error in most cases within a factor of ~2). Increased temperatures lead to significant reduction in partitioning, and room temperature measurements are clearly inadequate for solvent selection. Upon down selecting classes of solvents based on separation performance, we perform experimental thermal stability and reaction compatibility studies of a small set of solvents at relevant reactive-extraction temperatures. We discover that many substituted phenols exhibit an order-of-magnitude increase in partitioning compared to conventional solvents due chiefly to hydrogen bond interactions and show the necessary stability but retain a significant fraction of water and LA, factors that need to be considered in technoeconomic analysis. In contrast, anilines, aldehydes, and acids are good to excellent regarding separation but incompatible with this specific reaction medium. Furthermore, this multifaceted framework can be extended to other biomass-derived products and processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

DWPF SMECT PVV Sample Characterization and Remediation

On April 2, 2013, a solid sample of material collected from the Defense Waste Processing Facility’s Process Vessel Vent (PVV) jumper for the Slurry Mix Evaporator Condensate Tank (SMECT) was received at the Savannah River National Laboratory (SRNL). DWPF has experienced pressure spikes within the SMECT and other process vessels which have resulted in processing delays while a vacuum was re-established. Work on this sample was requested in a Technical Assistance Request (TAR). This document reports the results of chemical and physical property measurements made on the sample, as well as insights into the possible impact to the material using DWPF’s proposed remediation methods. DWPF was interested in what the facility could expect when the material was exposed to either 8M nitric acid or 90% formic acid, the two materials they have the ability to flush through the PVV line in addition to process water once the line is capped off during a facility outage.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Impact of Permanganate Oxidation of Glycolate on Corrosion of the Defense Waste Processing Facility (DWPF) Recycle Collection Tank (RCT), Transfer-line and Waste Tank Materials of Construction (MoC)

Savannah River Remediation (SRR) is evaluating the use of glycolic acid to replace formic acid as an alternate reductant for the Defense Waste Processing Facility (DWPF) at Savannah River Site (SRS). The replacement is aimed at reducing facility hazards, improving pH stability and rheological control, and lowering off gas production. Glycolate, which is the product that may remain, can also be carried downstream to High-Level Waste and Low-Level Waste facilities. Complete oxidation of glycolate and other organic species from the Sludge Receipt and Adjustment Tank (SRAT) may be necessary to minimize thermolytic hydrogen generation that can cause flammability issues. The glycolate oxidation may be performed in the Recycle Collection Tank (RCT). The RCT heel would be adjusted with sodium hydroxide to maintain the solution caustic and sodium nitrite as corrosion inhibitor prior to the addition of condensate that can be from the contents of the Slurry Mix Evaporator Condensate Tank (SMECT) or Offgas Condensate Tank (OGCT). The RCT tank collects the waste to be transferred via the Low Point Pump Pit – Recycle Pump Tank (LPPP-RPT) through a jacketed transfer-line to the Tank Farm facility. Scoping studies were performed to evaluate an oxidizing agent and sodium permanganate was selected as the best option for glycolate destruction. Testing was recommended to determine the impact on the Materials of Construction (MoC) due to the addition of sodium permanganate. The targeted concentration of sodium permanganate used equated to a 7:1 molar permanganate to glycolate ratio (nominally 0.002 M permanganate). However, to conservatively maximize the permanganate corrosivity, in some cases no glycolate was added.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1997

Computer-aided design of a proton pump

The use of transmembrane proton gradients in energy transduction is an almost universal feature of life on earth. These proton gradients are established and maintained by specialized assemblies of proteins which actively pump protons across membranes. One broad class of proton pumps uses captured light energy to drive the proton pumping. Our goal is to elucidate the minimum structural requirements of a light-driven proton-pump. There are two basic components to a simple light-driven proton pump: a source of photo-generated protons and a "gate-keeper" which prevents these protons from reattaching themselves to their source. A wide variety of molecules in the membrane, even as simple as polycyclic aromatic hydrocarbons, are capable of releasing protons when illuminated. Our work is therefore focused on the design of the "gate-keeper." Our initial model involves a pair of proton acceptors, coupled to each other by a transient water bridge, and supported in the membrane by a small bundle of peptide helices. Upon illumination, the proton source transfers its proton to the:- first acceptor of the gate-keeper. While the reverse reaction is highly probable, all that is needed to ensure irreversibility is a nonvanishing probability that the proton will be transferred to the second acceptor across a transient water bridge. Back transfer of the proton to the first acceptor, and thence to the proton source, is impeded by the free energy required to move the proton uphill towards the. proton source and by the disruption of the transient water bridge. As a prototypical water-bridged proton transfer system, we are studying the transfer of a proton across a water bridge from a formic acid to a formate anion. With a pK(sub alpha), of 3.7. formic acid is a good model for the acidic amino acids glutamate and aspartate which are good candidates for gate-keeper proton acceptors. Simulations of proton transfer reactions in a membrane are complicated by the quantum mechanical nature of the process breaking and forming chemical bonds.

New, Michael H.↗
DOE OSTI2011

Syntheses, structures and luminescent properties of a series of 3D lanthanide coordination polymers with tripodal semirigid ligand

Reactions of the tripodal bridging ligand 5-(4-carboxy-phenoxy)-isophthalic acid (abbreviated as H{sub 3}cpia) with lanthanide salts lead to the formation of a family of different coordination polymers, that is, [Ln(cpia)(H{sub 2}O){sub 2}]{sub n}.nH{sub 2}O (Ln=Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Dy (7), Er (8), Tm (9) and Y (10)) in the presence of formic acid or diethylamine, which are characterized by elemental analysis, IR spectrum, thermogravimetric analysis (TGA), XRPD spectrum and single-crystal X-ray diffraction. Compounds 1-10 are isostructural and exhibit three-dimensional microporous frameworks. Furthermore, the photoluminescent properties of 4, 5 and 7 have been studied in detail. -- Graphical abstract: Reactions of the tripodal bridging ligand (H{sub 3}cpia) with lanthanide ions lead to the formation of a series of coordination polymers in the presence of formic acid or diethylamine. Display Omitted Research Highlights: {yields} Ten new lanthanides-based coordination polymers (1-10) have been synthesized. {yields} 1-10 exhibit 3D (4,8)-connected fluorite topology networks with 1D channel parallel to the b-axis. {yields} Compounds 4, 5 and 7 exhibit characteristic luminescence of Sm{sup 3+}, Eu{sup 3+} and Dy{sup 3+} ions, respectively.

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

Tuning of catalytic properties for electrooxidation of small organic molecules on Pt-based thin films via controlled thermal treatment

Ability to utilize structure-function relationship in the design of electrocatalysts relies on fundamental understanding of physicochemical processes at the topmost surface. It has been demonstrated that reaction rate for majority of electrochemical reactions exhibit notable dependence on geometric arrangement of surface atoms due to varying levels of binding strength between different atomic structures and adsorbate molecules. Control of surface structure at nanoscale is being investigated here through a thin film approach. The surface characteristics of electrochemically deposited Pt thin films were probed for electrooxidation of small organic molecules such as formic acid and methanol. The low-index Pt single crystal electrodes were used for reactivity benchmarking which later guided thermal annealing processes, and ultimately, fine tuning of the ratio between (1 1 1) and (1 0 0) surface facets on Pt thin films. Finally, the tailored thin film structure is responsible for significant activation of both formic acid and methanol oxidation reactions, which justifies the approach.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

High Efficiency Solar-based Catalytic Structure for CO 2 Reforming

Throughout this project, we developed and optimized various photocatalyst structures for CO 2 reforming into hydrocarbon fuels and various commodity chemical products. We also built several closed-loop and continuous fixed-bed photocatalytic reactor system prototypes for a larger-scale demonstration of CO 2 reforming into hydrocarbons, mainly methane and formic acid. The results achieved have indicated that with each type of reactor and structure, high reforming yields can be obtained by refining the structural and operational conditions of the reactor, as well as by using various sacrificial agents (hole scavengers). We have also demonstrated, for the first time, that an aqueous solution containing acid whey (a common bio waste) is a highly effective hole scavenger for a solar-based photocatalytic reactor system and can help reform CO 2 into several products at once. The optimization tasks performed throughout the project have resulted in efficiency increase in our conventional reactors from an initial 0.02% to about 0.25%, which is 10X higher than our original project goal. When acid whey was used as a sacrificial agent, the achieved energy efficiency for formic acid alone was ~0.4%, which is 16X that of our original project goal and higher than anything ever reported for a solar-based photocatalytic reactor. Therefore, by carefully selecting sacrificial agents, it should be possible to reach energy efficiency in the range of the photosynthetic efficiency of typical crop and biofuel plants (1-3%).

10 SYNTHETIC FUELS↗
DOE OSTI2012

COMPLEX ORGANIC MOLECULES AT HIGH SPATIAL RESOLUTION TOWARD ORION-KL. II. KINEMATICS

It has recently been suggested that chemical processing can shape the spatial distributions of complex molecules in the Orion-KL region and leads to the nitrogen-oxygen 'chemical differentiation' seen in previous observations of this source. Orion-KL is a very dynamic region, and it is therefore also possible that physical conditions can shape the molecular distributions in this source. Only high spatial resolution observations can provide the information needed to disentangle these effects. Here, we present millimeter imaging studies of Orion-KL at various beam sizes using the Combined Array for Research in Millimeter-wave Astronomy. We compare molecular images with high spatial resolution images that trace the temperature, density, and kinematics of the source in order to investigate the effects of physical conditions on molecular distributions. These observations were conducted at {lambda} = 3 mm and included transitions of ethyl cyanide [C{sub 2}H{sub 5}CN], methyl formate [HCOOCH{sub 3}], formic acid [HCOOH], acetone [(CH{sub 3}){sub 2}CO], SiO, and methanol [CH{sub 3}OH]. We find differences in the molecular distributions as a function of each of the aforementioned physical factors. These results indicate that acetone may be produced by chemical processing and is robust to large changes in physical conditions, while formic acid is readily destroyed by gas-phase processing in warm and dense regions. We also find that while the spatial distributions of ethyl cyanide and methyl formate are not distinct as is suggested by the concept of 'chemical differentiation', local physical conditions shape the small-scale emission structure for these species.

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

Laser formation of luminescence bubble microstructures in polymer films

The results of laser-induced formation of luminescent structures on the surface of poly-2.2’-n-oxydiphenylene-5.5’-bis-benzimidazole films, obtained by the coating method from a formic acid solution, are presented. The structures are formed using cw 405-nm laser radiation with intensities of 10{sup 2} – 10{sup 4} W cm{sup –2}. It is shown (using methods of optical, atomic-force, and electron microscopy) that the structures formed on the surface are microbubble foam-like aggregations. Their formation is modelled as a sequence of the following processes: release of formic acid molecules, their condensation on matrix defects in the surface layer, and explosive boiling as a result of heating this layer of polymer film by the laser beam. The luminescence of these structures is due to the weakening of the concentration quenching from closely spaced luminescence centres in benzimidazole cycles during their emergence to the surface and the increase in the distance between them due to the extension on bubble aggregates on the surface. (interaction of laser radiation with matter. laser plasma)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Extraction and reductive stripping of pertechnetate from spent nuclear fuel waste streams.

An approach directed at rapid sequestration and disposal of technetium-99 from UREX (uranium extraction) liquid waste streams is presented. This stream is generated during reprocessing of light-water-reactor spent fuel to recycle the actinides and separate fission products for waste disposal. U and Tc are co-extracted from a nitric acid solution using tri-n-butylphosphate in dodecane, so that Tc(VII) is present in the strip solution after the actinide separations. The goal is to separate uranyl from the pertechnetate in this U-Tc stream and then sequester Tc in the metallic form. Our approach is based on reductive stripping of pertechnetate either from aqueous solution (for column extractions) or organic solvents (for liquid-liquid extractions). In both of these methods, metallic zinc in the presence of formic acid serves as a reducing agent, and {sup 99}Tc is recovered as a co-precipitate of Zn(II) hydroxide and hydrous Tc(IV) oxide, with a Zn:Tc ratio between 1:1 and 2:1 mol/mol. This solid residue can be reduced to a Zn-Tc alloy by high temperature (500-700 C) hydrogenation, and the resulting heterophase alloy can be added to a metallic Fe-Zr-Mo waste form that is processed at 1600 C, with subsequent loss of Zn by evaporation. Alternatively, Zn and Tc can be separated and {sup 99}Tc sequestered as NH{sub 4}TcO{sub 4} for further reduction to Tc(0) metal. The aqueous Zn reduction process removes {approx}90% of {sup 99}Tc per cycle. The nonaqueous Zn reduction in 1:1 methanol-formic acid removes 60-70% of {sup 99}Tc per cycle, depending on the extracting agent (such as a tetraalkylammonium nitrate). The extracting agent is recycled in the process. The pertechnetate is extracted from the aqueous phase into 1,2-dichloroethane, which is removed by evaporation and reused. The residue is either calcined and steam reformed to Tc(0) or processed by the nonaqueous Zn reduction method. These methods can be used not only to remove the pertechnetate from the U-Tc product stream, but also to sequester the pertechnetate from aqueous waste streams generated through the processes described in this paper, thereby closing the cycle. The same approaches can be used to close the {sup 99}Tc cycle for other methods that are currently being developed at Los Alamos and Argonne National Laboratories.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

A Review of the Use of Immobilized Ionic Liquids in the Electrochemical Conversion of CO2

This paper is a review on the application of imidazolium-based ionic liquids tethered to polymer backbones in the electrochemical conversion of CO2 to carbon monoxide and formic acid. These tethered ionic liquids have been incorporated into novel anion ion exchange membranes for CO2 electrolysis, as well as for ionomers that have been incorporated into the cathode catalyst layer, providing a co-catalyst for the reduction reaction. In using these tethered ionic liquids in the cathode catalyst composition, the cell operating current increased by a factor of two or more. The Faradaic efficiencies also increased by 20–30%. This paper provides a review of the literature, in addition to providing some new experimental results from Dioxide Materials, in the electrochemical conversion of CO2 to CO and formic acid.

09 BIOMASS FUELS↗
DOE OSTI2020

Electrocatalysts, and fuel cells containing them

Provided are electrocatalysts, fuel cells, methods of making fuel cells, and methods of generating an electric current, each featuring a platinum (Pt)-containing substrate in contact with an aqueous solution comprising Pb2+. Electrocatalysts of the invention are formed via underpotential deposition (UPD) when a trace amount of Pb2+ is present in the electrolyte of a half anodic cell for oxidizing formic acid using Pt as the anode. Surprisingly, the UPD process dramatically enhances the activity of formic acid oxidation, at least as much as 10-fold compared with palladium (Pd) black. In an embodiment, the electrocatalyst comprises a Pt-containing substrate, a submonolayer of lead (Pb) adsorbed onto the Pt-containing substrate, and an aqueous solution comprising Pb2+, wherein the concentration of Pb2+ in the aqueous solution is 10 to 500 μm.

30 DIRECT ENERGY CONVERSION↗