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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Carbonyl Sulfide (OCS): Detections in Comets C/2002 T7 (LINEAR), C/2015 ER61 (PanSTARRS), and 21P/Giacobini-Zinner and Stringent Upper Limits in 46P/Wirtanen

Carbonyl sulfide(OCS)is one of the sulfur-bearing molecules detected in different astronomical environments, including comets. The present-day sulfur chemistry in comets may reveal much about the origin of these ices and their subsequent processing history. Cometary sulfur molecules such as H2S, H2CS, SO2, SO, CS, CS2,S2, and NShave been detected in many comets. However, OCS, the only sulfur-bearing species with fluorescence emission lines at infrared wavelengths, is under-represented in comet volatile studies, having been reported in only six comets so far. We targeted OCS with the NASA Infrared Telescope Facility in comets 46P/Wirtanen, 21P/Giacobini–Zinner, and C/2015 ER61(Pan STARRS)in 2017–2018 using the high-resolution iSHELL spectrograph, and in C/2002 T7(LINEAR)in 2004 using the heritage CSHELL spectrograph. In comet C/2015 ER61, the OCS abundance was similar to those measured in bright comets such as comets C/2012 S1(ISON)and C/1996 B2(Hyakutake), whereas in C/2002 T7 it was relatively depleted. Our OCS measurement in21P/Giacobini–Zinner is the first definitive detection of this molecule in a Jupiter-family comet from a ground-based facility and is close to the average OCS abundance determined in comet 67P/ Churyumov–Gerasimenko by the Rosetta mission. Our 3σupper limit for comet 46P/Wirtanen is the lowest reported OCS abundance in any comet. We present production rates and mixing ratios(with respect to H2O)for these comets and place our results in the context of comets measured to date

Mohammad Saki↗
DOE OSTI2022

Influence of the Molecular Structure on the Electrocatalytic Hydrogenation of Carbonyl Groups and H 2 Evolution on Pd

We investigated the electrocatalytic hydrogenation (ECH) of model aldehydes and ketones over carbon supported Pd in aqueous phase. We propose reaction mechanisms based on kinetic measurements and on spectroscopic and electrochemical characterization of the working catalyst. The reaction rates of ECH and of the H 2 evolution reaction (HER) vary with the applied electric potential following trends that strongly depend on the organic substrate. The intrinsic rates of hydrogenation and H 2 evolution are influenced, in opposing ways, by the sorption of the reacting organic substrate. Strong interactions, i.e., higher standard free energies of adsorption of the organic compound, induce high hydrogenation rates but decrease the overall currents. The fast hydrogenation kinetics produces a hydrogen-depleted environment that kinetically hinders the HER and the bulk phase transition of Pd to a H-rich bulk Pd hydride, which is triggered by the applied potential in the absence of reacting organic compounds. As consequence of strong organic-metal interactions, hydrogenation dominates at low overpotential. However, the coverages of organic substrates on the metal surface decrease and the rates of H 2 evolution surpass those of hydrogenation with increasingly negative electric potential. We determined the range of electric potential favoring hydrogenation on Pd and quantitatively deconvoluted the effects of the sorption of the organic compound, and of the rates of proton coupled electron transfers, on the kinetics of both ECH and HER. The results indicate that electrocatalysis offers hydrogenation pathways for polar molecules that are different and, in some cases, faster than those dominating in the absence of an external electric potential.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

A Carbene-Rich but Carbonyl-Poor [Ir 6 (IMe) 8 (CO) 2 H 14 ] 2+ Polyhydride Cluster as a Deactivation Product from Catalytic Glycerol Dehydrogenation

The title cluster, a deactivation product in the catalytic dehydrogenation of glycerol, was characterized by XRD, DFT calculations, HRMS, FTIR spectroscopy, and NMR spectroscopy. Experimental/computational studies located the 14 H ligands, and all 1H and 13C{1H} NMR resonances were assigned. The structure contains an unprecedented Ir6H14 core with two CO and eight IMe ligands.

catalysis (homogeneous), catalysis (heterogeneous)↗
DOE OSTI2015

Reduction of CO 2 by Pyridine Monoimine Molybdenum Carbonyl Complexes: Cooperative Metal–Ligand Binding of CO 2

Abstract [( Ar PMI)Mo(CO) 4 ] complexes (PMI=pyridine monoimine; Ar=Ph, 2,6‐di‐ iso ‐propylphenyl) were synthesized and their electrochemical properties were probed with cyclic voltammetry and infrared spectroelectrochemistry (IR‐SEC). The complexes undergo a reduction at more positive potentials than the related [(bipyridine)Mo(CO) 4 ] complex, which is ligand based according to IR‐SEC and DFT data. To probe the reaction product in more detail, stoichiometric chemical reduction and subsequent treatment with CO 2 resulted in the formation of a new product that is assigned as a ligand‐bound carboxylate, [( PMI)Mo(CO) 3 (CO 2 )] 2− , by NMR spectroscopic methods. The CO 2 adduct [( PMI)Mo(CO) 3 (CO 2 )] 2− could not be isolated and fully characterized. However, the CC coupling between the CO 2 molecule and the PDI ligand was confirmed by X‐ray crystallographic characterization of one of the decomposition products of [( PMI)Mo(CO) 3 (CO 2 )] 2− .

Sieh, Daniel↗
DOE OSTI2017

Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion

In this work, methyl benzoate, N , N -dimethylbenzamide, and benzophenone were reduced by U III [N(SiMe 3 ) 2 ] 3 resulting in uranium(IV) products. Reduction of benzophenone lead to U IV [OC ∙ Ph 2 )][N(SiMe 3 ) 2 ] 3 , ( 1.1 ) which forms the dinuclear complex, [N(SiMe 3 ) 2 ] 3 U IV (OCPhPh-CPh 2 O)U IV [N(SiMe 3 ) 2 ] 3 ( 1.2 ), through coupling of the ketyl radical species upon crystallization. Reaction of N , N -dimethylbenzamide with U III [N(SiMe 3 ) 2 ] 3 resulted in U IV [OC ∙ (Ph)(NMe 2 )][N(SiMe 3 ) 2 ] 3 ( 2 ), a uranium(IV) compound and the first example of a charge-separated amide radical. In the case of methyl benzoate, the reduction resulted in U IV (OMe)[N(SiMe 3 ) 2 ] 3 ( 3 ) and benzaldehyde as the reduced organic fragment. Compound 2 showed the ability to act as a uranium(III) synthon in its reactivity with trimethylsilyl azide, a reaction that yielded U V (=NSiMe 3 )[N(SiMe 3 ) 2 ] 3 . Additionally, 2 was reduced with potassium graphite resulting in [U(μ-O)[O=C(NMe 2 )(Ph)][N(SiMe 3 ) 2 ] 2 ] 2 ( 4 ), a dinuclear uranium compound bridged by oxo ligands. Reduction of 2 in the presence of 15-crown-5 afforded isolation of the mono-oxo compound, [(15-crown-5) 2 K][UO[N(SiMe 3 ) 2 ] 3 ] ( 5 ). Lastly, the results expand the reduction capabilities of U III complexes and demonstrate a strategy for isolating novel metal-stabilized radicals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Non-Oxidative Dehydrogenation Pathways for the Conversion of C 2 -C 4 Alcohols to Carbonyl Compounds

Gold nanoparticles (NPs) supported on hydrotalcite (Au/HT) are highly active and selective catalysts for the continuous, gas-phase, non-oxidative dehydrogenation of bioderived C 2 -C 4 alcohols. Here, a sharp increase in turn over frequency (TOF) is noted when the size of Au NPs is less than 5 nm relating to the strong synergy between metallic Au NPs and the acid-base groups on the support surface. It is demonstrated that catalytic activity depends critically on Au NP size, support composition, and support pretreatments. A reaction pathway elucidated from kinetic isotope effects suggests that the abstraction of β-H by Au NPs (C-H activation) is the rate-determining step in the dehydrogenation of bioderived C 2 -C 4 alcohols.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗