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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Catalytic N 2 Reduction to Silylamines and Thermodynamics of N 2 Binding at Square Planar Fe

The geometric constraints imposed by a tetradentate P4N2 ligand play an essential role in stabilizing square planar Fe complexes with changes in metal oxidation state. A combination of high-pressure electrochemistry and variable temperature UV-vis spectroscopy were used to obtain these thermodynamic measurements, while X-ray crystallography, 57Fe Mössbauer spectroscopy, and EPR spectroscopy were used to fully characterize these new compounds. Analysis of Fe0, FeI, and FeII complexes reveals that the free energy of N2 binding across three oxidation states spans more than 37 kcal mol-1. The square pyramidal Fe0(N2)(P4N2) complex catalyzes the conversion of N2 to N(SiR3)3 (R = Me, Et) at room temperature, representing the highest turnover number (TON) of any Fe-based N2 silylation catalyst to date (up to 65 equiv N(SiMe3)3 per Fe center). Elevated N2 pressures (> 1 atm) have a dramatic effect on catalysis, increasing N2 solubility and the thermodynamic N2 binding affinity at Fe0(N2)(P4N2). Acknowledgment. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences. EPR experiments were performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for the U.S. DOE. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. The authors thank Prof. Yisong Alex Guo at Carnegie Mellon University for recording Mössbauer data for some complexes and Emma Wellington and Kaye Kuphal for their assistance with the collection of Mössbauer data at Colgate University, Dr. Katarzyna Grubel for X-ray assistance, and Dr. Rosalie Chu for mass spectrometry assistance. The authors also thank Dr. Aaron Appel and Dr. Alex Kendall for helpful discussions.

iron, thermodynamics, dinitrogen, square planer, M↗
DOE OSTI2018

Combining CO 2 reduction with propane oxidative dehydrogenation over bimetallic catalysts

In this paper, the inherent variability and insufficiencies in the co-production of propylene from steam crackers has raised concerns regarding the global propylene production gap and has directed industry to develop more on-purpose propylene technologies. The oxidative dehydrogenation of propane by CO 2 (CO 2 -ODHP) can potentially fill this gap while consuming a greenhouse gas. Non-precious FeNi and precious NiPt catalysts supported on CeO 2 have been identified as promising catalysts for CO 2 -ODHP and dry reforming, respectively, in flow reactor studies conducted at 823 K. In-situ X-ray absorption spectroscopy measurements revealed the oxidation states of metals under reaction conditions and density functional theory calculations were utilized to identify the most favorable reaction pathways over the two types of catalysts.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

NOx reduction - The stream of change

Fluctuation in the composition of reactant gas mixtures often leads to activity and selectivity variations in automotive catalysts. Now, time-resolved operando spectroscopy sheds light on the transient changes of surface species for a commercially applied catalyst and leads to process optimization. This study demonstrates how application of high time-resolution operando X-ray absorption spectroscopy can open new avenues toward the understanding of structure/function relationships in heterogeneous catalysis under transient, non-steady state conditions.

Gao, Feng↗