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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Theoretical Models of Low-Resolution Microwave Rotational Spectra of Ethane- and Propanethiol

Additive modeling of low-resolution microwave spectra of heteroisomeric substituted hydrocarbons produced theoretical spectra of ethanethiol and propanethiol in the range 0–2 THz with maxima at 465 ± 20 and 240 ± 20 GHz. More precise calculations in a narrow frequency band of these ranges used spectral line half-widths of 1.5, 0.8, and 0.5 MHz that modeled conditions in different layers of Earth’s troposphere. The strongest extrema of the low-resolution spectra of the studied molecules were found at 486 ± 5, 446 ± 5, and 436 ± 5 (ethanethiol) and at 257 ± 5, 239 ± 5, and 234 ± 5 GHz (propanethiol). Various aspects of the application of the results were discussed.

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

Enhancing carbon nanotube production from carbon dioxide and ethane using bimetallic catalysts

Converting CO 2 into carbon nanotubes (CNTs) offers a promising way for CO 2 utilization and sequestration, potentially mitigating environmental impacts from anthropogenic emissions. This study reports that bimetallic CoFe catalysts can increase CNT production from the reaction of CO 2 and C 2 H 6 by an order of magnitude compared to their monometallic counterparts. The active sites and CNT morphologies are composition-dependent: Co-rich catalysts (Co/Fe ratio ≥ 5) form stable face-centered cubic (fcc) CoFe alloys, producing cylindrical CNTs; Fe-containing catalysts (Co/Fe ≤ 2) favor body-centered cubic (bcc) CoFe alloy upon reduction, which transforms into carbides, resulting in bamboo-like CNTs. Experimental evidence and DFT calculations reveal that adjacent Fe and Co atoms modulate CO and C x H y adsorption, regulating CNT production pathways through the CO Boudouard reaction and C 2 H 6 decomposition. In conclusion, these results highlight the dual benefits of bimetallic catalysts in enhancing CNT yield and controlling CNT morphology through adjustment of catalyst compositions.

58 GEOSCIENCES↗
DOE OSTI2017

Synthesis of zeolitic imidazolate framework-69 for adsorption separation of ethane and ethylene

The zeolitic imidazolate framework ZIF-69 with topology of GME has been synthesized successfully via a facile hydrothermal synthetic method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption measurements, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The ethane/ethylene separation potential was measured by single-component adsorption isotherms, and the selectivity was calculated based on the ideal adsorbed solution theory (IAST). SEM and TEM images confirmed that the as-synthesized seeds possessed a well-crystallized and uniform morphology, appearing as a flat hexagonal prism with double hexagonal pyramid heads. The obtained ZIF-69 exhibited a higher adsorption capacity of C{sub 2}H{sub 6} over C{sub 2}H{sub 4} at 100 kPa, and the C{sub 2}H{sub 6}/C{sub 2}H{sub 4} adsorption selectivity was about 1.7 at below 100 kPa. The outcome would provide a new insight into the study on the effective separation of ethane/ethylene using different topological structures of ZIFs. - Highlights: • The well-crystallized and uniform ZIF-69 seeds were successfully synthesized. • ZIF-69 exhibited great preferential adsorption of C{sub 2}H{sub 6} over C{sub 2}H{sub 4}, with the C{sub 2}H{sub 6} adsorption capacity of 2.2 mmol/g. • C{sub 2}H{sub 6}/C{sub 2}H{sub 4} adsorptive selectivity was about 1.7 at pressure below 100 kPa. • The isosteric heat of C{sub 2}H{sub 6} was around 26 kJ/mol, much lower compared to those π -complexation sorbents.

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

Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl{sub 2}F–CClF{sub 2}, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl{sub 2}F–CCl{sub 2}F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Effects of surface species and homogeneous reactions on rates and selectivity in ethane oxidation on oxide catalysts

Selective alkane oxidations on metal oxide catalysts involve complex mechanisms with multiple reactions in series and parallel, different types of reduced and oxidized surface species, and potential contributions from gas-phase reactions. We report kinetics and thermodynamics of elementary steps involved in C 2 H 6 -O 2 reactions on SiO 2 -supported small vanadium oxide domains are determined using density functional theory. These surface reactions together with gas-phase mechanisms are incorporated in kinetic simulations to determine how surface and gaseous reactions interact and contribute to rates and selectivity. The results show that gas-phase reactions within pore volumes in contact with the catalyst contribute significantly to C 2 H 6 activation rates, even at conditions where gas-phase reactions in empty volumes without catalyst are negligible. The majority of C 2 H 6 activations occur on the surface, via H abstraction by vanadium oxo species present at terminal lattice oxygens. The gas-phase activations via H-abstraction by OH radicals also exhibit significant contributions. The reduced centers formed by reactions at vanadium oxo species are re-oxidized rapidly and, therefore, are present in very small concentrations at reaction conditions. The re-oxidation steps lead to the formation of HO 2 radicals and surface peroxo species that are also rapidly consumed and are present in small concentrations. The peroxo species preferentially convert C 2 H 4 to its epoxide product and influence selectivity even at low concentrations. The gas-phase reactions decrease the concentrations of peroxo species and improve selectivity slightly. The effects of reaction conditions and catalyst site density provide further insights into how factors beyond conversions at lattice oxygens influence rates and selectivity in alkane oxidation reactions of significant industrial importance.

42 ENGINEERING↗
DOE OSTI2026

Dual Chemical Looping/Catalytic Process for Alkylation of Benzene With Ethane and Propane Yielding Ethylbenzene and Cumene Over Copper‐Containing Mordenite

Given the sustained demand for alkylated aromatics and the strained olefin market, there is an urgent need to develop efficient one‐step processes for the direct alkylation of aromatics using alkanes instead of olefins. Such technologies offer greater energy efficiency and sustainability by eliminating the need for separate, energy‐intensive alkane dehydrogenation steps. In this work, we report a dual chemical looping / catalytic process that couples alkane dehydrogenation with aromatic alkylation over a copper‐containing mordenite yielding up to 25% of alkylated aromatics with >97% selectivity per cycle. In situ MAS NMR and FTIR spectroscopies combined with DFT calculations showed that the alkylation of benzene with alkanes proceeds via a π‐bounded Cu(I)‐olefin intermediate, which subsequently interacts with benzene, catalyzed by Brønsted acid sites, leading to alkylated products that readily desorb from the active material into the gas phase. DFT calculations show that alkylation mediated solely by Cu(I) has prohibitively high barriers (>1.8 eV), whereas a bi‐functional pathway involving both Cu(I) and Brønsted acid sites can proceed with significantly lower barrier (0.8 eV) through a concerted C–C bond formation and proton transfer step.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗