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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Gas-phase dehydration of tetrahydrofurfuryl alcohol to dihydropyran over γ-Al 2 O 3

Gas-phase dehydration of tetrahydrofurfuryl alcohol (THFA) to 3,4-2H-dihydropyran (DHP) was investigated over solid acid catalysts. A γ-Al 2 O 3 catalyst resulted in 90% DHP yield from THFA. The γ-Al 2 O 3 deactivated due to solid coke formation but was nearly fully re-generable upon a high temperature calcination step (only 2.5% activity loss after 3 rd regeneration). The high catalytic activity and selectivity of γ-Al 2 O 3 was correlated to its high Lewis to Brønsted acid site ratio, as confirmed by ammonia temperature-programmed desorption (NH 3 -TPD) and isopropylamine temperature-programmed desorption (IPA-TPD). According to isotopic-labelling studies, a reaction mechanism was proposed in which THFA initially dehydrates into a carbenium intermediate prior to Wagner-Meerwien rearrangement into DHP. A kinetic model of THFA dehydration over γ-Al 2 O 3 was developed according to kinetic experimental data. The best-fit model implied the rate-determining step was the surface reaction of adsorbed THFA dissociating into adsorbed DHP and water.

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

The effect of CO on CO2 methanation over Ru/Al2O3 catalysts: a combined steady-state reactivity and transient DRIFT spectroscopy study

The reactivity of Ru/Al2O3 catalysts in the hydrogenation of CO/CO2 gas mixtures is investigated in this work. Accordingly kinetic measurements are carried out at process conditions of industrial interest (i.e., at high COx per-pass conversion and with concentrated COx/H2 streams), and the surface species on the catalyst are investigated through transient DRIFTS-MS analysis. The catalyst shows gradual deactivation when the methanation is carried out in the presence of CO in the gas feed at low temperatures (200-300 °C). However, stable performance is observed at higher temperatures, showing CH4 yields even higher than those observed during methanation of a pure CO2 feed. The catalyst deactivation at low temperature is reversible as thermal treatments at temperatures above 350 °C are able to restore the catalytic activity. DRIFTS-MS experiments revealed that CO2 methanation involves a reaction pathway where CO2 is adsorbed as bicarbonate on Al2O3 and successively hydrogenated to methane on Ru, passing through formate and carbonyl intermediates. In the presence of CO at low temperatures, the catalyst shows a higher CO coverage of the Ru sites, a larger formate coverage of alumina sites and the presence of adsorbed carbonaceous species, identified as hydrocarbon and carboxylate species. Carboxylates remain on the surface, effectively blocking adsorption sites thus leading to catalyst deactivation. However, working above the carboxylate decomposition temperature ensures a clean catalyst surface, resulting in stable and high performance in CO/CO2 methanation. Catalyst preparation, characterization and testing activity were carried out with a joint project between the Politecnico di Milano and the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), which is gratefully acknowledged. The authors gratefully acknowledge the financial support of the DRIFTS experiments by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. L.F. also acknowledges the Pacific Northwest National Laboratory (PNNL) for the financial support during his permanence as visiting student.

Methanation, Power-to-gas, Ru/Al2O3 catalyst, cata↗
DOE OSTI2026

Disentangling interlayer confinement and pore surface adsorption in functionalized smectites for tunable ethylene gas capture

Smectite-based adsorbents are increasingly being studied as sustainable packaging materials for scavenging ethylene, a plant hormone that accelerates fruit ripening. However, the mechanisms governing their uptake and retention remain poorly understood. Here, to tackle this question we systematically investigate ethylene gas-solid interactions in pristine, acid-activated, and choline-functionalized montmorillonites using a complementary combination of structural, gravimetric, and spectroscopic techniques, including inelastic neutron scattering. We experimentally distinguish ethylene populations associated with interlayer confinement, mesopore, and external surface adsorption. We show that chemical functionalization distinctly controls adsorption pathways: acid activation enhances total uptake by generating mesoporous adsorption sites and promoting partial interlayer intercalation, yielding capacities comparable to those of leading smectite-based adsorbents, while choline functionalization promotes preferential confinement and stabilization of guest molecules within the interlayer galleries. Advanced spectroscopic analysis provides molecular-level insight into confinement environments and interaction strengths. We also establish clear structure-property relationships by correlating uptake values derived from independent techniques, linking chemical modification, accessible adsorption domains, and retention behavior. These findings provide general design principles for tuning gas-solid interactions in functionalized layered silicates and highlight their potential as adaptable platforms for sustainable ethylene gas capture and selective adsorption technologies.

Ethylene adsorption mechanism↗
DOE OSTI2020

The potential application of VS 2 as an electrode material for Mg ion battery: A DFT study

Herein, by means of first-principle calculations based on density functional theory (DFT), the electrochemical properties of monolayer VS 2 (M-VS 2 ), double-layer VS 2 (D-VS 2 ) and bulk VS 2 (B-VS 2 ) as electrode materials for Mg-ion batteries (MIBs) were comprehensively explored. The computation results reveal that Mg atom can strongly bind with the three different forms of VS 2 . All of the Mg adsorbed VS 2 systems demonstrate metallic characteristics, which indicates a good electronic conductivity. In addition, crystal orbital hamiltonian population shows that the stability of V-S bond is weakened after adsorption of Mg atom. The low diffusion barriers of Mg give rise to the high rate performance of VS 2 in MIBs. More interestingly, the three types of VS 2 display same storage ability for Mg cations, which can adsorb 0.5 Mg atoms for VS 2 , producing maximum theoretical capacity 233 mA h g -1 for MIBs. Furthermore, the average working voltages results suggest that M-VS 2 can be employed as anode materials, while D-VS 2 , B-VS 2 can be used as cathode materials for MIBs.

25 ENERGY STORAGE↗
DOE OSTI2022

Thermal stability and protective properties of phenylphosphonic acid on Cu(111)

Phenylphosphonic acid (PPA) adsorbed on Cu(111) has been studied by synchrotron radiation-based techniques in combination with density functional theory calculations. Here, the dehydrogenated phenylphosphonic acid molecule (PP) strongly bound in a tridentate geometry through oxygen atoms to Cu(111) is shown to be the dominant surface species in the temperature range 150–300 °C. The stable PP adlayer substantially protects the Cu(111) surface from oxidation during exposure to ambient conditions. Thermal treatment of the PPA adlayer at 375 °C initiates molecular decomposition through several channels: P–O bond scission forming C 6 H 5 PO 2 ; C–P bond scission forming phenyl and PO 3 ; and C–H bond scission forming C 6 H 4 PO 3 . All three reaction steps have activation barriers of 1.7–1.8 eV. Small products such as O, H, and phenyl can immediately react further and desorb, while the remaining phosphonate species undergo condensation. After annealing at a higher temperature, the phosphonate group is further reduced from oxygen-rich to phosphorus-rich species, which form the majority of remaining adsorbates after 500 °C treatment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Product-promoted acetylene cyclotrimerization to benzene on Ag(111)

Acetylene cyclotrimerization to benzene on Ag(111) has recently been found to be 100% selective. However, it requires monolayer coverages, limiting its practical application due to the high pressure required to attain this surface coverage of acetylene near room temperature. Here, we show that co-adsorbed benzene, the reaction product, promotes cyclotrimerization at submonolayer acetylene coverages without compromising the 100% selectivity of Ag(111) via temperature-programmed desorption experiments. Scanning tunneling microscopy and density functional theory (DFT) calculations elucidate the origin of this effect whereby attractive acetylene–benzene interactions locally compress acetylene domains. DFT calculations further illustrate how co-adsorbed benzene reduces the transition-state energy for formation of the key C 4 intermediate, making cyclotrimerization competitive with desorption. Together, these findings reveal how product-reactant interactions can enhance C–C coupling.

Acetylene cyclotrimerization↗
DOE OSTI2016

Large-pore mesoporous silica nanospheres as vehicles for delivering TRAF3-shRNA plasmids to Kupffer cells

The currently available techniques for transferring exogenous genes into macrophages, especially the targeted import of exogenous genes into Kupffer cells (KCs) in vivo, are inefficient and achieve only low targeting. Novel Large-Pore Mesoporous Silica Nanospheres (LPMSNs) may be a promising gene transfection agent for KCs because of their superior biodegradation and hypotoxic characteristics, as well as their ability to retain the biological function of KCs and the high loading-rate of exogenous plasmid. LPMSNs were able to completely adsorb shRNA-TRAF3 (tumor necrosis factor receptor-associated factor-3) plasmid at a mass ratio as low as 30:1, and exhibited a low cytotoxicity for KCs. LPMSNs were detected in KC cytoplasm in vitro, and transmission electron microscopy (TEM) revealed that they were present only in KCs in liver tissue in vivo. The max KC transfection efficiency with LPMSNs was 34.8± 0.07%, as evaluated using flow cytometry, and the protein and mRNA levels of TRAF3 were significantly inhibited (P < 0.05) by shRNA-TRAF3 plasmid transfection after 24 h in vitro and 48 h in vivo. In conclusion, KC targeted transfection was achieved successfully by LPMSNs carrying shRNA-TRAF3 plasmids in vitro and vivo. The protein and mRNA levels of TRAF3 were suppressed significantly. These results suggest that LPMSNs are a promising vehicle for delivering exogenous genes into KCs in vitro and vivo. - Highlights: • We constructed Large-Pore Mesoporous Silica Nanospheres (LPMSNs). • LPMSNs adsorbed high quantity of plasmid. • Low cytotoxicity of LPMSNs to Kupffer cells. • LPMSNs delivered plasmid into Kupffer cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

The role of correlation and solvation in ion interactions with B-DNA

Ionic atmosphere around nucleic acids plays important roles in biological function. Large-scale explicit solvent simulations coupled to experimental assays such as anomalous small-angle X-ray scattering (ASAXS) can provide important insights into the structure and energetics of the ionic atmosphere but are time- and resource-intensive. In this paper, we demonstrate the use of classical density functional theory to model DNA-ion interactions and explore the balance between ion-DNA, ion-water, and ion-ion interactions. In particular, we compute the distribution of RbCl, SrCl2, and CoHexCl3 (cobalt hexammine chlo- ride) around a B-form DNA molecule. The accuracy of the DFT calculations was assessed by comparison between simulated and experimental ASAXS curves. As expected, these calculations revealed significant differences between the monovalent, divalent, and trivalent cations. About half of the DNA-bound Rb+ ions penetrate into the minor groove of the DNA and half adsorb on the DNA strands. The fraction of cations in the minor groove decreases for the larger Sr2+ ions and becomes zero for CoHex3+ ions, which all adsorb on the DNA strands. The distribution of CoHex3+ ions is mainly determined by Coulomb interactions, while ion-correlation forces play a central role in the monovalent Rb+ distribution and a combination of ion-correlation and hydration forces affect the Sr2+ distribution around DNA.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Synthesis, characterization and thermodynamic study of carbon dioxide adsorption on akaganéite

A mixture of akaganeite nanoparticles and sodium salts was synthesized and modi fied, first by washing, and then by Li exchange. The structural characterization of the produced materials was performed with: powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis, diffuse reflectance infrared Fourier transform spectrometry, Mossbauer spectros- € copy and magnetization measurements. Additionally low pressure nitrogen and high pressure carbon dioxide adsorption experiments were performed. The sum of the characterization information made possible to conclude that the produced akaganeite phases crystallized in a structure exhibiting the symmetry of the I2/m space group, where the measured equivalent spherical diameter of the akaganeite crystallites yielded 9 nm, as well, the tested phases exhibited a standard behaviour under heating and displayed a superparamagnetic behaviour. Finally the high pressure carbon dioxide adsorption experiments demonstrated a pressure-responsive framework opening event due to a structural transformation of the adsorbent framework induced by the guest molecules. This fact opens new applications for akaganeite as a high pressure adsorbent.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

CO 2 capture in lignin-derived and nitrogen-doped hierarchical porous carbons

Here, nitrogen-doped and hierarchical porous carbons were synthesized from lignin precursor by KOH and NH 3 activation with BET surface area of 1631–2922 m 2 /g. X-ray photoelectron spectroscopy (XPS) revealed 5.6–7.1 at.% nitrogen with predominantly pyridinic, amino and pyrrolic/pyridonic type of functionality. Maximum CO 2 adsorption capacity at 298 K and 273 K and pressure upto 760 torr (1 bar) was found to be 5.48 and 8.6 mmol/g respectively, which is higher than that of majority of nitrogen-doped carbons, reported in literature. Ideal Adsorbed Solution Theory (IAST)-based selectivity for CO 2 /N 2 revealed that selectivity increases with the increase in nitrogen content. IAST calculations were also employed to calculate the binary adsorption isotherms to simulate mixed gas adsorption for CO 2 and N 2 as a function of total pressure and mole fraction of CO 2 in the gas mixture. Continuous CO 2 adsorption-desorption studies for 10 cycles revealed that all the nitrogen-doped carbons retained its working capacity at the end of the cycles. Finally, a breakthrough study for (10/90) CO 2 /N 2 mixture in a dynamic column experiment confirmed a physical separation of the two components. The overall results suggest that nitrogen-doped carbons from lignin can be used as potential adsorbents for CO 2 capture purposes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Ultrafast molecular transport on carbon surfaces: The diffusion of ammonia on graphite

We present a combined experimental and theoretical study of the self-diffusion of ammonia on exfoliated graphite. Using neutron time-of-flight spectroscopy we are able to resolve the ultrafast diffusion process of adsorbed ammonia, NH 3 , on graphite. Together with van der Waals corrected density functional theory calculations we show that the diffusion of NH 3 follows a hopping motion on a weakly corrugated potential energy surface with an activation energy of about 4 meV which is particularly low for this type of diffusive motion. The hopping motion includes further a significant number of long jumps and the diffusion constant of ammonia adsorbed on graphite is determined with D = 3.9•10 -8 m 2 /s at 94 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Catalytic descriptors and electronic properties of single-site catalysts for ethene dimerization to 1-butene

Six first-row transition metal cations (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) were evaluated as catalysts for ethene dimerization to 1-butene. This is an important reaction in the chemistry of C—C bond formation and in the conversion of natural gas to higher hydrocarbons. Two related classes of transition metal cation catalysts were investigated: 1) single transition metal cations supported on zirconium oxide nodes of the metal–organic framework NU-1000 and 2) small metal hydroxide clusters with two metal atoms (M 2 ) that could be grown by atomic layer deposition on a support exhibiting isolated hydroxyl groups. Using scaling relations, the free energies of co-adsorbed hydrogen and ethene (i.e., (H/C 2 H 4 )*) and adsorbed ethyl (i.e., C 2 H 5 *) were identified as descriptors for ethene dimerization catalysis. Using degree of rate control analysis, it was determined that the rate controlling steps are either ethene insertion (C—C bond forming) or β-hydride elimination (C—H bond breaking), depending on the metal. Using degree of catalyst control analysis, it was determined that activity on all the catalysts studied could be improved by tuning the free energy of C 2 H 5 *.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Promotion of Pd nanoparticles by Fe and formation of a Pd 3 Fe intermetallic alloy for propane dehydrogenation

In this study, silica supported Pd (~2 nm), Pd 3 Fe (~2 nm) and Pd 3 Fe_large (~12 nm) catalysts were synthesized and tested for propane dehydrogenation at 510 °C. At the 10% conversion, Pd and Pd 3 Fe catalysts exhibited propylene selectivity of 45% and 94%, respectively. Moreover, the latter showed a turnover rate (TOR) of 0.2 s -1 , which is five times higher than that of the Pd catalyst (0.04 s -1 ). Pd K edge XAS, XRD, and CO adsorbed IR were used to characterize the geometric structure of the catalysts. By combined comparison of XRD and XAS spectra of Pd 3 Fe and Pd 3 Fe_large catalysts, we successfully identified the crystalline phase in the 2 nm Pd 3 Fe catalyst. The CO adsorbed IR suggests that the formation of Pd 3 Fe breaks the ensemble of Pd, which is responsible for the increase of selectivity. The Pd L edge XAS was used to characterize the electronic structure of the catalysts. The Pd 3 Fe catalyst exhibits an increase of the edge energy compared with the Pd catalyst, which indicates the change of d-band structure in the bimetallic catalyst. The change in the electronic structure is likely the reason for the increase in TOR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Superior lithium adsorption and required magnetic separation behavior of iron-doped lithium ion-sieves

The recent research on adsorption-based lithium recovery from lithium-containing solutions has been centred on adsorption capacity and separation of lithium ion-sieves powder from solutions. Herein, an effective iron-doped lithium titanium oxide (Fe-doped Li 2 TiO 3 ) was synthesized by Fe-doping via solid state reactions followed by acid treatment to form iron-doped lithium ion-sieves (Fe/Ti-x(H)). The resulting solid powder displays both superior adsorption capacity of lithium and high separation efficiency of the adsorbent from the solutions. SEM imaging and BET surface area measurement results showed that at Fe doping levels x ≤ 0.15, Fe-doping led to grain shrinkage as compared to Li 2 TiO 3 and at the same time the BET surface area increased. The Fe/Ti-0.15(H) exhibited saturated magnetization values of 13.76 emu g -1 , allowing effective separation of the material from solid suspensions through the use of a magnet. Consecutive magnetic separation results suggested that the Fe/Ti-0.15(H) powders could be applied at large-scale and continuously removed from LiOH solutions with separation efficiency of 96% or better. Lithium adsorption studies indicated that the equilibrium adsorption capacity of Fe/Ti-0.15(H) in LiOH solutions (1.8 g L -1 Li, pH 12) reached 53.3 mg g -1 within 24 h, which was higher than that of pristine Li 2 TiO 3 (50.5 mg g-1) without Fe doping. Competitive adsorption and regeneration results indicated that the Fe/Ti-0.15(H) possessed a high selectivity for Li with facile regeneration. Therefore, it could be expected that the iron-doped lithium ion-sieves have practical applicability potential for large scale lithium extraction and recovery from lithium-bearing solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

On the pressure and temperature dependence of adsorption densities and other thermodynamic properties in gas shales

Black shale source rocks have become a key natural gas resource in the US and China. Unlike in conventional hydrocarbon reservoirs, a significant fraction of the gas in shales is adsorbed onto the inordinate specific surface areas (SSA) of micropores inside organic matter with densities exceeding those of bulk gas by an order of magnitude. Yet, the distribution of adsorbed versus bulk gas remains poorly understood. Experiments measure excess adsorption isotherms, which are corrected to absolute adsorption amounts by a factor that involves the density, &#x3C1; abs , of the adsorption layer(s). Constant values of &#x3C1; abs are widely used in the literature but, we argue, are inconsistent with the pressure- and temperature-dependence of adsorption behavior. In this work, we propose a more reliable approach that assumes a constant volume of each adsorption layer that can be determined from the SSA of the substrate. We measure nine high-pressure methane excess adsorption isotherms up to 15 MPa for three shale samples from China and Germany at temperatures of 65, 75, and 95 °C, and low-pressure carbon dioxide and nitrogen isotherms to estimate the SSA. We also investigate another 24 isotherms at 35, 50, and 60° C or 8 Chinese shale samples and 3 isotherms at 60, 90, and 120° C for an Argentinian shale sample from the literature. A new variation of the multi-layer Ono-Kondo lattice model is introduced to derive the temperature and pressure dependent adsorption layer densities, which are subsequently used to obtain the absolute adsorption isotherms of interest. Finally, this practical methodology has the potential to significantly improve our estimates of shale gas-in-place resources, and adsorption modeling more broadly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Mechanisms of Zn removal from water by amorphous geopolymer: Molecular-level insights from X-ray absorption spectroscopy, isotope fractionation, and surface complexation modeling

Porous geopolymers have attracted widespread attention as promising heavy metal adsorbents that can be synthesized from aluminosilicate solid wastes. However, the precise microstructural evidence for adsorbed heavy metals on geopolymers remains unclear due to the insensitivity of conventional characterization techniques on minerals with amorphous structure and surface disorder. Batch adsorption and column experiments coupled with X-ray absorption spectroscopy (XAS), Zn stable isotope, and surface complexation model (SCM) were employed to reveal the Zn removal mechanisms with coal fly ash porous geopolymer (CFAPG) at a molecular scale. The macroscopic kinetic and isothermal adsorption of Zn on CFAPG were well described by the pseudo-second-order model and Bi_Langmuir equation, respectively, indicating the presence of abundant heterogeneous active sites on the CFAPG surface. Further, two types of active sites on the CFAPG surface were identified by XAS coupled with Zn isotopes in batch experiments at pH <= 6.0: one is pH-dependent and associated with tetrahedral zinc coordi-nation, and the other is pH-insensitive and associated with octahedral zinc coordination; these sites were confirmed by the bidentate SCM as the variable charge site (surface complexation, >S-OH) and the permanent negative charge site (cation exchange, >X - ), respectively. Furthermore, the important contribution of surface co -precipitation besides surface complexation and cation exchange to the Zn adsorption on CFAPG was identified by XAS coupled with SCM in a flow-through column experiment at pH >6.0. These investigations provide a systemic understanding of the Zn adsorption mechanisms on CFAPG and an SCM reference for the application and prediction of geopolymers in heavy metal-contaminated water remediations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Ru/MgO catalyst with dual Ru structure sites for efficient CO production from CO 2 hydrogenation

The development and comprehension of supported metal catalysts for CO 2 hydrogenation is of paramount importance in mitigating the net CO 2 emissions. Supported Ru catalysts have been widely recognized in facilitating CO 2 methanation, on which recent findings suggest that the CO 2 hydrogenation process can be manipulated to favor the reverse water–gas shift (RWGS) pathway by precisely adjusting the size of Ru particles. However, the size-dependent impact of Ru remains a topic of lively debate. In this work, Ru/MgO catalysts with Ru in the form of single atoms (Ru 1 ) and few-atom cluster (Ru FAC ) structures were prepared for CO 2 hydrogenation. The 1.0Ru/MgO catalyst (with 1 wt.% of Ru), featuring a mixture of Ru 1 and Ru FAC with a size of 0.6–1.0 nm, showed the highest CO yield (38% at 500 °C) with balanced CO 2 conversion and CO selectivity. Transient CO 2 hydrogenation and temperature-programmed surface reaction (TPSR) studies suggested that the adsorbed CO 2 species participated in CO 2 hydrogenation. On Ru 1 sites, CO 2 hydrogenation followed the RWGS pathway, resulting in the production of CO. In contrast, on Ru FAC sites, the enhanced H 2 dissociation ability, along with the presence of adsorbed bidentate and monodentate carbonate species at the Ru-MgO interfaces, facilitated the formation of CH 4 through the CO 2 methanation pathway. In conclusion, this study highlights the critical roles of Ru structure and local environment in defining the CO 2 hydrogenation pathways and provides new design principles for highly active Ru-based catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗