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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Pore Aperture Control Toward Size‐Exclusion‐Based Hydrocarbon Separations

Metal–organic frameworks (MOFs) have been proposed as a promising material for non-thermal chemical separations owing to their high structural diversity and tunability. Here, we report the synthesis of a zinc-based MOF containing a three-dimensional (3D) linker, bicyclo[2.2.2]octane-1,4-dicarboxylic acid, with high thermal stability towards the separation of hexane isomers. The incorporation of the 3D linker enhances the structural stability and provides well-defined pore apertures/channels with sub-Ångstrom precision. This precision allowed for the separation of similarly sized hexane isomers based on subtle differences in their kinetic diameters. Multi-component liquid phase batch experiments confirmed the separation of hexanes mixture into linear, monobranched, and dibranched isomers. This work represents a significant milestone in the construction of stable Zn-based MOFs and the incorporation of 3D linkers as a potential solution to challenging separations.

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

Pore Aperture Control Toward Size‐Exclusion‐Based Hydrocarbon Separations

Abstract Metal–organic frameworks (MOFs) have been proposed as a promising material for non‐thermal chemical separations owing to their high structural diversity and tunability. Here, we report the synthesis of a zinc‐based MOF containing a three‐dimensional (3D) linker, bicyclo[2.2.2]octane‐1,4‐dicarboxylic acid, with high thermal stability towards the separation of hexane isomers. The incorporation of the 3D linker enhances the structural stability and provides well‐defined pore apertures/channels with sub‐Ångstrom precision. This precision allowed for the separation of similarly sized hexane isomers based on subtle differences in their kinetic diameters. Multi‐component liquid phase batch experiments confirmed the separation of hexanes mixture into linear, monobranched, and dibranched isomers. This work represents a significant milestone in the construction of stable Zn‐based MOFs and the incorporation of 3D linkers as a potential solution to challenging separations.

Lal, Bhajan↗
DOE OSTI2022

Non-equilibrium molecular dynamics simulation to evaluate the effect of confinement on fluid flow in silica nanopores

The flow of fluids in nano-confinement has applications in separations, water purification, medical systems and in the recovery of fluids in petroleum systems. It is believed that fluids do not obey continuum laws when flowing in nanopores (or in confinement). This paper attempts to shed light on various nano confinement effects such as fluid-wall interactions, pore size and molecular geometry, using molecular dynamic simulation. Here, water, hexane, and methanol flow behaviors were simulated for pore diameters ranging from 1 to 8 nm. In addition to the density analysis of the confined fluids, the fluid flows in saturated nanopores were simulated by the sectional flow method. Water and methanol molecules were completely stabilized in the 1 nm pore. Hexane molecules could not enter the 1 nm pore, due to geometric considerations. For the 2 – 8 nm pores, all fluids showed reduced flow rate compared to the Hagen–Poiseuille flow, due to an interfacial molecular layer stabilized at the pore surface. Flow reduction observed in these studies is contrary to significant flow enhancements observed for fluid flow in carbon nanotubes of similar dimensions. Water flow showed almost constant stick length for all the pore sizes. Methanol flow had the largest stick length. Hexane flow was reduced because of overcrowding of molecules at the pore surface. The effect of confinement diminished with an increase in pore diameter.

42 ENGINEERING↗
DOE OSTI2020

Learning Coarse-Grained Potentials for Binary Fluids

Even though atomistic and CG models have been used to simulate liquid nanodroplets in vapor, very few rigorous studies of the liquid-liquid interface structure are available, and most of them are limited to planar interfaces. In this work, we evaluate several existing force fields (FF)s, including two atomistic and three CG FFs, with respect to modeling the interface structure and thermodynamic properties of the water-hexane interface. Both atomistic FFs are able to quantitatively reproduce the interfacial tension and the coexisting densities of the experimentally-observed planar interface. We use the atomistic FFs to model water droplets in hexane and use these simulations to test the CG FFs. We found that the tested CG FFs cannot reproduce the interfacial tensions of planar and/or curved interfaces. Finally, we propose a new approach for learning coarse-grained (CG) potentials within the CG SDK (Shinoda-DeVane- Klein) FF framework from atomistic simulation data. We demonstrate that the new potential significantly improves the prediction of both the interfacial tension and structure of water-hexane planar and curved interfaces.

Gao, Peiyuan↗
DOE OSTI2025

Customizable Aperture Geometry in Metal–Organic Frameworks for Kinetic Hydrocarbon Separation

Precise control of aperture dimensions is crucial in adsorptive separations of hydrocarbons, as it directly affects key parameters such as selectivity, capacity, diffusion, and recyclability. The development of metal–organic frameworks (MOFs) has enabled the fine-tuning of local pore environments to address important hydrocarbon separations. However, customizing the aperture geometry to tune the kinetic separation performance remains challenging. Here, we deploy a mixed-linker synthesis strategy, combining long and short linkers on fcu net Zr-MOFs with equilateral triangular apertures to construct isoreticular multivariate MOFs, NU-415 and NU-416, with tailored isosceles triangular apertures suitable for the separation of hexane isomers. Sorption, liquid batch separation, and X-ray diffraction measurements demonstrate significantly improved selectivity, capacity, stability, and recyclability of NU-415 and NU-416 compared with Zr-muconate and MOF-801. Notably, both NU-415 and NU-416 achieve uptake capacities of 2.2 mmol g –1 in 1 min with an n-hexane to 2,2-dimethylbutane selectivity over 200 in an equimolar ternary mixture at ambient conditions, comparable to leading reported materials. Mechanistic studies confirm that separation performance is predominantly governed by significant kinetic differences rather than by thermodynamics. Furthermore, the successful customization of aperture geometry not only enables superior linear to monobranched hexane selectivity in NU-415 but also demonstrates the mixed-linker synthesis strategy as a promising solution for precise and predictable pore architecture control in MOFs.

Adsorption↗
DOE OSTI2020

Stabilization of Hydroxide Ions at the Interface of a Hydrophobic Monolayer on Water via Reduced Proton Transfer

We report a joint study using surface-specific sum-frequency vibrational spectroscopy and ab initio molecular dynamics simulations, respectively, on a pristine hydrophobic (sub)monolayer hexane-water interface, namely, the hexane/water interface with varied vapor pressures of hexane and different pHs in water. We show clear evidence that hexane on water revises the interfacial water structure in a way that stabilizes the hypercoordinated solvation structure and slows down the migration of hydroxide ion (OH – ) relative to that in bulk water. Furthermore, this mechanism effectively attracts the OH – to the water-hydrophobic interface with respect to its counterion. The result illustrates the striking difference of proton transfer of hydrated OH – at the interface and in the bulk, which is responsible for the intrinsic charging effect at the hydrophobic interface.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Characterization of Kariya ( Hildegardia barteri (Mast.) Kosterm) Seed Oil Fatty Acid Methyl Ester Prepared from Basic Catalytic Transesterification

The rising global energy demand, alongside concerns regarding environmental deterioration due to the use of fossil fuels, has spurred extensive investigation into renewable energy alternatives. Biomass-derived biodiesel, especially from lesser-known oil sources, emerges as a promising option. This research focuses on analyzing the fatty acid methyl esters (FAMEs) derived from Kariya (Hildegardia barteri (Mast.) Kosterm) seed oil through basic catalytic transesterification using gas chromatography–flame ionization detector (GC–FID) analysis, assessing its potential as a biodiesel feedstock. Oil extraction from Kariya seeds was carried out using three solvents (n-hexane, ethanol, and a 1:1 blend of hexane and ethanol), followed by transesterification with methanol. Gas chromatography–mass spectrometry (GC–MS) and GC–FID analyses were utilized to identify and quantify FAMEs in the resulting biodiesel. The results revealed various FAMEs, including methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, and methyl linolenate. Significant differences in FAME composition were observed among the samples, with hexane–ethanol Kariya oil biodiesel (HE-KOB) showing the highest FAME content (76.1%). This combination of solvents exhibited synergistic effects on the composition of HE-KOB, suggesting potential optimization strategies for biodiesel production. Fourier transform infrared spectroscopy (FTIR) provided additional insights into the molecular composition of the biodiesel samples, confirming their biodiesel nature through the identified functional groups such as methyl, methylene, hydrocarbon, ester, aldehyde, and alkene. Thermogravimetric analysis (TGA) for thermal decomposition also gave an insight into FAME composition and its contribution to the degree of conversion of biodiesel to energy. These findings highlight the feasibility of utilizing Kariya seed oil as a biodiesel feedstock, emphasizing the importance of solvent selection and transesterification conditions in optimizing FAME yield and composition. This research contributes to the exploration of underutilized oil sources for sustainable biodiesel production, aligning with the global shift towards cleaner and renewable energy sources.

09 BIOMASS FUELS↗
NASA NTRS1974

Release of volatile mercury from vascular plants

Volatile, organic solvent soluble mercury has been found in leaves and seeds of several angiosperms. Leaves of garlic vine, avocado, and haole-koa release mercury in volatile form rapidly at room temperature. In garlic vine, the most active release is temperature dependent, but does not parallel the vapor-pressure temperature relationship for mercury. Mercury can be trapped in nitric-perchloric acid digestion fluid, or n-hexane, but is lost from the hexane unless the acid mixture is present. Seeds of haole-koa also contain extractable mercury but volatility declines in the series n-hexane (90%), methanol (50%), water (10%). This suggests that reduced volatility may accompany solvolysis in the more polar media.

Siegel, S. M.↗
NASA NTRS1992

Dielectric constant of liquid alkanes and hydrocarbon mixtures

The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

NASA Program Exobiology↗
DOE OSTI2022

Enhanced Laplace Pressures for Functional Surfaces: Wicking, Switchability, and Selectivity

Abstract Wetting functionalities of rough surfaces are largely determined by the Laplace pressure generated across liquid–gas interfaces formed within surface structures. Typically, rough wetting surfaces create negative Laplace pressures, enabling capillary wicking, while rough non‐wetting surfaces create positive Laplace pressures, exhibiting fluid repellency. Here, with microfabricated reentrant structures, it is shown that the same surface can exhibit either a negative or positive Laplace pressure, regardless of its intrinsic wettability. This material‐independent Laplace pressure duality enables or enhances a range of wetting functionalities including wicking, switchability, and selectivity. On the same surface, capillary rise, capillary dip, and the combination of the two which leads to further enhancement of the total sustainable capillary height and Laplace pressure, the driving force for wicking is demonstrated. Further, active switching of wetting states between the hemiwicking and the repellent Cassie state on reentrant structures is shown. Moreover, with a water‐hexane mixture system, selective wetting of reentrant structures are demonstrated, that is, water can be selectively wicked or repelled in the presence of hexane, and vice versa. These functionalities are achieved, which would typically require complex chemical coatings, solely using surface structures, thus largely expanding the design space for a wide range of thermofluidic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Harnessing the potential of oilcane waste mud for recovering biobased waxes

Abstract Oilcane is an engineered sugarcane with the ability to hyper‐accumulate vegetative lipids. It is processed to obtain juice and bagasse as a potential substrate for the production of biofuels and biochemicals. The juice comprises solid particles that are separated as waste mud before the fermentation of the juice. In this study, the oilcane waste mud (OWM) generated from 1000 liters of oilcane juice was quantified and evaluated as a potential resource for recovering biobased waxes. Hexane and ethyl acetate were evaluated as two different solvents for extracting waxes from OWM followed by its purification using acetone. The extracted biobased wax samples were characterized for their chemical and thermal profiles which were then compared with commercial natural waxes. Detailed mass balance shows that 53.6 ± 2.6 kg (dry basis) of solid OWM gets generated upon processing 1000 L (~1068 kg) of oilcane juice. Hexane and ethyl acetate led to a crude wax yield of 25.6 ± 0.2% and 16.6 ± 0.4% (wt/wt, dry basis) respectively from OWM at the end of 8 h. The relative purification of the wax samples was reported in the range of 58%–65% (wt/wt). The purified OWM wax has a melting point of 74.7°C. The waste mud was valorized as a source of biobased waxes with characteristic chemical and thermal profiles comparable to commercial natural waxes (carnauba and beeswax). Considering the decline in the supply of petroleum wax in the future coupled with the switch to “greener” alternative products by consumers, OWM could be a valuable source of natural wax in the industrial sector reducing the dependence on petroleum waxes. Eventually, recovering biobased wax as a co‐product from OWM would bring in an additional stream of revenue leading to the development of a zero‐waste biorefinery based on bioenergy crops.

09 BIOMASS FUELS↗
DOE OSTI2020

Numerical study on spray collapse process of ECN spray G injector under flash boiling conditions

This work features a numerical study of the spray collapse process that occurs under flash-boiling, gasoline-direct-injection conditions. The Engine Combustion Network's Spray G injector was modeled, and iso-octane, n-hexane, and propane were used as fuels with the goal to investigate fuel property effects. The development of individual jets and jet-to-jet interaction were analyzed to reveal the physical mechanisms of spray collapse. The results agreed qualitatively well with the experimental data of propane available from the literature and the predictions revealed the model's ability to capture the near-nozzle shock structures witnessed in the experiments. Simulations showed that the flow development of flashing sprays was strongly tied with the fuel properties. Specifically, under-expanded jets were not observed with iso-octane due to the fuel's low vapor pressure. In the case of n-hexane, the jets were under-expanded, and a low-pressure core was observed inside the jets due to the flow expansion. With propane, the very strong expansion caused the flow to become transonic and generate a unique shock structure near the nozzle exit. The shock structure revealed the formation of primary shock cells within the jets and secondary shock cells induced by jet-to-jet interaction. Based on the results, the spray collapse under flash boiling conditions was mainly attributed to two effects, i.e., the decrease in pressure at the spray center induced by the low-pressure cores inside and between the jets, and the isolation effect due to the jet-to-jet interaction which contributed to maintain the pressure differential between the spray center and the ambient.

42 ENGINEERING↗
DOE OSTI2022

Unraveling 1-Hexene Hydrogenation over Dilute Pd-in-Au Alloys

Dilute Pd-in-Au alloys are valuable materials for selectively hydrogenating alkynes and isomerizing alkenes. By diluting Pd in a Au host, the selectivity toward semihydrogenated alkene isomers can be significantly enhanced and the unfavorable overhydrogenation to alkanes is suppressed. However, a detailed mechanistic study on the origin of the enhanced alkene selectivity over dilute alloy catalysts is still missing. Here, we combine experiment and theory to unravel the reaction mechanism, identifying rate-limiting and selectivity-controlling steps in 1-hexene hydrogenation over dilute Pd-in-Au catalysts. Using isotope-exchange hydrogenation experiments, we show that 1-hexene and hydrogen over a bimetallic Pd4Au96 in silica catalyst preferentially form 1-hexene isomers, (trans and cis) 2- and 3-hexene and only a small amounts of hexane. The reaction is consistent with a Horiuti–Polanyi mechanism, similar to a monometallic Pd nanoparticle catalyst. Computation of the free-energy profiles for 1-hexene hydrogenation and isomerization over a single Pd atom in a Au surface using first principles calculations indicated that the isomerization of 1-hexene to 2-hexene is energetically favorable due to the relatively large barrier for H2 dissociation preventing hydrogenation to n-hexane. Microkinetic modeling established that H2 dissociation on the single-atom Pd sites and H spillover from these sites onto the Au host are rate-limiting and key in steering the selectivity of dilute Pd-in-Au alloys toward the hexene isomers. Furthermore, the mechanistic insights from this study contribute to the rational design of optimized dilute alloy catalysts for selective alkene isomerization.

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

Data for Harnessing the Potential of Oilcane Waste Mud for Recovering Biobased Waxes

Oilcane is an engineered sugarcane with the ability to hyper-accumulate vegetative lipids. It is processed to obtain juice and bagasse as a potential substrate for the production of biofuels and biochemicals. The juice comprises solid particles that are separated as waste mud before the fermentation of the juice. In this study, the oilcane waste mud (OWM) generated from 1000 liters of oilcane juice was quantified and evaluated as a potential resource for recovering biobased waxes. Hexane and ethyl acetate were evaluated as two different solvents for extracting waxes from OWM followed by its purification using acetone. The extracted biobased wax samples were characterized for their chemical and thermal profiles which were then compared with commercial natural waxes. Detailed mass balance shows that 53.6 ± 2.6 kg (dry basis) of solid OWM gets generated upon processing 1000 L (~1068 kg) of oilcane juice. Hexane and ethyl acetate led to a crude wax yield of 25.6 ± 0.2% and 16.6 ± 0.4% (wt/wt, dry basis) respectively from OWM at the end of 8 h. The relative purification of the wax samples was reported in the range of 58%–65% (wt/wt). The purified OWM wax has a melting point of 74.7°C. The waste mud was valorized as a source of biobased waxes with characteristic chemical and thermal profiles comparable to commercial natural waxes (carnauba and beeswax). Considering the decline in the supply of petroleum wax in the future coupled with the switch to “greener” alternative products by consumers, OWM could be a valuable source of natural wax in the industrial sector reducing the dependence on petroleum waxes. Eventually, recovering biobased wax as a co-product from OWM would bring in an additional stream of revenue leading to the development of a zero-waste biorefinery based on bioenergy crops.

Biomass Analytics↗
DOE OSTI2022

Glycosylated stigmasterol from the rind of Napoleonaea imperialis

Napoleonaea imperialis rinds were separated from the seeds and extracted via maceration using methanol. The crude methanol extract was partitioned with n-hexane and dichloromethane to yield n-hexane fraction (11.01 g), dichloromethane fraction (35.16 g) and methanol fraction (101.75 g). Dichloromethane fraction was chromatographed and purified to give a compound whose structure was elucidated using one-dimension and two-dimension nuclear magnetic resonance (NMR) experiments. The isolated compound was characterized as glycosylated stigmasterol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Checking the statistical theory of liquids by ultraacoustic measurements

The manner of theoretically obtaining radial distribution functions 9(r) for n-hexane as a function of temperature is described. With the aid of function g(r) the coefficient of dynamic viscosity and the coefficient of volumetric viscosity for temperatures ranging from 213 K to 273 K were calculated. With the aid of the two coefficients of viscosity the coefficient of absorption of ultrasounds in n-hexane referred to the square of the frequency was determined. The same values were measured experimentally. Comparison of theory with experiments resulted in satisfactory agreement.

Dima, V. N.↗
NASA NTRS1982

Selective Etching of Semiconductor Glassivation

Selective etching technique removes portions of glassivation on a semi-conductor die for failure analysis or repairs. A periodontal needle attached to a plastic syringe is moved by a microprobe. Syringe is filled with a glass etch. A drop of hexane and vacuum pump oil is placed on microcircuit die and hexane is allowed to evaporate leaving a thin film of oil. Microprobe brings needle into contact with area of die to be etched.

Casper, N.↗