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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

An experimental and kinetic modeling study of the pyrolysis of isoprene, a significant biogenic hydrocarbon in naturally occurring vegetation fires

Isoprene dominates the carbon flux emitted by vegetation and constitutes 40% of non-methane biogenic emissions worldwide. Despite pyrolysis experiments at temperatures above 1000 K showing a link between isoprene combustion and aromatic species formation, comprehensive mechanistic research on isoprene is scarce in the literature. Here, in this work, we carry out an experimental and theoretical study to build, for the first time, a chemical kinetic model describing isoprene pyrolysis. The formation of polycyclic aromatic hydrocarbon (PAH) precursor species, often observed in vegetation fire plumes, is partially explained by isoprene pyrolysis experiments and theoretical modeling. Molecular dynamics (MD) simulations unveil reaction pathways from allylic isoprenyl radicals to allene and cyclopentadiene (CPD) intermediates, two relevant species detected in the experiments. Rate constants for these identified pathways are calculated using variational transition state theory to update the kinetic model, which is validated against single-pulse shock tube (SPST), and jet-stirred reactor (JSR) experimental data in the temperature range of 850–1690 K. The kinetic model presents satisfactory agreement with the SPST experimental data, and a reaction pathway analysis shows that association of propargyl radicals results in benzene formation. The JSR pathway analysis also identifies the prominent reactions for CPD, benzene, styrene, and toluene formation. Our model does not reproduce the CPD experimental profiles, indicating that additional studies are necessary. Overall, our findings advance the understanding of isoprene pyrolysis and its related atmospheric pollutants in naturally occurring vegetation fires where smoldering and oxygen-deficient combustion processes are present.

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

The Superfund Research Program Analytics Portal: linking environmental chemical exposure to biological phenotypes

The OSU/PNNL Superfund Research Program represents a longstanding collaboration to quantify Polycyclic Aromatic Hydrocarbons (PAHs) at various superfund sites in the Pacific Northwest and assess their potential impact on human health. To link the chemical measurements to biological activity, we describe the use of the zebrafish as a high-throughput developmental model of human exposure that provides quantitative measurements of the biological ramifications of exposure to toxicants. Toward this end, we have linked over 150 PAHs found at Superfund sites to the effect of these same chemicals in zebrafish, creating a rich dataset that links environmental exposure to biological response. To quantify this response, we have implemented a dose-response modelling pipeline to calculate benchmark dose parameters which enable potency comparison across over 500 chemicals and 10 zebrafish-specific phenotypes. Our portal provides public access to this dataset via an interactive web site designed to support exploration and re-use of these data by the scientific community at http://srp.pnnl.gov.

Gosline, Sara JC↗
DOE OSTI2026

Concordant Mode Approach (CMA): Vibrational Analysis of New and Upgraded Intermolecular Benchmarks for Noncovalent Bonding

The Concordant Mode Approach (CMA) is a novel method that offers tremendous potential for increasing the system size and the level of theory attainable in quantum chemical computations of molecular vibrational frequencies. To investigate the extension of CMA to intermolecular vibrations, computations with coupled cluster singles and doubles with perturbative triples theory [CCSD(T)] using two augmented correlation-consistent polarized-valence triple-ζ basis sets (aug-cc-pVTZ or h-aug-ccpVTZ) were performed on 17 prototypical loosely bound complexes of hydrogen-bonded, dispersion, and mixed character. These Level A results provide new and upgraded benchmarks for noncovalent bonding and a severe test for CMA vibrational analyses. The Level A target frequencies were recovered remarkably well using second-order Møller−Plesset perturbation theory (MP2) with h-aug-cc-pVTZ for generating the underlying (Level B) normal modes of the CMA scheme. Employing this Level B within the lowest-rung CMA-0A method reproduces the 435 benchmark frequencies with a mean absolute error (MAE) of 0.23 cm −1 and a corresponding standard deviation (σ) of 0.84 cm −1 ; strikingly, the corresponding subset of 106 interfragment frequencies exhibits MAE = 0.34 cm −1 and σ = 0.90 cm −1 . Subsequent application of the higher-rung CMA-2A scheme eliminates all outliers and reduces the overall MAE to a minuscule 0.08 cm −1 with the inclusion of only 3.0% of the off-diagonal couplings not accounted for by CMA-0A. Accordingly, the highly efficient CMA methodology proves to be robust even for vibrations on flat potential energy surfaces.

Aromatic compounds↗
DOE OSTI2020

Effects of the advanced organosolv pretreatment strategies on structural properties of woody biomass

Plants have evolved their lignocellulosic cell walls through complex structural and chemical mechanisms to protect itself against microbial attacks, which makes native lignocellulosic biomass recalcitrant to enzymatic deconstruction. Pretreatment is a crucial step in the biological conversion of biomass as it can render structural changes in the plant cell wall to reduce the biomass recalcitrance, thus enhancing its sugar release performance. There have been many efforts to develop effective pretreatment technologies to overcome the biomass recalcitrance with a primary focus on the efficient conversion of biomass carbohydrates to liquid fuels, while lignin is significantly underutilized despite its bulk amount and high-value opportunities. In this study, the effects of two recent organosolv pretreatment strategies, co-solvent enhanced lignocellulosic fractionation (CELF) and γ-Valerolactone (GVL) pretreatments, on physicochemical properties of poplar were investigated and compared with the effects of conventional ethanol organosolv pretreatment. Diverse physicochemical properties of biomass including chemical compositions, molecular weights of cellulose and lignin, aromatics and inter-unit linkages of lignin, lignin hydroxyl group contents, cellulose crystallinity, and accessible surface area of cellulose were analyzed before and after pretreatments. The results revealed how each organic solvent pretreatment system affected biomass structural characteristics and recalcitrance.

Meng, Xianzhi↗
DOE OSTI2024

Sparse-Stochastic Fragmented Exchange for Large-Scale Hybrid Time-Dependent Density Functional Theory Calculations

Here we extend our recently developed sparse-stochastic fragmented exchange formalism for ground-state near-gap hybrid DFT to calculate absorption spectra within linear-response time-dependent generalized Kohn-Sham DFT (LR-GKS-TDDFT) for systems consisting of thousands of valence electrons within a grid-based/plane-wave representation. A mixed deterministic/fragmented-stochastic compression of the exchange kernel, here using long-range explicit exchange functionals, provides an efficient method for accurate optical spectra. Both real-time propagation as well as frequency-resolved Casida-equation-type approaches for spectra are presented, and the method is applied to large molecular dyes.

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

Solvent Processing and Ionic Liquid-Enabled Long-Range Vertical Ordering in Block Copolymer Films with Enhanced Film Stability

Rapid and reliable processing methods for forming ordered block copolymer (BCP) materials with low defect density in a thin film geometry are required for many nanotechnology applications. Vertically aligned BCP structures, in particular, have applications ranging from nanolithography for electronics and photonics to nanoporous membranes for water remediation and novel batteries for flexible electronics. However, the attainment of nearly complete vertical orientational order of the BCP ordered phase remains challenging. Solvent-based techniques, such as direct immersion annealing (DIA) and solvent vapor annealing (SVA), have immense potential for these applications of BCP films, as it allows for tuning of their thermodynamic, structural, and chain mobility driven kinetic properties. We first demonstrate that DIA, using a judicious choice of binary solvent mixtures along with a relatively hydrophobic ionic liquid (IL), induces the rapid vertical ordering in polystyrene-b-polymethylmethacrylate (PS-PMMA) block copolymer in lamellar films. The IL establishes synergy to the binary solvent mixture of toluene and heptane to 1 create a near-neutral solvent environment for attaining the vertical microstructure of the BCP. Next, we show that IL can suppress the de-wetting of the PS-PMMA films to achieve long-range order using SVA in cylindrical films for long annealing times. Both vertical and horizontal morphology is attained in these films by selecting different solvent environments. Furthermore, attaining enhanced vertical and horizontal BCP structure with long-range defect-free order by tuning solvent quality and using additives like IL can render them useful for many nanotech applications.

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

Postanaerobic Digestion Manure Fibers as a Renewable Source of Lignin-Derived Aromatic Compounds for Microbial Upgrading

Abstract Postanaerobic digestion manure fibers are an abundant solid residue that remains underutilized. The substantial lignocellulosic content of digested manure opens the possibility of using it as a renewable resource for producing valuable products. In this study, we performed compositional and nuclear magnetic resonance analyses to determine lignin content and aromatic composition of these fibers. Additionally, alkaline-based treatment and reductive catalytic fractionation were evaluated as two different processes to produce aromatic-rich streams. The liquor from the alkaline treatment was subsequently utilized for microbial upgrading to produce 2-pyrone-4,6-dicarboxylic acid (PDC). The results showed that lignin in manure fibers represents 30% of the biomass (dry weight basis), with a ∼26% abundance of β-ether-linked aromatics and ∼13% p-coumarate moieties, indicating that the amount of lignin in the postanaerobic biomass is comparable to a moderately pretreated plant biomass. The alkaline treatment released 5.6 g aromatics/kg fibers, while reductive catalytic fractionation produced 14.0 g aromatics/kg fibers. A bioreactor operated in fed-batch mode produced a yield of ∼1 mol of PDC/mol measured aromatics at a rate of 0.2 g PDC/L·h and a titer of 2.6 g PDC/L. This study demonstrates how postanaerobic digestion manure fibers could be used in a circular bioeconomy by harnessing their lignocellulosic content to extract aromatic compounds and use them for obtaining valuable chemicals via microbial upgrading.

Riascos, Brayan D. [University of Wisconsin-Madiso↗
DOE OSTI2026

PNNL INFRARED REFRACTIVE INDEX (n/k) DATASET FOR SEVEN PAH SOLIDS AT ROOM TEMPERATURE

This dataset is an open-source repository of spectral data measured at Pacific Northwest National Laboratory (PNNL). This database provides quantitative values for the complex index of refraction for seven polycyclic aromatic hydrocarbon (PAH) solids. A list of the chemicals is available in the readme file. These spectra consist of the optical constants, i.e., the real, n(ν), and imaginary, k(ν), refractive indices, over the spectral range from 7,800 to 400 cm-1 (1.28 – 25 μm). The conditions under which the individual data were acquired are described in the associated metadata files, and the user is strongly encouraged to read and understand this information to ensure the data are used appropriately for your application. Recommended Citation for Dataset Jessica M Salcido, Jeremy D. Erickson, Ashley M. Bradley, Russell G. Tonkyn, Timothy J. Johnson and Tanya L. Myers. 2026. PNNL INFRARED REFRACTIVE INDEX (n/k) DATASET FOR SEVEN PAH SOLIDS AT ROOM TEMPERATURE. [Data Set] PNNL DataHub. INSERT DOI License Information This work is marked with CC0 1.0: https://creativecommons.org/publicdomain/zero/1.0/. The authors do request that you appropriately cite the dataset when referencing or using the dataset.

Salcido, Jessica Marie Ortola↗
NASA NTRS1973

Polyimide foam for the thermal insulation and fire protection

The preparation of chemically resistant and flame retardant foams from polyfunctional aromatic carboxylic acid derivatives and organic polyisocyanates is outlined. It was found that polyimide foams of reproducible density above 1 lb./ft. and below 6 lbs./cu ft. can be obtained by employing in the reaction of least 2% by weight of siloxane-glycol copolymer as a surfactant which acts as a specific density control agent. Polyimide foams into which reinforcing fibers such as silicon dioxide and carbon fibers may be incorporated were also produced.

Rosser, R. W.↗
NASA NTRS1982

Symposium (International) on Combustion, 19th, Technion Israel Institute of Technology, Haifa, Israel, August 8-13, 1982, Proceedings

Topics discussed are related to elementary reactions, reaction mechanisms and modeling, laminar flames, flame chemistry, turbulent reacting shear flows, turbulent premixed flames, turbulent combustion measurements, continuous combustors, detonation, detonation and explosion, heterogeneous detonation, propellant combustion, fire-ignition and thermal degradation, fire-flame spread and burning, fire-modeling, spray combustion, and droplet combustion. Coal combustion kinetics and mechanisms are considered along with coal combustion mechanisms and pyrolysis, coal combustion techniques, NOx in coal combustion, gaseous pollutants, soot and PAH, soot and inorganic pollutants, I.C. engine combustion, and ignition and extinction. Attention is given to intricate paths and simple steps in chemical kinetics and combustion, the formation of polycyclic aromatic hydrocarbons by combustion, turbulent flame structure and speed in spark ignition engines, and unresolved problems in SOx, NOx, and soot control in combustion.

Source record↗
NASA NTRS1996

Chemistry by Way of Density Functional Theory

In this work we demonstrate that density functional theory (DFT) methods make an important contribution to understanding chemical systems and are an important additional method for the computational chemist. We report calibration calculations obtained with different functionals for the 55 G2 molecules to justify our selection of the B3LYP functional. We show that accurate geometries and vibrational frequencies obtained at the B3LYP level can be combined with traditional methods to simplify the calculation of accurate heats of formation. We illustrate the application of the B3LYP approach to a variety of chemical problems from the vibrational frequencies of polycyclic aromatic hydrocarbons to transition metal systems. We show that the B3LYP method typically performs better than the MP2 method at a significantly lower computational cost. Thus the B3LYP method allows us to extend our studies to much larger systems while maintaining a high degree of accuracy. We show that for transition metal systems, the B3LYP bond energies are typically of sufficient accuracy that they can be used to explain experimental trends and even differentiate between different experimental values. We show that for boron clusters the B3LYP energetics are not as good as for many of the other systems presented, but even in this case the B3LYP approach is able to help understand the experimental trends.

Bauschlicher, Charles W., Jr.↗
NASA NTRS2010

Tidal Marsh Outwelling of Dissolved Organic Matter and Resulting Temporal Variability in Coastal Water Optical and Biogeochemical Properties

Coastal wetlands are highly dynamic environments at the land-ocean interface where human activities, short-term physical forcings and intense episodic events result in high biological and chemical variability. Long being recognized as among the most productive ecosystems in the world, tidally-influenced coastal marshes are hot spots of biogeochemical transformation and exchange. High temporal resolution observations that we performed in several marsh-estuarine systems of the Chesapeake Bay revealed significant variability in water optical and biogeochemical characteristics at hourly time scales, associated with tidally-driven hydrology. Water in the tidal creek draining each marsh was sampled every hour during several semi-diurnal tidal cycles using ISCO automated samplers. Measurements showed that water leaving the marsh during ebbing tide was consistently enriched in dissolved organic carbon (DOC), frequently by more than a factor of two, compared to water entering the marsh during flooding tide. Estimates of DOC fluxes showed a net DOC export from the marsh to the estuary during seasons of both low and high biomass of marsh vegetation. Chlorophyll amounts were typically lower in the water draining the marsh, compared to that entering the marsh during flooding tide, suggesting that marshes act as transformers of particulate to dissolved organic matter. Moreover, detailed optical and compositional analyses demonstrated that marshes are important sources of optically and chemically distinctive, relatively complex, high molecular weight, aromatic-rich and highly colored dissolved organic compounds. Compared to adjacent estuarine waters, marsh-exported colored dissolved organic matter (CDOM) was characterized by considerably stronger absorption (more than a factor of three in some cases), larger DOC-specific absorption, lower exponential spectral slope, larger fluorescence signal, lower fluorescence per unit absorbance, and higher fluorescence at visible wavelengths. Observed patterns in water optical and biogeochemical variables were very consistent among different marsh systems and throughout the year, despite continued tidal exchange, implying rapid transformation of marsh DOM in the estuary through both photochemical and microbial processes. These findings illustrate the importance of tidal marsh ecosystems as sources, sinks and/or transformers of biologically important nutrients, carbon and colored dissolved organic compounds, and their influence on short-term biological, optical and biogeochemical variability in coastal waters.

Tzortziou, Maria↗
DOE OSTI2021

Fuel properties effects on wall-wetting and fuel-in-lube dilution under stochastic pre ignition prone conditions

Fuel-engine interactions have been shown to influence stochastic pre-ignition (SPI), however there is uncertainty on the root causes, participially if effects are primarily physical or chemical in nature. To better delineate the physical and chemical dependencies of fuel properties on SPI, this work studies interactions between aromatics, distillation, and particle matter index on SPI with a laser induced fluorescence (LIF) diagnostic to observe wall wetting. Fuels with high aromatic components or higher distillation temperatures tend to increase SPI events, but it is not well understood if the increased fuel dilution or a chemical aspect of this process is the primary mechanism for SPI. By employing the novel LIF in this work we measure fuel dilution in real-time in a running single cylinder research engine operated at SPI conditions. Three fuels were used in the present work, with the LIF diagnostic. Each fuel was operated at two injection timings, generating fuel specific effects on wall wetting. The LIF measurements are coupled with engine combustion measurements and SPI event counts. Results enable a deconvolution of fuel physical and chemical properties on SPI propensity, providing unique and novel insights into the dominant fuel effects affecting SPI.

Splitter, Derek↗
DOE OSTI2020

An integrated methane dehydroaromatization and chemical looping process

Most of the natural gas co-produced in oil wells is flared due to the high transportation costs of bringing it to market. Onsite upgrading of natural gas to liquid products could address this issue but there are few processes for effective direct conversion of natural gas to liquid products. Methane dehydroaromatization (DHA) over Mo/HZSM- 5 offers a potential route to a value-added liquid product, however, DHA conversion is severely limited by thermodynamics at most industrially relevant temperatures. Here we propose an integrated process coupling methane DHA, chemical looping for selective hydrogen oxidation, and subsequent water removal to achieve higher yields of aromatic products limited by the thermodynamics in one-pass systems. Here, we validate this process via the construction and operation of a one-of-a-kind multibed recirculating reactor, and achieve a combined aromatics yield of 42%. Detailed technoeconomic analysis of the process for mobile applications show that such a process could be economically viable under certain circumstances.

03 NATURAL GAS↗
DOE OSTI2020

Water-polyamide chemical interplay in desalination membranes explored by ambient pressure X-ray photoelectron spectroscopy

Reverse osmosis using aromatic polyamide membranes is currently the most important technology for seawater desalination. The performance of reverse osmosis membranes is highly dependent on the interplay of their surface chemical groups with water and water contaminants. In order to better understand the underlying mechanisms of these membranes, we study ultrathin polyamide films that chemically resemble reverse osmosis membranes, using ambient pressure X-ray photoelectron spectroscopy. This technique can identify the functional groups at the membrane–water interface and allows monitoring of small shifts in the electron binding energy that indicate interaction with water. We observe deprotonation of free acid groups and formation of a ‘water complex’ with nitrogen groups in the polymer upon exposure of the membrane to water vapour. The chemical changes are reversed when water is removed from the membrane. While the correlation between functional groups and water uptake is an established one, this experiment serves to understand the nature of their chemical interaction, and opens up possibilities for tailoring future materials to specific requirements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

From Petroleum to Biobased Crude: A Thermoplastic Polyurethane from Lignin-Oil Without Isocyanates

The movement to transfer from petroleum-based products and materials to renewables does not necessarily have to bypass the use of oil. A new type of "black-gold" is readily abundant from the earth's most abundant source of aromatic carbon: lignin. While fractionation of petroleum yields fuels and chemicals for a diverse set of industries, lignin fractionation using targeted catalysts has demonstrated the ability to generate monomers and oligomers rich in functional groups for polymer synthesis. This study explores the use of lignin-oil, generated from reductive catalytic fractionation of popular wood, to a hydroxyl-rich mixture of aromatics that is used to synthesize a thermoplastic non-isocyanate polyurethane. The lignin-oil is first converted to a cyclocarbonated derivative using a benign synthetic sequence and further polymerized with a diamine to yield the non-isocyanate TPU. While more work is underway to optimize the reaction conditions and meet typical mechanical properties of commercial materials, initial analysis shows thermoplastic behavior and flexible properties consistent with traditional thermoplastic polyurethanes.

BIOMASS FUELS↗
NASA NTRS2006

Vibrational Spectroscopy after OSU - From C2- to Interstellar Polycyclic Aromatic Hydrocarbons

The composition of interstellar ice and dust provides insight into the chemical history of the interstellar medium and early solar system. It is now possible to probe this unique and unusual chemistry and determine the composition of these microscopic interstellar particles which are hundreds to many thousands of light years away thanks to substantial progress in two areas: astronomical spectroscopic techniques in the middle-infrared, the spectral region most diagnostic of chemical composition, and laboratory simulations which realistically reproduce the critical conditions in various interstellar environments. High quality infrared spectra of many different astronomical sources, some associated with giant, dark molecular clouds -the birthplace of stars and planets- and others in more tenuous, UV radiation rich regions are now available. The fundamentals of IR spectroscopy and what comparisons of astronomical IR spectra with laboratory spectra of materials prepared under realistic simulated interstellar conditions tell us about the components of these materials is the subject of this talk. These observations have shown that mixed molecular ices comprised of H2O, CH3OH, CO, NH3 and H2CO contain most of the molecular material in molecular clouds and that gas phase, ionized polycyclic aromatic hydrocarbons (PAHs) are widespread and surprisingly abundant throughout most of the interstellar medium.

Allamandola, Louis J.↗
NASA NTRS2012

Fluorescent aromatic sensors and their methods of use

Aromatic molecules that can be used as sensors are described. The aromatic sensors include a polycyclic aromatic hydrocarbon core with a five-membered imide rings fused to the core and at least two pendant aryl groups. The aromatic sensor molecules can detect target analytes or molecular strain as a result of changes in their fluorescence, in many cases with on-off behavior. Aromatic molecules that fluoresce at various frequencies can be prepared by altering the structure of the aromatic core or the substituents attached to it. The aromatic molecules can be used as sensors for various applications such as, for example, the detection of dangerous chemicals, biomedical diagnosis, and the detection of damage or strain in composite materials. Methods of preparing aromatic sensor molecules are also described.

Meador, Michael A.↗