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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Gold-catalyzed conversion of lignin to low molecular weight aromatics

A heterogeneous catalyst system, employing Au nanoparticles (NPs) and Li–Al (1:2) layered double hydroxide (LDH) as support, showed excellent activity in aerobic oxidation of the benzylic alcohol group in β-O-4 linked lignin model dimers to the corresponding carbonyl products using molecular oxygen under atmospheric pressure. The synergistic effect between Au NPs and the basic Li–Al LDH support induces further reaction of the oxidized model compounds, facilitating facile cleavage of the β-O-4 linkage. Extension to oxidation of γ-valerolactone (GVL) extracted lignin and kraft lignin using Au/Li–Al LDH under similar conditions produced a range of aromatic monomers in high yield. Hydrolysis of the Au/Li–Al LDH oxidized lignin was found to increase the degree of lignin depolymerization, with monomer yields reaching 40% for GVL extracted lignin. According to these results, the Au/Li–Al LDH + O 2 catalyst system shows potential to be an environmentally friendly means of depolymerizing lignin to low molecular weight aromatics under mild conditions.

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

How to add a five-membered ring to polycyclic aromatic hydrocarbons (PAHs) – molecular mass growth of the 2-naphthyl radical (C 10 H 7 ) to benzindenes (C 13 H 10 ) as a case study

The three-ring polycyclic aromatic hydrocarbons (PAHs) 3 H -benz[ e ]indene (C 13 H 10 ) and 1 H -benz[ f ]indene (C 13 H 10 ) along with their naphthalene-based isomers 2-(prop-2-yn-1-yl)naphthalene (C 13 H 10 ), 2-(prop-1-yn-1-yl)naphthalene (C 13 H 10 ), and 2-(propa-1,2-dien-1-yl)naphthalene (C 13 H 10 ) were formed through a “directed synthesis” via a high temperature chemical micro reactor under combustion-like conditions (1300 ± 35 K) through the reactions of the 2-naphthyl isomer (C 10 H 7 ˙) with allene (C 3 H 4 ) and methylacetylene (C 3 H 4 ). The isomer distributions were probed utilizing tunable vacuum ultraviolet radiation from the Advanced Light Source (ALS) by recording the photoionization efficiency curves at mass-to-charge of m / z = 166 (C 13 H 10 ) and 167 ( 13 CC 12 H 10 ) of the products in a supersonic molecular beam. Complemented by electronic structure calculations, our study reveals critical mass growth processes via annulation of a five-membered ring from the reaction between aryl radicals and distinct C 3 H 4 isomers at elevated temperatures as present in combustion processes and in circumstellar envelopes of carbon stars. The underlying reaction mechanisms proceed through the initial addition of the 2-naphthyl radical with its radical center to the π-electron density of the allene and methylacetylene reactants via entrance barriers between 8 and 14 kJ mol -1 , followed by isomerization (hydrogen shifts, ring closure), and termination via atomic hydrogen losses accompanied by aromatization. The reaction mechanisms reflect the formation of indene – the prototype PAH carrying a single five- and a single six-membered ring – synthesized through the reaction of the phenyl radical (C 6 H 5 ˙) with allene and methylacetylene. In conclusion, this leads us to predict that aryl radicals – upon reaction with allene/methylacetylene – may undergo molecular mass growth processes via ring annulation and de facto addition of a five-membered ring to form molecular building blocks essential to transit planar PAHs out of the plane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Quinonoid vs. aromatic structures of heteroconjugated polymers from oligomer calculations

Conjugated polymers with quinonoid ground states can display low optical band gaps. The design of novel conjugated polymers with quinonoid ground states offers insights into the relative stabilities of aromatic vs. quinonoid structures. In this work, we present parameters such as the quinonoid (Q)/aromatic (A) energy difference, the band gap, and the C–C distances between the repeat units. This study reveals eight new polymers which exist in quinonoid ground state among twenty-nine polymers of varying structural composition that were subject to analysis. We expect that copolymerizing such quinonoid ground state monomers with aromatic ground state monomers will modulate the bandgap of the resulting polymers.

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

Supramolecular assemblies of polybenzimidazole and aromatic polycarboxylic acids with superior mechanical and H 2 /CO 2 separation properties

Aromatic polycarboxylic acids complex with imidazoles, forming supramolecular assemblies. Herein, we demonstrate that polybenzimidazole (PBI) can be augmented by aromatic polycarboxylic acids, including phthalic acid (PA), trimesic acid (TMA), and pyromellitic acid (PMA), and the resulting supramolecular assemblies exhibit attractive H 2 /CO 2 separation performance for precombustion carbon capture. The acid doping decreases the free volume and gas permeability but increases H 2 /CO 2 selectivity, which can be correlated with the molar ratio of the protons to PBI repeating units in the assemblies. Increasing the temperature decreases the H 2 /CO 2 selectivity because of weakened interactions. When challenged with model gas mixtures, a supramolecular assembly based on TMA shows H 2 /CO 2 separation properties superior to state-of-the-art materials and above Robeson's upper bound. Furthermore, this study elucidates the fruitful harnessing of dynamic non-covalent bonds to design robust and highly selective membranes for industrial gas separations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Crystal engineering of heterocyclic arylene(ethynylene) oligomers through programmed aromatic stacking

Conjugated oligomers and polymers consisting of aromatic heterocycles are examples of next-generation organic electronic materials. However, control and optimization of the self-assembly of these materials in the solid-state, which is a crucial parameter for high efficiency performance, remains an unsolved challenge in materials development. In this work, we provide valuable insight into aromatic stacking interactions between fluorinated arene rings (ArF) and heterocycles with different electronic character (Het), and elaborate on the prospect of using these interactions to control the solid-state configurations of three-ring phenyleneethynylene oligomers (PEs). Oligomers possessing heterocycles typically thought of as electron-rich (ER) show blue-shifted optical spectra in the solid-state, while those incorporating heterocycles typically thought of us electron deficient (ED) show red-shifted solid-state optical spectra. Crystal structures show ArF-Het stacking interactions between the fluorinated side-chains and ER units, which twist the backbone out of planarity and prevent chromophore aggregation. Further, the interactions are absent in ED oligomers, highlighting cofacial incompatibility between ArF rings and ED units. A combination of TD-DFT computations and novel heterocycle descriptors reinforce our assignment of the oligomers as ED or ER, while exhaustive conformer analysis shows ArF-Het stacking interactions are a significant contributor to compound stability. Overall, this work describes the importance of heterocycle electronics in conformational control in the solid state, understanding of which can be a valuable asset in the development of novel optoelectronic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Biobased chemical recycling: aminolysis of PET using renewable reagents and monomers to synthesize new semi-aromatic polyamides

Chemical recycling of PET is a method of depolymerizing polymer chains to monomeric components enabling the synthesis of second-generation materials with virgin-like quality. Commercial chemical recycling techniques rely upon high pressure methanolysis to create precursors capable of synthesizing a second-generation PET resin. However, despite the circular approach of methanolysis, a product with a very short lifespan and similar value is created. The approach of the current study is to utilize aminolysis as an ambient pressure technique to create precursors for higher value materials with longer lifespans to address the current crisis in plastic waste. Semi-aromatic polyamides (SAP) are desired in this circumstance because of their high melting point and heat resistance combined with good melt-processability similar to aliphatic polyamides. In this study SAPs were synthesized using precursors recovered from the aminolysis of PET employing biobased diamines and dicarboxylic acids. While aminolysis has been explored in previous studies, this work investigated the use of biobased components from castor oil: decamethylene diamine during recycling and sebacic acid during polymerization. Polymer synthesis resulted in the formation of SAPs similar to polyphthalamides (PPA) with novel structures given the aromatic portion from terephthalic acid (TPA) and aliphatic portion from the diamines and diacids. The synthesized materials exhibited excellent thermal stability with high glass transition temperatures. Novel polymers were created with varying aliphatic chain length to understand fundamental parameters needed to produce a valuable polymer from post-consumer waste.

High performance Applications↗
DOE OSTI2014

Electronic structure and aromaticity of large-scale hexagonal graphene nanoflakes

With the help of the recently developed SIESTA-pole (Spanish Initiative for Electronic Simulations with Thousands of Atoms) - PEXSI (pole expansion and selected inversion) method [L. Lin, A. García, G. Huhs, and C. Yang, J. Phys.: Condens. Matter 26, 305503 (2014)], we perform Kohn-Sham density functional theory calculations to study the stability and electronic structure of hydrogen passivated hexagonal graphene nanoflakes (GNFs) with up to 11 700 atoms. We find the electronic properties of GNFs, including their cohesive energy, edge formation energy, highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap, edge states, and aromaticity, depend sensitively on the type of edges (armchair graphene nanoflakes (ACGNFs) and zigzag graphene nanoflakes (ZZGNFs)), size and the number of electrons. We observe that, due to the edge-induced strain effect in ACGNFs, large-scale ACGNFs’ edge formation energy decreases as their size increases. This trend does not hold for ZZGNFs due to the presence of many edge states in ZZGNFs. We find that the energy gaps E{sub g} of GNFs all decay with respect to 1/L, where L is the size of the GNF, in a linear fashion. But as their size increases, ZZGNFs exhibit more localized edge states. We believe the presence of these states makes their gap decrease more rapidly. In particular, when L is larger than 6.40 nm, we find that ZZGNFs exhibit metallic characteristics. Furthermore, we find that the aromatic structures of GNFs appear to depend only on whether the system has 4N or 4N + 2 electrons, where N is an integer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Aromatic anchor at an invariant hormone-receptor interface: Function of insulin residue B24 with application to protein design

Crystallographic studies of insulin bound to fragments of the insulin receptor have recently defined the topography of the primary hormone-receptor interface. Here, we have investigated the role of Phe B24 , an invariant aromatic anchor at this interface and site of a human mutation causing diabetes mellitus. An extensive set of B24 substitutions has been constructed and tested for effects on receptor binding. Although aromaticity has long been considered a key requirement at this position, Met B24 was found to confer essentially native affinity and bioactivity. Molecular modeling suggests that this linear side chain can serve as an alternative hydrophobic anchor at the hormone-receptor interface. These findings motivated further substitution of Phe B24 by cyclohexanylalanine (Cha), which contains a nonplanar aliphatic ring. Contrary to expectations, [Cha B24 ]insulin likewise exhibited high activity. Furthermore, its resistance to fibrillation and the rapid rate of hexamer disassembly, properties of potential therapeutic advantage, were enhanced. The crystal structure of the Cha B24 analog, determined as an R 6 zinc-stabilized hexamer at a resolution of 1.5 Å, closely resembles that of wild-type insulin. The nonplanar aliphatic ring exhibits two chair conformations with partial occupancies, each recapitulating the role of Phe B24 at the dimer interface. Together, these studies have defined structural requirements of an anchor residue within the B24-binding pocket of the insulin receptor; similar molecular principles are likely to pertain to insulin-related growth factors. Finally, our results highlight in particular the utility of nonaromatic side chains as probes of the B24 pocket and suggest that the nonstandard Cha side chain may have therapeutic utility.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Design of Transition-Metal/Zeolite Catalysts for Direct Conversion of Coal-derived CO 2 to Aromatics

This project introduces a lab-scale, stand-alone process to produce aromatics from CO 2 . Besides reducing the amount of coal-derived CO 2 emission, this process can provide new approaches to produce valuable chemicals such as benzene, toluene, and xylene (BTX). These chemicals are the starting material in various industries such as pharmaceuticals, polymers, paints, and coatings. The focus of the project is on developing a suitable reaction configuration, feed composition, and catalyst combination that leads to high aromatics selectivity and CO 2 conversions. To achieve these objectives, computational catalysis will accompany hands-on experiments to provide insights to potential transition metals or alloys that may serve as optimal active sites for different steps of the reaction mechanism, such as reduction of CO 2 and dehydration (in the case of alcohol intermediates) and oligomerization (in the case of paraffins or olefins) of intermediate hydrocarbons.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Design of Transition-Metal/Zeolite Catalysts for Direct Conversion of Coal-derived CO 2 to Aromatics

This project introduces a lab-scale, stand-alone process to produce aromatics from CO 2 . Besides reducing the amount of coal-derived CO 2 emission, this process can provide new approaches to produce valuable chemicals such as benzene, toluene, and xylene (BTX). These chemicals are the starting material in various industries such as pharmaceuticals, polymers, paints, and coatings. The focus of the project is on developing a suitable reaction configuration, feed composition, and catalyst combination that leads to high aromatics selectivity and CO 2 conversions. To achieve these objectives, computational catalysis will accompany hands-on experiments to provide insights to potential transition metals or alloys that may serve as optimal active sites for different steps of the reaction mechanism, such as reduction of CO 2 and dehydration (in the case of alcohol intermediates) and oligomerization (in the case of paraffins or olefins) of intermediate hydrocarbons.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2024

Roles of Metal Promoters (Co, Cu, K, Ni, Zn, and Cs) in Microwave-Assisted Methane Dehydroaromatization to Aromatics Over Mo-Supported HZSM-5

Microwave (MW)-assisted methane dehydroaromatization (MDHA) offers methane conversion to more value-added aromatics, thus generating revenue and mitigating the flaring emission. We previously found that Mo/HZSM-5, despite offering higher aromatic yield, experienced rapid deactivation under microwave irradiation. Adding metal promoters is one of the solutions to not only modulate the reaction/deactivation pathways, but potentially modify the heating properties of modified Mo/HZSM-5 under MW-assisted MDHA. In this study, Mo/HZSM-5 was modified with various metal promoters (Co, Cu, K, Ni, Zn, and Cs) and their catalytic performance was assessed and correlated with their physical and chemical properties upon adding metal promoters.

Mai, Duy Hien↗
DOE OSTI2025

pi-Extended Porphyrins: The Impact of Aromatic Heterocycles on the Properties of the Largely pi-Extended Structures (Final Report_UNT_SC0016766)

Largely π-extended carbon-rich materials represent fascinating yet challenging frontiers in chemistry and materials science as it offers numerous opportunities in molecular electronics. pi-Extended porphyrins possess unique set of electronic and photophysical properties and are very attractive for a wide range of applications. However, the synthesis and functionalization of pi-extended porphyrins had been very challenging. To explore and expand this intriguing research field, it is essential to develop synthetic tools to make them accessible. Funded by the Department of Energy Basic Energy Science, my laboratory addressed these synthetic challenges by developing concise and versatile methods for pi-extended porphyrins. Significant progress has been made in multiple directions, including fusing Polycyclic Aromatic Hydrocarbons (PAH), aromatic heterocycles, antiaromatic component, and cross-conjugated component to porphyrins as well as push-pull porphyrins. The availability of these methods has made it possible to rationally design and synthesize functionalized pi-extended porphyrins. Unprecedented electronic and photophysical properties have been discovered for these pi-extended porphyrins.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Calculation of monomer yields, verification of PG concentration approximation, catalyst comparison for neat aromatic RCF, SEM micrographs for postreaction pulps, yields of aqueous-phase sugar derivatives after PG-H2O RCF, reactor pressure transients, GPC comparing pre- and postreaction organic solvent composition, PG-H2O miscibility testing, GPC probing dimer/oligomer fractionation in PG-H2O mixtures for

Reductive catalytic fractionation (RCF) is an effective lignin-first biorefining method to extract lignin as a stabilized oil from lignocellulosic biomass. To realize RCF at scale, process modeling has shown that minimizing the use of exogenous organic solvents is critical. To this end, here we investigate the ability of lignin-derived monomers to act as either solvents or cosolvents for RCF. We begin by examining the influence of lignin-derived aromatic compounds (4-propylguaiacol, 4-propylphenol, and propylbenzene) on RCF monomer yields and subsequently extend our analysis to mixtures of 4-propylguaiacol and either methanol or water. We demonstrate that 4-propylguaiacol is an effective solvent for lignin extraction and depolymerization during RCF, especially when used in combination with water as a cosolvent. Cosolvent mixtures of 4-propylguaiacol and water enable up to 81% lignin extraction, monomer yields up to 25 wt %, and postreaction phase separation. However, unlike methanol, water as a cosolvent fails to inhibit aromatic ring hydrogenation when conducted over Ru/C as a catalyst, potentially leading to excess hydrogen consumption in a process utilizing this approach. Nonetheless, these results suggest a promising strategy for eliminating external organic solvents from RCF by utilizing mixtures of lignin-derived compounds and water as alternative extraction solvents.

biorefining↗
DOE OSTI2026

Evolution_and_engineering_of_pathways_for_aromatic_O-demethylation_in_Pseudomonas_putida_KT2440

Biological conversion of lignin from biomass offers a promising strategy for sustainable production of fuels and chemicals. However,aromatic compoundsderived from lignin commonly contain methoxy groups, andO-demethylation of these substrates is often a rate-limiting reaction that influences catabolic efficiency. Severalenzymefamilies catalyze aromaticO-demethylation, but they are rarely comparedin vivoto determine an optimal biocatalytic strategy. Here, two pathways for aromaticO-demethylation were compared inPseudomonas putidaKT2440. The native Rieske non-heme ironmonooxygenase(VanAB) and, separately, a heterologous tetrahydrofolate-dependentdemethylase(LigM) were constitutively expressed inP. putida, and the strains were optimized via adaptive laboratory evolution (ALE) withvanillateas a model substrate. All evolved strains displayed improved growth phenotypes, with the evolved strains harboring the native VanAB pathway exhibiting growth rates ∼1.8x faster than those harboring the heterologous LigM pathway.Enzyme kineticsandtranscriptomicsstudies investigated the contribution of selected mutations toward enhanced utilization of vanillate. The VanAB-overexpressing strains contained the most impactful mutations, including those in VanB, thereductasefor vanillateO-demethylase, PP_3494, a global regulator of vanillate catabolism, andfghA, involved in formaldehydedetoxification. These three mutations were combined into a single strain, which exhibited approximately 5x faster vanillate consumption than the wild-type strain in the first 8 h of cultivation. Overall, this study illuminates the details of vanillate catabolism in the context of two distinct enzymatic mechanisms,yielding a platform strain for efficientO-demethylation of lignin-related aromatic compounds to value-added products. This DOI contains supplementary material associated with the published manuscript.

CBI↗
NASA NTRS1975

Basicity of aromatic amines from liquid chromatographic behavior

A liquid chromatographic investigation was conducted to determine whether the adsorption of weakly basic aromatic amines on slightly acidic silica gel adsorbents could be used to study their relative basicity. Under proper conditions, a linear correlation between pKb and log of capacity factor was observed. This finding may prove useful in helping to predict the relative basicity of closely related aromatic diamines, especially new amines being synthesized for polymer synthesis.

Young, P. R.↗
NASA NTRS1975

Friction differences between aliphatic and aromatic structures in lubrication of titanium

Sliding friction experiments were conducted with a titanium (0001) single crystal surface with various adsorbed aliphatic and aromatic compounds containing the same number of carbon atoms. An Auger emission spectroscopy analysis was used to monitor the presence of the organic lubricating compounds. Results of the investigation indicate that hexane and benzene give the same friction coefficients over a range of loads. At light loads the friction decreased with an increase in the halogen atom size where the halogens chlorine, bromine, and iodine are incorporated into the benzene molecular structure. The aliphatic compounds chlorohexane and bromohexane exhibited lower friction coefficients than the aromatic structures chlorobenzene and bromobenzene.

Buckley, D. H.↗