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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Electrochemical Routes for the Valorization of Biomass-Derived Feedstocks: From Chemistry to Application

The drive to reduce consumption of fossil resources, coupled with expanding capacity for renewable electricity, invites the exploration of new routes to utilize this energy for the sustainable production of fuels, chemicals, and materials. Biomass represents a possible source of platform precursors for such commodities due to its inherent ability to fix CO2 in the form of multi-carbon organic molecules. Electrochemical methods for the valorization of biomass are thus intriguing, but there is a need to objectively evaluate this field and define the opportunity space by identifying pathways suited to electrochemistry. In this contribution we offer a comprehensive, critical review of recent advances in low-temperature (liquid phase), electrochemical reduction and oxidation of biomass-derived intermediates (polyols, furans, carboxylic acids, amino acids, and lignin), with emphasis on identifying the state-of-the-art for each documented reaction. Progress in computational modeling is also reviewed. We further suggest a number of possible reactions that have not yet been explored but which are expected to proceed based on established routes to transform specific functional groups. We conclude with a critical discussion of technological challenges for scale-up, fundamental research needs, process intensification opportunities (e.g., by pairing compatible oxidations and reductions), and new benchmarking standards that will be necessary to accelerate progress toward application in this still-nascent field.

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

Evaluating the Case for Reduced Precious Metal Catalysts in Proton Exchange Membrane Electrolyzers

Proton exchange membrane (PEM) water electrolyzers are a key technology in decarbonizing hydrogen production. Though the market for PEM electrolyzer systems is growing, there are concerns that the cost and availability of precious metal catalysts utilized in today’s commercial systems can limit deployment. Herein, we show that while the availability of Ir should not impede deployment in the near term, the inelasticity of the Ir commodity price is cause for immediate concern. Here we emphasize that diversifying catalyst materials, even with other precious metals, can reduce system costs and mitigate supply chain risk. Furthermore, we analyze the trade-offs between catalyst capital cost and catalyst activity for a range of operating conditions (i.e., capacity factor, electricity price). The framework presented herein is a first step toward establishing performance targets (i.e., activity, stability, material cost) for reduced precious metal and non-precious metal catalysts as a function of PEM electrolyzer operating conditions.

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

Mine Water Use, Treatment, and Reuse in the United States: A Look at Current Industry Practices and Select Case Studies

Mining provides significant economic value while often impacting local water supplies and environments because of freshwater usage and waste disposal practices. In this paper we identify current practices in mine water, including how water is used in mining, influent and effluent water quality, treatment technologies, and end uses with the goal of informing future research on implementable, reliable, and cost-effective advanced water treatment in the mining sector. This study also reviews the available literature to broadly evaluate mining in the United States and performs a techno-economic assessment on water use and disposal for three detailed case studies applicable to lithium, uranium, and copper mines. These case studies highlight specific industry examples of distinct extraction methods, geographical regions, and mined commodities. Hypothetical scenarios based on case study baselines revealed potential impacts to mine water available for beneficial reuse through the use of novel water treatment technologies and alternate water management strategies. Finally, an assessment of national level impacts resulting from the reuse of treated mine source water is presented.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2019

Polyethylene Grafted Silica Nanoparticles Prepared via Surface-Initiated ROMP

Polyethylene and nanosilica represent the most ubiquitous commodity plastic and nanocomposite filler, respectively. Despite their possible utility, few examples exist in the literature of successfully combining these two materials to form polyethylene nanocomposites. Synthesizing well-defined polyethylene grafted to a surface is a significant challenge in the nanocomposites community. Presented in this paper is a synthetic approach toward polyethylene grafted nanoparticles with controllable graft density and molecular weight of the grafted polymer. The variably grafted nanoparticles were then incorporated into a commercial high density polyethylene matrix. The synthesis, characterization, and challenges in making these materials are further discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Technoeconomic Analysis of a Novel Microwave Process to Produce Ethylene from Methane

Ethylene is a critical feedstock in industrial processes, serving as a raw material in the petrochemical industry to produce plastics and commodity chemicals. Conventional ethylene production routes are energy-intensive and contribute substantially to the carbon footprint of chemical manufacturing. In this study, an industrial-scale novel microwave process was simulated using ASPEN Plus to assess its economic viability. Technoeconomic analysis confirmed the economic competitiveness of the novel microwave process, with a levelized cost of ethylene of USD 0.51/kg compared to USD 0.56/kg for the conventional base case. Key economic drivers of the process were identified, and sensitivity analyses were conducted to evaluate their impact on project economics. Furthermore, 87.7% of the total utility consumption in the novel microwave process is electricity, highlighting its potential to contribute to the electrification of the chemical industry. The findings of this study confirm the economic feasibility of both industrial-scale microwave reactors and modular plant configurations for the production of ethylene from methane, offering a promising alternative to conventional processes.

electromagnetic radiation↗
DOE OSTI2020

Coupling and Reactions of Lignols and New Lignin Monomers: A Density Functional Theory Study

This perspective summarizes and compares computational results for the thermodynamics of bond dissociation, coupling, and rearomatization for a number of noncanonical lignin monomer–lignol combinations that have been found to occur experimentally. The noncanonical lignin monomers discussed are tricin, caffeyl alcohol, 5-hydroxyconiferyl alcohol, and piceatannol. Among dimeric combinations, the results for bond dissociation are generally similar, but in cases for which trimers have been reported (tricin-lignol adducts), this value can be quite variable, with stereochemical and structural preferences. Among the adducts examined thus far, the energies associated with quinone methide formation and rearomatization are not dissimilar and would not impede subsequent polymerization. These fundamental studies may help to elucidate how lignin monomers are incorporated into the lignin polymer, provide leads for targeted genetic modification, and be of use in deconstruction for the production of commodity chemicals.

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

Synthesis of Carbohydrates from Methanol Using Electrochemical Partial Oxidation over Palladium with the Integrated Formose Reaction

Electrochemically derived multicarbon products are a golden target for valorization of captured carbon dioxide due to the potential of turning a waste product into useful commodity chemicals with renewable energy sources. As a tantalizing approach toward their synthesis, the formose reaction utilizes catalytic condensation of formaldehyde to generate carbohydrates. Furthermore, while a sustainable approach to artificial carbohydrate production through electrochemical generation of formaldehyde is desirable, to date, it has not been fully realized. Here, we study the electrocatalytic conversion of methanol to formaldehyde on palladium with faradaic efficiency of over 90% at 0.9 V vs Ag/AgCl and with the partial current density of nearly 3 mA cm -2 at 1.6 V vs Ag/AgCl. We observe the concurrent generation of palladium oxides as a consequence of the high overpotentials employed, which may partially explain the higher selectivity toward the partial oxidation product. Moreover, we demonstrate that formaldehyde produced electrochemically from methanol is feasible for formose reactions without the need for further purification, achieving 21-28% carbon conversion to carbohydrates. This process, therefore, represents a potential avenue for the electrochemical generation of formaldehyde and its utilization in generating multicarbon products inaccessible by other electrocatalytic means.

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

Chemical Recycling of Polybutadiene Rubber with Tailored Depolymerization Enabled by Microencapsulated Metathesis Catalysts

The effective management of plastic waste streams to prevent plastic land and water pollution is a growing problem that is also one of the most important challenges in polymer science today. Polymer materials that are stable over their lifetime and can also be cheaply recycled or repurposed as desired could more easily be diverted from waste streams. However, this is difficult for most commodity plastics. It is especially difficult to conceive this with intractable, cross-linked polymers such as rubbers. In this work, we explore the utility of microencapsulated Grubbs’ catalysts for the in-situ depolymerization and reprocessing of polybutadiene (PB) rubber. Second-generation Hoveyda-Grubbs catalyst (HG2) contained within glassy thermoplastic microspheres can be dispersed in PB rubber below the microsphere’s glass transition temperature (T g ) without adverse depolymerization, evidenced by rubber with and without these microspheres obtaining similar shear storage moduli of ≈16 and ≈28 kPa, respectively. The thermoplastic’s T g can be used to tune the depolymerization temperature, via release of HG2 into the rubber matrix. For example, using poly(lactic acid) (PLA) vs polysulfone results in an 85 and 162 °C depolymerization temperature, respectively. Liquefaction of rubber to a mixture of small molecules and oligomers is demonstrated using a 0.01 mol % catalyst loading using PLA as the encapsulant. Furthermore, at that same catalyst loading, depolymerization occurs to a greater extent in comparison to two ex-situ approaches, including a conventional solvent-assisted method, where it occurs at roughly twice the extent at each given catalyst loading. In addition, depolymerization of the microsphere-loaded rubbers was demonstrated for samples stored under nitrogen for 23 days. Lastly, we show that the depolymerized products can be reprocessed back into solid rubber with a shear storage modulus of ≈32 kPa. Thus, we envision that this approach could be used to recycle and reuse cross-linked rubbers at the end of their product lifetime.

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

Computational Design of Metal-Exchanged MFI Zeolites for Coupling CO 2 –Ethylene to Form Acrylic Acid

The production of acrylic acid by coupling CO 2 and ethylene is highly desirable, as it uses a C 1 molecule to introduce the carboxylic group into a large commodity chemical, forming an unsaturated carboxylic acid. Molecular complexes have been used as catalysts in the literature for this reaction; however, these homogeneous studies were all limited by low activity and stability, and efficient heterogeneous catalysts remain to be explored. Here, we report density functional theory calculations, through which we investigated metal-exchanged MFI zeolites with metals from 3d, 4d, and 5d series for this reaction. Screening of reaction thermodynamics has shown that Sc, Y, Cr, Mo, W, Mn, Tc, and Re dispersed into MFI zeolites are potential catalysts. We further calculated the activation barriers for the β–H transfer, a key elementary step that normally determines the overall rates, and found the lowest barrier over Sc- and Y-MFI; such a feasible kinetics is attributed to the low electronegativity of Sc and Y that strongly affects the nature of the transition states and the charge redistribution during the β–H transfer. In conclusion, this work thus provides guidelines for designing a zeolite-based catalyst for this valuable reaction and identifies promising metal centers to be used.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Electrochemical Conversion of Biologically Produced Muconic Acid: Key Considerations for Scale-Up and Corresponding Technoeconomic Analysis

We present muconic acid, an unsaturated diacid that can be produced from cellulosic sugars and lignin monomers by fermentation, emerges as a promising intermediate for the sustainable manufacture of commodity polyamides and polyesters including Nylon-6,6 and polyethylene terephthalate (PET). Current conversion schemes consist in the biological production of cis,cis-muconic acid using metabolically engineered yeasts and bacteria, and the subsequent diversification to adipic acid, terephthalic acid, and their derivatives using chemical catalysts. In some instances, conventional precious metal catalysts can be advantageously replaced by base metal electrocatalysts. Here, we show the economic relevance of utilizing a hybrid biological–electrochemical conversion scheme to convert glucose to trans-3-hexenedioic acid (t3HDA), a monomer used for the synthesis of bioadvantaged Nylon-6,6. Potential roadblocks to biological and electrochemical integration in a single reactor, including electrocatalyst deactivation due to biogenic impurities and low faradaic efficiency inherent to side reactions in complex media, have been studied and addressed. In this study, t3HDA was produced with 94% yield and 100% faradaic efficiency. With consideration of the high t3HDA yield and faradaic efficiency, a technoeconomic analysis was developed on the basis of the current yield and titer achieved for muconic acid, the figures of merit defined for industrial electrochemical processes, and the separation of the desired product from the medium. On the basis of this analysis, t3HDA could be produced for approximately $2.00 kg –1 . The low cost for t3HDA is a primary factor of the electrochemical route being able to cascade biological catalysis and electrocatalysis in one pot without separation of the muconic acid intermediate from the fermentation broth.

3-Hexenedioic acid↗
DOE OSTI2020

Electrolyte Engineering for Efficient Electrochemical Nitrate Reduction to Ammonia on a Titanium Electrode

Nitrates from agricultural runoff and industrial waste streams are a notorious waste product and hazardous pollutant. Traditional electrochemical water remediation approaches aim to solve this problem by converting nitrates to environmentally benign N 2 while minimizing the production of environmentally hazardous side products such as ammonia and nitrous oxide in a process known as “denitrification”. We modify this concept and outline an opportunity to optimize the conversion of nitrates into ammonia, which is also a key commodity product used as a fertilizer, potential fuel, and chemical precursor. The electrochemical conversion of nitrates to ammonia recycles the fixed nitrogen and offers an appealing and supplementary alternative to the energy- and resource-intensive Haber-Bosch process. In this study, we investigated the effect of varying electrochemical conditions (pH, nitrate concentration, and applied potential) on the selective reduction of nitrate to ammonia at a titanium cathode. We observed that high concentrations of both protons and nitrate ions are needed to achieve high selectivity, reaching a peak of 82% Faradaic efficiency to ammonia at an applied potential of -1 V versus RHE and a partial current density to NH 3 of -22 mA/cm 2 , using 0.4 M [NO 3 – ] at pH ~0.77. The Ti electrode, as a poor hydrogen evolution catalyst with notable corrosion resistance, provides a large window of operating conditions to achieve high selectivity in the reduction of nitrate anions. Stability of the system was evaluated, and we found a high Faradaic efficiency throughout the course of an 8 h experiment. After electrochemical testing, titanium hydride was observed at the cathode surface. We also show a preliminary technoeconomic study, indicating that it may be feasible to employ an electrochemical strategy for the production of ammonium nitrate.

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

Monolignol Benzoates Incorporate into the Lignin of Transgenic Populus trichocarpa Depleted in C3H and C4H

Lignin, an abundant renewable aromatic biopolymer, is an essential macromolecule in terrestrial vascular plants. Genetic modifications affecting monolignol biosynthesis, which produces lignin monomers, alter the metabolic flux through the pathway and are becoming increasingly explored for improving the lignin and biomass quality and for producing high-value commodity chemical feedstocks. Benzoate (BA) conjugates are important metabolites in plants that have not been adequately characterized as components of the lignin structure. In addition to finding trace levels of BA conjugates in wild-type (WT) Populus trichocarpa, these become significantly augmented in strategic triple transgenics. Genes for three key cytochrome P450 enzymes, two 4-hydroxylases (PtrC4H1 and PtrC4H2), and one 3-hydroxylase (PtrC3H3), were downregulated to produce the transgenic plants in which monolignol benzoate (ML-BA) conjugates were incorporated into their lignin at a level some 16-fold higher than in WT. The co-downregulation of PtrC4H1/PtrC4H2/PtrC3H3 genes may cause a rerouting or modification of the pathway due to the interaction of the benzoate biosynthetic pathway with the conventional pathway for monolignol biosynthesis. The total lignin content in the transgenics was decreased by 50%, and the lignin H-unit level was elevated some 70-fold. The wood from the transgenic trees showed reduced recalcitrance toward enzymatic saccharification, which has value for the conversion of plant biomass to bioenergy.

2D NMR↗
DOE OSTI2016

Development of a Transcription Factor-Based Lactam Biosensor

Lactams are an important class of commodity chemicals used in the manufacture of nylons, with millions of tons produced every year. Biological production of lactams could be greatly improved by high-throughput sensors for lactam biosynthesis. To identify biosensors of lactams, we applied in this paper a chemoinformatic approach inspired by small molecule drug discovery. We define this approach as analogue generation toward catabolizable chemicals or AGTC. We discovered a lactam biosensor based on the ChnR/Pb transcription factor-promoter pair. The microbial biosensor is capable of sensing ε-caprolactam, δ-valerolactam, and butyrolactam in a dose-dependent manner. Finally, the biosensor has sufficient specificity to discriminate against lactam biosynthetic intermediates and therefore could potentially be applied for high-throughput metabolic engineering for industrially important high titer lactam biosynthesis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Application of an Acyl-CoA Ligase from Streptomyces aizunensis for Lactam Biosynthesis

ε-Caprolactam and δ-valerolactam are important commodity chemicals used in the manufacture of nylons, with millions of tons produced annually. Biological production of these highly valued chemicals has been limited due to a lack of enzymes that cyclize ω-amino fatty acid precursors to corresponding lactams under ambient conditions. In this study, we demonstrated production of these chemicals using ORF26, an acyl-CoA ligase involved in the biosynthesis of ECO-02301 in Streptomyces aizunensis. This enzyme has a broad substrate spectrum and can cyclize 4-aminobutyric acid into γ-butyrolactam, 5-aminovaleric acid into δ-valerolactam and 6-aminocaproic acid into ε-caprolactam. Recombinant E. coli expressing ORF26 produced valerolactam and caprolactam when 5-aminovaleric acid and 6-aminocaproic acid were added to the culture medium. Upon coexpressing ORF26 with a metabolic pathway that produced 5-aminovaleric acid from lysine, we were able to demonstrate production of δ-valerolactam from lysine.

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

Tunable Repression of Key Photosynthetic Processes Using Cas12a CRISPR Interference in the Fast-Growing Cyanobacterium Synechococcus sp. UTEX 2973

Cyanobacteria are photoautotrophic prokaryotes that serve as key model organisms to study basic photosynthetic processes and are potential carbon-negative production chassis for commodity and high-value chemicals. The development of new synthetic biology tools and improvement of current ones is a requisite for furthering these organisms as models and production vehicles. CRISPR interference (CRISPRi) allows for targeted gene repression using a DNase-dead Cas nuclease (“dCas”). Here, we describe a titratable dCas12a (dCpf1) CRISPRi system and apply it to repress key photosynthetic processes in the fast-growing cyanobacterium Synechococcus sp. UTEX 2973 (S2973). The system relies on a lac repressor system that retains tight regulation in the absence of inducer (0–10% repression) while maintaining the capability for >90% repression of high-abundance gene targets. We determined that dCas12a is less toxic than dCas9. We tested the efficacy of the system toward eYFP and three native targets in S2973: the phycobilisome antenna, glycogen synthesis, and photosystem I (PSI), an essential part of the photosynthetic electron transport chain in oxygenic photoautotrophs. PSI was knocked down indirectly by repressing the protein factor BtpA involved in stabilizing core PSI proteins. We could reduce cellular PSI titer by 87% under photoautotrophic conditions, and we characterized these cells to gain insights into the response of the strain to the low PSI content. The ability to tightly regulate and time the (de)repression of essential genes in trans will allow for the study of photosynthetic processes that are not accessible using knockout mutants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

A Substrate-Integrated and Scalable Templated Approach Based on Rusted Steel for the Fabrication of Polypyrrole Nanotube Arrays

We report here a facile, generalizable, and entirely scalable approach for the fabrication of vertically aligned arrays of Fe{sub 2}O{sub 3}/polypyrrole core-shell nanostructures and polypyrrole nanotubes. Our 'all electrochemical' approach is based on the fabrication of {alpha}-Fe{sub 2}O{sub 3} nanowire arrays by the simple heat treatment of commodity low carbon steel substrates, followed by electropolymerization of conformal polypyrrole sheaths around the nanowires. Subsequently, electrochemical etching of the nanowires yields large-area vertically aligned polypyrrole nanotube arrays on the steel substrate. The developed methodology is generalizable to functionalized pyrrole monomers and represents a significant practical advance of relevance to the technological implementation of conjugated polymer nanostructures in electrochromics, electrochemical energy storage, and sensing.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Chemoinformatic-Guided Engineering of Polyketide Synthases

Polyketide synthase (PKS) engineering is an attractive method to generate new molecules such as commodity, fine and specialty chemicals. A significant challenge is re-engineering a partially reductive PKS module to produce a saturated β-carbon through a reductive loop (RL) exchange. In this work, we sought to establish that chemoinformatics, a field traditionally used in drug discovery, offers a viable strategy for RL exchanges. We first introduced a set of donor RLs of diverse genetic origin and chemical substrates into the first extension module of the lipomycin PKS (LipPKS1). Product titers of these engineered unimodular PKSs correlated with chemical structure similarity between the substrate of the donor RLs and recipient LipPKS1, reaching a titer of 165 mg/L of short-chain fatty acids produced by the host Streptomyces albus J1074. Finally, expanding this method to larger intermediates that require bimodular communication, we introduced RLs of divergent chemosimilarity into LipPKS2 and determined triketide lactone production. Collectively, we observed a statistically significant correlation between atom pair chemosimilarity and production, establishing a new chemoinformatic method that may aid in the engineering of PKSs to produce desired, unnatural products.

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

Chemical Recycling of Thiol Epoxy Thermosets via Light-Driven C–C Bond Cleavage

Epoxy thermosets are high-volume materials that play a central role in a wide range of engineering applications; however, technologies to recycle these polymers remain rare. Here, we present a catalytic, light-driven method that enables chemical recycling of industrially relevant thiol epoxy thermosets to their original monomer at ambient temperature. This strategy relies on the proton-coupled electron transfer (PCET) activation of hydroxy groups within the polymer network to generate key alkoxy radicals that promote the fragmentation of the polymer through C–C bond β-scission. The method fully depolymerizes insoluble thiol epoxy thermosets into well-defined mixtures of small-molecule products, which can collectively be converted into the original monomer via a one-step dealkylation process. Notably, this process is selective and efficient even in the presence of other commodity plastics and additives commonly found in commercial applications. Finally, these results constitute an important step toward making epoxy thermosets recyclable and more generally exemplify the potential of PCET to offer a more sustainable end-of-life for a diverse array of commercial plastics.

36 MATERIALS SCIENCE↗