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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The AUREX cell: a versatile operando electrochemical cell for studying catalytic materials using X-ray diffraction, total scattering and X-ray absorption spectroscopy under working conditions

Understanding the structure–property relationship in electrocatalysts under working conditions is crucial for the rational design of novel and improved catalytic materials. This paper presents the Aarhus University reactor for electrochemical studies using X-rays (AUREX) operando electrocatalytic flow cell, designed as an easy-to-use versatile setup with a minimal background contribution and a uniform flow field to limit concentration polarization and handle gas formation. The cell has been employed to measure operando total scattering, diffraction and absorption spectroscopy as well as simultaneous combinations thereof on a commercial silver electrocatalyst for proof of concept. This combination of operando techniques allows for monitoring of the short-, medium- and long-range structure under working conditions, including an applied potential, liquid electrolyte and local reaction environment. The structural transformations of the Ag electrocatalyst are monitored with non-negative matrix factorization, linear combination analysis, the Pearson correlation coefficient matrix, and refinements in both real and reciprocal space. Upon application of an oxidative potential in an Ar-saturated aqueous 0.1 M KHCO 3 /K 2 CO 3 electrolyte, the face-centered cubic (f.c.c.) Ag gradually transforms first to a trigonal Ag 2 CO 3 phase, followed by the formation of a monoclinic Ag 2 CO 3 phase. A reducing potential immediately reverts the structure to the Ag (f.c.c.) phase. Following the electrochemical-reaction-induced phase transitions is of fundamental interest and necessary for understanding and improving the stability of electrocatalysts, and the operando cell proves a versatile setup for probing this. In addition, it is demonstrated that, when studying electrochemical reactions, a high energy or short exposure time is needed to circumvent beam-induced effects.

Frank, Sara (ORCID:0000000163218363)↗
DOE OSTI2022

Catalytic resonance of ammonia synthesis by simulated dynamic ruthenium crystal strain

Ammonia affords dense storage for renewable energy as a fungible liquid fuel, provided it can be efficiently synthesized from hydrogen and nitrogen. In this work, the catalysis of ammonia synthesis was computationally explored beyond the Sabatier limit by dynamically straining a ruthenium crystal (±4%) at the resonant frequencies (10 2 to 10 5+ Hz) of N 2 surface dissociation and hydrogenation. Density functional theory calculations at different strain conditions indicated that the energies of NH x surface intermediates and transition states scale linearly, allowing the description of ammonia synthesis at a continuum of strain conditions. A microkinetic model including multiple sites and surface diffusion between step and Ru(0001) terrace sites of varying ratios for nanoparticles of differing size revealed that dynamic strain yields catalytic ammonia synthesis conversion and turnover frequency comparable to industrial reactors (400°C, 200 atm) but at lower temperature (320°C) and an order of magnitude lower pressure (20 atm).

10 SYNTHETIC FUELS↗
DOE OSTI2022

Cryo-$\mathrm{EM}$ reveals an entangled kinetic trap in the folding of a catalytic $\mathrm{RNA}$

Functional RNAs fold through complex pathways that can contain misfolded “kinetic traps.” A complete model of RNA folding requires understanding the formation of these misfolded states, but they are difficult to characterize because of their transient and potentially conformationally dynamic nature. We used cryo–electron microscopy (cryo-EM) to visualize a long-lived misfolded state in the folding pathway of the Tetrahymena thermophilagroup I intron, a paradigmatic RNA structure-function model system. The structure revealed how this state forms native-like secondary structure and tertiary contacts but contains two incorrectly crossed strands, consistent with a previous model. This incorrect topology mispositions a critical catalytic domain and cannot be resolved locally as extensive refolding is required. This work provides a structural framework for interpreting decades of biochemical and functional studies and demonstrates the power of cryo-EM for the exploration of RNA folding pathways.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Homologous acetone carboxylases select Fe(II) or Mn(II) as the catalytic cofactor

The Irving-Williams series refers to the predicted stabilities of transition metal complexes where the observed general stability for divalent first-row transition metal complexes increase across the row. Acetone carboxylases (ACs) use a coordinated divalent metal at their active site in the catalytic conversion of bicarbonate and acetone to form acetoacetate. Highly homologous ACs discriminate among different divalent metals at their active sites such that variations of the enzyme prefer Mn(II) over Fe(II), defying Irving-Williams-predicted behavior. Defining the determinants that promote metal discrimination within the first-row transition metals is of broad fundamental importance in understanding metal-mediated catalysis and metal catalyst design.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Molten Salt Assisted Low-Temperature Electro-Catalytic Graphitization of Coal Chars

A great effort has been centered around developing clean energy technologies (energy storage devices) to curtail burning fossil fuels' deleterious environmental effects. Rechargeable batteries [lithium-ion batteries (LIBs)] are among the most invested and investigated storage devices showing potential to transform fossil fuel-powered mobility to next-generation safe electromobility. However, LIBs powered electric vehicles (EV) are expensive due to the high-cost graphite anode associated with LIBs. Herein, the synthesis of low-cost, highly crystalline nano-graphite with a tunable microstructural architecture has been demonstrated via molten salt assisted low-temperature electro-catalytic graphitization of coal chars, traditionally non-graphitizable carbon. Thus, graphite derived from coal chars exhibited nanoflake architecture and delivered high reversible capacity, stable long cycle life, and excellent electrochemical performance under fast charging/discharging conditions (5C, ~12 min charge/discharge time). This finding paves the way to manufacture cost-effective high-energy-density batteries using as-synthesized graphite from readily available coal sources that could propel the EVs to the next level.

25 ENERGY STORAGE↗
DOE OSTI2020

Highly Catalytically Active High-spin Single-atom Iron Catalyst Supported by Catechol-containing Microporous 2D Polymer

Traditionally, Fe-SACs are prepared through energy-intense processes, which often lead to the loss of precision in structural features from the starting substrates and impeding rational design. In this work, we have described the synthesis of a unique catechol-containing porous polymer with designed features in the substrates maintained, affording atomically dispersed iron catalyst (Fe-SAC) through treatment of ferrous chloride (FeCl 2 ). An aberration-corrected scanning transmission electron microscope (AC-STEM) and synchrotron X-ray absorption spectroscopy (XAS) were employed to shed light on the local coordination geometry of the atomically dispersed iron catalyst. The resulting Fe-SAC exhibits excellent catalytic performance in reduction of nitroaromatics with highest molar K app among all Fe based catalysts.

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

Catalytic Hydroprocessing of Single-Cell Oils to Hydrocarbon Fuels : Converting microbial lipids to fuels is a promising approach to replace fossil fuels

Microbial lipids hold great promise as biofuel precursors, and research efforts to convert such lipids to renewable diesel fuels have been increasing in recent years. In contrast to the numerous literature reviews on growing, characterising and extracting lipids from oleaginous microbes, and on converting vegetable oils to hydrocarbon fuels, this review aims to provide insight into aspects that are specific to hydroprocessing microbial lipids. While standard hydrotreating catalysts generally perform well with terrestrial oils, differences in lipid speciation and the presence of co-extracted compounds, such as chlorophyll and sterols, introduce additional complexities into the process for microbial lipids. Lipid cleanup steps can be introduced to produce suitable feedstocks for catalytic upgrading.

09 BIOMASS FUELS↗
DOE OSTI2021

Catalytic Reduction of Residual Oxygen for the Purification of Carbon Dioxide Streams from Pressurized Oxy-Combustors

Pressurized oxy-combustion (OC) is regarded as an energy-efficient alternative to atmospheric OC. To utilize the captured carbon dioxide (CO2) from pressurized OC for enhanced oil recovery or carbon storage in geological formations, the CO2 product stream must meet the required purity specifications. One major impurity in OC flue gases is residual O2 (e.g., 3 vol%). In this study, a catalytic approach has been investigated to remove the residual O2 through a reduction reaction with injected methane (CH4) in a reverse-flow fixed-bed (RFFB) reactor. The performance was tested for a supported copper (Cu)-based catalyst synthesized by incipient wetness impregnation and a cobalt-manganese (CoMn) oxide catalyst synthesized by a coprecipitation method. A commercial Cu-based catalyst was also studied as the reference. Experimental results revealed that under the reverse-flow operation, the temperature profiles in the reactor were symmetrical on both sides of the catalyst zone and were more homogenous than those under the conventional one-direction-flow operation. Among the tested catalysts, the CoMn catalyst was the most reactive for promoting the reduction of O2 with CH4, able to attain >95% O2 removal at 475 °C and a gas hourly space velocity (GHSV) of 18,000 h-1 with a feed gas containing 3 vol% O2. Under all experiments, the concentrations of carbon monoxide (CO) were lower than 30 ppmv in the effluent gas streams. The reaction between O2 and CH4 could be depicted by using the Mars–van Krevelen redox mechanism based on a two-step reduction–oxidation reaction pathway.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Probing catalytic activity in defect sites in transition metal oxides and sulfides using cluster models: A combined experimental and theoretical approach

Our research program has combined experimental and computational methods to study a range of cluster models for heterogeneous catalytic materials. The focus of our studies has been transition metal oxide and sulfide clusters in non-traditional oxidation states, and their chemical and physical interactions with water, to model steps in the electrocatalytic or photocatalytic hydrogen evolution reaction (HER). In the closing year of this project, we have also begun to explore addition systems in preparation for future grant proposals.

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

Supply Chain Sustainability Analysis of Renewable Hydrocarbon Fuels via Indirect Liquefaction, Ex Situ Catalytic Fast Pyrolysis, Hydrothermal Liquefaction, Combined Algal Processing, and Biochemical Conversion: Update of the 2019 State-of-Technology Cases

This technical report describes the supply chain sustainability analysis (SCSAs) for the production of renewable hydrocarbon transportation fuels via a range of conversion technologies: (1) renewable high octane gasoline (HOG) via indirect liquefaction (IDL) of woody lignocellulosic biomass (note that the IDL pathway in this SCSA represents the syngas conversion design in the 2019 SOT); (2) renewable gasoline (RG) and diesel (RD) blendstocks via ex situ catalytic fast pyrolysis of woody lignocellulosic biomass; (3) RD via hydrothermal liquefaction (HTL) of wet sludge from a wastewater treatment plant; (4) renewable hydrocarbon fuels via biochemical conversion of herbaceous lignocellulosic biomass; (5) renewable diesel via HTL of a blend of algae and woody biomass; and (6) renewable diesel via combined algae processing (CAP). This technical report focuses on the environmental performance of these six biofuel production pathways in their 2019 SOT cases. The results of these renewable hydrocarbon fuel pathways in these SCSA analyses update those for the respective 2018 SOT cases. They also provide an opportunity to examine the impact of technology improvements in both biomass feedstock production and biofuel production that have been achieved in 2019 SOTs on the sustainability performance of these renewable transportation fuels, and they reflect updates to Argonne National Laboratory’s Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET®) model, which was released in October 2019. These GREET updates include the production of natural gas, electricity, and petroleum-based fuels that can influence biofuels’ supply chain greenhouse gas (GHG) (CO₂, CH₄, and N₂O) emissions, water consumption, and air pollutant emissions. GHG emissions, water consumption, and nitrogen oxides (NO x ) emissions are the main sustainability metrics assessed in this analysis. In this analysis, we define water consumption as the amount of water withdrawn from a freshwater source that is not returned (or returnable) to a freshwater source at the same level of quality. Life-cycle fossil energy consumption and net energy balance, which is the life-cycle fossil energy consumption deducted from the renewable biofuel energy produced, are also assessed.

09 BIOMASS FUELS↗
DOE OSTI2021

Supply Chain Sustainability Analysis of Renewable Hydrocarbon Fuels via Indirect Liquefaction, Ex Situ Catalytic Fast Pyrolysis, Hydrothermal Liquefaction, Combined Algal Processing, and Biochemical Conversion: Update of the 2020 State-of-Technology Cases

This technical report describes the SCSAs for the production of renewable hydrocarbon transportation fuels via a range of conversion technologies in the 2020 SOTs: (1) renewable high octane gasoline (HOG) via indirect liquefaction (IDL) of woody lignocellulosic biomass (note that the IDL pathway in this SCSA represents the syngas conversion design); (2) renewable gasoline (RG) and diesel (RD) blendstocks via ex situ catalytic fast pyrolysis of woody lignocellulosic biomass; (3) RD via hydrothermal liquefaction (HTL) of wet sludge from a wastewater treatment plant; (4) renewable hydrocarbon fuels via biochemical conversion of herbaceous lignocellulosic biomass; (5) renewable diesel via HTL of a blend of algae and woody biomass; and (6) renewable diesel via combined algae processing (CAP). This technical report focuses on the environmental performance of these six biofuel production pathways in their 2020 SOT cases. The results of these renewable hydrocarbon fuel pathways in these SCSA analyses update those for the respective 2019 SOT cases. They also provide an opportunity to examine the impact of technology improvements in both biomass feedstock production and biofuel production that have been achieved in 2020 SOTs on the sustainability performance of these renewable transportation fuels. The SCSA results also reflect updates to Argonne National Laboratory’s Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET ® ) model, which was released in October 2020. These GREET updates include the production of natural gas, electricity, and petroleum-based fuels that can influence biofuels’ supply chain greenhouse gas (GHG) (CO 2 , CH 4 , and N 2 O) emissions, water consumption, and air pollutant emissions. GHG emissions, water consumption, and nitrogen oxides (NO x ) emissions are the main sustainability metrics assessed in this analysis. In this analysis, we define water consumption as the amount of water withdrawn from a freshwater source that is not returned (or returnable) to a freshwater source at the same level of quality. Life-cycle fossil energy consumption and net energy balance, which is the life-cycle fossil energy consumption deducted from the renewable biofuel energy produced, are also assessed.

09 BIOMASS FUELS↗
DOE OSTI2021

Supply Chain Sustainability Analysis of Renewable Hydrocarbon Fuels via Indirect Liquefaction, Ex Situ Catalytic Fast Pyrolysis, Hydrothermal Liquefaction, Combined Algal Processing, and Biochemical Conversion: Update of the 2020 State-of-Technology Cases

The Department of Energy’s (DOE) Bioenergy Technologies Office (BETO) aims to develop and deploy technologies to transform renewable biomass resources into commercially viable, high-performance biofuels, bioproducts, and biopower through public and private partnerships (U.S. Department of Energy, 2016). BETO and its national laboratory teams conduct in-depth techno-economic assessments (TEA) of biomass feedstock supply and logistics and conversion technologies to produce biofuels. There are two general types of TEAs: A design case outlines a target case (future projection) for a particular biofuel pathway. It enables identification of data gaps and research and development needs and provides goals and benchmarks against which technology progress is assessed. A state of technology (SOT) analysis assesses progress within and across relevant technology areas based on actual results at current experimental scales relative to technical targets and cost goals from design cases, and includes technical, economic, and environmental criteria as available. In addition to developing a TEA for a pathway of interest, BETO also performs a supply chain sustainability analysis (SCSA). The SCSA takes the life-cycle analysis approach that BETO has been supporting for about 20 years. It enables BETO to identify energy consumption, environmental, and sustainability issues that may be associated with biofuel production. Approaches to mitigate these issues can then be developed. Additionally, the SCSA allows for comparison of energy and environmental impacts across biofuel pathways in BETO’s research and development portfolio. This technical report describes the SCSAs for the production of renewable hydrocarbon transportation fuels via a range of conversion technologies in the 2020 SOTs: (1) renewable high octane gasoline (HOG) via indirect liquefaction (IDL) of woody lignocellulosic biomass (note that the IDL pathway in this SCSA represents the syngas conversion design [Harris et al. 2021]); (2) renewable gasoline (RG) and diesel (RD) blendstocks via ex situ catalytic fast pyrolysis of woody lignocellulosic biomass [Abhijit et al. 2021]; (3) RD via hydrothermal liquefaction (HTL) of wet sludge from a wastewater treatment plant; (4) renewable hydrocarbon fuels via biochemical conversion of herbaceous lignocellulosic biomass (Davis et al. 2021; Lin et al. 2021); (5) renewable diesel via HTL of a blend of algae (Davis and Klein, 2021) and woody biomass (Hartley et al. 2020); and (6) renewable diesel via combined algae processing (CAP) (Wiatrowski and Davis, 2021). This technical report focuses on the environmental performance of these six biofuel production pathways in their 2020 SOT cases. The results of these renewable hydrocarbon fuel pathways in these SCSA analyses update those for the respective 2019 SOT cases (Cai et al. 2020). They also provide an opportunity to examine the impact of technology improvements in both biomass feedstock production and biofuel production that have been achieved in 2020 SOTs on the sustainability performance of these renewable transportation fuels. The SCSA results also reflect updates to Argonne National Laboratory’s Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET®) model, which was released in October 2020 (Wang et al. 2020). These GREET updates include the production of natural gas, electricity, and petroleum-based fuels that can influence biofuels’ supply chain greenhouse gas (GHG) (CO 2 , CH 4 , and N 2 O) emissions, water consumption, and air pollutant emissions. GHG emissions, water consumption, and nitrogen oxides (NO x ) emissions are the main sustainability metrics assessed in this analysis. In this analysis, we define water consumption as the amount of water withdrawn from a freshwater source that is not returned (or returnable) to a freshwater source at the same level of quality. Life-cycle fossil energy consumption and net energy balance, which is the life-cycle fossil energy consumption deducted from the renewable biofuel energy produced, are also assessed.

09 BIOMASS FUELS↗
DOE OSTI2021

Processing of SOFC Anodes for Enhanced Intermediate Temperature Catalytic Activity at High Fuel Utilization (Final Report)

The overall objective was to infiltrate anodes with nanoparticle catalysts so that anode catalytic performance can be improved as anode operation temperature is reduced from 800°C to intermediate temperatures of 700°C and 600°C and as anode fuel utilization is increased. The addition of nickel nanoparticle catalysts into the anode improves performance by providing additional triple phase boundaries (TPBs), increasing the density of electrochemical reaction sites. To achieve this goal, both liquid phase and vapor phase methods for depositing nickel nanoparticles in the anode active layer, the region of the anode near the electrolyte where the electrochemical reaction occurs. It is imperative that nanoparticles are stable against coarsening during long-term operation, so the mechanisms and kinetics of nanoparticle stability during cell operation will be investigated. Finally, priority is given to processes that are scalable and easily transferable to industry, leveraging existing Ni-YSZ cermet anode technology. Utilizing nickel nanoparticles at different temperatures has different considerations that will be addressed. At the upper end of the intermediate temperature range (800°C), it is important that performance improvement is maintained over long periods by mitigating the instability of nanoparticles. At the middle of the temperature range (700°C), it is important that performance improvement is maintained at high fuel utilizations. At the lower end of the temperature range (600°C), where the performance of cells is poor due to increased resistances, it is important to improve anode performance by significantly increasing the electrochemical reaction site density, while nanoparticle durability is less of an issue. Finally, the objective was to explore mixed ionic and electronic (MIEC) nanoparticle catalysts like GDC to see if 2-phase boundaries can be created to increase the electrochemical reactions at the anode.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2022

Selective Catalytic Oxidations: Opportunities and Challenges for the Selective Conversion of Renewable Resources

The goal of this DOE-funded project was to investigate the fundamental science related to selective catalytic oxidation reactions for converting renewable polyhydroxylated bio-feedstocks into new classes of value-added chemicals. The focus was on selective oxidation catalysis, specifically the mechanisms and origin of chemoselectivity for the selective Pd-catalyzed aerobic oxidations of biomass-derived polyols and carbohydrates.

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

Catalytic Selective Oxidations with Porous Transition Metal Oxides

This final report covers work done concerning oxidation catalysis over the past year. There are three major areas involving synthesis, characterization, and catalysis. The synthetic focus has been on porous metal oxides. Full characterization of these systems using a variety of methods has been done using ex-situ, in situ, and operando conditions. A major goal of the work has been to study the mechanisms of catalytic oxidations including identification of reaction intermediates. Specific applications besides oxidations concern electrocatalytic water splitting, water harvesting, CO 2 capture, and environmental catalysis.

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

Customization for Current Market Applications of the Carbon Nanotubes Produced by PNNL’s Regenerable Catalytic Pyrolysis (ReCaP) for Scaled Hydrogen Production

Here, we demonstrated the Regenerative Catalytic Pyrolysis (ReCaP) process that generates carbon dioxide-free hydrogen (CO 2 -free H 2 ) from inexpensive and domestically abundant natural gas (NG), while simultaneously producing H 2 at net production cost of $1.0/kg through the sale of valuable carbon nanotube (CNT) co-product. The specific goal of this project is to 1) scale up the production of CNT, 2) correlate the properties of the CNT with the reaction conditions, 3) perform a techno-economic analysis to obtain minimum selling price of H 2 and CNT, and 4) identify industrial partners interested in the CNT co-product.

03 NATURAL GAS↗
DOE OSTI2023

Plasma-Assisted Catalytic Conversion of CO 2 and Propane to Propylene and CO

Ethylene and propylene are critical pillars of the petrochemical and plastics industry. The current industrial route for producing these olefins, which is via steam cracking process, is extremely endothermic and highly CO 2 -intensive. In this work, Susteon, in partnership with the North Carolina State University (NCSU), New Castle University (NU), and SoCalGas, has investigate catalytic materials and process designs to produce propylene from propane by utilizing CO 2 as a soft oxidant in the presence of low temperature dielectric barrier discharge plasma. This route integrates the effect of catalysis and the presence of a plasma environment to intensify the production of the important three carbon olefin from propane at a lower temperature and near atmospheric pressure. This CO 2 oxidative dehydrogenation (CO 2 -ODH) process coproduces CO, which is a valuable by-product, critical for the petrochemical sector. Through this work, Susteon and the team have made significant progress in developing catalysts and gaining insights on the plasma-assisted CO 2 -ODH process.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2023

Catalytic upgrading of ethanol to C8+ distillate range ethers via Guerbet coupling and etherification

In this presentation we describe the catalytic approaches for conversion of ethanol into diesel fuel ethers. This involves first alcohol oligomerization, followed by acid-catalyzed dehydration. As we will show in this presentation, ethanol can be converted to higher linear and α-branched alcohols by C-C coupling reactions (ethanol oligomerization) as well as to high molecular weight esters by C-O coupling reactions with Cu/MgxAlOy (CuHT) catalysts. Alcohols may be converted to ethers via bimolecular dehydration in a subsequent step. We have identified more than 160 number of species in the products including alcohols, esters, aldehydes, ketones, and olefins. Alcohols range from C4 to C10. Both alcohols and esters follow a Schulz-Flory chain growth model. We show the relationship between the catalyst properties (BET surface area, acid and base site count and Cu loading and synthesis method) and the performance in the reactions. We also show that physical mixtures of CuHT and HT can have similar product selectivity of low loading CuHT catalysts. The selectivity towards diesel fuel precursor compounds (hereafter ‘DFPC’) increased with conversion until reaching a plateau at high ethanol conversion (~70%). Alcohol selectivity follows a Schultz-Flory distribution at all studied conversions, and that adsorbed ethanol-derived species may undergo surface oligomerization into 1-butanol and higher alcohols before desorbing in a chain-growth mechanism. Zeolite catalysts convert the C4+ alcohols into C8+ ethers in both batch and continuous flow reactors. Selectivities of up to 80% to C8+ ethers at around 70% conversion using a single pass continuous flow system are achieved. The final product feedstocks obtained from etherification have been used in technoeconomic (TEA) and lifecycle analysis (LCA), which indicate a reduction in greenhouse gas (GHG) emissions of 50% relative to conventional diesel and diesel fuel prices that are lower than biodiesel. These final feedstocks are undergoing engine testing to elucidate the physiochemical properties and compare well to diesel #2 ASTM standards.

Huber, George↗