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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Synthesis of Hangman Chlorins

Two complementary rational synthetic routes have been developed in order to synthesize hangman chlorins, which differ with regard to the order of the installation (pre- and post-formation of the chlorin macrocycle) and position of the xanthene backbone about the chlorin periphery. The versatility of the synthetic method is demonstrated with the preparation of ten new hangman chlorins bearing a xanthene backbone and a pendant carboxylic acid. Cyclic voltammograms of hangman chlorins exhibit a hangman effect derived from intermolecular proton transfer. In conclusion, this hangman effect is manifested in catalytic hydrogen evolution production.

08 HYDROGEN↗
DOE OSTI2021

Selective butene formation in direct ethanol-to-C3+-olefin valorization over Zn-Y/Beta and single-atom alloy composite catalysts using in situ generated hydrogen

The selective production of C3+ olefins from renewable feedstocks, especially via C1 and C2 platform chemicals, is a critical challenge for obtaining economically viable low-carbon middle distillate transportation fuels (i.e., jet and diesel). Here, we report a multifunctional catalyst system composed of Zn-Y/Beta and “single-atom” alloy (SAA) Pt-Cu/Al2O3 which selectively catalyzes ethanol-to-olefins (C3+, ETO) valorization in the absence of cofed hydrogen, forming butenes as the primary olefin products. Beta zeolites containing predominately isolated Zn and Y metal sites catalyze ethanol upgrading steps (588 K, 3.1 kPa ethanol, ambient pressure) regardless of cofed hydrogen partial pressure (0-98.3 kPa H2), forming butadiene as the primary product (60% selectivity at 87% conversion). The Zn-Y/Beta catalyst possesses site-isolated Zn and Y Lewis acid sites (at ~7 wt% Y) and Brønsted acidic Y sites, the latter of which has been previously uncharacterized. A secondary bed of SAA Pt-Cu/Al2O3 selectively hydrogenates butadiene to butene isomers at a consistent reaction temperature using hydrogen generated in situ from ethanol-to-butadiene (ETB) conversion. This unique hydrogenation reactivity at near-stoichiometric hydrogen and butadiene partial pressures is not observed over monometallic Pt or Cu catalysts, highlighting these operating conditions as a critical SAA catalyst application area for conjugated diene selective hydrogenation at high reaction temperatures (>573 K) and low H2/diene ratios (e.g., 1:1). Single-bed steady state selective hydrogenation rates, associated apparent hydrogen and butadiene reaction orders, and DFT calculations of the Horiuti-Polanyi reaction mechanisms indicate that the unique butadiene selective hydrogenation reactivity over SAA Pt-Cu/Al2O3 reflects lower hydrogen scission barriers relative to monometallic Cu surfaces and limited butene binding energies relative to monometallic Pt surfaces. DFT calculations further indicate the preferential desorption of butene isomers over SAA Pt-Cu(111) and Cu(111) surfaces while Pt(111) surface favors subsequent butene hydrogenation reactions to form butane over butene desorption events. Under operating conditions without of hydrogen cofeeding, this combination of Zn-Y/Beta and SAA Pt-Cu catalysts can selectively form butenes (65% butenes, 78% C3+ selectivity at 94% conversion) and avoid butane formation using only in situ generated hydrogen, avoiding costly hydrogen cofeeding requirements that hinder many renewable energy processes.

Cordon, Michael↗
DOE OSTI2026

Scale-Up of Electrode Coating and Flow-Field for Commercial Hydrogen Peroxide Electrolyzer: Cooperative Research and Development Final Report, CRADA Number CRD-17-00687

Hydrogen peroxide is currently produced at central chemical plants via the anthraquinone oxidation process. This process produces environmental pollutants that are costly to remediate, requires hazardous long distance shipping of highly concentrated peroxide (50% or 70%), and necessitates extra handling costs related to storage and dilution. Peroxygen Systems, Inc. (PSi) is developing breakthrough technology for on-site hydrogen peroxide production. PSi’s on-site on-demand electrolyzer can reduce the cost of producing hydrogen peroxide by 50%, while also completely eliminating the cost and safety issues associated with shipping and handling of high concentration hydrogen peroxide. The challenge for PSi is scaling. To support the next step toward commercialization (customer pilot tests), scaling the prototype into larger single cells and 20-40 cell stacks is required. In addition to internal hardware and flow-field design efforts at PSi, NREL will address three critical problems for this scale-up effort: (1) demonstrating a large scale roll-to-roll (R2R) process to coat uniform electrode materials for 100 cm2 and 500 cm2 stack testing, (2) demonstrating an in-line diagnostic to achieve better electrode quality control, and (3) performing in situ cell/stack testing to better understand and optimize the performance of the flow field design.

28 EE - Advanced Manufacturing Office (EE-5A)↗
DOE OSTI2021

Green hydrogen from microalgal liquefaction byproducts with ammonia recovery and effluent recycle for developing circular processes

Hydrothermal liquefaction is a promising technology for microalgae-based biofuel production. However, hydrothermal liquefaction’s aqueous wastes have little established reuse, and contain significant fractions of toxic ammoniacal nitrogen. Careful reuse of this waste can assure microalgae-based biofuels are produced with less environmental impact and larger energy efficiency. Microbial electrolysis cells were investigated to valorize this waste product by converting the leftover organics into hydrogen and remove ammonia. Waste hydrothermal liquefaction aqueous phase from two microalgal strains, Tetraselmis sp. and Chlorella sp. were used as feedstocks for hydrogen production in microbial electrolysis cells. Chlorella and Tetraselmis aqueous phase-fed microbial electrolysis cells reach an average current density of 5.1 ± 0.19 A/m 2 and 3.8 ± 0.08 A/m 2 . Compound removal rates and mass removal percentages were also investigated for each feedstock. Additionally, acetic acid, propionic acid, ethanol, and glycerol were effectively removed from the aqueous byproduct. Further, microbial electrolysis cells separated up to 34.3% of ammoniacal nitrogen present in the aqueous phase. Charge transfer analysis indicated that proton transfer, not ammonium transfer, contributed to the majority of the hydrogen production in the cathode. Finally, the microbial electrolysis cell effluent was reused to grow the same microalgal strains, leading to the development of a circular biofuel production system. Microalgae regrowth studies using microbial electrolysis cell effluent showed nearly complete removal of total organic carbon, but significantly less removal of total nitrogen. Tetraselmis sp. growth occurred with the Tetraselmis-derived MEC effluent, however, the control medium without effluent produced the most growth. These findings support the possibility of a circular biofuel framework using MECs, but additional constraints, including the removal of inorganic contaminants, are necessary to realize the circular processes.

09 BIOMASS FUELS↗
DOE OSTI2024

Safety Review of the Hydrogen Components of a Reference Design of the Wind-H2-Green Steel/Ammonia Project

The Department of Energy Hydrogen Fuel Cell Technology Office and Wind Energy Technologies Office’s Wind-H2-Green Steel/Ammonia project is an initiative to demonstrate the feasibility and efficacy of GW-scale integrated energy systems. The team designed reference facilities that utilize wind- and solar-produced hydrogen for industrial steel and ammonia production. This novel concept warranted review of safety codes and standards as they apply to the designs and the identification of codes and standards as they apply to the designs and the identification of codes and standards gaps. This report reviews hydrogen production and storage codes and standards using reference design specifications from a Minnesota steel plant. Requirements, recommendations, and exclusions for the system were identified. Observed gaps included non-specific salt cavern storage requirements, electrolyzer capacity beyond regulated ranges, and lack of requirements for iron reduction via hydrogen. This report will aide future project design efforts and may provide a basis for safety reviews in new designs for industrial facilities with hydrogen production integration.

08 HYDROGEN↗
NASA NTRS1977

The Liquid Hydrogen Option for the Subsonic Transport: A status report

Continued subsonic air transport design studies include the option for a liquid hydrogen fuel system as an aircraft fuel conservation measure. Elements of this option discussed include: (1) economical production of hydrogen; (2) efficient liquefaction of hydrogen; (3) materials for long service life LH2 fuel tanks; (4) insulation materials; (5) LH2 fuel service and installations at major air terminals; (6) assessment of LH2 hazards; and (7) the engineering definition of an LH2 fuel system for a large subsonic passenger air transport.

Korycinski, P. F.↗
NASA NTRS1978

Methods for the photochemical utilization of solar energy

The paper considers the 'ground rules' which govern the efficiency of photochemical solar energy conversion and then summarizes the most promising approaches in each of three categories: photochemically assisted thermal systems for the heating and/or cooling of structures; photogalvanic systems for the production of electrical power in applications, such as photorechargeable batteries or inexpensive 'solar cells'; and photochemical formation of fuels for combustion and for use as chemical feedstocks or foods. Three concepts for the photochemical utilization of solar energy in space are found to be particularly promising: (1) photochemical trans-cis isomerization of indigold dyes for photoassisted heating or cooling, (2) the redox stabilized photoelectrolysis cell for the production of hydrogen (and/or oxygen or other useful chemicals), and (3) the liquid-junction photovoltaic cell for the production of electrical power.

Schwerzel, R. E.↗
DOE OSTI2025

Examining Metal Identity and Proximity Effects on Acetylene Hydrogenation with Azolate-Based MOFs

Liquid organic hydrogen carriers (LOHCs) are an attractive fuel source due to their compatibility with existing transportation methods and ease of use. However, they suffer from sluggish (de)hydrogenation kinetics. One promising platform for developing next-generation catalysts is metal–organic frameworks (MOFs), which can enable systematic interrogation into the influence of metal identity and spatial arrangement. In this study, the effect of the coordination environment was investigated using Ni- and Co-based azolate MOFs: MFU-4l-OH (M x Zn 5–x (OH) 4 (BTDD) 3 ; x = 4 for M = Co and x = 3 for M = Ni, H 2 BTDD = bis(1H-1,2,3-triazolo[4,5-b][4′,5′-i])dibenzo[1,4]dioxin), composed of single-site nodes, and M(OH) 2 BBTA (M = Ni, Co; H 2 BBTA = 1H,5H-benzo(1,2-d:4,5-d’)bistriazole), composed of extended chain-type nodes. The catalysts were characterized by isotherms, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and X-ray photoelectron spectroscopy (XPS) analysis. Acetylene hydrogenation activity under steady state conditions (150 °C, 1:1 C 2 H 2 :H 2 ) revealed higher turnover frequencies (TOFs) up 1.17 × 10 –2 mol C 2 H 2 mol −1 Ni min −1 and 1.98 × 10 –3 mol C 2 H 2 mol −1 Co min −1 for Ni-MFU-4l-OH and Co-MFU-4l-OH, respectively, compared to their BBTA analogues. However, the Co-based MOFs, particularly Co 2 (OH) 2 -BBTA, exhibited greater selectivity (up to 19%) for the fully hydrogenated ethane product. Isosteric heat of adsorption (Q st ) measurements for ethylene and ethane revealed that the BBTA framework had stronger binding to the products than MFU-4l. Furthermore, these findings demonstrate that metal identity and coordination environment may modulate acetylene hydrogenation performance, leading to design principles for tuning LOHC hydrogenation catalysts.

catalysts↗
DOE OSTI2022

Electrochemical Proton Insertion Modulates the Hydrogen Evolution Reaction on Tungsten Oxides

Development of new electrocatalysts for the hydrogen evolution reaction (HER) could reduce dependence on Pt and other rare metals and enable large-scale production of hydrogen with near-zero carbon emissions. Mechanistic insight into the electrocatalytic activity of a material helps to accelerate the development of new electrocatalysts. Alternative electrocatalyst materials such as transition metal oxides and sulfides can undergo insertion reactions that change their properties. Recent reports indicate that the presence of inserted ions can influence electrocatalytic activity. In this work, we utilized a materials chemistry approach to understand the role of proton insertion on the HER activity of layered tungsten oxide hydrates (WO 3 ∙xH 2 O, x = 1, 2). We synthesized a series of tungsten oxide hydrates along with an octylamine-pillared tungsten oxide (OA-WO 3 ). We used cyclic voltammetry to study the electrochemical reactivity of each material and performed ex situ X-ray diffraction and Raman spectroscopy to understand bulk and surface structural changes during electrochemical cycling. We show an inverse relationship between the degree of proton insertion and HER overpotential in tungsten oxides: the lack of proton insertion leads to a high overpotential for the HER. We discuss three hypotheses for how proton insertion leads to HER activity in WO 3 ∙xH 2 O: 1) proton insertion changes the electronic band structure of WO 3 ∙xH 2 O, 2) the presence of bulk protons can influence ΔG H,ads at the surface sites, and 3) inserted protons may participate in the HER mechanism on WO 3 ∙xH 2 O. Overall, this work shows the critical role of proton insertion in enabling high HER activity in tungsten oxides.

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

Microalgae Conversion to Biofuels and Biochemical via Sequential Hydrothermal Liquefaction (SEQHTL) and Bioprocessing: 2020 State of Technology

A preliminary techno-economic analysis (TEA) was developed for the fiscal year 2020 state of technology (SOT) assessment to evaluate the benefits and risks for a large-scale microalga hydrothermal liquefaction (HTL) system based on most recent testing results. The focus of the study is directed toward the conversion system, which consists of five processes: two-stage sequential HTL (SEQHTL), biocrude upgrading to final fuels, bioprocessing for co-product generation, hydrogen generation, and steam cycle. In this system, algae biomass with corn stover supplement during the lower algae productivity seasons (winter, fall, and spring) to match the maximum algae seasonal production rate in summer is employed to maintain a constant plant capacity in all the seasons. Algae only (summer season) or algae/corn stover blended feedstock (other seasons) are sent to a two-stage SEQHTL process. In stage I, the carbohydrates in the feedstock are extracted and separated from the residual solid. The residual solid from stage I is further converted to biocrude in the SEQHTL stage II step. The biocrude is upgraded to final fuel products in an upgrading process. The extract stream from HTL stage I is sent to the bioprocessing section for co-product generation via fermentation of carbohydrate. Lactic acid (LA) is assumed to be the co-product based on current bioprocessing testing results.

09 BIOMASS FUELS↗
NASA NTRS1999

Methane Pyrolysis and Disposing Off Resulting Carbon

Sabatier/Electrolysis (S/E) is a leading process for producing methane and oxygen for application to Mars ISPP. One significant problem with this process is that it produces an excess of methane for combustion with the amount of oxygen that is produced. Therefore, one must discard roughly half of the methane to obtain the proper stoichiometric methane/oxygen mixture for ascent from Mars. This is wasteful of hydrogen, which must be brought from Earth and is difficult to transport to Mars and store on Mars. To reduced the problem of transporting hydrogen to Mars, the S/E process can be augmented by another process which reduces overall hydrogen requirement. Three conceptual approaches for doing this are (1) recover hydrogen from the excess methane produced by the S/E process, (2) convert the methane to a higher hydrocarbon or other organic with a lower H/C ratio than methane, and (3) use a separate process (such as zirconia or reverse water gas shift reaction) to produce additional oxygen, thus utilizing all the methane produced by the Sabatier process. We report our results here on recovering hydrogen from the excess methane using pyrolysis of methane. Pyrolysis has the advantage that it produces almost pure hydrogen, and any unreacted methane can pass through the S/E process reactor. It has the disadvantage that disposing of the carbon produced by pyrolysis presents difficulties. Hydrogen may be obtained from methane by pyrolysis in the temperature range 10000-12000C. The main reaction products are hydrogen and carbon, though very small amounts of higher hydrocarbons, including aromatic hydrocarbons are formed. The conversion efficiency is about 95% at 12000C. One needs to distinguish between thermodynamic equilibrium conversion and conversion limited by kinetics in a finite reactor.

Sharma, P. K.↗
DOE OSTI2022

Discovery of LaAlO 3 as an efficient catalyst for two-electron water electrolysis towards hydrogen peroxide

Electrochemical two-electron water oxidation reaction (2e-WOR) has drawn significant attention as a promising process to achieve the continuous on-site production of hydrogen peroxide (H 2 O 2 ). However, compared to the cathodic H 2 O 2 generation, the anodic 2e-WOR is more challenging to establish catalysts due to the severe oxidizing environment. In this study, we combine density functional theory (DFT) calculations with experiments to discover a stable and efficient perovskite catalyst for the anodic 2e-WOR. Our theoretical screening efforts identify LaAlO 3 perovskite as a stable, active, and selective candidate for catalyzing 2e-WOR. Our experimental results verify that LaAlO 3 achieves an overpotential of 510 mV at 10 mA cm -2 in 4 M K 2 CO 3 /KHCO 3 , lower than those of many reported metal oxide catalysts. In addition, LaAlO 3 maintains a stable H 2 O 2 Faradaic efficiency with only a 3% decrease after 3 h at 2.7 V vs. RHE. This computation-experiment synergistic approach introduces another effective direction to discover promising catalysts for the harsh anodic 2e-WOR towards H 2 O 2 .

08 HYDROGEN↗
NASA NTRS1977

The liquid hydrogen option for the subsonic transport - A status report

Studies dealing with the use of liquid hydrogen for fuel in subsonic air transport systems are reviewed. Topics of the studies include the possibility for economical production of hydrogen, the problems associated with the efficient liquefaction of the gas, the development of insulation materials and materials for long-lasting liquid hydrogen fuel tanks, the difficulties related to fueling processes and the installation of liquid hydrogen fuel stations at major air terminals, an assessment of the hazards connected with liquid hydrogen fuels, and the engineering and design problems involved in incorporating liquid hydrogen fuel systems into large subsonic passenger aircraft.

Korycinski, P. F.↗
DOE OSTI2023

Reference Station Design for Heavy-Duty Vehicles

Five alternative design configurations for a heavy-duty hydrogen refueling truck stop are detailed in this work. Each of the station concepts provides fast, 5-minute, 50 kg fills of up to 4 vehicles simultaneously, with a station capacity of 4200 kg/day. Two on-site production stations using PEM electrolysis are considered: one with off-peak production of the daily capacity; and one with on-demand production of hydrogen during vehicle refueling. Three delivered liquid hydrogen station concepts are considered: one with the same, high-pressure cascade storage system for dispensing as the electrolysis supplied stations, with low-pressure vaporization of the liquid hydrogen and pressurization via a compressor; and two with on-demand pressurization: one by low-pressure vaporization and compressors; and one with a cryogenic pump and high-pressure vaporization. Design, economic, and operational considerations for each of the components needed in these station concepts is provided. Of all the station concepts, the delivered liquid station with a low-pressure vaporizer and a cascade dispensing system has the lowest capital costs and equipment footprint, but the second highest operating costs primarily due to high costs for liquid hydrogen delivery. The lowest operating cost station is that with on-site production via PEM electrolysis at off-peak hours with a cascade delivery system. The low-pressure buffer storage system and electrolyzers have a large footprint and considerable capital costs, but could result in a low total cost of ownership, depending on the design timeline. The liquid hydrogen station with a cryo-pump has moderate capital costs, the lowest operating costs of the three delivered hydrogen stations, and the same small equipment footprint as the delivered liquid, cascade dispensing system. As cryogenic pumping technology improves and the capital costs for these pumps decreases, this station concept will become even more favorable. Three-dimensional renderings of the five station concepts provide station designers with a starting point for the development of heavy-duty refueling stations.

08 HYDROGEN↗
NASA NTRS1998

Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HO, required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production Of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about I part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more 03 than expected.

Wennberg, P. O.↗
NASA NTRS1998

Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HO(sub x) required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.

Wennberg, P. O.↗
NASA NTRS1998

Hydrogen Radicals, Nitrogen Radicals, and the Production of O3 in the Upper Troposphere

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3, in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HO(x) required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of 03 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day.This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more 03 than expected.

Wennberg, P. O.↗
DOE OSTI2021

MW-Scale PEM-Based Electrolyzers for RES Applications (CRADA CRD-18-00742 Final Report)

Many nations are rapidly increasing electrical generation capacity from renewable energy sources (RES) such as wind and solar. The wide penetration of RES requires an energy storage solution which has come in the form of hydrogen generated via polymer exchange membrane (PEM) electrolysis. A study of the current state-of-the-art PEM electrolysis indicates that the largest PEM-based stacks range from 150 - 250kW and that a significant scale-up of the technology is required to accommodate multi-Megawatt (MW) energy storage solutions in large-scale RES applications.

08 HYDROGEN↗