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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Phosphonic acid modifiers for enhancing selective hydrodeoxygenation over Pt catalysts: The role of the catalyst support

Bifunctional catalysts comprised of both noble metal and Bronsted acid sites are of growing interest for many reactions, such as the hydrodeoxygenation (HDO) of oxygenates produced by the deconstruction of lignocellulosic biomass. One method of preparing a bifunctional metal-acid catalyst is to modify the supporting material of a metal catalyst with acid-containing ligands, such as phosphonic acids (PAs), which provide tunable Bronsted acid sites at the metal-support interface. Here, we explore the potential for PA modification to improve HDO rates on Al 2 O 3 , TiO 2 , CeO 2 , and SiO 2 -Al 2 O 3 supports. PAs containing either alkyl or carboxylic acid (CA) tails were used to modify Pt catalysts on each support. PA modification improved HDO rates for the model compound benzyl alcohol when applied to Pt supported by Al 2 O 3 , TiO 2 , and CeO 2 , but had a negative effect on the HDO rate of Pt/SiO 2 -Al 2 O 3 . Measurements of the relative strength of Bronsted acid sites present on the modified and unmodified catalysts suggested that PAs improved HDO when they provided new or stronger Bronsted acid sites. Additionally, the strength of the Bronsted acid sites provided by PA modifiers were tunable by altering the tail functionality, which affected the rates of HDO. These results suggest that PAs can be used to modify a variety of supports to prepare bifunctional acid-metal catalysts.

09 BIOMASS FUELS↗
DOE OSTI2023

Dual atom catalysts for rapid electrochemical reduction of CO to ethylene

Strong CO adsorption and facile CO dimerization are the key challenges in electrochemical CO2 reduction towards multi-carbon (C2+) products. We recently showed that CoPc immobilized on a single-walled carbon nanotube can selectively reduce CO2 to methanol. This is enabled through molecular strain, which dramatically improves the CO adsorption energy to CoPc, which in turn facilitates methanol formation. We now examine the extended Phthalocyanine (PcEx) dual atom catalyst (DAC), which is intrinsically strained and contains two catalyst centers, making it a candidate for reducing CO to C2+ products. Using Quantum Mechanics (QM), we screened 20 elements embedded in the PcEx, seeking catalysts with weak hydrogen binding, strong CO binding, and facile CO dimerization. We identi>ied Fe, Ru, Co, and Ir as the best performers and subsequently evaluated the entire CO to C2H4 mechanism (9 steps) using each of these elements as catalysts. In terms of limiting potential and overall exergonicity, we identi>ied CoPcEx as the best catalyst, followed by IrPcEx. We then examined the full CO to C2H4 mechanism on the bimetallic IrCoPcEx catalyst using grand canonical QM to obtain the reaction energetics as a function of applied potential. We conclude that the bimetallic IrCoPcEx is most promising for ef>iciently converting CO to ethylene.

Musgrave, Charles B.↗
DOE OSTI2018

ElectroCat: DOE's approach to PGM-free catalyst and electrode R&D

The successful development of high-performance, durable platinum group metal-free (PGM-free) electrocatalysts and electrodes for polymer electrolyte membrane fuel cells (PEMFCs) will ultimately improve the cost-competiveness of fuel cells in a wide range of applications. This is considered to be a critical development especially for automotive fuel cell applications in order to bring the system cost of an automotive fuel cell system down to the $30/kW cost target set by the U.S. Department of Energy (DOE). The platinum group metal (PGM) electrocatalysts are a major contributor to the system cost. Addressing the technical challenges to PGM-free electrocatalyst and electrode development, therefore, represents one of DOE's most pressing research and development (R&D) priorities. ElectroCat was formed by the DOE as part of the Energy Materials Network (EMN) in early 2016, and shares with other EMN consortia the goal of decreasing the time to market for advanced materials related to clean energy technologies, in the context of increasing U.S. fuel cell electric vehicle (FCEV) manufacturing competitiveness. To accomplish this, the consortium performs core research and development and provides universities and companies streamlined access to the unique, world-class set of tools and expertise relevant to early-stage applied PGM-free catalyst R&D of the member national laboratories. Moreover, ElectroCat fosters a systematic methodology by which prospective catalysts and electrodes are prepared and analyzed rapidly and comprehensively using high-throughput, combinatorial methods. Catalyst discovery is augmented by theory as well as foundational electrocatalysis and materials knowledge at the participating national laboratories. Furthermore, ElectroCat has developed a data sharing framework, requisite of all EMN consortia, for disseminating its findings to the public via a searchable database, to further expedite incorporation of PGM-free electrocatalysts into next-generation fuel cells by advancing the general understanding of the PGM-free electrocatalyst field.

Thompson, Simon T.↗
DOE OSTI2017

Investigation of Silica-Supported Vanadium Oxide Catalysts by High-Field 51 V Magic-Angle Spinning NMR

Supported V2O5/SiO2 catalysts were studied using solid state 51V MAS NMR at a sample spinning rate of 36 kHz and at a magnetic field of 19.975 T for a better understanding of the coordination of the vanadium oxide as a function of environmental conditions . Structural transformations of the supported vanadium oxide species between the catalyst in the dehydrated state and hydrated state under an ambient environment were revisited to examine the degree of oligomerization and the effect of water. The experimental results indicate the existence of a single dehydrated surface vanadium oxide species that resonates at -675 ppm and two vanadium oxide species under ambient conditions that resonate at -566 and -610 ppm, respectively. No detectable structural difference was found as a function of vanadium oxide loading on SiO2 (3% V2O5/SiO2 and 8% V2O5/SiO2). Quantum chemistry simulations of the 51V NMR chemical shifts on predicted surface structures were used as an aide in understanding potential surface vanadium oxide species on the silica support. The results suggest the formation of isolated surface VO4 units for the dehydrated catalysts with the possibility of dimer and cyclic trimer presence. The absence of bridging V-O-V vibrations (~200-300 cm-1) in the Raman spectra [Gao et al. J. Phys. Chem. B 1998, 102, 10842-10852], however, indicates that the isolated surface VO4 sites are the dominant dehydrated surface vanadia species on silica. Upon exposure to water, hydrolysis of the bridging V-O-Si bonds is most likely responsible for the decreased electron shielding experienced by vanadium. No indicators for the presence of hydrated decavanadate clusters or hydrated vanadia gels previously proposed in the literature were detected in this study.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2019

Catalysts in Coronas: A Surface Spatial Confinement Strategy for High-Performance Catalysts in Methane Dry Reforming

One of the grand challenges in industrial catalytic processes is the inevitable sintering and aggregation of conventional supported catalysts to large particles, leading to the decrease of activity and even deactivation with time. Herein, a surface spatial confinement strategy was employed to design high-performing catalysts for the dry reforming of methane (DRM). Specifically, active nickel (Ni) nanoparticles (NPs) were confined on the surface of a dendritic mesoporous silica (DMS) in the form of the “catalysts in coronas”. The Ni/DMS catalyst exhibited a high catalytic performance close to its equilibrium conversion (76% conversion for CH4 at 700 °C). More importantly, the prepared catalyst remained stable after 145 h time-on-stream at 700 °C without noticeable carbon deposition. This sintering and coking resistance was found to arise from the surface spatial confinement effect in which the three-dimensional dendritic layers in the corona posted a steric barrier against migration and aggregation of Ni NPs and size of Ni NPs was controlled below 5 nm, hence against sintering and coking. Meanwhile, the mesoporous feature of the layered wall facilitated mass transport of reactants to Ni species and further boosted catalysis. This strategy should be broadly applicable to a range of metal- and metal oxide-supported catalysts in high-temperature heterogeneous reactions, such as DRM, water gas shift reaction, and vehicle emission control related reactions.

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

Ion-Pair Reorganization Regulates Reactivity in Photoredox Catalysts

Cyclometalated and polypyridyl complexes of d6 metals are promising photoredox catalysts, using light to drive reactions with high kinetic or thermodynamic barriers via the generation of reactive radical intermediates. However, while tuning of their redox potentials, absorption energy, excited-state lifetime and quantum yield are well-known criteria for modifying activity, other factors could be important. Here we show that dynamic ion-pair reorganization controls the reactivity of a photoredox catalyst, [Ir[dF(CF3)ppy]2(dtbpy)]X. Time-resolved dielectric-loss experiments show how counter-ion identity influences excited-state charge distribution, evincing large differences in both the ground- and excited-state dipole moment depending on whether X is a small associating anion (PF6-) that forms a contact-ion pair versus a large one that either dissociates or forms a solvent-separated pair (BArF4-). These differences correlate with the reactivity of the photocatalyst toward both reductive and oxidative electron transfer, amounting to a 4-fold change in selectivity toward oxidation versus reduction. These results suggest that ion pairing could be an underappreciated factor that modulates reactivity in ionic photoredox catalysts.

catalysis↗
DOE OSTI2021

Stable and selective catalysts for propane dehydrogenation operating at thermodynamic limit

Hitting the limits on propene synthesis The greater abundance of propane from shale gas has spurred efforts to use it as a propylene feedstock. Direct dehydrogenation catalysts consisting of platinum–tin alloy nanoparticles supported on alumina often must run with hydrogen dilution to avoid carbon buildup and excess tin to avoid alloy segregation. Motagamwala et al. report that platinum–tin nanoparticles interact more weakly with a silica support and the metals thus do not segregate. The use of undiluted reactants allowed the reaction to run near the thermodynamically limit of about 67% conversion with a selectivity to propylene of more than 99%. This catalyst also does not build up carbon and could run up to 30 hours without deactivation. Science , abg7894, this issue p. 217

Science & Technology - Other Topics↗
NASA NTRS1976

Preliminary results from screening tests of commercial catalysts with potential use in gas turbine combustors. Part 1: Furnace studies of catalyst activity

Thirty commercially produced monolith and pellet catalysts were tested as part of a screening process to select catalysts suitable for use in a gas turbine combustor. The catalysts were contained in a 1.8 centimeter diameter quartz tube and heated to temperatures varying between 300 and 1,200 K while a mixture of propane and air passed through the bed at space velocities of 44,000 to 70,000/hour. The amount of propane oxidized was measured as a function of catalyst temperature. Of the samples tested, the most effective catalysts proved to be noble metal catalysts on monolith substrates.

Anderson, D. N.↗
NASA NTRS1976

Preliminary results from screening tests of commercial catalysts with potential use in gas turbine combustors. I - Furnace studies of catalyst activity

Thirty commercially produced monolith and pellet catalysts were tested as part of a screening process to select catalysts suitable for use in a gas turbine combustor. The catalysts were contained in a 1.8 centimeter diameter quartz tube and heated to temperatures varying between 300 and 1200 K while a mixture of propane and air passed through the bed at space velocities of 44,000 to 70,000 per hour. The amount of propane oxidized was measured as a function of catalyst temperature. Of the samples tested, the most effective catalysts proved to be noble metal catalysts on monolith substrates.

Anderson, D. N.↗
NASA NTRS1980

Durability testing at 5 atmospheres of advanced catalysts and catalyst supports for gas turbine engine combustors

The durability of CATCOM catalysts and catalyst supports was experimentally demonstrated in a combustion environment under simulated gas turbine engine combustor operating conditions. A test of 1000 hours duration was completed with one catalyst using no. 2 diesel fuel and operating at catalytically-supported thermal combustion conditions. The performance of the catalyst was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. Tests were performed periodically to determine changes in catalytic activity of the catalyst core. Detailed parametric studies were also run at the beginning and end of the durability test, using no. 2 fuel oil. Initial and final emissions for the 1000 hours test respectively were: unburned hydrocarbons (C3 vppm):0, 146, carbon monoxide (vppm):30, 2420; nitrogen oxides (vppm):5.7, 5.6.

Olson, B. A.↗
DOE OSTI2015

Supported catalyst systems and method of making biodiesel products using such catalysts

A heterogeneous catalyst system, a method of preparing the catalyst system and a method of forming a biodiesel product via transesterification reactions using the catalyst system is disclosed. The catalyst system according to one aspect of the present disclosure represents a class of supported mixed metal oxides that include at least calcium oxide and another metal oxide deposited on a lanthanum oxide or cerium oxide support. Preferably, the catalysts include CaO--CeO.sub.2ZLa.sub.2O.sub.3 or CaO--La.sub.2O.sub.3/CeO.sub.2. Optionally, the catalyst may further include additional metal oxides, such as CaO--La.sub.2O.sub.3--GdOxZLa.sub.2O.sub.3.

09 BIOMASS FUELS↗
DOE OSTI2023

Three-way catalyst with reduced palladium loading and method of making the three-way catalyst

A three-way catalyst for reduced palladium loading is provided. The catalyst includes an inert substrate and a palladium catalyst material coating the substrate. The palladium catalyst material includes a support material formed from one of 10% CeO 2 /Al 2 O 3 , 20% CeO 2 —Al 2 O 3 (20CeAlOy), 30% CeO 2 —Al 2 O 3 (30CeAlOy), Al 2 O 3 , and MOx-Al 2 O 3 , wherein M is one of copper, iron, manganese, titanium, zirconium, magnesium, strontium, and barium. The palladium catalyst material includes a layer of CeO 2 material disposed upon the support material, wherein the layer of CeO 2 material is dispersed on a surface of the support material. The palladium catalyst material includes an active component including a layer of praseodymium oxide particles dispersed across the surface of the layer of CeO 2 material and a layer of palladium particles disposed upon and dispersed across the surface of the layer of CeO 2 material at locations each corresponding to a respective location of each of the praseodymium particles.

Gu, Yuntao↗
DOE OSTI2019

Distinguishing Plasma Contributions to Catalyst Performance in Plasma-Assisted Ammonia Synthesis

Plasma-assisted catalysis is the process of electrically activating gases in the plasma-phase at low temperatures and ambient pressure to drive reactions on catalyst surfaces. Plasma-assisted catalytic processes combine conventional heterogeneous surface reactions, homogeneous plasma phase reactions, and coupling between plasma-generated species and the catalyst surface. Herein, we perform kinetically controlled ammonia synthesis measurements in a dielectric barrier discharge (DBD) plasma-assisted catalytic reactor. We decouple contributions due to plasma phase reactions from the overall plasma-assisted catalytic kinetics by performing plasma-only experiments. By varying the gas composition, temperature, and discharge power, we probe how macroscopic reaction conditions affect plasma-assisted ammonia synthesis on three different γ-alumina-supported transition metal catalysts (Ru, Co, and Ni). Our experiments indicate that the overall reaction and plasma-phase reaction are first-order in both N 2 and H 2 . In contrast, the rate contributions due to plasma-catalyst interactions are first-order in N 2 but zeroth order in H 2 . Furthermore, we find that the tuning of the plasma discharge power is more effective in controlling catalytic performance than the increasing of bulk gas temperature in plasma-assisted ammonia synthesis. Lastly, we show that adding a catalyst to the DBD reaction alters the way that productivity scales with the specific energy input (SEI).

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

Degradation of Platinum-Cobalt Alloy PEMFC Cathode Catalysts in Catalyst-Ionomer Inks

In this paper we report on studies of the effects of catalyst-ionomer ink composition: ionomer equivalent weight (EW), ink solvent, and ink mixing on a commercial PtCo alloy PEMFC cathode catalyst. X-ray absorption spectroscopy (XAS) and wide-angle X-ray scattering (WAXS) are utilized to determine catalyst atomic structure, catalyst crystallite composition, and extent of loss of Co into the ionomer-solvent phase. Three different n-propanol to water weight ratios (7:3, 5:5, and 3:7) and two different ionomers (3 M 800 EW and Nafion 1000 EW) were studied. Cobalt loss from the PtCo particles was found to increase with increasing water content in the inks and to be more extensive for the 800 EW ionomer inks, causing loss of contraction of the PtCo lattice and formation of a Pt shell-PtCo alloy core intraparticle structure.

25 ENERGY STORAGE↗