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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Silver-Promoted Dehydroaromatization of Ethylene over ZSM-5 Catalysts

The shape selectivity of ZSM-5 (MFI type) catalysts is ideal for the production of C 6 –C 8 aromatics. Developing high-performance zeolite catalysts with improved selectivity to aromatics, particularly from diversified (non-petroleum) feedstocks, has broad commercial appeal. Non-oxidative coupling (NOC) of ethylene was examined over Ag-ZSM-5 catalysts at 400 °C and shows that Ag + sites promote dehydroaromatization with enhanced selectivity to toluene and xylenes. Metal exchange of H-ZSM-5 results in Ag zoning wherein Ag + site density is higher on the exterior of ZSM-5 particles. Catalyst performance was characterized with varying Ag loading as well as the use of methane co-feed. Aromatic selectivity is about 60 % on Ag-ZSM-5 compared to 20 % on H-ZSM-5, which is qualitatively consistent with density functional theory (DFT) showing that ethylene forms strong complexes with Ag + (Lewis acid) sites. DFT calculations also reveal that ethylene activation on H + (Brønsted acid) sites is more energetically favorable, and likely constitutes the first mechanistic step in ethylene-to-liquids (ETL) reactions. Ag-ZSM-5 is thus identified as an effective catalyst for low-temperature ETL reactions that has the potential to outperform conventional metal-exchanged zeolites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Copper-Cobalt-Cerium Ternary Oxide as an Additive to a Conventional Platinum-Group-Metal Catalyst for Automotive Exhaust Catalysis

Recently, we reported on a ternary mixed-oxide catalyst that showed low-temperature CO oxidation activity under lean exhaust conditions without inhibition by hydrocarbons such as propene. However, the hydrocarbon oxidation activity of this Cu–Co–Ce (CCC) catalyst cannot be considered as a stand-alone solution to low-temperature automotive exhaust catalysis. To achieve both low-temperature oxidation of pollutants and a reduction in the total platinum-group-metal (PGM) content, we examined a 50 % physical mixture of traditional Pt/Al 2 O 3 and our CCC catalyst in two simulated exhaust protocols. Using this physical mixture, we were able to obtain equivalent or better hydrocarbon activity than the baseline Pt/Al 2 O 3 catalyst with half the total PGM content as well as increased sulfur tolerance for the CCC component of the mixture. Diffuse reflectance infrared Fourier transform spectroscopy data confirmed that despite exposure of sulfur-sensitive CCC to SO 2 , Cu + -carbonyl binding sites could still be seen if the catalyst was mixed with Pt/Al 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Ultra-Stable and High-Cobalt-Loaded Cobalt@Ordered Mesoporous Carbon Catalysts: All-in-One Deoxygenation of Ketone into Alkylbenzene

Catalytic deoxygenation represents a straightforward and core methodology for fine-chemical production and biomass upgrading. Generally, the application of homogeneous metal complexes or heterogeneous noble-metal catalysts prevails in academia and the chemical industry. We introduce cobalt@ordered mesoporous carbon (Co@OMC) catalysts, which are constructed conveniently by a mechanochemical coordination self-assembly based on a renewable tannin precursor. Importantly, the Co@OMC catalysts with a high loading of in situ confined Co species promote the selective deoxygenation of various ketones, aldehydes, and alcohols efficiently into the corresponding alkanes under mild conditions. Therefore, a simple, inexpensive, and heterogeneous catalyst for selective deoxygenation can be expected, meanwhile the solid-state synthesis affords a green, rapid, and scalable pathway to Co@OMC catalysts.

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

Bidentate N‐based Ligands for Highly Reusable, Ligand‐coordinated, Supported Pt Hydrosilylation Catalysts

Abstract A significant challenge in designing supported metal‐ligand catalysts for solution‐phase reactions is the stabilization of the metal active sites against leaching into solution. Here, we examine alkene hydrosilylation reactions as model systems to improve the stability of highly dispersed Pt using a metal‐ligand coordination strategy on high surface area oxide supports. By evaluating a series of bidentate N‐based ligands, we demonstrate several design strategies to improve stability of the highly dispersed Pt 2+ centers against leaching, while maintaining a high level of catalytic activity, selectivity, and recyclability for alkene hydrosilylation batch reactions under mild conditions. These involve a bi‐functional approach to ligand design, which considers interaction to the support and a well‐defined coordination environment for the metal active site. Three strategies are reported: modifying ligands for stronger interaction with oxide surfaces, mixing ligands, and pre‐depositing an “anchoring ligand” to the support before loading the metal‐ligand catalyst. Each of these is successful in enhancing Pt recyclability. Particularly, two Pt‐phenanthroline catalysts exhibit excellent reusability for multiple batch reaction cycles, due to high stability of the active Pt species. Addressing the active site leaching problem significantly enhances the utility of ligand‐coordinated supported metal catalysts as highly stable and selective catalysts for solution‐phase reactions.

Chen, Linxiao↗
DOE OSTI2023

Highly Active and Stable Single Atom Rh 1 /CeO 2 Catalyst for CO Oxidation during Redox Cycling

We report a single atom Rh 1 /CeO 2 catalyst prepared by the high temperature (800 °C) atom trapping (AT) method which is stable under both oxidative and reductive conditions. Infrared spectroscopic and electron microscopy characterization revealed the presence of exclusively ionic Rh species. These ionic Rh species are stable even under reducing conditions (CO at 300 °C) due to the strong interaction between Rh and CeO 2 achieved by the AT method, leading to high and reproducible CO oxidation activity regardless of whether the catalyst is reduced or oxidized. In contrast, ionic Rh species in catalysts synthesized by a conventional impregnation approach (e. g., calcined at 350 °C) can be readily reduced to form Rh nanoclusters/nanoparticles, which are easily oxidized under oxidative conditions, leading to loss of catalytic performance. The single atom Rh 1 /CeO 2 catalysts synthesized by the AT method do not exhibit changes during redox cycling hence are promising catalysts for emission control where redox cycling is encountered, and severe oxidation (fuel cut) leads to loss of performance.

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

PdCu Alloy Catalyst for Inhibition‐free, Low‐temperature CO Oxidation

Designing robust catalysts for low‐temperature oxidation is pertinent to the development of advanced combustion engines to meet increasingly stringent emissions limitations. Oxidation of CO, hydrocarbon, and NO pollutants over platinum‐group catalysts suffer from strong inhibition due to their competitive adsorption, while coinage metals are generally slow at activating O 2 . Through computational screening, we discovered a PdCu alloy catalyst that completely oxidizes CO below 150 °C without inhibition by NO, propylene or water. This is attributed primarily to geometric effects and the presence of CO bound to Pd sites within the Cu‐rich surface of the PdCu alloy. Here, we demonstrate that the novel PdCu catalyst can be used in tandem with a PtPd catalyst to achieve sequential, inhibition‐free, complete oxidation of CO in a two‐bed system, while also achieving 50 % NO conversion below 120 °C. Moreover, neither water nor propylene adversely affect the low temperature CO oxidation activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Novel Hybrid Catalyst for the Oxidation of Organic Acids: Pd Nanoparticles Supported on Mn-N-3D-Graphene Nanosheets

This paper reports the fabrication and electrochemical performance of a hybrid catalyst composed of Pd nanoparticles and atomically dispersed Mn active centers integrated into the nitrogen-doped three-dimensional graphene nanosheets (Pd/Mn-N-3D-GNS). Our results show that the synergistic integration of both Pd nanoparticles and atomically dispersed Mn can be used to enhance the activity toward the electrochemical oxidation of organic acids at biologically relevant pH values. The hybrid catalyst (Pd/Mn-N-3D-GNS) showed increased maximum currents toward the oxidation of oxalic acid when compared to its individual catalysts, namely, Pd/3D-GNS and Mn N-3D-GNS catalysts. The hybrid also showed a decreased onset potential for oxidation of mesoxalic acid as compared to Mn-N-3D-GNS and decreased onset potentials for the oxidation of glyoxalic acid when compared to both of its constituent catalysts. Oxidation of formic acid was also tested and the hybrid was shown to catalyze both dehydration and dehydrogenation mechanisms of formic acid electro-oxidation. Using density functional theory calculations, it was elucidated that a two-site catalysis most likely promotes dehydrogenation reaction for formic acid oxidation, which can explain the selectivity of Pd nanoparticles and atomically dispersed Mn towards the dehydrogenation/ dehydration pathway.

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

Material Changes in Electrocatalysis: An In Situ/Operando Focus on the Dynamics of Cobalt‐Based Oxygen Reduction and Evolution Catalysts

Abstract The shift towards cheaper, non‐platinum group metal electrocatalyst materials for clean energy technologies is coupled with challenges in maintaining long‐term performance. For practical purposes, electrocatalytic stability typically focuses on catalyst electrochemical performance over time. However, a deeper understanding of catalyst material property changes during operation is needed to enable material‐specific design strategies for long‐term stabilization. In the last several decades, improvements in material characterization techniques have made it possible to probe the composition, structure, and degradation products of catalysts in situ/operando. Herein we review the current understanding of in situ/operando material stability of Co‐based electrocatalysts for the oxygen evolution (OER) and reduction reactions (ORR) in acidic and alkaline environments. We focus on in situ/operando materials characterization of three categories of Co‐based OER/ORR catalysts: oxides and (oxy)hydroxides, mixed‐metal catalysts, and non‐oxide materials. This review aims to compile and compare the results from multiple studies and techniques to provide insight into the role that the starting material, pH, and applied potential have on the active surface and stability of Co‐based materials. We conclude by highlighting directions that have been underexplored with opportunities for continued research including improving in situ/operando characterization, methods to probe long‐term material changes, and the development of operando studies on full‐scale devices. Using Co‐based materials as a case study, this review shows the vital role that in situ/operando characterization must play in the future of improving electrocatalyst stability.

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

From Sugars to Wheels: The Conversion of Ethanol to 1,3-Butadiene over Metal-Promoted Magnesia-Silicate Catalysts

1,3-Butadiene (1,3-BD) is a high-value chemical intermediate used mainly as a monomer for the production of synthetic rubbers. The ability to source 1,3-BD from biomass is of considerable current interest because it offers the potential to reduce the life-cycle greenhouse gas (GHG) impact associated with 1,3-BD production from petroleum-derived naphtha. Here in this paper, we report the development and investigation of a new catalyst and process for the one-step conversion of ethanol to 1,3-BD. The catalyst is prepared by the incipient impregnation of magnesium oxide onto a silica support followed by the deposition of Au nanoparticles by deposition-precipitation. The resulting Au/MgO-SiO 2 catalyst exhibits a high activity and selectivity to 1,3-BD and low selectivities to diethyl ether, ethylene, and butenes. Detailed characterization of the catalyst shows that the desirable activity and selectivity of Au/MgO-SiO 2 are a consequence of a critical balance between the acidic-basic sites associated with a magnesium silicate hydrate phase and the redox properties of the Au nanoparticles. A process for the conversion of ethanol to 1,3-BD, which uses our catalyst, is proposed and analyzed to determine the life-cycle GHG impact of the production of this product from biomass-derived ethanol. We show that 1,3-BD produced by our process can reduce GHG emissions by as much as 155 % relative to the conventional petroleum-based production of 1,3-BD.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Key Single-Atom Electrocatalysis in Metal-Organic Framework (MOF)-Derived Bifunctional Catalysts

Metal-organic framework (MOF)-derived materials have attracted increasing interest and show promising catalytic performances in many fields. Intensive efforts have been focused on the structure design and metal-site integration in MOF-derived catalysts. However, the key catalytic processes related with the metal sites in MOF-derived catalysts that dominate the electrocatalytic performance still remain obscure. Herein, we show a neglected but critical issue in the pyrolytic synthesis of MOF-derived catalysts: the coupled evolution of dual sites, that is, metallic sites and single-atom metal sites. The identification of active sites of single-atom sites from the visible particles has been elucidated through the combined X-ray spectroscopic, electron microscopic, and electrochemical studies. Interestingly, after a total removal of metallic cobalt sites, catalysts with purified single-atom metal sites show no faltering activity for either the oxygen reduction reaction (ORR) or hydrogen evolution reaction (HER), while significantly enhanced ORR selectivity is achieved; this reveals the dominant activity and selectivity contribution from single-atom electrocatalysis. The insight of the coupled evolution of dual sites and the as-demonstrated dual-site decoupling strategies open up a new routine for the design and synthesis of MOF-derived catalysts with the optimized single-atom electrocatalysis towards various electrochemical reactions.

electrocatalysis↗
DOE OSTI2019

Electrocatalytic CO 2 Reduction with a Ruthenium Catalyst in Solution and on Nanocrystalline TiO 2

A Ru II complex [Ru(PO 3 Et 2 -ph-tpy)(6-mbpy)(NCCH 3 )] 2+ [PO 3 Et 2 -ph-tpy=diethyl(4-[(2,2':6',2"-terpyridin)-4'-yl]phenyl)phosphonate; 6-mbpy=6-methyl-2,2'-bipyridine] is explored as a molecular catalyst for electrocatalytic CO 2 reduction in both a homogeneous solution and, as a phosphonated derivative, on nanocrystalline-TiO 2 surfaces. In CH 3 CN, the complex acts as a selective electrocatalyst for reduction of CO 2 to CO at a low overpotential of 340 mV but with a limited turnover number (TON). An enhancement in reactivity was observed by immobilizing the phosphonated derivative of the catalyst on a nanocrystalline-TiO 2 electrode surface, with the catalyst surface protected by a thin overlayer of NiO. The surface-functionalized electrode was characterized by X-ray photoelectron and diffuse reflectance spectroscopies (XPS and DRS). Electrocatalytic reduction of CO 2 to CO occurred at -1.65 V versus Fc +/0 with a TON of 237 per catalyst site during 4 h of electrocatalysis. Post-catalysis XPS measurements reveal that the molecular structure of the catalyst is retained on TiO 2 after the long-term electrocatalysis.

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

Development of Molybdenum Phosphide Catalysts for Higher Alcohol Synthesis from Syngas by Exploiting Support and Promoter Effects

Molybdenum phosphide (MoP) catalysts have recently gained attention because of their robust methanol synthesis activity from CO/CO 2 . Synthesis strategies are used to steer MoP selectivity toward higher alcohols by investigating the promotion effects of alkali (K) and CO-dissociating (Co, Ni) and non-CO-dissociating (Pd) metals. Systematic research with transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy (XAS) showed that critical parameters governing the activity of MoP catalysts are P/Mo ratio and K loading, both facilitating MoP formation. The kinetic studies of mesoporous silica-supported MoP catalysts show a twofold role of K, which also acts as an electronic promoter by increasing the total alcohol selectivity and chain length. Palladium (Pd) increases CO conversion, but decreases alcohol chain length. The use of mesoporous carbon (MC) support has the most significant effect on catalyst performance and yields a KMoP/MC catalyst that ranks among the state-of-the-art in terms of selectivity to higher alcohols.

10 SYNTHETIC FUELS↗
DOE OSTI2014

Comparison of reduced and sulfided C o M o/γ‐ A l 2 O 3 catalyst on hydroprocessing of pretreated bio‐oil in a continuous packed‐bed reactor

Pretreated bio‐oil was hydroprocessed with conventional sulfided CoMo/γ‐Al 2 O 3 catalyst in a continuous packed‐bed reactor. Hydroprocessing experiments were performed at a temperature of 350 to 400°C, 1500 psig hydrogen pressure, using a hydrogen flow rate of 500 mL/min at a liquid hourly space velocity of 0.2 h −1 . The results from sulfided catalytic experiments were compared with our prior studies on hydroprocessing pretreated bio‐oil with reduced CoMo/γ‐Al 2 O 3 catalyst. sulfided CoMo/γ‐Al 2 O 3 catalyst demonstrated higher catalytic activity and resulted in increased hydrocarbon fraction yields. Moreover, the quality of the hydrocarbon fraction, as determined by the acid value, higher heating value, and water content analysis, also improved. Sulfided CoMo/γ‐Al 2 O 3 catalyst produced a hydrocarbon fraction having a higher heating value of 44.4 MJ/kg, acid value of 0.5 mg KOH/g oil, and a total water content of 0.1%. Use of sulfided catalyst for hydroprocessing pretreated bio‐oil decreased the oxygen content from 47.8 wt % in the pretreated bio‐oil to nondetectable limits (∼0 wt %) in the hydrocarbon fraction. The hydrocarbon fraction was also analyzed by detailed hydrocarbon analysis and simulated distillation. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 1174–1179, 2015

Parapati, Divya R.↗
DOE OSTI2025

The Triple Catalytic Action of Tertiary Nitrogen Catalysts in Recyclable Epoxy-Anhydride Thermosets

The thermosetting polymer matrix in fiber reinforced composites is an important component for energy related applications, such as the lightweighting of vehicles or their use in wind and waterpower turbine blades, due to their ability to provide superior adhesion, stiffness, and applicability to a wide range of manufacturing processes. Despite these benefits, today's thermosets are widely considered to be unrecyclable; thus, there is a large interest in redesigning these materials to be inherently recyclable so that energy intensive production of fibers and monomers can be circumvented, bolstering composite manufacture supply chains. Polyester covalent adaptable networks (PECANs) are one such promising alternative to the incumbent, nonrecyclable epoxy-amine thermosets. PECANs can be formed from the ring-opening co-polymerization (ROCOP) of epoxy-anhydride monomer mixtures and subsequent curing at mild temperatures to exhibit similar performance to conventional epoxies while also possessing unique dynamic chemistries along the ester-hydroxyl backbone that are capable of transesterification and thus reprocessability. While significant advancements have been made in formulating these materials for improved mechanical properties or optimizing solvolysis and reprocessing strategies, less attention has been placed on the impact of the residing amine catalyst used to generate the polyester network. In this work, we evaluated the triple-catalytic efficacy of 12 tertiary amines that act as a curing (bulk ROCOP), a transesterification (internal bond exchange), and a deconstruction (methanolysis) catalyst for PECAN thermosets. Specifically, we first distinguish between chain-growth and step-growth polymerization mechanisms for epoxy-amine and epoxy-anhydride mechanisms. We also utilized density functional theory (DFT) to estimate the basicity (pKb) of each catalyst. Of the tested catalysts, the ROCOP of the studied PECAN network can be completed between 95 and 247 min (at 80 degrees C), with variable gelation phenomena. Additionally, the stress relaxation (transesterification metric) efficiency of the tested PECAN networks with alternative embedded catalysts ranged from 95% to 15% reduction in stress after 5 h at 200 degrees C, and the depolymerization efficacy ranged from 2.5% to 9.8% deconstruction after 36 h at 130 degrees C. Overall, the nitrogen-based moieties were demonstrated to influence polymerization kinetics, catalyze the dynamic transesterification exchange mechanism, and aid in the solvolysis of the thermosets at end-of-life.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Chemical Transformation of Cat Cracking Light Gas Oil Components by Hydrofining on Aluminum-Cobalt-Molybdenum Catalysts

The degree of hydrogenation of various classes of aromatic and olefin hydrocarbons in the cat cracking light gas oil hydrofining process in the presence of Al-Co-Mo and Al-Ni-W catalysts is studied. The Al-Ni-W catalyst exhibits much greater hydrogenation activity with respect to aromatic hydrocarbons than the Al-Co-Mo catalyst. However, the Al-Co-Mo catalyst exhibits much greater hydrogenation activity with respect to olefin hydrocarbons than the Al-Ni-W catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Theoretical and Experimental Studies of CoGa Catalysts for the Hydrogenation of CO 2 to Methanol

We report methanol is an important chemical compound which is used both as a fuel and as a platform molecule in chemical production. Synthesizing methanol, as well as dimethyl ether, directly from carbon dioxide and hydrogen produced using renewable electricity would be a major step forward in enabling an environmentally sustainable economy. We utilize density functional theory combined with microkinetic modeling to understand the methanol synthesis reaction mechanism on a model CoGa catalyst. A series of catalysts with varying Ga content are synthesized and experimentally tested for catalytic performance. The performance of these catalysts is sensitive to the Co:Ga ratio, whereby increased Ga content results in increased methanol and dimethyl ether selectivity and increased Co content results in increased selectivity towards methane. We find that the most active catalysts have up to 95% CO-free selectivity towards methanol and dimethyl ether during CO 2 hydrogenation and are comparable in performance to a commercial CuZn catalyst. Finally, using in situ DRIFTS we experimentally verify the presence of a surface formate intermediate during CO 2 hydrogenation in support of our theoretical calculations.

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

Production of Gaseous Olefins from Syngas over a Cobalt-HZSM-5 Catalyst

Light olefins (C2–C5) are high-value platform chemicals used to produce plastics, lubricants, coating material, and surfactants, and can be intermediates to produce transportation fuels. In this study we report on the development of a Co-based catalyst for direct conversion of fossil as well as biomass derived syngas into light olefins that enables high conversion and olefin/paraffin (O/P) product ratio, minimal selectivity to CO2 (<?1%) and wax formation (C14+ selectivity?<?1%). Over a Co/HZSM-5 bi-functional catalyst 38% CO conversion with C2–C5 olefin selectivity of 48%, and O/P ratio of 4.0 was achieved at 240 °C, 17 bar, and 1.5 L/(g–h). In addition to a gaseous olefin-rich stream a C6–C13 mixed olefin/paraffin liquid byproduct was also produced with 25% selectivity. Both Co loading and the HZSM-5 acidity levels were optimized to maintain the balance between the hydrogenation and the cracking activity to generate high levels of C2–C4 olefins. A suite of catalyst characterization tools were used to correlate the physical and chemical property of the catalyst to the performance of the catalyst towards syngas conversion and C2–C4 olefin selectivity.

Maddi, Balakrishna↗
DOE OSTI2015

Replacing precious metals with carbide catalysts for hydrogenation reactions

Molybdenum carbide (Mo₂C and Ni/Mo₂C) catalysts were compared with Pd/SiO₂ for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO₂, Mo₂C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo₂C could be completely regenerated by H₂ treatment at 723 K for the three molecules. The Ni modified Mo₂C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Ni modified Mo₂C catalysts, 8.6%Ni/Mo₂C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO₂. Compared to Pd/SiO₂, both Mo₂C and Ni/Mo₂C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.

1,3-Buatdiene↗