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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

In situ Formation of Platinum-Carbon Catalysts in Propane Dehydrogenation

The catalytic production of propylene via propane dehydrogenation (PDH) is a key reaction in the chemical industry. By combining operando transmission electron microscopy with density functional theory analysis, we show that the intercalation and ordering of carbon on Pt interstitials to form Pt-C solid solutions is relevant for increasing propylene production. More specifically, we found that at the point of enhanced propylene formation, the structure of platinum nanoparticles is transformed into a transient caesium chloride-type Pt-C polymorph. At more elevated temperatures, the zincblende and rock salt polymorphs seemingly coexist. When propylene production was highest, multiple crystal structures consisting of Pt and carbon were occasionally found to coexist in one individual nanoparticle, distorting the Pt lattice. Catalyst coking was detected at all stages of the reaction, but did initially not affect all particles. These findings could lead to the development of novel synthesis strategies towards tailoring highly efficient PDH catalysts.

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

Propane Dehydrogenation on Single-Site [PtZn4] Intermetallic Catalysts

Propane dehydrogenation (PDH) is a commercial propylene production technology that has received much attention, but high reaction temperature results in decrease of propylene selectivity and catalyst stability. This paper describes a single-site [PtZn 4 ] catalyst by assembling atomically ordered intermetallic alloy (IMA) as a selective and ultrastable PDH catalyst. The catalyst enables more than 95% propylene selectivity from 520 to 620 oC. No obvious deactivation is observed within 160-hours test, superior to PtSn/Al 2 O 3 and state-of-the-art Pt-based catalysts. Additionally, based on in situ X-ray absorption fine-structure, X-ray photoelectron spectroscopy measurements and density functional theory calculations, we reveal that the surface [PtZn 4 ] ensembles in PtZn IMAs serve as the key active site structures, wherein the geometry-isolated and electron-rich Pt1 site in [PtZn 4 ] ensembles readily promotes the first and second C–H cleavage of propane, but inhibits further dehydrogenation of surface-bounded propylene. This significantly improves the selectivity and stability by prohibiting coke side reactions.

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

Integrated Approach to CO 2 Capture and Conversion to Cyclic Carbonates under Solvent- and Additive-Free Conditions Utilizing the CO 2 Capture Solvent EEMPA

An integrated CO 2 capture and conversion to materials (IC 3 M) implementation utilizing a CO 2 capture solvent is an efficient approach to reduce the amount of CO 2 in the atmosphere while producing value-added chemicals. In this work, we demonstrate that the advanced water-lean CO 2 capture solvent, N-(2-Ethoxyethyl)-3-morpholinopropan-1-amine (EEMPA), can catalyze the cycloaddition reaction between CO 2 and propylene oxide to produce the value-added chemical propylene carbonate in an IC 3 M fashion. When excess propylene oxide is used relative to EEMPA, yields as high as 75% with 85% selectivity toward propylene carbonate can be achieved under solvent-free conditions without the need of additives/cocatalysts. The reaction temperature (120 °C) is comparable to that used in the thermal regeneration of the capture solvent under industrial conditions. Formation of an undesired amino alcohol side product was observed, but it may be reversible or avoidable with continued research despite the unsuccessful initial attempts. Finally, we show that this can be applied to other epoxides for the production of various cyclic carbonates.

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

Tuning Metal–Organic Framework (MOF) Topology by Regulating Ligand and Secondary Building Unit (SBU) Geometry: Structures Built on 8-Connected M 6 (M = Zr, Y) Clusters and a Flexible Tetracarboxylate for Propane-Selective Propane/Propylene Separation

Topology evolution originating from variations of linker and SBU (Secondary Building Unit) geometries could largely enrich the chemistry of metal–organic frameworks (MOFs). Here we report the synthesis and characterization of three MOF structures built on the same organic linker, N,N,N',N'-Tetrakis(4-carboxyphenyl)-1,4-phenylenediamine (tcppda) and similar 8-connected M 6 (M = Zr or Y) clusters. The three compounds, HIAM-402, HIAM-403, and HIAM-311, feature 4,8-connected sqc, scu, and flu topology, respectively. Detailed structural analysis revealed that different geometries of the inorganic M 6 SBUs as well as the organic linker have led to the formation of distinct MOF nets. In particular, HIAM-402 features exceptional framework stability and high porosity and acts as a propane-selective adsorbent for the discrimination of propane and propylene. Its balanced adsorption selectivity (S propane/propylene = 1.43) and capacity (Q propane = 133.3 cm 3 /g, 298 K and 1 bar) endow it with the capability of separating propane and propylene mixtures and one-step production of highly pure propylene (purity >99.9%), as validated by column breakthrough measurements, with the presence of moisture or propyne. As a result, ab initio calculations further confirm that the propane-selective behavior of HIAM-402 is a result of its higher binding energy toward propane compared to that of propylene.

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

An experimental and computational view of the photoionization of diol–water clusters

In the interstellar medium, diols and other prebiotic molecules adsorb onto icy mantles surrounding dust grains. Water in the ice may affect the reactivity and photoionization of these diols. Ethylene glycol (EG), 1,2-propylene glycol, and 1,3-propylene glycol clusters with water clusters were used as a proxy to study these interactions. The diol–water clusters were generated in a continuous supersonic molecular beam, photoionized by synchrotron-based vacuum ultraviolet light from the Advanced Light Source, and subsequently detected by reflectron time-of-flight mass spectrometry. The appearance energies for the detected clusters were determined from the mass spectra, collected at increasing photon energy. Clusters of both diol fragments and unfragmented diols with water were detected. The lowest energy geometry optimized conformers for the observed EG–water clusters and EG fragment–water clusters have been visualized using density functional theory (DFT), providing insight into hydrogen bonding networks and how these affect fragmentation and appearance energy. As the number of water molecules clustered around EG fragments (m/z 31 and 32) increased, the appearance energy for the cluster decreased, indicating a stabilization by water. This trend was supported by DFT calculations. Fragment clusters from 1,2-propylene glycol exhibited a similar trend, but with a smaller energy decrease, and no trend was observed from 1,3-propylene glycol. In conclusion, we discuss and suggest that the reactivity and photoionization of diols in the presence of water depend on the size of the diol, the location of the hydroxyl group, and the number of waters clustered around the diol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Techno-economic analysis and life cycle assessment for the catalytic hydrogenolysis and hydrocracking of polyethylene

Catalytic hydrogenolysis and hydrocracking are promising technologies for the conversion of polyolefin waste into hydrocarbons. Here, to explore the economic and environmental viability of these approaches, we conducted techno-economic analysis and life cycle assessment of polyethylene hydrogenolysis and hydrocracking processes that produce fuel-range products or olefins, respectively. Relative to primary production, the minimum selling price (MSP) of alkanes for linear-chain naphtha was estimated to be 1.8-fold higher, whereas branched-chain naphtha and propylene were shown to be cost competitive. Environmental impacts showed similar trends across scenarios, with propylene production by hydrocracking exhibiting greenhouse gas emissions comparable with conventional propylene due to relatively low hydrogen demand and high yield. Together, these results suggest that innovations in catalysis and reaction engineering will be required to make viable products that are scale matched with today's plastics, such as light olefins for closed-loop recycling.

09 BIOMASS FUELS↗
DOE OSTI2022

Mechanistic Investigations of Gas-Phase Catalytic Hydrogenation in Metal–Organic Frameworks: Cooperative Activity of the Metal and Linker Sites in Cu x Rh 3– x (BTC) 2

We report the Cu x Rh 3–x (BTC) 2 catalyst (abbreviated CuRhBTC, BTC 3– = benzene tricarboxylate) provides excellent dispersion of active metal sites coupled with well-defined, robust structures for propylene hydrogenation reactions. This material therefore serves as a unique prototype for understanding catalytic activity in metal organic frameworks (MOFs). The mechanism of gas-phase hydrogenation at the bimetallic metal nodes of a MOF has been investigated in detail for the first time using in situ spectroscopy and diffraction experiments combined with density functional theory (DFT) calculations. The reaction occurs via a cooperative process in which the metal and linker sites play complementary roles; specifically, H 2 is dissociated at a Rh 2+ site with a missing Rh–O bond, while protonation of the decoordinated carboxylate linker stabilizes the active sites and promotes H 2 dissociation. In situ X-ray diffraction experiments show that the crystalline structure of the MOF is retained under reaction conditions at 20–100 °C. In situ Raman spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments demonstrate that propylene adsorbs at both Rh 2+ and Cu 2+ sites via π bonding. Cu 2+ is catalytically inactive, but at Rh 2+ sites, a propyl intermediate is observed when H 2 is introduced into the propylene feed. Furthermore, the appearance of the O–H stretch of COOH at ~3690 cm –1 in the DRIFT spectra is characteristic of defects consisting of missing Rh–O bonds. These experimental results are in general agreement with a reaction mechanism proposed by DFT, in which the decoordinated carboxylate linker is protonated, and the active Rh 2+ site remains available for readsorption of reactants in the subsequent catalytic cycle.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Adaptive Pore Opening to Form Tailored Adsorption Sites in a Cooperatively Flexible Framework Enables Record Inverse Propane/Propylene Separation

A proposed low-energy alternative to the separation of alkanes from alkenes by energy-intensive cryogenic distillation is separation by porous adsorbents. Unfortunately, most adsorbents preferentially take up the desired, high-value major component alkene, requiring frequent regeneration. Adsorbents with inverse selectivity for the minor component alkane would enable the direct production of purified, reagent-grade alkene, greatly reducing global energy consumption. However, such materials are exceedingly rare, especially for propane/propylene separation. Here, we report that through adaptive and spontaneous pore size and shape adaptation to optimize an ensemble of weak noncovalent interactions, the structurally responsive metal-organic framework CdIF-13 (sod-Cd(benzimidazolate) 2 ) exhibits inverse selectivity for propane over propylene with record-setting separation performance under industrially relevant temperature, pressure, and mixture conditions. Powder synchrotron X-ray diffraction measurements combined with first-principles calculations yield atomic-scale insight and reveal the induced fit mechanism of adsorbate-specific pore adaptation and ensemble interactions between ligands and adsorbates. Dynamic column breakthrough measurements confirm that CdIF-13 displays selectivity under mixed-component conditions of varying ratios, with a record measured selectivity factor of α ≈ 3 at 95:5 propylene:propane at 298 K and 1 bar. When sequenced with a low-cost rigid adsorbent, we demonstrated the direct purification of propylene under ambient conditions. In conclusion, this combined atomic-level structural characterization and performance testing firmly establishes how cooperatively flexible materials can be capable of unprecedented separation factors.

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

Low-temperature (< 200 °C) degradation of electronic nicotine delivery system liquids generates toxic aldehydes

Electronic cigarette usage has spiked in popularity over recent years. The enhanced prevalence has consequently resulted in new health concerns associated with the use of these devices. Degradation of the liquids used in vaping have been identified as a concern due to the presence of toxic compounds such as aldehydes in the aerosols. Typically, such thermochemical conversions are reported to occur between 300 and 400 °C. Herein, the low-temperature thermal degradation of propylene glycol and glycerol constituents of e-cigarette vapors are explored for the first time by natural abundance 13 C NMR and 1 H NMR, enabling in situ detection of intact molecules from decomposition. The results demonstrate that the degradation of electronic nicotine delivery system (ENDS) liquids is strongly reliant upon the oxygen availability, both in the presence and absence of a material surface. When oxygen is available, propylene glycol and glycerol readily decompose at temperatures between 133 and 175 °C over an extended time period. Among the generated chemical species, formic and acrylic acids are observed which can negatively affect the kidneys and lungs of those who inhale the toxin during ENDS vapor inhalation. Further, the formation of hemi- and formal acetals is noted from both glycerol and propylene glycol, signifying the generation of both formaldehyde and acetaldehyde, highly toxic compounds, which, as a biocide, can lead to numerous health ailments. The results also reveal a retardation in decomposition rate when material surfaces are prevalent with no directly observed unique surface spectator or intermediate species as well as potentially slower conversions in mixtures of the two components. The generation of toxic species in ENDS liquids at low temperatures highlights the dangers of low-temperature ENDS use.

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

Olefin metathesis over supported MoO x catalysts: influence of the oxide support

Here, a series of supported MoO x catalysts on different oxide supports (Al2O3, TiO2, ZrO2, SiO2) were synthesized and investigated for propylene metathesis, characterized with in situ spectroscopies (DRIFTS, Raman, UV-vis) and chemically probed with propylene-TPSR-MS, propylene-TPSR-IR, and ethylene/2-butene titration. Under dehydrated conditions at monolayer coverage or maximum surface dispersion, the surface MoO x sites are present as a mixture of isolated di-oxo (O=) 2 Mo(–O–Al) 2 and oligomeric mono-oxo O=Mo(–O–Al) 4/5 sites on Al 2 O 3 , primarily oligomeric mono-oxo O=Mo(–O–Ti) 4/5 on TiO 2 , isolated di-oxo (O=) 2 Mo(–O–Zr) 2 and oligomeric mono-oxo O=Mo(–O–Zr) 4/5 on ZrO 2 , and isolated di-oxo (O=) 2 Mo(–O–Si) 2 on SiO 2 . The bridged (S 2 -OH) and tri-coordinated (S 3 -OH) anchoring surface hydroxyls of the oxide supports with strong support cation electronegativity control the activation and number of active surface MoO x sites at low temperatures (<100 °C). The isolated anchoring surface hydroxyls (S-OH) of the oxide supports with strong support cation electronegativity control the activation and number of active surface MoO x sites at high temperatures (>350 °C). Olefin metathesis by the more redox active supported MoO x /TiO 2 and MoO x /ZrO 2 catalysts is retarded by the formation of stable surface acetone and acetate species that block olefin adsorption. The oxide supports are potent ligands that tune the activation and surface chemistry of the surface MoOx sites for olefin metathesis. This is the first time that the influence of oxide supports on the activation and surface chemistry of supported MoO x sites has been systematically examined.

02 PETROLEUM↗
DOE OSTI2024

Nonoxidative dehydrogenation of propane using boron-incorporated silica-supported Pt Sites synthesized by atomic layer deposition

Nonoxidative dehydrogenation of propane to propylene using Pt-based supported catalysts is an active research area in catalysis because catalyst attributes of Pt sites can be controlled by careful design of active sites. One way to achieve this is by the addition of a second metal that may impart a change in the electron density of active sites, which in turn affects catalytic performance. In this study, bimetallic Pt and B sites were deposited on powder SiO2 using atomic layer deposition (ALD). Boron was first deposited on SiO2 via half-cycle ALD using triisoproplyborate as the B source. Following calcination, Pt deposition was performed via half-cycle ALD using trimethyl(methylcyclopentadienyl)platinum(IV) as the Pt source. The synthesized catalysts were reduced under H2 at 550 °C and characterized using inductively coupled plasma optical emission spectroscopy for elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO to examine the properties of Pt, and time-resolved X-ray absorption near edge structure spectroscopy to examine the changes in the reducibility of Pt sites. The samples were then tested for nonoxidative dehydrogenation of propane at 550 °C using a fixed-bed plug-flow reactor to examine the role of B on the catalytic performance. Characterization results showed that the addition of B imparted an increase in electron density and affected the reducibility of Pt sites. In addition, incorporating B on SiO2 created anchoring sites for Pt ALD. The amount of Pt deposited on B/SiO2 was 2.2 times that on SiO2. Catalytic activity results revealed the addition of B did not change the initial activity of Pt sites significantly, but improved propylene selectivity from 80% to 87% and stability almost threefold. The enhanced selectivity and stability of PtB/SiO2 is most presumably due to favored desorption of propylene and mitigating coke formation under reaction conditions, respectively.

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

Comparison of direct and CO 2 -oxidative dehydrogenation of propane

Propane dehydrogenation to propylene has received increasing attention due to the fast growth in propylene demand and the exploration of shale gas containing propane. Direct dehydrogenation of propane (DDHP) offers high propylene selectivity but is limited by quick deactivation due to coke formation. CO 2 -assisted oxidative dehydrogenation of propane (CO 2 -ODHP) can consume CO 2 and meanwhile reduce coke deposition via the reverse Boudouard reaction. Here in the current review, direct and CO 2 -assisted dehydrogenation of propane has been compared from three aspects: reaction mechanisms, catalyst compositions, and CO 2 footprint analysis. As the average CO 2 emissions from electricity generation decrease due to the utilization of renewable energy, CO 2 -ODHP potentially leads to a net-negative CO 2 footprint while DDHP cannot.

58 GEOSCIENCES↗
DOE OSTI2024

Direct Conversion of CO 2 to Olefins over a Cr 2 O 3 /ZSM-5@CaO Cooperative and Bifunctional Material Under Isothermal Conditions

Direct conversion of point-source CO 2 into fine chemicals over cooperative and bifunctional materials (BFMs) – composed of adsorbents and catalysts – has emerged as a promising approach to improve the energy efficiency of the carbon capture and conversion processes. In this study, a bifunctional material consisting of Cr 2 O 3 /ZSM-5 catalyst and CaO adsorbent was developed and tested in the CO 2 -oxidative dehydrogenation of propane (CO 2 –ODHP) for reactive capture of CO 2 in a fixed bed reactor. First, CaO was prepared using two distinct methods: solid-state and citrate sol–gel. The citrate sol–gel method resulted in small and finely-distributed CaO particles, allowing more accessible sites for CO 2 adsorption. Consequently, a high CO 2 adsorption capacity of ~14 mmol/g was achieved with fast adsorption kinetics compared to CaO prepared by the solid-state method. The CaO adsorbent was then combined with the Cr 2 O 3 /ZSM-5 catalyst for BFM synthesis and tested in the CO 2 –ODHP process, targeting propylene production. The BFM was extensively characterized to provide insights into the BFM’s surface chemistry, morphology, and reaction mechanism in the reactive capture process of CO 2 –ODHP. The results revealed that under isothermal adsorption–reaction conditions at 600 °C, a propane conversion of 22.5%, a propylene selectivity of 55.3%, and an olefin selectivity of 67.3% were achieved. The excellent propylene selectivity was attributed to the catalyst acidity and redox property of the Cr 2 O 3 /ZSM-5 catalyst, which facilitated the reaction pathway of propane dehydrogenation in the process of CO 2 –ODHP. Overall, this study renders Cr 2 O 3 /ZSM-5@CaO as promising BFMs with high CO 2 capture capacity and catalytic activity for integrated CO 2 capture and conversion in the ODHP reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Suppressing CO x in oxidative dehydrogenation of propane with dual-atom catalysts

Oxidative dehydrogenation of propane (ODHP) is a promising route for propylene production, but achieving high selectivity towards propylene while minimizing CO x byproducts remains a significant challenge for conventional metal oxide catalysts. Here we propose a solution to this challenge by employing atomically dispersed dual-atom catalysts (M 1 M' 1 -TiO 2 DACs). Ni 1 Fe 1 -TiO 2 DACs exhibit an ultralow CO x selectivity of 5.2% at a high propane conversion of 46.1% and 520 °C, with stable performance for over 1000 hours. Mechanistic investigations reveal that these catalysts operate via a cooperative Langmuir-Hinshelwood mechanism, distinct from the Mars-van Krevelen mechanism typical of metal oxides. This cooperative pathway facilitates efficient conversion of propane and oxygen into propylene at the dual-atom interface. The superior selectivity arises from facile olefin desorption from the dual-atom sites and suppressed formation of electrophilic oxygen species, which are preferentially adsorbed on Fe 1 sites rather than oxygen vacancies. This work highlights the potential of dual-atom catalysts for highly selective ODHP and provides insights into their unique catalytic mechanism.

02 PETROLEUM↗
DOE OSTI2024

ChemPren: a new and economical technology for conversion of waste plastics to light olefins

With the ever-increasing demand for plastics, sustainable recycling methods are key necessities. Here, the current plastics industry can manage to recycle only 10% of the 400 million metric tons of plastic produced globally. Waste plastics, in the current infrastructure, land up mostly in landfills. Although a lot of research efforts have been spent on processing and recycling co-mingled mixed plastics, energy-efficient sustainable and scalable routes for plastic upcycling are still lacking. Catalytic valorization of waste plastic feedstock is one of the potential scalable routes for plastic upcycling. Silica-alumina based materials, and zeolites have shown a lot of promise. A major interest lies in restricting catalyst deactivation, and refining product selectivity and yield for such catalytic processes. This article highlights ChemPren technology as a clean energy solution to waste plastic recycling. Co-mingled, mixed plastic feedstock along with spray dried, attrition resistant, ZSM-5 containing catalysts is preprocessed with an extruder to form optimally sized particles and fed into a fluidized bed reactor for short contact times to produce selectively and in high yields ethylenes, propylenes and butylenes. This techno-economic perspective indicates that the ChemPren technology can produce propylene at $\$$0.16 per lb, whereas the current selling price of virgin propylene is $0.54 per lb. This technology can serve as a platform for mixed plastic upcycling, with more advancements necessary in the form of robust and resilient catalysts and reactor operation strategies for tuning product selectivity.

25 - ENERGY STORAGE↗
DOE OSTI2022

Molecular Design of Supported MoO x Catalysts with Surface TaO x Promotion for Olefin Metathesis

A series of supported 3% MoOx catalysts were synthesized by incipient-wetness impregnation of 5%-15% TaO x surface modified γ-Al 2 O 3 support. The catalysts were characterized by in situ spectroscopies (DRIFTS, Raman, UV-vis, XAS) and multiple chemical probes (C 2 H 4 /C 4 H 8 titration, C 3 H 6 -TPSR, steady state propylene metathesis, NH 3 -IR adsorption). The supported tantalum oxide phase was present as surface TaO x sites on the γ-Al 2 O 3 support that capped that Al 2 O 3 surface hydroxyls. The change in available surface hydroxyls caused the subsequent anchoring of MoOx species to occur at different surface hydroxyls. This shifted the anchoring of MoO x species from basic (Al-OH) to neutral (Al 2 -OH) to more acidic (Al 3 -OH) surface hydroxyls as well as perturbation of the remaining alumina surface hydroxyls by the surface TaO x sites. The TaO x surface modified γ-Al 2 O 3 support increased the number of activated surface MoO x sites (Ns) by ~6x and the TOF by ~10x resulting in an increased activity of ~60x. In conclusion, It was found that the specific anchoring surface hydroxyls rather than the extent of oligomerization of the surface MoO x sites control the number of activated MoO x sites and TOF for propylene metathesis. No relationship between the nature of the surface Lewis/Brønsted acid sites and Ns and TOF were found to be present.

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

Highly Selective Carbon-Supported Boron for Oxidative Dehydrogenation of Propane

Bulk boron materials, such as hexagonal boron nitride (h-BN), are highly selective catalysts for the oxidative dehydrogenation of propane (ODHP). Previous attempts to improve the productivity of these systems involved the immobilization of boron on silica and resulted in less selective catalysts. Here, we report that acid-treated, activated carbon-supported boron prepared via incipient wetness impregnation with boric acid (B/OAC) exhibits equal propylene selectivity and improved productivity (kg propylene kg cat -1 hr -1 ) as compared to h-BN. Characterization of the fresh and spent catalysts with infrared, Raman, X-ray photoelectron, and solid-state NMR spectroscopies reveals the presence of oxidized/hydrolyzed boron that is clustered on the surface of the support.

03 NATURAL GAS↗