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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Vacuum-assisted carbon molecular sieve membrane reactor for non-oxidative ethane dehydrogenation

Non-oxidative ethane dehydrogenation (EDH) is equilibrium-limited and endothermic. Selective hydrogen removal using a gas-permeable membrane within the EDH reaction zone can overcome the thermodynamic equilibrium, enabling higher ethane conversions. Employing vacuum as the permeation driving force, rather than a sweep gas, enhances the industrial viability of membrane reactors by eliminating additional post-reaction separation units. This study presents a membrane reactor that integrates H 2 -permeable carbon molecular sieve (CMS) hollow fiber membranes embedded in a fixed bed of cobalt in a dealuminated beta zeolite (Co@DeAl-BEA) catalyst, utilizing a vacuum to remove hydrogen efficiently. The CMS membrane exhibits high hydrogen permeance and an excellent H 2 /C 2 H 6 separation factor. The membrane reactor significantly enhanced the ethane conversion under reaction conditions comparable to those reported in the literature. A Langmuir-Hinshelwood kinetic rate expression was developed and incorporated into a one-dimensional steady-state reactor model. The experimentally validated model indicates that increasing the number of hollow fibers improves ethane conversion, although ethane loss to the permeate limits the benefit. The contact area between the catalyst and the membrane limits the reactor performance more than the catalytic throughput. Furthermore, we find that the location of the catalyst packing relative to the hollow fiber membranes influences ethane loss and conversion. Higher reactor pressures and inlet ethane flow rates improve space-time yield at the expense of lower ethane conversion. Increasing reactor temperature or packing length promotes both performance metrics. The EDH membrane reactor demonstrated durability over 200 h of continuous operation, maintaining record-low deactivation rates and high ethylene selectivity. Protocols for catalyst regeneration were developed.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Enhancement of oxidative dehydrogenation over cerium-doped nickel niobium catalysts and analysis of batch-to-batch variability

Nickel based catalysts are inexpensive and efficient for use in the oxidative dehydrogenation of ethane. NiO doped with niobium and cerium shows increased ethylene production. Small amounts of Ce doped onto a NiNb catalyst led to increased Ni activity. The catalyst that had the highest ethylene production rate per g of catalyst had 1 atom% Ce, 86 at% Ni, and 13 at% Nb (1CeNiNb) while, if surface area is incorporated into the calculation, the catalyst that had the highest ethylene production rate per m 2 was the 0.5CeNiNb catalyst. The ethylene production rates of these Ce-containing catalysts are 27 %-127 % higher than those with NiNb alone previously reported in the literature. Here, to fully understand how cerium affects the NiNb catalyst, the Ce content and effect on active sites has been fully characterized over multiple batches. In doing this, light has been shed on batch-to-batch variability. Characterization techniques such as powder X-ray diffraction, hydrogen temperature programmed reduction, X-ray photoelectron spectroscopy, synchrotron X-ray absorption spectroscopy, and methanol adsorption were used.

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

Transforming Boron Carbon Nitride: A Carbon-to-Oxygen Switch to Boost Propane Oxidative Dehydrogenation

Hexagonal boron nitride (h-BN) catalysts exhibit high alkene selectivity in the oxidative dehydrogenation of propane (ODHP). Nevertheless, the conversion-selectivity trade-off persisted primarily due to the low density of oxygen-containing boron active species, while simple and controllable modification strategies for h-BN still face challenges. Herein, we developed an in situ carbon-to-oxygen switch strategy within a tailored boron carbon nitride (BCN) framework, in which uniformly embedded B–C 3 were transformed into B–O 3 via oxidative treatment (denoted as BNO x ). The structural evolution from B–C 3 to B–O 3 was well characterized by spectroscopy and soft X-ray absorption techniques. The resulting BNO x catalysts, enriched with B–O 3 units, demonstrated performance in ODHP, achieving a propane conversion of 50.4% with 32.7% olefin yield at 500 °C. Density functional theory (DFT) calculations confirmed that B–O 3 species preferentially lower activation barriers, rendering the process thermodynamically more favorable. In conclusion, this work introduced an in situ reconstruction method for atomic-level heteroatom-engineered h-BN catalysts, opening an avenue for advanced catalyst design across energy conversion systems.

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

Propane Dehydrogenation Catalyzed by Supported Group IV (Ti, Zr, Hf) Organometallics on Silicon Nitride

Mesoporous silicon nitride (Si 3 N 4 ) enables access to chemisorbed group IV organometallics catalysts active for propane dehydrogenation (PDH) compared to the organometallic analogues on mesoporous silica under the same reaction conditions. The series of Si 3 N 4 -supported materials are active catalysts, (Zr > Hf > Ti k f = 290, 232, and 162 mol mol Metal -1 h -1 at 450 °C with 2% C 3 H 8 in Ar, respectively) with selectivity above 95%, demonstrating additional examples of Ti and Hf systems for PDH. However, the underlying mechanism of the improved performance relative to oxide supported homologues is not well-understood. Characterization of thermally treated samples (DRIFTS, XAS and SSNMR) and computational modeling of this catalyst series was utilized to differentiate between potential amido - (C-H activation along the M-N bond) and imido - (C-H activation along the M=N bond) mechanisms. Due to remaining mechanistic ambiguity, a Ga analogue was synthesized and evaluated for PDH activity as an indirect probe to experimentally differentiate pathways. An inversion of the oxide/nitride performance trend is observed for the Ga congener which does not form a Ga=N bond, most consistent with different mechanisms dictating the performance of the group IV/Si 3 N 4 catalysts vs Ga/Si 3 N 4 .

heterolytic cleavage↗
DOE OSTI2025

Investigation of Solid Particle Reactors for Nonoxidative Dehydrogenation of Ethane: Toward Solar Thermal Ethylene Production

Concentrating solar power plants can generate renewable heat at temperatures well above those of most industrial processes. Ceramic particles irradiated with concentrated sunlight can store high-quality sensible heat and transfer this to power generation systems. These concepts and materials hold great potential to also enable thermal processes in the chemical industry, but effective strategies for transferring heat from thermal energy storage media into chemical reactors are still under development. This present work evaluated the thermal and chemical compatibility of various solid particle media (including quartz, bauxite, and alumina particles) integrated directly into tube reactors and the subsequent effects on reactor performance for the nonoxidative dehydrogenation of ethane reaction. Empty tube reactors without loaded particles (representing conventional ethane cracking coils) showed significant heat transfer limitations as the tube diameter was scaled. The incorporation of media into the reactor significantly aided heat transfer to the gaseous ethane reactant and increased its conversion by as much as 10% at similar space velocities. Despite direct contact with hydrocarbon gases, alumina and quartz media showed negligible coke formation. Even during reaction in 100% ethane feed gas at 825 °C, the average selectivity of the coke product was only 0.57% when using the quartz media. These materials further demonstrated excellent thermal stability during subsequent reoxidation in air at 800 °C, which simulated the reheating of particles in a circulating particle solar receiver. Conversely, high rates of coke formation, with a product selectivity of 27.5%, were observed on sintered bauxite particles during the reaction, likely promoted by transition metal constituents. These particles fractured upon reoxidation due to exotherms generated from coke combustion. In conclusion, while the use of cofed steam could mitigate attrition of redox-active particles, the ability of inert metal oxide particles to efficiently transfer heat to concentrated ethane reactant gas while suppressing side reactions or degradation suggests that these media could effectively couple solar thermal plants to reactors for next-generation production of ethylene and other critical chemicals.

Hydrocarbons↗
DOE OSTI2025

Oxidative Dehydrogenation of N ‐Heteroaromatic Alkyl Alcohols and Amines Facilitated by Dearomative Tautomerization

The oxidation of alcohols, amines, and halides is a fundamental transformation in organic chemistry with significant applications in the synthesis of fine chemicals, pharmaceuticals, and natural products. Here we show that a broad variety of N-heteroarenes bearing hydroxymethyl, aminomethyl, or halomethyl groups are oxidatively dehydrogenated to their respective aldehydes by simply heating them in acidic or basic aqueous solution under ambient atmosphere. The quantitative oxidation of 9-acridinemethanol to 9-acridinecarboxaldehyde serves as an illustrative example, proceeding to completion within 3 hours in refluxing 5% aqueous acetic acid or even household vinegar. Quinoline derivatives may be similarly oxidized but require higher temperatures and longer reaction times, while indole derivatives are oxidized under basic conditions. Based on comprehensive regioselectivity screens, internal kinetic isotope competition, and density functional theory (DFT) calculations, we propose a mechanism in which migration of a methylene hydrogen to the pyridinic nitrogen by acid-catalyzed dearomative tautomerization yields an unstable enol or enamine intermediate that then irreversibly loses two hydrogen atoms to atmospheric oxygen. In addition to the simplicity and environmentally benign nature of our method, we observe no indication of any over-oxidation to carboxylic acids. Finally, we demonstrate the synthetic utility of this reaction through two different one-pot formylations of acridine.

Chemistry↗
DOE OSTI2024

Molten‐Salt‐Mediated Chemical Looping Oxidative Dehydrogenation of Ethane with In‐Situ Carbon Capture and Utilization

Abstract The molten‐salt‐mediated oxidative dehydrogenation (MM‐ODH) of ethane (C 2 H 6 ) via a chemical looping scheme represents an effective carbon capture and utilization (CCU) method for the valorization of ethane‐rich shale gas and concurrent mitigation of carbon dioxide (CO 2 ) emissions. Here, stepwise experimentation with Li 2 CO 3 ‐Na 2 CO 3 ‐K 2 CO 3 (LNK) ternary salts (i) assessed how each component of the LNK mixture impacted ethane MM‐ODH performance and (ii) explored physicochemical and thermodynamic mechanisms behind melt‐induced changes to ethylene (C 2 H 4 ) and carbon monoxide (CO) yields. Of fifteen screened LNK compositions, nine exhibited ethylene yields greater than 50 % at 800 °C while maintaining C 2 H 4 selectivities of 85 % or higher. LNK salts rich in Li 2 CO 3 content yielded more ethylene and CO on average than their counterparts, and net CO 2 capture per cycle reached a maximum of ~75 %. Extended MM‐ODH cycling also demonstrated long‐term stability of a high‐performing LNK medium. Density functional theory (DFT) calculations andab initiomolecular dynamics (AIMD) simulations suggested that the molten salt does not directly activate C 2 H 6 . Meanwhile, an empirical model informed by experimental data and reaction thermodynamics adequately predicted overall MM‐ODH performance from LNK composition and provided insights into the system′s primary drivers.

Chemistry↗
DOE OSTI2025

The Role of Surface Hydroxyls in Dehydration and Dehydrogenation of Formic Acid on Fe 3 O 4 (001)

Understanding the role of surface structure and hydroxylation in catalytic reactions on metal oxide surfaces is important for developing a mechanistic insight into the complex interface processes. Here, we investigate the reactivity of formic acid on reconstructed Fe 3 O 4 (001) using a combination of X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, temperature-programmed reaction spectroscopy, low energy electron diffraction, and electronic structure calculations. We find that formic acid initially dissociates at low temperatures (< 80 K) into bidentate formate and a hydroxyl up to an initial dosed coverage of two HCOOH per Fe 3 O 4 (001) unit cell. At higher temperatures (> 450 K), formate largely decomposes along the dehydration pathway, producing CO and H 2 O, with dehydrogenation to CO 2 being a minority side reaction. As a first step, water formation leads to surface oxygen extraction via the Mars-van Krevelen mechanism. Computational studies reveal formate embedded in oxygen vacancies as a key intermediate in the CO formation mechanism. CO formation proceeds via two reaction pathways with desorption that peaks at 530 K on the hydroxyl-rich surface and 560 K on the hydroxyl-deficient surface. Atomic hydrogen coadsorption experiments and ab initio calculations reveal that the presence of surface hydroxyls reduces the CO formation barrier. Furthermore, these results highlight the complex interactions between substrate and intermediate species occurring during reactions on metal oxide surfaces.

Adsorption↗
DOE OSTI2025

Modeling Oxidative Dehydrogenation of Propane with Supported Vanadia Catalysts Using Multireference Methods

The oxidative dehydrogenation of propane over supported vanadium oxide catalysts poses significant computational challenges due to complex electronic structure changes along the reaction coordinate, driven primarily by changes in the oxidation states of vanadium. To address these challenges, we systematically test quantum chemical methods, including multireference (MR) approaches, domain-based local pair natural orbital coupled cluster theory (DLPNO-CCSD(T)), and density functional theory (DFT). The initial C–H bond-breaking transition state requires MR treatment due to its multireference character, while subsequent steps permit efficient single-reference calculations. For the rate-limiting C–H activation step mediated by the vanadyl moiety, complete 1 active space second-order perturbation theory (CASPT2) yields an apparent activation barrier (E app 600K ) of 138 kJ/mol, consistent with experimental values (134 ± 4 kJ/mol; Gruene et al. Catal. Today 2010, 157, 137). In contrast, DLPNO-CCSD(T) overestimates this barrier (198 kJ/mol), whereas DFT predictions span 125–150 kJ/mol, depending on the functional. Our multireference investigation of this transition metal oxide-catalyzed process demonstrates that an active space that incorporates the C–H σ and V=O σ/π bonding orbitals, oxygen lone pairs, and their antibonding counterparts adequately captures electronic structure changes along the chemical transformation. Furthermore, these findings provide a general strategy for active space selection in transition metal oxide-catalyzed C/O–H bond activation reactions. The reference dataset from this work, which includes MR calculations with manually selected active spaces for all intermediates and transition states in the propane ODH reaction network, will serve as a benchmark for automating active space selection in similar systems.

Catalysts↗
DOE OSTI2025

Dehydrogenation vs Apparent Hydrogenation: Unraveling the Mechanisms of He and O 2 Plasma Etching on Colloidal Nanocrystal Films

Removing organic ligands from colloidal nanoparticles is critical for fabricating solid-state devices, yet accurately quantifying this removal remains a significant analytical challenge. Here, we establish a robust and accessible method for this quantification by calibrating Raman spectroscopy against precise ion beam analysis (IBA) for nanoparticle assemblies (CNAs) processed by helium (He) and oxygen (O 2 ) plasmas. We demonstrate that the calibration curves are remarkably independent of plasma power and pressure, depending critically only on the choice of feed gas. He plasma induces rapid dehydrogenation and cross-linking, evidenced by a much faster decrease in the C–H Raman signal relative to the actual carbon loss. Conversely, O 2 plasma leads to a surprising “apparent hydrogenation”, where the carbon backbone is removed significantly faster than the C–H signal diminishes. This counterintuitive effect is explained by a serial mechanism of oxidative fragmentation; β-scission cleaves the alkyl chains, and subsequent stabilization steps enrich the remaining film with hydrogen-rich methyl-terminated fragments, while carbon is efficiently removed as volatile CO. This work provides calibrated functions that enable the rapid determination of absolute carbon content in processed CNAs using simple Raman spectroscopy with uncertainties of ∼8% for O 2 and ∼12% for He plasma, offering a vital tool for both process diagnostics and fundamental studies of plasma–matter interactions in colloidal nanocrystal films.

Animal feed↗
DOE OSTI2025

Preventing Loss of Selectivity during the Oxidative Dehydrogenation of Propane over Supported Vanadium Catalysts

Supported vanadium materials are promising catalysts for the oxidative dehydrogenation of propane to propylene (ODHP), but a lack of mechanistic understanding limits the rational design of catalysts with improved propylene selectivity. Adding Ta to V/SiO 2 increases the propylene selectivity, as well as the activity, leading to superior performance compared to state-of-the-art boron-based systems. In this contribution, we utilize this surprising promotional effect of Ta to elucidate key elements of the mechanistic cycle. Through a combination of characterization techniques, computational modeling, and kinetic experiments, we show that the catalytic cycle over V/SiO 2 likely involves the formation of an isopropyl alcohol intermediate, the fate of which is in kinetic competition between subsequent dehydration to propylene or further oxidation. Furthermore, we show that the relatively facile propylene overoxidation observed for these materials occurs via the epoxidation of propylene by a proposed peroxovanadium intermediate, rather than the abstraction of propylene’s allylic C–H bond as previously assumed. Using these key mechanistic features, we rationalize the enhanced selectivity and activity of Ta promotion. In conclusion, our mechanistic framework offers avenues for future catalyst development to improve supported vanadium materials for ODHP.

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

Effects of Cofeeding Hydrogen on Propane Dehydrogenation Catalyzed by Isolated Iron Sites Incorporated into Dealuminated BEA

Iron sites dispersed on nonacidic siliceous supports have been reported to be catalytically active for propane dehydrogenation (PDH), yet the precise relationship between site structure and catalytic activity remains elusive. Here, this study provides a comprehensive understanding of the catalytic performance of iron supported on dealuminated BEA (DeAlBEA) zeolites for PDH. Using XAS, UV-vis, and IR spectroscopy of adsorbed pyridine and deuterated acetonitrile, it was found that, at an Fe/Al 0 of 0.04, isolated Fe sites form. These isolated sites exhibit a forward rate of PDH of 213 mol propene/mol Fe·h at 823 K and a feed containing 15 kPa propane. When 15 kPa of H 2 is added to the feed, the forward rate of PDH rises to 391 mol of propene/mol of Fe·h. In both cases, the propene selectivity is over 99%. IR spectroscopy of d 3 -acetonitrile suggests that the open Lewis acid site ((-Si-O-) 2 Fe 3+ -OH) serves as the active site responsible for PDH, while Brønsted acid sites (≡Fe 3+ -O(H)-Si≡) contribute to propane cracking with increasing Fe/Al 0 ratios. Kinetic analysis of the effects of H 2 addition to the propane feed on PDH kinetics shows that H 2 enhances the activity of 0.04FeDeAlBEA primarily by enhancing the strength of the propane adsorption.

Alghannam, Afnan [University of California, Berkel↗
DOE OSTI2025

Photocatalytic Methanol Dehydrogenation with Switchable Selectivity

Switchable selectivity achieved by altering reaction conditions within the same photocatalytic system offers great advantages for sustainable chemical transformations and renewable energy conversion. In this study, we investigate an efficient photocatalytic methanol dehydrogenation with controlled selectivity by varying the concentration of nickel cocatalyst, using zinc indium sulfide nanocrystals as a semiconductor photocatalyst, which enables the production of either formaldehyde or ethylene glycol with high selectivity. Control experiments revealed that formaldehyde is initially generated and can either serve as a terminal product or intermediate in producing ethylene glycol, depending on the nickel concentration in the solution. Mechanistic studies suggest a unique role of ionic nickel as an additional photoelectron competitor that can significantly influence selectivity, alongside its well-established function as a hydrogen evolution reaction cocatalyst under photocatalytic conditions. The demonstrated switchable selectivity provides a new tool for producing diverse products from methanol, while advancing the understanding of cocatalyst behavior for versatile catalytic performance.

Luo, Jie↗
DOE OSTI2025

Enabling Ethanol Dehydrogenation Catalysis by Postsynthetic Anion Exchange of Triazolate-Based Metal–Organic Frameworks

Materials containing soft, polarizable elements are expanding the boundaries of catalytic properties, offering unique electronic communication and stability characteristics compared with their harder counterparts due to the enhanced covalent nature of metal–ligand interactions. However, integrating soft components like sulfur into metal–organic frameworks (MOFs) for catalytic applications remains a largely underexplored challenge. Here, we report the synthesis of a family of triazole-based MOFs and expand upon established postsynthetic anion exchange methods to incorporate sterically encumbered polarizable elements, such as alkyl thiolates. Single-crystal X-ray diffraction, coupled with elemental analysis, confirms the successful anion exchange within M 2 X 2 BBTA (M = Co, Ni; X = μ-Cl, μ-OH, μ-SH, μ-SMe, μ-SEt; H 2 BBTA = 1H,5H-benzo(1,2-d:4,5-d′)bistriazole). We found that the anion identity significantly impacts the catalytic activity and selectivity of the MOFs, especially in nonoxidative ethanol dehydrogenation. Temperature-programmed experiments indicated that the metal single sites act as catalytically active sites below 250 °C. This work not only expands the synthetic toolbox for incorporating polarizable components into MOFs but also provides critical insights into their catalytic potential.

Anions↗
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 OSTI2025

Ampere-level co-electrosynthesis of formate from CO 2 reduction paired with formaldehyde dehydrogenation reactions

Current catalysts face challenges with low formate selectivity at high current densities during the CO 2 electroreduction. Here, we showcase a versatile strategy to enhance the formate production on p-block metal-based catalysts by incorporating noble metal atoms on their surface, refining oxygen affinity, and tuning adsorption of the critical oxygen-bound *OCHO intermediate. The formate yield is observed to afford a volcano-like dependence on the *OCHO binding strength across a series of modified catalysts. The rhodium-dispersed indium oxide (Rh/In 2 O 3 ) catalyst exhibits impressive performances, achieving Faradaic efficiencies (FEs) of formate exceeding 90% across a broad current density range of 0.20 to 1.21 A cm −2 . In situ Raman spectroscopy and theoretical calculations reveal that the oxophilic Rh site facilitates *OCHO formation by optimizing its adsorption energy, placing Rh/In 2 O 3 near the volcano-shaped apex. A bipolar electrosynthesis system, coupling the CO 2 reduction at the cathode with the formaldehyde oxidative dehydrogenation at the anode, further boosts the FE of formate to nearly 190% with pure hydrogen generation under an ampere-level current density and a low cell voltage of 2.5 V in a membrane electrode assembly cell.

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

Catalytic closed-loop recycling of polyethylene-like materials produced by acceptorless dehydrogenative polymerization of bio-derived diols

Petroleum-derived polyolefins exhibit diverse properties and are the most important and largest volume class of plastics. However, polyolefins are difficult to efficiently recycle or break down and are now a persistent global contaminant. Broadly replacing polyolefins with bio-derived and degradable polyethylene-like materials is an important yet challenging endeavour towards sustainable plastics. Here, in this study, we report a solution for circular bio-based polyethylene-like materials synthesized by acceptorless dehydrogenative polymerization from linear and branched diols and their catalytic closed-loop recycling. The polymerization and depolymerization processes utilize earth-abundant manganese complexes as catalysts. These materials exhibit a wide range of mechanical properties, encompassing thermoplastics to plastomers to elastomers. The branched diols, produced through a thiol-ene click reaction, can be polymerized to plastics with significantly enhanced tensile properties, toughness and adhesive properties. These materials could be depolymerized back to monomers through hydrogenation and were separatable with a monomer recovery of up to 99%, unaffected by the presence of dyes and additives. Overall, this system establishes a route to more sustainable plastics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗