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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Sequential Ammonia and Carbon Dioxide Adsorption on Pyrolyzed Biomass to Recover Waste Stream Nutrients

Untreated fecal waste in unsewered communities and reactive nitrogen (N) loading from wastewater and urine disposal are important environmental challenges. Through pyrolysis, untreated fecal waste can be converted into amine-rich carbon dioxide (CO 2 ) sorbents, the chemisorption of which tunes the surface chemistry toward ammonia (NH 3 ) uptake. We compared the N-loading potential within amine-rich pyrolyzed human solid waste through exposure to CO 2 followed by NH 3 with the N-loading potential on carboxyl-rich, pyrolyzed oxidized wood using sequential adsorption of isotopically labeled CO 2 and NH 3 . The total N content of pyrolyzed oxidized wood exposed once to NH3 was similar to native, pyrolyzed human solid waste (3.7% compared to 4.6%). However, sorption kinetics and spectroscopic evidence revealed distinct N forms between the two materials affecting subsequent CO 2 and NH 3 uptake. Tertiary amines comprised 70% of N in pyrolyzed waste, compared to only 53% in pyrolyzed oxidized wood. The high heat of adsorption of CO 2 on pyrolyzed human solid waste (50 kJ mol-1) at low concentrations (0.05 mmol CO 2 g -1 ) was indicative of CO 2 reactivity with tertiary amines, consistent with the formation of carbamic acid (Figure S1). Conversely, after exposure to NH 3 , pyrolyzed oxidized wood chemisorbed CO 2 at much higher concentrations (0.7 mmol CO 2 g-1), pointing to primary amines as the active functional moieties. Adsorption kinetics of pyrolyzed oxidized wood revealed continued, albeit diminishing NH 3 uptake with each consecutive CO 2 treatment, averaging 5.9 mmol NH 3 g -1 for the first NH 3 exposure event, and still 3.5 and 2.9 mmol NH 3 g -1 for the second and third. Penetration of 15 NH 3 and 13 CO 2 measured by NanoSIMS reached over 7 µm deep into both materials, explaining the large NH 3 capture. The significantly lower NH 3 adsorption compared to pyrolyzed oxidized wood may be a result of potassium (K) carbonate precipitation precluding a Lewis base interaction between NH 3 and chemisorbed CO 2 , suggested by a 2-fold increase in surface K concentrations after exposure of pyrolyzed human solid waste to CO 2 +NH 3 detected by XPS.

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

Mechanisms and Energetics of CO 2 Chemisorption in Choline-Based Eutectic Solvents

Understanding the influences of proton sharing and hydrogen transfer in amine and hydroxyl functionalized eutectic solvents is important for tuning CO 2 binding as they relate to the chemisorption capacity and energetics of solvent regeneration in carbon capture. In this study, we examine how the CO 2 binding mechanism and energetics vary in eutectic solvents composed of choline-based hydrogen-bond acceptors (HBAs) with amine and hydroxyl moieties and ethylene glycol (EG), propylene glycol (PG), 1,2-butanediol (BD), and monoethanolamine (MEA)-type hydrogen-bond donors (HBDs), through absorption–desorption experiments and spectral analysis, supported with density functional theory (DFT) calculations. While the HBD-CO 2 complex is the major and the thermodynamically more favored product of absorption in all of the examined eutectic solvents, this complexation is only possible proceeding a proton transfer from HBD to the HBA in diol-based systems (EG, PG, BD). The interplay between HBA-CO 2 and HBD-CO 2 speciation is governed by the HBD concentration, basicity, and steric effects, with increased HBD-CO 2 interactions in the presence of smaller HBDs (size: BD > PG > EG). On the other hand, in MEA-based systems, CO 2 readily binds to the amine followed by a proton transfer from the amine to the HBA as confirmed by DFT calculations. In this way, the MEA-CO 2 chemisorption capacities exceeded that of the conventional amine (up to 0.93 mol of CO 2 per mol of MEA versus 0.5). Furthermore, the increase in CO 2 capacities and enhanced binding in eutectics including MEA or the more basic HBAs also resulted in regeneration temperatures of 70 to 60 °C with calculated reaction energies of −82 to −57 kJ/mol, compared to 50 °C for others with weaker binding, following CO 2 absorption at 25 °C.

absorption↗
DOE OSTI2022

The missing base molecules in atmospheric acid–base nucleation

Abstract Transformation of low-volatility gaseous precursors to new particles affects aerosol number concentration, cloud formation and hence the climate. The clustering of acid and base molecules is a major mechanism driving fast nucleation and initial growth of new particles in the atmosphere. However, the acid–base cluster composition, measured using state-of-the-art mass spectrometers, cannot explain the measured high formation rate of new particles. Here we present strong evidence for the existence of base molecules such as amines in the smallest atmospheric sulfuric acid clusters prior to their detection by mass spectrometers. We demonstrate that forming (H2SO4)1(amine)1 is the rate-limiting step in atmospheric H2SO4-amine nucleation and the uptake of (H2SO4)1(amine)1 is a major pathway for the initial growth of H2SO4 clusters. The proposed mechanism is very consistent with measured new particle formation in urban Beijing, in which dimethylamine is the key base for H2SO4 nucleation while other bases such as ammonia may contribute to the growth of larger clusters. Our findings further underline the fact that strong amines, even at low concentrations and when undetected in the smallest clusters, can be crucial to particle formation in the planetary boundary layer.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Proposed synthesis of a linear poly-ethylenimine with hydroxyl pendants substituents at the adjacent carbon

The synthesis of a linear poly-ethylenimine with pendant hydroxyl groups bonded to backbone carbons adjacent to the backbone amine groups is investigated and compared to the conventional method of functionalizing branched poly-ethylenimine using epoxides for use in direct air capture of carbon dioxide. The addition of hydroxyl groups imparts stability against both oxidative degradation and the formation of urea by reducing the number of primary amines, while the novel method of bonding to the adjacent backbone carbon rather than directly to the amine is hypothesized to retain the higher capacity for carbon dioxide of secondary amines when compared to tertiary amines. We also expect that the hydroxyl substituents will impart stronger hydrogen bonding capabilities, resulting in stronger interactions between adjacent polymer chains and a subsequent decrease in mobility.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Development of Advanced Solid Sorbents for Direct Air Capture (Final Report)

RTI International is partnering with Creare, and Mohammed VI Polytechnic University (UM6P) successfully met all major technical objectives as outlined below: Identified one MOF adsorbent for DAC; Identified one amine-P-dendrimer adsorbent for DAC; Performed Computational fluid dynamics simulations of the MOF and amine-P-dendrimer adsorbents and validate them with experimental data; Selected one adsorbent for DAC; Demonstrated the scale-up of selected candidate and perform cost review; Performed a preliminary process design; Performed technology maturation plan and environmental health and safety risk assessment. After a thorough comparison between both adsorbents (MOFs and P-dendrimers) and based on their technical merits, the amine-based P-dendrimers sorbent was selected as the best performing adsorbent for DAC. In fact, the amine-based P-dendrimers have demonstrated superior performance over the MOF sorbents under relevant DAC conditions. The selected sorbent has been used in subsequent projects (DE-FE0032099 and DE-AR0001412) and has demonstrated similar superior performance with no loss of activity after long-term sorption-desorption testing (e.g., 100 cycles). This sorbent has demonstrated a very high and stable sorption performance, excellent kinetics, and fast regeneration at 80 °C, specifically at 75% relative humidity (RH). The incorporation of RTI’s high-performance, high-durability amine-based P-dendrimers sorbent and Creare’s hybrid additive manufacturing (H-AM) technology that will produce high performance, compact heat and mass exchange structures at low cost using methods, will lead to a contactor that is optimized for wind-driven operation. This contactor technology provides a technically viable pathway for reducing the cost of DAC to <$100/tonne of CO 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2023

Conversion of Syngas and CO2 to Light Olefins using Multi-Functional Catalysts

This report describes our effort in developing a novel zeolite encapsulated metal nanoparticle catalyst for the conversion of syngas to light olefins. We have adopted a ligand assisted synthesis protocol in which first metal-amine was prepared using metal salts and suitable amine ligands. The stable metal-amine complex thus prepared was then used as the seed for the growth of zeolite in alkaline solution. We have optimized the synthesis condition as well as different amine ligand to identify the condition to obtain stable metal-amine complex. Upon synthesis of zeolite, metal particles are encapsulated inside the zeolite in a confined space. We have synthesized both Fe and Co catalyst inside silicalite and chabazite zeolite. Catalytic activity of these catalysts were evaluated for syngas conversion reaction and compared with a baseline catalyst. The activity trend of zeolite encapsulated catalyst show very different activity trend compared to the baseline catalyst. While a distribution of products with different carbon number was obtained with baseline catalyst, zeolite encapsulated catalyst show ethylene as the major product. While ~73% selectivity to C 2 -C 6 products were obtained with cahabazite encapsulated Fe catalyst, only 53% selectivity was obtained for the corresponding products with silica-alumina supported Fe catalyst. Not only higher selectivity, Fe-chabazite also produces only C 2 products (ethylene/ethane) while a distribution of products was obtained with Fe-SiAl catalyst. The significantly different reactivity associated with the chabazite encapsulated Fe catalyst was attributed to the confinement effect. We hypothesized that due to the small size of the pore, only ethylene was obtained as the product.

10 SYNTHETIC FUELS↗
DOE OSTI2023

Mechanistic insights to drive catalytic hydrogenation of formamide intermediates to methanol via deaminative hydrogenation

Amine-promoted hydrogenation of CO 2 to methanol typically proceeds via a formamide intermediate when amines are used as additives or if the hydrogenation is performed in carbon capture solvents. The catalysts used for the hydrogenation of the formamide intermediate dictate the selectivity of the products formed: 1) Deoxygenative hydrogenation (C–O bond cleavage) resulting in N-methylation of amine and deactivation of the solvent, 2) Deaminative hydrogenation (C–N bond cleavage) resulting in formation of methanol and regeneration of the solvent. To date, catalytic reductions of CO 2 with amine promoters suffer from poor selectively for methanol which we attribute to the limiting formamide intermediate, though to date, the conditions that favor C–N cleavage have yet to be fully understood. To better understand the reactivity of the formamide intermediates, a range of heterogenous catalysts were used to study the hydrogenation of formamide. Well-known gas phase CO 2 hydrogenation catalysts catalyze the hydrogenation of formamide to N-methyl product via C–O bond cleavage. However, the selectivity can be readily shifted to selective C–N bond cleavage by addition of an additive with sufficient basicity for both homogenous and heterogeneous catalytic systems. The base additive shifts the selectivity by deprotonating a hemiaminal intermediate formed in situ during the formamide hydrogenation. This prevents dehydration process leading to N-methylated product, which is a key capture solvent deactivation pathway that hinders amine use in carbon capture, utilization, and storage (CCUS). The findings from this study provide a roadmap on how to improve the selectivity of known heterogenous catalysts, enabling catalytic reduction of captured CO 2 to methanol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2010

Testing and Results of Vacuum Swing Adsorption Units for Spacesuit Carbon Dioxide and Humidity Control

A principal concern for extravehicular activity (EVA) space suits is the capability to control carbon dioxide (CO2) and humidity (H2O) for the crewmember. The release of CO2 in a confined or unventilated area is dangerous for human health and leads to asphyxiation; therefore, CO2 and H2O become leading factors in the design and development of the spacesuit. An amine-based CO2 and H2O vapor sorbent for use in pressure-swing re-generable beds has been developed by Hamilton Sundstrand. The application of solid-amine materials with vacuum swing adsorption technology has shown the capacity to concurrently manage CO2 and H2O levels through a fully regenerative cycle eliminating mission constraints imposed with non-regenerative technologies. Two prototype solid amine-based systems, known as rapid cycle amine (RCA), were designed to continuously remove CO2 and H2O vapor from a flowing ventilation stream through the use of a two-bed amine based, vacuum-swing adsorption system. The Engineering and Science Contract Group (ESCG) RCA is the first RCA unit implementing radial flow paths, whereas the Hamilton Sundstrand RCA was designed with linear flow paths. Testing was performed in a sea-level pressure environment and a reduced-pressure environment with simulated human metabolic loads in a closed-loop configuration. This paper presents the experimental results of laboratory testing for a full-size and a sub-scale test article. The testing described here characterized and evaluated the performance of each RCA unit at the required Portable Life Support Subsystem (PLSS) operating conditions. The test points simulated a range of crewmember metabolic rates. The experimental results demonstrate the ability of each RCA unit to sufficiently remove CO2 and H2O from a closed loop ambient or subambient atmosphere.

McMillin, Summer↗
DOE OSTI2026

A Chemoselective and Stereodivergent Platform of Heme‐Nitrene Transferases to Access Chiral Aryl‐β‐Amino Esters and An Investigation of the Sequence‐Activity Landscape

Engineered biocatalysts can utilize nitrene precursors to access enantioenriched amination products, yet they have not been applied to produce valuable, enantiomerically enriched noncanonical β-amino esters. Current approaches to synthesizing β-amino acids rely on pre-oxidized precursors and multistep synthetic approaches involving various protecting groups. We engineered a platform of heme enzymes for stereoselective C–H bond amination of readily available carboxylic ester derivatives to install primary amines. A directed evolution campaign coupled with sequencing of over 1000 variants enabled us to develop engineered variants that use either O-pivaloylhydroxylamine triflic acid (PONT) or hydroxylamine hydrochloride (H 2 NOH∙HCl) as aminating reagents. An analysis of the resulting sequence–activity dataset revealed additional improvements that could be made to the final variant, highlighting the utility of sequencing data to guide future steps in directed evolution campaigns. Furthermore, the evolved nitrene transferases expand the scope of accessible chiral β-amino acid building blocks for peptidomimetic applications and provide new starting points for the design and synthesis of enantioenriched β-amino acid motifs.

amino ester building blocks↗
DOE OSTI2023

Targeted electrochemical reduction of carcinogenic N -nitrosamines from emission control systems within CO 2 capture plants

N-Nitrosamines are one of the environmentally significant byproducts from aqueous amine-based post-combustion carbon capture systems (CCS) due to their potential risk to human health. Safely mitigating nitrosamines before they are emitted from these CO 2 capture systems is therefore a key concern before widescale deployment of CCS can be used to address worldwide decarbonization goals. Electrochemical decomposition is one viable route to neutralize these harmful compounds. The circulating emission control waterwash system, commonly installed at the end of the flue gas treatment trains to minimize amine solvent emissions, plays an important role to capture N-nitrosamines and control their emission into the environment. The waterwash solution is the last point where these compounds can be properly neutralized before becoming an environmental hazard. In this study, the decomposition mechanisms of N-nitrosamines in a simulated CCS waterwash with residual alkanolamines was investigated using several laboratory-scale electrolyzers utilizing carbon xerogel (CX) electrodes. Hcell experiments revealed that N-nitrosamines were decomposed through a reduction reaction and are converted into their corresponding secondary amines thereby neutralizing their environmental impact. Batch-cell experiments statistically examined the kinetic models of N-nitrosamine removal by a combined adsorption and decomposition processes. The cathodic reduction of the N-nitrosamines statistically obeyed the first-order reaction model. Finally, a prototype flow-through reactor using an authentic waterwash was used to successfully target and decompose N-nitrosamines to below the detectable level without degrading the amine solvent compounds allowing them to be return to the CCS and lower the system operating costs. Furthermore, the developed electrolyzer was able to efficiently remove greater than 98% of N-nitrosamines from the waterwash solution without producing any additional environmentally harmful compounds and offers an effective and safe route to mitigate these compounds from CO 2 capture systems.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2025

CO 2 Capture Characteristics of Hyperbranched Poly(alkylene imine): A Molecular Dynamics Simulation Approach

This study explores the CO 2 capture characteristics of hyperbranched poly(ethylenimine) (HB-PEI) and poly- (propyleneimine) (HB-PPI) through molecular dynamics simulations using density functional theory-calibrated force fields. Key features such as density, free volume, glass transition temperature, CO 2 /H 2 O distribution, and molecular diffusion are systematically investigated to elucidate structure−function relationships under dry and hydrated conditions. HB-PEI demonstrates a slightly higher density and lower free volume compared to HB-PPI yet shows superior CO 2 capture due to the high amine concentration. Glass transition analysis indicates a higher thermal mobility in HBPEI, enhancing the CO 2 diffusivity. Pair correlation and coordination analyses confirm a stronger affinity of CO 2 with primary and secondary amines, particularly in hydrated environments where water competes with CO 2 for binding sites. Despite its more compact structure, HB-PEI outperformed HB-PPI in CO 2 and H 2 O transport, as confirmed by higher diffusion coefficients across all hydration levels. These findings highlight a critical balance among polymer architecture, amine accessibility, and hydration in designing next-generation solid amine sorbents for efficient direct air capture applications.

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

CO 2 Capture with Capsules of Ionic Liquid/Amines

Carbon capture remains an urgent issue that has gained a great deal of attention over the past few decades. Aqueous amines have excellent selectivity, but present corrosion and volatility issues, whereas ionic liquids (ILs) have negligible volatility and tunable physical properties, but high viscosities. One approach to improve the practical performance of these liquids is encapsulating them in a CO 2 permeable polymer shell to enhance the accessibility of the liquid and the CO 2 absorption rate. In this work, we report the encapsulation of a mixture of amine and IL (i.e., monoethanolamine (MEA) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ])) and demonstrate enhanced carbon capture performance. A soft-template approach and interfacial polymerization are used to give capsules with liquid core (64 wt %) and polyurea shell. Compared to the bulk liquid, the encapsulated liquid shows improved thermal stability over cycles of absorption at 25 °C, and desorption at 75 °C. The capsules with core of [BMIM][BF 4 ]-MEA show 0.2 mol CO 2 /kg of capsules at 1 bar CO 2 , compared to the bulk liquid, which has 0.05 mol CO 2 /kg of sorbent. This is attributed to the limited evaporation of the amines. Alternatively, the same capsules but with 5 wt % of piperazine (Pz) in the core have doubled gravimetric CO 2 capacity of the capsules (0.4 mol CO 2 /kg of capsules); performance is evaluated over 10 capture–release cycles showing minimal mass loss. Characterization of the CO 2 uptake of the polymer shell itself reveals that the shell contributes only ~10% of the observed capacity, likely attributed to amine functionalities of the polymer. Here, this facile approach to encapsulating such “active” liquids can be applied to other CO 2 selective solvents that are volatile, viscous, and corrosive.

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

Electrochemical Reductive N-Methylation with CO 2 Enabled by a Molecular Catalyst

The development of benign methylation reactions utilizing CO 2 as a one-carbon building block would enable a more sustainable chemical industry. Electrochemical CO 2 reduction has been extensively studied, but its application for reductive methylation reactions remains out of the scope of current electrocatalysis. Here, in this work, we report the first electrochemical reductive N-methylation reaction with CO 2 and demonstrate its compatibility with amines, hydroxylamines, and hydrazine. Catalyzed by cobalt phthalocyanine molecules supported on carbon nanotubes, the N-methylation reaction proceeds in aqueous media via the chemical condensation of an electrophilic carbon intermediate, proposed to be adsorbed or near-electrode formaldehyde formed from the four-electron reduction of CO 2 , with nucleophilic nitrogenous reactants and subsequent reduction. By comparing various amines, we discover that the nucleophilicity of the amine reactant is a descriptor for the C-N coupling efficacy. We extend the scope of the reaction to be compatible with cheap and abundant nitro-compounds by developing a cascade reduction process in which CO 2 and nitro-compounds are reduced concurrently to yield N-methyl amines with high mono-methylation selectivity via the overall transfer of 12 electrons and 12 protons.

amines↗
DOE OSTI2022

Low Regeneration Temperature Sorbents for Direct Air Capture of CO 2

Susteon Inc., in partnership with University of Wyoming and SoCalGas, successfully met all major technical objectives to (1) scale up the ionic liquid catalyst for amine-based sorbents for improved desorption and absorption kinetics, (2) evaluate the catalyzed amine-based sorbents for direct CO 2 capture process to determine CO 2 adsorption and desorption rates and energy requirements, and (3) based on the experimental results, develop a conceptual process design to perform a preliminary economic assessment to evaluate the potential for DAC process cost reduction using the catalyzed sorbents. Amine doped solid sorbents are effective for DAC applications and can be regenerated by heat or by a combination of heat, steam, and vacuum. The best sorbent composition identified was polyethyleneimine (PEI) on fumed silica with 200 ppm ionic liquid catalyst. This sorbent formulation was shown to have a CO 2 breakthrough capacity twice that of the non-catalyzed sorbent, in laboratory tests with air at 75% relative humidity (RH). The CO 2 adsorption rate was also 40% higher than that of the non-catalyzed sorbent. This type of sorbents has the attributes required for lowering the overall cost of DAC with high CO 2 capacity and high rate of adsorption. The combination of an industrially utilized amine-based sorbent with a highly active catalyst to form a new class of materials for DAC provides a technically viable pathway for reducing the cost of DAC to <$100/tonne of CO 2 . Laboratory measurements show that the silica/PEI (polyethyleneimine) sorbents with 100 ppm of ionic liquid catalyst have almost 100% higher CO 2 cyclic capacity and 40% higher adsorption rate. Generally, CO 2 desorption occurred at higher temperatures with a rate of desorption 10 times faster than adsorption (which occurred at ambient conditions). Therefore, adsorption rate is a much more important factor in the cost of DAC because it is directly linked to the CAPEX of the total system and the cycle time (i.e., sorbent productivity in ton/day of CO 2 captured per unit volume of the air contactor). An initial process design, coupled with techno-economic analysis, based on optimal experimental results and preliminary resulting from structured sorbent testing, showed a path to lower the DAC cost from the current cost of over $200/tonne CO 2 to less than $100/tonne with a scale-up, mature state of the technology, with projected material and process improvements. These results demonstrate the effectiveness of the catalyst in silica/PEI sorbents in enhancing sorbents’ CO 2 working capacity, in (a) increasing the rate of adsorption and desorption, and (b) in lowering the CAPEX and OPEX of the DAC system employing the ionic liquid catalyzed sorbents.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2024

Stable Cycling of Mg Metal Anodes by Regulating the Reactivity of Mg 2+ Solvation Species

Rationally designing stable nonaqueous electrolytes for Mg metal anodes demands a thorough understanding of their interfacial behaviors. Here, the critical role of cation–anion pairing in improving the cathodic stabilities of amine-based electrolytes against solvent reduction and H 2 evolution is identified. It is demonstrated that strong coordination between solvating amine groups and the Mg 2+ cation facilitates the dehydrogenation of the -NH 2 group, which is mainly responsible for low reversibility during Mg metal plating and stripping. Introducing ion-pairing into the primary solvation shell can effectively weaken the amine coordination such that its reduction is suppressed. A novel interfacial behavior regarding parasitic reaction product dissolution is also identified, which is responsible for the failure of interfacial passivation. An ion-pairing electrolyte is developed based on a weakly-solvated amine molecule and strongly coordinating Mg 2+ salt. This electrolyte composition delivers long-term Mg metal anode cycling with 99.6% Coulombic efficiency for 800 cycles.

25 ENERGY STORAGE↗
DOE OSTI2023

C−N Coupling through Hydroaminoalkylation on a Single‐Atom Rh Heterogeneous Catalyst

Abstract C−N coupling is significant for the synthesis of fine chemicals toward various applications. Hydroaminoalkylation of olefins is a tandem reaction of C−N coupling involving first the formation of an aldehyde through hydroformylation of an olefin and then the production of amine through reductive amination of the aldehyde. Here we report a stable, supported catalyst of singly dispersed Rh 1 atoms anchored on TiO 2 (P25) nanoparticles designated as Rh 1 /P25. Its high activity for C−N coupling was demonstrated by six hydroaminoalkylations of olefins and amines with selectivity of higher than 90% for producing tertiary amines. The singly dispersed Rh 1 O 4 on P25 exhibit activity and selectivity for hydroaminoalkylation comparable or even higher than some reported molecular catalysts. In contrast to molecular catalysts, the Rh‐based single‐atom Rh heterogeneous catalysis (Rh 1 /P25) can be readily separated from reactants and products, reused for multiple runs of hydroaminoalkylation, and recycled with a low cost.

Li, Yuting↗
DOE OSTI2023

C–N Coupling through Hydroaminoalkylation on a Single–Atom Rh Heterogeneous Catalyst

C–N coupling is significant for the synthesis of fine chemicals toward various applications. Hydroaminoalkylation of olefins is a tandem reaction of C–N coupling involving first the formation of an aldehyde through hydroformylation of an olefin and then the production of amine through reductive amination of the aldehyde. Here we report a stable, supported catalyst of singly dispersed Rh 1 atoms anchored on TiO 2 (P25) nanoparticles designated as Rh 1 /P25. Its high activity for C–N coupling was demonstrated by six hydroaminoalkylations of olefins and amines with selectivity of higher than 90% for producing tertiary amines. Furthermore, the singly dispersed Rh 1 O 4 on P25 exhibit activity and selectivity for hydroaminoalkylation comparable or even higher than some reported molecular catalysts. In contrast to molecular catalysts, the Rh-based single-atom Rh heterogeneous catalysis (Rh 1 /P25) can be readily separated from reactants and products, reused for multiple runs of hydroaminoalkylation, and recycled with a low cost.

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

Recent advances in polymeric facilitated transport membranes for carbon dioxide separation and hydrogen purification

Membrane and membrane process have been widely considered as one of the best candidates for mitigating CO 2 emissions from the combustion or utilization of fossil fuels. Various amine-containing polymers constitute an important class of membranes, where the highly selective CO 2 transport is achieved by the facilitated transport mechanism. In this review, the amine–CO 2 chemistry is discussed in conjunction with the mechanism of the reaction-mediated CO 2 transport. A wide variety of amine-containing polymers are discussed based on two synthesis motifs: (a) polyamines with amino groups covalently bound to the polymer backbone and (b) small molecule amines embedded in a polymer matrix. This review concludes with the remarks on the facilitated transport membranes for post-combustion carbon capture (CO 2 /N 2 ) and hydrogen purification (CO 2 /H 2 ).

42 ENGINEERING↗