Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “AMINES”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction

The activity of colloidally synthesized CoP for the hydrogen evolution reaction (HER) was studied to determine the impact of surface ligand on catalysis. The as-synthesized CoP nanocrystals were stripped with trialkyloxonium tetrafluoroborate (Meerwein’s reagent) to create a “blank template” that was then religated with carboxylates (oleate, octanoate, acetate) and amines (oleylamine, octylamine, dioctylamine, trioctylamine butylamine). Carboxylates and amines were chosen due to their prevalence in colloidal syntheses, and the range of ligands was chosen to study the impact of sterics and hydrophobicity of the surface ligands on catalysis. Long chain carboxylates were found to result in a larger increase in overpotential when compared to the equivalent amine (e.g., oleate vs oleylamine), due to higher ligand density and stronger coordination with carboxylates. Increased carbon chain length resulted in increased overpotential with carboxylates; however, the range of 1° amines studied had similar overpotentials. This is due to the lower ligand density and therefore sparse ligand packing for the 1° amines. These results suggest that the mechanism by which surface ligands impede catalysis on CoP for HER is primarily through inhibiting substrate access to surface active sites rather than poisoning the active sites.

cobalt phosphide, hydrogen evolution reaction, lig↗
DOE OSTI2023

Tailoring the Near-Surface Environment of Rh Single-Atom Catalysts for Selective CO 2 Hydrogenation

For this study, we used a combination of experimental spectroscopies, density functional theory calculations, and CO 2 hydrogenation studies to investigate the effects of modifying single-atom Rh 1 /TiO 2 catalysts with functionalized phosphonic acid monolayers. We found that the deposition of specific amine-functionalized ligands resulted in an ~8× increase in site-specific CO 2 reduction turnover frequency at 150 °C and a ~2× increase at 250 °C. On-stream stability also improved following ligand deposition. The effect of the modifier on reactivity was highly sensitive to the proximity of the amine functional group to the surface, which was controlled by adjusting the length of the phosphonic acid tail. Furthermore, deposition of alkyl phosphonic acids without an amine functional group resulted in blocked CO 2 adsorption and a near-complete loss of catalytic activity. Infrared spectroscopy studies suggested that the amine group provided binding sites for CO 2 that enabled hydrogenation when the amine was positioned near a Rh1 site. Phosphonic acid-modified catalysts also exhibited high selectivity to CO over the series product methane; the selectivity effect was traced to modification of the Rh1 sites to favor CO desorption. Phosphonic acid deposition resulted in 80–90% loss of accessible Rh1 sites, likely due to blocking by tail groups. However, even with the loss of sites, under low-temperature reaction conditions, the rates of CO 2 hydrogenation were improved with the coatings, indicating that the remaining sites are highly efficient. Organic functionalization of the supports for atomically dispersed catalysts offers the opportunity to precisely control the positioning of functional groups in the vicinity of a well-defined active site, potentially enabling an additional level of control over active site design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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 OSTI2014

Heterolytic Cleavage of H2 by Bifunctional Manganese(I) Complexes: Impact of Ligand Dynamics, Electrophilicity, and Base Positioning

We report the synthesis, characterization, and reactivity with H2 of a series of MnI complexes of the type [(P-P)Mn(L2)CO]+ (L2 = dppm, bppm, or (CO)2; P-P = PPhNMePPh or PPh2 NBn2 ) that bear pendant amine ligands designed to function as proton relays. The pendant amine was found to function as a hemilabile ligand; its binding strength is strongly affected by the ancillary ligand environment around Mn. Tuning the electrophilicity of the Mn center leads to systems capable of reversible heterolytic cleavage of the H-H bond. The strength of pendant amine binding can be balanced to protect the Mn center while still leading to facile reactivity with H2. Neutral amine-bearing MnIH species were found to react with one-electron oxidants and, after proton and electron transfer reactions, regenerate MnI cationic species. The reactivity presented herein indicate that the Mn complexes we have developed are a promising platform for Mn-based H2 oxidation electrocatalyst development. The research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE.

electrochemistry↗
DOE OSTI2015

A chimeric prokaryotic pentameric ligand–gated channel reveals distinct pathways of activation

Recent high resolution structures of several pentameric ligand–gated ion channels have provided unprecedented details of their molecular architecture. However, the conformational dynamics and structural rearrangements that underlie gating and allosteric modulation remain poorly understood. We used a combination of electrophysiology, double electron–electron resonance (DEER) spectroscopy, and x-ray crystallography to investigate activation mechanisms in a novel functional chimera with the extracellular domain (ECD) of amine-gated Erwinia chrysanthemi ligand–gated ion channel, which is activated by primary amines, and the transmembrane domain of Gloeobacter violaceus ligand–gated ion channel, which is activated by protons. We found that the chimera was independently gated by primary amines and by protons. The crystal structure of the chimera in its resting state, at pH 7.0 and in the absence of primary amines, revealed a closed-pore conformation and an ECD that is twisted with respect to the transmembrane region. Amine- and pH-induced conformational changes measured by DEER spectroscopy showed that the chimera exhibits a dual mode of gating that preserves the distinct conformational changes of the parent channels. Collectively, our findings shed light on both conserved and divergent features of gating mechanisms in this class of channels, and will facilitate the design of better allosteric modulators.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
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 OSTI2013

High-performance sorbents for carbon dioxide capture from air

This project has focused on capture of CO 2 from ambient air (“air capture”). If this process is technically and economically feasible, it could potentially contribute to net reduction of CO 2 emissions in ways that are complementary to better developed techniques for CO 2 from concentrated point sources. We focused on cyclic adsorption processes for CO 2 capture from air in which the entire cycle is performed at moderate temperatures. The project involved both experimental studies of sorbent materials and process level modeling of cyclic air capture processes. In our experimental work, a series of amine-functionalized silica adsorbents were prepared and characterized to determine the impact of molecular architecture on CO 2 capture. Some key findings were: • Amine functionalized silicas can be prepared with high enough CO 2 capacities under ambient conditions to merit consideration for use in air capture processes. • Primary amines are better candidates for CO 2 capture than secondary or tertiary amines, both in terms of amine efficiency for CO 2 adsorption and enhanced water affinity. • Mechanistic understanding of degradation of these materials can enable control of molecular architecture to significantly improve material stability. Our process modeling work provided the first publically available cost and energy estimates for cyclic adsorption processes for air capture of CO 2 . Some key findings were: • Cycles based on diurnal ambient heating and cooling cannot yield useful purities or amounts of captured CO 2 . • Cycles based on steam desorption at 110 oC can yield CO 2 purities of ~88%. • The energy requirements for cycles using steam desorption are dominated by needs for thermal input, which results in lower costs than energy input in the form of electricity. Cyclic processes with operational costs of less than $\$$100 tCO 2 -net were described, and these results point to process and material improvements that could substantially reduce these costs. The most critical conclusions from our work are that (i) CO 2 capture from ambient air using moderate temperature cyclic adsorption processes is technically feasible and (ii) the operational costs of realistic versions of these processes are moderate enough to encourage future development of this technology. Because of the very modest net investment that has been made in R&D associated with this approach from all sources worldwide (relative to the massive public and private investment that has been made in technologies for CO 2 from concentrated point sources), our results strongly suggest that continued development of air capture is justified.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Ediesel: Diesel Additive production from ethanol and bio-diesel coproducts

This project has focused on supporting and expanding the U.S. ethanol industry by developing new conversion routes and products from ethanol and the byproducts made in ethanol fermentation. The work is relevant to the DOE program goals of developing high-margin chemical products in the biorefinery to economically support large-scale biofuel production. The higher alcohols from condensation of ethanol, alkylated amine compounds made by electrocatalytic alkyation, and fusel alcohols produced by modified fermentation microorganisms are all existing or potentially large-scale commodity or specialty chemicals with well-defined uses in industry. The formation of higher alcohols from ethanol in the condensed phase developed several catalysts, first in stirred batch autoclave reactors and then in a continuous flow reactor system, to achieve significant yields of n-butanol and higher alcohols. The best selectivity to higher alcohols exceeded 80% of theoretical at ethanol conversions of 30-40%. From the laboratory experiments and analysis of the phase equilibria of the species involved, a process concept was generated and simulated in AspenPlus to determine the specifications of the various equipment involved in the process. Results show that for the conversion and selectivity described above, the required n-butanol selling price of ~$1.60/kg is in the range of current n-butanol selling price in the marketplace. Several additional permutations of the process, along with evaluation of higher conversion and selectivities to desired alcohol products, showed that the production of n-butanol from ethanol should be competitive in the marketplace as the science and engineering behind the process improves with continued development. A second aspect of the project focused on producing fusel alcohols in increased quantities during ethanol fermentation. Fusel alcohols, which are composed primarily of isoamyl alcohol and minor quantities of C3-C6 alcohols, have potential as higher value feed stocks for specialty chemical production. Several strains of yeast were evaluated for fusel alcohol production, and the most efficient process for separating and purifying fusel alcohols was developed from both experiments and simulation. Finally, model fusel alcohol mixtures were subjected to condensation reactions with ethanol to prepare higher alcohols that again have potential for specialty chemical or solvent applications. In this preliminary work, measurable quantities of several species were observed, including some species that were previously unknown or uncharacterized in the literature. The third aspect of the project involved the electrocatalytic alkylation of amines with alcohols to form alkyl amines. Ethanol has been demonstrated to serve as an effective ethyl group transfer agent to the nitrogen centers of amines, a reaction with only water as a byproduct. Mild reaction conditions (60 °C, aqueous solution) are enabled by the novel use of simple, undivided electrochemical cell reactors that include long-lived, low cost catalytic electrodes. Direct polyalkylation of ammonia and isolation of the resulting triethylamine product was readily achieved in high yield. Though classical high temperature and pressure industrial scale alkylations reactions will likely continue to be used for production of simple product such as triethylamine, this approach has opened the door to the low cost, low waste use of ethanol and related primary and secondary alcohols to alkylate more delicate amines that were heretofore difficult to synthesize.

02 PETROLEUM↗
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 OSTI2013

Regenerable solid imine sorbents

Two new classes of amine-based sorbents are disclosed. The first class comprises new polymer-immobilized tertiary amine sorbents; the second class new polymer-bound amine sorbents. Both classes are tailored to facilitate removal of acid anhydrides, especially carbon dioxide (CO.sub.2), from effluent gases. The amines adsorb acid anhydrides in a 1:1 molar ratio. Both classes of amine sorbents adsorb in the temperature range from about 20.degree. C. upwards to 90.degree. C. and can be regenerated by heating upwards to 100.degree. C.

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

Preparation of sorbent pellets with high integrity for sorption of CO.sub.2 from gas streams

Method for the production of a CO.sub.2 sorbent prepared by integrating a clay substrate, basic alkali salt, amine liquid, hydraulic binder, and a liquid binder. The basic alkali salt is present relative to the clay substrate in a weight ratio of from about 1 part to about 50 parts per 100 parts of the clay substrate. The amine liquid is present relative to a clay-alkali combination in a weight ratio of from about 1 part to about 10 parts per 10 parts of the clay-alkali combination. The clay substrate and basic alkali salt may be combined in a solid-solid heterogeneous mixture and followed by introduction of the amine liquid. Alternatively, an alkaline solution may be blended with the amine solution prior to contacting the clay substrate. The clay-alkali-amine CO.sub.2 sorbent is particularly advantageous for low temperature CO.sub.2 removal cycles in a gas stream having a CO.sub.2 concentration less than around 2000 ppm and an oxygen concentration around 21%, such as air.

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

Postsynthetic Functionalization of Mg-MOF-74 with Tetraethylenepentamine: Structural Characterization and Enhanced CO 2 Adsorption

Postsynthetic functionalization of magnesium 2,5-dihydroxyterephthalate (Mg-MOF-74) with tetraethylenepentamine (TEPA) resulted in improved CO 2 adsorption performance under dry and humid conditions. XPS, elemental analysis, and neutron powder diffraction studies indicated that TEPA was incorporated throughout the MOF particle, although it coordinated preferentially with the unsaturated metal sites located in the immediate proximity to the surface. Neutron and X-ray powder diffraction analyses showed that the MOF structure was preserved after amine incorporation, with slight changes in the lattice parameters. The adsorption capacity of the functionalized amino-Mg-MOF-74 (TEPA-MOF) for CO 2 was as high as 26.9 wt % versus 23.4 wt % for the original MOF due to the extra binding sites provided by the multiunit amines. Here, the degree of functionalization with the amines was found to be important in enhancing CO 2 adsorption, as the optimal surface coverage improved performance and stability under both pure CO 2 and CO 2 /H 2 O coadsorption, and with partially saturated surface coverage, optimal CO 2 capacity could be achieved under both wet and dry conditions by a synergistic binding of CO 2 to the amines as well as metal centers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Catalytic Upgrading of Biomass-Derived Methyl Ketones to Liquid Transportation Fuel Precursors by an Organocatalytic Approach

A highly efficient water-tolerant, solid-base catalyst for the self-condensation of biomass-derived methyl ketones to jet-diesel fuel precursors was developed by grafting site-isolated secondary amines on silica-alumina supports. Here, it is shown that apart from the nature and density of amine groups and the spatial separation of the acidic and basic sites, the acidity of the support material plays a critical role in defining the catalytic activity. It is also found that a combination of weakly acidic silanol/aluminol with secondary amine groups can mimic proline catalysts and are more effective in catalyzing the selective dimerization reaction than the combination of amines with organic acids. In situ FTIR measurements demonstrate that acidic groups activate methyl ketones through their carbonyl groups leading to a favorable C-C bond formation step involving an enamine intermediate. DFT analysis of the reaction pathway confirms that C-C bond formation is the rate-limiting step.

aldol condensation↗