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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Molecular-scale mechanisms of CO 2 mineralization in nanoscale interfacial water films

The calamitous impacts of untethered carbon emission from fossil-fuel-burning energy infrastructure calls for accelerated development of large-scale CO 2 capture, utilization, and storage technologies that are underpinned by fundamental understanding of molecular-level chemical processes. In the subsurface, rocks rich in divalent metals can react with CO 2 , permanently sequestering it in the form of stable metal carbonate minerals, with the CO 2 -H 2 O composition of the post-injection pore fluid acting as a primary control variable. Herein, we compare mechanistic reaction pathways for aqueous-mediated carbonation with carbon mineralization occurring in nanoscale adsorbed water films. In the extreme of pores filled with a CO 2 -dominant fluid, carbonation reactions are confined to nanometer-thick water films coating mineral surfaces, which enable metal cation release, transport, nucleation, and crystallization of metal carbonate minerals. Though seemingly counterintuitive, laboratory studies have demonstrated facile carbonation rates in these low water environments, which in recent years has begun to be better understood in mechanistic detail. The overarching objective of this review is to delineate the unique underlying molecular-scale reaction mechanisms that govern CO 2 mineralization in these reactive and dynamic quasi-2D interfaces. Here. we highlight the importance of understanding unique properties in thin water films, such as how water dielectric properties, and consequently ion solvation/hydration behavior, can change under nanoconfinement. We conclude by identifying important frontiers for future work and opportunities to exploit these fundamental chemical insights for decarbonization technologies in the 21st century.

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

Transport Cost for Carbon Removal Projects With Biomass and CO2 Storage

Strategies to remove carbon from the atmosphere are needed to meet global climate goals. Promising strategies include the conversion of waste biomass to hydrogen, methane, liquid fuels, or electricity coupled with CO 2 capture and storage (CCS). A key challenge for these projects is the need to connect geographically dispersed biomass supplies with geologic storage sites by either transporting biomass or CO 2 . We assess the cost of transport for biomass conversion projects with CCS using publicly available cost data for trucking, rail, and CO 2 pipelines in the United States. We find that for large projects (order of 1 Mt/yr CO 2 or greater), CO 2 by pipeline is the lowest cost option. However, for projects that send most of the biomass carbon to storage, such as gasification to hydrogen or electricity production, biomass by rail is a competitive option. For smaller projects and lower fractions of carbon sent to storage, such as for pyrolysis to liquid fuels, CO 2 by rail is the lowest cost option. Assessing three plausible example projects in the United States, we estimate that total transport costs range from $24/t-CO 2 stored for a gasification to hydrogen project traversing 670 km to $\$ 36$/t for a gasification to renewable natural gas project traversing 530 km. In general, if developers have flexibility in choosing transport mode and project type, biomass sources and storage sites can be connected across hundreds of kilometers for transport costs in the range of $20-40/t-CO 2 stored. Truck and rail are often viable modes when pipelines cannot be constructed. Distances of 1,000 km or more can be connected in the same cost range when shared CO 2 pipelines are employed.

09 BIOMASS FUELS↗
DOE OSTI2024

Examining the Reactions of Ethanolamine’s Thermal Degradation Compounds in Carbon Capture through 1 H NMR and 13 C NMR

In amine scrubbing carbon capture, concerns about amine solvent degradation include whether it can affect the ability of the solvent to capture CO 2 . This study examines the interactions between the three most reported monoethanolamine (MEA) thermal degradation compounds namely, oxazolidine-2-one (OZD), N-(2-hydroxyethyl)-ethylenediamine (HEEDA), and N-(2- hydroxyethyl)-imidazoline-2-one (HEIA) with CO 2 in the presence and absence of MEA. We compared 1 H NMR, 13 C NMR, and heteronuclear single-quantum coherence (HSQC) NMR for neat OZD, HEEDA, and HEIA samples with CO 2 -loaded samples to observe changes in protonation and unique carbamate species formation. We found that OZD and HEIA did not directly react with CO 2 or undergo proton shifting based on our comparison of the neat OZD and HEIA samples with CO 2 -loaded spectra. However, we observed that the OZD can protonate when sparged with CO 2 in the presence of MEA, which suggests that the OZD acts as an intermediate. The NMR spectra for HEEDA indicated that HEEDA directly reacts with CO 2 at both amino groups and can protonate. In the presence of MEA, HEEDA and MEA can act like a solvent blend, resulting in multiple carbamates forming within the solvent. The neat HEIA spectrum, compared with CO 2 -loaded HEIA spectra, revealed similar results as OZD, where it does not react with CO 2 or protonate directly. However, HEIA does not protonate in the presence of MEA. These degradation compound reactions can increase the number of general equilibrium reactions during carbon capture and impact the model MEA solvent. This work helps provide a more complete picture of the reactions as the solvent degrades. Although this study examines CO 2 effects on thermal degradation products for MEA, other amines such as piperazine or 1- amino-3-propanol will degrade, and the degradation may speciate similarly with CO 2 . Furthermore, this study can impact and improve process models by assessing the degradation compounds’ reactions with CO 2 and potentially incorporating them into the model based on a neat solvent.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2026

Bench-Scale Development of Promoted High-Capacity Structured Sorbents (Final Technical Report)

The project objective was to develop high-capacity structured sorbent capable of achieving low CO 2 removal from air. The sorbent framework consists of an amine-functionalized onto hydrophobic polymer backbone with an added promoter. The functionalized amine provides high CO 2 capacity and adsorption rates and the polymer backbone to reduce water uptake. For the sorbent development, multiple functionalized amines and promoters were assessed to select a candidate that achieved high CO 2 capacity, high adsorption rate, and high stability. A sorbent-coated filter design was selected as the structured sorbent, which provides high sorbent loading capacity and contains an electrically conductive nonwoven filter substrate that can be Joule-heated to provide efficient utilization of available electricity for sorbent regeneration. A commercial partner operated a pilot filter manufacturing line to produce the filter panels coated with the developed sorbent. A 1 kg CO 2 /day bench unit was designed and fabricated to test the structured filter sorbent. The key achievements from the structured sorbent development activity were demonstrating that existing filter industrial-scale processes can be used for manufacturing Susteon’s structured sorbent and completing a proof-of-concept demonstration of the commercially manufactured structured sorbent filters for CO 2 capture from air with direct, Joule-heated regeneration. A techno-economic assessment with sensitivity analysis was conducted on a 100,000 TPY facility with 85% operating capacity. Through sorbent optimization and process design improvements, it is estimated that the cost of capture was reduced from $\$$349/tCO 2 to $\$$241/tCO 2 . The TEA projects further reductions to $165/tCO 2 through enhancements in CO 2 adsorption rate and sorbent capacity and reducing manufacturing and scale up risks. A life cycle analysis was conducted on the same 100,000 TPY facility and confirmed that the facility’s electricity demand drives its greenhouse gas impact. It was determined that electricity supplied through the current grid mix would result in net-positive CO 2 emissions and that achieving net-negative emissions is only possible by powering the system with renewable electricity or fossil fuel sources equipped with carbon capture and sequestration.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Carbon Capture Beyond Amines: CO 2 Sorption at Nucleophilic Oxygen Sites in Materials

Carbon capture and utilization or sequestration and direct air capture will be needed to reduce atmospheric levels of greenhouse gases over the next century. Current amine-based technologies bind CO 2 with high selectivities but suffer from poor oxidative and thermal stabilities. Herein, we discuss understudied sorbents based on oxygen nucleophiles, including metal oxides and hydroxides, hydroxide-containing polymers, and hydroxide-based metal–organic frameworks. In general, these materials display improved oxidative stabilities compared to traditional amine-based sorbents. Here, we outline the challenges and opportunities offered by these alternative sorbents for carbon capture applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Direct aromatization of CO 2 via combined CO 2 hydrogenation and zeolite-based acid catalysis

Aromatics, including benzene, toluene, and xylenes (BTX), are essential chemical building blocks and are widely used as solvents, fuel additives, and polymers. With the recent development in CO 2 capture technologies and the progress made in producing H 2 using renewable energy, direct hydrogenation of CO 2 to aromatics via heterogeneous catalysis has emerged as a promising pathway to accomplish the production of aromatics with simultaneous utilization of waste CO 2 . In this review, we focus on recent advances in the nascent field of direct CO 2 aromatization, whereby tandem catalysts composed of CO 2 hydrogenation and aromatization functionalities are designed and deployed. We review two categories of tandem catalysts: catalysts integrating Fe-based/H-ZSM-5 components following RWGS (reverse water-gas shift of CO 2 to CO)-FT (Fischer-Tropsch synthesis of lower olefins)-aromatization pathways, and catalysts combining metal oxide/H-ZSM-5 domains following CO 2 to methanolaromatization pathways. The key parameters that determine the catalytic performance, such as the composition and structure of the Fe-based or metal oxide-based CO 2 conversion catalysts, the properties of H-ZSM-5, and the synergy between the two components, are analyzed to provide insights for the design of efficient tandem catalysts for CO 2 aromatization. In parallel, thermodynamic analyses, mechanistic studies, and density functional theory (DFT) computations for the relevant reaction routes and pathways are discussed to offer improved understanding of CO 2 activation, reaction intermediates, and product formation. In closing, the challenges and prospects for these tandem reactions are addressed to provide suggested paths forward for future research.

10 SYNTHETIC FUELS↗
DOE OSTI2025

Optimizing CO 2 -Loaded Aqueous Amine Solutions for Higher Electrocatalytic CO 2 Reduction Activity

The activity of aqueous-based carbon dioxide reduction (CO 2 R) reactions is often limited by the solubility of CO 2 . The addition of amines can increase the total dissolved carbon in water through the formation of bicarbonate and carbamate species, which has been used to a great effect to capture CO 2 from dilute streams. Here, in this study, we explore the effect of 12 primary and secondary amines of varying Brønsted basicity, steric profile, and hydrogen-bonding capabilities on the aqueous CO 2 R to CO activity of a molecular Ni(cyclam)Cl 2 catalyst with a Hg electrode. Addition of some of the amines results in greater activity and selectivity for CO production compared to equivalent aqueous solutions without added amines. Under optimal conditions (0.4 M 3-amino-propionitrile), there is an over sevenfold increase in partial current density and greater selectivity for CO compared to equivalent conditions with no amine. Interestingly, the increase in activity did not correlate to any single property across the 12 amines. To elucidate the effect of the amine additives on catalysis, we used vapor–liquid equilibrium modeling (VLE), 13 C NMR spectroscopy, and computational analysis to determine the carbon speciation of the solutions. These results indicate that for amines without ethylalcohol functionalities, CO 2 R activity correlates with carbamate concentration, which is in turn governed by amine basicity and steric effects. However, this correlation does not persist for amines with ethylalcohol functionalities, which can form more stable carbamates through intramolecular-hydrogen bonding. These studies demonstrate that amine additives can enhance aqueous CO 2 R activity and selectivity and describe amine properties that lead to these higher performance metrics.

Amines↗
DOE OSTI2023

Integrated low carbon H 2 conversion with in situ carbon mineralization from aqueous biomass oxygenate precursors by tuning reactive multiphase chemical interactions

Meeting our rising demand for clean energy carriers such as H 2 from renewable biomass resources is challenged by the co-emission of CO 2 and CH 4 . To address this challenge, we design novel reactive separation pathways that integrate multiphase chemical reactions by harnessing Ca and Mg bearing minerals as a sorbent to capture CO 2 released during the hydrothermal deconstruction of aqueous biomass oxygenates to produce H 2 and solid carbonates via low temperature aqueous phase reforming and thermodynamically downhill carbon mineralization. Earth abundant catalysts such as Ni/Al 2 O 3 are effective in producing H 2 yields as high as 79% and 74% using ethylene glycol and methanol in the presence of Ca(OH) 2 as an alkaline sorbent, without contaminating or deactivating the catalyst. H 2 yields with in situ carbon mineralization using a Ni or Pt/Al 2 O 3 catalyst are enhanced based on the following order of reactivity: acetate < glycerol < methanol < formate < ethylene glycol. These studies demonstrate that the multiphase chemical interactions can be successfully tuned to enhance H 2 yields through the selective cleavage of C–C bonds using Ni/Al 2 O 3 catalysts to deconstruct biomass oxygenates for producing H 2 and CO 2 , and in situ carbon mineralization by harnessing abundant alkaline materials, as demonstrated using ladle slag. This approach unlocks new scientific possibilities for harnessing multiple emissions including abundant organic-rich wastewater streams and alkaline industrial residues to co-produce low carbon H 2 and carbonate-bearing materials for use in construction by using renewable solar thermal energy resources.

09 BIOMASS FUELS↗
DOE OSTI2024

Potential for Combined Heat and Power with Carbon Capture and Storage at U.S. Ethanol Facilities

Conference paper presented at 17th International Conference on Greenhouse Gas Control Technologies (GHGT-17), Calgary, Alberta, Canada, October 20–24, 2024. Economic conditions in the United States have positioned ethanol producers as early adopters of industrial CO 2 capture and storage (CCS) from fermentation processes, creating an opportunity to further reduce emissions. Replacing fossil fired energy with biogenic combined heat and power (CHP) coupled with CCS could enable ethanol production to achieve net negative CO 2 emissions, with gasification based CHP better matching ethanol facilities’ heat and power needs than combustion based systems. Pilot scale testing showed that while 100% biomass gasification increased tar formation, cofeeding corn stover with coal and optimizing gasifier configurations offered promising pathways to reduce tar and improve operational performance.

09 BIOMASS FUELS↗
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 OSTI2024

Photoinduced Carbon Dioxide Release via a Metastable Photoacid in a Nonaqueous Environment

Capturing and concentrating carbon dioxide (CO 2 ) from the atmosphere is an important modern scientific and technological challenge. CO 2 can be captured by forming a carbamate bond with amines, most notably monoethanolamine (MEA). Regenerating MEA by releasing the captured CO 2 requires heating the carbamate solution, which is energy-demanding and wasteful. Recently, photoacids were used to convert light input into pH change, which in turn released CO 2 from aqueous carbonate solutions. Here, we report a merocyanine photoacid that releases CO 2 from a non-aqueous carbamate solution of MEA, thereby extending the utility of this concept to a wider range of capture agents and environments. Based on the absorption spectra of the photoacid in the presence of acids and CO 2 , we show that the photoacid cycle and the CO 2 capture of MEA are two separate equilibria that are coupled to each other via protons. Then, we demonstrate that irradiating 405 nm light on the sample can induce release of CO 2 which we detect using an in-line mass spectrometer. This work highlights an alternative path for optimizing a photo-induced CO 2 capture and release system.

Amines↗
DOE OSTI2023

A General Binary Isotherm Model for Amines Interacting with CO 2 and H 2 O

CO 2 capture by primary or secondary amines has been of great research interests for a century because of its industrial importance. Interest has grown even more, because of the need to eliminate the CO 2 emissions that drive global warming. Experimental evidence shows that CO 2 sorption in primary or secondary amines is accompanied by co-absorption of H 2 O. A quantitative analysis of such CO 2 -H 2 O co-absorption behavior is important for practical process design and theoretical understanding. Even though there is almost an experimental consensus that water enhances CO 2 uptake capacity, an analytic model to explain this phenomenon is not well established. Instead, some empirical models such as the Toth model are used to describe the isotherm without accounting for the presence of water. Recently, we have demonstrated that the isotherm equation of CO 2 sorption into strong-base anion exchange materials with quaternary ammonium can be derived from that of strong-base aqueous alkaline solutions by correcting for the drastic change in water activity and by including an appropriate parameterization of the water activity terms. In this paper, we generalize this model from quaternary ammonium to primary, secondary and tertiary amines either in solutions or as functional groups in polymer resins. For primary, secondary and tertiary amines, the isotherm equation can be derived by extending that of a weak-base aqueous alkaline solution such as aqueous ammonia. The model has been validated using experimental data of aqueous ammonia in literature. Furthermore, this general model even includes quaternary ammonium as a special limit. Hence, this general model offers a platform that can treat the isotherms of solid amines, aqueous amines and aqueous alkaline solutions in a unified way.

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

Integrated Renewable Combined Heat and Power for Ethanol

Conference presentation at 48th International Technical Conference on Clean Energy (Clearwater Clean Energy Conference), Clearwater, Florida, June 16–19, 2024. This project evaluates the technical and economic feasibility of small‑scale combined heat and power (CHP) systems using corn stover to support bioenergy with carbon capture and storage (BECCS) at ethanol facilities. The work includes resource characterization, pilot‑scale gasification and CO 2 capture testing to support techno‑economic analysis, economic evaluation of CHP deployment and potential carbon revenue, and life‑cycle assessment of gasification‑based CHP systems.

09 BIOMASS FUELS↗
DOE OSTI2023

Carbon Capture Design and Costing: Phase 2 (C3DC2) (Final Project Report)

ION Clean Energy’s (ION) advanced solvent is one of the leading solvent systems currently under development for post-combustion carbon dioxide (CO 2 ) capture. ION has partnered with Nebraska Power Public District (NPPD), Sargent & Lundy, Koch Modular Process Systems, and Siemens to design a commercial-scale (700 MW) capture system utilizing ION’s advanced solvent, ICE-21, retrofitted onto NPPD’s Gerald Gentleman Station in Sutherland, Nebraska, USA. The capture system was designed to take full advantage of the solvent benefits including an efficient physical plant layout, reduced energy requirements, less solvent degradation, lower emissions, and lower capital costs relative to systems built with DOE BBS case benchmark solvents. This Front-End Engineering Design (FEED) study also included an investigation of utilizing biomass co-combustion with the aim of reaching near-zero emissions for this coal-fired power generating unit. The targeted biomass was from local resources in Nebraska tied to the production of ethanol.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2024

Sulfur-Enriched Nanoporous Carbon: A Novel Approach to CO 2 Adsorption

Carbon dioxide (CO 2 ) intake plays a vital role in sustaining the environmental balance by influencing global carbon dynamics and climatic stability. This work addresses the production of sulfur-doped porous nanocarbons (SDCs) as prospective sorbents for CO 2 capture. SDCs were fabricated by utilizing coconut shell as a carbon precursor and potassium persulfate as both a chemical activating agent and a sulfur dopant. The incorporation of sulfur functionalities into carbon matrices creates structural variability and active sites, boosting CO 2 absorption capabilities. Sulfur's peculiar electrical structure allows greater intermolecular interactions with CO 2 , enhancing adsorption affinities. According to the experimental data, the CO 2 uptake was best measured as 3.37 mmol/g at 0(degrees)C and 1 bar and 2.56 mmol/g at 25 C-degrees and 1 bar. The results show that the higher porosity of SDC materials adds to a large amplification in the CO 2 uptake capability. The work underlines the delicate interaction between sulfur doping, morphological porosity, and surface reactivity in enhancing the effectiveness of CO 2 sequestration. SDC materials hold considerable promise in tackling the present ecological concerns and developing CO 2 collection techniques. The suggested single-step synthesis technique described here provides a sustainable and environmentally friendly method for synthesizing SDCs for carbon capture applications.

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

Nanoscale Hybrid Electrolytes with Viscosity Controlled Using Ionic Stimulus for Electrochemical Energy Conversion and Storage

As renewable energy is rapidly integrated into the grid, the challenge has become storing intermittent renewable electricity. Technologies including flow batteries and CO 2 conversion to dense energy carriers are promising storage options for renewable electricity. To achieve this technological advancement, the development of next generation electrolyte materials that can increase the energy density of flow batteries and combine CO 2 capture and conversion is desired. Liquidlike nanoparticle organic hybrid materials (NOHMs) composed of an inorganic core with a tethered polymeric canopy (e.g., polyetheramine (HPE)) have a capability to bind chemical species of interest including CO 2 and redox-active species. In this study, the unique response of NOHM-I-HPE-based electrolytes to salt addition was investigated, including the effects on solution viscosity and structural configurations of the polymeric canopy, impacting transport behaviors. The addition of 0.1 M NaCl drastically lowered the viscosity of NOHM-based electrolytes by up to 90%, reduced the hydrodynamic diameter of NOHM-I-HPE, and increased its self-diffusion coefficient, while the ionic strength did not alter the behaviors of untethered HPE. This study is the first to fundamentally discern the changes in polymer configurations of NOHMs induced by salt addition and provides a comprehensive understanding of the effect of ionic stimulus on their bulk transport properties and local dynamics. These insights could be ultimately employed to tailor transport properties for a range of electrochemical applications.

25 ENERGY STORAGE↗
DOE OSTI2024

High-throughput measurements of CO 2 permeance and solubility in ionic liquid reveal a synergistic role of ionic interactions and void fractions

The factors that govern CO 2 solubility in ionic liquids (ILs) are of great interest for the development of new materials for CO 2 capture and utilization. The cationic functional group (i.e., imidazolium, pyrrolidinium, pyridinium, etc.), alkyl chain length of cation, degree of fluorination of anion, anion size, and the void fraction in IL are known to influence CO 2 solubility. However, a comprehensive explanation of how these factors collectively affect CO 2 solubility has not been developed yet. This knowledge gap is largely attributed to the lack of CO 2 solubility data for IL structures other than imidazolium based ILs. We report here an automated high-throughput (HT) setup for the measurement of CO 2 solubility in room-temperature ILs (RTILs) combining six different anions and nine different cations for a total of 19 different specific ranges of RTILs. The HT setup first dispenses up to 200 µL of RTILs in a 96-well microtiter plate and then utilizes a robotic arm to measure cyclic voltammogram (CV) in each well using maneuverable Ag electrodes. The Cottrell analysis of the CO 2 reduction CV peak provides a direct measurement of CO 2 permeance in RTILs, which yields Henry’s constant from the estimated diffusion coefficient of CO 2 . Henry’s constants thus obtained are in very good agreement with those reported earlier. The measured CO 2 permeance and Henry’s constant of all RTILs seem to follow a first-order dependence on void fraction and a second-order dependence on electrostatic interaction between anion and cation of IL, with some synergistic dependence on the product of a void fraction and electrostatic interaction, making them two important descriptors for the design of novel ILs.

CO2 Solubility↗