An official website of the United States government
Abstract Affordable synthetic ammonia (NH3) enables the production of nearly half of the food we eat and is emerging as a renewable energy carrier. Sodium‐promoted chemical looping NH3synthesis at atmospheric pressure using manganese (Mn) is here demonstrated. The looping process may be advantageous when inexpensive renewable hydrogen from electrolysis is available. Avoiding the high pressure of the Haber‐Bosch process by chemical looping using earth‐abundant materials may reduce capital cost, facilitate intermittent operation, and allow operation in geographic areas where infrastructure is less sophisticated. At this early stage, the data suggest that 0.28 m3of a 50 % porosity solid Mn bed may suffice to produce 100 kg NH3per day by chemical looping, with abundant opportunities for improvement.
more »
« less
High‐Throughput Analysis of Materials for Chemical Looping Processes
Abstract Chemical looping is a promising approach for improving the energy efficiency of many industrial chemical processes. However, a major limitation of modern chemical looping technologies is the lack of suitable active materials to mediate the involved subreactions. Identification of suitable materials has been historically limited by the scarcity of high‐temperature (>600 °C) thermochemical data to evaluate candidate materials. An accuratethermodynamic approach is demonstrated here to rapidly identify active materials which is applicable to a wide variety of chemical looping chemistries. Application of this analysis to chemical looping combustion correctly classifies 17/17 experimentally studied redox materials by their viability and identifies over 1300 promising yet previously unstudied active materials. This approach is further demonstrated by analyzing redox pairs for mediating a novel chemical looping process for producing pure SO2from raw sulfur and air which could provide a more efficient and lower emission route to sulfuric acid. 12 promising redox materials for this process are identified, two of which are supported by previous experimental studies of their individual oxidation and reduction reactions. This approach provides the necessary foundation for connecting process design with high‐throughput material discovery to accelerate the innovation and development of a wide range of chemical looping technologies.
more »
« less
- PAR ID:
- 10456674
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Energy Materials
- Volume:
- 10
- Issue:
- 27
- ISSN:
- 1614-6832
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Over the past two decades, chemical looping combustion (CLC) has been extensively investigated as a promising means to produce electric power while generating a concentrated carbon dioxide stream for sequestration. We note that the chemical looping strategy can be extended well outside of combustion-based carbon capture. In fact, application of the chemical looping strategy in areas beyond combustion can result in somewhat unexpected energy and carbon dioxide savings without producing a concentrated CO2 stream at all. Furthermore, it allows the looping-based technologies to tap into applications such as chemical production – a $4 trillion per year industrial sector with high energy and carbon intensities. The key resides in the design of effective oxygen carriers, also known as redox catalysts in the context of selective chemical conversion through chemical looping catalysis (CLCa). This contribution focuses on the design and applications of mixed oxides as multi-function reaction media in CLCa. Since typical mixed oxide oxygen carriers tend to be nonselective for hydrocarbon conversion, the first part of this article presents generalized design principles for surface modification of mixed oxides to improve their selectivity and catalytic activity. Applications of these redox catalysts in chemical looping – oxidative dehydrogenation (CL-ODH) of a variety of light alkanes and alkyl-benzenes are presented. This is followed with a discussion of computation assisted mixed oxide design based upon thermodynamic criteria. Finally, a few new directions for the chemical looping technologies are introduced.more » « less
-
Thermochemical splitting of carbon dioxide to carbon-containing fuels or value-added chemicals is a promising method to reduce greenhouse effects. In this study, we propose a novel process for synchronous promotion of chemical looping-based CO 2 splitting with biomass cascade utilization. The superiority of the process is reflected in (1) a biomass fast pyrolysis process is carried out for syngas, phenolic-rich bio-oil, and biochar co-production with oxygen carrier reduction; (2) the reduced oxygen carrier and the biomass-derived biochar were both applied for CO 2 splitting during the oxygen carrier oxidation stage with carbon monoxide production as well as oxygen carrier re-oxidation; (3) the redox looping of the oxygen carrier was found to synchronously promote the comprehensive utilization of biomass and CO 2 splitting to CO. Various characterizations e.g. HRTEM- and SEM-EDX mapping, H 2 -TPR, CO 2 -TPO, XRD, XPS, N 2 nitrogen adsorption and desorption isotherm tests, Mössbauer, etc. were employed to elucidate the aerogels' microstructures, phase compositions, redox activity, and cyclic stability. Results indicate that the Ca 2 Fe 2 O 5 aerogel is a promising initiator of the proposed chemical looping process from the perspectives of biomass utilization efficiency, redox activity, and cyclic durability.more » « less
-
Structurally stabilized composites are promising for using phase change materials in high‐temperature thermal energy storage (TES). However, conventional skeleton materials, which typically comprise 30–50 wt% of the composite, mainly provide sensible heat storage and contribute minimally to overall energy density. This study introduces a new class of redox‐active oxide‐molten salt (ROMS) composites that overcome this limitation by combining sensible, latent, and thermochemical heat storage in a single particle. Specifically, porous, redox‐active Ca2AlMnO5+δ(CAM) complex oxide particles were demonstrated as a suitable support matrix, with the pores filled by eutectic NaCl/CaCl2salt. X‐ray diffraction confirms excellent phase compatibility between CAM and the salt. Scanning electron microscopy/energy dispersive X‐ray spectroscopy and nano X‐ray tomography show good salt infiltration and wettability within the CAM pores. Thermogravimetric analysis reveals that a 60 wt% CAM/40 wt% salt composite achieves an energy density of 267 kJ kg−1over a narrow 150 °C window, with ≈50 kJ kg−1from thermochemical storage. Additionally, the composite shows higher thermal conductivity than salt alone, enabling faster energy storage and release. ROMS composites thus represent a novel and efficient solution for high‐performance TES.more » « less
-
Redox‐active electrosorbents are promising platforms for selective separations. However, these platforms face intrinsic challenges in extracting multiple species simultaneously, as their binding mechanisms are typically tailored to separate a single ion preferentially. Here, bipolar electrochemistry is leveraged to introduce a new strategy for the multiplexed use of redox‐active and capacitive materials for separations. Using polyvinyl ferrocene (PVF)‐, Prussian blue analog (PBA)‐functionalized, and carbon‐based electrodes, multicomponent separations within a modular bipolar electrode (BPE) platform are demonstrated. The multiplexed BPE system provides distinct electrochemical environments within each BPE pair, enabling parallel selective separations. With three identical PVF BPEs, arsenic uptake increased linearly from 41.4 to 115.4 mgAsgPVF−1, highlighting the scalability of the system. Moreover, deploying three distinct BPE pairs—PBA, PVF, and carbon—enables simultaneous potassium recovery (11.0 mg g−1), arsenic removal (19.8 mg g−1), and desalination (4.2 mg g−1) from secondary wastewater, demonstrating real‐world applicability. This wireless, membraneless architecture enables process‐intensified selective separations by precisely controlling local electric fields on individual redox‐active materials, facilitating electrosorption and regeneration across diverse BPE systems within a unified process.more » « less
