Toward a Mechanistic Understanding and Optimization of Molten Alkali Metal Borates (A_xB_1–xO_1.5–x) for High-Temperature CO₂ Capture

Abstract

Carbon capture, utilization, and storage technologies are needed to meet carbon emission reduction targets and prepare the energy industry for a carbon constrained world. Recent breakthroughs have identified the first liquid phase sorbents for CO2 capture at high temperatures. In this work, the material design space of the molten alkali metal borates (A x B1–x O1.5–x ) is explored finding sodium and sodium-rich lithium–sodium borates with a mixing ratio, x, of around 0.75 to be optimal. A mechanistic understanding of the material is developed through exploration of the sodium borate phase diagram, the development of a kinetic equilibrium model, and estimation of effective diffusion coefficients. Interesting features of the sorbents, such as the proposed formation of dicarbonate ions and counter-intuitive trends in the diffusion coefficient, are identified and explained with implications for the design of future high temperature carbon capture facilities discussed.

Sorbents for the Capture of CO2 and Other Acid Gases: A Review

“…Molten salts are a recently discovered class of liquid phase sorbent that operate at elevated temperatures. A number of advantages of certain salts for CO 2 capture, including high capacities, fast kinetics, and excellent stability, have been demonstrated with molten alkali metal borates. ,, These materials may be tuned for entirely liquid phase reactions or for the phase change precipitation of reaction products, introducing opportunities to handle captured SO x and NO x impurities . As high temperature liquid phase materials, these sorbents are uniquely positioned, although a number of uncertainties and challenges remain around their corrosive nature and their practical operation at scale. , …”

Net-Negative Emissions through Molten Sorbents and Bioenergy with Carbon Capture and Storage

“…31 Equilibrium diagrams, presented in Figures 3 and S2, plot the mole ratio of CO 2 to inert gas (mostly nitrogen in the absorber and steam in the desorber) in the gas phase (Y) against the mole ratio of CO 2 to liquid (sorbent) in the liquid phase (X). Equilibrium curves, derived from concentration isotherms, 23 define the relationship between X and Y at the two temperatures of interest, 600 and 650 °C.…”

“…In this work, we explore how a new class of molten salt-based sorbent materials could contribute to increasing the techno-economic feasibility of BECCS. Molten sorbents are liquids under high temperatures at which CO 2 is exposed to the sorbent and separated from the flue gas stream, typically 600–700 °C. , Significant opportunities exist despite the fact that molten sorbents are at a lower technology readiness level than other sorbents. Advantages of molten sorbents include high capacities, fast kinetics, excellent stability, combined capture of multiple acid gases, and low energy penalties. , The work presented here follows the principles presented in our previous analyses, which proposed a conceptual design for a large 800 MW e coal fired power plant.…”

“…Molten sorbents are liquids under high temperatures at which CO 2 is exposed to the sorbent and separated from the flue gas stream, typically 600−700 °C. 22,23 Significant opportunities exist despite the fact that molten sorbents are at a lower technology readiness level than other sorbents. Advantages of molten sorbents include high capacities, fast kinetics, excellent stability, combined capture of multiple acid gases, and low energy penalties.…”

Interface engineering of metal nanomaterials enhance the electrocatalytic water splitting and fuel cell performance

“…[ 5,6 ] Carbon dioxide capture using renewable energy sources is a useful way to produce storable carbon‐neutral fuels and to prevent global warming. [ 7,8 ] Likewise, the electrocatalytic nitrogen reduction reaction utilizing renewable energy sources is a sustainable and economically viable process for production of fertilizers sustainably and commodity chemicals, which is a promising process for replacing Haber‐Bosch process in the future. [ 9,10 ] The main factor to develop those electrochemical energy devices is the electrocatalysts with an excellent activity and selectivity for the chemical transformations involved.…”