Kinetics of absorption of carbon monoxide in aqueous solutions of sodium hydroxide and aqueous calcium hydroxide slurries

Patwardhan, Anand; Sharma, Man Mohan

doi:10.1021/ie00085a002

Cited by 8 publications

(6 citation statements)

References 3 publications

(3 reference statements)

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“…Although previous reports propose the formation of CO as a reaction product, we did not observe any CO in the gas phase, which is consistent with the mechanism proposed here. Alternatively, the yields were either below the detection limit or any CO formed reacted rapidly with OH – to yield the formate ( CO + OH – → HCOO – ), which was observed in experiments with NaOH amendment.…”

Section: Resultsmentioning

confidence: 99%

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA)

Austin,

Purohit,

Thomsen

et al. 2024

Environ. Sci. Technol.

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Per-and polyfluoroalkyl substances (PFAS) have received increased attention due to their environmental prevalence and threat to public health. Trifluoroacetic acid (TFA) is an ultrashortchain PFAS and the simplest perfluorocarboxylic acid (PFCA). While the US EPA does not currently regulate TFA, its chemical similarity to other PFCAs and its simple molecular structure make it a suitable model compound for studying the transformation of PFAS. We show that hydrothermal processing in compressed liquid water transforms TFA at relatively mild conditions (T = 150−250 °C, P < 30 MPa), initially yielding gaseous products, such as CHF 3 and CO 2 , that naturally aspirate from the solution. Alkali amendment (e.g., NaOH) promotes the mineralization of CHF 3 , yielding dissolved fluoride, formate, and carbonate species as final products. Fluorine and carbon balances are closed using Raman spectroscopy and fluoride ion selective electrode measurements for experiments performed at alkaline conditions, where gas yields are negligible. Qualitative FTIR gas analysis allows for establishing the transformation pathways; however, the F-balance could not be quantitatively closed for experiments without NaOH amendment. The kinetics of TFA transformation under hydrothermal conditions are measured, showing little to no dependency on NaOH concentration, indicating that the thermal decarboxylation is a rate-limiting step. A proposed TFA transformation mechanism motivates additional work to generalize the hydrothermal reaction pathways to other PFCAs.

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Section: Resultsmentioning

confidence: 99%

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA)

Austin,

Purohit,

Thomsen

et al. 2024

Environ. Sci. Technol.

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show abstract

“…Greater diffusivity makes species transfer easier in the aqueous phase. It is noted that the viscosity of the aqueous solution increases with electrolyte addition, [30] and the diffusivity then decreases as the viscosity increases. For example, the diffusivity of species A decreases even for a 0.1 mol/L sodium hydroxide solution, compared to pure water.…”

Section: Mass Transfer Without Chemical Reactionmentioning

confidence: 99%

CFD simulation of mass transfer intensified by chemical reactions in slug flow microchannels

Zhang

et al. 2015

Can J Chem Eng

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Based on computational fluid dynamics (CFD), the liquid-liquid mass transfer in a slug flow through circular capillaries was studied. In order to save computational resources and time, the numerical simulations were carried out in a unit cell containing an aqueous slug and an organic one with a moving frame of reference. The flow field within individual slugs and interphase mass transfer with reactions between two consecutive slugs were discussed. Concentration fields were obtained to describe the mass transfer between the liquid phases. In addition, the effects of fluid diffusivity D on mass transfer coefficient k L a and the chemical species distribution were studied in detail. In general, the internal circulations inside individual slugs were displayed by the motion paths of mass transfer components. Furthermore, the mass transport process is enhanced by the alkaline hydrolysis reaction as confirmed by the so-called enhancement factor E. Finally, the simulation results showed close agreement with published experimental data.

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“…9 In comparison to CO 2 carbonation, the analogous reaction of CO with OH − to form formate (HCO 2 − ) is very slow, which enables the use of alkaline electrolytes in CO electrolysis to achieve substantially lower cell voltages with minimal nonfaradaic parasitic losses. 10 Although this two-step strategy nominally has more process complexity, it can in principle provide higher overall energy conversion efficiency and carbon yield for the CO 2 to C 2+ conversion. 11−13 The engineering challenges of COR differ from CO2R because of differences in the gas solubilities, reaction rates, product distributions, and tolerance to electrolyte composition.…”

Section: Introductionmentioning

confidence: 99%

Continuum Model for Optimizing CO Reduction Gas Diffusion Electrodes

Disselkoen,

Rabinowitz,

Mani

et al. 2024

ACS Sustainable Chem. Eng.

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Carbon monoxide electrolysis has the potential to unlock new routes to sustainable C 2+ chemicals. Improvements to CO reduction (COR) gas diffusion electrodes (GDEs) are critical for advancing CO electrolysis cells, but a comprehensive understanding of COR GDEs remains elusive because of the complex interplay of physical and chemical processes under operating conditions and the difficulty of experimentally probing the heterogeneous environment of a GDE. In this study, we build a model for COR GDEs that includes fully coupled gas and ion transport and competing electrokinetic reactions. The transport and electrokinetic equations are solved in two dimensions to calculate critical COR figures of merit across multiple operating parameters including current density, flow rate, pressure, temperature, and electrochemically active surface area (ECSA). We validate our model by showing agreement with experimental data for steady-state CO electrolysis at various pressures and flow rates and then apply it to see how the figures of merit depend on the operating parameters over a wide range of values. We demonstrate that increasing the cell pressure above ambient and augmenting the ECSA of the catalyst are two effective strategies to improve cathode performance.

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Kinetics of absorption of carbon monoxide in aqueous solutions of sodium hydroxide and aqueous calcium hydroxide slurries

Cited by 8 publications

References 3 publications

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA)

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA)

CFD simulation of mass transfer intensified by chemical reactions in slug flow microchannels

Continuum Model for Optimizing CO Reduction Gas Diffusion Electrodes

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