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ICPT-AP System concept/ Design

Electrochemical synthesis of ammonia using a cell with a Nafion membrane and SmFe0.7Cu0.1Ni0.2 cathode at atmospheric pressure and lower temperature

To produce Ammonia from Hydrogen and Nitrogen.

Electrochemical methods of ammonia synthesis have been most widely studied. It is recognized that Nafion is the best polymer proton exchange membrane.

FreeCAD File (2022/11/01)

 

Flow Chart of Electrochemical Synthesis

 

Flow chart version 29.12.2022

Characterization

Ammonia synthesis and measurement

Wet H2 (the gas is bubbled through distilled water at 25℃ before entering the reactor, since water vapour may provide some protons[13] and increase the conductance and the rate of evolution of ammonia) was supplied to the anode, while dry N2 was supplied to the cathode.

The flow velocities of wet H2 and dry N2 are 30 mL·min−1. The vent gas from the cathode is absorbed by dilute H2SO4 (10 mL, pH 3.85) for 10 min under the closed circuit conditions. When Nessler’s reagent was added to the solution, a stable yellow color appeared immediately, which confirmed the presence of NH4+ in the solution. The concentration of NH4+ in the solution is determined by spectrophotometry[14] using a standard curve method in order to calculate the rate of ammonia synthesis.

NH3 Detection The amounts of NH3 trapped in the acid solutions are determined by indophenol and Nessler methods.

  • For the indophenol method, 1 mL of an aqueous 0.64 M C6H5OH, 0.38 M NaOH, and 1.3 mM C5FeN6Na2O solution was mixed with 1 mL of 55 mM NaOCl and 0.75 M NaOH prior to NH3 Then, 1 mL of either a standard NH3 solution (a known quantity of NH4Cl in an aqueous 10 mM H2SO4 solution) or the NH3- containing acid trap solution was added to the indophenol solution after dilution with aqueous 0.1 M KOH. The dissolved NH4+ ions were quantified by assessing the absorbance at 633 nm using UV-Vis spectroscopy. The measurements were calibrated by subtracting the background absorbance measured at 875 nm.
  • In the Nessler method, the acid-trapped-NH3 solution or the standard NH4OH solution was diluted in aqueous 90 mM K2HgI4 (Nessler reagent, Sigma Aldrich) and 0.1 M KOH before spectroscopic analysis. The absorbance measured at approximately 375 nm (corrected using the background at 700 nm) was used to determine the NH4+

For both the indophenol and Nesseler NH3 detection methods, standard calibration curves were obtained using known amounts of NH4Cl or NH4OH, respectively.