Synergetic NH₃ absorption properties of the NaBH₄-LiBH₄ mixed system

Area of Science:

• Materials Science
• Chemical Engineering
• Inorganic Chemistry

Background:

• Ammonia (NH₃) is a key chemical feedstock and potential hydrogen storage medium.
• Borohydrides are investigated for their potential in gas absorption and storage applications.
• Understanding gas-material interactions is crucial for developing efficient storage solutions.

Purpose of the Study:

• To investigate the ammonia absorption characteristics of sodium borohydride (NaBH₄) and lithium borohydride (LiBH₄).
• To explore the synergistic effects of mixed borohydrides on ammonia absorption and liquefaction.
• To analyze the in situ kinematic viscosity of liquefied borohydride-ammonia systems.

Main Methods:

• Gas absorption experiments were conducted at pressures below and above 100 kPa.
• The phase behavior of NaBH₄, LiBH₄, and mixed borohydrides upon ammonia absorption was observed.
• In situ kinematic viscosity measurements were performed during the ammonia absorption process.

Main Results:

• NaBH₄ did not absorb NH₃ below 100 kPa but liquefied upon absorption.
• LiBH₄ absorbed NH₃ at pressures below 100 kPa.
• Mixed borohydrides exhibited synergistic NH₃ absorption at low pressures and liquefied above 100 kPa, with viscosity analyzed in situ.

Conclusions:

• Mixed borohydrides demonstrate enhanced ammonia absorption capabilities due to synergistic effects.
• The liquefaction behavior of borohydrides under ammonia pressure is pressure-dependent.
• In situ viscosity analysis provides insights into the fluid dynamics of these systems.