Dr. Prince Nana AMANIAMPONG, prince.nana.amaniampong@univ-poitiers.fr
CNRS Chargé de Recherche (CRCN)
Bâtiment B1, Rue Marcel Doré, TSA41105
86073 – Poitiers Cedex 9 (France)
Popular version of 1pPA1 – Ammonia chemistry: Sounds better with ultrasound
Presented Monday morning, May 23, 2022
182nd ASA Meeting
Click here to read the abstract
Hydrazine (N2H4) is a chemical of outmost importance in the chemical industry. The global hydrazine market was valued at 510.95 million USD in 2020, and is projected to reach 806.09 million by 2030, mostly boosted by the growing need of our society for the manufacture of polymer foams and agrochemicals. Moreover, hydrazine is used in space vehicles in the form of propellant to reduce the overall concentration of dissolved oxygen. The direct production of hydrazine from ammonia (NH3) is economically and environmentally highly attractive, but it remains a very difficult task. One of the reason stems from the high bond dissociation energy of N-H bond in NH3 (435 kJ/mol), requiring harsh conditions of temperature and pressure, which are not compatible with the stability of hydrazine. Indeed the composition of hydrazine is thermodynamically more favorable than the conversion of ammonia to hydrazine, making the accumulation of hydrazine scientifically challenging.
In this work, we show that cavitation bubbles created by ultrasonic irradiation of aqueous NH3 at a high frequency, act as micro-reactors to activate and convert NH3 to amino species, without assistance of any catalyst, yielding hydrazine at the bubble-liquid interface (Figure 1). The compartmentation of the in-situ produced hydrazine in the bulk solution, which is maintained close to 30 °C, advantageously prevents its thermal degradation, a recurrent problem faced by previous technologies.
Figure 1. Cavitation bubbles act as micro-reactors to activate ammonia towards hydrazine formation.
With this technology, a maximum hydrazine production rate of 0.17 mmol.L-1.h-2 in 7 wt. % ammonia solution was achieved (Figure 2). This work opens up new avenues toward the production of hydrazine for industrial and commercial applications using high frequency ultrasound activation technologies.
Figure 2. Effect of NH3 concentration on the formation of hydrazine (525 kHz, 0.17 W/mL, 30 °C)
This is has been recently published in Angewandte Chemie International Edition, Anaelle Humblot et al., 60, 48, 25230-25234 (doi.org/10.1002/anie.202109516) and was also highlighted as the front cover image of the issue.