Electromagnetic field-assisted ammonia synthesis developed for potential industrialization

Ammonia (NH3) stands as a vital industrial chemical, playing a pivotal role in nitrogenous fertilizer production and holding promise as an eco-friendly fuel for the future. Presently, industrial ammonia synthesis hinges on the Haber-Bosch method, involving the reaction of hydrogen and nitrogen, often derived from fossil fuels, at high temperatures (~500 °C) and pressures (>15 MPa). This process consumes roughly 2% of the world’s power and contributes around 1.5% of global greenhouse gas emissions.

In a noteworthy development, a team from Tianjin University in China has introduced an Electromagnetic Field (EMF)-assisted approach to the Haber-Bosch technique for ammonia synthesis, executed with off-the-shelf iron-based catalysts. Notably, the introduction of EMF lowers the initiation temperature to 100 °C, a substantial reduction compared to the conventional method, which operates at 300 °C.

In a practical large-scale experiment employing 80 grams of commercial catalysts, the EMF-assisted Haber-Bosch technique delivers a fivefold increase in ammonia yield while decreasing energy consumption by approximately 2.7 times. This impressive catalytic performance boost is attributed to the EMF’s ability to facilitate greater electron transfer from iron orbitals to nitrogen triple bonds (N≡N) in both side-on and end-on adsorption modes.

(a) Ammonia concentration under different temperatures with and without an EMF at 1 MPa. (b) Comparison of ammonia concentration and energy cost for the scale-up experiment at 200 ℃ and 1 MPa with and without the EMF. (c) Adsorption energy of N2 on Fe(110) with and without an EMF (1 V Å-1). Atomic structure of N2 side-on adsorption on the Fe(110) surface with (d) and without (e) an external electric field and N2 end-on adsorption on the Fe(110) surface with (f) and without (g) an external electric field. Gray ball: Fe, blue ball: N. Charge density difference of N2 side-on adsorption with (h)and without (i) an external electric field and N2 end-on adsorption with (j) and without (k) an external electric field. The isosurface value is 0.003 e Å-1The yellow isosurface represents electron accumulation, and cyan denotes electron depletion. Credit: ©Science China Press
A pilot-scale system includes alkaline water electrolysis equipment, air PSA separation equipment and EMF-assisted H-B equipment. Credit: Science China Press

To take their innovation to the next level, the team has established a pilot-scale system at Tianjin University with an annual production capacity of 10,000 kg, marking a significant stride towards transitioning EMF-assisted thermal catalysis from the lab to industrial applications.

The researchers are now conducting further scale-up studies on EMF-assisted thermal catalysis in Qinghai Province, known for its abundant renewable energy resources. This endeavor aims to pave the way for addressing the challenges of large-scale storage and transportation of renewable energy, contributing to the realization of the “dual carbon” goal. Their findings have been published in the esteemed journal Science Bulletin.

Source: Science China Press

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