Ammonia Synthesis Using a Membrane Dielectric-Barrier Discharge Reactor: Design and Performance Assessment

Ammonia is primarily used for agricultural fertilizer production to sustain 40% of the global population, and it can have a primary role as a carbon-free fuel in hard-to-decarbonize sectors, such as long-haul aviation and maritime transport. Ammonia synthesis using non-thermal plasma has the potential to be more viable than established approaches (e.g., the Haber-Bosch process), particularly for distributed operations [1]–[3]. This study presents the design and performance assessment of a membrane Dielectric-Barrier Discharge (DBD) reactor for ammonia synthesis from nitrogen
$(\mathrm{N}_{2})$
and hydrogen
$(\mathrm{H}_{2})$
. The reactor uses a porous alumina membrane that fulfills the dual role of dielectric barrier and of separator of
$\mathrm{N}_{2}$
and
$\mathrm{H}_{2}$
streams. The latter allows greater resident time for N
2
to decompose together with distributed availability of
$\mathrm{H}_{2}$
, potentially leading to higher ammonia production. The performance assessment of the reactor encompasses two operation modes: (1) standard DBD (with non-porous dielectric) and (2) membrane DBD (with porous dielectric). Computational modelling is used to determine internal reactor temperature and gas velocity as operational characteristics. Optical spectroscopy is used to determine electron and excitation temperatures as well as electron number density. The characterization of the reactor operation includes electrical signals, temperature, optical visualization, and chemical analyses of gas products through Fourier-transform infrared spectroscopy (FTIR). The results reveal that the maximum energy yield is around
$0.30 \mathrm{g}-\text{NH}_{3}/\text{kWh}$
obtained for the highest voltage level under membrane DBD operation, whereas the maximum yield under standard DBD operation is
$0.10 \mathrm{g}-\text{NH}_{3}/\text{kWh}$
. The assessment indicates that membrane DBD can improve the performance of DBD-based ammonia synthesis.