TY - JOUR
T1 - Plasma-catalytic ammonia synthesis in a dielectric barrier discharge reactor
T2 - A combined experimental study and kinetic modeling
AU - Andersen, J. A.
AU - Holm, M. C.
AU - van 't Veer, K.
AU - Christensen, J. M.
AU - Østberg, M.
AU - Bogaerts, A.
AU - Jensen, A. D.
N1 - Publisher Copyright:
© 2023 The Author(s)
PY - 2023
Y1 - 2023
N2 - Plasma-catalytic ammonia synthesis in a dielectric barrier discharge reactor has emerged as a possible route for electrification of nitrogen fixation. In this study, we use a combination of experiments and a plasma kinetic model to investigate the ammonia synthesis from N2 and H2, both with and without a solid packing material in the plasma zone. The effect of plasma power, feed flow rate, N2:H2 feed ratio, gas residence time, temperature, and packing material (MgAl2O4 alone or impregnated with Co or Ru) on the ammonia synthesis rate were examined in the experiments. The kinetic model was employed to improve our understanding of the ammonia formation pathways and identify possible changes in these pathways when altering the N2:H2 feed ratio. A higher NH3 synthesis rate was achieved when increasing the feed flow rate, as well as when increasing the gas temperature from 100 to 200 °C when a packing material was present in the plasma. At the elevated temperature of 200 °C, an optimum in the NH3 synthesis rate was observed at an equimolar feed ratio (N2:H2 = 1:1) for the plasma alone and MgAl2O4, while a N2-rich feed was favored for Ru/MgAl2O4 and Co/MgAl2O4. The optimum in the synthesis rate with the N2-rich feed, where high energy electrons are more likely to collide with N2, suggests that the rate-limiting step is the dissociation of N2 in the gas phase. This is supported by the kinetic model when packing material was used. However, for the plasma alone, the model found that the N2 dissociation is only rate limiting in H2-rich feeds, whereas the limited access to H in N2-rich feeds makes the hydrogenation of N species limiting.
AB - Plasma-catalytic ammonia synthesis in a dielectric barrier discharge reactor has emerged as a possible route for electrification of nitrogen fixation. In this study, we use a combination of experiments and a plasma kinetic model to investigate the ammonia synthesis from N2 and H2, both with and without a solid packing material in the plasma zone. The effect of plasma power, feed flow rate, N2:H2 feed ratio, gas residence time, temperature, and packing material (MgAl2O4 alone or impregnated with Co or Ru) on the ammonia synthesis rate were examined in the experiments. The kinetic model was employed to improve our understanding of the ammonia formation pathways and identify possible changes in these pathways when altering the N2:H2 feed ratio. A higher NH3 synthesis rate was achieved when increasing the feed flow rate, as well as when increasing the gas temperature from 100 to 200 °C when a packing material was present in the plasma. At the elevated temperature of 200 °C, an optimum in the NH3 synthesis rate was observed at an equimolar feed ratio (N2:H2 = 1:1) for the plasma alone and MgAl2O4, while a N2-rich feed was favored for Ru/MgAl2O4 and Co/MgAl2O4. The optimum in the synthesis rate with the N2-rich feed, where high energy electrons are more likely to collide with N2, suggests that the rate-limiting step is the dissociation of N2 in the gas phase. This is supported by the kinetic model when packing material was used. However, for the plasma alone, the model found that the N2 dissociation is only rate limiting in H2-rich feeds, whereas the limited access to H in N2-rich feeds makes the hydrogenation of N species limiting.
KW - Ammonia Synthesis
KW - Chemical Kinetics Model
KW - DBD Plasma
KW - Micro-Discharges
KW - Plasma Catalysis
U2 - 10.1016/j.cej.2023.141294
DO - 10.1016/j.cej.2023.141294
M3 - Journal article
AN - SCOPUS:85146078489
SN - 1385-8947
VL - 457
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
M1 - 141294
ER -