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	Author	Andersen, Ja.; van 't Veer, K.; Christensen, Jm.; Østberg, M.; Bogaerts, A.; Jensen, Ad.
	Title	Ammonia decomposition in a dielectric barrier discharge plasma: Insights from experiments and kinetic modeling			Type	A1 Journal article
	Year	2023	Publication	Chemical engineering science	Abbreviated Journal
	Volume	271	Issue		Pages	118550
	Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
	Abstract	Utilizing ammonia as a storage medium for hydrogen is currently receiving increased attention. A possible method to retrieve the hydrogen is by plasma-catalytic decomposition. In this work, we combined an experimental study, using a dielectric barrier discharge plasma reactor, with a plasma kinetic model, to get insights into the decomposition mechanism. The experimental results revealed a similar effect on the ammonia conversion when changing the flow rate and power, where increasing the specific energy input (higher power or lower flow rate) gave an increased conversion. A conversion as high as 82 % was achieved at a specific energy input of 18 kJ/Nl. Furthermore, when changing the discharge volume from 31 to 10 cm3, a change in the plasma distribution factor from 0.2 to 0.1 was needed in the model to best describe the conversions of the experiments. This means that a smaller plasma volume caused a higher transfer of energy through micro-discharges (non-uniform plasma), which was found to promote the decomposition of ammonia. These results indicate that it is the collisions between NH3 and the high-energy electrons that initiate the decomposition. Moreover, the rate of ammonia destruction was found by the model to be in the order of 1022 molecules/(cm3 s) during the micro-discharges, which is 5 to 6 orders of magnitude higher than in the afterglows. A considerable re-formation of ammonia was found to take place in the afterglows, limiting the overall conversion. In addition, the model revealed that implementation of packing material in the plasma introduced high concentrations of surface-bound hydrogen atoms, which introduced an additional ammonia re-formation pathway through an Eley-Rideal reaction with gas phase NH2. Furthermore, a more uniform plasma is predicted in the presence of MgAl2O4, which leads to a lower average electron energy during micro-discharges and a lower conversion (37 %) at a comparable residence time for the plasma alone (51 %).
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000946293200001	Publication Date	2023-02-09
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0009-2509	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	4.7	Times cited		Open Access	OpenAccess
	Notes	We thank Topsoe A/S for providing the packing material used, the research group PLASMANT (UAntwerpen) for sharing their plasma kinetic model and allowing us to perform the calculations on their clusters, and the Department of Chemical and Biochemical Engineering, Technical University of Denmark, for funding this project.			Approved	Most recent IF: 4.7; 2023 IF: 2.895
	Call Number	PLASMANT @ plasmant @c:irua:195204			Serial	7237
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	Author	Andersen, Ja.; Holm, Mc.; van 't Veer, K.; Christensen, Jm.; Østberg, M.; Bogaerts, A.; Jensen, Ad.
	Title	Plasma-catalytic ammonia synthesis in a dielectric barrier discharge reactor: A combined experimental study and kinetic modeling			Type	A1 Journal Article
	Year	2023	Publication	Chemical engineering journal	Abbreviated Journal
	Volume	457	Issue		Pages	141294
	Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
	Abstract	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 tem-perature 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.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	001058978000001	Publication Date	2023-01-05
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1385-8947	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	15.1	Times cited		Open Access	OpenAccess
	Notes	We thank Topsoe A/S for providing the catalytic materials used in the study, the research group PLASMANT (University of Antwerp) for sharing their plasma kinetic model and allocating time on their cluster for the calculations, and the Department of Chemical and Biochemical Engineering (Technical University of Denmark) for funding the project.			Approved	Most recent IF: 15.1; 2023 IF: 6.216
	Call Number	PLASMANT @ plasmant @c:irua:195877			Serial	7234
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	Author	Andersen, J.A.; Christensen, J.M.; Østberg, M.; Bogaerts, A.; Jensen, A.D.
	Title	Plasma-catalytic ammonia decomposition using a packed-bed dielectric barrier discharge reactor			Type	A1 Journal article
	Year	2022	Publication	International Journal Of Hydrogen Energy	Abbreviated Journal	Int J Hydrogen Energ
	Volume	47	Issue	75	Pages	32081-32091
	Keywords	A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
	Abstract	Plasma-catalytic ammonia decomposition as a method for producing hydrogen was studied in a packed-bed dielectric barrier discharge (DBD) reactor at ambient pressure and a fixed plasma power. The influence of packing the plasma zone with various dielectric materials, typically used as catalyst supports, was examined. At conditions (21 W, 75 Nml/min NH3) where an NH3 conversion of 5% was achieved with plasma alone, an improved decomposition was found when introducing dielectric materials with dielectric constants between 4 and 30. Of the tested materials, MgAl2O4 yielded the highest conversion (15.1%). The particle size (0.3-1.4 mm) of the MgAl2O4 packing was found to have a modest influence on the conversion, which dropped from 15.1% to 12.6% with increasing particle size. Impregnation of MgAl2O4 with different metals was found to decrease the NH3 conversion, with the Ni impregnation still showing an improved conversion (7%) compared to plasma-only. The plasma-assisted ammonia decomposition occurs in the gas phase due to micro-discharges, as evident from a linear correlation between the conversion and the frequency of micro-discharges for both plasma alone and with the various solid packing materials. The primary function of the solid is thus to facilitate the gas phase reaction by assisting the creation of micro-discharges. Lastly, insulation of the reactor to raise the temperature to 230 degrees C in the plasma zone was found to have a negative effect on the conversion, as a change from volume discharges to surface discharges occurred. The study shows that NH3 can be decomposed to provide hydrogen by exposure to a non-thermal plasma, but further developments are needed for it to become an energy efficient technology. (C)2022 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000865421200012	Publication Date	2022-08-17
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0360-3199	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	7.2	Times cited		Open Access	OpenAccess
	Notes				Approved	Most recent IF: 7.2
	Call Number	UA @ admin @ c:irua:191512			Serial	7191
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	Author	Andersen, Ja.; Christensen, Jm.; Østberg, M.; Bogaerts, A.; Jensen, Ad.
	Title	Plasma-catalytic dry reforming of methane: Screening of catalytic materials in a coaxial packed-bed DBD reactor			Type	A1 Journal article
	Year	2020	Publication	Chemical Engineering Journal	Abbreviated Journal	Chem Eng J
	Volume	397	Issue		Pages	125519
	Keywords	A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
	Abstract	The combination of catalysis with non-thermal plasma is a promising alternative to thermal catalysis. A dielectric-barrier discharge reactor was used to study plasma-catalytic dry reforming of methane at ambient pressure and temperature and a ﬁxed plasma power of 45 W. The eﬀect of diﬀerent catalytic packing materials was evaluated in terms of conversion, product selectivity, and energy eﬃciency. The conversion of CO2 (~22%) and CH4 (~33%) were found to be similar in plasma-only and when introducing packing materials in plasma. The main reason is the shorter residence time of the gas due to packing geometry, when compared at identical ﬂow rates. H2, CO, C2-C4 hydrocarbons, and oxygenates were identiﬁed in the product gas. High selectivity towards H2 and CO were found for all catalysts and plasma-only, with a H2/CO molar ratio of ~0.9. The lowest syngas selectivity was obtained with Cu/Al2O3 (~66%), which instead, had the highest alcohol selectivity (~3.6%).
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000542296100011	Publication Date	2020-05-17
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	1385-8947	ISBN		Additional Links	UA library record; WoS full record; WoS citing articles
	Impact Factor	15.1	Times cited		Open Access
	Notes	Department of Chemical and Biochemical Engineering, Technical University of Denmark; We thank Haldor Topsoe A/S for providing all the catalytic materials used and the Department of Chemical and Biochemical Engineering, Technical University of Denmark, for funding this project.			Approved	Most recent IF: 15.1; 2020 IF: 6.216
	Call Number	PLASMANT @ plasmant @c:irua:170613			Serial	6406
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