Plasma-catalytic ammonia synthesis beyond thermal equilibrium on Ru-based catalysts in non-thermal plasma

Abstract

Mehta et al. 1 proposed that plasma-catalytic NH3 synthesis with excited N2 allows for conversions beyond thermal equilibrium. We show that this is indeed possible with experimental data for Ru-based...

Al2O3-Supported Transition Metals for Plasma-Catalytic NH3 Synthesis in a DBD Plasma: Metal Activity and Insights into Mechanisms

“…Of course, the yield and the concentration of NH 3 are directly related as shown in Equations ( 4) and (7). While other works report lower EC values, the respective NH 3 yields are often also very low (from <0.1 to 0.7%) and correspond to similarly low values of NH 3 concentrations (<1 vol%), as seen e.g., in [18,35,46,56] In our previous work, we demonstrated that a process of NH 3 production becomes plausible only if the NH 3 concentration in the reaction mixture is ≥1 vol% due to the 'hidden' additional energy costs required for product separation [16]. In this regard, our value of ca.…”

“…Moreover, different pathways leading from N 2 to NH 3 were investigated. Among these are reduction of the plasma-produced NO x to NH 3 [16,17], and direct reactions of N 2 with H 2 [18,19] or H 2 O [20][21][22], as also summarised in detail in recent reviews [23,24]. We show the possible pathways of the plasma-driven N 2 fixation in Figure 1.…”

“…DBD produces highly energetic, spatially and temporally non-uniform microdischarges (filaments) [28]. Therefore, the high energy density of the filaments allows excitation of molecules by plasma but limits the overall gas heating, thus reducing the potential thermal NH 3 decomposition [18]. Some of the first reports of PC NH 3 production from N 2 and H 2 in DBD describe reactors with Al 2 O 3 -coated inner walls of the reactor [29], as well as Ru deposited on the Al 2 O 3 inner walls [30].…”

“…In the last three years, the growing interest in PC NH 3 has led to numerous studies which attempted to discriminate between the plasma and thermal catalytic effects in PC, identify the mechanisms of PC NH 3 formation, and formulate the differences between thermal and plasma catalysis [13,18,37]. However, despite the substantial progress in the field of PC, many unknowns still linger.…”

Atmospheric Pressure DBD Plasma Ammonia Synthesis and Separation Process Design and Environmental Impact Assessment

“…Thus, process development has been the focus of the recent studies with H 2 generated electrochemically from water and then combined with N 2 in a conventional NH 3 synthesis process. , Plasma N 2 fixation into NH 3 , on the other hand, recently enjoyed a rejuvenation. Cold dielectric discharge barrier (DBD) plasma-enhanced catalytic NH 3 synthesis from N 2 and H 2 has been shown to take place at near room temperatures. − For example, an NH 3 synthesis rate of 471 μmol g –1 h –1 was reported recently using Ni/Al 2 O 3 as a catalyst with DBD plasma and significant work is currently taking place on exploring the DBD plasma-assisted catalytic NH 3 reaction ,− including elucidating the underlying mechanisms and reactive intermediates. − However, it is not yet clear whether plasma-based NH 3 synthesis will be the most feasible alternative for either centralized or decentralized ammonia production . This is due to the lack of process-wide models where integration of plasma reactors into the existing gas infrastructure can be assessed.…”