One-Step Synthesis of Ammonia Directly from Wet Air/N₂ by Plasma Combined with a γ-Al₂O₃ Catalyst

Abstract

The conventional Haber−Bosch NH 3 synthesis process requires high temperatures and pressures, resulting in a high carbon footprint and the need to develop alternative NH 3 synthesis methods. Accordingly, plasma-based and γ-Al 2 O 3 -catalyzed NH 3 synthesis from H 2 O (a hydrogen source) and air/ N 2 (a nitrogen source) was studied under low temperature and low pressure conditions. The experimental results show that NH 3 can be synthesized with air/N 2 and H 2 O, although byproducts such as NO and N 2 O are also formed. The NH 3 formation rate resulting from the use of N 2 and H 2 O is higher than that of air and H 2 O. Increasing specific energy input (SEI) can increase the NH 3 formation rate. Nevertheless, the energy efficiency of NH 3 synthesis technology first increases and then decreases with SEI. An NH 3 formation rate of 2.92 μmol h −1 g −1 was achieved with an SEI of 11.68 J mL −1 and energy efficiency of 5.10 mg kW −1 h −1 (1.28 mg kWh −1 g −1 ), when wet air at a flow rate of 200 mL min −1 was introduced into the dielectric barrier discharge (DBD) reactor, which was lower than that (4.30 μmol h −1 g −1 ) attained with N 2 + H 2 O under an SEI of 11.50 J mL −1 and energy efficiency of 7.63 mg kW −1 h −1 (1.91 mg kWh −1 g −1 ). Additionally, the γ-Al 2 O 3 catalyst exhibited good stability. Different results show that plasma-based and γ-Al 2 O 3 catalyzed NH 3 synthesis technology is promising. KEYWORDS: NH 3 synthesis, plasma, H 2 O and N 2 , Al 2 O 3 catalyst, dielectric barrier discharge

Plasma‐Assisted Sustainable Nitrogen‐to‐Ammonia Fixation: Mixed‐phase, Synergistic Processes and Mechanisms

“…Catalysts characterized by well-developed pore structures and high surface areas are favored, as they enhance the adsorption and capture of excited state particles within the plasma phase. [91] Research conducted by Zhang et al [33] and Nguyen et al [90] collectively underscores that, within the framework of plasma collectively revealed that in plasma catalysis, byproducts generated from the reaction between N 2 and water vapor predominantly manifest as N 2 O, while other forms of NOx remain below detectable thresholds. Notably, N 2 O production primarily occurs in the gas phase.…”

“…Additionally, Feng and his team‘s research suggests that the water vapor content significantly impacts energy efficiency and yield. When the water bath temperature increased from 30 °C to 90 °C, energy efficiency increased from approximately 4.4 mg ⋅ kWh −1 to about 7.5 mg ⋅ kWh −1 , and NH 3 production rate rose from around 2.6 μmol ⋅ g cat −1 ⋅ h −1 to approximately 4.3 μmol ⋅ g cat −1 ⋅ h −1 [91] …”

“…A thoughtful catalyst design can partially mitigate these challenges. Catalysts characterized by well‐developed pore structures and high surface areas are favored, as they enhance the adsorption and capture of excited state particles within the plasma phase [91] …”

Wet Catalytic Oxidation of a FeMnCe-Activated Semi-Coke Catalyst for Treating Piperazine Wastewater

“…Furthermore, in the presence of • OH, 2hydroxy-piperazine (1) was subsequently formed, which underwent ring-opening oxidation to form [(2-aminoethyl)amino]acetaldehyde (2). However, [(2-aminoethyl)amino]acetaldehyde (2) was found to be unstable 29 and formed formaldehyde (8), oxalic acid (3), and ethylenediamine (4) by N−C bond breaking. The ethylenediamine continued to degrade to produce glycine (5) and ethanoic acid (6), which further produced oxalic acid (3) and formaldehyde, further forming formic acid (9).…”

“…The main treatment methods for piperazine wastewater include physical, chemical, and biological methods. , Physical methods such as adsorption and precipitation can only separate piperazine from water and are prone to secondary contamination; in contrast, biological methods are prone to inactivation by poisoning, leading to their limited application . In recent years, advanced oxidation processes (AOPs) have been favored by many researchers due to their advantages including a fast reaction rate and final degradation products such as N 2 , CO 2 , and H 2 O. − …”