Hydrogen production via two-stage plasma catalytic decomposition of ammonia over Fe/ZSM-5 catalyst

초록

This study investigates a 2-stage ammonia (NH3) decomposition process using nonthermal gliding arc plasma followed by thermal catalytic cracking. A 2-step catalyst preparation method was implemented, which included the ion-exchange and impregnation methods to achieve more homogeneous deposition of metal species on the zeolite support relative to the single-step impregnation method. The gliding arc discharge was sustained by an alternating current power source at 400 Hz. Plasma process parameters such as flow rate and NH3 concentration were systematically varied to evaluate their impact on NH3 conversion and hydrogen (H2) production. Results indicated that the optimal conditions for plasma-based H2 production were achieved at a flow rate of 4.5 L/min and an NH3 concentration of 11% in nitrogen (N2), yielding an H2 production of 14.5 g/kWh. Further, the thermal catalytic NH3 decomposition revealed that the catalyst prepared using the combined ion-exchange and impregnation method was superior to those prepared via individual methods. It was observed that although a higher conversion was achieved with the combination of plasma, the energy required was high. Also, the catalyst itself was capable enough at higher temperatures, achieving around 92% conversion at 700 degrees C. Thus, additional energy used for plasma is not essential at high temperatures, suggesting that the plasma stage can be beneficial at low temperatures or as a preheating stage of the catalyst.

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