The operating conditions of the plasma reactor have been studied in relation to energy efficiency and product distribution. This involved testing different energy delivery schemes and inlet gas flow rates. The results indicate that the total energy dissipated in the plasma discharge is the main driver of reactant conversion and in turn of process throughput. Therefore, the different pulse repetition patterns have marginal effect on the production of the different olefins. Whilst the tests involved a substantial amount of investigated variables, including Optical Emission Spectroscopy analysis, the Artificial Neural Network built on these input values requires more datapoints for robust training and prediction. Hence, the objective of Work Package 1 'Optimization of reactor configuration and operating conditions' (M2.1) has been partially achieved as it does not involve the full utilization of the ANN, as also mentioned in the Objective 1) of Section 1.1. Nonetheless, the most performing operating conditions in terms of energy efficiency are reported in our scientific publication as a standard for operating post-plasma catalytic processes (
https://doi.org/10.1016/j.cep.2024.109946(se abrirá en una nueva ventana)).
New structured catalysts have been designed and tested for the once-through conversion of methane (CH4) into ethylene (C2H4). The metal structure that serves as catalyst support enables high thermal conductivity, hence the process can be run exclusively with electrical power. Different metal catalyst loadings have been tested for the hydrogenation reaction of acetylene (C2H2), which is the main product of CH4 coupling in the plasma discharge, into C2H4. Therefore, M3.1 M3.2. and M3.3 about catalysts synthesis, 3D printing of the metal electrode, and catalysts deposition have been fully achieved. Both experimental and modeling validation have been conducted to identify the optimal catalyst formulation, hence intensifying the C2H4 productivity. (DOI: 10.1039/D4EY00203B DOI: 10.1039/D5CY00529A
https://doi.org/10.1016/j.cep.2024.109946(se abrirá en una nueva ventana)). Therefore, objective 2) 'Intensify C2H$ production' has been fully achieved.
The plasma operating variables in the nanosecond-pulsed discharge operation have been optimized in the reforming of biogas surrogates (i.e. mixture of CH4 and CO2) into platform chemicals such as CO and H2. The energy efficiency of the process is controlled via tuning the energy dissipated in each discharge and the discharge frequency. Moreover, the plasma-driven CH4 coupling and CO2 dissociation can be tuned to attain a product composition that is suitable for downstream processes. (
https://doi.org/10.1016/j.ijhydene.2025.150293(se abrirá en una nueva ventana)) Different catalysts have been tested in the post-plasma zone, as per WP3 of the proposal; however, no significant effect was observed on the product distribution, owing to the gas temperature being to low for coupled reactions. Nonetheless, M4.1 of WP3 'NPD reactor for DRM operational with consistent product quality and performance' has been fully achieved. This relates to objective 3) 'Develop a blueprint for customized catalytic plasma processes' which is partially achieved due to the limited application of the DRM process to non-catalytic conditions.
Furthermore, plasma-assisted CH4 pyrolysis has been investigated in the framework of low-carbon H2 production. The nanosecond-pulsed discharge can activate pure CH4 streams with high selectivity to H2 and C2H2. The energy delivered to the plasma can be regulated to maximize H2 energy efficiency and throughput. While this application was not originally included in the proposal, it expands the range of processes suitable for the NPD plasma reactor. The work has been presented in a scientific publication (
https://doi.org/10.1016/j.cep.2025.110483(se abrirá en una nueva ventana)).
Owing to the earlier termination of the fellowship, WP4 has been only partially undertaken. Techno-Economic Analysis (TEA) of the plasma process has not been performed as planned for M5.1 while a simplified estimation of the process carbon footprint of H2 production from biogas has been realized and presented in a journal article (
https://doi.org/10.1016/j.ijhydene.2025.150293(se abrirá en una nueva ventana)). Thereby, M5.2 has been partially achieved. Therefore, Objective 5) on feasibility assessment is also partially achieved.
