A study published in Chem on July 10 has developed a plasma-catalysis synergistic process, which employs SiO₂-Al₂O₃ aerogel-supported Ni nanoparticles (Ni/SiAlO) in a dielectric barrier discharge (DBD) reactor to enable the co-conversion of nitrogen (N₂) and methane (CH₄) into valuable N-containing compounds under mild conditions.

The study was led by Profs. DENG Dehui and YU Liang from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS).

"Our study provides a promising pathway for the direct co-conversion of N₂ and CH₄ into valuable N-containing chemicals under mild conditions and offers new opportunities for efficient and environmentally friendly chemical synthesis," said Prof. DENG.

Schematic illustration and the performance for plasma-catalytic conversion of nitrogen and methane to valuable N-containing compounds (Image by LI Di and LIU Ziming)

N₂ and CH₄ are naturally abundant but extremely inert molecules, making their conversion and utilization highly challenging. Currently, the separate conversion of N₂ and CH₄ relies on energy-intensive processes.

Direct co-conversion of N₂ and CH₄ offers an atom-economical pathway, where CH₄ dehydrogenation can directly supply hydrogen for N₂ hydrogenation, thereby bypassing the complex steps. However, simultaneous activation of both molecules and selective construction of N-C and N-H bonds under mild conditions remains a formidable challenge.

This study found that, under mild conditions of approximately 80 °C and atmospheric pressure, the plasma-catalysis process achieved N₂ and CH₄ conversions of 3.3% and 49.3%, respectively, while co-producing H₂ and C₂-C₅ hydrocarbons. The yields of alkylamines, including methylamine and ethylamine, and ammonia reached 0.88 and 6.43 mmol g_Ni^-1 h^-1, respectively.

Through a series of custom-built in-situ characterization techniques and computational studies, the researchers elucidated a significant plasma-catalysis synergy in boosting the co-conversion efficiency.

According to the researchers, on the one hand, packing the catalyst increases the mean electron energy of the plasma, thereby facilitating the activation of reactants. On the other hand, the adsorption of plasma-derived reactive species on the Ni catalyst promotes the N-C and N-H coupling, enabling the efficient synthesis of alkylamine and ammonia.