2025 AIChE Annual Meeting

(117d) Plasma-Assisted Oxidative Coupling of Methane over Sodium-Promoted Gold Catalysts

Authors

Yiteng Zheng - Presenter, Stevens Institute of Tech
Hengfei Gu, Princeton University
Bruce E. Koel, Princeton University
Methane is an underutilized resource due to a lack of efficient technologies that enable its conversion into value-added chemical feedstocks. Production of chemical feedstocks from methane is currently dominated by technologies that rely on generation of synthesis gas as the first step. These technologies have an inherent inefficiency since the breaking of C-H bonds in synthesis gas production must be substantially reversed in subsequent steps. Therefore, development of direct methane conversion is highly desired. The oxidative coupling of methane is one of the promising processes that can directly convert methane into C2 hydrocarbons. However, high reaction temperatures (> 1000 K) are required to activate methane, and the selectivity to desired products is poor.

To address this challenge, we coupled non-thermal plasma and heterogenous catalysts to selectively produce C2 products via oxidative coupling of methane at room temperature. A reactor was developed to enable in-situ/operando Raman spectroscopy during plasma-assisted reaction. Catalytic kinetic measurements for sodium-promoted gold catalysts were collected while varying the methane and oxygen partial pressures using the Raman cell. The catalysts were characterized by TEM, N2 physisorption, DR-UV-Vis, and in-situ DRIFTS. In-situ Raman experiments were conducted to further investigate the catalysts. The plasma properties were characterized by OES. Under most of the testing conditions, the sodium-promoted gold catalyst was more active and selective. Sodium was found to increase gold dispersion into smaller particles. Also, Na could favor the formation of atomic O on Au surfaces, which has been proposed in the literature to be the active sites for methane activation. The findings in this study will be useful in the development of improved catalytic processes for oxidative coupling of methane into value-added chemical feedstocks. Beyond methane activation, the design of the in-situ/operando Raman cell will be helpful in improving catalysts for a wide range of plasma-assisted catalytic reactions.