Kinetic Study of Nonthermal Plasma Activated Catalytic CO2 Hydrogenation over Ni Supported on Silica Catalyst

Nonthermal plasma (NTP) is a promising alternative to conventional thermal activation for promoting efficient heterogeneous catalysis under ambient conditions. However, full understanding of the hybrid NTP catalyst system is challenging due to its complexity. Herein, using the catalytic CO2 hydrogenation over the Ni@SiO2 catalyst as the model system, we carried out comparative kinetic studies of the catalysis under both thermal and NTP conditions to assess the reaction dynamics and kinetics, aimed at understanding the interactions between NTP and catalyst surface. Specifically, the performance of process parameters was evaluated by varying temperature, total flow rate, partial pressure of H-2, and dielectric barrier discharge (DBD) power. Kinetic studies showed that, under the NTP conditions, the catalysis exhibited non-Arrhenius behavior likely due to the complex interactions between NTP and Ni catalyst, showing a linear correlation between the natural logarithmic turnover frequency (TOF) and the reciprocal DBD power (instead of the bulk reactor temperature measured). Additionally, under the conditions used, the activation energy of the catalysis under the NTP conditions was independent of the total feed flow rate (at similar to 29 kJ mol(-1), being significantly lower than that of thermal catalysis (similar to 80 kJ mol(-1)). Kinetic studies suggested that the dissociated H species due to NTP discharge in the gas phase are ready to interact with Ni surfaces, thus reducing the activation barrier required to enable the surface reactions.