mPlasma-assisted ammonia synthesis in a packed-bed DBD reactor over M/BaTiO3 (M = Fe, Co and Ni): Process optimization towards cost-effective ammonia synthesis using RSM

Non-thermal plasma (NTP) assisted ammonia (NH 3 ) synthesis has been performed in a packed-bed dielectric barrier discharge (DBD) reactor. The presence of M/BaTiO 3 (M = Fe, Co and Ni) catalysts in the DBD reactor significantly improved the NH 3 concentration and energy efficiency with a sequence of Ni/BaTiO 3 > Co/BaTiO 3 > Fe/BaTiO 3 > BaTiO 3 . N 2 adsorption-desorption experiment, X-ray diffraction analysis and temperature-programmed desorption of CO 2 were performed to get insight into the relationships between the plasma-assisted NH 3 synthesis process and M/BaTiO 3 catalysts. The improved performance over Ni/BaTiO 3 could be attributed to abundant basic sites and weaker metal-nitrogen (M − N) bindings on catalyst surfaces, which benefits the generation of NH x species and desorption of formed NH 3 . Response surface methodology (RSM) was utilized to assess the contribution of each independent process parameters and explore the mutual effects on NH 3 synthesis process systematically. The results of analysis of variance (AVONA) suggested that plasma discharge power and gas flow rate were the most significant factors in affecting the NH 3 concentration and energy efficiency of plasma-assisted NH 3 synthesis process, respectively. Based on the proposed polynomial regression model, the maximum energy efficiency of 2.37 g kWh −1 was achieved at the predicted optimal working condition over Ni/BaTiO 3 . • BaTiO 3 is used to support transition metal for NH 3 synthesis for the first time. • Ni/BaTiO 3 presents better catalytic activity due to abundant strong basic sites. • CCD-RSM is used to optimize plasma-assisted NH 3 synthesis process systematically. • Mutual effects of independent process parameters are illustrated based on RSM. • The energy efficiency is significantly improved using prediction model.