Explorative Study of a Ru/CeO<sub>2</sub> Catalyst for NH<sub>3</sub> Synthesis from Renewable Hydrogen and Demonstration of NH<sub>3</sub> Synthesis under a Range of Reaction Conditions
Tetsuya Nanba, Yuki Nagata, Keisuke Kobayashi, Rahat Javaid, Ryosuke Atsumi, Masayasu Nishi, Takehisa Mochizuki, Yuichi Manaka, Hirokazu Kojima, Taku Tsujimura, Hideyuki Matsumoto, Takayoshi Fujimoto, Koichi Suzuki, Takahiro Oouchi, Sho KAMEDA, Yuki Hoshino, Sho FUJIMOTO, Mototaka KAI, Yasushi Fujimura
Abstract
The potential of Ru/CeO2 catalysts to catalyze the synthesis of ammonia from renewable hydrogen was explored under ambient and high-pressure conditions. Different types of Ru precursors, CeO2, and their combinations strongly influenced NH3 synthesis activity. The catalytic activities of Ru(acac)3 and Ru(NO)(NO3)3 were relatively high at ambient pressure. The activity of 1 wt% Ru/CeO2 with Ru(NO)(NO3)3 as a Ru precursor was studied at high pressure. The dependence of NH3 synthesis activities on temperature, pressure, space velocity, and H2/N2 ratio were investigated. The parameter dependences differed somewhat between different types of CeO2. Use of CeO2 with high surface area resulted in relatively high NH3 synthesis rates and good low-pressure activity. Demonstration of NH3 synthesis using the optimized Ru/CeO2 catalyst was performed with a bench-scale plant with the recirculation of unreacted gases. NH3 synthesis activity was measured using more than 130 combinations of temperature, pressure, space velocity, and H2/N2 ratio. NH3 concentrations in the product gases were close to equilibrium value for the reaction conditions around 400 °C. The effects of operation load on the response of NH3 production was acceptable. Ru/CeO2 catalysts are good candidates for industrial NH3 synthesis from renewable hydrogen.