Plasma-Catalytic Hydrolysis of Urea for Ammonia Production: Optimization and Kinetic Study

ZrO2 was combined with dielectric barrier discharge plasma for hydrolysis of urea under ambient conditions. Effects of discharge power, O2 presence in carrier gas, repeated use of ZrO2 on hydrolysis of urea, and formation of byproducts were investigated. Urea could be completely hydrolyzed to NH3 and CO2 at 87–239 °C during the temperature-programmed catalytic process regardless of the presence of O2 in the carrier gas. By introducing plasma into the catalyst bed, urea could be hydrolyzed under ambient conditions, and increasing discharge power accelerates the hydrolysis of urea. Higher discharge power and O2 absence in the carrier gas are favorable for increasing NH3 yield, suppressing byproduct formation and reducing energy consumption of the plasma-catalytic urea hydrolysis process. ZrO2 shows excellent stability in the O2-free plasma-catalytic urea hydrolysis process. Plasma-catalytic hydrolysis of urea follows the pseudo-first-order kinetic model and could be described by the direct hydrolysis reaction.