Kinetics of nitrate reduction in monolith reactor

The kinetics of nitrate reduction with hydrogen was studied in a metallic monolith reactor, where the catalytically active material was Cu-doped Pd supported on Al2O3. The experiments were carried out at 60°C and at hydrogen pressures of 2 atm and 4 atm. The reactor was operated in semibatch with respect to hydrogen, whereas the liquid phase was in batch recirculating through a storage tank. The main reaction products were nitrogen and ammonia; nitrite was formed as an intermediate product. The reduction kinetics was described with a rate model based on a mechanism where absorbed NO is the key intermediate on the catalyst surface. The mass transfer parameters were estimated from correlations and the mass transfer model was combined to the kinetic model. The reaction kinetics and the mass transfer were included in a plug-flow type of model for the monolith and the kinetic parameters were estimated with non-linear regression analysis. Simulation of the experimental conditions showed that the rate model can be used in nitrate hydrogenation.