Mathematical modelling and simulation of nitrite hydrogenation in a membrane microreactor

Nitrite hydrogenation using heterogeneous catalysis is an important process for purification of wastewater or potable water. The main aim of this study is to explore a new mechanistic model and simulation for a heterogeneously catalysed reaction in a microporous catalytic layer. The system studied involves a liquid solution containing certain amount of nitrite, and a membrane reactor in which the nitrite penetrates into the catalytic layer to react with hydrogen. The developed model considers coupling between equations of momentum transfer in free and porous media and convection-diffusion of nitrite. It was found that there is great agreement between measured data and modelling values. Increasing velocity was the main reason for reduction of nitrite conversion and also there was a slight increase in nitrite conversion with increasing the thickness and porosity of catalytic layer. Furthermore, it was found that the diffusion mass transfer mechanism is favourable for nitrite hydrogenation while convective mass transfer of fluid flow has negative impact on nitrite hydrogenation.