Liquid-Phase Hydrogenation of Nitrobenzene in a Tubular Reactor: Parametric Study of the Operating Conditions Influence

Fixed-bed reactors for nitrobenzene (NB) hydrogenation into aniline (ANL) in the liquid phase have not experienced extensive industrial-scale development, mostly due to difficulties in removing the reaction heat generated. In this work, NB hydrogenation was performed in a tubular fixed-bed reactor using a Pd/Al2O3 commercial catalyst. The influence of some operating conditions was analyzed by assessing catalyst performance in NB conversion and selectivity toward ANL and secondary products. It was found that catalyst time of usage is extremely important while NB conversion remains stable, selectivity toward the products formed changes (ANL selectivity increases with the catalyst use but the formation of secondary products decreases until almost disappearing). It was also found that temperature and pressure are the most important parameters in the ranges studied and that NH3, which is a reaction product with potential influence in gas compositioin, does not affect NB conversion but helps decreasing secondary products formation.