Commercial catalysts screening for liquid phase nitrobenzene hydrogenation

In this work, a series of commercially available materials was screened for the catalytic hydrogenationof nitrobenzene (NB). The materials revealed different performances, particularly different activities inwhat concerns the NB conversion, and notably diverse selectivities towards the industrially desired reaction product, aniline (ANL). The catalysts' active phases are based on Pd and Ni (respectively groups Iand II), namely 1 wt.% Pd/Al2O3 (catalyst I.1), 0.3 wt.% Pd/Al2O3 (catalyst I.2), 0.3 wt.% Pd/Al2O3 (catalystI.3), and 50 wt.% NiO/(Al2O3 + SiO2) (catalyst II.1). The fresh and used materials were characterized byseveral physical-chemical techniques, specifically scanning electron microscopy (SEM), high resolutiontransmission electron microscopy (HRTEM), nitrogen adsorption (with BET surface area determination),X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), inductively coupled plasma massspectrometry (ICP-MS) and elemental (CHNS) analysis. It was shown that the catalysts are stable in theconditions studied and no deactivation was found. The characterization results allowed explaining thecatalytic behavior of the tested materials. In particular, catalyst I.1 was found to be the less active, probably due to its much lower BET surface area (and larger Pd particle size). On the other hand, catalyst I.2was the more active, which was well correlated to the smaller average particle size (along with narrowerPd particle size distribution) and smaller pellet size, although the active metal content is low. Finally, itwas observed that catalyst II.1 is the most selective towards light by-products (benzene (Bz), cyclohexylamine (CHA), cyclohexanol (CHOL) and cyclohexanone (CHONA)), probably due to its lower pore sizedimensions