THE EFFECT OF PHOSPHORUS ON THE HDN REACTION OF PIPERIDINE, DECAHYDROQUINOLINE AND ORTHO-PROPYLANILINE OVER NI-MOS2 AL2O3 CATALYSTS/

The hydrodenitrogenation (HDN) of piperidine, decahydroquinoline (DHQ) and ortho-propylaniline (OPA) has been studied over NiMo(P)/Al2O3 cat alysts at 593 K and 3.0 MPa in order to understand the effect of phosp horus on the elementary HDN reaction steps. Phosphorus exhibited a neg ative effect on the HDN of piperidine and DHQ, both on the C-N bond cl eavage reaction and on the subsequent hydrogenation reaction of alkene to alkane. A P/Al2O3 catalyst showed no HDN activity at all, neither with piperidine, nor with DHQ. A positive effect of phosphorus was obs erved in the HDN of OPA, where hydrogenation of the aromatic ring is n eeded and is rate limiting. It is suggested that introduction of phosp horus to NiMo/Al2O3 catalysts on the one hand decreases the available support surface area, and as a consequence the dispersion of the Ni-Mo -S phase and thus the capacity for C-N bond breaking and olefin hydrog enation. On the other hand, phosphorus induces either new or more acti ve sites for the hydrogenation of aromatics.