EFFECT OF FLUORINE ON HYDRODENITROGENATION ACTIVITY OF DOUBLY PROMOTED (ZN+CO) MOLYBDENA ALUMINA CATALYSTS

Activity for the hydrodenitrogenation (HDN) of quinoline has been stud ied at an overall pressure of 7 MPa in the temperature range 623-698 K , on a series of doubly promoted ZnCo-Mo catalysts supported on fluori nated alumina (0.0-2.0 wt% F). For the F free catalysts the partial su bstitution of Co by Zn does not affect HDN activity. However, for the fluorinated catalyst series, the HDN activity was found to increase sl ightly for fluorine contents around 1.0-1.3 wt% F. Simultaneously, a m inimum in hydrogenation activity to N free products was observed. Thes e results have been explained in terms of two antagonistic effects. Wh ile fluorine favours multilayered MoO3 crystallites, with shorter dime nsions in the lateral direction caused by disruption in the geometry, cobalt has a propensity to intercalate at the edges of the crystals, t hus inhibiting the formation of stacks in which the reduced sites, bel ieved to be needed for HDN and hydrogenation, are located.