INFLUENCE OF O-2 AND O-3 REGENERATION ON THE METALLIC PHASE OF THE PT-RE AL2O3 CATALYST/

The influence of the regeneration with oxygen or ozone on the metallic function activity of the Pt-Re/Al2O3 catalyst prepared by catalytic r eduction is studied. The interaction between Pt and Re is higher when activation is carried out by direct reduction. However, calcination at 450 degrees C leads to a segregation of metals. The regeneration carr ied out with diluted O-2 destroys the metallic interaction producing s egregation of Pt and Re, while the regeneration with O-3 at low temper ature avoids such segregation to a large extent. Ozone not only burns coke off, but also modifies its burning characteristics as measured by temperature programmed oxidation technique (TPO) with 6% O-2/N-2. It was found that after the O-3 treatment, the coke left on the catalyst burns at lower temperatures if compared to the coke without O-3 treatm ent. Therefore, a regeneration treatment can be carried out at low tem peratures by combining a first step with O-3 followed by a second one with O-2 at lower temperatures than those needed in conventional regen eration procedures. (C) 1997 Elsevier Science B.V.