THE ROLE OF METAL-SUPPORT INTERACTIONS IN SINTERING AND THERMAL DEACTIVATION OF HDS HDN CATALYSTS/

The sintering process in CoO-MoO3/Al2O3 and NiO-MoO3/Al2O3 catalysts f or HDS/HDN has been studied using two industrial catalysts and their m odel systems, subjected to thermal treatment in oxidizing and reducing atmospheres. The critical role of oxidizing atmosphere for rapid sint ering has been found to be connected with the formation of free MoO3 p hase, distinguished by high mobility in lower temperature regime and i ntermediary presence of liquid phase at higher temperatures. A prerequ isite for HDS/HDN catalyst sintering during regeneration is the destru ction of active monolayer structure that results in formation of the p recursor of MoO3 phase. Specific role of metal-support interactions in this deactivation mechanism has been shown by comparative investigati on on model systems prepared on more inert supports (alpha-Al2O3 and S iO2).