ATOMIC-FORCE MICROSCOPY EXAMINATION OF THE TOPOGRAPHY OF A FLUID CRACKING CATALYST SURFACE

Examination of the topography of a fluid cracking catalyst (FCC) using atomic force microscopy (AFM) has revealed the presence of a unique surface architecture characterized by valleys, ridges, crevices, dislodged plates, and narrow slits 6-9 nm wide. Formation of pits and craters with micrometer dimensions are believed to result from incomplete delamination of clay platelets used in catalyst preparation. Atomic scale resolution images were found consistent with the presence of kaolin and faujasite-type crystals. When V was added at the 2-4% level, the catalyst surface roughness decreased. Furthermore, AFM images indicate the formation of vanadia islands and that vanadia coat the surface causing blockage of the narrow slits and cracks responsible for most of the catalyst microporosity. The extent of clay delamination can influence macropores formation on the FCC surface and therefore influence the tendency of the catalyst to occlude hydrocarbons during cracking. Removal of occluded surface vanadia should restore some of the initial activity in spent equilibrium FCC.