Structural Characterization of Lanthanide Promoted Sulfated Zirconia Catalysts

 Increasing the octane value of light naphtha streams through isomerization is accomplished commercially by using a range of catalysts including chlorided alumina, sulfated zirconia, and zeolites. Sulfated zirconia (SZ) catalysts are stable, can be used at low temperature, and have activities significantly higher than zeolitic catalysts but are less active than chlorided alumina catalysts.   The activity of sulfated zirconia can be enhanced with the addition of first row transition metal cations such Fe and Mn.  It has been shown that these promoters are in part incorporated into the zirconia lattice, leading to stabilization of the tetragonal (or cubic) ZrO₂ structure.

It is well known that the addition of lanthanides into zirconia affects many properties including cation diffusion, defect ordering, and oxygen diffusion.  In this paper the structural characterization of a Tm-promoted SZ catalyst (as representative lanthanide) is presented with the aim of determining if the structural promotion of the lanthanide is similar to that of Mn.   EXAFS data is presented, together with synchrotron XRD, XPS and LEIS data.