Stability studies of PtSn structured catalysts supported on thin layers of MAl2O4 (M: Mg, or Zn) for paraffins dehydrogenation reactions

In order to determine the catalytic stability, PtSn structured catalysts supported on thin films of MgAl2O4 or ZnAl2O4 deposited on alpha-Al2O3 spheres were studied through five reaction-regeneration cycles in the n-butane dehydrogenation. Bimetallic catalysts show good catalytic stability along the five reaction-regeneration cycles. Among the different synthesized catalysts, the PtSn/Sp-Zn-CN catalyst showed the best catalytic behaviour, showing very good values of yields to butenes and excellent catalytic stability along the cycles, even better than the one of a structured commercial catalyst used industrially for the dehydrogenation of paraffins. The characterization results by temperature-programmed reduction and X-ray photoelectron spectroscopy showed some modifications in the metallic phase of the catalysts after the cycles, mainly in the Sn/Pt surface ratios and in segregation effects in some catalysts. However, the transmission electron microscopy (TEM) results are conclusive in the sense that, after the cycles, the bimetallic catalysts maintained a very high proportion of particles with sizes between 1-2 nm, and therefore, preserved a high metallic dispersion.