Improvement of Activity and Stability of CuGa Promoted Sulfated Zirconia Catalyst for n-Butane Isomerization

The use of CuGa promoted sulfated zirconia (CuGa/SZ) catalyst for the isomerization of n-butane to isobutane has potential value as a replacement for the current catalyst for this important reaction (chlorinated alumina). Ga promoted SZ work well but deactivate rapidly. Several related catalysts (SZ, Ga/SZ, Cu/SZ, and CuGa/SZ) were compared. Only CuGa/SZ shows the most interesting properties: The stable conversion is 55%, and the selectivity to isobutane is 82% for 200 h. This is mainly attributed to Cu promoting a better incorporation of GaOx into the support, higher Bronsted/Lewis ratio, smaller ZrO2 crystallite, retard in the transformation from tetragonal (active for isomerization) to monoclinic (inactive) ZrO2 and higher sulfate stability. This effect is finally compared to the effect of Pd and Pt, demonstrating potential benefits of CuGa/SZ for commercial application due to their similar yields of isobutane (40–45%).