Hydrogen effects in hexane reactions over Al2O3 supported Pt, Ir and Pt-Ir catalysts

Hexane was tested under similar conditions on Al2O3 supported Pt, Ir and Pt-Ir catalysts. A conventional impregnation on commercial alumina and a sol-gel procedure involving the introduction of the Pt or Ir components at the commencement of gelification were applied for the preparation of monometallic catalysts. Pt-Ir samples were prepared by co-impregnation or using a bimetallic complex precursor, [Ir(NH3)(5)Cl][PtCl4], produced in the pores of the support. Increasing H-2 pressure at both 603 and 663 K enhanced the overall activity and the very pronounced hydrogenolysis on Ir. Non-degradative products, including isomers, methylcyclopentane, benzene and hexenes, showed, as a rule, maximum rates as a function of p(H-2) on Ir also, in agreement with earlier and present reports concerning Pt. Both Pt and Ir catalysts on a sol-gel alumina were superior in non-degradative reactions to their conventional counterparts. The hydrogenolysis activity of both bimetallic catalysts was below the average for Pt and Ir, indicating Pt-Ir interactions. These were more pronounced with Pt-Ir prepared from a complex precursor, showing a higher activity in non-degradative reactions, more manifest at 663 K.