US EPA

8562425 

Journal Article 

PtIr Al2O3 catalysts-The effect of PtIr interaction on Ir agglomeration and catalytic performance 

Huang, YJ; Fung, SC; Gates, WE; Mcvicker, GB 

1989 

Yes 

Journal of Catalysis
ISSN: 0021-9517
EISSN: 1090-2694 

118 

1 

192-202 

English 

10.1016/0021-9517(89)90310-2 

Interaction between Pt and Ir has been found to occur on freshly impregnated PtIr Al2O3 subjected only to drying at 393 K. Iridium in the freshly prepared bimetallic precursor material retains the same reduction behavior as monometallic Ir. Iridium promotes the reduction of Pt in the bimetallic precursor material. This promotion results in a 20 K lower temperature-programmed reduction peak temperature than that observed for monometallic Pt. The incorporation of Pt into Ir clusters retards the oxidative agglomeration of Ir. Reduction followed by calcination causes a higher degree of Ir oxidative agglomeration than direct calcination at the same temperature. The incorporation of Pt into Ir clusters decreases the cracking activity of the Ir component as well as the coking tendency of the Pt component, and therefore enhances benzene selectivity. The catalytic performance of a PtIr catalyst approaches that of a Pt-only catalyst as the degree of Ir agglomeration increases. The cracking of n-hexane molecules takes place more frequently at the terminal carbon atom position as the degree of Ir agglomeration increases. © 1989.