A series of bimetallic catalysts RhSnx SiO2 (x = 0.4, 0.7, 0.9, and 1.4) were synthesized by the reaction of the monometallic catalyst Rh SiO2 with Sn(n-butyl)4 under hydrogen. Various chemical and spectroscopic methods indicated that the metals present were fully reduced, and that tin atoms rest on the surface, very slightly increasing particle size and producing isolated rhodium sites. The catalytic reactions of propylene/hydrogen mixtures in the presence of these bimetallic catalysts are compared with those of the monometallic Rh SiO2 catalysts. The mechanistically interesting reactions observed are those of carbon-carbon bond formation and cleavage. For the monometallic catalyst, olefin homologation and hydrogenolysis were observed, reactions which invoked the transfer of C1 fragments from one olefin to another. For the bimetallic catalysts, a marked increase in the selectivity for C6 products was observed. The presence of hydrogen is necessary to this reaction but selectivity for C6 is enhanced when hydrogen is in deficit with respect to propylene. Selectivity for C6 increases with the surface rhodium to tin, Rhs Sn, ratio to a maximum at 0.9. Low temperature favors the formation of C6 and C2 products.
- Bimetallic catalysts
- Supported catalysts
ASJC Scopus subject areas
- Process Chemistry and Technology
- Physical and Theoretical Chemistry