RHODIUM IN BASIC ZEOLITE-Y - A STABLE, SELECTIVE CATALYST FOR CO HYDROGENATION

Zeolite-entrapped rhodium carbonyl clusters were prepared by reductive carbonylation of [Rh(CO)2(acac)] in the pores of zeolite Y made basic by treatment with NaN3. The samples were characterized as CO hydrogenation catalysts at 1-20 atm, 225-325-degrees-C and H-2/CO feed molar ratios of 0.5-3.0. Rh carbonyl clusters were formed and evidently entrapped in the strongly basic zeolite, and the catalyst was active for CO hydrogenation, at low conversions giving a non-Schulz-Flory distribution of C1-C5 hydrocarbons with high olefin to paraffin ratios. The catalyst was stable, operating at 300-degrees-C and 20 atm with a H-2/CO molar ratio of 1 for more than two weeks with no significant loss in activity and selectivity. High partial pressures of CO (or CO + H-2) stabilize the catalyst. The predominant rhodium species are suggested to be rhodium carbonyl clusters trapped in the zeolite cages. The results suggest opportunities for synthesis of metal clusters in strongly basic zeolites and for application of encaged metal clusters as catalysts for shape-selective conversions of synthesis gas.