Isomerization and hydrocracking of heptane over bimetallic bifunctional PtPd/H-beta and PtPd/USY zeolite catalysts

Bifunctional catalysts are prepared by loading NH4-Beta zeolites with platinum, palladium, and platinum-palladium metal combinations via cation exchange and incipient wetness impregnation with Pt(NH3)(4)Cl-2 and Pd(NH3)(4)Cl-2 complexes, followed by calcination and reduction. In comparison to the Pt and Pd loaded acid zeolites, the bimetallic Pd-Pt zeolites are found to be more active and selective in the isomerization of heptane. The noble metal phases are characterized with temperature programmed reduction and hydrogen chemisorption. The dispersion of platinum is significantly improved in presence of as little as 20 mole% of palladium. The improved Pt dispersion leads to a better intimacy and balance of the acid and hydrogenation-dehydrogenation functions in these bifunctional catalysts and suppression of undesirable hydrogenolysis and dimerization-cracking activity. On Pt/USY zeolite, the addition of palladium has similar beneficial effects on the catalytic performances. (C) 1997 Academic Press