The role of Re and S in the PtRe S Al2O3 catalyst

PARERA, J.M.; BELTRAMINI,J.N:; QUERINI,C.A.; MARTINELLI, E.E.; CHURIN, E.J.; ALOE, P.E.; FIGOLI, N.S.

JOURNAL OF CATALYSIS

Año: 1986 vol. 99 p. 39 - 52

0021-9517

The modifications in catalytic activity, selectivity and stability when a Pt Al2O3 catalyst is promoted by Re and/or S is studied following several C6 hydrocarbons reforming. A bifunctional reaction scheme, showing modifications from those previously proposed, is introduced in order to interpret the results. Even the catalyst properties of PtRe are not the sum of the ones of Pt and Re, PtRe has properties brought by Pt and by Re. The addition of Re and S modifies the hydrogenolysis-dehydrogenation capacity of Pt. Re decreases the dehydrogenating capacity of Pt, reducing coke formation (desired effect) and increasing the formation of lower molecular weight paraffins by hydrogenolysis (undesired effect). The undesired contribution of Re is partially suppressed by the addition of S, that decreases the hydrogenolytic capacity of PtRe and increases the production of benzene and coke. This opposite action of Re and S on Pt can be related to the opposite electronic transfers, from Re to Pt and from Pt to S. Both geometrical and electronic effects influence the changes in selectivity