Coke and Product Profiles Formed Along the Catalyst Bed during n-Heptane Reforming. II. Influence of S on Pt/Al2O3 and Pt?Re/Al2O3

QUERINI, C.A.; FUNG, S.C.

JOURNAL OF CATALYSIS

Año: 1996 vol. 161 p. 263 - 273

0021-9517

Studies of coke and product profiles along catalyst beds of Pt/Al2O3 and Pt?Re/Al2O3 during n-heptane reforming have provided insight into catalyst deactivation and reaction mechanisms. The addition of rhenium to a Pt catalyst changes coke and product profiles similar to those observed with an increase in pressure. Sulfur modifies these profiles in the opposite direction of rhenium. It affects the catalyst in a similar manner to a decrease in reactor pressure: a reduction in hydrogenolysis activity, an increase in dehydrogenation and coke-make, and a shift of the maximum in the coke profile toward the bottom of the reactor. Due to a slow stripping of sulfur during reforming reactions, an increasing sulfur concentration along the bed is observed at the end of several-days run. As a consequence, the coke profile does not match exactly with the C5-ring naphthene concentration profile, as was previously found on both unsulfided Pt and Pt?Re catalysts. The observed increase in coke-make and dehydrogenation activity, when sulfur is added to the Pt?Re catalyst, is probably due to a decrease in the hydrogen surface fugacity produced through electronic modifications of Pt by adsorbed sulfur atoms. insight into catalyst deactivation and reaction mechanisms. The addition of rhenium to a Pt catalyst changes coke and product profiles similar to those observed with an increase in pressure. Sulfur modifies these profiles in the opposite direction of rhenium. It affects the catalyst in a similar manner to a decrease in reactor pressure: a reduction in hydrogenolysis activity, an increase in dehydrogenation and coke-make, and a shift of the maximum in the coke profile toward the bottom of the reactor. Due to a slow stripping of sulfur during reforming reactions, an increasing sulfur concentration along the bed is observed at the end of several-days run. As a consequence, the coke profile does not match exactly with the C5-ring naphthene concentration profile, as was previously found on both unsulfided Pt and Pt?Re catalysts. The observed increase in coke-make and dehydrogenation activity, when sulfur is added to the Pt?Re catalyst, is probably due to a decrease in the hydrogen surface fugacity produced through electronic modifications of Pt by adsorbed sulfur atoms. 2O3 and Pt?Re/Al2O3 during n-heptane reforming have provided insight into catalyst deactivation and reaction mechanisms. The addition of rhenium to a Pt catalyst changes coke and product profiles similar to those observed with an increase in pressure. Sulfur modifies these profiles in the opposite direction of rhenium. It affects the catalyst in a similar manner to a decrease in reactor pressure: a reduction in hydrogenolysis activity, an increase in dehydrogenation and coke-make, and a shift of the maximum in the coke profile toward the bottom of the reactor. Due to a slow stripping of sulfur during reforming reactions, an increasing sulfur concentration along the bed is observed at the end of several-days run. As a consequence, the coke profile does not match exactly with the C5-ring naphthene concentration profile, as was previously found on both unsulfided Pt and Pt?Re catalysts. The observed increase in coke-make and dehydrogenation activity, when sulfur is added to the Pt?Re catalyst, is probably due to a decrease in the hydrogen surface fugacity produced through electronic modifications of Pt by adsorbed sulfur atoms.