E�ects of regeneration cycles on heptane�H2 reactions over Pt�Re/Al2O3 catalysts

Alumina-supported Re, Pt and PtÈRe catalysts have been used to catalyse reactions of heptaneÈH mixtures as 2 a probe of sulfur-free PtÈRe/Al catalyst structure after a series of pretreatments involving 2O3 oxidationÈreduction and oxychlorinationÈreduction regeneration cycles. Catalyst activities and selectivities for
aromatization, cyclization, hydrogenolysis and isomerization reactions are discussed in relation to CO and H2 chemisorption, IR and X-ray absorption near-edge spectroscopy (XANES) data and were consistent with
alloying of Pt and Re with Re surface enrichment on the alloy particles. Surface enrichment of Re was greater
in the absence rather than the presence of Cl in the catalyst pretreatment. Both oxidationÈreduction and
oxychlorinationÈreduction completely removed deposited coke from used catalysts but the addition of Cl
maintained higher metal surface area and catalytic activity.