Effects of regeneration cycles on heptane–H2 reactions over Pt–Re/Al2O3 catalysts

Abstract

Alumina-supported Re, Pt and Pt–Re catalysts have been used to catalyse reactions of heptane–H₂ mixtures as a probe of sulfur-free Pt–Re/Al₂O₃ catalyst structure after a series of pretreatments involving oxidation–reduction and oxychlorination–reduction 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 oxidation–reduction and oxychlorination–reduction completely removed deposited coke from used catalysts but the addition of Cl maintained higher metal surface area and catalytic activity.