Determination of Number of Activated Sites Present during Olefin Metathesis by Supported ReO_<i>x</i>/Al₂O₃ Catalysts

Abstract

The number of surface rhenia sites on alumina participating in olefin metathesis, usually counted by chemical titration of surface reaction intermediates with olefins, has been debated for several decades. The current olefin titration measurements, however, demonstrate that the number of reactive surface intermediates on supported rhenia/alumina catalysts is strongly dependent on the experimental variables. The new findings reveal that the accepted titration procedures significantly undercount the number of activated surface rhenia sites upon exposure to olefins by ∼10¹–10² because of invalid assumptions