Structure sensitivity of cyclopropane hydrogenolysis on carbon-supported platinum

There has been debate in the past as to whether or not cyclopropane hydrogenolysis is a structure sensitive reaction. This paper addresses the structure sensitivity of cyclopropane hydrogenolysis on Pt using K+ addition to Pt/C and compares the results to those for CO hydrogenation, a classic structure insensitive reaction. Kinetic parameters determined for both reactions show the effect of K+ on Pt to be limited to simple site blockage at the reaction conditions used. Determination of the site ensemble size (number of contiguous surface metal atoms) required for reaction using Martin’s model suggests that cyclopropane hydrogenolysis requires a site ensemble size of ca. 7, whereas the structure insensitive CO hydrogenation reaction requires only an ensemble size of ca. 1. In addition, evidence suggests that K+ decorates Pt non-uniformly.

Although poisoning/blocking of Pt by K+ appears to be non-uniform, reaction analysis strongly indicates the structure sensitivity of cyclopropane hydrogenolysis on Pt. Based on Martin’s model, the ensemble size required for this hydrogenolysis reaction appears to be ca. 7, whereas the structure insensitive CO hydrogenation reaction requires an ensemble size of ca. 1.Figure optionsDownload high-quality image (55 K)Download as PowerPoint slideHighlights
► Structure sensitivity of cyclopropane hydrogenolysis on Pt has been shown for Pt/C.
► Site ensemble size for cyclopropane hydrogenolysis on Pt appears to be ca. 7.
► Evidence suggests that K+ decorates Pt crystallites non-uniformly.