Hydrogen spillover on silica II. Kinetics and mechanism of the induction of catalytic activity

摘要: To understand the potential significance of phenomena associated with hydrogen spillover it is necessary to mechanism by which catalytic activity induced onto oxides and relative these sites. quantify activity, estimate number active sites that are created so a “proper” turnover frequency can be calculated. We have studied hydrogenation on silica spilled over from platinum as function pretreatment time temperature exposure hydrogen. The induction requires long periods (>6 h, increasing 12 h) at high temperatures (400–460 °C). With optimum conditions concentration approaches 1013/cm2 surface maximum estimated 10−1 s−1 for ethylene 200 °C. seem reaction specific “associated” (vicinal or geminal) hydroxyls