Studies of hydrogen spillover. Part 2.—Titration of hydrogen adsorbed upon silica supported platinum by pent-1-ene

Abstract

The initial product obtained on treating hydrogen-reduced Pt/SiO₂ with pent-1-ene (161 N m^–2) in flowing nitrogen (101 kN m^–2) is n-pentane alone. As the reaction proceeds its yields falls and the isomers of pent-1-ene also appear. By assuming that it is hydrogen directly held to platinum which reacts to give n-pentane alone, the surface area and crystallite size of the platinum can be estimated. For Pt/SiO₂ the results are in good agreement with those determined by transmission electron microscopy and by X-ray line broadening. Caution is required in applying the technique to Pt/γ-Al₂O₃ and Pd/SiO₂. The results also reveal the effect of hydrogen coverage upon the isomerisation activity of supported platinum and the migration of spilled over hydrogen; n-pentane appearing in low yield is believed to result from spilled over hydrogen migrating back from the support to the metal to react with pent-1-ene.