Adsorption of surfactant-stabilized colloidal noble metals by ion-exchange resins and their catalytic activity for hydrogenation

Abstract

Hydrosols of ruthenium, rhodium, palladium, platinum, silver, and gold were prepared in the presence of stearyltrimethylammonium chloride (SC), sodium dodecylbenzenesulfonate (SD), or polyethylene glycol mono- p-nonylphenyl ether (PN). Adsorption of colloidal particles in the sols by ion-exchange resins was examined. Positive colloids prepared with SC and negative colloids with Sd or PN were adsorbed by cation-exchange resins (CER) and anion-exchange resins (AER), respectively. Negative colloids of ruthenium and rhodium were exceptionally adsorbed by an H-form CER. Many more aggregations were observed with the noble metal particles adsorbed by CER than with those by AER. The particles of ruthenium, rhodium, palladium, and platinum adsorbed by the resins exhibited a catalytic activity for hydrogenation of cyclohexene at 30°C under atmospheric hydrogen pressure. Those adsorbed by AER were more active than the others despite their considerably aggregated states. Different mechanisms for each colloid adsorption were proposed.