Study of Pt/alumina catalysts preparation

Abstract Platinum-alumina catalysts were prepared at 20°C by using a method in which hexachloroplatinic anions from solution were adsorbed on θ-alumina in the pH range 1–10 and with contact times between 1 and 24 h. An adsorption maximum was observed at pH around 3–4. From measurements of electrophoretic mobility, the isoelectric point of θ-alumina was determined to be about 8.5. Comparison with literature data indicated that γ- and θ-alumina exhibit similar adsorption properties and that the amount of Pt deposited is controlled by pH and contact time for both systems. The adsorption appears to proceed initially as a physisorption process with relatively strong specific interaction or chemisorption taking over at longer contact times. Pt θ -alumina samples with 0.3 to 2.2 wt% Pt were prepared. Wet calcination at 570°C led to a decrease in the Cl content of the samples, while the Pt content was unaffected.