Point of Zero Charge of Oxides for Catalyst Preparation

Abstract

Determination of the point of zero charge (PZC) of supported oxide is an essential step for catalyst preparation, especially via the wet impregnation method, because the adsorption of complex metallic ions on oxide surface is due to the electrostatic force at the interface-oxide solution. Knowing the PZC of oxide can be useful for the catalyst preparation in terms of the suitable condition (ie, type of metal complex ions and pH of solution)

The mass titration technique was selected in this study to estrmate the PZC of both single and composite oxides. The pH_PZC of single oxides found are corresponded with the value recorded by other investigators using different methods. For single oxides, Al₂O₃ MgO, SiO₂ (Sigma) and SiO₂ (Oriental), their  PZCs are found to be 9.5, 11.5, 4.7 and 6.7, respectively. But the pH_PZC of mixed oxide of 6% MgO/ Al₂O₃ approximately equals to 11.0 which is located in between PZC of pure Al₂O₃ and of MgO. This is an important information for the improvement the efficiency of wet impregnation method since the shift of PZC can be obtained.