Au or Pt Supported on Al Pillared Montmorillonite: Characterization and Catalytic Activity for CO Oxidation

To increases cation exchange capacity (CEC),Ca-montmorillonite is exchanged upon Ca₂₊ and Mg₂₊ to Na₊ and forms Na-montmorillonite.Al pillared montmorillonite(Al-PILCS) support is prepared by the intercalation of polymerization of aluminum hydroxyl ions(Al-agent) with Na-montmorillonite and then calcined.Platinum and gold is deposited on Al-PILCS by deposition-precipitation (DP) and impregnation.The characterization and catalytic activity of the samples are investigated by X-ray diffraction(XRD),N₂-sorption analysis,transmission electron microscopy (TEM),X-ray photoelectron spectroscopy (XPS) techniques,and CO oxidation reaction.Results of XRD and N₂-desorption/adsorption show that due to pillaring,Al-PILCS in microporous surface area and micropore volume increase distinctively.The influence of the preparation methods on the catalytic activity for CO oxidation is markedly large for Au/Al-PILCS and negligible for Pt/Al-PILCS catalysts.The DP method gives the most active catalysts for both Pt and Au.Pt catalysts prepared by DP show a much greater activity than Au catalysts.Different activities of Au/Al-PILCS and Pt/Al-PILCS may attribute to two reasons: the size of Au and Pt parties,and different reaction mechenismes.XPS techniques verified that the Au species of the samples is only metal Au⁰ over Au/Al-PILCS-IM and oxidation state Au ^δ+ and metal Au⁰ coexist over Au/Al-PILCS-DP.