Preparation of nano-sized palladium particles anchored onto Ln(2)O(3) grains with Ln = La, Nd, Sm, Eu or Gd

Nano-sized Pd-particles anchored onto Ln(2)O(3) particles with Ln = La, Nd, Sm, Eu or Gd have been prepared by reduction of the Ln(4)PdO(7) precursor materials in a flowing gas mixture of CO and an inert gas (He or Ar). The r eductions have been monitored by theromogravimetric (TG) and differential s canning calorimetric (DSC) measurements. The TG experiments show that the o nset temperatures of the reduction varies from 450 to 575 degrees C with th e lanthanoid used and Ln = Sm or Eu exhibit the lowest reduction temperatur es. The air re-oxidation of the reduced materials back to their oxidised fo rmed, e.g. Ln(4)PdO(7), has also been studied by TG and this reaction start s at 280-340 degrees C depending on the lanthanoid used; the re-oxidation p rocess occurs in two steps for all lanthanoids except Sm and Gd. The format ion of Ln(4)PdO(7) is observed to be very fast. The prepared and reduced ma terials have been characterised by their X-ray powder diffraction (XRPD) pa tterns. The DSC studies and XRPD patterns of quenched samples suggest that the reduction process occurs in at least two steps. The reduced materials h ave also been characterised by transmission electron microscopy (TEM/EDS) s tudies and a wet-chemistry method for selective dissolution of Ln(2)O(3) ha s been used to extract the formed Pd nano-particles. Line-broadening analys is of the XRPD pattern of extracted particles suggests that the Pd particle s are nanosized single crystals as the calculated particle size (20 nm) agr ees fairly well with corresponding data from the TEM studies (5-20 nm). Red uced Ln(4)PdO(7) materials have been shown to exhibit three way catalytic a ctivity for car exhaust clean-up (ie. simultaneous oxidation of CO and hydr ocarbons and reduction of NO) with T-50 values around 450 degrees C.