Surface properties of platinum catalysts based on various nanoporous matrices

Platinum species was located via incipient wetness impregnation with chloroplatinic acid in the mesoporous silicate and niobiosilicate of MCM-41 type, microporous DHY zeolite containing ∼20% of mesopores, and in Y zeolite mixed with the mesoporous NbMCM-41 material. A choice of the supports was determined by their various chemical composition and structure/texture parameters leading to the different metal–support interactions and various location of platinum. N2 adsorption/desorption measurements, XRD, 27Al MAS NMR, and TOF-SIMS techniques were applied for the characterisation of the prepared materials. A special focus was on the latter method, which allows a complex characterisation of metal surroundings (oxygen, chloride ions) and its dispersion, as well as the components of the support. The most important finding from this work is the migration of oxygen located in Nb surrounding toward platinum species, which causes the higher content of Pt-oxygen species in NbMCM-41 than in SiMCM-41 matrix, migration of oxygen from Pt to Al species in Pt/DHY, and migration of Pt from Pt/Y to NbMCM-41. The other important conclusions are the presence of Pt–Cl species strongly held especially in the systems containing niobium and the protection against Pt agglomeration by the incorporation of Nb element into the catalytic systems. All these features influence the catalytic activity of Pt-containing materials.