Palladium–zinc catalysts on mesoporous titania prepared by colloid synthesis. II. Synthesis and characterization of PdZn/TiO₂ coating on inner surface of fused silica capillary

Nanoparticle-doped mesoporous titania coating was synthesized by incorporation of PdZn nanoparticles into TiO₂ sol followed by dip coating of the sol on inner surface of fused silica capillary. Monodispersed PdZn bimetallic colloidal particles with average particle diameters of approximately 2 nm have been prepared by an ethylene glycol reduction of ZnCl₂ and Pd(CH₃COO)₂ in the presence of polyvinylpyrrolidone. The textural properties, surface structure, chemical composition, and morphology of the samples were investigated by means of N₂ sorption measurements, TEM, and X-ray diffraction. PdZn/TiO₂ coating has been further analyzed by quantitative analysis of the SAXS data in combination with the density contrast method, providing direct structural-dispersion information about the active component and support. Calcination conditions suitable for surfactant removal have been optimized to obtain PdZn/TiO₂ coatings with required metal particle size and composition. The high dispersion and chemical composition of the nanoparticles embedded in mesoporous titania coating have been retained with no modification after thermal treatment in vacuum at 300 °C. Results suggest how porous structure of the PdZn coating may be fine-tuned to improve the accessibility of the pores to reactants. The control of the pore size in the range of 4.9–6.8 nm of the mesoporous titania was achieved by adding co-surfactants, such as n-butanol.