Florica Papa

Preparation, characterization and catalytic behavior of Pt-Cu nanoparticles in methane combustion

Abstract Fine and well dispersed Pt-Cu bimetallic nanoparticles stabilized by polyvinyl pyrrolidone (PVP) were synthesized by alkaline polyol method. The molar ratio of Pt to Cu was 1:1. Further, the Pt-Cu bimetallic nanoparticles were supported on alumina and their catalytic behavior in methane combustion was investigated. The as-prepared as well as the supported Pt-Cu nanoparticles were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fractal analysis and X-ray diffraction (XRD). The dependence of methane combustion on the morphology and surface composition of Pt-Cu nanoparticles was analyzed based on the experimental results.

Impact of particle size and metal–support interaction on denitration behavior of well-defined Pt–Cu nanoparticles

Well-dispersed Pt–Cu nanoparticles with two average sizes were synthesized: small (≈1.6 nm) and large (≈4.8 nm), respectively. The effects of size and support on the catalytic behavior of the nanoparticles for denitration reaction were analyzed. Both the unsupported and alumina-supported nanoparticles of smaller average size (1.6 nm) were very active, completely converting NO3− and NO2− (an intermediate reaction product) to N2 and NH4+. They were also more selective of N2 compared to the larger particles. The effects of particle size and alumina support on the denitration rate constants were analyzed in detail. The kinetic investigation indicates that the catalytic behavior is strongly related to the size of Pt–Cu nanoparticles as well as to the metal–support interaction. Generally, the larger nanoparticles proved to be less active, but on the other hand, they are less influenced by the support than the smaller ones. The metal–support interaction for bimetallic nanoparticles with smaller average size proved to be a key factor both for nitrate and nitrite reduction. Consideration of the reaction mechanism is made in light of the experimental results.

Fractal dimensions of lanthanum ferrite samples by adsorption isotherm method

Abstract Fractal dimensions of three different samples of lanthanum ferrite were computed using single adsorption method. The fractal Dubinin–Radushkevitch isotherm was used to fit directly the experimental nitrogen adsorption data. Avnir–Jaroniec method for fractal dimension determination was also used. Low and intermediate fractal dimensions were obtained according to BET specific surface areas.