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Solid state reactions in the platinum–mercury system
Thermogravimetry and differential scanning calorimetry
Abstract
Thermogravimetry, Differential Scanning Calorimetry and other analytical techniques (Energy Dispersive X-ray Analysis; Scanning Electron Microscopy; Mapping Surface; X-ray Diffraction; Inductively Coupled Plasma Atomic Emission Spectroscopy and Cold Vapor Generation Atomic Absorption Spectroscopy) have been used to study the reaction of mercury with platinum foils. The results suggest that, when heated, the electrodeposited Hg film reacts with Pt to form intermetallic compounds each having a different stability, indicated by at least three mass loss steps. Intermetallic compounds such as PtHg4, PtHg and PtHg2 were characterized by XRD. These intermetallic compounds were the main products formed on the surface of the samples after partial removal of bulk mercury via thermal desorption. The Pt(Hg) solid solution formation caused great surface instability, attributed to the atomic size factor between Hg and Pt, facilitating the acid solution’s attack to the surface.
Introduction Platinum catalysts have usually been prepared by impregnating a platinum precursor on supports with exceptional thermal and mechanical stabilities to achieve a high platinum dispersion and long catalyst life [ 1
the catalysis, the functions of the metallic components and hydrogen during each isomerization step [ 10 ]. Highly chlorinated platinum-alumina catalysts can be used at low temperatures (120–180 °C). However, these catalysts are very sensitive
Some features of DTA in platinum crucibles in air related to the catalytic activity of platinum in many oxidation reactions have been considered. This property of platinum should be taken into account in the interpretation of the DTA curves.
composition necessary for kinetic analysis can be simultaneously monitored. The new technique has been applied to investigate the kinetics of methane combustion over platinum in the pressure range 4–16 bar [ 7 ], to identify the impact of large exhaust gas
opportunity to tailor both the size and the composition of the metal catalyst, which seems independent of the support [ 11 , 16 ]. Supported platinum catalysts have been most intensively used in catalytic reactions, such as hydrogenation of
Abstract
The thermal degradation of diammoniumhexachloroplatinate (NH4)2PtCl6 is used in technical scale for the production of the pure platinum metal [1] and for this reason of great interest. Our investigations have been focused on the influence of the different atmospheres (oxidizing, inert or reducing) used in the technical processes towards the degradation mechanism and the evolved volatile degradation products. The second main aspect of our investigations was the evolution of volatile platinum species. Regarding the different frequencies of platinum allergies related to the different technical processes, the evolution of volatile platinum species is of great importance, due to the supposed allergic potential of this substances [2–4].
Abstract
The reaction of platinum-methionines and platinum-selenomethionine complexes with ytterbium chloride was studied. The biodistribution of these organic platinum complexes labelled with169Yb was examined in animals bearing Ehrlich tumor. It was found that the retention of radioactivity from labelled monomethionin- and monoselenomethioninplatinum complexes in animals after 72 h was about 60% while the retention from dimethioninplatinum complex was about 6%.
Abstract
Standard enthalpies of formation of amorphous platinum hydrous oxide PtH2.76O3.89 (Adams' catalyst) and dehydrated oxide PtO2.52 at T=298.15 K were determined to be -519.61.0 and -101.3 5.2 kJ mol-1, respectively, by micro-combustion calorimetry. Standard enthalpy of formation of anhydrous PtO2 was estimated to be -80 kJ mol-1 based on the calorimetry. A meaningful linear relationship was found between the pseudo-atomization enthalpies of platinum oxides and the coordination number of oxygen surrounding platinum. This relationship indicates that the Pt-O bond dissociation energy is 246 kJ mol-1 at T=298.15 K which is surprisingly independent of both the coordination number and the valence of platinum atom. This may provide an energetic reason why platinum hydrous oxide is non-stoichiometric.
