Volume 224, Issue 05 -

The formation of condensed particles in atmospheric ethylene-oxygen and acetylene-air premixed flames catalyzed by the vapours of Fe(CO) 5 and Mo(CO) 6 was studied in the wide range of C/O ratio. Laser scattering and extinction measurements were carried out in a wide frame of flame conditions. The structure and the morphology of formed particles were analyzed using electron microscope. Different formation of the particles takes place due to the fuels and also to the catalyst. In the C 2 H 2 /air flame catalyzed with Mo(CO) 6 , particle formation starts at about threshold of soot formation (C/O ~ 0.6), while in the flames doped with Fe(CO) 5 , particle formation starts already in the lean range of both premixed flames investigated here.

Systematic determination of the surface tension and surface excess values of aquo-organic mixtures (methanol + water, ethanol + water, isoprapanol + water, tertiary butanol + water and ethylene glycol + water) were made. Attempts were made to interpret the surface tension values of aquo-alcoholic mixtures in terms of structure of water and its interactions with alcohols, surface excess and excess surface tension values. Correlation of the structural properties of the solvent mixtures with surface excess and other related macroscopic properties were attempted.

We report on the desorption kinetics of adsorbates from metal surfaces in the presence of exoergic - processes, either atom recombination or non-dissociative adsorption. The modeling takes into account the dissipation of the adatom energy to both the solid and the adlayer and permits one to investigate the effect of these processes on the desorption rate. The model kinetics, which is solved analytically for two recombination channels under non steady state conditions, shows that the desorption rate is ruled by the ratio between the rate constant for recombination and for energy loss to the solid. The behavior of the vibrational distribution function of the adatoms on this control parameter is analyzed and compared with Boltzmann equilibrium distributions. Rate coefficients for energy disposal to a metal surface, evaluated for a relaxation process involving electron-hole pair excitation, are shown to be linked to the electron density, which than becomes a control parameter of reaction rates at metal surfaces.

The theoretical model presented in the previous paper predicts the possibility of vibrational excitation of the adlayer in exoergic process at metal surfaces to an extent determined by the interplay of reaction rates and energy dissipation into the metal. In the present paper this model will be employed for studying the following systems: a)The abstraction of D s adspecies by H gas and the accompanying H-atom recombination and b) the adsorption-stimulated desorption of CO s in the presence of adsorbing CO gas . Proper reduction of literature data provides the evidence for the existence of vibrational excitation of the H-Me and of the CO-Me adlayers, witnessed by desorption rates that are orders of magnitude larger than those expected for systems in Boltzmann equilibrium. Application of the model to D s +H gas relates the vibrational excitation of the adlayer and the corresponding non-Boltzmann desorption rates to the parameter Z/K and to the flux of adsorbing species. Rate coefficients K for vibrational relaxation of the H-Me bond are in the range 10 13 -10 12 s −1 and decrease with increasing surface coverage σ . The analysis of CO s desorption in the presence of adsorbing CO gas confirms the dependence of desorption rates on Z/K , the coverage dependence of the rate coefficients K for energy relaxation of the CO-Me bond and brings out the predicted influence of gas pressure on the over- population of the vibrational levels of adsorbed CO. The decrease of K observed in both systems is discussed in terms of energy relaxation processes involving electron-hole pair excitation at the metal surface and it should be linked to the decrease of the surface electron density caused by the adsorbates.

Kinetics of heterogeneous catalysed esterification of propionic acid with n-amyl alcohol was studied with a microporous cation-exchange resin catalyst, Dowex 50Wx4, in a stirred batch reactor to synthesise amyl propionate. Effects of various parameters such as speed of agitation, catalyst loading, and reaction temperature on reaction rate were investigated. The equilibrium conversion of propionic acid increased with in catalyst loading and reaction temperature. Stirrer speed had virtually no effect on the reaction rate under the experimental conditions. The apparent activation energy was found to be 43.167 kJmol −1 for the formation of amyl propionate and the equilibrium constant, which is independent of temperature ranging from 318 to 348 K, was found to be 4.05. It was also observed that the initial reaction rate decreased with water concentrations and increased with that of acid and increased with that of alcohol linearly. The reaction was found to occur between an adsorbed acid molecule and a molecule of alcohol in the bulk and it was concluded that the reaction mechanism can be represented by Eley-Rideal model.

We celebrate the 100 th anniversary of the construction of the first glass electrode, by F. Haber and Z. Klemensiewicz. This electrode was firstly described in the journal Zeitschrift fur physikalische Chemie in 1909. In our paper we present the way how this invention was created.